Widely targeted metabolomics-based analysis of the impact of L. plantarum and L. paracasei fermentation on rosa roxburghii Tratt juice

Rosa roxburghii Tratt fruits (RRT) exhibit extremely high nutritional and medicinal properties due to its unique phytochemical composition. Probiotic fermentation is a common method of processing fruits. Variations in the non-volatile metabolites and bioactivities of RRT juice caused by different lactobacilli are not well understood. Therefore, we aimed to profile the non-volatile components and investigate the impact of L. plantarum fermentation (LP) and L. paracasei fermentation (LC) on RRT juice (the control, CG). There were both similarities and differences in the effects of LP and LC on RRT juice. Both of the two strains significantly increased the content of total phenolic, total flavonoid, and some bioactive compounds such as 2-hydroxyisocaproic acid, hydroxytyrosol and indole-3-lactic acid in RRT juice. Interestingly, compared with L. paracasei, L. plantarum showed better ability to increase the content of total phenolic and these valuable compounds, as well as certain bioactivities. The antioxidant capacity and α-glucosidase inhibitory activity of RRT juice were notably enhanced after the fermentations, whereas its cholesterol esterase inhibitory activity was reduced significantly. Moreover, a total of 1466 metabolites were identified in the unfermented and fermented RRT juices. There were 278, 251 and 134 differential metabolites in LP vs CG, LC vs CG, LC vs LP, respectively, most of which were upregulated. The key differential metabolites were classified into amino acids and their derivatives, organic acids, nucleotides and their analogues, phenolic acids and alkaloids, which can serve as potential markers for authentication and discrimination between the unfermented and lactobacilli fermented RRT juice samples. The KEGG enrichment analysis uncovered that metabolic pathways, purine metabolism, nucleotide metabolism and ABC transporters contributed mainly to the formation of unique composition of fermented RRT juice. These results provide good coverage of the metabolome of RRT juice in both unfermented and fermented forms and also provide a reference for future research on the processing of RRT or other fruits.

Virulence of Novel Ralstonia pseudosolanacearum (Phylotype I) Strains from Rose, Blueberry, and Mandevilla on Seed Potato

Potato (Solanum tuberosum L.) ranks fourth among the most important staple food in the world. Ralstonia solanacearum (phylotype [phy] IIB, sequevar [seq] 1 and 2), also known as R3B2, the causal agent of brown rot disease on potato, is extremely damaging, causing great economical losses to potato in temperate regions. It is thought that members of Ralstonia pseudosolanacearum (phy I) are not pathogenic at low temperatures and are usually found in warmer climates. R. pseudosolanacearum strain PD 7123 (seq 33) isolated from roses in the Netherlands, strain P824 (seq 13) isolated from blueberry, and strain P781 (seq 14) from mandevilla in Florida are phylogenetically closely related and could share the same host. The virulence and ability of these novel strains to multiply latently in potato in temperate regions is unknown. The objective of this work was to assess the virulence and presence of latent infections of the mentioned R. pseudosolanacearum strains on three commercial seed potato cultivars under warmer (28°C) and temperate (20°C) temperatures. At 28°C, all three R. pseudosolanacearum strains caused severe symptoms on all potato cultivars. Overall disease severity on potato was lower at 20°C than 28°C, but major differences in virulence of the three strains were observed at 42 days postinoculation (dpi) among potato cultivars. All asymptomatic potato plants and most of their daughter tubers had latent infections at 20°C. Altogether, these results show that the phy I strains from rose, blueberry, and mandevilla may pose a threat to potato production in temperate climates and the worldwide movement of seed potatoes.[Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Characterization of wall-associated kinase/wall-associated kinase-like (WAK/WAKL) family in rose (Rosa chinensis) reveals the role of RcWAK4 in Botrytis resistance

BACKGROUND

Wall-associated kinase (WAK)/WAK-like (WAKL) is one of the subfamily of receptor like kinases (RLK). Although previous studies reported that WAK/WAKL played an important role in plant cell elongation, response to biotic and abiotic stresses, there are no systematic studies on RcWAK/RcWAKL in rose.

RESULTS

In this study, we identified a total of 68 RcWAK/RcWAKL gene family members within rose (Rosa chinensis) genome. The RcWAKs contained the extracellular galacturonan-binding domain and calcium-binding epidermal growth factor (EGF)-like domain, as well as an intracellular kinase domains. The RcWAKLs are missing either calcium-binding EGF-like domain or the galacturonan-binding domain in their extracellular region. The phylogenetic analysis showed the RcWAK/RcWAKL gene family has been divided into five groups, and these RcWAK/RcWAKL genes were unevenly distributed on the 7 chromosomes of rose. 12 of RcWAK/RcWAKL genes were significantly up-regulated by Botrytis cinerea-inoculated rose petals, where RcWAK4 was the most strongly expressed. Virus induced gene silencing of RcWAK4 increased the rose petal sensitivity to B. cinerea. The results indicated RcWAK4 is involved in the resistance of rose petal against B. cinerea.

CONCLUSION

Our study provides useful information to further investigate the function of the RcWAK/RcWAKL gene family and breeding research for resistance to B. cinerea in rose.

Analysis of allelic variants of RhMLO genes in rose and functional studies on susceptibility to powdery mildew related to clade V homologs

Rose has 19 MLO genes. Of these, RhMLO1 and RhMLO2 were shown to be required for powdery mildew infection, which suggests their potential as susceptibility targets towards disease resistance. Powdery mildew, caused by Podosphaera pannosa, is one of the most serious and widespread fungal diseases for roses, especially in greenhouse-grown cut roses. It has been shown that certain MLO genes are involved in powdery mildew susceptibility and that loss of function in these genes in various crops leads to broad-spectrum, long-lasting resistance against this fungal disease. For this reason, these MLO genes are called susceptibility genes. We carried out a genome-wide identification of the MLO gene family in the Rosa chinensis genome, and screened for allelic variants among 22 accessions from seven different Rosa species using re-sequencing and transcriptome data. We identified 19 MLO genes in rose, of which four are candidate genes for functional homologs in clade V, which is the clade containing all dicot MLO susceptibility genes. We detected a total of 198 different allelic variants in the set of Rosa species and accessions, corresponding to 5-15 different alleles for each of the genes. Some diploid Rosa species shared alleles with tetraploid rose cultivars, consistent with the notion that diploid species have contributed to the formation of tetraploid roses. Among the four RhMLO genes in clade V, we demonstrated using expression study, virus-induced gene silencing as well as transient RNAi silencing that two of them, RhMLO1 and RhMLO2, are required for infection by P. pannosa and suggest their potential as susceptibility targets for powdery mildew resistance breeding in rose.

RcTGA1 and glucosinolate biosynthesis pathway involvement in the defence of rose against the necrotrophic fungus Botrytis cinerea

BACKGROUND

Rose is an important economic crop in horticulture. However, its field growth and postharvest quality are negatively affected by grey mould disease caused by Botrytis c. However, it is unclear how rose plants defend themselves against this fungal pathogen. Here, we used transcriptomic, metabolomic and VIGS analyses to explore the mechanism of resistance to Botrytis c.

RESULT

In this study, a protein activity analysis revealed a significant increase in defence enzyme activities in infected plants. RNA-Seq of plants infected for 0 h, 36 h, 60 h and 72 h produced a total of 54 GB of clean reads. Among these reads, 3990, 5995 and 8683 differentially expressed genes (DEGs) were found in CK vs. T36, CK vs. T60 and CK vs. T72, respectively. Gene annotation and cluster analysis of the DEGs revealed a variety of defence responses to Botrytis c. infection, including resistance (R) proteins, MAPK cascade reactions, plant hormone signal transduction pathways, plant-pathogen interaction pathways, Ca²⁺ and disease resistance-related genes. qPCR verification showed the reliability of the transcriptome data. The PTRV2-RcTGA1-infected plant material showed improved susceptibility of rose to Botrytis c. A total of 635 metabolites were detected in all samples, which could be divided into 29 groups. Metabonomic data showed that a total of 59, 78 and 74 DEMs were obtained for T36, T60 and T72 (T36: Botrytis c. inoculated rose flowers at 36 h; T60: Botrytis c. inoculated rose flowers at 60 h; T72: Botrytis c. inoculated rose flowers at 72 h) compared to CK, respectively. A variety of secondary metabolites are related to biological disease resistance, including tannins, amino acids and derivatives, and alkaloids, among others; they were significantly increased and enriched in phenylpropanoid biosynthesis, glucosinolates and other disease resistance pathways. This study provides a theoretical basis for breeding new cultivars that are resistant to Botrytis c.

CONCLUSION

Fifty-four GB of clean reads were generated through RNA-Seq. R proteins, ROS signalling, Ca²⁺ signalling, MAPK signalling, and SA signalling were activated in the Old Blush response to Botrytis c. RcTGA1 positively regulates rose resistance to Botrytis c. A total of 635 metabolites were detected in all samples. DEMs were enriched in phenylpropanoid biosynthesis, glucosinolates and other disease resistance pathways.

Characterization of black spot resistance in diploid roses with QTL detection, meta-analysis and candidate-gene identification

Two environmentally stable QTLs linked to black spot disease resistance in the Rosa wichurana genetic background were detected, in different connected populations, on linkage groups 3 and 5. Co-localization between R-genes and defense response genes was revealed via meta-analysis. The widespread rose black spot disease (BSD) caused by the hemibiotrophic fungus Diplocarpon rosae Wolf. is efficiently controlled with fungicides. However, in the actual context of reducing agrochemical use, the demand for rose bushes with higher levels of resistance has increased. Qualitative resistance conferred by major genes (Rdr genes) has been widely studied but quantitative resistance to BSD requires further investigation. In this study, segregating populations connected through the BSD resistant Rosa wichurana male parent were phenotyped for disease resistance over several years and locations. A pseudo-testcross approach was used, resulting in six parental maps across three populations. A total of 45 individual QTLs with significant effect on BSD resistance were mapped on the male maps (on linkage groups (LG) B3, B4, B5 and B6), and 12 on the female maps (on LG A1, A2, A3, A4 and A5). Two major regions linked to BSD resistance were identified on LG B3 and B5 of the male maps and were integrated into a consensus map built from all three of the male maps. A meta-analysis was used to narrow down the confidence intervals of individual QTLs from three populations by generating meta-QTLs. Two 'hot spots' or meta-QTLs were found per LG, enabling reduction of the confidence interval to 10.42 cM for B3 and 11.47 cM for B5. An expert annotation of NBS-LRR encoding genes of the genome assembly of Hibrand et al. was performed and used to explore potential co-localization with R-genes. Co-localization with defense response genes was also investigated.

Global analysis of the AP2/ERF gene family in rose (Rosa chinensis) genome unveils the role of RcERF099 in Botrytis resistance

BACKGROUND

The AP2/ERFs belong to a large family of transcription factors in plants. The AP2/ERF gene family has been identified as a key player involved in both biotic and abiotic stress responses in plants, however, no comprehensive study has yet been carried out on the AP2/ERF gene family in rose (Rosa sp.), the most important ornamental crop worldwide.

RESULTS

The present study comprises a genome-wide analysis of the AP2/ERF family genes (RcERFs) in the rose, involving their identification, gene structure, phylogenetic relationship, chromosome localization, collinearity analysis, as well as their expression patterns. Throughout the phylogenetic analysis, a total of 131 AP2/ERF genes in the rose genome were divided into 5 subgroups. The RcERFs are distributed over all the seven chromosomes of the rose, and genome duplication may have played a key role in their duplication. Furthermore, Ka/Ks analysis indicated that the duplicated RcERF genes often undergo purification selection with limited functional differentiation. Gene expression analysis revealed that 23 RcERFs were induced by infection of the necrotrophic fungal pathogen Botrytis cinerea. Presumably, these RcERFs are candidate genes which can react to the rose's resistance against Botrytis cinerea infection. By using virus-induced gene silencing, we confirmed that RcERF099 is an important regulator involved in the B.cinerea resistance in the rose petal.

CONCLUSION

Overall, our results conclude the necessity for further study of the AP2/ERF gene family in rose, and promote their potential application in improving the rose when subjected to biological stress.

RcMYB84 and RcMYB123 mediate jasmonate-induced defense responses against Botrytis cinerea in rose (Rosa chinensis)

Jasmonates (JAs) are important for pathogen resistance in many plants, but the role of these phytohormones in fungal pathogen resistance in rose is unclear. Here, we determined that exogenous application of methyl jasmonate increased resistance to the important fungal pathogen Botrytis cinerea in Rosa chinensis 'Old blush', whereas silencing the JA biosynthetic pathway gene Allene Oxide Synthase (AOS) and JA co-receptor gene CORONATINE INSENSITIVE 1 (COI1) suppressed this response. Transcriptome profiling identified various MYB transcription factor genes that responded to both JA and B. cinerea treatment. Silencing Ri-RcMYB84/Ri-RcMYB123 increased the susceptibility of rose plants to B. cinerea and inhibited the protective effects of JA treatment, confirming the crucial roles of these genes in JA-induced responses to B. cinerea. JAZ1, a key repressor of JA signaling, directly interacts with RcMYB84 and RcMYB123 to deplete their free pools. The JAZ1-RcMYB84 complex binds to the RcMYB123 promoter via the CAACTG motifs to block its transcription. Upon JA treatment, the expression of RcMYB123 is de-repressed, and free forms of RcMYB84 and RcMYB123 are released due to JAZ1 degradation, thereby activating the defense responses of plants to B. cinerea. These findings shed light on the molecular mechanisms underlying JA-induced pathogen resistance in roses.

Mapping the black spot resistance locus Rdr3 in the shrub rose 'George Vancouver' allows for the development of improved diagnostic markers for DNA-informed breeding

Rdr3 is a novel resistance gene of black spot in roses that maps to a chromosome 6 homolog. A new DNA test was developed and can be used to pyramid black spot resistance in roses. Diplocarpon rosae, the cause of rose black spot, is one of the most devastating foliar pathogens of cultivated roses (Rosa spp.). The primary method of disease control is fungicides, and they are viewed unfavorably by home gardeners due to potential environmental and health impacts. Planting rose cultivars with genetic resistance to black spot can reduce many of the fungicide applications needed in an integrated pest management system. To date, four resistance genes have been identified in roses (Rdr1, Rdr2, Rdr3, and Rdr4). Rdr3 was never mapped and is thought to be unique from Rdr1 and Rdr2. It is unknown whether it is an allele of Rdr4. To assess the novelty of Rdr3, a mapping population was created by crossing the Rdr3 containing cultivar George Vancouver with the susceptible cultivar Morden Blush. The mapping population was genotyped with the WagRhSNP 68 K Axiom array and mapped using the 'polymapR' package. Rdr3 was mapped to a chromosome 6 homolog confirming it is different from Rdr1 and Rdr2, found on chromosome 1, and from Rdr4, found on chromosome 5. The mapping information was used in conjunction with the Rosa chinensis genome assembly to develop new tightly linked SSRs for marker-assisted breeding. Three markers were able to predict the presence of Rdr3 in a 63-cultivar validation set. Additionally, 12 cultivars appear to have resistance genes other than Rdr3. The improved diagnostic markers will be a great asset to the rose-breeding community toward developing new black spot-resistant cultivars.

Assessment of endophytic bacterial diversity in rose by high-throughput sequencing analysis

The endophytic bacterial diversity of rose was analyzed by high-throughput sequencing of 16S rDNA and functional prediction of the bacterial community. The number of bacterial sequence reads obtained from 18 rose samples ranged from 63,951 to 114,833, and reads were allocated to 1982 OTUs based on sequences of the V3-V4 region. The highest Shannon Index was found in Luogang rose (1.93), while the lowest was found in Grasse rose (0.35). The bacterial sequence reads were grouped into three different phyla: Firmicutes, Proteobacteria, and Actinobacteria. At the genus level, Bacillus and Staphylococcus had the highest abundance across all 18 samples; Bacillus was particularly abundant in Daguo rose (99.09%), Rosa damascena (99.65%), and Fenghua rose (99.58%). Unclassified OTUs were also found in all samples. PICRUSt gene prediction revealed that each endophyte sample contained multiple KEGG functional modules related to human metabolism and health. A high abundance of functional genes were involved in (1) Amino Acid Metabolism, (2) Carbohydrate Metabolism, (3) Cellular Processes and Signaling, (4) Energy Metabolism, and (5) Membrane Transport, indicating that the endophytic community comprised a wide variety of microorganisms and genes that could be used for further studies. The rose endophytic bacterial community is rich in diversity; community composition varies among roses and contains functional information related to human health.

Identification of a polymorphism within the Rosa multiflora muRdr1A gene linked to resistance to multiple races of Diplocarpon rosae W. in tetraploid garden roses (Rosa × hybrida)

A QTL for resistance to several races of black spot co-located with the known Rrd1 locus in Rosa. A polymorphism in muRdr1A linked to black spot resistance was identified and molecular markers were designed. Black spot, caused by Diplocarpon rosae, is one of the most serious foliar diseases of landscape roses that reduces the marketability and weakens the plants against winter survival. Genetic resistance to black spot (BS) exists and race-specific resistance is a good target to implement marker-assisted selection. High-density single nucleotide polymorphism-based genetic maps were created for the female parent of a tetraploid cross between 'CA60' and 'Singing in the Rain' using genotyping-by-sequencing following a two-way pseudo-testcross strategy. The female linkage map was generated based on 227 individuals and included 31 linkage groups, 1055 markers, with a length of 1980 cM. Race-specific resistance to four D. rosae races (5, 7, 10, 14) was evaluated using a detached leaf assay. BS resistance was also evaluated under natural infection in the field. Resistance to races 5, 10 and 14 of D. rosae and field resistance co-located on chromosome 1. A unique sequence of 32 bp in exon 4 of the muRdr1A gene was identified in 'CA60' that co-segregates with D. rosae resistance. Two diagnostic markers, a presence/absence marker and an INDEL marker, specific to this sequence were designed and validated in the mapping population and a backcross population derived from 'CA60.' Resistance to D. rosae race 7 mapped to a different location on chromosome 1.

Genome-wide characterization of the rose (Rosa chinensis) WRKY family and role of RcWRKY41 in gray mold resistance

BACKGROUND

The WRKYs are a major family of plant transcription factors that play roles in the responses to biotic and abiotic stresses; however, a comprehensive study of the WRKY family in roses (Rosa sp.) has not previously been performed.

RESULTS

In the present study, we performed a genome-wide analysis of the WRKY genes in the rose (Rosa chinensis), including their phylogenetic relationships, gene structure, chromosomal locations, and collinearity. Using a phylogenetic analysis, we divided the 56 RcWRKY genes into three subgroups. The RcWRKYs were unevenly distributed across all seven rose chromosomes, and a study of their collinearity suggested that genome duplication may have played a major role in RcWRKY gene duplication. A Ka/Ks analysis indicated that they mainly underwent purifying selection. Botrytis cinerea infection induced the expression of 19 RcWRKYs, most of which had undergone gene duplication during evolution. These RcWRKYs may regulate rose resistance against B. cinerea. Based on our phylogenetic and expression analyses, RcWRKY41 was identified as a candidate regulatory gene in the response to B. cinerea infection, which was confirmed using virus-induced gene silencing.

CONCLUSIONS

This study provides useful information to facilitate the further study of the function of the rose WRKY gene family.

Two Novel Genomospecies in the Agrobacterium tumefaciens Species Complex Associated with Rose Crown Gall

In this study, we explored the pathogenicity and phylogenetic position of Agrobacterium spp. strains isolated from crown gall tissues on annual, perennial, and ornamental plants in Iran. Of the 43 strains studied, 10 strains were identified as Allorhizobium vitis (formerly Agrobacterium vitis) using the species-specific primer pair PGF/PGR. Thirty-three remaining strains were studied using multilocus sequence analysis of four housekeeping genes (i.e., atpD, gyrB, recA, and rpoB), from which seven strains were identified as A. larrymoorei and one strain was identified as A. rubi (Rer); the remaining 25 strains were scattered within the A. tumefaciens species complex. Two strains were identified as genomospecies 1 (G1), seven strains were identified as A. radiobacter (G4), seven strains were identified as A. deltaense (G7), two strains were identified as A. nepotum (G14), and one strain was identified as "A. viscosum" (G15). The strains Rnr, Rnw, and Rew as well as the two strains OT33 and R13 all isolated from rose and the strain Ap1 isolated from apple were clustered in three atypical clades within the A. tumefaciens species complex. All but eight strains (i.e., Nec10, Ph38, Ph49, fic9, Fic72, R13, OT33, and Ap1) were pathogenic on tomato and sunflower seedlings in greenhouse conditions, whereas all but three strains (i.e., fic9, Fic72, and OT33) showed tumorigenicity on carrot root discs. The phylogenetic analysis and nucleotide diversity statistics suggested the existence of two novel genomospecies within the A. tumefaciens species complex, which we named "G19" and "G20." Hence, we propose the strains Rew, Rnw, and Rnr as the members of "G19" and the strains R13 and OT33 as the members of G20, whereas the phylogenetic status of the atypical strain Ap1 remains undetermined.

Characterization of Botrytis cinerea From Commercial Cut Flower Roses

Botrytis cinerea Pers. infects cut flower roses (Rosa × hybrida L.) during greenhouse production and gray mold symptoms are often expressed in the postharvest environment, resulting in significant economic losses. Disease management is based on cultural practices and preventative chemical treatments; however, gray mold outbreaks continue to occur. Rose tissues from six commercial shipments from two greenhouses in Colombia were evaluated to determine the Botrytis species composition as well as identify other pathogens present, gray mold incidence and severity, and fungicide resistance profiles. Botrytis isolates (49 total) were grouped into six morphological phenotypes, and all were identified to be B. cinerea sensu stricto. Disease incidence was higher in the petals than in the stem, stamen, ovary, sepal, or leaf tissues. Other fungi were isolated infrequently and included Alternaria alternata, Cladosporium cladosporioides, Epicoccum nigrum, Penicillium citrinum, Aspergillus brasiliensis, and Diplodia sp. Fungicide resistance profiles were determined using previously established discriminatory doses. Isolates resistant to thiophanate-methyl, iprodione, boscalid, and cyprodinil were found frequently in all shipments and in both greenhouses. The frequency of resistance to penthiopyrad, fenhexamid, fluopyram, isofetamid, and fludioxonil varied between shipments and greenhouses. No resistance to pydiflumetofen was observed at the discriminatory doses tested. Isolates with resistance to multiple chemical classes were commonly found. These results indicate that fungicide resistance management practices may improve preharvest and postharvest gray mold control of cut flower roses.

Engineered nanomaterials inhibit Podosphaera pannosa infection on rose leaves by regulating phytohormones

In the present study, we investigated the antifungal effects of engineered nanomaterials (ENMs) against Podosphaera pannosa (P. pannosa), a fungal pathogen that causes powdery mildew on plants in the rose family. Four commercial ENMs, including multi-wall carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), copper oxide (CuO) nanoparticles (NPs) and titanium dioxide (TiO₂) NPs, were used to prepare 50 or 200 mg/L NP suspensions in deionized water. Rose leaves in water-agar plates were sprayed by different ENM suspensions mixed with P. pannosa conidia. After a 19-day standard infection test, the growth of P. pannosa on rose leaves was evaluated. All four ENMs inhibited infection by P. pannosa at the concentration 200 mg/L, whereas only CuO NPs decreased fungal growth at 50 mg/L. The phytohormone content of the leaves was measured across all treatments to investigate potential ENMs antifungal mechanisms. The results suggest that ENMs increased plant resistance to fungal infection by altering the content of endogenous hormones, particularly zeatin riboside (ZR). Our study demonstrates that ENMs exhibited distinctly antifungal effects against P. pannosa on roses, and could be utilized as a novel plant protection strategy after a comprehensive assessment of potential environmental risk.

Phylogenetic Assignment of Ralstonia pseudosolanacearum (Ralstonia solanacearum Phylotype I) Isolated from Rosa spp

During the last two years, greenhouse cultivation of rose (Rosa spp.) in the Netherlands has been challenged by an uncommon bacterial disease. Affected plants suffered from chlorosis, stunting, wilting, and necrosis. The bacterial isolates obtained from the different Rosa spp. cultivars were all identified as phylotype I, sequevar 33 from the 'Ralstonia solanacearum species complex' (RSSC), actually reclassified as Ralstonia pseudosolanacearum. The work in this paper considers the genetic diversity and the phylogenetic position of 129 R. pseudosolanacearum isolates from the outbreak. This was assessed by AFLP based on four different primer combinations and MLP using partial sequences of the egl, mutS, and fliC genes. The AFLP revealed identical profiles for all the isolates, irrespective of their association with Rosa sp. propagating material, Rosa spp. plants for cut flowers, or water used in the different greenhouse cultivations. These AFLP profiles were unique and diverged from profiles of all other reference isolates in the RSSC included. Furthermore, MLP on egl, fliC, and mutS gene sequences clearly demonstrated that all R. pseudosolanacearum isolates clustered in phylotype I, as a distinct monophyletic group. Interestingly, this monophyletic group also included phylotype I strain Rs-09-161 from eggplant (Solanum melongena), isolated in 2009 in India. AFLP and MLP were both efficient in revealing the genetic divergence from the RSSC isolates included. The phylogenetic tree constructed from the AFLP profiles was, in general, in agreement with the one obtained from MLP. Both phylogenetic trees displayed a similar clustering, supported by high posterior probabilities. Both methodologies clearly demonstrated that the R. pseudosolanacearum isolates from Rosa spp. grouped in a monophyletic group inside phylotype I, with a particular correspondence to a strain present in India, as revealed in MLP.

Downy Mildew: A Serious Disease Threat to Rose Health Worldwide

Peronospora sparsa is a downy mildew-causing oomycete that can infect roses, blackberries, and other members of the rose family. During the last 70 years, this disease has become a serious problem for rose growers in the U.S. and worldwide. While much is known about the disease and its treatment, including significant research on molecular identification methods, as well as environmental conditions conducive to disease and the fungicides used to prevent it, significant knowledge gaps remain in our basic comprehension of the pathogen's biology. For example, the degree of genetic relatedness of pathogen isolates collected from rose, caneberries, and cherry laurel has never been examined, and the natural movement of genotypes from host to host is not known. Further work could be done to determine the differences in pathogen population structure over time (using herbarium specimens and fresh collections) or differences in pathogen population structure and pathogen environmental adaptation for specimens from different geographic regions. The oospore stage of the organism is poorly understood, both as to how it forms and whether it serves as an overwintering structure in nurseries and landscapes. In production greenhouses, the detection of the pathogen using infrared thermographic imaging and possible inhibition by ultraviolet light needs to be explored. Further work needs to be done on breeding using wild roses as new sources for resistance and using new methods such as marker assisted selection and RNAi technologies. As roses are one of the most economically important ornamental crops worldwide, a proper understanding of the disease cycle could allow for better use of cultural and chemical controls to manage rose downy mildew in landscapes and in greenhouse and nursery production areas.

The TNL gene Rdr1 confers broad-spectrum resistance to Diplocarpon rosae

Black spot disease, which is caused by the ascomycete Diplocarpon rosae, is the most severe disease in field-grown roses in temperate regions and has been distributed worldwide, probably together with commercial cultivars. Here, we present data indicating that muRdr1A is the active Rdr1 gene, a single-dominant TIR-NBS-LRR (Toll/interleukin-1 receptor-nucleotide binding site-leucine rich repeat) (TNL)-type resistance gene against black spot disease, which acts against a broad range of pathogenic isolates independent of the genetic background of the host genotype. Molecular analyses revealed that, compared with the original donor genotype, the multiple integrations that are found in the primary transgenic clone segregate into different integration patterns in its sexual progeny and do not show any sign of overexpression. Rdr1 provides resistance to 13 different single-spore isolates belonging to six different races and broad field mixtures of conidia; thus far, Rdr1 is only overcome by two races. The expression of muRdr1A, the active Rdr1 gene, leads to interaction patterns that are identical in the transgenic clones and the non-transgenic original donor genotype. This finding indicates that the interacting avirulence (Avr) factor on the pathogen side must be widespread among the pathogen populations and may have a central function in the rose-black spot interaction. Therefore, the Rdr1 gene, pyramided with only a few other R genes by sexual crosses, might be useful for breeding roses that are resistant to black spot because the spread of new pathogenic races of the fungus appears to be slow.

Sphingobium soli sp. nov. isolated from rhizosphere soil of a rose

Strain THG-SQA7(T), a Gram-negative, strictly aerobic, non-motile, rod-shaped bacterium was isolated from rhizosphere soil of a rose in PR China. Strain THG-SQA7(T) is closely related to the members of the genus Sphingobium, showing the highest 16S rRNA gene sequence similarities with Sphingobium lactosutens KACC 18100(T) (98.2%) and Sphingobium abikonense KCTC 2864(T) (98.1%). The DNA-DNA relatedness between strain THG-SQA7(T) and S. lactosutens KACC 18100(T) and S. abikonense KCTC 2864(T) was 26.2 ± 0.9 and 28.3 ± 1.2%, respectively. Chemotaxonomic data showed that strain THG-SQA7(T) possesses ubiquinone Q-10 as the predominant respiratory quinone, and C(18:1)ω7c, C(16:0), summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c) and C(14:0) 2OH as the major fatty acids. The major polar lipids were found to be phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, sphingoglycolipid, diphosphatidylglycerol and phosphatidyldimethylethanolamine. Based on these results, together with phenotypic characterization, a novel species, Sphingobium soli sp. nov. is proposed.with the type strain is THG-SQA7(T) (=CCTCC AB 2015125(T) = KCTC 42607(T)).

Root-associated fungi of Rosa rugosa grown on the frontal dunes of the Baltic Sea Coast in Lithuania

The aim of the present study was to assess fungal communities associated with fine living roots of Rosa rugosa Thunb grown on the frontal dunes of Curonian Spit at the Baltic Sea coast in Lithuania. The roots of R. rugosa were sampled at five sites (Nida, Preila, Pervalka, Juodkrante and Smiltyne) situated at a distance ca. 5-15 km from each other. Direct amplification, cloning and sequencing of fungal ITS rRNA from the fine roots resulted in 134 high-quality sequences, representing 31 fungal taxa among which saprotrophs and endophytes Mycena sp. (14.2 %), Tumularia sp. (14.2 %), Penicillium spinulosum (11.9 %) and Cadophora malorum (9.0 %) were most common. Arbuscular mycorrhizal fungi including Entrophospora baltica (0.7 %) and Rhizophagus irregularis (0.7 %) and potentially root pathogenic fungi--Ceratobasidium sp. (4.5 %), Fusarium oxysporum (3.0 %), Fusarium culmorum (0.7 %) and Ilyonectria crassa (0.7 %)--were also detected at low proportions. In conclusion, the results demonstrated that the fine roots of R. rugosa are inhabited by various groups of fungi. Although saprotrophs and endophytes were dominant, the detection of arbuscular mycorrhizal fungi indicated that these may be important for mineral nutrition of R. rugosa established on dry and poor fertility coastal dunes.

Martelella endophytica sp. nov., an antifungal bacterium associated with a halophyte

A Gram-staining-negative, non-spore-forming endophytic bacterium, designated strain YC6887(T), was isolated from a root sample of a halophyte, Rosa rugosa, collected from a tidal flat area of Namhae Island, located at the southern end of Korea. Strain YC6887(T) was found to exhibit inhibitory activity against oomycete plant pathogens. The cells were non-motile and aerobic rods. The strain was able to grow at 4-40 °C (optimum 28-30 °C) and at pH 5.0-9.0 (optimum pH 7.0-8.5). Strain YC6887(T) was able to grow at NaCl concentrations of 0-9 % (w/v) with optimum growth at 4-5 % (w/v) NaCl, but NaCl is not essential for growth. Comparison of 16S rRNA gene sequences showed that the strain was a member of the genus Martelella, a member of order Rhizobiales, exhibiting highest similarity with Martelella mediterranea (98.6 %). The DNA-DNA relatedness between strain YC6887(T) and M. mediterranea MACL11(T) was 19.8 ± 6.8. Chemotaxonomically, strain YC6887(T) contained C19 : 0 cyclo ω8c (28.0 %) and C18 : 1ω7c (17.9 %) as predominant fatty acids, confirming the affiliation of strain YC6887(T) with the genus Martelella. The major respiratory quinone was Q-10 and the DNA G+C content was 62.1 mol%. On the basis of phylogenetic analysis, physiological and biochemical characterization and DNA-DNA hybridization data, strain YC6887(T) should be classified as representing a novel species of the genus Martelella, for which the name Martelella endophytica sp. nov. is proposed. The type strain is YC6887(T) ( = KCCM 43011(T) = NBRC 109149(T)).

Silicon-induced changes in antifungal phenolic acids, flavonoids, and key phenylpropanoid pathway genes during the interaction between miniature roses and the biotrophic pathogen Podosphaera pannosa

Application of 3.6 mm silicon (Si+) to the rose (Rosa hybrida) cultivar Smart increased the concentration of antimicrobial phenolic acids and flavonoids in response to infection by rose powdery mildew (Podosphaera pannosa). Simultaneously, the expression of genes coding for key enzymes in the phenylpropanoid pathway (phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase, and chalcone synthase) was up-regulated. The increase in phenolic compounds correlated with a 46% reduction in disease severity compared with inoculated leaves without Si application (Si-). Furthermore, Si application without pathogen inoculation induced gene expression and primed the accumulation of several phenolics compared with the uninoculated Si- control. Chlorogenic acid was the phenolic acid detected in the highest concentration, with an increase of more than 80% in Si+ inoculated compared with Si- uninoculated plants. Among the quantified flavonoids, rutin and quercitrin were detected in the highest concentrations, and the rutin concentration increased more than 20-fold in Si+ inoculated compared with Si- uninoculated plants. Both rutin and chlorogenic acid had antimicrobial effects on P. pannosa, evidenced by reduced conidial germination and appressorium formation of the pathogen, both after spray application and infiltration into leaves. The application of rutin and chlorogenic acid reduced powdery mildew severity by 40% to 50%, and observation of an effect after leaf infiltration indicated that these two phenolics can be transported to the epidermal surface. In conclusion, we provide evidence that Si plays an active role in disease reduction in rose by inducing the production of antifungal phenolic metabolites as a response to powdery mildew infection.

Phytophagous arthropods and a pathogen sharing a host plant: evidence for indirect plant-mediated interactions

In ecological systems, indirect interactions between plant pathogens and phytophagous arthropods can arise when infestation by a first attacker alters the common host plant so that although a second attacker could be spatially or temporally separated from the first one, the former could be affected. The induction of plant defense reactions leading to the production of secondary metabolites is thought to have an important role since it involves antagonistic and/or synergistic cross-talks that may determine the outcome of such interactions. We carried out experiments under controlled conditions on young rose plants in order to assess the impact of these indirect interactions on life history traits of three pests: the necrotrophic fungus Botrytis cinerea Pers.: Fr. (Helotiales: Sclerotiniaceae), the aphid Rhodobium porosum Sanderson (Hemiptera: Aphididae) and the thrips Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Our results indicated (i) a bi-directional negative interaction between B. cinerea and R. porosum, which is conveyed by decreased aphid growth rate and reduced fungal lesion area, as well as (ii) an indirect negative effect of B. cinerea on insect behavior. No indirect effect was observed between thrips and aphids. This research highlights several complex interactions that may be involved in structuring herbivore and plant pathogen communities within natural and managed ecosystems.

Haloferula luteola sp. nov., an endophytic bacterium isolated from the root of a halophyte, Rosa rugosa, and emended description of the genus Haloferula

A Gram-negative, non-spore-forming, endophytic bacterium, strain YC6886(T), was isolated from the root of a halophyte, Rosa rugosa, which inhabits coastal areas of Namhae Island off the southern coast of Korea. Cells were non-motile, obligately aerobic rods and formed pale-yellow colonies. The isolate grew at 4-32 °C (optimum 25-28 °C) and at pH 6.5-9.5 (optimum pH 7.5) and grew optimally with 2-3 % (w/v) NaCl, but NaCl was not an absolute requirement for growth. Strain YC6886(T) produced yellow carotenoid pigments. Strain YC6886(T) exhibited the highest 16S rRNA gene sequence similarity with Haloferula sargassicola MN1-1037(T) (97.4 %). Sequence similarities between strain YC6886(T) and other members of the genus Haloferula were 93.9-94.7 %. DNA-DNA relatedness between strain YC6886(T) and H. sargassicola KCTC 22202(T) and Haloferula rosea KCTC 22201(T) was 27 and 15 %, respectively. The major fatty acids were iso-C(14 : 0), C(16 : 0) and C(16 : 1)ω9c and minor components were C(14 : 0), C(18 : 0) and anteiso-C(15 : 0). The major respiratory quinone was menaquinone 9 and the DNA G+C content was 58.5 mol%. The polar lipid profile was composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unknown phospholipid and an unknown phosphoglycolipid. On the basis of phenotypic, chemotaxonomic, DNA-DNA hybridization and phylogenetic analysis, strain YC6886(T) represents a novel species in the genus Haloferula, for which the name Haloferula luteola sp. nov. is proposed. The type strain is YC6886(T) ( = KCTC 22447(T)  = DSM 21608(T)). An emended description of the genus Haloferula is also presented.

Rdr3, a novel locus conferring black spot disease resistance in tetraploid rose: genetic analysis, LRR profiling, and SCAR marker development

Black spot disease of rose, incited by the fungus Diplocarpon rosae, is found worldwide and is the most important disease of garden roses. A gene-for-gene interaction in this pathosystem is evidenced by the presence of pathogenic races of D. rosae and the previous discovery of a dominant resistance allele at the Rdr1 locus in the diploid Rosa multiflora. The objective of the present study was to genetically analyze resistances to North American black spot races 3, 8, and 9 previously reported in tetraploid roses. Resistance to North American races 3 and 8 segregated 1:1 in multiple F(1) populations, indicating that both are conferred by dominant alleles at single loci and are present in simplex (Rrrr) configuration. Gene pyramiding was demonstrated by combining both resistances into single genotypes. Resistance to race 9 was partial and segregated in a quantitative fashion. Analysis of these populations with microsatellite markers previously developed for Rdr1 revealed that the gene conferring race 3 resistance resides within the same R gene cluster as Rdr1. Race 8 resistance segregated independently and is, therefore, a novel locus for black spot resistance in rose which we have named Rdr3. NBS and LRR profiling were used in a bulked segregant analysis to identify a marker 9.1 cM from Rdr3, which was converted to a SCAR marker form for marker-assisted breeding.

Biological control of crown gall of grapevine, rose, and tomato by nonpathogenic Agrobacterium vitis strain VAR03-1

A nonpathogenic strain of Agrobacterium vitis VAR03-1 was tested as a biological control agent for crown gall of grapevine (Vitis vinifera). When roots of grapevine, rose (Rose multiflora), and tomato (Lycopersicon esculentum) were soaked in a cell suspension of antagonists before planting in soil infested with tumorigenic A. vitis, A. rhizogenes, and A. tumefaciens, respectively, treatment with VAR03-1 significantly reduced the number of plants with tumors and disease severity in the three plant species. The inhibitory effects of treatment with VAR03-1 and the nonpathogenic A. rhizogenes strain K84 on crown gall of rose and tomato were almost identical, and the inhibitory effect of VAR03-1 on grapevine was superior to that of K84. Moreover, VAR03-1 greatly controlled crown gall of grapevine due to tumorigenic A. vitis in the field. VAR03-1 established populations averaging 10(6) colony forming units (CFU)/g of root in the rhizosphere of grapevine and persisted on roots for 2 years. VAR03-1 was bacteriocinogenic, producing a halo of inhibition against those three species of Agrobacterium. This is the first report that a nonpathogenic strain, VAR03-1, can effectively control crown gall caused by tumorigenic A. vitis, A. rhizogenes, and A. tumefaciens.

Histological analyses of the fungal endophytes in Rosa hybrida

Endophytes are fungi that cause asymptomatic infections in leaves and stems of healthy plants. This study evaluated the presence of endophytic fungi on leaves of Rosa hybrida collected in Bogota, (Colombia) using histological techniques and light microscopy. Histological preparations showed fungal mycelium with few cells in the vascular tissue. Colonization of mesophyll cells was not observed. Visualization of fungal cells within plant tissues is a confirmatory test of the endophytic habitat of fungi isolated from leaves of Rosa hybrida.

Host-related variability in arbuscular mycorrhizal fungal structures in roots of Hedera rhombea, Rubus parvifolius, and Rosa multiflora under controlled conditions

The arbuscular mycorrhizal (AM) morphology of three host plant species inoculated with single and mixed fungal culture and the distribution of AM fungal species in roots of the hosts treated with a mixed culture of AM fungi were determined. The aim was to investigate the effect of host plants and AM fungi on AM morphology of coexisting plant species. Noncolonized rooted cuttings of Hedera rhombea (Miq) Bean, Rubus parvifolius L., and Rosa multiflora Thunb. were inoculated with five fungal species as single and mixed culture inocula. The fungal species used were Gigaspora rosea and Scutellospora erythropa, previously isolated from H. rhombea; Acaulospora longula and Glomus etunicatum from R. parvifolius; and Glomus claroideum from both plant species. A few hyphal and arbusculate coils were seen in the mixed culture-inoculated roots of R. parvifolius; all fungal treatments produced this Paris-type AM in H. rhombea and Arum-type AM in R. parvifolius, and R. multiflora indicates that AM morphology is strongly controlled by the identity of the host plants used in this study. AM fungal rDNA was extracted separately from roots of each replicate plant species inoculated with the mixed fungal culture, amplified, cloned, sequenced, and analyzed to determine the AM fungal species and their respective proportions in roots of each plant species. Glomus etunicatum and G. claroideum of the family Glomaceae generally occurred more frequently in R. parvifolius and R. multiflora, which form Arum-types, whereas S. erythropa, of the family Gigasporaceae, was the most frequently detected species in H. rhombea, which produced Paris-type AM. Although the genotype of the plant species used appears to determine the AM morphologies formed, there was preferential association between the hosts and AM fungal inoculants.

Characterisation of powdery mildew resistance in a segregating diploid rose population

Powdery mildew (Podosphaera pannoso) is one of the most serious fungal diseases on both greenhouse and field grown roses. Improvement of disease resistance is a major selection aim for garden rose breeders. For rose cultivars, being mostly tetraptoid, it is complicated to develop molecular markers for resistance. Hence, a segregating diploid population was established from a cross between 'Yesterday', a commercial available rose variety susceptible to powdery mildew, and R. wichurana, a rose species with resistance to certain isolates of powdery mildew. A progeny of 94 seedlings was planted in the field. The segregation of powdery mildew resistance was studied in this population by means of a bioassay with two different monoconidial isolates of powdery mildew. Based on the response to these inoculations different groups were selected: a first group of genotypes was susceptible to both isolates, other groups were susceptible to one of both isolates and a last group was resistant to both tested isolates. The disease resistance inherits for both isolates in a quantitative way. A genetic map based on AFLP and SSR markers was established and will be used for QTL analysis of powdery mildew resistance.

Powdery mildew resistance in roses: QTL mapping in different environments using selective genotyping

Podosphaera pannosa, the causal agent of rose powdery mildew, hampers the production of cut roses throughout the world. A major tool to control this disease is the use of resistant plant material. Single resistance genes, like Rpp1, may be overcome within a few years by high risk pathogens like powdery mildews. Durable resistance could be achieved using quantitative resistances. Here we describe mapping of QTLs for resistance to P. pannosa in six different environments (artificial and natural infections in the greenhouse over 3 years and natural infections in the field over 2 years). AFLPs, RGAs and other marker types were used to construct an integrated linkage map for the diploid population 97/7 containing 233 markers. In a selective genotyping procedure, marker segregation was analysed for 170 of the up to 270 phenotyped individuals. We identified seven linkage groups with an average length of 60 cM, corresponding to seven rose chromosomes in the haploid set. Using an LOD significance threshold of 3.9 we detected a total of 28 QTLs for the nine powdery mildew disease scores under analysis. Using the data from artificial inoculations with powdery mildew race 9, three resistance QTLs explaining about 84% of the variability were mapped. Twelve and 15 QTLs were detected for resistance to naturally occurring infections in the greenhouse and in the field, respectively, over several years.

Systemic movement of Agrobacterium tumefaciens in several plant species

AIMS

The systemic movement of Agrobacterium spp. inside plants of different species was studied to determine the most valuable diagnostic methodology for their detection.

METHODS AND RESULTS

Pathogenic agrobacteria were detected by isolation and PCR in tissue away from primary tumours in tomato plants grown in the presence of Agrobacterium spp. Moreover, this bacterium was also able to induce secondary tumours beyond the inoculation site. In addition, the capacity of agrobacteria to translocate and induce secondary tumours was analysed in rose, grapevine, chrysanthemum, cherry and peach x almond hybrid GF677. No differences among strains of Agrobacterium spp. were detected in secondary tumour development, although some of them induced a significantly higher number of primary tumours in some species. Movement of inoculated pathogenic cells of four strains was also demonstrated in symptomless portions of the plant stems by isolation and PCR. Finally, pathogenic agrobacteria were detected in root, crown and stem portions of naturally infected walnuts. In all assays, PCR was the most efficient technique for detecting the movement of Agrobacterium spp. within the plants.

CONCLUSIONS

Migration of agrobacteria inside plants is a complex phenomenon and more extensive than previously reported. Therefore, efficient and sensitive detection methods such as PCR must be used to select clean plants to avoid latent infections of Agrobacterium spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results show that migration of Agrobacterium spp. could be relatively frequent in several cultivated fruit trees, and systemic infections should be taken into account when designing strategies for controlling crown gall disease.

Downy mildews on ornamental plants and their control

Among downy mildews occurring on ornamentals in Poland the most dangerous are downy mildew of rose and downy mildew of German statice (Tartarian statice). Downy mildew of rose caused by Peronospora sparsa Berk. is a serious threat to commercial cultivation of cut roses, especially grown under plastic tunnels. Peronospora statices Lobik casual agent of German statice downy mildew can causes the total losses in the second year of statice cultivation more than 70%. Both pathogens are very difficult to control. Effectiveness of azoxystrobine, cymoxanil + famoxate, mancozeb, phosethyl aluminium, phosethyl aluminium + fenamidone, propamocarb in the control of P. sparsa and P. statices was presented. In the control of statice downy mildew none of tested compounds was able to control satisfactory the pathogen. Relatively the best results were obtained with mixture of fenamidone (88 microg/cm3) and phosethyl AL (1334 microg/cm3). In the control of rose downy mildew, the best results were obtained with phosethyl Al at concentration 1600 microg/cm3.

Mycorrhizal impact on drought stress tolerance of rose plants probed by chlorophyll a fluorescence, proline content and visual scoring

Micropropagated rose plants (Rosa hybrida L., cv. New Dawn) were inoculated with the arbuscular mycorrhizal (AM) fungus Glomus intraradices (Schenk and Smith) and subjected to different drought regimens. The dual objectives of these experiments were to investigate the mechanism and the extent to which AM can prevent drought damages and whether physiological analyses reveal enhanced drought tolerance of an economically important plant such as the rose. In a long-term drought experiment with four different water regimens, visual scoring of wilt symptoms affirmed that AM in a selected host-symbiont combination increased plant performance. This effect was mostly expressed if moderate drought stress was constantly applied over a long period. In a short-term experiment in which severe drought stress was implemented and plants were allowed to recover after 4 or 9 days, no visual differences between mycorrhizal and non-mycorrhizal roses were observed. Therefore, the early physiological steps conferring drought tolerance were prone to investigation. Proline content in leaves proved to be an unsuitable marker for AM-induced drought tolerance, whereas analysis of chlorophyll a fluorescence using the JIP test (collecting stress-induced changes of the polyphasic O-J-I-P fluorescence kinetics in a non-destructive tissue screening) was more explanatory. Parameters derived from this test could describe the extent of foliar stress response and help to differentiate physiological mechanisms of stress tolerance. AM led to a more intense electron flow and a higher productive photosynthetic activity at several sites of the photosynthetic electron transport chain. A K step, known as a stress indicator of general character, appeared in the fluorescence transient only in drought-stressed non-mycorrhizal plants; conversely, the data elucidate a stabilising effect of AM on the oxygen-evolving complex at the donor site of photosystem (PS) II and at the electron-transport chain between PS II and PS I. If drought stress intensity was reduced by a prolonged and milder drying phase, these significant tolerance features were less pronounced or missing, indicating a possible threshold level for mycorrhizal tolerance induction.

Isolation of TIR and non-TIR NBS--LRR resistance gene analogues and identification of molecular markers linked to a powdery mildew resistance locus in chestnut rose (Rosa roxburghii Tratt)

Toll and interleukin-1 receptor (TIR) and non-TIR nucleotide binding site-leucine rich repeat (NBS-LRR) resistance gene analogues (RGAs) were obtained from chestnut rose (Rosa roxburghii Tratt) by two PCR-based amplification strategies (direct amplification and overlap extension amplification) with degenerate primers designed to the conserved P-loop, kinase-2, and Gly-Leu-Pro-Leu (GLPL) motifs within the NBS domain of plant resistance gene (R gene) products. Thirty-four of 65 cloned PCR fragments contained a continuous open reading frame (ORF) and their predicted protein products showed homology to the NBS-LRR class R proteins in the GenBank database. These 34 predicted protein sequences exhibited a wide range (19.5--99.4%) of sequence identity among them and were classified into two distinct groups by phylogenetic analysis. The first group consisted of 23 sequences and seemed to belong to the non-TIR NBS-LRR RGAs, since they contained group specific motifs (RNBS-A-non-TIR motif) that are often present in the coiled-coil domain of the non-TIR NBS-LRR class R genes. The second group comprised 11 sequences that contained motifs found in the TIR domain of TIR NBS-LRR class R genes. Restriction fragment length polymorphic (RFLP) markers were developed from some of the RGAs and used for mapping powdery mildew resistance genes in chestnut rose. Three markers, RGA 22 C, RGA 4 A, and RGA 7 B, were identified to be linked to a resistance gene locus, designated CRPM 1 for chestnut rose powdery mildew resistance 1, which accounted for 72% of the variation in powdery mildew resistance phenotype in an F1 segregating population. To our knowledge, this is the first report on isolation, phylogenetic analysis and potential utilization as genetic markers of RGAs in chestnut rose.

Aislamiento de hongos endofitos en rosa (Rosa hybrida) en Bogotá, Colombia

We have investigated the presence of endophytic fungi associated with rose plants (Rosa hybrida) in Colombia. Endophytic fungi were isolated from healthy leaves of ten ornamental roses plants from gardens cultured in malt extract, peptone, yeast extract agar plates (MPY). We sampled 560 leaves fragments, 56 per sample. Endophytic fungi comprised 92 isolates (16.4%); of these isolates, 41 were classified as sterile mycelium (without reproductive structures that allowed their identification), 31 isolates were identified to genus or to species, and 20 isolates could not be identified at all. The identified endophytic fungi were as follow: Nigrospora oryzae, Aureobasidium spp, Acremonium spp. The fungi Nodulisporium sp, Gliocladium virens, Cladosporium sp, Alternaria sp, Phoma sp and Chaetomium globosum were represented by one isolate each. Since the endophytic fungi are known for their capacity to produce metabolites with biological activity, it is possible that the microorganisms found in this study have potential as antagonist of rose pathogens.

Different evolutionary histories of two Phragmidium species infecting the same dog rose hosts

Rust fungi in the genus Phragmidium are frequent pathogens of both wild and cultivated roses. We investigated the occurrence and relationships of rusts on dog roses, Rosa sect. Caninae (Rosa canina, R. corymbifera and R. rubiginosa) in Germany. Two Phragmidium species, P. mucronatum and P. tuberculatum, were able to infect each of the three dog rose species examined. However, the overall infection of R. rubiginosa was significantly lower, which could be important for rose breeding. Despite overlapping host ranges, the evolutionary background of P. tuberculatum and P. mucronatum is quite distinct. Phylogenetic analyses of the D1/D2 region of the LSU rDNA suggest that P. mucronatum shares a common ancestor with other rose rusts, whereas P. tuberculatum evolved from a Rubus-Sanguisorba rust clade and must have undergone a host shift to Rosa spp.

Tolylfluanide + tebuconazole in the control of some ornamental foliage diseases

In the control of Sphaerotheca pannosa var. rosae on rose Tolylfluanide + tebuconazole (Folicur Multi 50 WG at concentration 0.1%) was used for spray 2 -times at 14-day-intervals or 4-times at 7-day-intervals. After 4 weeks of plants protection effectiveness of tested product was about 75%. In the control of Diplocarpon rosae, the product was applied when first disease symptoms appeared on rose shrubs. Application was repeated 5-times at 14-day-intervals or 9-times at 7-day-intervals. After 9 week-protection effectiveness of tested product was about 85% and depended on frequency of sprayings. In the control of Puccinia horiana on chrysanthemum, Tolylfluanide + tebuconazole was used as plant spray twice at 14-day-intervals or 4-times at 7-day-intervals. After 4 week-protection the product suppressed of new telia formation about 55%. Application of the product for willow rust (Melampsora epitea) control suppressed formation of new uredia about 86% and half of them were dried. In the control of pelargonium rust (Puccinia pelargonii-zonalis) the product was used as plant spray 4-times at 7-day-intervals. It suppressed formation of new uredia about 90% and 1/3 of them were dried. It was found that 1 or 7 days after rose spray, spores of D. rosae collected from leaf blades only in 6% germinated. Spores taken from nonspraying leaves germinated in 90%. In case of P. pelargonii-zonalis, after 1 or 7 days after spraying, spores collected from protected plants germinated at 3%, compared to 90% on untreated plants. Spores of B. cinerea, collected from protected plants germinated at about 10%, whereas on control leaves at 90%.

Chitosan (biochikol 020 PC) in the control of some ornamental foliage diseases

Chitosan, (Biochikol 020 PC) a potential elicitor of plant defence and also an active inhibitor of fungal growth was used in experiments. The compound was used at concentrations 0.01 to 0.2% as a plant spray for rose protection against Sphaerotheca pannosa var. rosae, Peronospora sparsa and Diplocarpon rosae, Oidium chrysanthemi and Puccinia horiana on chrysanthemum, against Melampsora epitea on willow. Myrothecium roridum on dieffenbachia and against Lophodermium spp on Scots pine. Effectiveness of this product, applied curatively 2-times at 7-day-intervals after appearance of rose powdery mildew symptoms on most of plant parts, was about 32%. When compound was applied just after the first disease symptoms appearance, after 2-week-protection its effectiveness was about 43-60%. After 4 weeks, effectiveness of chitosan (Biochikol 020 PC) increased and ranged from 67 to 77%. In the control of P. sparsa on rose shrubs, growing in plastic tunnel, chitosan at conc. 0.025% was applied 4 times at weekly intervals. Effectiveness of chitosan against this pathogen was over 72%, similar as standard fungicide. Increase of chitosan (Biochikol 020 PC) concentration resulted in decrease of its effectiveness. In case of D. rosae control, chitosan used 9 times at weekly intervals was applied after first disease symptoms. After 3-week-protection effectiveness of the compound varied from 18 to 60% according to used concentration. After 9 weeks of protection effectiveness of tested product ranged from 16 to 23% and was connected with used concentration. Increase of chitosan concentration resulted in better protection of rose shrubs. Effectiveness of chitosan (Biochikol 020 PC) used 4-times at conc. 0.01 to 0.05% as chrysanthemum spray in the control of Oidium chrysanthemi ranged from 69 to 79%, whereas against Puccinia horiana from 54-97%. Two-time-spraying of willow with rust symptoms (Melampsora epitea) with chitosan at conc. 01-0.04% caused decrease of disease severity from 26 to 47%. Additionally about 10 to 25% of uredinia were dried up. Chitosan (Biochikol 020 PC) applied for leaf spraying inhibited the development of Myrothecium leaf spot on dieffenbachia more than 85%. Curative application of the compound controlled Myrotecium leaf spot at about 40%. Chitosan efficacy was also tested against one-year-old Pinus sylvestris seedlings growing in field conditions. Plants were sprayed fortnightly 14-times (long programme) or 5-times (short programme) against Lophodermium spp. Observations made during next spring showed that effectiveness of chitosan (Biochikol 020 PC) was more than 50% (long programme) and below 50% (short programme).

Transgenic rose lines harboring an antimicrobial protein gene, Ace-AMP1, demonstrate enhanced resistance to powdery mildew ( Sphaerotheca pannosa)

An antimicrobial protein gene, Ace-AMP1, was introduced into Rosa hybrida cv. Carefree Beauty via Agrobacterium-mediated transformation. A total of 500 putative transgenic plants were obtained from 100 primary embryogenic calli co-cultivated with A. tumefaciens following selection on a regeneration medium containing 100 mg/l kanamycin. Polymerase chain reaction analysis of these putative transgenic lines, using primers for both Ace-AMP1 and neomycin phosphotransferase ( npt II) genes, showed that 62% of these plants were positive for both transgenes. These lines were further confirmed for stable integration of Ace-AMP1 and npt II genes by Southern blotting. Transcription of the Ace-AMP1 transgene in various transgenic rose lines was determined using Northern blotting. Transgenic rose lines inoculated with conidial spores of Sphaerotheca pannosa (Wallr.: Fr.) Lev. var. rosae showed enhanced resistance to powdery mildew using both a detached-leaf assay and an in vivo greenhouse whole-plant assay.

Oils activity in the control of rose powdery mildew

The efficacy and eventual phytotoxicity of oils from rape, sunflower seed (vegetable oil) and paraffin (Atpolan 80 EC) in the control of Sphaerotheca pannosa var. rosae were evaluated on roses grown in greenhouse or plastic tunnel. Oils were applied curativelly as plant spray 4-times at 7-day-intervals in concentrations from 0.25 to 4%. All used oils, gave as good effect as triforine (standard) or even better. On shrubs protected with oils at concentrations 0.25% and 0.5%, disease symptoms were noted only sporadically. Rose shrubs sprayed with higher concentration of oils were almost completely protected. Efficacy of tested oils increased with their concentrations. Paraffin oil was better in the control of S. pannosa var. rosae than vegetable oils. After 2 oil applications at conc. 2% or higher, first phytotoxicity symptoms on leaves were noted, particularly during warm and sunny days. Observations of treated leaves, 24 h after spraying under microscope, showed that all tested oils caused hyphae and spores degeneration or their visible deformation suggesting partial loss of turgidity. Depends on oil concentrations used, sporadically regular and unchanged shape hyphae and spores were visible.

Isolation and identification of eight races of powdery mildew of roses (Podosphaera pannosa) (Wallr.: Fr.) de Bary and the genetic analysis of the resistance gene Rpp1

Powdery mildew, caused by Podosphaera pannosa, is one of the most-severe diseases of roses grown under glass. The differentiation into physiological races and the genetic analysis of resistance in a segregating host population was investigated using single conidial isolates of the pathogen. Using ten rose genotypes, all eight isolates of the pathogen could be ascribed to different races. Five races were isolated from one location, which indicates that populations of P. pannosa exhibit a high racial diversity. Infection experiments in a backcross-population of 114 rose plants resulted in a 1:1 segregation, suggesting control by a single dominant gene. Rpp1 is the first resistance gene against rose powdery mildew to be described.

[The quantity and structure of the root-associated microbial complexes of two greenhouse rose cultivars]

The study of the root-associated microbial complexes of affected and healthy rose plants of two cultivars (Grand gala and Royal velvet) grown in a greenhouse showed that the biomass of eukaryotic microorganisms in the rhizoplane and rhizosphere of healthy rose plants and in the surrounding soil was considerably lower than in the same loci of affected plants. In contrast, the biomass of root-associated prokaryotic microorganisms was higher in the case of healthy than in the case of affected rose plants. The root-associated bacterial complexes of both affected and healthy rose plants were dominated by the genera Arthrobacter, Rhodococcus, and Myxobacterium and did not contain phytopathogenic bacteria. The root-associated fungal complex of healthy roses was dominated by fungi of the genus Trichoderma, whereas that of the affected rose plants was dominated by the species Aureobasidium microstictum. The affected cane cuttings and cankers occurring on affected canes were found to contain Coniothyrium fuckelii (the causal fungus of rose stem canker) and sclerotia of Botrytis cinerea (the causal fungus of gray rot). The micromycete complex of healthy rose plants was not so diverse as was the micromycete complex of affected rose plants.

Construction of a BAC library of Rosa rugosaThunb. and assembly of a contig spanning Rdr1, a gene that confers resistance to blackspot

A BAC library to serve as a general tool for the physical mapping and positional cloning of rose genes has been constructed from Rosa rugosa DNA. With 27,264 clones the library contains 5.2 genome equivalents. The library was used to assemble a contig of BAC clones spanning Rdr1, a locus that confers resistance to blackspot. For this purpose fine-scale mapping of the target locus was achieved by bulked segregant analysis using 816 AFLP primer combinations. The target region around Rdr1 comprises about 400 kb and is covered by a minimum of six BAC clones. Furthermore, the detection of at least five resistance gene analogs of the TIR-NBS-LRR family on the contig indicates the presence of a cluster of resistance genes around Rdr1. These results will not only allow the isolation and identification of Rdr1 in the near future, but also provide the tools for the physical mapping and positional cloning of other horticulturally interesting genes in roses.

Efficacy of salts against fungal diseases in glasshouse crops

The constant input of chemical fungicides against foliar diseases in glasshouse crops has instigated research on alternative control substances. Various salts have been mentioned in the literature and we have tested several bicarbonates, sulphates and phosphates against powdery mildew fungi in cucumber, tomato, sweet pepper and rose and against Bremia lactucae in lettuce. The experiments were run according to EPPO guidelines for efficacy in glasshouses of Applied Plant Research (PPO). Plants were sprayed weekly and disease and yield were assessed. In cucumber, NaHCO3, KHCO3, MgSO4 and MnSO4 all reduced powdery mildew significantly, with MnSO4 as the most effective agent. In tomato, MgSO4, MnSO4 and KH2PO4 all reduced powdery mildew by approx. 40% whereas NaHCO3 and KHCO3 gave approx. 95% control. In pepper, NaHCO3 controlled Leveillula taurica by 50-90% compared to the untreated control. In rose, the efficacy of KH2PO4, MnSO4, MgSO4, NaHCO3 and KHCO3 against powdery mildew differed between cultivars. In general, the bicarbonates were the most effective compounds. In lettuce, NaHCO3 reduced Bremia severity by 70 to 80%. The conclusion of this range of experiments is that especially bicarbonates can be a good alternative for control of foliar fungal diseases in glasshouse crops. The effective concentration is not causing any symptoms of phytotoxicity, provided that spraying is not done at high irradiation conditions. Bicarbonates have been submitted for the Dutch list of exceptions on the Pesticide Law.

Activity of some chemicals in the control of Botrytis cinerea on roses

In the control of grey mould (Botrytis cinerea) on rose petals all 15 tested fungicides used as a spray, suppressed very effectively development of necrosis. But the best results in suppression of necrosis development, more than 90% effectiveness gave: Amistar 250 SC (azoxystrobin), Bravo 500 SC (chlorothalonil), Discus 500 WG (kresoxim methyl), Euparen 50 WP (dichlofluanid) Euparen Multi 50 WG (tolyfluanid), Folpan 80 WG (folpet), Kaptan zaw. 50 WP (captan), Penncozeb 80 WP (mancozeb), Ronilan 50 WP (vinclozolin), Rovral Flo 255 SC (iprudione), Sumilex 500 SC (procymidone) and Teldor 500 SC (fenhexamid). When Dithane M-45 80 WP (mancozeb), Sarbrawit 530 SC (chlorothalonil + carbendazim) or Topsin M 70 WP (thiophanate methyl) were used, the diameter of spots was about 6-times smaller than on control flowers (about 84% effectiveness). All tested fungicides used for spraying of flower petals with abundant visible sporulation of B. cinerea were ineffective in the inhibition of spore germination. But when Petri dishes with potato-dextrose-agar were sprayed with tested fungicides and inoculated with spore suspension, Euparen 50 WP, Euparen Multi 50 WG, Folpan 80 WG, Kaptan zaw. 50 WP and Penncozeb 80 WP completely suppressed conidia germination.

Molecular diagnostic procedures for production of pathogen-free propagation material

Production of disease-free propagation material is a major means of controlling most bacterial diseases of plants, particularly when neither resistant clones nor effective chemical treatments are available. For this purpose sensitive, specific and rapid detection methods are required. The advent of molecular biology and, in particular, the polymerase chain reaction (PCR) has opened new ways for the characterization and identification of plant pathogens and the development of disease-management strategies. PCR-based detection methods rely on the development of primers for the specific detection of the pathogen. The use of pathogenicity genes as targets for primer design is the preferred procedure for obtaining specific primers but other procedures may also be useful for this purpose. In the present review we describe four examples of procedures for detecting four important bacterial pathogens in Israel: Erwinia herbicola pv gypsophilae in gypsophila, Xanthomonas campestris pv pelargonii in geranium, Agrobacterium tumefaciens in asters and roses, and Xanthomonas campestris pv campestris in crucifers. Procedures for constructing specific PCR primers for each bacterium are illustrated and discussed as well as the combination of PCR with other methods.