First Report of Pilidiella granati Causing Dieback and Fruit Rot of Pomegranate (Punica granatum) in Iran

Characterization of Coniella granati Isolates Causing Pomegranate Decline in Italy

Coniella granati, the causal agent of pomegranate crown rot, twig blight, and fruit decay, is an emerging worldwide pathogen with a heavy impact on pomegranate cultivation. In this study, we report the rapid spread of the fungus in Italian pomegranate orchards associated with crown rot symptoms and provide new results on fungal development, baseline sensitivity to different fungicides, and intraspecific variability by analyzing 11 isolates, representative of populations of the pathogen from comparable pomegranate orchards in different regions of Italy. In vitro assays showed that 25 to 30°C was the optimal range for both colony growth and conidial germination, corroborating the results previously obtained for Californian and Greek isolates. According to the baseline sensitivity assay on the response of colony growth and conidial germination to 10 fungicides, fludioxonil, thiophanate-methyl, tebuconazole, and cyprodinil were the most effective. Random amplified polymorphic DNA (RAPD) analysis, carried out using fourteen 10-mer primers, showed very low intraspecific variability (similarity coefficient >0.95), probably as a result of the recent spread of the pathogen in Italy and the uncommon occurrence of the sexual process as a source of genetic variability. In summary, this study provides new knowledge on C. granati that will be helpful for improving pomegranate crown rot management.

Biological Activity of Pyraclostrobin Against Coniella granati Causing Pomegranate Crown Rot

Pomegranate crown rot caused by Coniella granati is one of the most severe diseases of pomegranate. No fungicides have been registered for controlling this disease in China. Pyraclostrobin, belonging to strobilurin fungicides, has a broad spectrum of activity against many phytopathogens. In this study, based on the mycelial growth and conidial germination inhibition methods, we investigated the biological activity of pyraclostrobin against C. granati in the presence of 50 μg/ml of salicylhydroxamic acid using 80 isolates collected from different orchards in China from 2012 to 2018. The EC₅₀ (50% effective concentration) values ranged from 0.040 to 0.613 μg/ml for mycelial growth and 0.013 to 0.110 μg/ml for conidium germination. Treated with pyraclostrobin, the hyphae morphology changed and conidial production of C. granati decreased significantly. The result of transmission electron microscope showed that treatment of pyraclostrobin could make the cell wall thinner and lead to ruptured cell membrane and formation of intracellular organelle autophagosomes. The pyraclostrobin showed good protective and curative activities against C. granati on detached pomegranate fruits. In field trials, pyraclostrobin showed excellent control efficacy against this disease, in which the treatment of 25% pyraclostrobin EC 1,000× provided 92.25 and 92.58% control efficacy in 2019 and 2020, respectively, significantly higher than that of other treatments. Therefore, pyraclostrobin could be a candidate fungicide for the control of pomegranate crown rot.

Agrobacterium tumefaciens-mediated transformation of Coniella granati

Pomegranate fruit rot caused by Coniella granati is among the most devastating diseases threatening pomegranate production. The pathogenic mechanism of this pathogen remains largely unknown due to lack of genetic transformation method. Herein, we developed an approach to the Agrobacterium tumefaciens-mediated transformation (ATMT) of C. granati using a plasmid vector encoding the green fluorescent protein (GFP) and hygromycin resistance (Hyg) genes. This approach yielded C. granati transformants that exhibited uniform, stable green fluorescence. We further optimized this ATMT protocol, enabling us to achieve a transformation efficiency of up to 300 transformants per 0.5 cm² mycelial plug. Together, we thus provide the first report of the stable transformation of C. granati, laying a foundation for future functional studies characterizing this economically important fungal pathogen.

The Effect of Polyphenols on Pomegranate Fruit Susceptibility to Pilidiella granati Provides Insights into Disease Tolerance Mechanisms

Pilidiella granati, also known as Coniella granati, is the etiological agent of pomegranate fruit dry rot. This fungal pathogen is also well-known as responsible for both plant collar rot and leaf spot. Because of its aggressiveness and the worldwide diffusion of pomegranate crops, the selection of cultivars less susceptible to this pathogen might represent an interesting preventive control measure. In the present investigation, the role of polyphenols in the susceptibility to P. granati of the two royalties-free pomegranate cultivars Wonderful and Mollar de Elche was compared. Pomegranate fruit were artificially inoculated and lesion diameters were monitored. Furthermore, pathogen DNA was quantified at 12-72 h post-inoculation within fruit rind by a real time PCR assay setup herein, and host total RNA was used in expression assays of genes involved in host-pathogen interaction. Similarly, protein extracts were employed to assess the specific activity of enzymes implicated in defense mechanisms. Pomegranate phenolic compounds were evaluated by HPLC-ESI-MS and MS2. All these data highlighted 'Wonderful' as less susceptible to P. granati than 'Mollar de Elche'. In the first cultivar, the fungal growth seemed controlled by the activation of the phenylpropanoid pathway, the production of ROS, and the alteration of fungal cell wall. Furthermore, antifungal compounds seemed to accumulate in 'Wonderful' fruit following inoculation. These data suggest that pomegranate polyphenols have a protective effect against P. granati infection and their content might represent a relevant parameter in the selection of the most suitable cultivars to reduce the economic losses caused by this pathogen.

Identification the Pathogens Causing Rot Disease in Pomegranate (Punica granatum L.) in China and the Antifungal Activity of Aqueous Garlic Extract

Rot disease is a serious disease in pomegranate (Punica granatum L.) plantations in China. This disease usually weakens tree vigor, and seriously reduces the ornamental value, fruit yield, and quality. A better understanding of the pathogen that causes a disease is important for its control. Thus, the aims of this study were to isolate and identify the pathogen causing rot disease and to explore substances for its biological control. In this study, the morphology of the hyphae and spores of the pathogens was observed, and the pathogens were identified by morphological characteristics and the internal transcribed spacer (ITS) regions of their rDNA. Furthermore, the activity of an aqueous garlic extract as antifungal treatment for the identified pathogens was assessed. The results showed that the pathogens causing soft rot and dry rot in ‘Xinjiang Big Seed’ pomegranate were most probably Aspergillus niger and Botryosphaeria dothidea, respectively. In addition, the pathogenicity of A. niger was stronger than that of B. dothidea. The aqueous garlic extract had a strong antifungal effect on both pathogens by inhibiting mycelium growth in vitro, and the minimum inhibitory concentrations against A. niger and B. dothidea were 7.5 mg/mL and 10 mg/mL, respectively.

Development of a nested-PCR assay for the rapid detection of Pilidiella granati in pomegranate fruit

Pilidiella granati, a causal agent of twig blight and crown rot of pomegranate, is an emerging threat that may cause severe risk to the pomegranate industry in the future. Development of a rapid assay for the timely and accurate detection of P. granati will be helpful in the active surveillance and management of the disease caused by this pathogen. In this study, a nested PCR method was established for the detection of P. granati. Comparative analysis of genetic diversity within 5.8S rDNA internal transcribed spacer (ITS) sequences of P. granati and 21 other selected fungal species was performed to design species-specific primers (S1 and S2). This primer pair successfully amplified a 450 bp product exclusively from the genomic DNA of P. granati. The developed method can detect 10 pg genomic DNA of the pathogen in about 6 h. This technique was successfully applied to detect the natural infection of P. granati in the pomegranate fruit. The designed protocol is rapid and precise with a high degree of sensitivity.

Revising the Schizoparmaceae: Coniella and its synonyms Pilidiella and Schizoparme

The asexual genera Coniella (1918) and Pilidiella (1927), including their sexual morphs in Schizoparme (1923), have a cosmopolitan distribution and are associated with foliar, fruit, leaf, stem and root diseases on a wide variety of hosts. Species of these genera sometimes occur as secondary invaders of plant tissues infected by other organisms or that are injured by other causes. Several studies published over the last few decades had conflicting ideas as to whether Coniella, Pilidiella and Schizoparme should be regarded as synonymous or as separate genera. The present study aims to resolve the generic classification of these genera through phylogenetic analyses of the concatenated alignment of partial LSU nrDNA, rpb2, ITS nrDNA and tef1 sequence data of 117 isolates, combined with their morphology. Results revealed that all strains cluster in a single well-supported clade. Conidial colour, traditionally the distinguishing character between Coniella and Pilidiella, evolved multiple times throughout the clade, and is not a good character at generic level in Schizoparmaceae. The three genera should therefore be regarded as synonymous, with the older name Coniella having priority. Furthermore, this study delineated 13 new species, and new combinations were proposed for a further 15 species.

Isolation, diversity and acetylcholinesterase inhibitory activity of the culturable endophytic fungi harboured in Huperzia serrata from Jinggang Mountain, China

Huperzia serrata has many important medicinal properties with proven pharmacological potential. Some of these properties may be mediated by its endophytic fungi. To test this hypothesis, in the present study, we provided a first insights into evaluating the species composition and acetylcholinesterase (AChE) inhibitory activity of the culturable endophytic fungi of H. serrata from the regional at Jinggang Mountain in southeastern China. A total number of 885 fungal isolates distributed across 44 genera and 118 putative species were obtained from 1422 fragments of fine H. serrata roots, stems and leaves base on ITS-rDNA sequences BLAST analysis. The endophytic fungi were phylogenetically diverse and species-rich, with high rate of colonization and isolation. The assemble of endophytic fungi consisted mainly of Ascomycota (97.15%), followed by Basidiomycota (1.92%) and unknown fungal species (0.90%). Colletotrichum (64.29%), Phyllosticta (3.39%), Hypoxylon (2.81%), Xylaria (2.25%) and Nigrospora (2.04%) were the most abundant genera, whereas the remaining genera were infrequent groups. Although, roots yielded low abundance strains, the diverse and species-rich were both higher than that of stems and leaves. In addition, out of the 247 endophytic fungi strains determinated, 221 fungal extracts showed AChE inhibition activities in vitro. Among them, 22 endophytic fungi strains achieved high inhibitory activity (≥50%) on AChE which belongs to 13 genera and five incertae sedis strains. Four endophytic fungi designated as JS4 (Colletotrichum spp.), FL14 (Ascomycota spp.), FL9 (Sarcosomataceae spp.) and FL7 (Dothideomycetes spp.) were displayed highly active (≥80%) against AChE, which the inhibition effects were even more intense than the positive control. Our findings highlight that H. serrata grown in Jinggang Mountain harbors a rich and fascinating endophytic fungus community with potential AChE inhibitory activity, which could further broaden the natural acetylcholinesterase inhibitors resources used for Alzheimer's disease treatment.