Diaporthe species infecting sunflower (Helianthus annuus) in Russia, with the description of two new species

Diaporthe species causing shoot dieback of Acer (maple) in Henan Province, China

BACKGROUND

Maple is an important ornamental plant in China. With the increasing use of maple trees in landscaping, a symptom of shoot dieback has been observed in Henan province, China.

RESULTS

In this study, 28 Diaporthe isolates were obtained from symptomatic shoots of maple trees between 2020 and 2023. Phylogenetic analyses based on five loci (ITS, TEF, CAL, HIS and TUB) coupled with morphology of 12 representative isolates identified three known species (D. eres, D. pescicola and D. spinosa) and one new species, namely D. pseudoacerina sp. nov. Koch's postulates confirmed that all these species were pathogenic. Additionally, D. pseudoacerina was able to infect China wingnut (Pterocarya stenoptera), pear (Pyrus sp.), and black locust (Robinia pseudoacacia). This study marks the first report of Diaporthe spinosa and D. pescicola pathogens infecting maple trees.

CONCLUSIONS

These findings enhance the existing knowledge of the taxonomy and host diversity of Diaporthe species as, while also providing valuable information for managing of maple shoot dieback in Henan Province, China.

Diversity and Aggressiveness of the Diaporthe Species Complex on Sunflower in Serbia

This study aimed to investigate the Diaporthe species associated with Phomopsis stem canker of sunflower (Helianthus annuus L.) in Serbia. The significant increase in sunflower and soybean (Glycine max [L.] Merr.) cultivation may have created the bridge favorable conditions for the distribution of Diaporthe species in this region. The present study identified five Diaporthe species on sunflower: D. gulyae, D. helianthi, D. pseudolongicolla, D. stewartii, and the newly identified D. riccionae based on morphological, molecular, and pathogenic characteristics. The research emphasizes the importance of effective inoculation methods and evaluates the aggressiveness of isolates. Sunflower plants were inoculated using the stem wound method, while seeds of sunflower and soybean were inoculated using the standard seed method. Most of the tested isolates demonstrated high aggressiveness, resulting in more than 80% premature wilting of sunflower plants. Additionally, this research examined the aggressiveness of Diaporthe species on sunflower seeds, highlighting D. stewartii and D. pseudolongicolla as common pathogens of both sunflower and soybean. The most aggressive species on seeds was D. stewartii, causing seed decay of up to 100% in sunflower and 97% in soybean. The findings suggest the development of resilient sunflower genotypes through breeding programs and the implementation of strategies to manage cross-contamination risks between sunflower and soybean crops. Furthermore, this study provides insights into the interactions between Diaporthe species and the seeds of sunflower and soybean. Future research will enhance our understanding of the impact of Diaporthe species on sunflower and soybean.

Natural ten-membered lactones: sources, structural diversity, biological activity, and intriguing future

Covering: 2012 to 2022Ten-membered lactones (TMLs) are an interesting and diverse group of natural polyketides that are abundant in fungi and, to a lesser extent, in bacteria, marine organisms, and insects. TMLs are known for their ability to exhibit a wide spectrum of biological activity, including phytotoxic, cytotoxic, antifungal, antibacterial, and others. However, the random discovery of these compounds by scientific groups with various interests worldwide has resulted in patchy information about their distribution among different organisms and their biological activity. Therefore, despite more than 60 years of research history, there is still no common understanding of the natural sources of TMLs, their structural type classification, and most characteristic biological activities. The controversial nomenclature, incorrect or erroneous structure elucidation, poor identification of producing organisms, and scattered information on the biological activity of compounds - all these factors have led to the problems with dereplication and the directed search for TMLs. This review consists of two parts: the first part (Section 2) covers 104 natural TMLs, published between 2012 and 2022 (after the publishing of the previous review), and the second part (Section 3) summarizes information about 214 TMLs described during 1964-2022 and as a result highlights the main problems and trends in the study of these intriguing natural products.

Fusarium bilaiae, a new cryptic species in the Fusarium fujikuroi complex associated with sunflower

A Fusarium species associated with sunflower based on multilocus genealogy, morphological, physiological, ecological, mating type, and mycotoxin production data is formally described as the newly discovered species Fusarium bilaiae. The F. bilaiae strains formed a genealogically exclusive lineage within the African clade of the F. fujikuroi species complex. Comparison of morphological characteristics of F. bilaiae strains with those of the closely related F. phyllophilum strain NRRL 13617 revealed similarities in the main micromorphology of both species: production of numerous one-celled microconidia in false heads and short chains on monophialides and polyphialides and the absence of macroconidia and sporodochia. There was a slight but significant distinction between the two species when the strains were grown on different agar media, as well as in the shape and width of microconidia. Fusarium bilaiae strains isolated from symptomatic sunflower were not pathogenic to members of the Asteraceae tested; apparently, they live as saprophytes or endophytes in sunflower tissues. A difference between the strains of the two species in the production of mycotoxins was demonstrated with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis. On autoclaved rice, F. bilaiae did not produce fumonisins and beauvericin but produced moniliformin, whereas F. phyllophilum produced all these mycotoxins. A polymerase chain reaction (PCR) assay specific for mating type alleles identified F. bilaiae as a putative heterothallic species with MAT1-1 and MAT1-2 idiomorphs, but laboratory crosses were unsuccessful. Determining the area and host range of the new endophytic species F. bilaiae is a priority for future research.

Four new endophytic species of Diaporthe (Diaporthaceae, Diaporthales) isolated from Cameroon

The genus Diaporthe (Diaporthaceae, Diaporthales) is a large group of fungi frequently reported as phytopathogens, with ubiquitous distribution across the globe. Diaporthe have traditionally been characterized by the morphology of their ana- and teleomorphic state, revealing a high degree of heterogeneity as soon as DNA sequencing was utilized across the different members of the group. Their relevance for biotechnology and agriculture attracts the attention of taxonomists and natural product chemists alike in context of plant protection and exploitation for their potential to produce bioactive secondary metabolites. While more than 1000 species are described to date, Africa, as a natural habitat, has so far been under-sampled. Several endophytic fungi belonging to Diaporthe were isolated from different plant hosts in Cameroon over the course of this study. Phylogenetic analyses based on DNA sequence data of the internal transcribed spacer region and intervening 5.8S nrRNA gene, and partial fragments of the calmodulin, beta-tubulin, histone and the translation elongation factor 1-α genes, demonstrated that these isolates represent four new species, i.e. D.brideliae, D.cameroonensis, D.pseudoanacardii and D.rauvolfiae. Moreover, the description of D.isoberliniae is here emended, now incorporating the morphology of beta and gamma conidia produced by two of our endophytic isolates, which had never been documented in previous records. Moreover, the paraphyletic nature of the genus is discussed and suggestions are made for future revision of the genus.

Integrative Taxonomy of Novel Diaporthe Species Associated with Medicinal Plants in Thailand

During our investigations of the microfungi on medicinal plants in Thailand, five isolates of Diaporthe were obtained. These isolates were identified and described using a multiproxy approach, viz. morphology, cultural characteristics, host association, the multiloci phylogeny of ITS, tef1-α, tub2, cal, and his3, and DNA comparisons. Five new species, Diaporthe afzeliae, D. bombacis, D. careyae, D. globoostiolata, and D. samaneae, are introduced as saprobes from the plant hosts, viz. Afzelia xylocarpa, Bombax ceiba, Careya sphaerica, a member of Fagaceae, and Samanea saman. Interestingly, this is the first report of Diaporthe species on these plants, except on the Fagaceae member. The morphological comparison, updated molecular phylogeny, and pairwise homoplasy index (PHI) analysis strongly support the establishment of novel species. Our phylogeny also revealed the close relationship between D. zhaoqingensis and D. chiangmaiensis; however, the evidence from the PHI test and DNA comparison indicated that they are distinct species. These findings improve the existing knowledge of taxonomy and host diversity of Diaporthe species as well as highlight the untapped potential of these medicinal plants for searching for new fungi.