The phoma-like dilemma Hou, L.W.; Groenewald, J.Z.; Pfenning, L.H. ...
Studies in mycology,
06/2020, Volume:
96, Issue:
1
Journal Article
Peer reviewed
Open access
Species of Didymellaceae have a cosmopolitan distribution and are geographically widespread, occurring in diverse ecosystems. The family includes several important plant pathogenic fungi associated ...with fruit, leaf, stem and root diseases on a wide variety of hosts, as well as endophytic, saprobic and clinically relevant species. The Didymellaceae was recently revised based on morphological and phylogenetic analyses of ex-type strains subjected to DNA sequencing of partial gene data of the LSU, ITS, rpb2 and tub2 loci. Several poly- and paraphyletic genera, including Ascochyta, Didymella and Phoma were redefined, along with the introduction of new genera. In the present study, a global collection of 1 124 Didymellaceae strains from 92 countries, 121 plant families and 55 other substrates, including air, coral, human tissues, house dust, fungi, insects, soil, and water were examined via multi-locus phylogenetic analyses and detailed morphological comparisons, representing the broadest sampling of Didymellaceae to date. Among these, 97 isolates representing seven new genera, 40 new species and 21 new combinations were newly introduced in Didymellaceae. In addition, six epitypes and six neotypes were designated to stabilise the taxonomy and use of older names. A robust, multi-locus reference phylogenetic tree of Didymellaceae was generated. In addition, rpb2 was revealed as the most effective locus for the identification of Didymellaceae at species level, and is proposed as a secondary DNA marker for the family.
Epicoccum
species are ubiquitous ascomycetes. Several species are known to cause plant diseases and some species act as biological control agents against a range of plant pathogens. Accurate ...identification of
Epicoccum
species is paramount to a successful disease management program and successful development of biological control products. There are 18
Epicoccum
species that are associated with diseases of 46 plant species. The diseases occur in 20 countries with leaf spot as the most commonly reported disease symptom. There are a further five
Epicoccum
species (
E. nigrum, E. layuense, E. dendrobii, E, mezzettii
and
E. minitans
) that have biological control activity against various plant pathogens. Of the five species,
Epicoccum nigrum
is the most promising and has been shown to reduce incidence and severity of a wide range of plant diseases. The use of bioactive metabolites (e.g. flavipin and epicolactone) from
Epicoccum
spp. may offer growers a cheap and safe alternative to conventional pesticides which are widely used to manage plant diseases. We review the current knowledge of
Epicoccum
species, both those species that are plant pathogens, and those species that are biological control agents for plant disease.
The cover picture shows on the left-hand side, sugarcane growing in S. Paulo, Brazil, from which the endophytic fungus Epicoccum nigrum was isolated. A picture of this fungus growing on an agar plate ...is also shown. The X-ray crystallographic structure of epicolactone, a novel E. nigrum pentacyclic metabolite isolated from an ethyl acetate extract, is depicted on the right-hand side. Evidence suggests that epicolactone is produced through a polyketide synthase (PKS) biosynthetic pathway. Details are discussed in the article by A. J. Marsaioli et al. on p. 5225 ff. We thank Yara Gomes Pereira Aparicio for the cover picture design.
Plants with certain medicinal values are a good source for isolating function-specific endophytes.
Rosa roxburghii
Tratt. has been reported to be a botanical source of antimicrobial compounds, which ...may represent a promising candidate for screening endophytic fungi with antimicrobial potential. In this study, 54 endophytes were isolated and molecularly identified from
R. roxburghii
. The preliminary screening using the plate confrontation method resulted in 15 different endophytic strains showing at least one strong inhibition or three or more moderate inhibition against the 12 tested strains. Further re-screening experiments based on the disc diffusion method demonstrated that
Epicoccum latusicollum
HGUP191049 and
Setophoma terrestris
HGUP190028 had excellent antagonistic activity. The minimum inhibitory concentration (MIC) test for extracellular metabolites finally indicated that HGUP191049 had lower MIC values and a broader antimicrobial spectrum, compared to HGUP190028. Genomic, non-target metabolomic, and comparative genomic studies were performed to understand the biosynthetic capacity of the screened-out endophytic fungus. Genome sequencing and annotation of HGUP191049 revealed a size of 33.24 megabase pairs (Mbp), with 24 biosynthetic gene clusters (BGCs), where the putative antimicrobial compounds, oxyjavanicin, patulin and squalestatin S1 were encoded by three different BGCs, respectively. In addition, the non-targeted metabolic results demonstrated that the strain contained approximately 120 antimicrobial secondary metabolites and was structurally diverse. Finally, comparative genomics revealed differences in pathogenicity, virulence, and carbohydrate-active enzymes in the genome of
Epicoccum
spp. Moreover, the results of the comparative analyses presumed that
Epicoccum
is a promising source of antimicrobial terpenes, while oxyjavanicin and squalestatin S1 are antimicrobial compounds shared by the genus. In conclusion,
R. roxburghii
and the endophytic HGUP191049 isolated from it are promising sources of broad-spectrum antimicrobial agents.
Epicotripeptin (
), a new cyclic tripeptide along with four known cyclic dipeptides (
-
) and one acetamide derivative (
) were isolated from seagrass-associated endophytic fungus
M13 recovered from ...the Red Sea. Additionally, two new compounds, cyclodidepsipeptide phragamide A (
) and trioxobutanamide derivative phragamide B (
), together with eight known compounds (
-
), were isolated from plant-derived endophyte
13A collected from a saline lake of Wadi El Natrun depression in the Sahara Desert. The structures of the isolated compounds were determined based on the 1D and 2D NMR spectroscopic data, HRESIMS data, and a comparison with the reported literature. The absolute configurations of
and
were established by advanced Marfey's and Mosher's ester analyses. The antimicrobial screening indicated that seven of the tested compounds exhibited considerable (MIC range of 2.5-5 µg/mL) to moderate (10-20 µg/mL) antibacterial effect against the tested Gram-positive strains and moderate to weak (10-30 µg/mL) antibacterial effect against Gram-negative strains. Most of the compounds exhibited weak or no activity against the tested Gram-negative strains. On the other hand, four of the tested compounds showed considerable antibiofilm effects against biofilm forming Gram-positive and Gram-negative strains.
Rationale Epicoccum tends to be found in grassland and agricultural areas and is a cause of exacerbation of allergic diseases in the summer-autumn period.
Elaeagnus pungens is an ornamental plant used in landscapes and is native to China and Japan. In Nov. 2015, a leaf spot was found on El. pungens in the Sheshan National Forest Park located at ...Shanghai. A fungus was isolated from the margins of the lesions and one isolate, EP8, selected for identification and pathogenicity tests. Morphological characteristics of the fungus were similar to Epicoccum latusicollum. Phylogenetic analysis using concatenated sequences of ITS, LSU, TUB, and RPB2 also showed that isolate EP8 clustered with strains of E. latusicollum, a relationship supported with a high bootstrap value. This report is the first of E. latusicollum causing leaf spot on El. pungens.
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