Fungal Pathogens and Seed Storage in the Dry State

Genomic and morphological characterization of Knufia obscura isolated from the Mars 2020 spacecraft assembly facility

Members of the family Trichomeriaceae, belonging to the Chaetothyriales order and the Ascomycota phylum, are known for their capability to inhabit hostile environments characterized by extreme temperatures, oligotrophic conditions, drought, or presence of toxic compounds. The genus Knufia encompasses many polyextremophilic species. In this report, the genomic and morphological features of the strain FJI-L2-BK-P2 presented, which was isolated from the Mars 2020 mission spacecraft assembly facility located at the Jet Propulsion Laboratory in Pasadena, California. The identification is based on sequence alignment for marker genes, multi-locus sequence analysis, and whole genome sequence phylogeny. The morphological features were studied using a diverse range of microscopic techniques (bright field, phase contrast, differential interference contrast and scanning electron microscopy). The phylogenetic marker genes of the strain FJI-L2-BK-P2 exhibited highest similarities with type strain of Knufia obscura (CBS 148926T) that was isolated from the gas tank of a car in Italy. To validate the species identity, whole genomes of both strains (FJI-L2-BK-P2 and CBS 148926T) were sequenced, annotated, and strain FJI-L2-BK-P2 was confirmed as K. obscura. The morphological analysis and description of the genomic characteristics of K. obscura FJI-L2-BK-P2 may contribute to refining the taxonomy of Knufia species. Key morphological features are reported in this K. obscura strain, resembling microsclerotia and chlamydospore-like propagules. These features known to be characteristic features in black fungi which could potentially facilitate their adaptation to harsh environments.

Good things come to those who wait - a 42-year study challenges 'trade-off' theories

This article is a Commentary on Chen et al. (2024), 241: 623–631.

Purification and evaluation of 2, 4-di-tert butylphenol (DTBP) as a biocontrol agent against phyto-pathogenic fungi

A fungal strain, Marasmiellus sp (PUK64), isolated from the mangrove forests in Muthupet, Tamil Nadu, East coast of India, along with others were screened for the search of potent bioactive compounds. A phenolic compound, 2,4-di-tert-butylphenol (DTBP), was isolated from the most promising strain PUK64 and its chemical structure was ascertained. DTBP demonstrated remarkable antifungal activity against the phytopathogenic fungi Aspergillus oryzae, Curvularia lunata and Fusarium verticillioides. In an in-vitro experimental setup, DTBP suppressed the growth of all three fungi, among which F. verticillioides was found to be highly susceptible. This effect relates with the inhibition of spore germination and hyphal growth that we observed. DTBP showed high affinity with the F. verticillioides's β-tubulin protein (determined by ligand-protein docking) as compared to the standard fungicide carbendazim (CBZ). Molecular docking and simulation studies of DTBP with target β-tubulin further confirmed the potential of β-tubulin binding in F. verticillioides. To our knowledge, this is the first report on DTBP-mediated biocontrol of phytopathogenic fungi, produced by Marasmiellus sp. PUK64 that can be potent inhibitor of β-tubulin protein of F. verticillioides.

Bruchus rufimanus Boh. Effect on Broad Bean Seed Quality and the Infection Level of Seed-Borne Fungal Pathogens

Broad bean weevil (Bruchus rufimanus Boh.) is considered an economically important insect pest of the broad bean crop. Its damage starts when larvae burrow into the seed and feed on endosperm or kill the embryo, thus the seed cannot germinate. The microbiological quality and consumer safety of broad bean may be compromised by holes. This study was performed during 2018-2020 to estimate the effect of seed damage by B. rufimanus on seed quality, germination rate and seedling growth, and on the incidence of seed-borne fungal pathogens. Broad bean seeds were collected and classified as damaged by B. rufimanus or non-damaged. There was a relationship between broad bean weevil damage and an increase in fungal contamination. Results showed that germination decreased from 97.2% for non-damaged seeds to 81.4% for the seeds with B. rufimanus damage. Seven fungal genera were identified: Fusarium spp., Alternaria spp., Aspergillus spp., Penicillium spp., Cladosporium spp., Mucor spp. and Botrytis spp. The most common fungal genus was Cladosporium spp. Our research shows that B. rufimanus negatively affects the germination of its host's seeds and decreases the development of seedlings.

Impact of green antioxidants on decreasing the aflatoxins percentage in peanut oil seed (Arachis hypogaea L.) during storage

The present study conducted an experimental investigation to impede the degradation of peanut (Arachis hypogaea L.) seeds and enhance their quality while being stored. The efficacy of eco-friendly chemicals such as ascorbic acid, salicylic acid, acetic acid, and propionic acid in seed preservation was evaluated over a period of six months. After a period of six months of storage in a greenhouse, an examination was conducted on peanut seeds that had undergone treatment. Rhizoctonia was observed after Cephalothorax, whereas Aspergillus, Fusarium, and Penicillium were the prevailing fungi throughout the storage period. The optimal outcomes were obtained from the conversion of acetic acid to propionic acid. The study observed a decline in seed oil, protein, carbohydrates, germination percentage, energy, index, length, vigour index, dead and rotten seeds, rotted seedlings, and surviving healthy seedlings, with an increase in storage duration ranging from zero to six months. The application of 100% propionic acid to peanut seeds throughout the storage duration resulted in decreased occurrences of deceased seeds, decaying seeds, and deteriorated seedlings. Peanut seeds that underwent treatment with green chemical agents of moderate and high intensity were found to be free of aflatoxin B1. The highest levels of chlorophylls a and b, carotenoids, and total phenols were observed in seeds stored in greenhouses and treated with 100% propionic acid and acetic acid extract. The application of propionic acid 100%, acetic acid 100%, salicylic acid 4 g/l and ascorbic acid 4 g/l proved to be the most effective treatments for peanut seeds, exhibiting the lowest total aflatoxin level of 0.40. The correlation coefficient between shoot fresh weight and shoot dry weight was found to be 0.99, whereas the correlation coefficient between root dry weight and shoot length was 0.67. The seed chemical analysis, seedling characteristics, and germination characteristics were subjected to clustering analysis, resulting in the formation of two distinct groups. The first group consisted of germination percentage and energy levels across all time points (0-6 months), while the second group consisted of the remaining characteristics. The findings of this research propose the utilisation of 100% propionic acid as a viable method for preserving peanut seeds and preventing their deterioration during storage. The application of 100% acetic acid has been found to be effective in enhancing the quality of seeds and minimising losses.