Assessment of filamentous fungal diversity using classic and molecular approaches: case study – Mediterranean ecosystem

Biomolecules from Chaetomium globosum Possessing Antimicrobial Compounds Potentially Inhibits Fusarium Wilt of Tomato

Wilt disease caused by Fusarium solani, a soil-borne plant pathogenic fungus, is a serious disease in tomato causing economic losses. In the present study, among the nine isolates of Chaetomium globosum Kunze (Chg1-Chg9), screened against F. solani No. Fs-1, Chg2 exhibited the maximum inhibition (49.2 %), followed by the isolates Chg6 (47.4%) and Chg1 (46.3%) in dual culture. Further, the crude secondary metabolites from these three isolates showed maximum reduction of the mycelial growth of Fs-1 compared to control. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the metabolites from Chg2 revealed the presence of major compounds, viz., benzothiazole, 2-(2-hydroxyethylthio) (7.51%); 9,12,15- octadecatrienoic acid, 2,3-bis[(trimethylsilyl)oxy] propyl ester (3.13%); and hexadecanoic acid, 1- (hydroxymethyl)-1,2-ethanediyl ester (2.69%). Fourier transform infrared (FTIR) spectroscopy revealed the presence of alcohol, secondary amine, aliphatic primary amine, carboxylic acid, allene, conjugated ketone, imine/oxime, sulphate, and halo compound groups with a weak to strong range of intensity. Pure compound of benzothiazole @ 5000 ppm exhibited higher antagonistic activity of Fs-1which decreased at lower concentration. In pot culture experiment, dipping tomato seedlings cv. PKM1 in 2% ethyl acetate-fractionated biomolecules of Chg2 recorded a minimum disease incidence of 20.0%, whereas seedlings dipped in the culture filtrate of Chg2 showed a disease incidence of 26.6% compared to control (86.6%). Besides, these seedlings treated with the culture filtrate showed the highest plant height of 37.68 cm and the maximum number of leaves and flowers (39.6 and 5.48, respectively), followed by those treated with the biomolecules of Chg2 (C. globosum) and the culture filtrate of T. asperellum. The results revealed that the antifungal efficacy of C. globosum Chg2 is due to the presence of antimicrobial metabolites including benzothiazole. Exploring the use of this novel antifungal compound in the management of plant diseases is highly warranted.

Foliar fungi of the enigmatic desert plant Welwitschia mirabilis show little adaptation to their unique host plant

Foliar fungi, especially endophytic fungi, constitute an important part of the microbiome of plants. Yet little is known about the composition of these communities. In this study, we isolated fungi from leaf tissues of the desert plant Welwitschia mirabilis to determine the culturable diversity of the foliar fungal community. The isolated fungal taxa, which grouped into 17 distinct lineages, were identified by sequencing elongation factor 1 alpha, beta tubulin 1, beta tubulin 2 and the internal transcribed spacer region. The culturable community was mainly composed of cosmopolitan fungal genera despite the unique taxonomic position of the plant and its geographic isolation. To test for endemism in two of the common fungal genera, Alternaria and Aureobasidium, we built haplotype networks using a global data set. Even this broad data set showed little evidence for specialisation within this unique host or its geographical location. The data suggest that the culturable members of communities of leaf-associated fungi in habitats with little plant coverage, such as the Namib Desert, are mainly established by long-distance aerially distributed fungal inocula and few of these taxa co-evolve with the host within the habitat.