ABSTRACT
Gliocladium fungi have been known to produce compounds with potent antibiotic activity belonging to the class of the Epidithiodiketopiperazines, including the metabolites gliotoxin, viridin, gliovirin and viridiol. These compounds show inhibitory effect against a wide range of microorganisms, and are particularly toxic to fungal pathogens. The present work aimed to apply the mutagenesis technique on two locally isolated Gliocladium species [G. roseei or G. virens] to enhance their biocontrol abilities against F. oxysporum and P. ultimum the causal fungi of root-rot and wilt diseases in pea plants, through increasing the antifungal metabolite [antibiotics] production than the original wild type parents. After y-irradiation of the mycoparasitic strains of G. virens and G. roseei mutant strains were isolated which were benomyl-tolerant and longer than that of the wild types. Four of the mutants characterized, [gamma-GrM8 and gamma-GrM10] and [gamma-GvM11 and gamma-GvM12] that are derived from G. virens and G. roseei, respectively, had higher levels of the antibiotics; gliovirin, viridiol, gliotoxin and viridin. High Performance Liquid Chromatography [HPLC] analysis indicated each individual antibiotic to be more abundant in the selected mutants than in the wild types. The selected mutants were more resistant to the fungicide benomyl and highly producers of the metabolites [antibiotics] than their wild type parents possibly due to a pleiotropic effect of the altered permeability. Studies on mutual antagonism in vitro showed that selected mutants significantly reduced that of P.ultimum and F.oxysporum growth and inhibition by its culture filtrates. When applied to pea seeds sown in artificial [pots] and natural [field] infection, the selected mutants significantly suppressed root-rot and wilt pathogens [P. ultimum and F. oxysporum] and reduced diseases incidence in rhizosphere compared with wild type parents