Biocontrol potential of salinity tolerant mutants of Trichoderma harzianum against Fusarium oxysporum causing tomato wilt disease [electronic resource].

Includes references.

This work aims to apply γ- irradiation in a breeding program of Trichoderma harzianum to enhance its biocontrol ability against F. oxysporum through increasing their production of antifungal metabolites (i.e., hydrolytic enzymes,antibiotics and total phenols) under salt stress conditions. Exposing a wild-type culture of the mycoparasitic fungus T. harzianum to gamma irradiation induced two stable salt-tolerant mutants (Th50M6 & Th50M11).Under saline conditions, both mutants greatly surpassed their wild type strain in growth rate, sporulation and biological proficiency against Fusarium oxysporum, the causal agent of tomato wilt disease. Tolerant T. harzianum mutants detained a capability to grow and convinced sporulation in growth media containing up to 69 mM NaCl. In comparison with their parent strain, characterization of both mutants confirmed that they have reinforced contents of proline and hydroxyproline, relatively higher sodium content compared to potassium, calcium or magnesium contents, higher level of total phenols. Data also showed that mutants produce certain active metabolites including; extracellular-enzymes of chitinases, cellulases, β-galactosidases, as well as, some antibiotics i.e., trichodermin, gliotoxin and gliovirin. Trichoderma mutants significantly reduced wilt disease incidence and improved yield and mineral contents of tomato plants under both saline and nonsaline soil conditions, as well as, under infested and natural conditions. T. harzianum mutants were also more efficient in dropping the F. oxysporum growth in rhizosphere compared to the wild type strain. Population density of both mutants in rhizosphere far exceeded those of T. harzianum wild type strain.

Summary in Arabic.

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