ملخص
Abstract
This study was conducted to evaluate in vitro and in vivo antagonistic activities of five Trichoderma isolates; three local (Lib1, Lib2, Lib3) and two commercial (T22, Tp1) against mycelium radial growth and sclerotia formation of the plant pathogenic fungus Sclerotinia sclerotiorum, and its effect on seed germination and infection of pea (Pisum sativum L.) seeds. All experiments were conducted at two growth temperatures, 20 and 25˚C. Microscopic interactions of Trichoderma isolates and host fungus were performed by slide culture technique. Two concentrations (10, 20%) of Trichoderma culture filtrate were tested for their effect on mycelium growth. All Trichoderma isolates were able to inhibit the growth of the fungal pathogen, although, variations were observed among tested isolates in rate and mechanisms of inhibition. At 25⁰C Lib2 showed the highest rate of mycelium growth and spore formation. In mycoparasitism, the inhibition rate was 55% for Lib3 and 45% for Lib1. Whereas for indirect interactions; significant inhibition of mycelium radial growth was observed for Lib1 and Tp1 with a percentage of 28.5 and 26.4 respectively. Overgrowth was also reported on the colonies of S. sclerotiorum by Lib2 and T22, and these two isolates showed remarkable inhibition of sclerotia formation with a percentage rate of 91. The effect of culture filtrate of Trichoderma isolates was dose dependent, 20% concentration of culture filtrate lowered the rate of radial growth of S. sclerotiorum by 53% for Lib1 and 47.2% for Tp1, while lower inhibition of Sclerotinia radial growth was reported for 10% concentration of culture filtrate with a percentage of 45 for Lib1 and 34 for Tp1. At 20⁰C 10% and 20% culture filtrate exhibited lower effect on mycelium radial growth of Sclerotinia. Seed germination of peas (local variety) was enhanced by Trichoderma treatment. Increased rate of seed germination was reported by 96.6% for Lib1, Lib2 and 80% for Lib3 and 76% for Tp1, lower inhibitory effect was reported for T22 by 43%. Seed treated with Trichoderma isolates exhibited low rate of seedlings infection by S. sclerotiorum.