Induced Systemic Resistance in Two Genotypes of <i>Brassica napus</i> (AACC) and <i>Raphanus oleracea</i> (RRCC) by <i>Trichoderma</i> Isolates against <i>Sclerotinia sclerotiorum</i>

Abstract

Two different species, Trichoderma viride TV10 and Trichoderma harzianum TH12 from 30 Trichoderma isolates were selected out based on their high growth inhibition of the phytopathogen Sclerotinia sclerotiorum (Lib) de Bary, which reached 84.44% and 100%, respectively. Their untreated culture filtrates (CF) and culture filtrates treated with heat (CFH) also were tested for growth inhibition of the pathogen in potato dextrose agar (PDA). Morphological and molecular characterisation by internal transcribed spacer (ITS) PCR provided consistent identification of these isolates. The degree of infection and disease index (DI) of S. sclerotiorum were examined in Brassica napus (AACC) and Raphanus alboglabra (RR) and Brassica alboglabra (CC). The results revealed that Raphanus alboglabra showed higher disease resistance than that of B. napus . Biotic elecitors T. harzianum TH12 and T. viride TV10 and their CF and CFH demonstrated the ability to cause induced systemic resistance (ISR) in B. napus and Raphanus alboglabra against sclerotinia stem rot (SSR) disease. Furthermore, a high ability to reduce the degree of infection and DI in B. napus with the biotic elicitors T. harzianum TH12 and T. viride TV10 was observed, with numbers reaching 7.22% to 6.67% and 17.78% to 11.67%, respectively. When CF were used, reached 20.00% to 16.67% and 33.33% to 23.33%, respectively; with CFH, values reached 35.00% to 21.67% and 37.78% to 28.33%, respectively. While in Raphanus alboglabra the degree of infection and DI reached 0.00% and 0.00% with all biotic elicitors treatments. These results show that biotic elicitor treatments significantly (P < 0.05) can increase the fresh and dry weights of both roots and shoots as well as plant height compared with controls. The TH12 treatment in B. napus and Raphanus alboglabra ranked as most effective. This study showed for the first time the ability of genotype Raphanus alboglabra (RRCC) to demonstrate resistance against S. sclerotiorum with or without treatment by biotic elicitors and the ability of genotype B. napus (AACC) to demonstrate resistance to the pathogen after treatment with biotic elicitors.