The Profile Change Of Defense Pathways In Phaseouls Vulgaris L. By Biochemical And Molecular Interactions Of Trichoderma Harzianum Transformants Overexpressing A Chimeric Chitinase

Trichoderma species as biocontrol agents protect plants against several pathogens via multiple mechanisms. This study was aimed to evaluate the in vitro biocontrol activities and, as well as in vivo induction of systemic resistance of Phaseolus vulgaris L. by two Trichoderma harzianum transformants overexpressing a chimeric chitinase42 with chitin binding domain (T13 and T15) and wild-type (Tw) strain with and without Rhizoctonia solani. In order to achieve this goal, T. harzianum strains were compared in vitro for their potential to antagonize activity against R. solani. Also, the expression of biocontrol-associated genes (chit42 and qid74) and the volatile compounds (VOCs) profile with biocontrol activity was analyzed from T. harzianum strains. The real-time PCR was used to measure the expression of defense-related genes involved in systemic acquired resistance (SAR) and induced systemic resistance (ISR) pathways. The results showed that recombinant strains T15 (92%) and T13 (85%) had the higher inhibitory effects against R. solani compared to the Tw strain. Also, gene expression analysis of T. harzianum revealed the up-regulation of biocontrol-associated genes in recombinant strains. Analysis of VOCs from three T. harzianum strains identified a total of twenty-two compounds, including five that were produced by all of them .VOCs analysis of recombinant strains revealed the production of compounds, like caryophyllene oxide, 2-methyl-1-butanol, alpha-farnesene, and beta-bisabolene. These compounds had been reported to induce plant defensive reactions against stress. Inoculation of plants with T13 and specially T15 strains, restricted the R. solani growth. Treatment of bean plants with recombinant strains led to increase in protection mechanisms including enhanced defense enzymes activity and higher expression of defense-related genes, as compared with Tw. The ability of recombinant strains to have better colonization within the soil and the root surface, describes its positive effects on defense mechanisms against R. solani.