Abstract

Co-cultivation is one of the significant ways to improve the efficacy of biocontrol agents. In the present study, the role of Vel1 on the sporulation, secondary metabolism, mycoparasitism and disease control of Trichoderma atroviride and its influence on B. amyloliquefaciens macrolactin and difficidin gene expressions during co-cultivation have been investigated through the knockout and overexpression of Vel 1 gene. Under nutrient stress conditions the T. atroviride Vel1 knockout ( T23ΔVel1) exhibited early chlamydospore differentiation, while wild type and over expression strains formed more chlamydospores under nutrient-rich conditions. The differential expression of genes related to sporulation, secondary metabolism, mycoparasitism, and disease control was upregulated by the Vel1 over-expression ( T23OVel1 ), and co-cultivations (T23 + BA and T23OVel1  + BA). The expression of these genes was impaired by the deletion of Vel1 gene and co-culture of B. amyloliquefaciens and T23ΔVel1 strains. Interestingly, macrolactin and difficidin genes of B. amyloliquefaciens were downregulated during co-cultivation with T23OVel1 and upregulated during co-cultivation with T23ΔVel1 strains. The mycoparasitism, plant growth and bio-control activity of T23 + BA and T23OVel1  + BA were superior than other treatments. The T23ΔVel1 showed reduced activity of mycoparasitism, plant growth and biocontrol, but it was increased by the co-culture ( T23ΔVel1  + BA) due to the enhanced activity of B. amyloliquefaciens . The results infer that Vel1 of T. atroviride is involved in sporulation, mycoparasitism, disease control and secondary metabolite production. Further, it confirmed that Vel1 downregulates macrolactin and difficidin gene expression of B. amyloliquefaciens and thereby it regulates the compatibility between the T. atroviride and B. amylolique