Biological control of growth promoting rhizobacteria against verticillium wilt of pepper plant

Verticillium dahliae is one of the most important soil pathogens, causing verticillium wilt. It is well known that the use of chemical products against this pathogen is not without side effects on the environment. In this regard, the present study was aimed to search for antagonistic rhizobacteria as an alternative of biological control against this causal agent. A total of 162 isolates were screened for their antagonistic activity according to the “double layer” and the “well diffusion” methods. Three of them (RS11, SF82 and ZO4), were subsequently selected as biological control agent (BCAs) according to their efficiency and were identified by 16S rRNA sequencing and Biolog microplate GEN III as Bacillus spp. Using 10 different lipopeptide gene primers, PCR reactions only revealed the involvement of genes responsible for iturins (ituA, ituD, ituC), bacillomycin (bmyA) and Bacilysin (bacA / B-F, bacA / B-R) biosynthesis. The Plant Growth Promoting Rhizobacteria traits [enzymatic activities, phytohormones production] of the three BCAs were also studied in vitro then on pepper plant (Capsicum annuum L.), indicating that Bacillus subtilis ZO4 was the most effective, enhancing leaf, stem and root growth comparing to the control.