The effect of biocontrol agents consortia against Rhizoctonia root rot of common bean Phaseolus vulgaris

In recent years, biological control has become a promising and ecologically friendly alternative to chemical control in the management of soil-borne plant diseases and several biological control agents have been introduced as potential bio-fungicides. The aim of this study was to investigate different biological control agent consortia against Rhizoctonia solani root rot disease of common bean. Bacillus pumilus INR7, Trichoderma harzianum and Rhizophagus intraradices were used individually or in combination. There were two application simultaneous application of biocontrol agents with the plant pathogen, and pre-inoculation of biocontrol agents one month before the pathogen. Treatments containing B.pumilus INR7 were the best treatments for suppression of the disease in the simultaneous application method, where B. pumilus INR7 T. harzianumreduced the disease up to 54%. However, in pre-inoculation method T. harzianum alone was the only treatment that reduced disease severity up to 49% compared to the infected control; other treatments did not haveany significant effect on disease severity. In current study, combination of T. harzianum and R. intraradices was unable to decrease disease severity and improve plant growth. This phenomenon was common in both simultaneous and pre-inoculation experiments. However, results showed that B. pumilus INR7 and R. intraradices were compatible with each other. Their combination not only decreased the disease, but also improved the dry weight of common bean in both application methods. Our results revealed that B. pumilus INR7 had positive interaction with T. harzianum. This combination increased their ability to suppress root rot disease and improve plant health, significantly. Overall, combinations of biocontrol agents have good potential to be applied in modern agriculture, but such combinations need to be checkedin advance for their compatibility in greenhouse and field experiments.