Biological control of Fusarium root rot of bean with two Trichoderma species and Pseudomonas fluorescens

Fusarium root rot with damage reported up to 85% of the crop yield, caused by Fusarium solani f. sp. phaseoli, is one of the most important bean diseases in the world. Biological control is a healthy and environmentally friendly way to manage this soil-borne disease.

Bean farms in Kohgiluyeh and Boyer-Ahmad Province were visited and the rotten roots of diseased plants were sampled. Two isolates of the pathogen were isolated, purified and identified. The pathogenicity of these two isolates was tested on two bean varieties Drakhshan and Pak under greenhouse conditions. The colony growth inhibition rate of the hypervirulant isolate of the pathogen was assessed by 14 native isolates of Trichoderma harzianum, four isolates of Trichoderma virens, two isolates of Trichoderma atroviridae, and five native isolates of Pseudomonas florescens and P. florescens CHAO with hyperparasitic ability and production of antibiotics in vitro. Finally, the effect of four superior T. harzianum isolates, one T. atroviridae isolate and two P. florescens isolates on disease severity were examined in a completely randomized design in the greenhouse.

All isolates of three species of Trichoderma had the ability to hyperparasite and destroy pathogenic hyphae. Four T. harzianum isolates showed a more significant ability to produce non-volatile and volatile antibiotic materials. All treatments significantly reduced the disease severity, but a T. harzianum isolate was more effective in vivo.

Fusarium root rot is also found in bean fields in southwestern Iran. Native isolates of T. harzianum, T. virens and T. atroviridae have the hyperparasitic ability on the pathogen. These fungi and isolates of P. florescens have the ability to inhibit the growth of the pathogen colony by producing antibiotic substances. Isolates of Trichoderma harzianum, T. atroviridae and P. florescens CHAO have the ability to reduce the severity of the disease in vivo.