Biological control of Fusarium oxysporum f. sp. ciceris, the causal agent of the fusarial yellowing and wilting of chickpea by mixtures of some microbial agents

Fusarial yellowing and wilting caused by Fusarium oxysporum f. sp ciceris is one of the most important diseases of chickpea. The effects of separate and combined applications of Trichoderma harzianum T33, Pseudomonas putida RUP1 and Rhizophagus intraradices were evaluated on suppression of this disease and improving growth factors of chickpea in the presence of the pathogen. The experiments were conducted in greenhouse in a completely randomized design with four replications. Except for the triple treatment (consisting of three biocontrol agents), all treatments significantly reduced the yellowing symptoms of foliage and vascular necrosis caused by the pathogen and also increased the roots volume and dry weight and shoot dry weight. Also, in addition to the triple treatment and the combined treatment of R. intraradices and T. harzianum T33, other biocontrol treatments increased the fresh weight of roots and shoots. R. intraradices was able to colonize 60% and 74% of chickpea roots in the presence and absence of the pathogen, respectively. Despite their compatibility, the dual combination of biocontrol strains did not have a synergistic effect in improving biocontrol efficiency and chickpea growth promoting, and the triple combination of these factors did not have biocontrol capability or plant growth promoting. This study showed that the combination of biocontrol agents is not always synergistic or efficient.