The effect of some probiotic bacteria and different methods of their application in biological control of chickpea ascochyta blight disease

Chickpea ascochya blight caused by the fungus Ascochyta rabiei, reduces the yield and quality of chickpea (Cicer arietinum) around the world. The biocontrol potential of 12 bacterial probiotics from genera Alcaligenes, Arthrobacter, Bacillus, Delftia, Lysinibacillus, Pseudomonas and Stenotrophomonas was investigated against A. rabiei. In dual-culture and volatile compounds production tests, all probiotic bacteria (except one Bacillus isolate) significantly inhibited the mycelial growth of pathogen. The highest inhibition in these tests was obtained by Bacillus subtilis BS (57.84%) and Alcaligenes faecalis 1624 (72.5%), respectively. Six probiotic bacteria with the best inhibitory results in the laboratory were selected and their biocontrol and growth stimulation (fresh and dry weight) effects were evaluated in the presence of the pathogen using seed application and foliar spraying methods in the greenhouse. In comparison to the disease control, all selected probiotics in both application methods significantly reduced the disease index and increased the growth factors of chickpea plants (except for the seed treatment of A. faecalis 1624 which did not increase the fresh weight of shoots). Foliar application of B. subtilis BS, with large difference to other treatments, was the most effective treatment in reducing the disease index (63.80%) and increasing the growth factors of chickpea. According to the results of this study, foliar application of B. subtilis BS had great potential in biocontrol of ascochya blight and growth promotion of chickpea. Therefore, if its effectiveness is confirmed by field studies, it could be used in integrated management of this disease in the future.