Deciphering the Role of Bacillus subtilis var. amyloliquefaciens in the Management of Late Blight Pathogen of Potato, Phytophthora infestans

Abstract

An oomycete fungus Phytophthora infestans (Mont.) de Bary, is an incitant of destructive late blight disease on potato, causes severe yield loss worldwide. A study was undertaken for the management of the diseases by using the antagonistic bacterium. Twenty-five isolates of antagonistic bacteria were collected from various parts of Tamil Nadu from rhizospheric soils of Solanaceous crops potato, tomato and Solanum nigrum. These isolates were tested in vitro for its efficacy against P. infestans along with the FZB 24 strain of Bacillus subtilis var. amyloliquefaciens of M/S. Novozymes South Asia Ltd. B. subtilis var. amyloliquefaciens (FZB 24) showed a maximum inhibition of 35.56% against P. infestans. Based on this initial screening, the FZB 24 was used for further investigation under glass house and field conditions for the late blight disease management in potato. The glasshouse studies revealed that the application of corn flour formulation of B. subtilis var. amyloliquefaciens (FZB 24) as foliar spray @ 0.2% at 7 days interval for six times had shown significant reduction of 49.7% late blight severity over control. In addition, the potato plants from the above treatment showed higher activity of defence related enzymes such as peroxidase, polyphenol oxidase and phenylalanine ammonia lyase, which lead to higher accumulation of total phenols in comparison to untreated control plants. Under field conditions, B. subtilis var. amyloliquefaciens (FZB 24) treated potato plots registered significantly less severity of late blight disease which recorded higher tuber yield of 15.5 t/ha as against 9.4 t/ha in control.