Biocontrol Prospects of Pseudomonas fluorescens AS15 Against Banded Leaf and Sheath Blight Disease of Maize Under Field Condition in Conducive Soil

摘要

Banded leaf and sheath blight (BL&SB) disease of maize caused by Rhizoctonia solani is widespread in humid Terai region of Western Himalayas and leads to 11-40% yield loss in maize. Pseudomonas fluorescens AS15 is an ideal antagonist against BL&SB pathogen. Disease severity is reduced when population of AS15 reaches threshold level 5.3 x 10(5) CFU g(-1) in soil at 45 days after inoculation. It is metabolically versatile and utilizes various carbohydrates and nitrogen sources of plants root exudates. Application of P. fluorescens AS15 in conducive soil reduced disease incidence and disease severity and increased grain yield to 33.4%, 46.8% and 8.4%, respectively, during June 2014 field trial. The reduction in disease incidence (18.1%) and disease severity (35.6%) along with the increase in yield (8.1%) was also observed in June 2015 trial carried out in the same fields without further application of antagonistic bacteria. The results clearly demonstrate biocontrol efficacy and successful rhizospheric colonization of P. fluorescens AS15 in natural conditions.