G K Kishore1, S Pande. 1. Department of Pathology, International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502 324, India. krishnakishore_gali@yahoo.co.in
Abstract
AIM: To identify and evaluate chitinolytic bacteria for control of Botrytis gray mold (BGM), a devastating disease in chickpea. METHODS AND RESULTS: Two antifungal bacterial isolates, chitinolytic Bacillus cereus CRS 7 and nonchitinolytic Pseudomonas fluorescens CRS 31, from the rhizosphere of chickpea, were applied as a prophylactic foliar spray and evaluated for control of BGM. In a controlled environment, the two isolates reduced the severity of BGM on the susceptible cv. JG 62 to 6.0 and 5.6, respectively, compared with 9.0 in the control, measured on a 1-9 rating scale. Supplementation of the foliar application of CRS 7 with 0.5% and 1.0% colloidal chitin reduced BGM severity to 4.4 and 4.1 respectively, while chitin-supplemented application of CRS 31 was similar to CRS 31 applied alone. Partially purified 47-kDa chitinase from the cell-free culture filtrate of CRS 7 at 20 and 40 mug protein ml(-1) (enzyme activity 3.1 units ml(-1)) inhibited the germination and lysed the conidia of Botrytis cinerea, and as a prophylactic foliar spray reduced BGM severity to 5.4 and 4.8, respectively. CONCLUSION: Chitin supplementation improved the biocontrol of the foliar disease BGM by chitinolytic bacterium. Disease control with partially purified chitinase of CRS 7 supported the major role of chitinolysis in improved control of BGM. SIGNIFICANCE AND IMPACT OF THE STUDY: Enhanced control of BGM by chitin-supplemented application of CRS 7 is of significant in view of the frequent inconsistency in biocontrol of foliar diseases. This study supports further attempts on chitinolysis-based biocontrol methods for foliar disease biocontrol.
AIM: To identify and evaluate chitinolytic bacteria for control of Botrytis gray mold (BGM), a devastating disease in chickpea. METHODS AND RESULTS: Two antifungal bacterial isolates, chitinolytic Bacillus cereusCRS 7 and nonchitinolytic Pseudomonas fluorescensCRS 31, from the rhizosphere of chickpea, were applied as a prophylactic foliar spray and evaluated for control of BGM. In a controlled environment, the two isolates reduced the severity of BGM on the susceptible cv. JG 62 to 6.0 and 5.6, respectively, compared with 9.0 in the control, measured on a 1-9 rating scale. Supplementation of the foliar application of CRS 7 with 0.5% and 1.0% colloidal chitin reduced BGM severity to 4.4 and 4.1 respectively, while chitin-supplemented application of CRS 31 was similar to CRS 31 applied alone. Partially purified 47-kDa chitinase from the cell-free culture filtrate of CRS 7 at 20 and 40 mug protein ml(-1) (enzyme activity 3.1 units ml(-1)) inhibited the germination and lysed the conidia of Botrytis cinerea, and as a prophylactic foliar spray reduced BGM severity to 5.4 and 4.8, respectively. CONCLUSION:Chitin supplementation improved the biocontrol of the foliar disease BGM by chitinolytic bacterium. Disease control with partially purified chitinase of CRS 7 supported the major role of chitinolysis in improved control of BGM. SIGNIFICANCE AND IMPACT OF THE STUDY: Enhanced control of BGM by chitin-supplemented application of CRS 7 is of significant in view of the frequent inconsistency in biocontrol of foliar diseases. This study supports further attempts on chitinolysis-based biocontrol methods for foliar disease biocontrol.