Chitin-supplemented foliar application of chitinolytic Bacillus cereus reduces severity of Botrytis gray mold disease in chickpea under controlled conditions.

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.