Management of bacterial wilt (Ralstonia solanacearum) of brinjal using Bacillus cereus, Trichoderma harzianum and Calotropis gigantea consortia in Bangladesh

Abstract

Background: Bacterial wilt caused by Ralstonia solanacearum is a devastating disease of brinjal in Bangladesh. The study was targeted to evaluate the bacterial wilt management ability of microbial consortia composed of isolated and identified native Bacillus cereus, Trichoderma harzianum and Calotropis gigantea for the first time in Bangladesh. Results: Twenty bacterial strains were isolated from the rhizosphere of the brinjal plant following serial dilution method. Among the strains, HSTUB 17 showed maximum zone of inhibition (1.5 ± 0.1 cm) against R. solanacearum in the dual culture method. Molecular characterization using 16 s rRNA partial coding sequence revealed HSTUB 17 as B. cereus. Consortia composed with the identified B. cereus HSTUB 17 (108 CFU ml−1 @ 5 ml/plant), previously isolated T. harzianum (@5 mm size of four mycelial disk/plant) and aqueous leaf extracts of C. gigantea (1:1, w/v basis @ 40 ml/plant) were applied in the root zone following soil drenching method and found to reduce bacterial wilt incidence by 74.87, 66.67 and 66.67% at 30, 50 and 70 days after transplanting, respectively, in comparison with plants received only R. solanacearum (108 CFU ml−1 @ 5 ml/plant). The single application of B. cereus HSTUB 17, T. harzianum and C. gigantea also minimized wilt incidence by 21.16–37.34, 33.33 and 21.48–28.14%, respectively, on all the days of observations. The consortia of B. cereus HSTUB 17, T. harzianum and C. gigantea also resulted in maximum plant height (56.67 cm), the number of branches/plants (10.33), the number of fruits/plants (8.33) and fruit yield (25.56 ton/ha) in comparison with the plant exposed to R. solanacearum only. Conclusion: The findings of the study revealed the potentiality of consortia composed of B. cereus HSTUB 17, T. harzianum and C. gigantea for the eco-friendly management of bacterial wilt of brinjal for the first time in Bangladesh.