Efficacy of rhizospheric Bacillus spp. for growth promotion in Theobroma cacao L. seedlings
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Date
2011
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Abstract
Cocoa (Theobroma cacao L.) trees harbour a diverse microbial communities of epiphytic, rhizospheric and endophytic organisms, many possessing plant growth promoting abilities. Since plant growth promoting rhizobacteria (PGPR) can significantly promote plant health and sustain agriculture by a variety of mechanisms, their potential for use in cocoa crop can be exploited. PGPR based products with strains of Bacillus are more successful in the field due to the fact that they produce spores which offer them ability to tolerate wide range of biotic and abiotic stress. This paper highlights the screening of selected Bacillus spp., isolated from the rhizosphere of cocoa growing in different agro-climatic and soil types in Kerala, Karnataka, Tamil Nadu and Andhra Pradesh, on the growth parameters of cocoa seedlings when grown in polybags. Statistically significant increase (P = 0.05) over the control was observed in the tested parameters such as total seedling length (up to 37 %), total fresh weight (up to 73 %) and total dry weight (up to 56 %) of cocoa seedlings when they were inoculated with Bacillus spp. The overall improvement in seedling vigour through a significant increase in various growth parameters indicated that the Bacillus strains (Bacillus sp. ASB3, ASB12, CSB8, CSB16 and CSB17) had positive and effective plant growth promoting ability on cocoa seedlings. In addition to its plant growth promotion abilities the potential PGPR Bacillus spp. (isolates CSB8, CSB16, CSB17 and ASB12) also showed high abiotic stress tolerance, growing at higher temperatures (> 50 0C) and salt concentrations (10 % NaCl). These PGPRs were identified according to Bergey’s Manual of Determinative Bacteriology and confirmed by Biolog® GEN III microplate identification system. The results of this study points to the potential of rhizospheric Bacillus spp. to enhance growth and vigour of cocoa seedlings when grown in polybags.
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Keywords
Bacillus spp., plant growth promoting (PGP) traits, Theobroma cacao
Citation
Journal of Plantation Crops, 2011, 39 (1): 19-25