Culturable Diversity of Endophytic and Rhizoplane Colonizing Bacteria of Indian Mustard (Brassica juncea (L.) Czern & Coss), Affected by Soil Types and Assessment of Plant Growth Promoting Attributes

Microbial community in the rhizosphere of plant significantly influences growth and development of a plant. As the soil vary in microbial composition due to interaction of soil with plant roots and its exudates, the role of soil in shaping microbial diversity of a crop rhizosphere is least studied. In present study, Mustard (Brassica juncea cv Pusa Mehak) was grown in three different soil viz. Vertisols, Inceptisols and Alfisols, and the bacteria were isolated form root tissues and rhizoplane to study their plant growth promoting (PGP) attributes and diversity using BOX-Polymerase chain reaction (PCR) fingerprinting technique, as influenced by soil types. Form threes soil orders, total 37 isolates were obtained of which, 19 could grow on nitrogen free medium, 6 solubilized P from tricalcium phosphate, 2 isolate solubilized potassium from glauconite and 8 had zinc solubilizing ability with the highest zinc solubilization index of 3.84 by isolate VRB-7. Based on the fingerprint analysis, differences occurred in the endophytic bacteria of same host grown in different soil types suggesting influence of soil types in colonization of microbes in rhizoplane and endorhizosphere. The common organisms obtained from host grown in different soil types indicating host genotype driven assembly of bacteria. Similarity in the isolates on rhizoplane and endorhizosphere indicated endophytic colonization of the isolates capable of firmly adhering to the rhizoplane. The findings of this study will help in formulation of crop specific bioinoculant for specific soil types and edaphic properties.