Optimization of IAA production by endophytic Bacillus spp. from Vigna radiata for their potential use as plant growth promoters

Endophytic bacteria isolated from nodules of Vigna radiata were screened for indole acetic acid (IAA) production. Three isolates MBN3, MJHN1 and MJHN10, molecularly identified as Bacillus aryabhattai (MF693121.1), B. megaterium (MF693120.1) and B. cereus (MF693119.1) were producing significantly high amount of IAA. Production parameters viz. L-tryptophan concentration, incubation time, carbon and nitrogen sources were optimized. The study revealed the presence of trp-dependent pathway for IAA production in the isolates. All of them gave maximum production with yeast extract as nitrogen source but variation in preference for carbon sources was observed. The invitro application of bacterial isolates on plant roots resulted in increase in root length as well as number of lateral roots. These results confirm the occurrence of Bacillus as predominant non-rhizobial endophytic genera in summer season crop and its potential as plant root growth promoter.