Bacillus species consortium with tryptophan-dependent and -independent pathways mediated IAA production modulates soil biological properties, growth and yield of wheat

Abstract

Abstract Background and Aims: Operation of both tryptophan-dependent and -independent pathways leading to higher IAA production by certain bacteria is known to beneficially influence plant growth and development. This study aimed to detect the operation of different pathways in bacteria for IAA production and evaluate the PGP (plant growth promoting) potential of the best IAA-producing bacteria in wheat crop. Methods The bacteria isolated from chickpea rhizosphere were screened for IAA production through tryptophan-dependent and independent pathways. The prominent IAA producing bacteria were identified by 16S rRNA gene sequencing and evaluated for their growth promoting, soil and plant nutrient enriching potential in wheat crop (cv. Sujata). Results Out of the 80 bacteria screened, three isolates, KS-14, BEMS-9-1 and BS-2 were found to produce high levels of IAA by operating both the pathways. These isolates were identified as Brevibacillus formosus, Bacillus paramycoides and Bacillus tequilensis, respectively. Evaluation of various combinations of these promising bacteria showed that the consortium of Brevibacillus formosus KS-14 and Bacillus paramycoides BEMS-9-1 along with a 50% recommended dose of fertilizer (RDF) not only significantly improved the morphological and physiological traits of wheat including yield and grain micronutrient loading, mediated through enhanced soil biological activities. To the best of our knowledge, this is the first report of the occurrence of tryptophan–independent pathway for IAA production in the three bacilli. Conclusion This study is a novel approach towards utilizing the bacteria producing IAA through tryptophan-dependent and -independent pathways for their promise as biostimulants in wheat.