Comparative effectiveness of Bacillus spp. possessing either dual or single growth-promoting traits for improving phosphorus uptake, growth and yield of wheat (Triticum aestivum L.)

The aim of this study was to compare the effectiveness of Bacillus spp. simultaneously carrying dual traits such as P solubilization and ACC deaminase activity with Bacillus spp. having any one of these traits for improving growth, yield and P uptake by wheat crop. Six Bacillus strains having predominantly either ACC deaminase activity (KA1 and KA2) or P solubilizing activity (KP3 and KP4) or simultaneously both of these traits (KAP5 and KAP6) were evaluated for improving growth of wheat cv. Bhakar-2002 using rock phosphate (RP) as an exclusive P-source. Under axenic conditions, the bacterial strains with dual plant growth-promoting activities were superior in improving growth of wheat as compared to the strains possessing single trait. Similarly, these dual traits bacterial strains were more effective than single trait strains under soil conditions (pot trial) in increasing root weight (up to 3.9-fold) and root elongation (up to 3.8-fold), dry shoot weight (up to 37.6%), number of tillers (up to 56%), grain yield (up to 38.5%) and P uptake in grain (up to 77.4%) of wheat grown in the presence of P applied as diammonium phosphate (DAP), RP (rock phosphate) or RP-enriched compost. An almost similar trend was observed when the same trial was repeated under field conditions. Inoculation in the presence of RP-enriched compost resulted in promoting various growth parameters almost comparable to that recorded in the case of DAP. It was concluded that the simultaneous presence of two superior plant growth-promoting traits in the bacteria could have an additive effect not only on growth and yield of wheat but also on P uptake. The performance of Bacillus strains possessing dual traits was distinctly superior to that of the single trait strains. These bacteria exhibited an excellent effectiveness in utilizing RP as the source of P in the growth medium as well as in soil.