Thermotolerant PGPR consortium B3P modulates physio-biochemical and molecular machinery for enhanced heat tolerance in maize during early vegetative growth

Abstract Global maize productivity has decreased due to sudden temperature fluctuations and heat waves. The current study demonstrates the potential of beneficial bacteria for evaluating plant heat tolerance during early growth. Three Bacillus spp. AH-08, AH-67, SH-16, and one Pseudomonas spp. SH-29 showed the ability to grow and exhibited multiple plant-beneficial traits up to 45 ± 2°C. In Bacillus sp. SH-16 two small heat shock proteins (HSP) of 15 and 30kDa and in SH-16 and AH-67 two large HSP of 65 and 100kDa were upregulated at 45 and 50°C. Plant-inoculation with the consortium B3P was carried out on six maize varieties pre-grown at 25 ± 2 ºC and then applied heat shock at 10-day for 3h at 38ºC, and then 48h at 42ºC. The B3P treatment showed significant improvement in the plant growth parameters and level of catalase, peroxidase, chlorophyll, and carotenoids. The expression of HSP1 and HSP18 in Malka and YH-5427 while HSP70 and HSP101 were higher in FH-1046 and Gohar as compared to control. The results indicate that PGPR exert multiphasic responses to improve plant growth and heat-tolerance during seedling growth. Further studies will be focused on the field evaluation of this consortium under high heat to evaluate the impact on crop yield.