A Study on Root Exudation Pattern and Effect of Plant Growth Promoting Fungi during Biotic and Abiotic Stress in Pigeonpea

An experiment was conducted to observe the interaction of Fusarium udum and Macrophomina phaseolina with a rhizospheric microbe Pseudomonas [AKC-O11] to see their impact on pigeonpea under biotic and abiotic conditions. Both biotic [Fusarium udum and Macrophomina phaseolina] and abiotic stress (NaCl) were applied and performances of these microbes were evaluated. The strain was used individually and in combination with the stresses and applied as seed bacterization of pigeonpea (Var. MA-3) seeds to see the impact on total phenol content in plant root exudates. The bacterized seeds were grown under invitro conditions and after three days of germination the seedlings were exposed to biotic stress due to challenge of the pathogens [Fusarium udum and Macrophomina phaseolina] and abiotic stress due to irrigation with salt solution of 100 mM. Root exudates were collected at 48 h, 96 h and 144 h after the application of stresses. The collected root exudates were processed for total phenolic content and High Pressure/Performance Liquid Chromatography (HPLC) analysis. It was observed that total phenol content was low in seeds bacterized with Pseudomonas strain but the concentration increased when the plants were challenged with the pathogen particularly Macrophomina phaseolina and NaCl. Similarly, a similar trend was also observed in gallic acid accumulation. The above results indicates that Pseudomonas strain (AKC-O11) have potential to be used as biocontrol agent that can help pigeonpea plants to combat attack of Macrophomina phaseolina and Fusarium udum as well as salinity.