Studies on Pseudomonas and Trichoderma-Mediated Root Exudation Pattern in Chickpea against Fusarium oxysporum f. sp. Ciceris

Plant growth-promoting microbes are known for protection of plants against a number of phytopathogens. In the present study, we used Pseudomonas fluorescens OKC and Trichoderma asperellum T42 singly as well as in combination in chickpea (Cicer arietinum) under challenge of Fusarium oxysporum f. sp. ciceris (Foc). Two cultivars of chickpea were used, viz., L550 susceptible to Foc and Avarodhi resistant to Foc. Root exudates obtained from the two cultivars of chickpea were analyzed and showed higher amount of Total Phenolic Content (TPC) accumulated in the microbe-treated plants compared to microbe un-treated control. Maximum phenolic content was observed in exudates of OKC treated plants in both cultivars. Interestingly, in OKC treated plants, TPC was higher in the exudates of the susceptible cultivar L550 compared to the resistant cultivar Avrodhi. Gallic acid content in the exudates also confirmed the pattern of TPC in the treatments. Wilting due to Foc was significantly reduced in the OKC and T42 treated plants compared to the untreated plants and thereby showed a positive correlation between TPC in exudates and reduction in Fusarium wilt. Higher TPC in the susceptible cultivar compared to the resistant cultivar clearly indicates the roles of OKC and T42 in reducing the wilt symptom whereas no wilting in the resistant cultivar may be explained due to genetic factor. High total chlorophyll content in the OKC and T42 treated plants of L550 also show the role of the microbes in maintaining a good health of the Foc challenged plants.