Salt Stress Alters Pathogenic Behaviour Of Fusarium Oxysporum F. Sp. Ciceris And Contributes To Severity In Chickpea Wilt Incidence

Soil salinity is one of the most prominent abiotic stresses whereas wilt disease caused by Fusarium oxysporum f. sp. ciceris is the major biotic stress in chickpea. We carried out an experiment to understand the mechanism of wilt development in chickpea (cv. JG-62) by F. oxysporum f. sp. ciceris isolate 49 (Foc-49) in soil under salinity (NaCl) stress. High NaCl concentration had a negative influence on chickpea seed germination and growth while positively influenced mycelial growth and sporulation in Foc-49. Increased mycelial growth, mycelial biomass, sporulation, and microconidial production was observed in Foc-49 cultured in high NaCl concentrations. Similarly, at higher NaCl concentrations either extensive root colonization by Foc-49 or severe rotting of the roots was observed in plants challenged with or without Foc-49, respectively. In contrast, Foc-49 alone without NaCl caused extensive browning of the chickpea roots initially and rotting at a later stage. Mortality of chickpea plants was also high in the combined treatment of Foc-49 and NaCl. Additionally, results from the virulence study showed that G-protein and MAP kinase-mediated signalling were active in Foc-49 while interacting with the JG62 plants under NaCl stress. Moreover, up-regulation of the SNFI, cell wall-degrading enzymes, and fusaric acid biosynthesis genes and down-regulation of the SIX effector genes in Foc-49 during interaction with the chickpea plants under NaCl stress indicate that soil salinity promotes growth in Fusarium sp. and push the pathogen to shift its pathogenic lifestyle towards the necrotrophic state by-passing the hemibiotrophic state.