Exogenous application of epibrassinolide attenuated Verticillium wilt in upland cotton by modulating the carbohydrates metabolism, plasma membrane ATPases and intracellular osmolytes

Verticillium dahliae toxin (Vd toxin) was employed as pathogen free model system to induce osmotic stress on upland cotton and its amelioration is investigated using epibrassinolide (EBR). In this study, we observed the physiological and biochemical differences among Vd toxin alone and EBR + Vd toxin treated plants using different levels of root (5, 10, 15 nM) and shoot (50, 100, 200 nM) applied EBR. Results revealed that in absence of EBR, Vd toxin caused 83 % plant wilting and the levels of glycine betaine and proline were 33 and 61 % higher than non treated control, respectively. However, the accumulation of these osmolytes was decreased in EBR treated plants with minimum values at 5 and 200 nM. Furthermore, the results depicted a remarkable decline in soluble sugars, photosynthesis, transpiration, chlorophyll content and chlorophyll florescence (Fv/Fm) in Vd toxin alone treated plants than EBR + Vd toxin. Besides, the activities of sucrose synthase, sucrose phosphate synthase and acid invertase were high in Vd + EBR treated plants with increased root and shoot biomass than Vd toxin alone treated plants. Moreover, EBR remarkably regulated the levels of plasma membrane ATPases and contents of total ATPase and Na+ K+-ATPase were elevated while contents of Ca2+ Mg2+-ATPase and H+ K+-ATPase were decreased as compared to Vd toxin alone treated plants. This study broadens our understanding of Verticillium wilt and demonstrates the potential role of EBR in mediating tolerance against Vd toxin induced stress of V. dahliae in cotton.