Signaling and cross-talk between Salicylic Acid and Abscisic Acid phytohormones on Net Blotch, Aluminium toxicity and drought stresses in barley

Varying levels of abscisic acid and salicylic acid whose effects can be antagonistic or synergistic are produced by plants including barley under stress conditions. This scenario has not been explored in details and scientifically documented in barley despite the fact that the pathways leading to synthesis and catabolism of these hormones entirely depend on the genetic make-up of each variety, crop nutrition and environmental conditions. This research was designed to determine the phenotypic expression of tolerance to net blotch foliar severity, aluminium toxicity and drought stresses in barley. Twenty four traitspecific winter and spring barley initially grouped into 3 categories of eight genotypes for net blotch, aluminium toxicity and drought were treated with ABA, SA, ABAxSA phytohormones and distilled water as control. The treatments were arranged in split-plot manner with phytohormones as main plot and genotypes as sub-plots in a completely randomized design replicated thrice. Net blotch set of genotypes were inoculated with 5 x 103 spore concentration of Pyrenophora teres at Zadoks growth stage 15 and assessed on 0 – 7 severity scale. Aluminium toxicity and drought stress sets were maintained at 148 μM and 20% field capacity respectively and hormonal treatments were applied as soil drench twice at seedling emergence and 14 days later. Disease severity, aluminium toxicity and drought stress data were subjected to Genstat statistical software version 16.0. Treating barley with SA enhanced tolerance levels across all genotypes but single application of ABA was ineffective. Synergistic tolerance induction was stronger when SA and ABA are combined under aluminium and drought stresses compared to net blotch disease. In conclusion, SA enhanced tolerance to net blotch disease while synergy was expressed when SA and ABA are combined to enhance tolerance to drought and aluminium toxicity