Severity expression of net blotch foliar infection as induced by initial exposure to aluminium toxicity and drought stress in barley

The interactions between aluminium toxicity, drought and net blotch may be the reasons for decreasing barley yields in Kenya despite availability of improved varieties. Such interactions induce diverse hormonal signaling and biochemical responses whose final impact on disease severity remains less understood and undocumented in barley. This research was set to identify the interaction effect of water deficiency and aluminium cation toxicity on net blotch severity. Trait-specific winter and spring barley were inoculated with 5 x 103 spore concentration of Pyrenophora teres at Zadoks growth stage 15 in a split – plot arrangement in completely randomized design with 148 µM Al, 20% Field capacity (FC) and 80% FC conditions as main plots and genotypes as sub plots. Assessment was based on 0 – 7 severity scale. Severity data was analyzed on Genstat statistical package version 16.0. Initial exposure to drought and Al toxicity significantly reduced net blotch severity compared to unstressed set of the same genotypes. In conclusion, tolerance to stress in barley involves a complex system of inherent traits, interaction of stress factors and activation of signal pathways induced by phytohormones.