Metabolic and genotypic mechanisms involved in early defensive response of powdery mildew-infected wheat

Early defensive responses of powdery mildew-infected wheat were investigated in 17 Egyptian cultivars and 21 universal powdery mildew resistance genes at seedling and adult plant stages under greenhouse conditions. Genotypic responses revealed that none of the Egyptian cultivars confer complete resistance under inoculation with Blumeria graminis f. sp. tritici. Giza-168, Misr-1, Misr-2, and Giza-171 appear to have good partial resistance to the disease, while In Sakha-93, Sakha-94 and Sids-12 exhibited susceptibility. Six genes, Pm1b, Pm3a, Pm34, Pm37, NCA6, MIAG12 and NCAG13 specific all-stage resistance, six genes, Pm1a, Pm2a, Pm3b, Pm4a, Pm6, and Pm8 showed seedling susceptibility, while highest disease severities were observed in only two genes Pm6 and Pm8. Metabolic analysis of powdery mildew-infected wheat revealed a significant increase in oxidative enzyme activities (PPO, POX, CAT), Chl. a, Chl. b and carotene contents in the moderately resistant cultivars. However, increasing in electrolyte leakage was observed in susceptible cultivars. Negative correlations were recorded between powdery mildew severity and each of PPO, POX, CAT, Chl. a, Chl. b, and Car, while a positive correlation was recorded with Electrolyte leakage. Molecular assay of resistance gene Pm38 revealed gene identification in moderately resistant cultivars and was correlated with the resistance degrees. Early defense response is dependent on metabolic and genotypic mechanisms that are controlled by the expression of resistance genes.