Evaluating physiological and genetic variation of Quercus brantii response to Brenneria goodwinii in Iran

Brenneria goodwinii is a bacterial pathogen causing severe decline in Quercus brantii. We explored the effects of B. goodwinii on physiological traits of Q. brantii seedlings and assessed differences between families in the response to the pathogen. We examined 210 seedlings from 14 half-sib families. To evaluate disease resistance, foliar symptoms and several physiological traits, including chlorophyll fluorescence and electrolyte leakage were measured in pathogen-inoculated and mock-inoculated seedlings. In addition, seven EST-SSR markers associated with stress resistance were genotyped in two resistant and two susceptible families. All physiological traits were negatively affected by pathogen inoculation. There was significant genetic variation among the families, with the most susceptible ones showing a worse physiological condition. The heritability and coefficient of genotypic variation of the resistance increased during the experimental period reaching relatively high values (0.49 and 35%, respectively) five weeks after inoculation. EST-SSR analysis revealed that resistant families showed the highest heterozygosity. Two of the seven evaluated loci were associated with the measured physiological traits and showed high FST values. Our results support that resistant mother trees can be selected for disease management. The putative alleles of FIR053 locus could be useful for identifying resistant Q. brantii families to the pathogen.