Location: Crops Pathology and Genetics Research
2013 Annual Report
We have tested five pistachio cultivars for resistance to canker causing Botryosphaeriaceae species. Lost Hills was the cultivar most resistant to Botryosphaeria shoot blight, although it was not significantly better than the widely planted Kerman. Kalehghouchi and Aria were the most susceptible cultivars. From 300 isolates from pistachio trees in California collected from 1998 to the present, we identified eight species of Botryosphaeriaceae (Botryosphaeriaceae dothidea, Diplodia seriata, Dothiorella iberica, Dothiorella sarmentorum, Lasiodiplodia citricola, Lasiodiplodia gilanensis, Neofusicoccum mediterraneum, Neofusicoccum vitifusiforme) and one species of Diaporthe (Diaporthe rhusicola). Neofusicoccum mediterraneum, which was widely distributed, was found in 19 counties in California where pistachios are grown.
Ten commercial almond cultivars were also tested for susceptibility to Botryosphaeriaceae. In a previous study, we found seven different species attack almonds and cause band canker (cankers develop in the tree trunk), cankers initiated from pruning wounds, and cankers in the canopy starting from lenticels or natural wounds (growth cracks, limb breaking, cracks created by winds, etc.). Ten cultivars of almonds were inoculated with two of the most aggressive Botryosphaeriaceae isolated from almond cankers: Neofusicoccum nonquaesitum and Neofusicoccum parvum. The results showed, regardless of the pathogen used, some of the cultivars, i.e. Carmel and Padre, were more susceptible than the Butte and Peerless. These initial results indicate considerable differences in the resistance of almond germplasm to canker-causing fungal pathogens.