Methods of screening apricot fruit for resistance to brown rot caused by Monilinia spp.

Four methods were evaluated over 3 years for their ability to determine the resistance of ten cultivars of apricot ( Prunus armeniaca) to the brown rot pathogens, Monilinia fructicola and M. laxa. Methods assessed were lesion development on wounded and non-wounded inoculated fruit, spore productions from these lesions, the postharvest development of brown rot from natural infection, and cuticle thickness of ripe fruit. There were high correlations among lesion area and spore count assessments, but neither lesion area nor spore count assessments correlated with storage rot or cuticle thickness. Storage rot and cuticle thickness did not correlate with each other. Although all methods detected cultivar differences in disease susceptibility, there were year effects and cultivar x year interactions for most methods. Measuring lesion area on wounded, artificially inoculated fruit after 72 h was the most robust method. The spore count method was labour-intensive and gave no additional information over the lesion area method. Storage rot and cuticle thickness provide additional criteria for cultivar resistance. It is suggested that more than one method, for example, lesion area assessments in combination with storage rot and/or cuticle thickness, is used for screening apricot resistance to brown rot disease and that tests should be conducted over several years.