Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2017
Publication Date: 2/7/2018
Citation: Naegele, R.P. 2018. Evaluation of host resistance to Botrytis bunch rot in Vitis spp. and its correlation with Botrytis leaf spot. HortScience. 53(2):204-207. https://doi.org/10.21273/HORTSCI12655-17. Interpretive Summary: Botrytis cinerea is the number one postharvest pathogen of fresh market table grapes, and causes losses in the field on both wine and table grapes. Managing this disease requires the regular use of fungicides, which are detrimental to the environment and expensive for growers. Plant host resistance to Botrytis is needed to reduce chemical inputs. Twenty-seven lines of grape (Vitis spp.) were evaluated for potential resistance to Botrytis-induced bunch rot and leaf spot. Most lines tested were susceptible to both isolates used in this study. One source of resistance with poor fruit quality was identified, and additional sources with reduced susceptibility and moderate fruit quality were identified. Leaf spot and fruit rot resistance were positively correlated, suggesting leaf testing may be a suitable alternative for evaluating resistance.
Technical Abstract: Botrytis cinerea, the causal agent of Botrytis bunch rot and gray mold, is the number one postharvest disease of fresh grapes in the United States. Fungicide applications are used to manage the disease, but fungicide-resistant isolates are common and postharvest losses occur annually. Host resistance is needed for long-term management of the disease. Sources of resistance in grape have been identified, but often have poor fruit quality. In this study, twenty-seven grape lines (cultigens and species), including high fruit quality V. vinifera, were evaluated for fruit and leaf susceptibility to two isolates of Botrytis cinerea. No significant differences in virulence or pathogenicity were detected between the two isolates, but differences in disease incidence were evident among lines in leaves and berries. Most Vitis vinifera cultivars evaluated had high disease incidence in berries, while complex hybrids, V. aestivalus, and V. arizonica, had low to moderate disease incidence. Two V. vinifera breeding lines had moderate susceptibility (<50% disease) to Botrytis bunch rot when inoculated with either isolate. Only one V. vinifera line had little (<5%) to no berry or leaf disease when inoculated with either isolate. Moderate resistance (10-25%) was detected in Vitis spp., and a single Vitis vinifera line. Correlations were examined among soluble solids, leaf susceptibility, and fruit susceptibility. No correlations between soluble solids and disease susceptibility (leaves or berries) were identified, but moderate correlations between leaf and berry susceptibility were observed. Moderate resistance to Botrytis bunch rot and leaf spot were detected in Vitis breeding lines, suggesting these may be useful for developing grape cultivars with high fruit quality and resistance to B. cinerea.