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2019 ASHS Annual Conference

Genomic Prediction for Increasing Resistance to Verticillium Wilt in Heirloom and Modern Populations of Strawberry

Wednesday, July 24, 2019
Cohiba 5-11 (Tropicana Las Vegas)
Dominique D.A. Pincot, University of California, Davis, Davis, CA
Randi Famula, University of California, Davis, Davis, CA
Glenn S. Cole, University of California, Davis, Davis, CA
Michael A. Hardigan, University of California, Davis, Davis, CA
Thomas R. Gordon, University of California, Davis, Davis, CA
Steven J. Knapp, University of California, Davis, Davis, CA
Verticillium wilt, a soil-borne disease caused by the fungal pathogen Verticillium dahliae, was initially discovered in strawberry (Fragaria × ananassa) in 1931. This widespread pathogen causes significant losses in strawberry production worldwide. Despite extensive research, including 38 previously published studies, the genetics of resistance to this pathogen appears to be quantitative and remains murky—thus far, only one genome-enabled forward genetic study has been reported. While resistant cultivars have been developed, there are only a few highly resistant cultivars, and the frequency of moderately to completely susceptible cultivars is extremely high across the globe. To develop insights into the genetics of resistance, we developed and studied a training population comprised of 480 germplasm accessions including heirloom and modern cultivars representing demographic and phenotypic diversity worldwide. The training population was genotyped with a 49,000-SNP genotyping array and phenotyped for resistance to Verticillium wilt in 2016-17 and 2017-18 field experiments where plants were artificially inoculated and grown in soils that had been fumigated to eliminate the confounding effects of other soil-borne pathogens. We observed a full range of phenotypes from highly susceptible to highly resistant. The broad-sense heritability of resistance was 0.70 in 2017 and 0.60 in 2018, and phenotypes were correlated between years (r = 0.53). Statistically significant signals were not observed in a genome-wide association study (GWAS), indicating that the underlying genetic variation is quantitative in nature. To explore the application of genomic selection for Verticillium wilt resistance, marker-based genomic kinship BLUP was investigated for potential in predicting Verticillium resistance within- and across-years. Our results suggest that breeding for resistance to this pathogen can be improved by applying genomic prediction approaches early in the breeding cycle, before phenotypic selection can be performed.
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