Assessing cultivated strawberries and the Fragaria Supercore for resistance to soilborne pathogens

Authors: Zurn, Jason; IVORS, KELLY - California Polytechnic State University; COLE, GLENN - University Of California, Davis; KNAPP, STEVEN - University Of California, Davis; Hummer, Kim; HANCOCK, JAMES - Michigan State University; Finn, Chad; Bassil, Nahla

Submitted to: Journal of the American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2019
Publication Date: 1/1/2020
Citation: Zurn, J.D., Ivors, K.L., Cole, G.S., Knapp, S.J., Hummer, K.E., Hancock, J.F., Finn, C.E., Bassil, N.V. 2020. Assessing cultivated strawberries and the Fragaria Supercore for resistance to soilborne pathogens. Journal of American Pomological Society. 74(1):18-23.

Interpretive Summary: Soilborne pathogens can become a problem for strawberry growers. The pathogens Verticillium dahliae, Macrophomina phaseolina, and Fusarium oxysporum f.sp. fragariae are common pathogens of strawberry that cause Verticillium wilt, charcol rot, and Fusarium wilt, respectively. These pathogens are often controlled by the application of broad spectrum fumigaion. This fumigation can be detrimental to benficial microbial communities in the soil. The use of genetic resistance to these diseases can be a more economical and environmentally friendly option for disease management. To idntify sources of disease resistance, 21 cultivated strawberry varieties and 32 wild strawberry varieties were evaluated. Six plants of each variety were inoculated separately for each disease by dipping their roots in liquid containing spores of the pathogen. The percent of plants for each variety that died was recorded. If 2 or fewer plants died the variety was considered resistant. Of the accessions evaluated, 29 were resistant to V. dahliae, 20 were resistant to M. phaseolina, and 36 were resistant to F. oxysporum f. sp. fragariae. Future work is needed to identify the resistance genes, develop tools for DNA-informed breeding, and incorporate the resistance from the supercore into new strawberry varieties.

Technical Abstract: The soilborne pathogens Verticillium dahliae, Macrophomina phaseolina, and Fusarium oxysporum f. sp. fragariae are a challenge for strawberry (Fragaria ×ananassa) growers. The loss of methyl bromide and increasing restrictions on the use of other fumigants due to health and environmental concerns make the development of effective non-fumigant disease control options critical for the future economic survival of the industry. Genetic resistance can be an economical option to manage these diseases. Little is known about the genetics mediating resistance to these pathogens. Thus, there is a great need to identify sources of resistance for these pathogens to assist future breeding efforts. As such, 21 F. ×ananassa accessions and 30 individuals from the Fragaria Supercore were evaluated for V. dahliae, M. phaseolina, and F. oxysporum f. sp. fragariae resistance. Six plants of each accession were inoculated via root dips prior to planting and percent mortality was recorded. Accessions with less than 33.3% mortality were considered resistant. Of the accessions evaluated, 29 were resistant to V. dahliae, 20 were resistant to M. phaseolina, and 36 were resistant to F. oxysporum f. sp. fragariae. Future work is needed to identify the resistance genes, develop tools for DNA-informed breeding, and introgress resistance from the supercore into F. ×ananassa.