Searching for resistance to soilborne pathogens in cultivated strawberries and the Fragaria supercore

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

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2018
Publication Date: 6/25/2018
Citation: Zurn, J.D., Ivors, K.L., Whitaker, V.M., Knapp, S.J., Hummer, K.E., Hancock, J.F., Finn, C.E., Bassil, N.V. 2018. Searching for resistance to soilborne pathogens in cultivated strawberries and the Fragaria supercore. Abstract for the American Phytopathological Society Annual Meeting; 2018 June25-27; Portland, OR.

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 after 10 weeks was recorded. If 2 or fewer plants died the variety was considered resistant. Fifteen of the cultivated varieties were found to be resistant to Verticillium dahlie, eight were resistant to Macrophomina phaseolina, and 12 were resistant to Fusarium oxysporum. One variety (MI 10-24-52) was resistant to all three pathogens. For the wild strawberries, 13 were resistant to Fusarium oxysporum, 18 were resistant to Verticillium, and 13 were resistant to Macrophomina. Eight wild strawberries were found to be resistant to all three pathogens. To further study the genetics of resistance in the cultivated strawberries, six populations were developed. Future work will focus on identifying resistance genes, developing DNA-based tools to improve breeding, and to incorporate resistance from the wild strawberries into cultivated varieties.

Technical Abstract: Soilborne pathogens are a challenge for strawberry (Fragaria ×ananassa) growers. Pre-planting soil fumigation is used to control Verticillium dahliae (Vd), Macrophomina phaseolina (Mp), and Fusarium oxysporum f.sp. fragariae (Fof). Fumigation is detrimental to microbial communities. Genetic resistance can be an economical, environmentally friendly option for disease management. To identify sources of disease resistance, 21 F. ×ananassa accessions and 32 individuals from the Fragaria supercore, composed of F. chiloensis and F. virginiana accessions, were evaluated. Six plants of each accession were inoculated via separate root dips prior to planting. Percent mortality was recorded after 10 weeks and a mortality less than 33.3% was considered resistant. Fifteen F. ×ananassa accessions were resistant to Vd, eight were resistant to Mp, and 12 were resistant to Fof. MI 10-24-52 was the only F. ×ananassa accession resistant to all three pathogens. From the supercore, 13 of 32 accessions evaluated were resistant to Fof, 18 of 23 were resistant to Vd, and 13 of 16 were resistant to Mp. Out of 16 accessions evaluated with each pathogen, eight were resistant to all three. Six F. ×ananassa bi-parental populations have been developed to identify genes involved in resistance to these pathogens. Future work will focus on identifying resistance genes, developing tools for DNA-informed breeding, and introgressing resistance from the supercore into F. ×ananassa.