Identifying Resistance to Crown Rot Caused by Colletotrichum gloeosporioides in Strawberry.

Resistance to Colletotrichum crown rot (CCR, caused by Colletotrichum gloeosporioides) among commercial strawberry cultivars is variable, and increasing host resistance is a goal of the strawberry breeding program at the University of Florida. Twenty-eight accessions of Fragaria virginiana and F. chiloensis, the progenitor species of the cultivated strawberry (F. × ananassa), were evaluated for CCR resistance on artificially inoculated plants in a field trial, along with cultivars and breeding selections. Accessions PI 612320, PI 612323, and PI 551736 and selections FL 10-128 and FL 10-129 had no mortality in either of two seasons. The most susceptible genotypes had mortality between 75 and 100%. In a separate growth-chamber evaluation, seven genotypes were inoculated by spraying a spore suspension onto the crown or by injecting the suspension directly into the crown tissues. Mortality was higher using the injection method but the ranking of the genotypes was similar for both methods, indicating that resistance is expressed within crown tissues. Among the seven genotypes, selections FL 10-128 and FL 10-129 had the lowest mortality regardless of inoculation method, illustrating that a high level of resistance can be found within the cultivated germplasm.