Inheritance of Resistance to Colletotrichum acutatum Simmonds on Runners of Garden Strawberry and its Backcrosses

Two half diallel mating designs were conducted to study the inheritance of resistance to Colletotrichum acutatum Simmonds on runners of strawberry. The main design included six genotypes representing a range of responses to the pathogen: `Chandler' (very susceptible); FL 87-210 (tolerant); MS/US 541 (very resistant); NC 92-01 ( Fragaria chiloensis Duch.) (resistant); NCH 87-10 (tolerant-susceptible); and NCC 89-39 (susceptible). The cross `Chandler' × MS/US 541 was absent. The secondary test included `Chandler' and selections FL 87-210 and NC 85-01 ( Fragaria virginiana Duch.) (very resistant) as parents. Griffing's methods 4 and 2, model I, were used to test for combining ability in the main and secondary tests, respectively. General combining ability and specific combining ability were highly significant in all analyses. This study indicated that nonadditive effects are more important than additive effects in the inheritance of resistance of runners to anthracnose. The frequency distribution of lesion lengths within progenies suggests that resistance to C. acutatum on runners is quantitative. Therefore, breeding for resistance should be accomplished using progeny testing followed by individual selection within progenies.