GENETIC VARIABILITY IN APPLE FRUIT STORAGE DISORDERS

The genetic component of apple fruit susceptibility to storage disorders was estimated. Thirty half-sib families derived from open-pollinated seed, obtained from different countries were used in the study. Fruit from 267 seedlings (three - five seedlings per family at each of two sites) were sampled once or twice during maturity and assessed after eight weeks’ cold storage in air. Considerable variation in the incidence of disorders existed among individual seedlings; for instance, for internal bitter pit incidence across both sites, the overall seedling mean was 7% with a maximum of 86% and 138 seedlings with none of the disorder. Soft scald was the only disorder that was highly heritable at each site and across both sites, indicating a high degree of genetic control for this disorder, which is independent of environmental effects. In contrast, incidences of internal and external bitter pit and brown heart, showed strong site x family interactions and were moderately heritable traits at each site but not across both sites.