Abstract
Inbreeding is a great concern for strawberry plant breeders because of the repeated crossings among a limited number of breeding materials. Coefficients of inbreeding (CI) in recently developed cultivars of strawberry were calculated using a personal computer and a programming language, Prolog. The relation between CI and yield was also investigated in the strawberry. There was no correlation between the selection rate of F1 seedling plants and CI of those plants. In the strawberry breeding lines from Tochigi Branch, Tochigi Prefectural Agricultural Experiment Station, the correlation coefficient between CI and yield was −0.37, which was significant at the 1% level. The figure showed that strawberry plants with a CI less than 0.3 did not show any inbreeding depression. The CIs of several recently bred strawberry cultivars of the June-bearing type were approximately 0.2. CIs of ‘Tochiotome’, ‘Akihime’, ‘Sagahonoka’, ‘Amaou’, ‘Satumaotome’, ‘Hinosizuku’ and ‘Yayoihime’ were 0.261, 0.222, 0.257, 0.213, 0.257, 0.247 and 0.346, respectively. Those of CIs of ever-bearing type cultivars were approximately 0.1, except ‘Summer Princess’ and ‘Kiminohitomi’. Hypothetical diallel crossing among 15 representative June-bearing type cultivars resulted in CIs of their offsprings ranging from 0.067 to 0.440 with an average CI of 0.210.
