DEVELOPMENT OF STRAWBERRY BREEDING LINES WITH EXTENDED DORMANCY

Abstract

The short-day cultivar 'Judibell' emerges from dormancy 4-5 weeks later than most other strawberry cultivars and crops around 35 days later than the industry standard, 'Elsanta'. The inheritance of this trait was investigated by intercrossing 'Judibell' with five late and mid-season genotypes in all combinations including selfs, but without reciprocals (half-diallel). Twenty-five seedlings from each of the 21 families (totalling 525) were planted in the field in a randomised block design. The plants were over-wintered and assessed the following year. The seedlings were evaluated weekly for date of emergence from dormancy and date of first flower. Assessment of the progeny indicated that there was segregation in the seedling population for both duration of dormancy and flowering time. These two traits were found to be highly heritable and independent of one another. Inheritance was concluded to be quantitative and additive, as there was no evidence of segregation to suggest that either was under the control of a single major gene. Whilst all the 'Judibell' selfed seedlings had long dormancy, not all had the later flowering trait. This suggests, therefore, that this line does not have the ideal genetic combination to flower as late as possible. By careful selection of parents it may be possible to combine a more extreme expression of long dormancy and late flowering to develop short-day strawberries with an even later fruiting period than the cultivar 'Judibell'. Seedlings with a very late season were selected from the half-diallel progeny and backcrossed to 'Judibell' and another, related line. The seedlings were evaluated, as before, for date of emergence from dormancy and flowering date. Whilst one family contained individuals with a longer average dormancy, another contained plants which flowered the latest. This finding provides further evidence that the two traits are independently inherited.