Vigorous strawberry lines developed from recurrent selection under forcing culture

We developed strawberry (Fragaria × annassa Duchesne) lines that grew well with short day length and low temperature under forcing culture. A total of 36 cultivars of non-everbearing strawberry cultivars (32 Japanese and 4 foreign) were divided into three groups based on their genetic differences. We performed recurrent selection in sets of one self-pollination and one cross-pollination. The main breeding objective was to develop cultivars with stable plant vigor during the harvesting period. Two or three generations of recurrent selection produced very vigorous lines. The average leaf area of the largest leaf, a measure of plant vigor, was larger than the leaf area of the cultivar 'Kaorino' which is one of the most vigorous strawberry cultivars in Japan. A line was produced with leaf area twice that of 'Kaorino'. Strawberry is generally predisposed to inbreeding depression, but some self-pollinated lines obtained from recurrent selection had leaf area larger than that of 'Kaorino'.