Effect of Long-day Treatments before Planting on Flower Initiation and Autumn Yield of First-year Runner Plant of Everbearing Strawberry ^|^lsquo;Natsuakari^|^rsquo;

Abstract

Long-day treatments were applied to everbearing strawberry (Fragaria × ananassa Duch.) 'Natsuakari' before planting to accelerate flower initiation for the autumn harvest. Twenty-four-hour day length treatment for one month promoted the flower initiation of runner plants potted on May 30, June 17, July 1, and in the previous July. The yields of the first-year runner plants that were subjected to 24-h treatment were not lower than those of the plants potted in the previous July. An increase in day length led to a corresponding increase in flower initiation. Two weeks of treatment was sufficient for flower initiation in all the plants that underwent 24-h day length treatment or 4-h night interruption treatment. In the case of plants that underwent 16-h day length treatment, anthesis was observed in all of these plants after treatment for a total of one month. Three different planting dates after 24-h continuous or cyclic lighting (15 min・h −1 , overnight) treatments were investigated. As a result of 24-h continuous lighting for 3 weeks, harvesting could be initiated from early September for plants that were planted on July 28, but the yield in October was higher for the plants that were planted on August 10. Not all of the plants that were planted on September 2 could be harvested by December. Cyclic lighting was markedly less effective for flowering than continuous lighting.

Recent Progress of Strawberry Year-round Production Technology in Japan

“…In addition, everbearers sometimes develop excessive branch crowns, inflorescences, and flowers, meaning more management and labor is required for debudding, pruning, and thinning. Some recent noteworthy work includes studies on the photoperiodic response of flowering under high temperature regimes 15,16,18 , flower induction by long-day treatment 9 , the high temperature effects on flowering and fertilization 3,4 , the involvement of chilling and runner production 7,8 , seasonal changes in fruit sugar content 5 , the analysis of root structure 30 , and the application to forcing culture 10 . Despite the shortage of information on flowering physiology, there are many active breeding programs involving new everbearing varieties in public and private institutions.…”