Quantitative analysis of cultivation environment effects on growth and yield during summer and autumn everbearing strawberry production (cultivar ‘Suzuakane’)

Strawberry production in Japan mainly utilizes forcing culture, using June bearing cultivars with a harvest period from, November to June. From July to October, strawberry production is low, and the demand for domestic strawberries is not met. Everbearing cultivars could meet this demand, as they have flower bud differentiation under long-day conditions. However, their production is limited as there is an insufficient understanding of the relationship between climate conditions such as solar radiation, temperature, and their growth and yield. In this study, the effects of solar radiation and temperature on the growth and yield of the everbearing cultivar 'Suzuakane' were quantitatively analyzed. Two different fruit load conditions were assessed, as flower clusters that appeared before mid-May and before mid-June were removed for May and June treatments, respectively. Destructive measurements were conducted periodically, and the leaf area and dry weight by organ were determined. The amount of intercepted light was estimated to determine light use efficiency (LUE, g-DW MJ^‑1). Growth analysis was also carried out to understand the effects of temperature and solar radiation. In the June treatment, the fruit load from June to July was smaller than that in the May treatment, but there were no differences in their August yields. From 39 to 101 days after transplanting, the LUE and net assimilation rate in the June treatment were smaller than those in the May treatment, suggesting that a smaller fruit load caused a negative feedback effect and reduced the photosynthesis rate in the June treatment. Our results indicate that fruit load should be adjusted by considering the balance between temperature and solar radiation, and that the relationship between demand and supply of photosynthetic products is important.