Factors affecting fruit abortion in a gynoecious cucumber cultivar

Abstract: Fruit growth of the gynoecious cucumber 'NK x AN8' was measured non-destructively to clarify whether the presence of fruit at lower nodes caused the abortion of fruit at upper nodes. When only one fruit per plant was allowed to grow, fruit growth could be divided into two phases: slow exponential and fast exponential. Phase change from slow to fast occurred when cumulative temperatures (CTs) after anthesis reached 38 and 54?C d for pollinated and parthenocarpic fruit, respectively. The CT was calculated as the sum of the differences between daily temperatures and 5?C. When fruit at nodes 4 and above were allowed to grow, the first growth phase was prolonged. Furthermore, parthenocarpic fruit aborted frequently when the sum of the relative growth rate (RGR) with respect to the CT (the sum of RGRs) for fruit at lower nodes exceeded 0.1 g g^-1 (?C d)^-1. Pollination with pollen of the monoecious cucumber '028' strongly suppressed fruit abortion; a large number of fruits could develop to a commercial size even when the sum of RGRs for fruit at lower nodes exceeded 0.1 g g^-1 (?C d)^-1. These results suggested that fruit abortion is more related to the existence of actively growing fruit than to the absolute amount of dry mass accumulation in the fruit.