Characterization of Component Factors Associated with Differences In Cucumber Fruit Size and Shape

Cucumber (Cucumis sativus) fruit size and shape are critical determinants of market class (e.g. pickling vs. long glasshouse type) and fruit quality. To elucidate the underlying basis for variation, and to assist in targeted identification of fruit size and shape QTL, two genotypes of cucumber, GY14 (pickling) and 9930 (“Chinese Long”), that markedly differ in fruit size and shape, and for which full genome sequence is available, were chosen for study. Ovaries and fruit were analyzed from anthesis to 20 days post-pollination (dpp) for length, diameter, length and diameter ratio (LD), time and period of cell division and expansion, number of cells and cell size. Fifty plants of each genotype and their F1 progeny were grown in the greenhouse and one fruit was allowed to develop on each plant. Ten fruits out of fifty from each genotype were measured daily for fruit length and diameter, and LD until 20dpp. Of the remaining 40 fruits, five fruits from each genotype were harvested every 2 days for a period of 16 days for the determination of mesocarp cell size and cell number. Preliminary results showed that at anthesis both GY14 and 9930 have equal number of cells across the fruit, however, 9930 has more cells along the length of the fruit than GY14. Additional variation between genotypes results from the period of cell division and cell expansion post-pollination. Increase in cell number in GY14, and 9930 was observed until 6dpp, and 10dpp, respectively. On the other hand, cell size increased more sharply from 8-16dpp in GY14 than in 9930. At 16dpp, GY14 has fewer but larger cells than 9930.These preliminary results suggest that GY14 and 9930 differ for several growth related factors including cell number at anthesis and post-anthesis, time and period of cell proliferation and cell expansion post-pollination, and final cell size, that contribute to the fruit variation between the two genotypes.