Nerson, H., Department of Vegetable Crops Agricultural Research Organization, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel

Six open-pollinated melon cultivars from different market types were grown in a partially controlled greenhouse during the four seasons over the year, to observe their seed production and quality. A strong positive correlation was observed between fruit yield and seed yield per plant, both of which were highest in fall and lowest in winter and summer. The mean seed yield per plant was 23.4, 13.7, 10.6 and 9.0 g in fall, spring, summer and winter respectively. The differences in seed yield among seasons were mainly due to different number of seeds per fruit rather than in mean seed weight. The average fully-developed seed number per fruit in the fall was higher by 26, 61 and 76% than in the summer, winter and spring, respectively. The limiting factor of melon seed production in winter was the high percentage of empty seeds (42-64% in the different cultivars). Cultivar 'Noy Yizre'el' had, in most cases, the highest number but the smallest fruits, and this combination resulted in the highest seed yield. There were significant interactions between cultivars and growing seasons with respect to seed yield. In all six cultivars, maximum seed yield was obtained in fall, and minimum seed yield in winter or summer. The six cultivars were differentiated into two groups with respect to seed yield index [seed yield (g)/fruit yield (kg)]. The mean index of the efficient 'Persia 202', 'Noy Yizre'el' and 'Noy Amid' was 15.7 and of the less-efficient 'Ananas Yoqne'am', 'Perlita' and 'Tam Dew' was 11.8. 'Noy Yizre'el' and 'Perlita' were characterized by significant partial seed dormancy, independent of growing season. They had slow and a low percentage germination at seed harvest, which markedly and gradually improved during seed storage. There were significant interactions between cultivar and growing season with respect to germinability. In 'Persia 202' and 'Ananas Yoqne'am', germination was excellent (>95%) and good (75-85%), respectively, in all seasons. Germination was worse for 'Noy Yizre'el' in winter and for 'Perlita' in fall, than in other seasons, and in 'Noy Amid' and 'Tam Dew' germination in two of the seasons was better than in the other two seasons.