Abstract
In order to make a systematic classification scheme of oriental melons (Cucumis melo L.), 32 melons with different ecotypes were collected from Japan, China, Taiwan and South Asia, and differences in morphological and physiological characters of these melons were investigated.
For morphological differences, basal size of spine on the petiole was the largest in Japanese melons and the smallest in those in South Asia. Leaf stomatal density and depth of leaf incision were the smallest in melons in South Asia. The numbers of inner cell layers in the seed coat were 2, 3 or mixed in Japanese melons, mostly 2 in Chinese melons and 2 in all the melons in South Asia. For ecological differences, resistance to water stress was stronger in melons in South Asia than in those in the other areas. Resistance to low temperature was stongest in Japanese melons. For physiological differences, all the melons in South Asia had 4 clear isozyme bands in acid phosphotase at seed-germination time. Some of the Japanese or Chinese melons had a few thin bands or even lacked one of the 4 bands. The component of leaf phenolic- like-compounds in some melons in South Asia slightly differed from that in melons in the other areas. Many of Chinese and Japanese melons had sucrose in the fruit, which was lacking in melons in South Asia. Half of Chinese melons and most of melons in South Asia had another unidentified sugar, which was lacking in Japanese melons.
All the melons in South Asia showed deep seed dormancy while many of Chinese and Japanese melons showed weak dormancy. All 26 characters, including the other data, were analyzed by cluster analysis to obtain a similarity value among various melons. All the melons in South Asia, a few Chinese melons, conomon group and weedy melon belonged to one major group. Many of the Chinese melons and all Japanese melons except ‘Katsurashirouri’ belonged to another major group. These results suggest that Japanese sweet melons were introduced from China after some breeding process while conomon melon and weedy melon were introduced with little change in China or directly from South Asia.
