不同变种甜瓜糖分积累及蔗糖代谢酶活性动态变化

为了解不同类型甜瓜糖分积累及糖代谢特点,选用厚皮甜瓜品种X228、普通甜瓜品种B154及越瓜品种H227为材料,定期取样测定果实成熟过程中的葡萄糖、果糖、蔗糖含量和蔗糖代谢相关酶活性,研究不同变种甜瓜果实发育过程中糖分积累及相关酶动态变化差异。结果表明,授粉15 d至果实成熟期间,3个甜瓜品种的果实葡萄糖与果糖含量的变化均较小,品种间差异不显著。3个甜瓜品种果实蔗糖含量存在显著性差异,其中H227果实几乎无蔗糖积累,葡萄糖和果糖是果实的主要糖组分;B154和X228果实蔗糖含量随着果实发育而快速增加,蔗糖积累存在明显的转折点,蔗糖是B154和X228这2个品种成熟果实中最主要的糖组分,且果实蔗糖含量提高的同时蔗糖磷酸合成酶(SPS)活性上升、酸性转化酶(AI)活性降低,蔗糖合成酶(SS)合成方向的活性与蔗糖含量关系不显著。根据蔗糖含量的差异,可将甜瓜分为蔗糖积累型和低蔗糖积累型两类,前者果实蔗糖含量的上升被认为是SPS活性上升与转化酶(特别是AI)活性下降共同作用的结果,后者果实内极低的蔗糖含量被认为是SPS活性较低导致的。本研究结果为甜瓜种质资源创新利用和甜瓜果实糖分积累调控研究奠定了理论基础。

Dynamic Changes of Sugar Accumulation and Sucrose Metabolic Enzymes Activity During Fruit Growth and Maturation in Different Varieties of Melon (Cucumis melo L.)

In order to improve the fruit quality of melon, and to identify the characteristics of melon varieties that could satisfy the demanding of most consumer and different market trends, three melon varieties, Cucumis melo L. var. saccharinus Naud. cv. X228, Cucumis melo L. var. makuwa Makino cv. B154 and Cucumis melo L. var. conmmon Makino cv. H227 were selected to investigate the physiological mechanism of sucrose accumulation during fruit ripening. Fruit were sampled at each growth stages, and the fruit soluble solid content (Brix grade) and sugar (glucose, fructose, sucrose) content, as well as activities of sucrose phosphate synthase(SPS), sucrose synthase(SS), acid invertase(AI) and neutral invertase(NI) were measured. Results showed that the sucrose contents were significantly different among the varieties; glucose and fructose were the major sugars and only a little amount of sucrose was accumulated in immature and mature H227 fruits, while sucrose is the major sugar in B154 and X228 fruits. During fruit development, the contents of glucose and fructose in three melon varieties were not changed dramatic ally, and there were no pronounced differences in glucose and fructose contents among three varieties. The sucrose contents in B154 and X228 fruits increased remarkably during fruit development with obvious turning points. Moreover, the rise of sucrose content was accompanied by the increase of SPS activity and the decreases of AI and NI activities, while the relationship between the content of sucrose and SS was not significant. According to the changes of sucrose content in developing melon fruits, melon could be divided into two sucrose accumulation types: sucrose accumulation type, i.e. X228 and B154, and low-sucrose accumulation type, i.e. H227. In the sucrose accumulation type, the sucrose content increased accompanied by the increase of SPS activity and the decrease of AI and NI activities. In the low- sucrose accumulation type, the low sucrose content may be caused by low SPS activity. The results provided the theoretical foundation for the innovative use of melon germplasm resources and the research on regulation of sugar accumulation in melon fruits.