与稻米高垩白率相关的qPGWC-9的生理功能

利用携带qPGWC-9目标区段而其他置换片段上不带有与垩白率相关QTL(quantitative trait locus)的高垩白染色体片段置换系(chromosomal segment substitution line,CSSL)AIS82,以其轮回亲本Asominori(低垩白)为对照,从源库关系角度探讨qPGWC-9的生理功能。结果发现,籽粒灌浆期AIS82与Asominori的剑叶净光合速率没有显著差异,说明光合作用强弱不是AIS82高垩白率产生的直接原因。灌浆前期AIS82的淀粉合成关键酶活性显著高于Asominori,但中后期AIS82酶活下降快,整个灌浆期变化幅度相对较大,推测qPGWC-9主要影响了淀粉合成关键酶活性的动态变化,从而决定了高垩白表型。

Physiological Function of the qPGWC-9 Related to High Percentage of Rice Grains with Chalkiness

Percentage of grains with chalkiness (PGWC), one of the important traits assessing rice grain appearance quality, belonged to qualitative trait controlled by many genes. Our previous study identified a novel quantitative trait locus (QTL), namely qPGWC-9, related to high PGWC using chromosomal segment substitution line (CSSL) population. qPGWC-9 was shown to be expressed stably in eight environments. AIS82 which carried a IR24 chromosomal segment corresponding to qPGWC-9 in the Asominori genetic background was selected and analyzed to clarify the physiologi- cal function of qPGWC-9 from the relationship of source and sink of carbohydrates. It showed that AIS82 had higher PGWC than Asominori (control variety with low PGWC) (Table 1). The net photo- synthetic rate of flag leaf of AIS82 showed no sig- nificant difference from that of Asominori (Figs.1, 2), so photosynthetic ability in flag leaf was not directly related with high PGWC in AIS82. But, the changes in pattern of activity of the key en-zymes associated with starch synthesis were dif- ferent in these plants. Activities of some key en- zymes in starch synthesis in AIS82 changed more radically than those in Asominori (Fig.3). These results suggest that qPGWC-9 might determine the activities of some enzymes associated with starch synthesis and therefore affect the degree of grain chalkiness.