水稻穗型和籽粒大小不仅对产量形成有显著效应，对稻米品质尤其是外观品质也有重要影响。直立穗性状一般由qpe9-1/dep1等位基因控制，已广泛应用于高产粳稻育种，但其稻米的外观品质往往不够理想。GS9是水稻粒形的重要调控因子，该基因突变后可使稻谷适当变细长，从而改良稻米的外观品质。然而，GS9和qPE9-1/DEP1基因都位于第9染色体，两位点紧密连锁，且两者间的互作关系还不明确，这就制约了它们在现代水稻育种中的应用。蛋白和mRNA表达水平的比较分析显示GS9和qPE9-1独立发挥功能。以含有GS9和qpe9-1等位基因的高产粳稻品种2661(GS9/qpe9-1)为背景，创建了3个近等基因系（NIL），分别携带不同等位基因组合，包括NIL(gs9/qpe9-1)、NIL(GS9/qPE9-1)和NIL(gs9/qPE9-1)。结果显示，GS9和qPE9-1对籽粒大小的调控具有加性效应，在含有qpe9-1等位基因的直立穗粳稻品种中导入功能缺失型gs9等位基因，可在不影响株型和穗型的前提下，降低籽粒垩白，改良籽粒外观。此外，在另一推广的高产粳稻品种武育粳27（WYJ27）背景中，导入gs9等位基因，也表现出相同的效应，进一步证实利用gs9等位基因改良高产粳稻品种籽粒外观的可行性。本研究为直立穗粳稻及相关品种稻米外观品质改良提供了有效策略。

There are nearly 1 000 rice landrace varieties in the Taihu basin, China. To assess the genetic diversity of the rice, 24 intragenic molecular markers (representing 17 starch synthesis-related genes) were investigated in 115 Taihu basin rice landraces and 87 improved cultivars simultaneously. The results show that the average genetic diversity and polymorphism information content values of the landraces were higher than those of improved cultivars. In total, 41 and 39 allele combinations (of the 17 genes) were derived from the landraces and improved cultivars, respectively; only two identical allele combinations were found between the two rice variety sources. Cluster analysis, based on the molecular markers, revealed that the rice varieties could be subdivided into five groups and, within these, the japonica improved rice and japonica landrace rice varieties were in two separate groups. According to the quality reference criteria to classify the rice into grades, some of the landraces were found to perform well, in terms of starch quality. For example, according to NY/T595-2002 criteria from the Ministry of Agriculture of China, 25 and 33 landraces reached grade 1, in terms of their apparent amylose content and gel consistency. The varieties that had outstanding quality could be used as breeding materials for rice quality breeding programs in the future. Our study is useful for future applications, such as genetic diversity studies, the protection of rice variety and improvment of rice quality in breeding programs.

Eating and cooking qualities (ECQs) of rice are important attributes due to its major influence on consumer acceptability. To better understand the molecular mechanism of the variation in ECQs, we investigated and compared the expressions among different alleles of the Waxy (Wx) gene and its effect on ECQs in specialty rice cultivars. The results showed that the accumulation of amylose was positively and significantly correlated to the level of mature Wx mRNA and granule-bound starch synthase I (GBSS I) in developing rice grain at 12 days after flowering. The amount of GBSS I and its activity together are the main factors controlling amylose synthesis. Differences in ECQs among five Wx allele types were investigated in samples from 15 rice varieties. The apparent amylose content (AAC) and gel consistency (GC) were similar in each type of Wx allele. The AAC followed the order, Wxa type>Wxin type>Wxb type>Wxmq type>wx. Contrary to this, the GC showed an opposite trend compared to AAC. There was a wide variation in rapid visco analyzer (RVA) profile among five Wx allele types, while varieties sharing a specified Wx allele had basically the similar RVA profile, although there was a slight difference in some RVA parameters, peak, hot paste and cool paste viscosities.