National key laboratory of crop genetic improvement and National Center of Plant gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China.
BMC Genet. 2010 Feb 26;11:16. doi: 10.1186/1471-2156-11-16.
The three-dimensional shape of grain, measured as grain length, width, and thickness (GL, GW, and GT), is one of the most important components of grain appearance in rice. Determining the genetic basis of variations in grain shape could facilitate efficient improvements in grain appearance. In this study, an F7:8 recombinant inbred line population (RIL) derived from a cross between indica and japonica cultivars (Nanyangzhan and Chuan7) contrasting in grain size was used for quantitative trait locus (QTL) mapping. A genetic linkage map was constructed with 164 simple sequence repeat (SSR) markers. The major aim of this study was to detect a QTL for grain shape and to fine map a minor QTL, qGL7.
Four QTLs for GL were detected on chromosomes 3 and 7, and 10 QTLs for GW and 9 QTLs for GT were identified on chromosomes 2, 3, 5, 7, 9 and 10, respectively. A total of 28 QTLs were identified, of which several are reported for the first time; four major QTLs and six minor QTLs for grain shape were also commonly detected in both years. The minor QTL, qGL7, exhibited pleiotropic effects on GL, GW, GT, 1000-grain weight (TGW), and spikelets per panicle (SPP) and was further validated in a near isogenic F2 population (NIL-F2). Finally, qGL7 was narrowed down to an interval between InDel marker RID711 and SSR marker RM6389, covering a 258-kb region in the Nipponbare genome, and cosegregated with InDel markers RID710 and RID76.
Materials with very different phenotypes were used to develop mapping populations to detect QTLs because of their complex genetic background. Progeny tests proved that the minor QTL, qGL7, could display a single mendelian characteristic. Therefore, we suggested that minor QTLs for traits with high heritability could be isolated using a map-based cloning strategy in a large NIL-F2 population. In addition, combinations of different QTLs produced diverse grain shapes, which provide the ability to breed more varieties of rice to satisfy consumer preferences.
粒形的三维形状，用粒长、粒宽和粒厚（GL、GW 和 GT）来衡量，是稻米外观最重要的组成部分之一。确定粒形变化的遗传基础可以促进粒形外观的高效改良。在这项研究中，利用籼稻和粳稻品种（南阳占和川 7）杂交衍生的 F7:8 重组自交系群体（RIL），对粒型进行数量性状位点（QTL）作图。用 164 个简单重复序列（SSR）标记构建了一个遗传连锁图谱。本研究的主要目的是检测粒形的 QTL，并对一个小的 QTL，qGL7，进行精细定位。
在第 3 和第 7 染色体上检测到 4 个 GL 的 QTL，在第 2、3、5、7、9 和 10 染色体上分别检测到 10 个 GW 和 9 个 GT 的 QTL。共鉴定了 28 个 QTL，其中一些是首次报道；在两年中也共同检测到 4 个主要 QTL 和 6 个小的 QTL 对粒形的影响。小 QTL，qGL7，对 GL、GW、GT、千粒重（TGW）和每穗小穗数（SPP）表现出多效性，并在近等基因系 F2 群体（NIL-F2）中进一步验证。最后，qGL7 被缩小到 InDel 标记 RID711 和 SSR 标记 RM6389 之间的一个区间，该区间覆盖了日本晴基因组中的一个 258-kb 区域，与 InDel 标记 RID710 和 RID76 共分离。
由于其复杂的遗传背景，使用具有非常不同表型的材料来开发作图群体以检测 QTL。后代测试证明，小 QTL，qGL7，可以表现出单一的孟德尔特征。因此，我们建议可以使用基于图谱的克隆策略在大的 NIL-F2 群体中分离具有高遗传力的性状的小 QTL。此外，不同 QTL 的组合产生了不同的粒形，为培育更多满足消费者偏好的水稻品种提供了能力。
