Tian Feng, Zhu Zuofeng, Zhang Boshen, Tan Lubin, Fu Yongcai, Wang Xiangkun, Sun Chuan Qing
Department of Plant Genetic and Breeding and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100094, People's Republic of China.
Theor Appl Genet. 2006 Aug;113(4):619-29. doi: 10.1007/s00122-006-0326-y. Epub 2006 Jun 13.
SIL040, an introgression line (IL) developed by introgressing chromosomal segments from an accession of Oryza rufipogon into an indica cultivar Guichao 2, showed significantly less grains per panicle than the recurrent parent Guichao 2. Quantitative trait locus (QTL) analysis in F2 and F3 generations derived from the cross between SIL040 and Guichao 2 revealed that gpa7, a QTL located on the short arm of chromosome 7, was responsible of this variation. Alleles from O. rufipogon decreased grains per panicle. To fine mapping of gpa7, a high-resolution map with 1,966 F2 plants derived from the cross between SIL040 and Guichao 2 using markers flanking gpa7 was constructed, and detailed quantitative evaluation of the structure of main panicle of each of F3 families derived from recombinants screened was performed. By two-step substitution mapping, gpa7 was finally narrowed down to a 35-kb region that contains five predicted genes in cultivated rice. The fact that QTLs for five panicle traits (length of panicle, primary branches per panicle, secondary branches per panicle, grains on primary branches and grains on secondary branches) were all mapped in the same interval as that for gpa7 suggested that this locus was associated with panicle structure, showing pleiotropic effects. The characterizing of panicle structure of IL SIL040 further revealed that, during the domestication from common wild allele to cultivated rice one at gpa7, not only the number of branches and grains per panicle increased significantly, more importantly, but also the ratio of secondary branches per panicle to total branches per panicle and the ratio of grains on secondary branches per panicle to total grains per panicle increased significantly. All these results reinforced the idea that gpa7 might play an important role in the regulation of grain number per panicle and the ratio of secondary branches per panicle during the domestication of rice panicle.
SIL040是一个渗入系，通过将来自普通野生稻的染色体片段渗入籼稻品种桂朝2中培育而成，其每穗粒数显著少于轮回亲本桂朝2。对SIL040和桂朝2杂交产生的F2和F3代进行数量性状基因座（QTL）分析发现，位于第7号染色体短臂上的QTL gpa7是导致这种变异的原因。来自普通野生稻的等位基因会减少每穗粒数。为了精细定位gpa7，利用gpa7两侧的标记构建了一张包含1966个来自SIL040和桂朝2杂交F2植株所构成的高分辨率图谱，并对筛选出的重组体衍生的每个F3家系的主穗结构进行了详细的数量评估。通过两步代换定位，最终将gpa7定位到一个35 kb的区域，该区域在栽培稻中包含5个预测基因。五个穗部性状（穗长、每穗一次枝梗数、每穗二次枝梗数、一次枝梗上的粒数和二次枝梗上的粒数）的QTL均定位在与gpa7相同的区间，这表明该基因座与穗部结构相关，具有多效性。对渗入系SIL040穗部结构的特征分析进一步表明，在从gpa7处的普通野生等位基因驯化到栽培稻的过程中，不仅每穗枝梗数和粒数显著增加，更重要的是，每穗二次枝梗数与总枝梗数的比例以及每穗二次枝梗上的粒数与总粒数的比例也显著增加。所有这些结果都强化了这样一种观点，即gpa7可能在水稻穗部驯化过程中对每穗粒数和每穗二次枝梗比例的调控中发挥重要作用。
