Zhang Yushan, Luo Lijun, Xu Caiguo, Zhang Qifa, Xing Yongzhong
National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China.
Theor Appl Genet. 2006 Jul;113(2):361-8. doi: 10.1007/s00122-006-0305-3. Epub 2006 Jun 2.
Near-isogenic lines (NILs) are ideal materials for precise estimation of quantitative trait loci (QTL) effects and map-based gene isolation. With the completion of the rice genome sequence, QTL isolation based on NILs is becoming a routine. In this study, a trait-performance derived NIL strategy was adopted to develop NILs. Two plants were identified within one inbred line of recombinant inbred lines (RILs, F(7) generation), exhibiting a significant difference in panicle size. By marker screening of the whole genome the genetic background of the two plants was estimated to be 98.7% identical. These two plants were selected as parents to produce a near-isogenic F(2) (NIL-F(2)) population, consisting of 125 individuals, in which spikelets per panicle (SPP), grains per panicle (GPP), heading date (HD) and plant height (PH) were recorded. These four traits expressed discontinuous or bimodal distribution in the NIL-F(2) population and followed the expected segregation ratios for a single Mendelian factor by progeny tests. A partial dominant QTL for the four traits was mapped to the same interval flanked by RM310 and RM126 on chromosome 8. The QTL region explained 83.0, 80.2, 94.9 and 93.8% of trait variation of SPP, GPP, HD and PH in the progenies, respectively. Progeny tests also confirmed co-segregation of QTL for the four traits, tall plants consistently flowering late and carrying large panicles. Different NILs development strategies are discussed.
近等基因系（NILs）是精确估计数量性状位点（QTL）效应和基于图谱的基因分离的理想材料。随着水稻基因组序列的完成，基于NILs的QTL分离正变得常规化。在本研究中，采用了一种基于性状表现的NIL策略来开发NILs。在一个重组自交系（RILs，F(7)代）的自交系中鉴定出两株植物，它们在穗大小上表现出显著差异。通过对全基因组进行标记筛选，估计这两株植物的遗传背景相似度为98.7%。选择这两株植物作为亲本，产生了一个由125个个体组成的近等基因F(2)（NIL-F(2)）群体，记录了其中每穗小穗数（SPP）、每穗粒数（GPP）、抽穗期（HD）和株高（PH）。这四个性状在NIL-F(2)群体中表现出不连续或双峰分布，通过子代测验遵循单个孟德尔因子的预期分离比。一个控制这四个性状的部分显性QTL被定位到第8号染色体上RM310和RM126两侧的同一区间。该QTL区域分别解释了子代中SPP、GPP、HD和PH性状变异的83.0%、80.2%、94.9%和93.8%。子代测验还证实了这四个性状的QTL共分离，高植株总是开花晚且穗大。文中讨论了不同的NILs开发策略。
