Net work of quantitative trait loci responsible for evolutionary change in rice

宽耕稻和栽培稻在产量和繁殖方式等许多数量性状上存在差异。本研究的目的是利用栽培稻与野生稻的杂交，鉴定这些数量性状（QTL）的位点，并阐明它们在水稻基因组上的网络。1) QTL分析发现140个分子标记在亲本间存在多态性。对上述杂交组合衍生的125个R_6重组自交系（ril）进行了分离分析，并构建了连锁图谱。在各自的ril中测定了30多个数量性状，并利用qGENE分析了分子标记与数量性状的共分离。共检测到22个性状的176个qtl。控制某一性状的qtl广泛分散在不同的染色体上。不同性状的qtl倾向于聚集在12条染色体的几个特定区域上。在标记附近发现这样的聚类，表明品种源性等位基因明显过量。2)落粒选育试验F_3后，按以下方法进行批量繁殖，建立了上述杂交组合的两个杂交群体。一种是粉碎组(S)，在这个组中，粉碎在地上的种子被收集起来用于抚养下一代。另一种是不落粒组（non-shattering group， NS），在这一组中，穗上剩余的种子被收获并用于培养下一代。对所建立的两个F_7群体进行了80个RFLP标记和各种数量性状的检测。S组品系抽穗较晚，种子休眠较强，再生能力较NS组强。部分RFLP的等位基因频率在S组和NS组之间有显著差异。它们大多与负责种子破碎的qtl相关联。上述结果提示了水稻驯化的可能遗传机制。由人类播种和收割所定义的“栽培”一定是一种强烈的自然选择，有利于不碎裂的植物。此外，qtl的连锁或基因簇也有助于在驯化过程中形成性状的自适应关联。少

Wide and cultivated rices differ in many quantitative characters responsible for yielding capacity and propagation method. The objective of this study is to identify loci of those quantitative traits (QTL) and elucidate their network on rice genome using a cross between cultivated rice and a strain of wild rice.1) QTL analysisOne-hundred forty molecular markers were found to be polymorphic between two parents. Segregation of those markers were surveyed among 125 R_6 Recombinant Inbred Lines (RILs) derived from the above cross, and linkage map was constructed. More than 30 quantitative traits were measured in respective RILs, and cosegregation of molecular markers and quantitative traits were analyzed by qGENE.A total of 176 QTLs for 22 traits were detected. QTLs controlling a given trait were widely scattered on different chromosomes. QTLs for different traits tended to cluster on several specific regions of 12 chromosomes. Such clusters were found near the markers which showed signifi … More cant excess of cultivar-derived alleles.2) Selection experiment on seed shatteringTwo hybrid populations of the above cross were established by propagating after F_3 in bulk as follows. One is shattering group (S) in which seeds shattered on the ground were collected and used for raising next generation. The other is non-shattering group (NS) in which seeds remaining on the panicles were harvested and used for raising next generation. Two F_7 populations thus established were examined regarding 80 RFLP markers and various quantitative traits. Lines of S group showed later heading, stronger seed dormancy, stronger regenerating ability than those of NS group. Allele frequencies of some RFLP showed significant difference between S and NS groups. They are mostly linked with QTLs responsible for seed shattering.The above results suggest possible genetic mechanisms of domestication in rice. "Cultivation" defined by seeding and harvesting by man must have worked as strong natural selection favoring non-shattering plants. Further, linkage or gene cluster of QTLs also contributed to forming adaptive association of characters in domestication process. Less