Revisiting rice breeding methods – evaluating the use of rapid generation advance (RGA) for routine rice breeding

Rice production needs to increase in the future in order to meet increasing demands. The development of new improved and higher yielding varieties more quickly will be needed to meet this demand. However, most rice breeding programmes in the world have not changed in several decades. In this article, we revisit the evidence in favour of using rapid generation advance (RGA) as a routine breeding method. We describe preliminary activities at the International Rice Research Institute (IRRI) to re-establish RGA on a large scale as the main breeding method for irrigated rice breeding. We also describe experiences from the early adoption at the Bangladesh Rice Research Institute. Evaluation of RGA breeding lines at IRRI for yield, flowering time and plant height indicated transgressive segregation for all traits. Some RGA lines were also higher yielding than the check varieties. The cost advantages of using RGA compared to the pedigree method were also empirically determined by performing an economic analysis. This indicated that RGA is several times more cost effective and advantages will be realized after 1 year even if facilities need to be built. Based on our experience, and previous independent research empirically testing the RGA method in rice, we recommend that this method should be implemented for routine rice breeding in order to improve breeding efficiency.     

水稻主要农艺性状的QTL分析

【目的】通过对水稻Oryza sativa主要农艺性状的遗传研究,挖掘优异主效QTL,为利用分子标记辅助选择进行高产、优质育种提供理论基础.【方法】以粳稻品系中野1211与籼稻品系中大304构建的重组自交系群体188个家系为试验材料,利用该重组自交系群体构建的含有142个SSR标记分子连锁图,采用区间作图法对抽穗期、单株有效穗数、株高、穗长、每穗实粒数、每穗总粒数、结实率、穗着粒密度、粒长、粒宽、粒形、千粒质量和单株质量13个主要农艺性状进行早、晚季的全基因组QTL定位.【结果和结论】除株高没有检测到相关的QTL之外,其余的每个性状检测到的QTL数目为2~15个.12个性状共检测到73个QTL,分布于水稻的12条染色体上,其中仅在早季能检测到的有34个,仅在晚季能检测到的有23个,两季都能检测到的只有16个.单个QTL的贡献率在5.3%~28.4%之间,其中超过20%以上的有10个.检测到的新位点为12个.早晚两季在多数染色体的多处区段上均检测到多个紧密连锁的QTL.检测到的12个新位点为水稻主要农艺性状的QTL定位增加了新的遗传信息,重复检测到的16个QTL可用于水稻分子标记辅助育种.     

Flooding tolerance of spelt (Triticum spelta L.) compared to wheat (Triticum aestivum L.) – A physiological and genetic approach

In marginal, agroclimatic zones, yield is often affected by flooding, but the effect is much less for winter spelt (Triticum spelta L.) than for winter wheat (Triticum aestivum L.). This study evaluates the reaction of a wheat x spelt population (F₅ RILs of Forno x Oberkulmer) to flooding stress in the early phase of germination. Lines with greater tolerance to 48 h flooding just after imbibition showed less electrolyte leakage (r = -0.79) indicating greater membrane integrity and better survival. Five QTL explaining 40.6% of the phenotypic variance for survival to flooding were found, and localized on the chromosomes 2B, 3B,5A, and 7S. The tolerance to 48 h flooding four days after sowing was best correlated with the mean germination time (r = 0.8), indicating that the plants with a fast coleoptile growth during flooding are less susceptible to flooding. Ten QTL were found for seedling growth index after flooding explaining 35.5% of the phenotypic variance. They were localized on chromosomes 2A, 2B, 2D, 3A, 4B, 5A, 5B, 6A, and 7S. Standard varieties of spelt and wheat showed the same tolerance characteristics. The possibility to use marker assisted selection for flooding tolerance is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

水稻蛋白质含量NIR模型适配范围的研究

【目的】比较不同类型样品建立水稻蛋白质近红外模型的效果和适配范围。【方法】通过对178份来自“II-32B/岳早籼6号”的重组自交系和496份水稻品种的近红外反射光谱的比较分析，选择其中59个株系和76份品种作为建模样品，采用偏最小二乘法建立基于品种、重组自交系和混合样品的3个蛋白质含量回归模型。【结果】经模型内部交叉验证和对模型外部重组自交系和品种样品的验证结果的比较分析，发现基于分离群体的模型因蛋白质含量范围较窄，样品来源较单一，适应范围仅局限于本群体内样品蛋白质含量预测，而品种和混合模型对群体和品种样品都表现出良好的适应能力，交叉验证决定系数大于0.90，外部验证决定系数大于0.89, 本试验可为近红外建模的样本集选择提供良好的指导意义。【结论】不同类型样品对建模效果有显著影响，品种模型和混合模型的适配范围显著大于群体模型，研究结果不能支持用背景变异较小的样品建立较高精度回归模型的设想。     

Comparison of Near Infrared Spectroscopy Models for Determining Protein and Amylose Contents Between Calibration Samples of Recombinant Inbred Lines and Conventional Varieties of Rice

The near infrared spectra of 178 recombinant inbred lines （RILs） from the cross of Ⅱ-32B/Yuezaoxian 6 （YZX6） and 511 varieties in rice were acquired. A total of 80 RILs and 96 cultivars were selected as modeling samples by comparing the spectra similarity primarily. Three partial least square （PLS） regression models were developed, based on the RILs （RIL-model）, the varieties （Var-model） and their mixture （Mix-model）, for protein content （PC） and amylose content （AC）, respectively. Cross validation and outer prediction showed that the models were largely influenced by the range and distribution of modeling samples. The regression model of PC based on the cultivars and the model of AC based on RILs had higher coefficient of determination （r^2 ≥ 0.9） and lower root mean square error of cross validation （RMSECVs）. The disadvantages of RIL samples for PC model and variety samples for AC model were probably caused by the narrow range of variance. Aberrant predictions were obtained for outer sample with PC or AC outside the range or within the distribution gap of modeling samples. The Mix-models gave more reliable prediction as the distribution of RIL and variety modeling samples were complementary to each other.     

3个小麦重组自交系群体抗赤霉病QTLs的SSR分析

 对3个重组自交系群体(RILs)苏麦3号/Alondra F_7、望水白/Alondra F_8、894037/Alondra F_8进行SSR分析,用单个标记方差及回归分析方法,结合接种鉴定资料,寻找与抗赤霉病性有关的的SSR分子标记。结果显示,在这3个抗病亲本的3B染色体上都存在一个主效抗赤霉病QTL,分别能解释2.6％～6.7％(苏麦3号)、47.4％(894037)、8.9％～27.0％(望水白)的抗性表型变异。在其它一些染色体上也发现一些微效QTLs,如2D、4B、4D、7A、6B染色体上,其中存在于4B染色体上的一个QTL来源于感病品种Alondra。在望水白/Alondra F_8群体中检测到了1个存在于2D染色体的抗赤霉病QTL,来源于抗病品种望水白,而在894037/Alondra F_8群体上检测到的1个存在于2D染色体的抗赤霉病QTL,则来源于感病品种Alondra,对其真实性将进一步研究。     

利用重组自交系高密度遗传图谱定位水稻芽期耐冷QTL

为定位水稻芽期耐冷QTL,本实验以双季超级稻品种‘五丰优T025’的双亲‘五丰B’和‘昌恢T025’杂交衍生的重组自交系(recombinant inbred lines, RILs)群体为材料,对10℃低温处理的水稻幼芽的存活率、根数、根长和芽长进行了测定。利用QTL Icimapping v4.2软件,共检测到3个控制芽期耐冷性QTL：qRL1、qRL2和qBL6,分别位于第1、2、6染色体上,LOD值分别为2.98,2.51和5.26,分别解释表型变异的10.54%,8.67%和14.04%,其增效等位基因均来自于亲本‘昌恢T025’。这些QTL定位在6.75k~40.05 kb染色体区间,为后续利用这些QTL进行分子标记辅助,选育芽期耐冷籼稻新品种奠定了基础。此外,检测到13对影响水稻芽期耐冷上位性互作QTL,分布在所有12条染色体,其中第3染色体与第8染色体之间互作位点可解释的表型变异率达到21.77%,表明上位性互作QTL在调控水稻芽期耐冷过程中也发挥了重要作用。     

稻米垩白QTL定位分析

该研究以高垩白度品种V20B和低垩白度品种CPSLOi7作为亲本,构建150个V20B/CPSLO 17重组自交家系(RIL)为作图群体,进行稻米垩白QTL检测及其遗传效应分析.以垩白度作为衡量稻米垩白高低的表型数据,结合SLAF标签构建的分子连锁图谱,运用MapQTL5软件检测到4个稻米垩白QTL,分别命名为qC-5a、qC-5b、qC-5c和qC-5d.分析结果表明这4个QTL的LOD值分别为4.02、4.09、3.94和4.1,对表型变异的解释率分别为11.6％、11.8％、11.2％和11.8％,且这4个QTL抗性等位基因都来自低垩白亲本CPSLO17.     

大拇指矮×偃展1号重组自交系群体主要农艺性状遗传分析

对大拇指矮和偃展1号构建的重组自交系群体（RILs）后代主要农艺性状进行遗传分析,并调查其抽穗期、开花期、株高、穗长、单株穗数、单穗小穗数、单穗结实小穗数、穗粒数、千粒重9个农艺性状。结果表明,上述性状在重组自交系后代中表现出双向超亲分离,根据抽穗期、单株穗数、单穗结实小穗数、穗粒数和千粒重这5个重要农艺性状进行优良株系的筛选,均得到超高亲的株系,为进一步利用该重组自交系群体进行小麦品种改良提供了重要材料。