Components of heterosis for growth traits and litter size in line crosses of mice after long-term selection

Strains selected for 54 generations for large 8-week weight (N8, S8), for small weight (N6, S6), for high 3–5-week gain and low 8-week weight (N1) as well as unselected randomly mated control strains (N9, S9) were crossed, and F ₁, F ₂ and both back crosses created. N strains are derived from a NMRI base, S strains from a synthetic four-way cross among inbred lines. Heterosis for 8-week weight (8-ww) was some 6%, but 30% for 3–5-week gain and it was on average negative (22%) for 5–8-week gain. When epistatic effects were taken into account, it appeared that heterosis for 8-ww was largely due to beneficial effects of non-parental gene combinations, i.e. additive × additive epistatic effects were negative. These non-parental combinations neutralized the mostly negative dominance effects. The latter were mostly positive for early gain but in all 9 line crosses negative for late gain. The digenic effects of the non-parental origin were not large enough to balance the negative dominance effects for late gain, so that heterosis was negative. It appears therefore that early and late gain are affected by different sets of genes. Maternal additive effects on 8-ww and early gain are smaller than direct additive effects but mostly of similar sign. For late gain there appears to be no connection with direct additive effects. Direct litter heterosis was almost 50% but much of this was due to positively acting recombinational gene combinations, while direct litter dominance was mostly negative. Maternal additive effects on litter size differed depending on whether they were estimated from dams with crossbred or with purebred litter. Heterosis was small in crosses between control strains. Heterosis caused by recombinant gene pairs should be amenable to improvement by selection.     

Analysis of mode of inheritance of Fusarium wilt resistance in castor (Ricinus communis L.)

Castor (Ricinus communis L.) is an important industrial oilseed crop grown worldwide. Wilt caused by Fusarium oxysporum f.sp. ricini is a devastating disease in castor. The inheritance mode of wilt resistance was investigated. The F₁, F₂ and backcross generations of four crosses involving four resistant and three susceptible parents were developed. The role of digenic (R¹ and R²) epistatic interactions on wilt resistance was confirmed. The 15 : 1, 9 : 7 and 13 : 3 ratios indicated duplicate dominant, duplicate recessive and dominant and recessive epistatic interactions, respectively. Castor parents used in the crosses exhibited varied inheritance modes. All generations of a cross exhibited similar inheritance mode when parents were comparable. However, generations varied in inheritance mode when parents were not comparable in inheritance mode. These results would have practical interest when decisions are required regarding the choice of parents and methodology in resistance and hybrid breeding. The results also provided a basis for investigating molecular genetics of wilt resistance mechanisms.     

QTL epistatic analysis for yield components with single‐segment substitution lines in rice

Epistasis is an important genetic component in determining the phenotype of complex quantitative trait. In this article, 12 single‐locus heterozygotes and 66 double‐locus heterozygotes were developed and then were applied to assay QTL epistasis for four yield‐associated traits under two planting densities. Of 264 (66 × 4) tested interactions, 130 (49.2%) were significant at the p < .05 level. QTL with the same effect directions had higher probabilities of interactions. The negative epistasis at least included one positive effect QTL but the positive epistasis one negative QTL. The detected epistasis was sensitive to planting density. Epistasis also exhibited pleiotropic effects.     

8种水旱环境下2个玉米群体穗部性状QTL间的上位性及环境互作效应分析

深入剖析干旱胁迫条件下玉米穗部性状的遗传机制可为玉米抗旱高产分子育种提供参考依据。以大穗型旱敏感自交系TS141为共同亲本,分别与小穗型强抗旱自交系廊黄和昌7-2杂交,构建了含有202个(LTPOP)和218个(CTPOP)家系的F2:3群体,在8种水旱环境下进行单穗重、穗轴重、穗粒重、百粒重、出籽率及穗长等6个穗部性状的表型鉴定,并采用复合区间作图法(CIM)和基于混合线性模型的复合区间作图法(MCIM)对其进行单环境和多环境联合数量性状位点(QTL)分析。结果表明,采用CIM法,单环境下在2套F2:3群体间检测到62个穗部性状QTL,其中干旱胁迫环境下检测到38个QTL,进一步在2套F2:3群体多个干旱胁迫环境下检测到10个稳定表达的QTL (sQTL),分别位于Bin 1.01–1.03、Bin 1.03–1.04、Bin 1.05、Bin 1.07、Bin 1.07–1.08、Bin 2.04、Bin 4.08、Bin 5.06–5.07、Bin6.05和Bin 9.04–9.06。采用MCIM法,联合分析定位到54个穗部性状联合QTL,其中24个表现显著的QTL与环境互作(QTL×E), 17对参与了显著的加性与加性/显性(AA/AD)上位性互作,其表型贡献率较低。这些研究结果可为系统地剖析玉米穗部性状的分子遗传机制提供理论依据;且这2套F2:3群体多个环境下检测到的sQTL可作为穗部性状改良的重要候选染色体区段,用于图位克隆或抗旱高产分子育种,但要注重环境及上位性互作效应的影响。     

甘蓝型油菜隐性上位细胞核雄性不育三系的转育方法

对甘蓝型油菜隐性上位细胞核雄性不育纯合两型系、临保系和全不育系的转育方法进行了介绍。其要点是先转育隐性上位细胞核雄性不育纯合两型系,然后再通过回交转育主要农艺性状与纯合两型系相近或完全一致的相应的全不育临时保持系。具有方法简便,工作量小,见效快等优点。该方法正在应用于对REGMS118A类型细胞核雄性不育系的转育改良实践中。     

Dissection of additive,epistatic and QTL × environment effects involved in oil content variations in rapeseed

In this study, we observed variation of rapeseed oil content in SG population across 11 environments. A joint mapping was conducted to detect the quantitative trait loci (QTL) involved in oil content variation. We examined additive main (a), epistatic effects (aa) and their interactions with environments (QE). Apart from a of 12 QTL (collectively to 6.74% of oil content), aa of 18 locus pairs contributed to 5.36% difference, explaining 45.3% of phenotypic variation in the population. Moreover, 28 QE interactions contributed to a change of 1.55% in oil content in each environment, accounting for 13.3% phenotypic variation. Two environmentally sensitive QTL (OilC2 and OilC8‐1) exhibited a small a (0.17) but strong ae (0.41 and 0.32 averagely). These two QTL were also frequently involved in epistatic interactions. However, two major QTL (OilA7 and OilC8‐2) showed few QE and uninvolved in epistasis. In conclusion, a and aa were the dominant contributors to oil content in rapeseed, while QE accounted for 10‐15% of variation. The results suggest OilA7 and OilC8‐2 are potential candidates for breeding utilization and gene cloning.     

数量性状全基因组关联分析中上位效应遗传位点检测方法研究进展

数量性状的表型变异受到大量效应微小的遗传位点和诸多环境因素的共同作用,但在数量性状的遗传研究领域,关于不同遗传位点之间加性效应与上位效应相对重要性的认识却存在着分歧。近年来,伴随着全基因组关联分析在人类及家养动物数量性状研究中的发展,在全基因组关联分析的框架内进行上位效应遗传位点的检测越发受到重视。文章以遗传力失踪问题为出发点,首先综述了标记-QTL连锁分析和GWAS框架下传统上位效应遗传位点的检测方法,然后对基于表型方差同质性检验和广义线性混合模型方法的上位效应统计推断以及混杂因素的处理方法进行了总结与梳理,旨在为数量性状全基因规模上位效应的相关研究提供理论参考。     

甘蓝型油菜隐性核不育的遗传与应用研究

对由二对隐性重叠不育基因与一对隐性上位抑制基因控制的三隐性核不育进行的研究表明:1该不育系不育性彻底,基本上不受环境影响而出现微粉影响制种纯度,且制种容易;2在不育系的选育中纯合两型系是基础,临保系的筛选是关键,为了加快育种进程,要在分析基因型及其杂交后代出现比率的基础上选择最佳的途径;3三隐性核不育的恢复源极广,优势组合选择的范围大。4筛选较多临保系可丰富不育系的遗传基础。由于三隐性核不育系育性彻底,恢复源广,制种容易,因而具有广阔的应用前景。     

水稻耐辐射损伤的QTL分析

利用水稻品种珍汕97B/密阳46所构建的RIL群体及其遗传图谱, 以350和550Gy γ射线辐照成熟种子,以相对发芽率和相对成苗率作为考察其耐辐射损伤指标,进行QTL加性效应和上位性效应分析。结果表明,RIL群体受不同剂量辐照后,株系间表现出耐辐射损伤的差异。350Gy剂量处理共检测到2个耐辐射的加性效应QTL,其中qRR(g)8-1（相对发芽率为指标）有效基因来自于父本,其遗传贡献率为653%;qRR(s)2-2（相对成苗率为指标）有效基因来自于母本,其遗传贡献率为1281%。550Gy剂量处理共检测到4个耐辐射的加性效应QTL,其中以相对发芽率为指标,检测到的qRR(g)1-2和 qRR(g)8-2,其有效基因分别来自于母本和父本,共可解释1438%变异;以相对成苗率为指标,则检测到qRR(s)5-2和qRR(s)10,共解释1965%变异。在不同剂量处理下,还检测到9对双基因相互作用。比较表明,水稻耐辐射损伤的QTL表达可能与辐照剂量有关。     

甘蓝型油菜隐性上位核不育×恢复系遗传判别

利用定性分析方法,对甘蓝型油菜隐性上位核不育×恢复系的各种遗传情况进行鉴别。结果发现可以区分为6种类型,每种类型有3种遗传情况。同时对隐性上位核不育的遗传行为方式进行了讨论。