根据杂种优势值划分粳型水稻杂种优势生态型

利用9个不同生态类型的50份水稻亲本材料,以生态型为单位进行双列杂交,配制杂交组合.研究杂种一代的对照优势和超亲优势.以杂种优势值作为划分优势生态型的依据.结果表明:西北粳、台湾粳、日本粳和韩国稻为优势生态类型.根据各生态型间的杂种优势值可以推测台湾粳、日本粳和韩国粳具有穗数上的优势基因,西北粳具有粒数上的优势基因,非洲IRAT粳具有粒重上的优势基因.最佳优势组配模式为韩国粳×日本粳、西北粳×美国粳和台湾粳×日本粳.杂种优势与亲本形态指数差异的相关分析表明,各生态型间形态指数差异与其F1杂种优势相关不显著.表明依据亲本形态差异不能预测杂种优势.     

多子房性状应用于杂种小麦的研究——Ⅱ．多子房小麦的杂种优势与利用

利用3个多子房小麦与8个普通小麦品种杂交后获得的24个杂种及其相应的亲本材料,对多子房小麦的杂种优势与利用进行了研究。结果表明,F1各性状的杂种优势依次为株高＞穗粒数＞单株产量＞千粒重。单株产量有较强的杂种优势,18个组合超双亲均值,平均均产32．71％,12个组合有超标正优势,幅度为3．41－42．84％。多子房小麦杂种优势的主要表现是穗粒数增多,其生产应用还应注意加强对子房小麦其它农艺性状的改良。     

Ven、K型小麦雄性不育系春性F1杂种的优势表现及与叶绿素含量和同工酶谱的关系

利用Ven、K型小麦雄性不育系与北方春性普通小麦杂交,研究了Ven、K型春性F1杂种的优势表现及其与叶绿素含量、同工酶谱的关系.结果表明Ven型和K型杂种F1存在显著的个体杂种优势,在主要农艺性状中尤其以单株穗数、千粒重、单株生产力的杂种优势明显,其中单株穗数对单株生产力的贡献最大;相关分析表明单株生产力与单株穗数呈正相关,相关系数为0.7122;与每穗粒数和千粒重的相关系数分别为-0.1183和0.4941.灌浆期旗叶、倒二叶叶绿素含量与千粒重的相关性最大,呈正相关.杂种F1优势强的组合其种子和苗期的过氧化物同工酶和酯酶的酶谱一般呈双亲互补型或“杂种型”酶带,该特征可作为杂种优势预测的指标.     

玉米杂种与亲本穗分化期功能叶基因差异表达与杂种优势

为探讨玉米杂种优势的分子机理,以10个玉米自交系及其组配的38个杂交种为材料,利用cDNA-AFLP技术,分析杂种与亲本在玉米雌穗小穗分化期功能叶片的基因差异表达类型与主要农艺性状的杂种表现及杂种优势的关系。研究表明：（1）杂种的基因相对于其双亲,存在质和量的表达差异,其中质的差异表达类型包括：单亲沉默表达,双亲沉默表达,亲本显性表达和杂种特异表达等类型。（2）在雌穗小穗分化期,同一差异表达类型中不同杂交组合间差异很大;从总体平均看,杂种特异表达类型占25.22%,亲本显性表达类型占21.46%,双亲沉默表达类型占8.27%,单亲沉默表达类型占33.49%。（3）单亲沉默表达与株高的杂种表现呈显著正相关;双亲沉默表达与穗粗的杂种优势呈显著负相关,显性表达与行粒数和单株粒重的杂种优势呈显著负相关,其余表达类型与所有农艺性状杂种表现及杂种优势均不相关,并对结果进行了讨论。     

Ven、K型小麦雄性不育系春性F1杂种的优势表现及与叶绿素含量和同工酶谱的关系

利用Ven、K型小麦雄性不育系与北方春性普通小麦杂交,研究了Ven、K型春性F1杂种的优势表现及其与叶绿素含量、同工酶谱的关系。结果表明：Ven型和K型杂种F1存在显著的个体杂种优质,在主要农艺性状中尤其以单株穗数、千粒重、单株生产力的杂种优势明显,其中单株穗数对单株生产力的贡献最大;相关分析表明：单株生产力与单株穗数呈正相关,相关系数为0.7122;与每穗粒数和千粒重的相关系数分别为－0.1183和0.4941。灌浆期旗叶、倒二叶叶绿素含量与千粒重的相关性最大,呈正相关。杂种F1优势强的组合其种子和苗期的过氧化物同工酶和酯酶的酶谱一般呈双亲互补型或“杂种型”酶带,该特征可作为杂种优势预测的指标。     

不结球白菜杂种优势及相关分析

以4个不结球白菜不育系与4个父本系以NCⅡ法配制16个杂交组合,研究了16个F1组合的杂种优势表现及其与亲本之间的相关关系,同时对性状间的遗传相关进行分析.结果表明:不结球白菜产量性状杂种优势＞农艺性状杂种优势＞光合性状杂种优势＞品质性状杂种优势.产量性状以超亲优势为主,农艺性状和光合性状以中亲优势为主,品质性状中可溶性糖含量以中亲优势为主, Vc含量和蛋白质含量均为弱的负向优势.亲子相关分析表明,一些性状F1与中亲值、低亲值或高亲值显著相关,因此在亲本选配时,注意亲本差异的同时,中亲值特别是低亲值不能过低,尤其是品质性状.性状间相关分析显示,光合性状与产量性状显著正相关,说明F1高效的光合同化作用是杂种高产的基础.品质性状中,可溶性糖含量与产量显著正相关,但Vc和蛋白质含量与产量负相关,在亲本选配时还应注意二者的协调.     

普通小麦不同优势杂交种及其亲本苗期根系基因的差异表达

为探讨小麦(Triticum aestivum L.)杂种优势形成的分子机理,选用普通小麦品种(系)3338、6554和2410TD及其强优势杂种A(3338×6654)和无优势杂种B(2410TD×6554),采用mRNA差异显示技术,对生长至三叶一心的根系(初生根)基因表达差异进行了比较研究.结果发现,小麦杂种一代苗期根系基因表达较亲本明显不同,表现为数量水平和质量水平上的差异,且差异表达基因的数目远高于我们以苗期叶片为材料的研究结果,表明小麦杂交种与其亲本间的基因差异表达与所研究的组织和器官有关.比较分析发现,在强优势杂种组合A中,超亲表达和偏高亲表达基因所占比例均明显高于无优势杂种组合B.以家族特异基因替代随机引物进行的差异显示结果表明,MADS-box家族基因在小麦杂交种和亲本苗期根系中存在着显著的表达差异,且差异表达类型以杂种特异表达和亲本基因在杂种一代沉默为主,说明MADS-box家族基因可能与小麦的杂种优势形成具有重要关系.对杂种和亲本基因表达差异与杂种优势的关系进行了分析和讨论.     

六倍体小黑麦T型细胞质雄性不育体系杂种优势与配合力的研究

用具提莫菲维小麦细胞质的六倍体小黑麦的3个不育系和3个恢复系作为亲本,进行3×3不完全双列杂交,对所组配的F1代8个农艺性状的杂种优势分析结果表明,除千粒重外,其余性状出现正向超亲优势的组合较少,多数呈低亲或中亲遗传,且各组合间的差异比较显著。配合力分析表明,一般配合力与特殊配合力的方差均达到了显著水平,F1各性状均受基因加性效应和非加性效应共同作用;从总体上看,不育系A1、A2及恢复系R1、R2的一般配合力良好,其配制的组合优势较强,具一定的利用价值。对一般配合力与亲本表型值进行了相关分析,二者无显著的相关关系。     

RAPD分子标记与玉米杂种产量优势预测的研究

以２４个优良玉米自交系统ＮＣⅡ设计组配成１４３个单杂交种为材料，利用的ＲＡＰＤ分子标记技术研究玉米杂种优势群划分，遗传距离与特殊配合力，杂种产量，杂种产量优势的联系。结果表明：（１）ＲＡＰＤ技术可用于玉米杂种优势群划分。（２）亲本遗传距离杂种产量优势，杂种产量，特殊配合畋有一定相关关系，但决定系数很小，分别是１０％，１０％，１５％，利用ＲＡＰＤ技术预测杂种优势，杂种产量作用有限，应进一步研究与杂     

普通小麦不同优势杂交种及其亲本苗期根系基因的差异表达

为探讨小麦 (TriticumaestivumL .)杂种优势形成的分子机理 ,选用普通小麦品种 (系 ) 3338、6 5 5 4和 2 410TD及其强优势杂种A(3338× 6 6 5 4)和无优势杂种B(2 410TD× 6 5 5 4) ,采用mRNA差异显示技术 ,对生长至三叶一心的根系 (初生根 )基因表达差异进行了比较研究。结果发现 ,小麦杂种一代苗期根系基因表达较亲本明显不同 ,表现为数量水平和质量水平上的差异 ,且差异表达基因的数目远高于我们以苗期叶片为材料的研究结果 ,表明小麦杂交种与其亲本间的基因差异表达与所研究的组织和器官有关。比较分析发现 ,在强优势杂种组合A中 ,超亲表达和偏高亲表达基因所占比例均明显高于无优势杂种组合B。以家族特异基因替代随机引物进行的差异显示结果表明 ,MADS_box家族基因在小麦杂交种和亲本苗期根系中存在着显著的表达差异 ,且差异表达类型以杂种特异表达和亲本基因在杂种一代沉默为主 ,说明MADS_box家族基因可能与小麦的杂种优势形成具有重要关系。对杂种和亲本基因表达差异与杂种优势的关系进行了分析和讨论     

Intra-specific hybridization: generator of genetic diversification and heterosis in Andrographis paniculata Nees. A bridge from extinction to survival

Andrographis paniculata (AP) has been stated as a low-diverse, endangered and red-listed plant species. Self-pollinated mating system, being an introduced species and experiencing a bottleneck as well as over exploitation cause such a consequence. Inter and intra-specific hybridizations have been suggested as essential techniques for generating genetic diversity. To test the effect of intra-specific hybridization on diversification and heterosis of AP, seven accessions were outcrossed manually in all 21 possible combinations. Three types of markers including morphological, phytochemical and RAPD markers were employed to evaluate the mentioned hypothesis. The results revealed that hybridization acted as a powerful engine for diversification of AP as it caused heterotic expression of the studied traits, simultaneously. Initially, it seems that additive and non-additive gene effects both can be considered as the genetic basis of heterosis in AP for the investigated traits. Agronomic and morphological traits were differentiated from each other, while positive heterosis was recorded mainly for agronomic traits but not for the morphological traits. Intra-specific hybridization increased the genetic diversity in AP population. Nevertheless, a part of this variation could also be attributed to the negative heterosis. The current exploration demonstrated the first ever conducted manual intra-specific hybridization among AP accessions in a mass scale. However, the 17 RAPD primers produced a monomorph pattern, but perhaps increasing the number of markers can feature a new genetic profile in this plant.     

Heterosis studies for yield and its components in bread wheat over environments

A set of diallel crosses involving 10 parents was made to have information on the extent of heterosis over mid-parent and better parent and inbreeding depression for yield and yield contributing characters under three different environments. Marked heterobeltiosis for grain yield and its important components were observed. For grain yield, 83 crosses showed significant positive heterobeltiosis in all the three sowing dates, however, twenty crosses showed significant consistent heterobeltiosis for grain yield per plant over all the three environments. The maximum heterobeltiosis for grain yield per plant observed was 50.94% (Raj 3765 x HD 2285), 121.08% (PBW 373 x HD 2329) and 93.96% (PBW 373 x HD 2329) under early, normal and late sowing conditions, respectively. Cross PBW 373 x HD 2329 in both early and normal plantings and cross Raj 3765 x HD 2285 under late planting were observed most heterotic for grain yield. The crosses showing heterosis for grain yield were not heterotic for all the characters. Heterosis for grain yield per spike followed by tillers per plant and 1000-grain weight was independently associated with heterosis for grain yield in early and normal plantings. However, heterosis for grain yield per spike, dwarf plant height and tillers per plant contributed maximum towards yield heterosis. Significant inbreeding depression was recorded frequently for yield and yield contributing traits, however, in a few traits it was observed significant negative indicated that F(2) was superior to F(1) considered desirable combination for trait(s). The study reveals good scope for commercial exploitation of heterosis as well as isolation of pure lines among the progenies of heterotic F(1) for improvement of yield levels in bread wheat.     

The metabolomic landscape of rice heterosis highlights pathway biomarkers for predicting complex phenotypes

Understanding the molecular mechanisms underlying complex phenotypes requires systematic analyses of complicated metabolic networks and contributes to improvements in the breeding efficiency of staple cereal crops and diagnostic accuracy for human diseases. Here, we selected rice (Oryza sativa) heterosis as a complex phenotype and investigated the mechanisms of both vegetative and reproductive traits using an untargeted metabolomics strategy. Heterosis-associated analytes were identified, and the overlapping analytes were shown to underlie the association patterns for six agronomic traits. The heterosis-associated analytes of four yield components and plant height collectively contributed to yield heterosis, and the degree of contribution differed among the five traits. We performed dysregulated network analyses of the high- and low-better parent heterosis hybrids and found multiple types of metabolic pathways involved in heterosis. The metabolite levels of the significantly enriched pathways (especially those from amino acid and carbohydrate metabolism) were predictive of yield heterosis (area under the curve = 0.907 with 10 features), and the predictability of these pathway biomarkers was validated with hybrids across environments and populations. Our findings elucidate the metabolomic landscape of rice heterosis and highlight the potential application of pathway biomarkers in achieving accurate predictions of complex phenotypes.

Specific metabolic pathways (especially those from amino acid and carbohydrate metabolism) underlie heterosis of six agronomic traits in rice.     

白菜类蔬菜资源的农艺性状分析及应用研究

通过对505份白菜类蔬菜：大白菜、小白菜和紫菜薹的田间观察鉴定,同时抽取其中有代表性的材料90份(每类型30份)以白菜型油菜(30份)为对照进行农艺性状考察,结果显示：白菜类蔬菜种质资源中存在有符合油莱育种目标的特异性状,如特早熟型、白花、黄籽、抗寒型、矮杆、多分枝、多角果、大粒、特殊不育类型等。从变异幅度看,白菜类蔬菜资源的大多数农艺性状的变异系数大于白菜型油菜。同时通过核心种质资源构建,从120份材料中筛选出40份(每类10份)进行系统聚类分析,结果将40份供试材料共分为12类,其中紫菜薹和白菜型油莱各聚为一类,而小白菜和大白菜的聚类结果比较复杂,类型较多,这说明白菜类蔬菜资源与普通白菜型油菜的亲缘关系较远,遗传背景差异较大,用它们测配杂交组合优势明显,这一点在实际应用中已被证实。同时通过对白菜类蔬菜不育系和甘蓝型油菜不育系接受外界花粉能力的比较得到,白菜类蔬菜不育系的异交率极高。这一特性为其杂交优势利用提供了科学依据。     

Identification of heterotic loci associated with yield-related traits in Chinese common wild rice (Oryza rufipogon Griff.)

Many rice breeding programs have currently reached yield plateaus as a result of limited genetic variability in parental strains. Dongxiang common wild rice (Oryza rufipogon Griff.) is the progenitor of cultivated rice (Oryza sativa L.) and serves as an important gene pool for the genetic improvement of rice cultivars. In this study, heterotic loci (HLs) associated with six yield-related traits were identified in wild and cultivated rice and investigated using a set of 265 introgression lines (ILs) of O. rufipogon Griff. in the background of the Indica high-yielding cultivar Guichao 2 (O. sativa L.). Forty-two HLs were detected by a single point analysis of mid-parent heterosis values from test cross F₁ offspring, and 30 (71.5%) of these HLs showed significantly positive effects, consistent with the superiority shown by the F₁ test cross population in the six yield-related traits under study. Genetic mapping of hsp11, a locus responsible for the number of spikelets per panicle, confirmed the utility of these HLs. The results indicate that favorable HLs capable of improving agronomic traits are available. The identification of HLs between wild rice and cultivated rice could lead to a new strategy for the application of heterosis in rice breeding.     

小麦品种间杂种优势与配合力分析

对９个冬小麦亲本１３个性状的杂种优势分析表明,产量性状的杂种优势较强,品质性状的杂种优势较弱。籽粒蛋白质含量、硬度和湿面筋、干面筋含量偏低亲或中亲遗传,沉淀值偏高遗传,存在较明显杂种优势（１６．１－２３．８％）。     

A systematic dissection in oilseed rape provides insights into the genetic architecture and molecular mechanism of yield heterosis

Heterosis refers to the better performance of cross progeny compared with inbred parents, and its utilization contributes greatly to agricultural production. Several hypotheses have been proposed to explain heterosis mainly including dominance, over-dominance (or pseudo-overdominance) and epistasis. However, systematic dissection and verification of these hypotheses are rarely documented. Here, comparison of heterosis level across different traits showed that the strong heterosis of composite traits (such as yield) could be attributed to the multiplicative effects of moderate heterosis of component traits, whether at the genome or locus level. Yield heterosis was regulated by a complex trait-QTL network that was characterized by obvious centre-periphery structure, hub QTL, complex up/downstream and positive/negative feedback relationships. More importantly, we showed that better-parent heterosis on yield could be produced in a cross of two near-isogenic lines by the pyramiding and complementation of two major heterotic QTL showing partial-dominance on yield components. The causal gene (BnaA9.CYP78A9) of QC14 was identified, and its heterotic effect results from the heterozygous status of a CACTA-like transposable element in its upstream regulatory region, which led to partial dominance at expression and auxin levels, thus resulting in non-additive expression of downstream responsive genes involved in cell cycle and proliferation, eventually leading to the heterosis of cell number. Taken together, the results at the phenotypic, genetic and molecular levels were highly consistent, which demonstrated that the pyramiding effect of heterotic QTL and the multiplicative effect of individual component traits could well explain substantial parts of yield heterosis in oilseed rape. These results provide in-depth insights into the genetic architecture and molecular mechanism of yield heterosis.     

Genetic distance and heterosis in Indian mustard: developmental isozymes as indicators of genetic relationships

The use of isozymes as indicators of genetic diversity and as markers for the selection of agronomic traits has been proposed in different crop species. The present investigation was conducted to study the use of isozyme-derived genetic distance between parents in predicting the F₁ heterosis in Indian mustard. In addition, the interaction of isozyme-based diversity with quantitative trait and pedigree-based diversity measures, and its role in predicting hybrid heterosis has also been examined. Sixteen Indian mustard lines and their 48 crosses (12 × 4, line x tester crossing) were evaluated over two environments for isozyme and quantitative morphological characters. The results from this study suggest that the heterotic response to isozymic changes is more responsive in crosses derived from morphologically and pedigree-wise related parents in comparison to crosses derived from unrelated parents. It was possible to improve heterosis predictions by partitioning the isozyme-based genetic distance into general genetic distance and specific genetic distance and correlating the latter with the specific combining ability of morphological traits. The possible reasons for these observations are discussed.     

Assembly of yield heterosis of an elite rice hybrid is promising by manipulating dominant quantitative trait loci

In the past, rice hybrids with strong heterosis have been obtained empirically, by developing and testing thousands of combinations. Here, we aimed to determine whether heterosis of an elite hybrid could be achieved by manipulating major quantitative trait loci. We used 202 chromosome segment substitution lines from the elite hybrid Shanyou 63 to evaluate single segment heterosis (SSH) of yield per plant and identify heterotic loci. All nine detected heterotic loci acted in a dominant fashion, and no SSH exhibited overdominance. Functional alleles of key yield-related genes Ghd7, Ghd7.1, Hd1, and GS3 were dispersed in both parents. No functional alleles of three investigated genes were expressed at higher levels in the hybrids than in the more desirable parents. A hybrid pyramiding eight heterotic loci in the female parent Zhenshan 97 background had a comparable yield to Shanyou 63 and much higher yield than Zhenshan 97. Five hybrids pyramiding eight or nine heterotic loci in the combined parental genome background showed similar yield performance to that of Shanyou 63. These results suggest that dominance underlying functional complementation is an important contributor to yield heterosis and that heterosis assembly might be successfully promised by manipulating several major dominant heterotic loci.