Agronomic Performance of F1 Hybrids of Rice (Oryza sativa L.) in Japonica-Indica Crosses

Summary

Generally F₁ hybrids from crosses between japonica and indica rice show variable degrees of sterility. Previous studies revealed that among the indica rice, the Aus type has sexual affinity with japonica cultivars giving higher fertility in F₁ hybrids. Therefore, we made an effort to obtain higher grain yield by producing F₁ hybrids between japonica and Aus-type indica. A field experiment was conducted to investigate the heterosis in these F₁ hybrids for dry matter accumulation, spikelet fertility, yield and yield attributes, to find cross combinations with higher grain yield, and examined the relationships of grain yield with some agronomic characters. F₁ hybrids flowered earlier than their parent cultivars. Heterosis for dry matter accumulation was positive at the panicle initiation stage, at heading and at maturity. The average heterosis for number of panicles, grain and straw yield per plant, number of spikelets per panicle and 1000-grain weight was positive. A few F₁ hybrids showed positive heterosis for number of filled grains per panicle, spikelet fertility and harvest index; but the average heterosis for these traits was negative. Among the yield components, a higher number of panicles per plant and higher number of spikelet per panicle contributed to higher grain yield in F₁ hybrids. A significant and positive relationship existed between spikelet fertility and grain yield per plant. The higher grain yield was attributed to higher dry matter production rather than higher harvest index in F₁ hybrids, although low spikelet fertility limited yield potential in some F₁ hybrids.     

Physio-Morphological Characters of F1 Hybrids of Rice (Oryza sativa L.) in Japonica-Indica Crosses: II. Heterosis for leaf area and dry matter accumulation

Summary

A pot experiment was conducted to investigate the heterosis for morphological characters and to examine the relationship among some characters at active tillering, flowering and dough ripe stages of 12 Fj hybrids from crosses between japonica and indica rice. Heterosis for plant height, number of tillers, green leaf area and dry matter accumulation per plant was positive at all stages. The intensity of heterosis was higher at the active tillering stage for number of tillers, leaf area and dry matter accumulation per plant. A significant positive relationship was found between tiller number and leaf area per plant at active tillering and flowering stages. Significant positive relationships between leaf area and dry matter accumulation, and between tiller number and dry matter accumulation per plant were observed at all stages. A significant positive relationship was found between leaf area per plant at an early stage and dry matter accumulation per plant at a later stage, suggesting that early development of leaf area is an important factor for higher dry matter accumulation in 1 hybrids. Although heterosis for percent dead leaf blade was positive at the flowering stage due to early leaf senescence in some Fx hybrids, a larger leaf area was also found in Fx hybrids at this stage and leaves of Fx hybrids remained green longer compared to parent cultivars up to the dough ripe stage.     

Combining ability analysis to identify suitable parents for heterosis in seed cotton yield,its components and lint % in upland cotton

Combining ability and heterosis were studied in a 6 × 6 diallel cross to see the nature of gene action in Upland cotton (Gossypium hirsutum L.) during 2002 to 2004. Analysis of variance revealed highly significant differences among all the F₁ and F₂ hybrid means and their respective six parental values for all the traits examined. In both generations, the mean squares due to general combining ability (GCA) and specific combining ability (SCA) were also highly significant. SCA genetic variances were greater than GCA and more important for the traits, i.e. boll weight, boll number and seed cotton yield per plant, showing the predominance of non-additive gene action. Lint % in both generations and boll weight in F₂s only were controlled by additive type of gene action due to maximum GCA variances. Cultivar CIM-1100 was found to be the best general combiner and its utilization produced valuable hybrids with desirable SCA in both generations. F₁ and F₂ hybrids, viz., CIM-1100 × CRIS-9, CIM-1100 × FH-682, CIM-1100 × BH-36 and CIM-109 × CIM-1100 as high × low and low × high parents performed well in SCA determination, outstanding mean performance and heterosis. Better SCA effects associated with useful heterosis were more pronounced for yield traits. In F₁ hybrids, maximum heterosis was observed for seed cotton yield followed by boll number, boll weight and lint %. The heterosis over better parent was +3.13 to +65.63% for bolls per plant, +0.75 to +24.40% for boll weight, +0.82 to +115.22% for seed cotton yield and +0.27 to +3.88% for lint %. Involvement of CIM-1100 in most of the F₁ and F₂ hybrids resulted in the synthesis of superior genotypes for most of the traits studied. Inbreeding depression was elevated in good performing hybrids and was the highest for seed cotton yield. Highest yielding F₁ hybrids yielded lesser in the subsequent generation due to over-dominance and inbreeding depression, whereas moderate yielding F₁ hybrids were found more stable even passing through process of segregation due to additive gene action. The combined performance of F₁ and F₂ hybrids could be a good indicator to identify the most promising populations to be utilized either as F₂ hybrids or as a resource population for further selection.     

A comparison of inbred line and F1 testers for evaluating sorghum experimental lines in testcrosses

Selecting an effective tester for evaluating the hybrid performance and heterosis of new inbred lines is crucial to ensure their accurate evaluation. Most sorghum breeding programs use at least two elite inbred line testers when evaluating new inbred lines. These testcrosses provide valuable information, but the specificity of inbred line testers may incorrectly characterize experimental lines that would combine well with other genetic backgrounds. Reducing this risk by increasing the number of preliminary testcrosses is limited in breeding programs by resource availability. Efficiently diversifying testcrosses may be accomplished through the use of F₁ testers. Testcrosses made with F₁ testers simultaneously evaluate inbred lines against two genetic backgrounds. In preliminary testcrosses, this may reduce the probability of incorrectly discarding new lines or improve the efficiency of preliminary testcrossing. The objective of this research was to compare two sorghum inbred line testers to their respective F₁ as a tester for evaluating sorghum inbred lines (R-lines) in testcrosses for grain yield. The testers used were A.Tx623, A.Tx2752 and their F₁ hybrid, A.Tx623/B.Tx2752. Data from testcross hybrids from 33 different inbred lines grown in three environments indicated that the F₁ tester was comparable in accuracy and discriminatory efficiency to the inbred line testers. The results indicated that a single cross tester in sorghum can serve to effectively evaluate new germplasm.     

小黑麦杂交F_1代真假杂种的ISSR标记鉴定及遗传多样性分析

为了给ISSR标记技术应用于小黑麦杂种鉴定提供参考,利用ISSR标记对小黑麦品系P1和P_2有性杂交得到的F_1代群体进行分子鉴定,同时结合田间表型调查结果对F_1代群体进行遗传多样性分析。结果表明,66个杂交F_1代单株中,52个为真杂种,其中,5个单株无主茎、未结实,1个生长后期死亡。14条ISSR引物对46个正常结实真杂种扩增的多态性条带百分率为61.19%,其中,UBC822的多态性条带百分率为100%,UBC808和UBC815的多态性条带百分率均为75%。F_1代群体和父母本的遗传相似系数为0.62~0.94,说明杂交后代产生了丰富的遗传变异。聚类分析将杂交F_1代群体和父母本在阈值0.748处分为3大类群,第1类群包括1份材料(父本,P1),第2类群包括1份材料(母本,P_2),第3类包括46个杂交F_1代单株;杂交F_1代与父母本的遗传距离较远,先与母本聚为一类,之后与父本聚为一类。田间调查结果表明,7个性状中,除株高偏向于父本外,分蘖数、有效分蘖数、穗长、小穗数、穗粒数和穗粒重均偏向于母本,与父本的差距较大,这与ISSR分析结果基本相吻合。     

干旱胁迫下披碱草属种间杂种F1的DNA甲基化MSAP分析

为了研究披碱草属种间杂种抗旱性优势的遗传机理，以加拿大披碱草（J1）、老芒麦(L1)及其种间杂种F₁为试验材料，经干旱胁迫处理，采用甲基化敏感扩增多态性（MSAP）方法，探究干旱胁迫后亲本及种间杂种F₁的DNA甲基化变化规律。结果表明，亲本材料L1和J1的DNA平均甲基化水平分别为45.41%和59.53%，杂种F₁的DNA甲基化水平为44.24%，说明杂种在形成过程中发生了DNA去甲基化作用。全甲基化在杂交种的DNA甲基化模式中占主导地位。干旱胁迫前亲本L1、J1和杂种F₁的DNA甲基化程度分别为32.73%、41.54%和28.00%，杂种F₁甲基化水平为亲本材料的75.40%；干旱胁迫后各材料的DNA甲基化程度均增加，平均增幅分别为14.99、20.44和19.78个百分点，说明干旱胁迫对不同材料DNA甲基化水平均有明显影响，且具有特异性。杂种F₁的抗旱性最强，其DNA甲基化水平低于亲本，说明杂交种的抗旱性与DNA甲基化水平存在一定的负相关。     

粳稻不同生态类型间F1的杂种优势及其亲本的配合力分析

用8个不同生态类型的粳稻品种配成8×8双列杂交,研究8个重要农艺性状的杂种优势以及亲本的配合力。结果表明,不同生态类型间杂种F1 各性状的优势有正有负。56个F1组合平均, 小区产量性状表现19.5%的高亲优势, F1小区产量超过高亲值的组合占87.5%,其余7个性状的F1值位于中亲值与高亲值之间。 在不同生态类型所构成的总体中,株高、每穗总粒数、每穗实粒数和小区产量4个性状的加性遗传方差和非加性遗传方差同等重要;抽穗期、穗长、单株有效穗3个性状的加性遗传方差更重要;千粒重性状非加性遗传方差更为重要。小区产量和产量构成因素一般配合力效应和特殊配合力效应方差较大的亲本是秀水04和3726;特殊配合力效应大且综合性状优良的组合是越光/秀水04。     

籼型杂交水稻杂种与亲本的稻米品质比较

 以具广泛代表性的7个不育系和9个恢复系及其配制的63个组合为材料,对籼型杂交水稻11个稻米品质性状的杂种与亲本的表现进行了比较研究。就全部杂交组合各品质性状相对优势而言，无论是超亲优势、完全显性还是部分显性，都表现为负向的几率远大于正向。 组合间杂种品质表现的差异因性状而异,无论是中亲优势指数、超高亲优势指数，还是超低亲优势指数，均以垩白大小、垩白粒率、胶稠度和整精米率等性状组合间变异为大。全部性状杂种平均值都显著或极显著低于高亲值。除精米长和直链淀粉含量杂种值极显著高于中亲值外，其余性状都与中亲值接近或极显著低于中亲值。除糙米率、精米率和胶稠度杂种值低于低亲值外，其余性状都显著或极显著高于低亲值。     

Insect-mediated cross-pollination in soybean [Glycine max (L.) Merrill] : I. Agronomic performance

In soybean, manual cross-pollination to produce large quantities of F₁ hybrid seed for yield trials is difficult and time-consuming. Conversely, insect-mediated cross-pollination has been shown to produce large quantities of hybrid seed in soybean and could facilitate the identification of heterotic patterns. The objective of our study was: (1) evaluate F₁ hybrid soybean plants from single crosses for yield and agronomic traits over several environments and (2) compare hybrid performance of the single crosses to lines developed from three-way crosses and backcrosses. In 2003, F₁ seed of single-crosses and their parent lines were evaluated in replicated experiments at three locations. Also in 2003, three-way crosses, and BC₁F₁ seed were produced. In 2004, three-way crosses, BC₁F₁ crosses, and their parent lines were evaluated at one location. High-parent heterosis (HPH) in single-crosses for grain yield ranged from −41.11% to +11.19%; for protein content from −4.34% to +3.53%, and for oil content from −13.22% to −0.84%. In three-way crosses, HPH for yield ranged from −25.21% to −4.50%, for protein from −2.72% to +1.92%, and for oil from −5.87% to −1.20%. For BC₁F₁ crosses, HPH for yield ranged from −15.65% to +41.97%, for protein from −2.57% to +1.69%, and for oil from −2.47% to +2.22%. Although positive heterosis levels were observed across all populations tested to determine the economic feasibility it is imperative that more tests of more cross-combinations be evaluated in replicated environments. Extensive research in different environments must be conducted to determine what parental combinations will produce the highest heterosis levels, and to develop criteria for selecting the parents with the best combining ability. This will be important to maximize agronomic performance that can economically justify the use of hybrids in soybean production.     

玉米F1、F2代穗粒性状的遗传效应分析和适宜群体筛选

利用2个优良爆裂玉米自交系与6个Reid类群普通玉米自交系杂交组配12个杂交组合,研究穗长、穗粗、穗行数、行粒数、百粒重、穗重、穗粒重和出籽率8个穗粒性状的F1表现、杂种优势和F2群体表现、分离特征及其与亲本的相关性。结果表明,不同组合F1表现、中亲优势(MH)、超高亲优势(HH)和F2群体的平均值(F2M)、变幅、变异系数、优势衰退(HDR)等均存在不同程度差异,各穗粒性状杂交早代的遗传背景效应突出;F2群体各性状均呈连续正态分布,存在超双亲分离,为多基因控制的复杂数量性状;杂种优势较小的穗行数、出籽率和穗粗可以根据两类亲本或其均值初步预测其组合F1和F2M值的表现,对于杂种优势较大的穗重、穗粒重和百粒重不宜进行预测;除穗行数和出籽率外,其余性状F1表现与F2M、MH和HH以及F2M、MH、HH间多呈显著或极显著正相关,HDR与F1、F2M、MH和HH均呈显著或极显著负相关;R2×N04、R4×N10和R5×N10组合为进一步开展遗传作图和改良爆裂玉米自交系穗粒性状的最佳群体。     

玉米无叶舌种质10H045对F1代植株叶片生长态势和产量的影响

以昌7-2和应用EMS对昌7-2诱变选育的无叶舌新种质—10H045为父本，以郑58、WX201620和WX201623表型差异显著的3个自交系为母本进行杂交，研究无叶舌种质10H045对F₁代植株叶片生长态势和产量的影响。结果表明，以10H045为父本杂交的F₁代，其茎叶夹角和叶向值均比以昌7-2为父本杂交的F₁代的植株要小，且差异显著；穗3叶以上的叶片上冲特性尤为突出，植株塔型结构明显，有利于提高杂交种产量。无叶舌种质10H045为父本的组合，其产量均比以昌7-2为父本的组合产量高，组合WX201623×10H045的产量最高，与其他组合产量差异达极显著水平。无叶舌种质10H045不但对后代株型结构有很大的改善作用，而且产量的一般配合力较高，是一个优异亲本。     

玉米杂交当代优势研究进展

杂种优势利用是玉米种质遗传改良与技术创新的理论基础。利用杂交当代(F₀)优势来提高玉米子粒产量和改善品质是研究的重点。综述了近年来玉米杂交当代优势的研究进展,并探讨了杂种当代优势有效利用的主要途径。     

利用花青素基因标记研究正反交对玉米杂交种主要性状的影响

以转花青素合成转录因子Bi和Cl基因玉米的稳定表达株系与自交系B73-329(CK)进行杂交,研究花青素基因在玉米杂种F_1植株组织、器官中表达情况。结果表明,用转基因株系作为母本的杂交种F_1植株部分存在表型分离,用自交系B73-329作为母本的杂交种F_1植株不存在表型分离。转基因杂交种F_1植株,颖紫色,苞叶、茎鞘紫色,气生根紫色,与CK差异显著;转基因杂交种F_1植株叶片为绿色,转基因株系自交分离群体株系的叶片为紫色;转基因杂交种F_1植株绝大部分花丝为黄色,个别花丝红色,子粒绝大部分为黄色。抽丝、散粉期,转基因杂交种株高、穗位高等农艺性状与对照差异不显著,但是大部分产量显著低于对照,推测其主要原因在于花青素合成途径的引入导致植株能量代谢损耗所致。研究表明,转基因玉米杂交制种应用应以转基因株系作为父本。     

小麦核质互作杂交种农艺性状和籽粒性状的杂种优势分析

为探究核质互作杂交种不同性状间的遗传变异规律和杂种优势,用8种小麦同核异质、同质异核雄性不育系分别与恢复系R5174、R2726组配获得16个杂交组合,对其F₁代及亲本的11个农艺性状和6个籽粒物理性状进行遗传变异、杂种优势、相关性、主成分及聚类分析。结果表明：（1）F₁表型性状的变异系数为3.00%～32.72%,农艺性状的变异系数大于籽粒性状;（2）不同性状间杂种优势差异显著,中亲优势和超亲优势分别为0.22%～12.50%和-13.51%～3.61%,其中正中亲优势组合最低比例为50%,正超亲优势组合最高比例可达81.25%;（3）粒形与旗叶面积呈显著正相关,与穗长、小穗数、穗粒数呈显著负相关;（4）从通过主成分分析得到的F₁代综合得分看, P型和Y型细胞质背景下的AK58不育系与R2726的杂交组合F₁表现最好;（5）通过聚类分析可将F₁分为两大类,其中第二大类包含除AS细胞质背景的AK58异质不育系与恢复系R2726组配的杂交组合,其共同的特征是籽粒表面积大、千粒重高及旗叶性状较好,表型性状的综合表现优于第Ⅰ类群,说明杂交种的性状受恢复系和不育系核背景影响较大。     

F型小麦雄性不育系测恢研究及杂种优势分析

小麦F型雄性不育系是具有普通小麦细胞质的新型细胞质雄性不育系。本研究利用364个普通小麦品种(系)与F型雄性不育系FA杂交配制F1,测定其育性恢复性。结果表明,49个小麦品种(系)对F型不育系具有完全恢复性,其F1的自交结实率(国际法)达到甚至超过对照(黄淮冬麦区主栽品种周麦18),这些材料可作为FA的恢复系供进一步研究利用。这一结果说明,小麦F型雄性不育系的育性较易恢复。另外,7个小麦品种(系)对不育系FA不具有恢复力,可用于转育新不育系。从364个组合初选出15个组合,经超标杂种优势分析,7个组合表现更优,具有不同程度的增产潜力,需进一步升级试验、筛选鉴定。     

玉米种子活力的杂种优势分析

对12个玉米组合及其亲本的种子活力指标进行了杂种优势和亲子相关分析。结果表明,所有玉米种子活力指标均表现正向杂种优势。F₁代田间幼苗干重与父本值、高亲值、双亲差值呈显著正相关;F₁代低温发芽率与双亲差值呈显著负相关;F₁代发芽指数与母本呈显著正相关;F₁发芽势与母本值、低亲值呈显著正相关;F₁代田间出苗率、幼苗高、标准发芽率、活力指数受亲本的影响较小,与父本、母本、中亲值、高亲值、低亲值和双亲差值相关系数均不显著。     

玉米品种通育189的雄穗分枝数F1平均优势及遗传分析

针对PH6WC、PH4CV、B20、D1279及PH6WC×PH4CV、PH6WC×B20、PH6WC×D1279、D1279×PH6WC鉴定试验进行雄穗分枝数差异分析,PH6WC×D1279(通育189)组建6世代群体(P₁、P₂、F₁、B₁、B₂、F₂),运用主-多基因混合模型遗传分析方法对雄穗分枝数遗传进行分析。结果表明,通育189雄穗分枝数存在细胞质遗传效应,F₁雄穗分枝数平均优势为28.57%～132.41%;雄穗分枝数遗传模型为2对主基因加、显、上+多基因加、显混合模型,2对主基因为正向完全显性,主基因上位性效应>显性效应>加性效应;主基因效应是多基因效应的41.25倍,主基因遗传率为27.58%～88.87%,多基因遗传率为0～41.78%。     

水分利用效率分子标记在小麦不同种质材料中的分布

高水分利用效率（Water use efficiency,WUE）是丰产性和节水性的统一。为给小麦高WUE分子设计育种提供理论依据和技术支撑,利用与WUE相关QTLs紧密连锁的8个分子标记和与叶水势紧密连锁的2个分子标记,通过PCR技术检测了其在小麦进化种质、黄淮海麦区小麦品种（系）、高代小麦新品系和F₁代共81份小麦随机材料中的分布。结果表明,在10份小麦进化种质中,有9个WUE相关分子标记的出现频率均高于70%。在27个黄淮海水旱地区代表品种（系）中,有7个WUE相关分子标记的出现频率高于85%。在44份高代品系和F₁代中,有9个WUE相关分子标记的出现频率高于90%。在晋麦47×京东8号、济麦22×运旱22-23和济麦22×长6878杂交F₁代中实现了WUE相关分子模块组装。在81份小麦随机材料中,有9个WUE相关标记的出现频率高于85%,说明这些分子标记能够稳定遗传,可用于小麦WUE分子标记辅助育种。     

杂种小麦干物质积累及其杂种优势的研究

对6个澳大利亚杂种小麦在不同生育期植株及各器官的干物质积累、分配及干物质积累的杂种优势进行了研究。结果表明,植株总干物质积累在籽粒灌浆末期达到最大值,茎秆和叶片干物质积累均在开花期达到最大值。挑旗期茎秆、叶片各占植株总干物质的50％;从孕穗王灌浆末期,茎秆为干物质的主要贮存器官,占植株总干物质的 39.87％～66.67％;在成熟期,籽粒成为干物质贮存的最主要部位,占37.65％,茎秆占35.23％。从6个杂交种平均值来看,干物质积累多表现为正向杂种优势,尤其在营养生长期优势最明显。相关分析表明,营养生长期植株总干物质积累量较大且主要分配在茎秆部位的杂交品种,一般具有较高的籽粒产量和较强的产量优势。     

马铃薯4x×2x杂种无性一代产量及产量性状的表现

产生２ｎ花粉的Ｎｅｏ－ｔｕｂｅｒｏｓｕｍ双单倍体×Ｓｏｌａｎｕｍｐｈｕｒｅｊａ的二倍体杂种以及其与Ｎｅｏ－ｔｕｂｅｒｏｓｕｍ双单倍体的回交后代与普通马铃薯（Ｓ．ｔｕｂｅｒｏｓｕｍｓｓｐ．ｔｕｂｅｒｏ ｓｕｍ品种东农３０３进行了杂交。４ｘ杂种在株高方面表现出了很强的杂种优势。商品薯产量与４ｘ亲本无显著差异，但两个杂种群体的最高值分别超４ｘ亲本的２６０ｇ／株和６０ｇ／株。总产量杂种优势明显，但杂种单株结薯数多，平均块茎重小，这些是限制４ｘ×２ｘ杂种利用的不利因素，需要进一步地改善。