Conversion of the Statistical Combining Ability into a Genetic Concept

Since the combining ability was proposed in 1942, efforts to uncover the genetic basis underlying this phenomenon have been ongoing for nearly 70 yr, with little success. Some breeding strategies based on evaluation of combining ability have been produced, and are still extensively used in hybrid breeding. In this review, the genetic basis underlying these breeding strategies is discussed, and a potential genetic control of general combining ability （GCA） is postulated. We suggested that GCA and the yields of inbred lines might be genetically controlled by different sets of loci on the maize genome that are transmitted into offspring. Different inbred lines might possess different favorable alleles for GCA. In hybrids, loci involved in multiple pathways, which are directly or indirectly associated with yield performance, might be regulated by GCA loci. In addition, a case of GCA mapping using a set of testcross progeny from introgression lines is provided.

Analysis of combining ability for stem-related traits and its correlations with lodging resistance heterosis in hybrid wheat

With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production. However,few studies have focused on combining ability and heterosis analysis of stem-related traits. In this study, 24 crosses were made according to NCII genetic design, using the three(photo-sensitive male sterile lines)×eight(restorer lines) incomplete diallel crosses. The length of basal second internode(LBSI) and breaking strength of basal second internode(BSBSI)as well as other stem-related traits were used to perform the principal component analysis(PCA), combining ability and heterosis analysis. The PCA results showed that the variables could be classified into two main factors, which were named as the positive factor(factor 1) and the negative factor(factor 2), and accounted for 52.3 and 33.2%, respectively, of the total variance in different variables, combined with the analysis for index weight indicated that the factor 1-related traits play positive roles in lodging resistance formation of hybrids. Combining ability variance analysis indicated that its genetic performance was mainly dominated by additive gene effects, and the hybrid combinations with higher lodging resistance can be selected by using of 14 GF6085(R1), 14 GF6343-2(R4), 14 GF6937(R6), 14 GF7433-1(R7), and BS1086(M3),which are with the features with lower general combining ability(GCA) effects of factor 2-related traits whereas higher GCA effects of factor 1-related traits. The heterosis analysis showed that the wide range of heterosis varied with the traits and combinations, and GCA or specific combining ability(SCA) effects of factor 1-related traits except wall thickness of basal second internode(WTBSI) were positively and closely related to the heterosis of lodging resistance. Generally, the correlation coefficients of heterosis to GCA effects of sterile lines(GCAm) of factor 1-related traits are significantly higher than that to GCA of restorer lines(GCAr) and SCA, combined with the higher GCAm variance values of factor 1-related traits compared to GCAr, the GCAm of factor 1-related traits should be particularly considered when breeding hybrid combinations.The heritability analysis showed that the narrow-sense heritability of the diameter of basal second internode(DBSI) and the center of gravity height(TCGH) were obviously lower(<60%) than other traits, suggesting that these two traits were suitable for selection in higher generation for parental breeding. These could provide a theoretical basis for parental breeding and heterosis utilization of lodging resistance.

Combining ability and heterosis analysis over two environments in a diallel cross of three families of the clam Meretrix meretrix

A 3×3 complete diallel cross comprising three families of the clam Meretrix meretrix（P1, P2 and P3） was used to determine the combining ability of parental families and heterosis of F1 under indoor and openair environments for growth traits. Analysis of variance for shell length and whole body weight indicated highly significant cross effects, environment effects and the interaction of cross by environment. General combining ability（GCA） and specific combing ability exhibited great variation among crosses and between two environments. Pooled over environments, P2 was the top combiner among the three parental families for both traits studied. The cross of P1 and P3 had the highest SCA. Additionally, significant reciprocal effects were observed. For individual environment, about half of the crossbred combinations showed favorable Mid-parent heterosis（MPH）（〉1%） for the shell length and whole body weight. Our data has shown that non-additive genetic and reciprocal effects constituted the major sources of genetic variation for both shell length and whole body weight, which indicates that crossbreeding among selective families could further explore the heterotic effects.

Study of Yield Combining Ability and Genetic Relationship Among Exotic Tropical,Subtropical Maize(Zea mays L.) Inbreds and Temperate Maize Inbreds in China

Information on the genetic relationship between tropical maize (Zea mays L), germplasm and temperate maize germplasm is of great value to maize breeding. The objective of this study was to determine the combining ability and genetic relationship of 25 inbreds extracted from five tropical maize populations and a land race, with four temperate maize inbreds (Huangzaosi, Mol7, B73 and Dan 340). The 25 tropical inbreds were crossed with the four temperate inbreds and evaluated. Lines from Suwanl and POP28 had high general combining ability (GCA) for grain yield. The lines from POP32 (ETO) had the highest special combining ability (SCA) with B73; the average SCA value of the 5 lines was 879 kg/ha. The lines from Suwanl had the second-highest SCA (584 kg/ha) with Huangzaosi. The lines from Suwanl had the greatest relative heterosis (20%) with B73, followed by the lines from POP32 (ETO) with B73 (19%). Five heterotic patterns have been identified from this study: Suwanl × Reid, ETO × Reid, POP28× Reid, POP28× Ludahong-gu, and Suwan1× Lancaster.

Correlation Between Parents and F_1 and Combining Ability of Parents on Seed Dormancy in indica Rice (Oryza sativa)

Dormancy indices of hulled and dehulled seeds were investigated by using 19 cytoplasmic male sterile （CMS） lines, 9 restorer lines and their 109 F1 hybrids of indica hybrid rice. The seeds of each F1 and the parents were harvested on 35 days after flowering. Combining ability was analyzed in 25 combinations made by 5 CMS lines and 5 restorer lines （North Carolina II mating design）. The seed dormancy index of F1 was positively and highly significantly correlated with those of their parents and mid-parent value. Out of the 109 combinations, 82 combinations showed mid-parent heterosis, and 43 heterobeltiosis. Seed dormancy indices of F1s and their parents declined dramatically in dehulled seeds compared with hulled seeds, indicating that the hull played an important role in seed dormancy. However, the trends were similar in hulled seeds and dehulled seeds in terms of relationships between the seed dormancy indicices in F1 and their parents. The influence of hull on seed dormancy mainly depended on F1 genotype, not on the hull from maternal parent. The variances of general combining ability （GCA） in female and male parents occupied 59.2% and 31.1% of total variance, respectively. The variance of specific combining ability （SCA） in combinations occupied 9.7% of total variance, indicating that gene additive effects were principal. Among the 5 CMS lines, II112A had the highest GCA effect for seed dormancy, followed by D62A. Among the 5 restorer lines, IRl12 had the highest GCA effect for seed dormancy, followed by 2786. These lines are elite parental materials for breeding F1 hybrid rice with stronger seed dormancy.

Genomic prediction of the performance of hybrids and the combining abilities for line by tester trials in maize

The two most important activities in maize breeding are the development of inbred lines with high values of general combining ability(GCA)and specific combining ability(SCA),and the identification of hybrids with high yield potentials.Genomic selection(GS)is a promising genomic tool to perform selection on the untested breeding material based on the genomic estimated breeding values estimated from the genomic prediction(GP).In this study,GP analyses were carried out to estimate the performance of hybrids,GCA,and SCA for grain yield(GY)in three maize line-by-tester trials,where all the material was phenotyped in 10 to 11 multiple-location trials and genotyped with a mid-density molecular marker platform.Results showed that the prediction abilities for the performance of hybrids ranged from 0.59 to0.81 across all trials in the model including the additive effect of lines and testers.In the model including both additive and non-additive effects,the prediction abilities for the performance of hybrids were improved and ranged from 0.64 to 0.86 across all trials.The prediction abilities of the GCA for GY were low,ranging between-0.14 and 0.13 across all trials in the model including only inbred lines;the prediction abilities of the GCA for GY were improved and ranged from 0.49 to 0.55 across all trials in the model including both inbred lines and testers,while the prediction abilities of the SCA for GY were negative across all trials.The prediction abilities for GY between testers varied from-0.66 to 0.82;the performance of hybrids between testers is difficult to predict.GS offers the opportunity to predict the performance of new hybrids and the GCA of new inbred lines based on the molecular marker information,the total breeding cost could be reduced dramatically by phenotyping fewer multiple-location trials.

基于虾夷扇贝自交家系的双列杂交配合力分析

为评估“先纯后杂”种质改良技术在虾夷扇贝中的应用效果,利用3个自交F_(1)家系(21#、12#、16#)的子代,采用3×3完全双列杂交构建包含亲本正反交的9种组合,统计幼虫期和成体期的成活率性状并开展配合力分析。试验结果显示:自幼虫期3日龄起,各阶段存活率均有显著差异(P<0.05);3组亲本的一般配合力的大小和方向均不相同,在27、140、200、440日龄一般配合力差异显著(P<0.05),尤其在140日龄差异极显著(P<0.01),效应值为-6.88~8.25;在幼虫期,不同交配组合中62.96%的特殊配合力与其反交组合是相反的方向,16#×12#展现出较高的特殊配合力,最高值达18.33;在成体期特殊配合力的大小和方向也不同,从幼虫到成体的转换期(27~140日龄)多数组合出现了效应值下降趋势。21#×12#、16#×12#组合在存活率上的杂种优势展现了合理运用“先纯后杂”的育种策略的有效性;同时21#×21#、12#×12#、16#×16#组合在存活率上的优势显示了虾夷扇贝具有较强的遗传负荷清除效率。试验结果可为虾夷扇贝遗传改良提供基础数据。

番茄优良自交系部分品质性状杂种优势及配合力分析

按照Griffing Ⅳ不完全双列杂交设计,利用11个相关农艺性状优良亲本筛选出55个杂交组合。所有F1代杂交组合及其亲本采用随机区组重复3次的方法,对番茄品质性状进行杂种优势研究与配合力分析,筛选出强优势与高配合力组合。结果表明,果形指数主要由加性效应组成,果肉厚度主要由显性效应组成,每个亲本不同性状的一般配合力(GCA)效应值均存在区别;硬度特殊配合力效应值最大组合为18P24×18696(70.23),果形指数特殊配合力效应值最高组合为18920×18P24(0.88),果肉厚度特殊配合力效应值最大杂交组合为18954×18943(1.05);综合3种品质性状最优越组合有:18920×18P24、18P24×18696、18954×18943;番茄各性状遗传力依次为果肉厚>硬度>果形指数。

西藏玉米地方品种配合力分析

为筛选具有遗传优势的西藏玉米地方品种,以西藏6份地方品种自交系为母本,5份杂交种为父本,用不完全双列杂交技术组配的30份杂交组合的F 1代11个农艺性状进行亲本一般配合力和杂交组合F 1代特殊配合力分析。结果表明,一般配合力较高的亲本DF125、DF128可作为选配优良品种的亲本;特殊配合力较高的杂交组合F 1代DF220×兆和A79可作为高产杂交组合组配高产品种,DF125×五谷703,DF128×吉单12,DF125×五谷214,DF135×吉单17,DF174×吉单12可组配中高产品种。

白桦5×5完全双列杂交种苗性状的遗传效应分析

通过对白桦杂交子代种苗性状的分析,估算白桦亲本的遗传参数,为白桦第二代强化种子园的亲本选配提供理论依据.2003年在白桦强化种子园中以小北湖(BH)3个优树、帽儿山(M)2个优树作为杂交亲本,按5×5完全双列交配设计进行控制杂交,测定白桦25个杂交组合种子的千粒重、发芽率、发芽势及其苗高、地径等.结果表明,25个杂交组合的种子千粒重、发芽率、发芽势及其苗高、地径均存在着极显著的差异;千粒重、发芽率和发芽势的一般配合力、特殊配合力、反交效应差异也达到了极显著水平,苗高的一般配合力差异显著,而地径的一般配合力差异不显著,苗高和地径的特殊配合力及反交效应差异极显著;根据杂交子代一般配合力效应值和特殊配合力效应值,从25个杂交组合中初选M4×M1、BH3×BH2、M4×BH3、BH2×BH1、BH2×M1组合为优良组合,M4和BH3为优良亲本.

基于马尾松测交系子代的生长、干形和木材密度的配合力分析

利用设置在浙江省淳安县姥山林场的14年生测交系交配设计(测交系未经过一般配合力测定)的遗传测定林,研究马尾松生长、干形和木材基本密度的一般配合力(GCA)和特殊配合力(SCA)及所受的遗传控制。结果表明:马尾松胸径、树高、木材基本密度和干物质积累量皆存在显著的GCA和SCA效应,其全同胞家系遗传力在0.746～0.908间,受较强的遗传控制,其中胸径、木材基本密度和干物质积累量受加性基因效应控制为主、显性基因效应次之,树高受基因的显性效应控制略高于加性效应,而树干通直度完全由加性基因效应影响。统计分析表明,来自中南部的1134、1127和5906测交系其胸径、树高和木材干物质积累量的GCA为正值且较高,而来自北部安徽的3203测交系木材基本密度的GCA最高。在9个待测系中,5476、5158、3205的胸径、树高、木材干物质积累量和树干通直度的GCA均较高,但5476和5158的木材基本密度的GCA则较低,与木材基本密度GCA较高的5910和3205差异显著。马尾松SCA的大小则独立于GCA,因性状和组合而异。依据单株干物质积累量大于总体平均值的20%及树干通直度得分不小于4的选择标准,筛选出7个优良杂交组合,其单株干物质积累量的现实增益和遗传增益分别为22.68%～67.34%和20.25%～60.13%。

10个热带、亚热带玉米群体配合力效应研究

以 5个中国主要玉米自交系为测验种 ,采用NCⅡ遗传交配设计 ,对 10个热带、亚热带玉米群体的配合力效应及利用潜力进行评价。两年研究结果表明 ,群体 2 1、群体 43和群体StayGreen的产量一般配合力依次最高 ,利用潜力较大 ;参试的 5 0个顶交组合中 ,Mo17×群体 43、自 330×群体 43、丹 34 0×群体 2 1和Mo17×群体StayGreen4个组合特殊配合力较大 ,产量最高 ,对照优势最大。根据单株产量特殊配合力结合一般配合力效应 ,将 10个热带、亚热带玉米群体初步划分 5群 ,其中Tuxpeno群、StayGreen群和P5 0 0群一般配合力较高 ,为我国温带玉米育种具有潜在利用价值的 3个杂种优势群。

普通油茶杂交子代幼林经济性状的遗传分析

为了建立油茶杂交育种最佳亲本选配模式,提高育种效率,以浙江省金华市东方红林场6个普通油茶杂交组合子代林为试材,分析了亲本在杂交子代单株产果量、果实大小、出籽率、干籽出仁率、种仁含油率、脂肪酸成分含量等17个经济性状的一般配合力(GCA)和特殊配合力(SCA),估算了各性状的遗传参数。结果表明,除了鲜果干籽率外,其余16个经济性状在6个杂交组合间均存在显著差异;亲本在各性状的一般配合力差异达极显著水平,亲本间特殊配合力在单株产果量、单果质量、种仁含油率、油酸含量等重要育种形状上亦差异显著或极显著;除了含油率外,其余主要经济性状的亲本GCA方差都显著大于亲本在SCA方差,均受基因的加性效应控制为主、非加性效应次之;遗传力较低,广义遗传力在10.10%~46.80%间,狭义遗传力在0%~41.30%之间,受到较强的环境效应影响。综合分析主要育种性状的亲本GCA、SCA效应,确定优良亲本为53号和81号,优良组合为53×81和178×81,其杂交子代单株产果量分别比平均产果量高78%和35%,单果质量比平均值分别高14%和11%,风干籽出仁率比总平均值分别高8%和5%,种仁含油率提高了5%和9%。参试亲本间遗传距离在0.254 5~1.791 8间,只与油脂中油酸、亚油酸含量在0.1水平上具有相关性,与其他经济性状间无显著相关性。因此,油茶杂交育种中,除了油酸含量外,针对幼林大部分经济性状,未评估过GCA的亲本材料,先评估其GCA比评估亲本间的SCA更重要。

玉米自交系产量配合力综合评价方法探讨

用８个配合力不同的玉米测验种测定了６个待测系的配合力，结果表明，亲本自交系的ＧＣＡ与ＳＣＡ都对杂交种的产量有着重要作用，且二者的作用是平行的，不能相互代替。为此，提出了综合评价玉米自交系ＧＣＡ与ＳＣＡ的指标“ｇｉ＇＋Ｓｓｉ＇”，称之为“总配合力效应”，并验证了这一指标的可靠性。

烤烟亲本配合力的双列杂交分析

利用6个烤烟品种(系),按双列杂交设计配制成15个杂交组合。对烤烟F1代的主要化学成分和产量特性、亲本间的一般配合力(GCA)、杂交组合间的特殊配合力(SCA)进行了分析与研究。结果表明:亲本间的GCA和杂交组合间的SCA差异均达到极显著水平。说明烤烟品种的产量和质量性状受加性效应和非加性效应基因的共同控制。对亲本间的GCA效应和杂交组合间的SCA效应分析表明,相同亲本不同性状的GCA存在较大差异,而杂交组合间的SCA与亲本间的GCA并没有直接的关系。评价亲本的育种价值和对杂交组合的选配应以亲本的GCA和组合的SCA方差分析为依据。

11份超甜玉米自交系产量和食味品质性状配合力分析

以8个分属于Reid、Lancaster类群超甜玉米自交系为母本,3个唐四平头类群超甜玉米自交系为父本,采用NCⅡ设计方法,按照不完全双列杂交组配24个杂交组合,对超甜玉米鲜食种皮厚度、鲜食甜度、煮食种皮厚度、煮食甜度及产量的一般配合力和特殊配合力进行分析。结果表明:12H6048对子代籽粒5个性状均表现为正遗传效应,12H6004对子代籽粒5个性状均表现为负遗传效应;12HZ46-48鲜食与煮食甜度特殊配合力效应值最高,12H351的5个性状特殊配合力效应值均最低;每种性状特殊配合力效应值最高的组合均是由一般配合力效应值高或中的自交系组配,至少也要有一个亲本是高或中等水平的一般配合力组配而成。

滇型不育系和恢复系的配合力分析

用生产上广为应用的9个粳稻不育系和8个粳稻恢复系为亲本,采用p×q不完全双列杂交(NCⅡ)设计,对其F1代10个农艺性状的配合力进行了分析。结果表明,10个性状的一般配合力和特殊配合力均达显著(P<0.05)或极显著(P<0.01)水平。单株产量、穗总粒数、有效穗主要受非加性效应的影响,实粒数、结实率、着粒密度同时受加性效应和非加性效应影响,千粒重、穗长、株高、播抽历期主要受加性效应的影响。单株产量、穗总粒数、结实率、穗长、着粒密度受不育系影响较大,而实粒数、千粒重、有效穗、株高、播抽历期受恢复系的影响较大。高配合力的亲本是选育强优势组合的重要基础,要选育高产量的杂交组合,不育系的选择比较重要。不育系以滇粳优2号A、合系41A、滇粳优5-1A、大理香谷A较好,有较大的应用潜力。恢复系以南34、香糯选、南29选和南34选较好。

杂交稻新组合主要农艺性状配合力分析及利用评价

利用引进的5个不育系(全丰A、谷丰A、天丰A、广抗13A、蓉18A和Ⅱ-32A)和自育的6个恢复系(YR1577、YR2292、YR3003、YR4245和YR7633)进行不完全双列(NCII模式)杂交,配置的30个杂交组合。对F1代农艺性状的配合力进行分析,结果表明:穗长、穗实粒数、结实率、千粒质量和单株产量的特殊配合力高于一般配合力,说明大多数农艺性状受非加性效应影响大;亲本方面,穗长、有效穗数、穗总粒数、穗实粒数、千粒质量的性状表明恢复系对后代的影响大于不育系。综合考虑配合力和遗传力效应,选育高产量的杂交组合以Ⅱ-32A/YR2292和广抗13A/YR7633优势较为明显。

油茶5×5全双列杂交子代幼林生长性状的配合力分析

以浙江省金华市东方红林场油茶5×5全双列交配杂交组合（无自交）子代林为试材,分析了2年生苗造林当年树高、地径和冠幅的遗传变异规律,估算了油茶亲本的遗传参数。结果表明：树高、地径和冠幅在20个杂交组合间均存在显著的遗传差异,40×95和10×40两个组合在树高、地径和冠幅性状上均表现最优;树高和冠幅的一般配合力、特殊配合力和反交效应差异极显著,地径的一般配合力和反交效应也差异极显著,特殊配合力无显著差异;长林40号树高、地径和冠幅3个性状的一般配合力均最高,在0.05水平上显著高于其余亲本,这与该良种长势旺的特性一致;长林53号作为亲本,在树高、地径和冠幅上的一般配合力均最低,这与53号无性系良种长势偏弱、树冠矮小的特点一致;3个性状的加性方差分别是非加性方差的1.25倍、19.5倍和1.60倍,均受基因的加性效应控制为主,非加性效应次之;遗传力较低,广义遗传力在14.91%~20.62%之间,狭义遗传力在9.55%~14.14%之间,受到较强的环境效应影响;综合分析GCA、SCA及反交效应,确定5个最佳组合,其杂交子代树高和冠幅分别实现5.76%~45.62%和7.68%~127.10%的遗传增益。可见,油茶杂交育种中,针对树高、地径和冠幅等生长性状,未评估过GCA的亲本材料,先评估其GCA比评估亲本间的SCA更重要。

12个玉米自交系主要性状遗传研究及综合评价

本研究选取7个热带、亚热带玉米自交系和5个改良后的温带玉米自交系采用Griffing双列杂交方法Ⅳ进行完全双列杂交组配,共配制66个杂交组合。以大面积推广杂交种云瑞6号为对照,对供试自交系不同性状进行配合力和对照优势等分析。结果表明改良后的温带玉米自交系YML582、YML5986和热带、亚热带玉米自交系CML166、YML46单株产量配合力高、综合性状优良,用它们作亲本较易组配出综合性状优良的杂交组合,育种潜力较大;杂交组合YML5986×YML46、YML1216×YML46、YML1071×CML486、YML1071×YML5986、YML582×YML46,综合性状优良,可作为苗头组合进一步试验。