Combining ability of Egyptian cotton(Gossypium barbadense L.)reveals genetic potential for improved yield and fiber quality

Background As the most widely cultivated fiber crop,cotton production depends on hybridization to unlock the yield potential of current varieties.A deep understanding of genetic dissection is crucial for the cultivation of enhanced hybrid plants with desired traits,such as high yield and fine fiber quality.In this study,the general combining ability(GCA)and specific combining ability(SCA)of yield and fiber quality of nine cotton parents(six lines and three testers)and eighteen F1 crosses produced using a line×tester mating design were analyzed.Results The results revealed significant effects of genotypes,parents,crosses,and interactions between parents and crosses for most of the studied traits.Moreover,the effects of both additive and non-additive gene actions played a notably significant role in the inheritance of most of the yield and fiber quality attributes.The F1 hybrids of(Giza 90×Aust)×Giza 86,Uzbekistan 1×Giza 97,and Giza 96×Giza 97 demonstrated superior performance due to their favorable integration of high yield attributes and premium fiber quality characteristics.Path analysis revealed that lint yield has the highest positive direct effect on seed cotton yield,while lint percentage showed the highest negative direct effect on seed cotton yield.Principal component analysis identified specific parents and hybrids associated with higher cotton yield,fiber quality,and other agronomic traits.Conclusion This study provides insights into identifying potential single-and three-way cross hybrids with superior cotton yield and fiber quality characteristics,laying a foundation for future research on improving fiber quality in cotton.

Combining ability and gene action studies for yield and fibre traits in Gossypium arboreum using Griffings numerical and Haymans graphical approach

Background For the purpose of utilising hybrid vigour to produce possible hybrids with a suitable level of stability,the knowledge of gene activity and combining ability is a crucial prerequisite before choosing desirable parents.The present study was carried out with six parents crossed in full diallel fashion and generated 30 F1 hybrids.These hybrids were evaluated in two replications in Randomized Block Design at Department of Cotton,TNAU for combining ability and gene action.Diallel analysis was carried out according to Griffing’s method-I(parents + F_(1) + reciprocals) and model-I and Hayman’s graphical approach by using INDOSTAT software.Results Analysis of variance for combining ability indicated that mean square values of GCA,SCA and reciprocals were highly significant for all the traits except for the uniformity index.RG763 and K12 showed highly positively significant GCA effects for most of the yield traits while PA838 and K12 for fibre quality traits,so they were found as best general combiners.PAIG379 × K12 and PDB29 × K12 for yield traits,and PDB29 × PA838,RG763 × PA838,and CNA1007 × RG763 cross combinations for fibre quality traits could be recommended for future breeding programms.Conclusion The results of both Griffing’s and Hayman’s approaches showed that non-additive gene action predominates as SCA variance was bigger than GCA variance,so heterosis breeding is thought to be a more fruitful option for enhancing GCA of many traits.

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.

Invention and Utilization of Glutinous Sorghum Male Sterile Line 45A with High Starch and High Combining Ability

45A is a glutinous sorghum male sterile line with high starch and high combining ability bred by Rice and Sorghum Institute of Sichuan Academy of Agricultural Sciences in 1998, it is a coeno-species taking non-glutinous maintainer line TL169-239B which bred by Tieling Institute of Agricultural Sciences in 1991 as the female parent and glutinous maintainer line72B bred by the authors＇ institute as the male parent, then, based on the backcross breeding between glutinous single plant chosen from F2 segregation population and Tx623A. There are ten hybrid sorghum varieties which already have been examined and approved by national and above provincial（municipal） level units; the patent of this breeding method has been authorized （the patent number： ZL 2012 1 0129155.6）; 45A is protected by the Right of New Varieties of Plants, MOA, P.R. China （the variety right number： CNA20090576.1）. In this paper, the breeding process of 45A and the characteristics of 45A sterile line and its hybrid sorghum were summed up, what＇s more, the technical key points of high-yielding breed of 45A and the production of hybrid sorghum seeds were introduced, to provide data for further popularizing the sterile line.

Analysis on the Combining Ability and Heritability of Main Agronomic Traits of Hybrid Glutinous Sorghum

Using 3 sterile lines and 12 restorer of glutinous sorghum as experimental materials,36 hybrid combinations（3×12 NCⅡ） were designed to analyze the combining ability and heritability of six main agronomic traits,including plant height,panicle length,growth period,1 000-grain weight,per panicle grains and per panicle grain weight.The results showed that except per panicle grain number all other five agronomic traits have remarkable or extremely remarkable general combining ability and specific combining ability.Six agronomic traits were found to be control by additive genetic effect.Most of these agronomic traits are more easily influenced by restorers than sterile lines,suggesting that more attention should be paid to select restores in hybrid glutinous sorghum breeding.The narrow-sense heritability of these agronomic traits were in order growth period plant height per panicle grain weight panicle length 1 000-grain weight per panicle grains.

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.

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.

Analysis of Heterosis, Combining Ability and Heritability of Cadmium Content in Brown Rice of Three-line Indica Hybrid Rice

Five cytoplasmic male sterile （CMS） lines were used as parents in an incomplete diallet cross and six restorer lines of rice design （Nc II design）. Thirty hybrid combinations with the same growth period were selected as experimental ma- terials to investigate the heterosis, combined ability and heredity of Cd content in brown rice of indica hybrid rice. According to the results, Cd content in brown rice showed a significantly negative heterosis; the general combining ability and specific combination ability of Cd content in CMS and restorer lines both reached extremely significant level （P〈0.01）, indicating that both genetic improvement of parents and e- valuation of combinations are important to the breeding of hybrid combinations with low accumulation of Cd; the broad-sense heritabitity and narrow-sense heritability of Cd content were both relatively high with slight differences, which respectively reached 97.73% and 80.10%, indicating that Cd content in brown rice mainly de- pends on the additive action of genes; in addition, parent improvement showed bet- ter effect on the selection of early generation.

Combining Ability and Correlation of Ear Characteristics of Twenty Maize Inbred Lines

The combining ability and correlation of eight ear characteristics in 99 maize hybrids generated by crossing nine female parents with 11 male parents were analyzed by incomplete diallel cross （NC II ） design. The results showed that the line F6 had the highest general combining ability （GCA） for yield, followed by F7, M3, M4 and M8. All of the five lines have great potential in maize breeding. The cross combination M3xF10 had the highest specific combining ability （SCA） for yield, showing strong heterosis. Heritability analysis of ear characteristics showed that GCA variance was higher than SCA variance in ear diameter, number of rows per ear and seed rate, and they were mainly controlled by the additive gene effect, indicating that that the selections for these traits are effective at early generations. The other three traits had lower SCA, for which the selections should be carried out at late generations. The correlation analysis revealed that ear length, number of grains per row, ear diameter, number of rows per ear, 100-seed weight and seed rate had extremely significant positive correlations with grain yield per plant. Among them, number of grains per row had the most significant effect on yield per plant. Barren tip length had a significant negative correlation with grain yield per plant. Therefore, we concluded that the combinations with more grains per row and shorter barren tip should be selected to achieve high yield of maize.

Analysis on Combining Ability and Genetic Parameters of Main Agronomic Characters of 22 Maize Inbred Lines

The general combining ability（GCA）, special combining ability（SCA） and genetic parameter of ten characters of 22 maize inbred lines including plant height and ear height were analyzed using 10×12 through incomplete diallel cross（NC Ⅱ）.The results showed that：（1） Among the 22 maize inbred lines, the yield GCAs of11 HN 097, 11 HN 099, 11 HN 105 and 11 HN 110 were high, which were elite inbred lines to collocate hybridized combinations with strong heterosis. The yield of11 HN110 × 11 HN097, 11 HN110 × 11 HN105, 11 HN112 × 11 HN 097 and 11 HN 106 × 11 HN 104 were in the first four place. The yielding abilities, adaptabilities and yielding stabilities of the four combinations can be further identified by experiment. The heredities of the ten characters were mainly controlled by additive gene effect whereas the influence of non-addictive gene effect was small. The narrow heritabilities of plant height, ear height, ear rows, ear length, kernels per row,100-grain weight and seed-producing percentage were more than 50%. The variances were mainly caused by heredity and early-generation selection should be conducted. The narrow heritabilities of ear diameter, bare tip length and yield was low, which should not be selected in early-generation.

Analysis on Combining Ability and Heritability of the Main Agronomic Characters for JA CMS in Brassica napus L.

Fifteen combinations crossed by five JA cytoplasmic male sterile lines （A1, A2, A3, A4, A5） and three restoring lines （R1, R2, R3） were selected to analyze the combining ability and heritability of nine main agronomic characters of Brassica na-pus L. to definite the application potential of these parent materials. The result showed that （i） the general combining ability （GCA） of male parents was R3＆gt;R2＆gt;R1 and that of female parents was A4＆gt;A1＆gt;A2＆gt;A5＆gt;A3; （i ） the special combining ability （SCA） of A2＆#215;R3 in plant height, number of branches, number of pods per plant and yield per plant was the best. The yield per plant of A2＆#215;R3, A1＆#215;R1 and A2＆#215;R1 ranked the first three places in the 15 combinations; （i i） the broad heritability of yield per plant was the highest, and that of the height of branches was the lowest. The com-prehensive characters of R3, A2 and A4 were better, which could be used to create new materials; （iv） good offspring were more likely to be chosen from the combina-tion with higher parental GCA, so the GCA and SCA should be considered com-prehensively when choosing parent and determining the optimal combinations.

Combining Ability Analysis on Yield Traits of Recombinant Inbred Lines in Hybrid Rice

A population of 140 recombinant inbred lines at F8 generation were obtained after seven successive generations of self-pollination using single seed descent（SSD） method from the F2 hybrids of three-line restorers Luhui 8258 with high combining ability and Yanghui 34. Then, the 140 inbred lines obtained above and their parents Luhui 8258 and Yanghui 34 were crossed with three different types of cyto-plasmic male sterile（CMS） lines（Gang 46 A, Ⅱ-32 A and Lu 98A） according to NCⅡ design. The resulting 426 combinations were planted at Deyang and Suining bases to test the combining ability and inheritance of five yield traits： yield per plant, panicle number per plant, filled grain number per panicle, seed setting rate and 1 000-grain weight. The results showed that the variances of both general and specific combining abilities of the five traits all reached a significant or extremely significant level at the two sites. The broad and narrow heritability of the yield traits（except 1 000-grain weight whose broad and narrow heritability were both over70%） were all below 50% at the two experimental bases, suggesting that the four traits were easily subjected to environment influence. Very significant positive correlation of general combining ability was found between yield per plant and other traits except 1 000-grain weight. The general combining ability variance showed a normal distribution among the recombinant inbred lines at two sites, right in line with inheritance of quantitative traits. So, the genes controlling rice general combining ability can be targeted by QTL mapping.

Combining Ability Analysis of Panicle Traits in Six CIMMYT Maize Inbred Lines

In this study, six CIMMYT maize inbred lines and five representative do- mestic maize inbred lines were used as parental lines. By using incomplete diallel cross design, 30 hybrid combinations were developed to analyze the general com- bining ability （GCA）, specific combining ability （SCA） and total combining ability （TCA） of seven panicle traits in six CIMMYT maize inbred lines. The results showed that CIMBL98 and GEMS13 were excellent inbred lines with good compre- hensive performance; CIMBL98 × 340 and GEMS13×Chang 7-2 were superior combinations.

Analysis of Combining Ability of Drought Tolerance in Maize

By using complete-diallel cross design（Griffing method I）, the influence of the combination of different high-yield genotypes of maize on the drought tolerance of their offspring, the general combining ability, the specific combining ability and the back cross effect of drought tolerance between parents and the main genetic parameters for drought tolerance were analyzed. The result indicated that there were significant differences in general combining ability effects（GCA） of maize; there were highly significant differences in special combining ability effects（SCA）; there was no significant difference in reciprocal effects（R）. There were apparent differences in drought tolerance among six parents; to be specific, Zheng 58 had the highest drought tolerance, while PH4CV had the lowest. Improving drought-tolerant parents with Zheng 58, Ji 853 and Xinzi 8717 had gain superiority effects on the increase of drought tolerance in offspring. The influence of the genetic additive effect on the drought tolerance of offsprings varied with different parents and combinations. Therefore, the expression of drought tolerance inheritance genes was determined only by the additive and non-additive genetic effects but had little relationship with reciprocal effects. The selection of drought tolerance of maize should be conducted at higher generations.

Analysis of Combining Ability for Resistance of Sugarcane Parents and Cross Combinations to Brown Stripe Disease

[Objectives] The paper was to screen resistant sugarcane varieties against brown stripe disease,and to breed disease-resistant germplasm resource.[Methods]The combining ability for resistance to sugarcane brown stripe disease was analyzed based on 23 female parents,21 male parents and 29 cross combinations. [Results]The average heritability of resistance to sugarcane brown stripe disease successively were female parents（ 95. 3%）,cross combinations（ 93. 0%）and male parents（ 79. 1%）. The general combining ability of 12 female parents showed negative effect,including Pma 98-40,Yacheng 93-26,Yunrui 05-283,Yuetang 91-976,Chuanzhe 19,ROC10,Yunzhe 06-80,ROC26,Zhanzhe 74-141,K86-110,Yunzhe 03-194 and ROC25. The general combining ability of 10 male parents showed negative effect,including Q 199,Yunrui 06-649,Yunrui 05-733,CP 84-1198,CP 88-1762,Yacheng 84-125,Yunrui 05-784,Yuetang 00-236,CP72-3591 and CP 94-110. The special combining ability of 16 cross combinations showed negative effect,including Pma 98-40 × Yunrui 05-649,Yacheng 93-26 ×Yunrui 05-733,Yunrui 05-283 × Q199,Yuetang 91-976 × CP 84-1198,Chuanzhe 19 × CP 88-1762 and ROC10 × Yuenong 73-204. [Conclusions] There were significant differences in combining ability among female parents,male parents and cross combinations,which were mainly controlled by additive and non-additive gene.

Heterosis and combining ability:a diallel cross of three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino

We conducted a complete diallel cross among three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino to determine the heterosis and the combining ability of growth traits at the spat stage.The three populations were collected from Qingdao(Q) and Dalian(D) in China,and Miyagi(M) in Japan.We measured the shell length,shell width,and total weight.The magnitude of the general combining ability(GCA) variance was more pronounced than the specific combining ability(SCA) variance,which is evidenced by both the ratio of the genetic component in total variation and the GCA/SCA values.The component variances of GCA and SCA were significant for all three traits(P<0.05),indicating the importance of additive and non-additive genetic effects in determining the expression of these traits.The reciprocal maternal effects(RE) were also significant for these traits(P<0.05).Our results suggest that population D was the best general combiner in breeding programs to improve growth traits.The DM cross had the highest heterosis values for all three traits.

Heterosis and Combining Ability for Major Yield Traits of a New Wheat Germplasm Shannong 0095 Derived from Thinopyrum intermedium

The wheatgrass, Thinopyrum intermedium （Host） Barkworth ＆ DR Dewey, shows many beneficial characteristics, such as big spikes and high resistance to many diseases. To transfer the beneficial genes of this species, many wheat- Thinopyrum intermedium alien chromosome lines were developed. Of them, Shannong 0095 （SN0095）, a disomic substitution, has long spikes and flag-leaves, and thus may be an important genetic resource for wheat yield improvement. In order to realize its heterosis and combining ability on major yield traits, a 7 ×7 complete diallel design was made according to Griffing＇s Method-1. The results showed that heterosis for spike length （SPL）, flag-leaf area （FLA）, number of spikes per plant （NSP）, number of spikelets per spike （NSL）, kernels per spike （KPS）, 1 000-kernel weight （TKW） and grain yield per plant （GYP） existed in all the crosses by SN0095, but heterobeltiosis occurred only for KPS, TKW, and GYP. The relative mid-parent heterosis （RMH） and relative high-parent heterosis （RHH） for GYP, which valued as high as 35.32 and 29.92% respectively, were the highest among all the traits mearsured. Though additive and non-additive gene effects and cytoplasmic effects （or cytoplasmic-nuclear interaction effects） were found in governing all the traits measured above, additive gene action played a predominant role. The results also showed that SN0095 was the best-general combiner for SPL and FLA, and high-general combiner for NSP amongst all the parents. Estimates of specific combining ability （SCA） showed that SN0095 could also make high-SCA combinations for GYP, such as SN0095 × Jimai 19 （JMI9）. SN0095 could be a unique and important parent in hybrid wheat breeding programs.

Combining Ability and Genetic Effects of Germination Traits of Brassica napus L.Under Waterlogging Stress Condition

Cross combinations from six rapeseed cultivars and lines were evaluated under waterlogging stress condition in order to understand the genetic mechanism of waterlogging tolerance of Brassica napus L.and provide reasonable improvement programs.There were six germination traits investigated on combining ability and heritability using complete diallel crossing method designed for 30 combinations from those six cultivars and lines.The traits included relative root length,stem length,fresh weight per plant,survival rate,electrical conductivity,and vigor index.After flooding treatment,the six traits of parents and F1 were analyzed.The general combining ability（GCA） and special combining ability（SCA） of germination traits were analyzed using Griffing I method.Among 30 cross combinations,the GCA was significantly different among six waterlogging resistance traits.The SCA of these traits was significantly different except the SCA of electrical conductivity.As a representative trait of waterlogging tolerance in rapeseed,relative vigor index had the highest narrow heritability and relatively low broad heritability.The cultivars Zhongshuang 9 and P79 had higher tolerance potential to waterlogging stress.It can be concluded that combining ability and genetic effects of relative vigor index during germination stage could be used to identify the waterlogging tolerance of rapeseed in breeding program.

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.

Combining Ability Analyses of Net Photosynthesis Rate in Pepper (Capsicum annuum L.)

In perspective of breeding high-yield hybrid pepper varieties, combining ability analysis of net photosynthesis rate at different phases of flowering and fruit setting in pepper was made with 15 cross combinations from 6 parents by （1/2） n （n- 1） diallel crosses. There are relatively large differences not only in general combining ability （GCA） effect among different parents and at different phases of flowering and fruit setting, but also in specific combining ability （SCA） effect among different hybrids. There are relatively large GCA effects in late parents but relatively less GCA effects in early parents. No obvious laws have been found in the relationship between SCA effects and maturity of hybrids. Variances of SCA are larger than those of GCA. Heritability is less but influence of environment is larger. Correlation analysis of combining ability between net photosynthesis rate and agronomic character or resistances to main diseases has showed that correlation coefficients of GCA are relatively large at the medium phase and the late phase of flowering and fruit setting. Net photosynthesis rate is more relative to leaf characters and fruit characters. Correlation coefficients of SCA are relatively large at the early phase and the late phase of flowering and fruit setting. Net photosynthesis rate is more relative to leaf characters and plant characters at the early phase but to plant characters and fruit characters at the late phase. Correlation coefficients of SCA between net photosynthesis rate and resistances to main diseases are larger than those of GCA. The combining abilities of net photosynthesis rate at different phases of flowering and fruit setting are positively correlated with those of yield per plant. The combining ability is an important parameter of breeding of high photosynthesis hybrid pepper varieties.