Combining ability analysis for harvest index in winter wheat

Summary Cereal breeders have used harvest index (HI) as a selection criterion in segregating generations to identify physiologically superior lines with improved partitioning of total assimilate into grain. Information on combining ability for HI of the hard red winter wheat (Triticum aestivum L.) cultivars of the Southern Great Plains is not available. A study was undertaken to examine HI of seven genetically diverse winter wheat parents, evaluate their general combining ability (GCA) and specific combining ability (SCA) effects, and study correlations of HI with several agronomic traits. The seven parents were crossed in a half-diallel mating design to produce 21 crosses. The F₁'s, their F₂ progenies, and the parents were evaluated in replicated field tests at Stillwater and at Lahoma, OK. The combining ability analysis was performed using Griffing's Method 4, Model 1. The results showed significant variation among parents for HI. The GCA and the SCA effects were mostly inconsistent between generations and between environments. However, parents with consistently high HI and positive GCA estimates were identified. The progeny with high HI mostly resulted from parents with high GCA estimates. The correlations between HI and agronomic traits indicated that improvement in HI should also result in high grain yield, early maturity, and short plant height.     

Combining ability and gene action for maturity and agronomic traits in different heterotic groups of maize inbred lines and their diallel crosses

Combining ability information is necessary for selection of suitable advanced lines for hybridization and identification of promising hybrids for development of improved varieties. A number of 14 maize (Zea mays L.) inbred lines and 91 related crosses were evaluated over two years, 2008 and 2009, in a temperate-zone of Iran. The objectives of the study were to identify the best general and specific combiners, heterosis and type of gene actions responsible for agronomic traits. Except for grain yield and growing degree day to milky, significant general (GCA) and specific (SCA) combining ability were observed for all traits. The Baker ratio for plant height (0.15), ear height (0.26), growing degree day to milky stage (0.04), and grain yield (0.002) showed the predominance of non-additive gene effects in the expression of these traits. The heterosis observed for grain yield, grain number, pollination period, ear and plant height was considerably higher than that observed for other traits. The correlations (r) of F₁ means and SCA effects were positive and significantly higher than that of r (F₁, mid-parents) and r (F₁, heterosis) for all the traits except cob percent, growing degree days to silking, and physiological maturity. MO17, K3547/5, and K3615/2 had negative GCA effects for growing degree day to milky stage and maturity. Among hybrids, MO17 × K3653/2, B73 × K3651/2, and K3545/6 × K3493/1 with positive SCAs for pollination period and grain yield had also negative SCA effects for degree day to silking and milky stages. Therefore, the use of these inbred lines and hybrids increases the response to selection for increasing grain yield and early maturity in maize.     

Combining ability of seed vigor and seed yield in soybean

Studies have shown no consensus in relationships between seed yield and vigor in soybean [Glycine max (L.) Merrill]. The lack of information regarding the inheritance of seed vigor prompted this study to determine the types of gene action and combining ability estimates for seed vigor and its related traits. Five high and six low seed vigor soybean genotypes were crossed in a diallel, and selfed to produce 55 F₂ progenies, which were examined, along with the parents, for seed vigor, yield, and seed weight. Significant genotype and environment effects were found for seed vigor and yield. General combining ability (GCA) effects for seed vigor and seed yield were significant (p≤ 0.01) and larger than specific combining ability (SCA) effects. Significant GCA and SCA effects were found for seed weight, indicating that both additive and non additive genetic effects were involved in conditioning seed weight. The ratios of mean square, 2GCA / (2GCA+SCA), were 0.96 for seed vigor and 0.93 for seed yield. These ratios indicated that additive gene effects were more important than non additive gene effects for seed vigor and seed yield in these crosses. Mean seed vigor(83.8%), as determined by accelerated aging germination, and mean seed yield (2,155 kg ha^-1)in high vigor × high vigor crosses were higher than the high vigor × low vigor and low vigor × low vigor crosses. Mean percent accelerated aging germination rates in F₂ populations from diallel crosses were significantly related to mid-parent seed vigor(r² = 0.52^**) and midparent seed size (r² = 0.31^**). These results indicated that levels of seed vigor can be improved through breeding, while maintaining high yields because of the predominance of GCA effects in both seed vigor and seed yield. This revised version was published online in July 2006 with corrections to the Cover Date.     

Advanced cycle pedigree breeding in sunflower. II: combining ability for oil yield and its components

Combining ability is one of the most important information breeders use to identify superior inbred lines on the basis of their performance in hybrid combinations. The objectives of our study were (i) to quantify the importance of general combining ability (GCA) and specific combining ability (SCA) variances for seed yield, oil content and oil yield; and (ii) estimate GCA and SCA effects of seed yield, oil content and oil yield of inbred lines developed from advanced cycle pedigree breeding populations in sunflower. A total of 109 female S₃ cytoplasmic male sterile (CMS) lines from four bi-parental populations in advanced cycle pedigree breeding were crossed with two testers to form 218 testcross hybrids (TCHs). The TCHs were then evaluated in three environments. Variance component analysis results showed predominance of σ²gca over σ²sca for seed yield and oil yield indicating that superior TCHs can be identified based on positive and significant GCA effects of the female lines. For oil content σ²sca was predominant over σ²gca indicating that selecting for TCHs with high oil content would be best among line × tester combinations and not among female S₃CMS lines per se. The proportion of GCA and SCA effects in the best five TCHs in each breeding population also confirmed the predominance of GCA effects over SCA effects for seed yield and oil yield while for oil content both GCA and SCA effects appear to be important, with SCA effects having more influence than GCA. The best selection strategy would therefore be to capture the GCA in the early stages of inbreeding and then SCA for the few unique combinations when lines are almost fixed.     

Combining ability for yield,protein and oil of peanut lines from South American centers of diversity

Summary Ten peanut (Arachis hypogaea L.) lines, two from each of five centers of diversity in South America, and the F₂ generation of all possible crosses among them were used to characterize the variation for yield, fruit and seed traits and protein and oil content and to determine the breeding potential of the parents. Two of the parental lines belong to subspecies hypogaea and the other eight to subspecies fastigiata.Several crosses gave heterotic responses for yield. The parents of the crosses with significant heterosis generally came from different centers of diversity.Variation among both general and specific combining abilities was significant for all traits with the exception of the SCA estimate for protein percent. The component of variation for GCA was larger than the SCA component for all traits.A Spanish line and a Valencia-like intermediate line from the Guarani region had the highest GCA effects for fruit yield, seed yield and meat content and transmitted consistently their characteristics to their F₂ progeny. Some lines showed significant but small maternal effects for oil, protein and oil + protein percent. Differences between reciprocal crosses were significant for fruit length, fruit weight and oil + protein percent.A significant portion of the variation among crosses was explained by differences among parental lines within centers of diversity. This supports the fact that centers are founded because of the diversity of the peanuts grown there.The performance of parental lines per se was useful in predicting the performance of the lines in hybrid combination for all traits except fruit yield.Paper number 6141 of the Journal Series of the North Carolina Agricultural Research Service (USA). This work was partially supported by CSRS Research Agreement 701-15-51.     

食葵主要经济性状的配合力及杂种优势分析

选用农家种改良过的6个食葵细胞质雄性不育系和4个优良的分枝型恢复系为亲本,按NCⅡ遗传交配设计,配成24个F₁杂种,研究了9个主要经济性状,即株高、茎粗、生育期、盘径、单盘总粒数、单盘实粒数、结实率、百粒重、单株产量的配合力及杂种优势表现。结果显示：（1）不育系中有8个性状,恢复系中有7个性状的一般配合力差异达显著或极显著水平;有4个性状的特殊配合力差异达到显著或极显著水平;（2）株高、茎粗、生育期、盘径、百粒重等5个性状主要受基因的加性效应控制;单盘总粒数、单盘实粒数、结实率、及单株产量等4个性状则受基因的加性效应和非加性效应共同影响;（3）从GCA分析看,参试的不育系以A6最为理想,A2次之;恢复系则以C3最为理想。从SCA分析看,组合A2C1单株产量效应值最高;（4）杂种优势分析表明,大部分经济性状存在杂种优势,甚至相当一部分存在超亲优势,并且这些优势都是可利用的,F₁多倾向于早熟、粗壮、高杆、大盘、多粒亲本。     

水稻广亲和品种农艺性状的配合力分析

用９个水稻不育系与３个广亲和品种进行不完全双列杂交，对其杂交组合１０个性状的配合力效应分析结果表明，就杂种Ｆ１主要农艺性状而言，亲本的一般配合力效应比组合特殊配合力效应更为重要；株高、单株有效穗数、穗长、每穗实粒数、结实率、单株粒重、千粒重等性状，以一般配合力作用为主，而每穗总粒数、生育期、着粒密度等性状虽以一般配合力作用为主，但特殊配合力的作用也不可忽视；株高、单株有效穗数、穗长、每穗实粒数。结实率、单株粒重等性状以广亲和品种的一般配合力作用为主；生育期、每穗总粒数、千粒重、着粒密度等性状以不育系的一般配合力作用为主。     

Heterosis and combining ability for grain yield and other agronomic traits in winter triticale

Hybrid breeding is a widely discussed alternative for triticale. Heterosis as well as general (GCA) and specific combining ability (SCA) effects were estimated for eight agronomic traits. The experiment comprised 24 F₁ hybrids, produced by a chemical hybridizing agent, together with their six female and four male parents, grown in drilled plots in two locations. In comparison with the mid‐parent values, hybrids averaged a 6.4 dt/ha (10.1%) higher grain yield, 8.4% more kernels per spike, a 6.8% higher 1000‐kernel weight, 9.7% lower falling number (FN) and 4.4% greater plant height. SCA effects for grain yield were significant and ranged from 4.5 to 6.9 dt/ha for grain yield. Together with GCA x location interactions, they explained most of the variation. For 1000‐kernel weight, GCA effects were predominant. SCA and interactions with location accounted for most of the variation in FN, whereas interactions were negligible for plant height. Correlations between mid‐parent and hybrid performance and between GCA and per se performance of parents were tight for all traits except grain yield, which allows for pre‐selection of parental lines. Although the amount of heterosis in triticale at present is closer to wheat than to rye, by selecting parents for combining ability and identifying heterotic patterns, grain yield heterosis of up to 20% appears sufficiently encouraging to embark on hybrid breeding.     

芝麻配合力的研究

本文对54个芝麻杂交组合10个性状进行配合力分析,结果得出:一般配合力方差明显大于特殊配合力方差,表明这些性状的遗传主要受加性基因控制.同一亲本不同性状或同一性状不同亲本间的一般配合力和组合的特殊配合力相差很大.即使双亲的一般配合力都为负值,也不能排除获得特殊配合力较高的组合.特殊配合力与双亲一般配合力均值呈显著、极显著的正相关.果轴长、单株产量、单株蒴数、株高和千粒重5个性状的总配合力与单株实产呈极显著的正相关,腿高和黄尖长呈极显著的负相关.上述分析结果有利于芝麻亲本选配及杂种后代的选择.     

Genetic combining ability estimates in the F<Subscript>1</Subscript> and F<Subscript>2</Subscript> generations for yield,its component traits and alkaloid content in opium poppy (<Emphasis Type="Italic">Papaver somniferum</Emphasis> L.)

The F ₁ and F ₂ generations of a twenty parent fractional diallel cross of opium poppy (P. somniferum L.) were analyzed for combining ability for ten quantitative and five quality (alkaloids) traits. The results indicated significant differences among the parents for combining ability for all the traits. The GCA and SCA components of variances were significant for all the characters. However, the SCA component of variance (δ ²s) was predominant indicating the preponderance of non-additive gene effect for all the traits except for leaves/plant and papaverine in F₁ hybrids. The average degree of dominance (δ ²s/δ ²g) was more than unity indicating over dominance and also confirming non-additive mode of gene action. Among the parents IS-16, IS-13 and NBRI-1 for early flowering, BR226 and BR241 for branches/plant, capsule weight/plant, seed yield/plant and husk yield/plant, BR227 for leaves/plant, UO1285 for capsule size and opium yield/plant, NBRI-5 for husk yield/plant, morphine, codeine, and thebaine and ‘Papline’ for plant height and papaverine content were found good general combiners. Parent ND1001 was good combiner for codeine and narcotine content. Inclusion of good general combiners in a multiple crossing program or an intermating population involving all the possible crosses among them subjected to bi-parental mating may be expected to offer maximum promise in breeding for higher opium, seed yield and alkaloid contents.     

籼型杂交水稻农艺性状的配合力研究

如何有效利用杂种优势已成为水稻增产的关键。本研究按照NCII遗传交配设计,将三系野败型杂交水稻的恢复系和微核心种质构成的115份优异籼稻品种,分别与4个两系不育系及1个三系不育系测交,分析各农艺性状配合力、遗传力及相互关系。结果表明,除单株有效穗数、主穗实粒数外,其他农艺性状一般配合力差异均达到极显著水平;除单株有效穗数外,其他各农艺性状特殊配合力差异也均达到极显著水平。同一组合的不同性状、同一亲本的不同组合所表现出的特殊配合力效应都有所不同,表明亲本的一般配合力水平与特殊配合力间没有固定的联系。在育种实践中,选取一般配合力高的亲本,同时兼具较高特殊配合力是获取高产杂交稻组合的关键。     

Combining ability of soybean (Glycine max) for low phosphorus tolerance on acidic soils of Western Ethiopia

Determining the gene actions governing the inheritance of traits of interest has paramount importance in designing a breeding approach to improve the progeny populations. This study was undertaken to determine the combining ability of nine selected parental lines in the F₂/F₃ segregating populations for low P tolerance. The experiment was laid out in an alpha lattice design in two locations, that is Mettu and Assossa of Western Ethiopia that are characterized by soils with low P and pH. General combining ability (GCA) effects were highly significant for grain yield, pod length, days to maturity and plant height, while specific combining ability (SCA) effects were highly significant for grain yield, 100-seed weight, pod length and plant height. The parent Hardee-1 was identified as the best general combiner for yield, number of seeds per pod, pod length, plant height and pod number. The results suggest that additive gene action was important for several of the studied traits, implied by significant GCA effect, which might indicate selection for these traits could be effective in later segregating generations.     

Prediction of F6 line performance from F3 families in spring oilseed rape. I. Yield and other agronomic traits

Summary The reliability of a selection among crosses based on a cross prediction in early generations was investigated in spring rapeseed. The performance of the parents, the F₂ generation, and random F₃ lines from four crosses were used to predict the probability of finding superior recombinant lines. These predictions were made for two years and compared with the observed performance of F₆ lines in the second of these two years and in an additional year. Predicted and observed performances coincided reasonably for the characters plant height, standability, maturity and an index calculated from seed yield, oil content and protein content. For seed yield and flowering time, the predictions were very unreliable. In conclusion, prediction methods may be useful in rapeseed breeding, if quality traits are of major commercial interest.     

Relationship of plant height and days to maturity with resistance to spot blotch in wheat

A total of 1,407 spring wheat (T. aestivum) lines of Indian and CIMMYT (International Maize and Wheat Improvement Centre, Mexico) origin were evaluated for plant height, days to maturity and resistance to spot blotch (caused by Bipolaris sorokiniana) during the 1994–95, 1995–96 and 1996–97 crop seasons. The frequency distribution of genotypes, based on disease score ignoring the growth stages, differed from the distribution in which disease score was assessed on a similar growth stage. Two crosses each,between `tall resistant × dwarf susceptible' and `late resistant × early susceptible' genotypes, were made. The evaluation of homozygous resistant lines in the F₃, F₄ and F₅ generations of both crosses showed a wide range of plant height and days to maturity. These lines showed significant differences for plant height and days to maturity but did not show a significant difference for AUDPC values of spot blotch. The correlation coefficients for AUDPC versus plant height or days to maturity were weak, i.e., – 0.336 and 0.061, respectively. Results indicated that resistance to spot blotch severity was independent of plant height and days to maturity in progenies from these crosses.     

Sunflower seed yield as influenced by some agronomic and seed characters

Summary An investigation was made to the interrelationships of agronomic and seed characters and their effect upon seed yield. Twenty genotypes of sunflower (Helianthus annuus L.) from diverse origin were studied in spring and autumn season, 1989.Most of the studied characters exhibited different relationships in spring and autumn seasons. The correlations between plant height and oil content, 100-achene weight and number of achenes per head and plant height and head diameter were, however, consistent in both seasons and across the seasons. Stepwise multiple regression analysis identified six relevant characters on which path analysis was done.Path analysis indicated that yield components like head diameter, number of achenes per head and 100-achene weight had comparatively smaller direct effects on seed yield (0.22, 0.15 and 0.23, respectively). Days to physiological maturity, plant height and oil content had relatively stronger direct effects on seed yield (0.33, 0.38 and 0.29, respectively). Days to physiological maturity, plant height and head diameter had considerable indirect effects. Head diameter, 100-achene weight and number of achenes per head were indentified as selection criteria for yield improvement.     

矮秆超大穗小麦亲本与多抗丰产小麦主要农艺性状的配合力评价及遗传分析

为了进一步挖掘矮秆超大穗小麦亲本在遗传育种中的应用潜力,为小麦高产、超高产育种选择优良亲本和最优杂交组合提供理论依据,选用5个矮秆超大穗小麦品种（系）作为父本,8个多抗丰产小麦品种（系）作为母本,按NCII遗传交配设计,采用8×5不完全双列杂交法,配制了40个杂交组合,对小麦亲本及杂种F1的株高、主穗长、单株穗数、结实小穗数、主穗粒数、主穗产量、单株产量、千粒重8个性状进行了考察,并在基因型方差分析显著的基础上进行了配合力评价及遗传力分析。结果表明：父本中A1、A3、A4是综合性状优良的亲本,其多数性状的一般配合力均较高,特别是穗长、主穗粒数、结实小穗数、主穗产量、单株产量的一般配合力高,而株高的一般配合力效应值较低,是很理想的矮秆超大穗多粒亲本材料。母本中B5、B6单株穗数一般配合力较高,株高的一般配合力效应值较低,可作小麦高产杂交育种的矮秆多穗型亲本使用。结合特殊配合力效应分析：组合B5×A3单株穗数、主穗产量、单株产量、千粒重特殊配合力效应最高,株高特殊配合力效应较低,可作为的矮秆、多穗、粒重高且高产的重点杂交组合。B2×A4主穗长、单株产量、单株穗数特殊配合力效应都较高,而株高特殊配合力效应低,可作为矮秆大穗高产的重点杂交组合。遗传力分析表明：单株产量、千粒重、主穗长、主穗产量皆在70%以上,表明这4个性状的广义遗传力较大,受环境影响较小,而狭义遗传力的分析除主穗长、主穗粒数、主穗产量、株高大于50%,其余4个性状均低于50%,说明受环境影响大,不宜早期选择,应该适当推迟选择的代数。     

Characterization and genetic control of germination-emergence responses of grain sorghum to salinity

Summary When grain sorghum is grown in saline soils, one cause of low yield is poor crop establishment. The objectives of this study were to assess the response of grain sorghum to salinity in the germination-emergence stages, study the inheritance of salt tolerance at this stage, and determine the relative contribution to final emergence of salt effects during imbibition, and after onset of germination. Twelve inbred lines and 18 F1 hybrids, resulting from an incomplete 6×6 factorial mating design, were tested for germination and emergence in folded paper at 10 salt concentrations, from 1.8 to 36 dSm^-1. The mean EC₅₀ (the electrical conductivity at which the variable score declines by 50%) for emerged seedlings production was 21.2 dSm^-1. Large genotypic differences were observed for salt tolerance at germination and emergence stages, which were not related to the viability of seeds, and poorly related to seed weight (considered as an estimate of intrinsic seed vigor). In the hybrids, these differences were due to SCA and female GCA for emergence, and female GCA for germination, though the male GCA was also significant for both characters. Line per se performance was significantly correlated to individual GCA estimates for emergence, but not for germination. Heterosis was only detected in three crosses for final emergence and in one cross for germination. The genetic differences in final emergence were mainly due to effects occurring after the onset of germination rather than a consequence of effects during imbibition.     

Ga糯玉米自交系的配合力分析与评价

摘要：利用不完全双列杂交NCⅡ设计,以3个经遗传改良的Ga糯玉米自交系为父本,与8个糯玉米自交系进行杂交。对24个杂交组合进行农艺性状鉴定,分析Ga糯玉米自交系主要农艺性状的配合力效应。结果表明,父、母本各性状的一般配合力和特殊配合力效应均达极显著差异。Ga糯玉米自交系具有良好的配合力,其中,CM327的一般配合力效应比较高,其组配的杂交种在产量、穗长、行粒数等性状上具有明显优势,具有很好的杂优利用潜力。Ga糯玉米自交系的选育利用,有助于糯玉米种质的扩增与杂种优势的利用。     

Growth habit and gene pool effects on inheritance of yield in common bean

Summary To satisfy farmer and consumer preferences, breeding efforts to increase yield potential in common bean must take into account the interrelated effects of growth habit, seed size, maturity, and gene pool on yield expression in segregating populations. To examine the relationships among these traits, a genetic study was conducted to determine the effect of growth habit on yield and seed size in crosses among five bean lines from diverse gene pools. Two parental bean lines had determinate, type I growth habits and large seed size typical of the Neuva Granada-Andean gene pool. Two other lines were tropical Mesoamerican types with type II growth habits and small seed size; and the fifth line, G13625, a landrace of the Jalisco gene pool from the Mexican highlands, had a type IV climbing growth habit and medium seed size. Individual F₂ plants from each cross and parental lines were evaluated for growth habit and yield component traits under high input field conditions. The following season, the evaluations were repeated on random F₃ plants. Of the five parental lines, only G13625 showed significant GCA effects for yield in both the F₂ and F₃ generations. Improved yielding ability of G13625 progeny was associated with an increased expression of climbing bean growth habit traits: guide length, climbing ability, node number on main stem, and plant height. Crosses between Andean x Mesoamerican and Andean x Jalisco genotypes, as well between growth habit type I (Andean x Andean) and between type II (Mesoamerican x Mesoamerican) had very low parent-offspring heritability values for yield. Yield heritability was only significant for crosses between Mesomerican x Jalisco gene pools. An apparent simple genetic control of growth habit modification towards semi-climbing and climbing types is proposed as the major reason for increased yields in these crosses. No genetic linkage between genes controlling growth habit and seed size was detected which might restrict the development of high yielding large-seeded type II lines.     

大麦若干经济性状的遗传特性分析

按Hayman方法对8×8完全双列杂交F_1的6个性状进行基因效应分析与模型检验,株高、穗长、实粒数符合加性-显性模型.株高、实粒数为部分显性,加性方差和显性方差均显著,基因的加性效应比显性效应更重要;穗长为超显性,显性基因效应比加性基因效应更重要.对杂交F_1、F_2进行配合力效应值分析表明,一般配合力方差和特殊配合力方差对所研究性状均重要,多数性状为加性基因效应占主导.亲本85G63、81-18、82-14为最佳配合者,其主要经济性状一般配合力好.杂交F_1各性状均有明显杂种优势,组合间和性状间的优势具有显著差异,以单株籽粒产量优势最强,其余依次为实粒数、穗长、株高、小穗粒数和千粒重.