Analysis of diallel cross in Phaseolus aureus roxb

Summary In a diallel cross of Phaseolus aureus involving five varieties, combining ability and gene action for grain yield, grains per pod and pods per plant were estimated. The study indicated that both general combining ability and specific combining ability effects were significant and important for all three traits. Partial dominance for grain yield and partial to over-dominance for grains per pod and pods per plant were observed. Dominant genes seem to govern the inheritance of all three characters. Combining ability, and graphical and component variance analyses indicated that the grain yield and two of its components are influenced by both additive and non-additive gene action.     

Genetics of transgressive segregation for yield and yield components in wheat

Three crosses of spring wheat (Triticum aestivum L. em Thell) involving six cultivars (WC29, WH291, SGP 14, RAJ. 1972, WH377 and HD 2329) were selected on the basis of combining ability analysis to study genetics of transgressive segregation for tillers/plant, grains/spike, 1000 grain weight and grain yield/plant using various mating designs. Diallel analysis indicated that both additive and non- additive components were significant for all the characters. On the basis of general combining ability and specific combining ability effects, the parents WH 291 and WH 377 were found to be good general combiners for tillers/ plant, 1000 grain weight and grain yield/plant. For grains/spike SGP 14 was found to be a good general combiner. The cross WH 377 × HD 2329 for tillers/plant, SGP 14 × Raj. 1972 for grains/spike and grain yield/plant and WC 29 × WH 291 for 1000 grain weight were found to be good cross combinations. Generation mean analysis indicated that the additive-dominance model was inadequate for all the characters in all the crosses except for 1000 grain weight in WC29 × WH291. Additive component was more pronounced than non-additive components for all the characters in all the crosses except for tillers/ plant in WH 377 × HD 2329. Predictions for transgressive segregants from F₃ was more accurate than that from generation mean analysis. However, prediction from both the sources were equally efficient if additive-dominance model was adequate. In general, observed frequencies of transgressive segregants were more in F₂ and BIPi than F₄ but the majority of them were discarded on progeny testing. Biparental mating had an impact in increasing the frequencies of transgressive segregants for different characters in all the crosses. The crosses, WH 377 × HD 2329 for grain yield/ plant, SGP 14 × Raj. 1972 for tillers/plant and WC 29 × WH 291 for grains/spike and 1000 grain weight were found to be potential crosses for transgressive segregants. A comparison of combining ability of parents and crosses, and observed and predicted frequencies of transgressive segregants indicated that the potential crosses for transgressive segregants were those that had high sea effects and involved high and low general combiners. The crosses involving low general combiners irrespective of their sea effects showed poor performance with respect to transgressive segregation.     

Combining ability in the F1 and F2 generations of diallel cross in hexaploid wheat (Triticum aestivum L. em. Thell)

The F(1) and F(2) progenies of a ten-parent diallel cross (excluding reciprocals) of hexaploid wheat (Triticum aestivum L. em. Thell) were analyzed for combining ability for quantitative and quality traits. The results indicated significant differences among the parents for general combining ability (gca) and crosses for specific combining ability (sca) for all the characters studied. The gca and sca components of variance were significant for all the traits. However, the gca component of variance was predominant indicating the predominance of additive gene effects for the traits studied. Among the parents Durgapura 65, HD 2285, Lok-1, Raj 1972 and HD 2329 were the best general combiners for grain yield and average to high combiners for tillers per plant, grain yield per spike, grains per spike and 1000-grain weight. The best specific crosses for grain yield were Sonalika x WH 157, HD 2428 x Durgapura 65, Durgapura 65 x Sonalika, HD 2428 x Lok-1 and CPAN 3004 x Raj 1972. The parent Raj 1972, Lok-1 and HD 2285 were the best general combiners for grain yield and protein content, however, Raj 3077 was the best general combiner for protein content. The most suitable specific crosses for protein content were HD 2329 x HD 2285, HD 2428 x Raj 1972 and CPAN 3004 x WH 157. Most of the specific crosses for grain yield as well as protein content involved high x average, average x average and average x poor general combiners. To ensure further increase in grain yield along with high protein, combinations of desirable yield components is advocated. Inclusion of F(1) hybrids showing high sca and having parents with good gca, into multiple crosses and/or bi-parental mating, or diallel selective mating could prove a worthwhile approach for further improvement of grain yield in bread wheat.     

Genetic analysis of agronomic characters in chickpea

Summary Twenty-eight diallel trials over 8 years and two locations were analysed to estimate genetic variances for agronomic characters of chickpea (Cicer arietinum L.). The data were analysed according to Method 4 and Model I of Griffing (1956). Days to flowering, plant height, and seed size were found to be predominantly under additive inheritance and were highly predictable. Both additive and non-additive genetic components were important for seed yield, number of branches, pods per plant, and seeds per pod. Although both general combining ability (gca) and specific combining ability (sca) varied significantly with generation, components of gca mean squares were invariably much larger than gca x generation interaction components, indicating that either the F₁ or the F₂ generation can be used to estimate the gca components effectively. Combined diallel analysis of F₂s over locations revealed the importance of combining ability x location interactions and emphasized the need for testing over more than one location for the precise estimation of combining ability. The implications of these findings and those reported earlier in the literature on the breeding strategies/methods for the genetic improvement of agronomic characters in chickpea are discussed.ICRISAT journal article no. 1199     

Combining ability analysis over F1-F5 generations in diallel crosses of bread wheat

Summary Combining ability studies for grain yield and its primary component traits in diallel crosses involving seven diverse wheat cultivars of bread wheat (Triticum aestivum L.) over generations F₁-F₅ are reported. The general and specific combining ability variances were significant in all generations for all the traits except specific combining ability variance for number of spikes per plant in the F₅. The ratio of general to specific combining ability variances was significant for all the traits except grain yield in all the generations. This indicated an equal role of additive and non-additive gene effects in the inheritance of grain yield, and the predominance of the former for its component traits. The presence of significant specific combining ability variances in even the advanced generations may be the result of an additive x additive type of epistasis or evolutionary divergence among progenies in the same parental array. The relative breeding values of the parental varieties, as indicated by their general combining ability effects, did not vary much over the generations. The cheap and reliable procedure observed for making the choice of parents, selecting hybrids and predicting advanced generation (F₅) bulk hybrid performance was the determination of breeding values of the parents on the relative performance of their F₂ progeny bulks.     

Combining ability analysis over environments in diallel crosses of linseed (Linum usitatissimum L.)

Summary This paper reports on combining ability studies for yield and its component traits in diallel crosses involving ten ecogeographically and genetically diverse linseed (Linum usitatissimum L.) cultivars in the F₂ generation over three locations. The general combining ability (GCA) and specific combining ability (SCA) mean squares were significant at all three locations for all traits. Combined analysis over locations showed the same trend of significance. The ratio of GCA to SCA mean squares was significant for all the traits in individual location analysis as well as in combined analysis. This indicated the predominant role of additive gene effects in the inheritance of these characters. The GCA mean squares were several times larger than SCA mean squares for all the traits, indicating the presence of considerable magnitude of additive genetic variance and the additive x additive components of the epistatic variance. Consequently, effective selection should be possible within these F₂ populations for all characters. Significant genotype-location and GCA-location interactions indicated that more than one test location is required to obtain reliable information. The inexpensive and reliable procedure used for making the choice of parents was the determination of breeding values of the parents on the relative performance of their F₂ progeny bulks.Part of the thesis submitted by the senior author in partial fulfillment of the requirements for the Ph. D. degree of the Marathwada Agricultural University, Parbhani, 431 402, India     

Multivariate statistical analysis of grain yield and agronomic characters in Durum wheat

Summary Correlation, stepwise multiple regression and factor analyses were conducted on grain yield and a number of agronomic characters in the parental, F ₁ and F ₂ families originating from a 10 X 10 diallel cross in durum wheat. For the F ₁ diallel, the correlation analysis indicated that the number of spikes and kernels per plant and 1,000 kernel weight had the highest correlations with grain yield; for the F ₂ diallel, the number of spikes and kernels per meter, 1000 kernel weight and plant height showed most striking correlations with same.Stepwise multiple regression analysis indicated that, for the F ₁ diallel, number of kernels per plant, 1000 kernel weight and days to maturity were the most potent predictor variables for grain yield, accounting for 78% of its variability. For the F ₂ diallel, the number of kernels and number of spikes per meter, 1000 kernel weight and number of kernels per spike were the most potent predictors for grain yield, accounting for 91 % of its variability. Five common factors were extracted which explained 98.8% and 98.1% of the total variance in the F ₁ and F ₂ diallel, respectively. However, the importance of each of the five factors and the characters which loaded highly on each of them differed from generation to generation.Contribution No. 323 from Plant Science Department, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.     

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％）。     

Studies of heterosis,combining ability and inheritance of yield and yield components in a diallel cross of bengal gram (Cicer arietinum L.)

Summary A 5 X 5 diallel cross among well-adapted varieties of gram from different agroclimatic regions was studied for heterosis, combining ability and inheritance of days-to-flowering, primary branches, pods per plant, 100-seed weight and grain yield. A high degree of heterosis over mid-parent and better parent was observed for primary branches, no. of pods and grain yield, whereas very little heterosis was exhibited for days-to-flower and 100-seed weight. Crosses among lines of diverse origin generally gave higher heterosis and over-dominance than lines from the same region. Primary branch number, pod number, and grain yield exhibited positive over-dominance; days-to-flower showed negative over-dominance while 100-seed weight had no dominance. Both general and specific combining ability effects were significant for all the characters studied but g.c.a. effects appeared to be more important for days-to-flower, 100-seed weight and grain yield. Graphical analysis indicated additive effects for all the characters, with complete dominance for days-to-flower, no dominance for 100-seed weight and over-dominance for the other three characters. Dominant genes conditioned earliness, primary branch number and 100-seed weight. The role of various parents and crosses in planning a hybridization programme has been discussed.     

Combining ability and parental evaluation in five selected clones of sugarcane (Saccharum sp. hybrids)

Summary Five Hawaiian commercial sugarcane (Saccharum sp. hybrids) clones were crossed in a full diallel. Four morphological characters were studied in the progeny: number of millable stalks per plant, stalk diameter, stalk length, and sucrose content. A fifth character, plant volume, was calculated from stalk number, stalk diameter and stalk length. The five selected parental clones were treated as fixed variables in the analysis. General combining ability (gca) was significant for all five characters; specific combining ability (sca) was significant for stalk diameter, stalk length, and plant volume. The variance for gca was large in all progeny populations. However, the variance for sca was large in the progeny of only some clones and/or for some individual characters. Parents were evaluated on the basis of their general combining ability: clone H49-3533 had high gca for sucrose content, while clone H53-5356 had high gca for plant vigor.Published with the approval of the Director as Journal Series Paper No. 455, Experiment Station, Hawaiian Sugar Planters' Association.     

Estimation of genetic parameters in barley (Hordeum vulgare L.)

Summary Four exotic and four indigenous strains of barley were used for making diallel crosses. The sets of parents and crosses making full, half and quarter diallel were analysed in a randomized block design for plant height, number of effective tillers, ear length, grain yield per plant, 100 grain weight and number of grains per ear.The three alternatives of diallel were similar with respect to the estimates of degree of dominance, general combining ability and specific combining ability, indicating that all these three methods of diallel were equally efficient. However, as the number of entries are minimum in quarter diallel, it would be economical in terms of cost, time and labour to estimate genetic parameters by this method. Average degree of dominance was found in the range of overdominance. The ranking of parents on the basis of their array mean was similar to the ranking based on gca effects. Similarly, the ranking of crosses on the basis of per se performance was similar to the ranking based on sca effects. This suggests that the selection of best general combiner or best cross combinations may be easier and more effective through array mean for per se performance rather than through high gca and sea effects, respectively. From among 56 crosses, IB-226 X X C-164 was the one which showed superiority for maximum number of characters followed by AB-12/59 X PTS-57. High sea effect for plant height, ear length, grain yield, 100 grain weight and number of grains per ear was the result of cross between parents having high X low general combining ability, indicating additive X dominance type of gene interaction. For number of effective tillers, high sca was produced by low x low general combiners, indicating dominance x dominance gene interaction.Part of a Ph. D. thesis submitted by senior author to Haryana Agricultural University, Hissar.     

Genetic studies on tissue culture response and some agronomical traits in Egyptian bread wheat

The main effort of wheat breeder is the detection of genes and to merge them in a particular genotype using most suitable combination. Five Egyptian cultivars of bread wheat (Triticum aestivum L.) were crossed in a half diallel mating design to produce 10 crosses. The genetic potential of embryogenic callus (EC%), plant regeneration (RGP%) response and its association with heading date (HD) and grain yield per plant (GY/P) were investigated. The results showed that GY/P was significantly and positively correlated with EC% and RGP%. The combining ability analysis showed that the magnitudes of general combining ability (GCA) were higher than those of specific combining ability (SCA) for both tissue culture response and agronomic traits. The promising crosses which exhibited desirable SCA effects, showed also high useful heterosis for all studied traits. The magnitudes of additive genetic variance (σ²A) were larger than those of non-additive ones (σ²D) for all studied traits except for number of days to heading. The estimates of narrow sense heritability were 84.56%, 82.13%, 43.46% and 70.28% for the percentage of EC%, RGP%, HD and GY/P, respectively. The genetic similarity percents based on RAPD markers ranged from 76% to 93% between the cultivars. The UPGMA cluster analysis revealed that the cultivars could be divided into two main clusters. The range of Euclidean distances based on morphological characters among the cultivars was relatively wide (4.37–27.87), indicating relatively high amount of phenotypic variation. A significant positive correlation between Euclidean distance and RAPD distance (0.72⁷) was found.     

Predicting hybrid value in bread wheat: biometric modelling based on a ”top-cross” design

Multi-environmental experimentation made it possible to compare 311 hybrids and their 59 parental lines for five characters: yield, two yield components (number of grains per m² and 1000-grain weight), height and date of heading. At all three sites, average high-parent heterosis exceeded 6%, and our results confirm that hybrids in general head as early as the earlier parent does and are as high as the taller parent. For the five characters studied ecovalences were significantly lower in the F1 than in the parents, indicating a higher level of homeostasis for hybrids. The experimental model, based on a ”top-cross” design comprised of 55 lines used as females and four testers, made it possible to implement different hybrid-value prediction models. For yield, by far the most important character to predict, the predictor based on the general combining ability and the per se value of the parents, appears to be the most interesting. The prediction remains, however, imperfect as specific combining ability (SCA) has a strong impact for this character. Attempting to take account of SCA in the prediction, by using a multiplicative model for ”male×female” interaction modelling, did not prove convincing. Received: 15 February 1999 / Accepted: 25 July 1999     

Specifity of Genetic Determination of Content of Photosynthetic Pigments in Triticale

Lines of winter hexaploid Triticale and their F₁ and F₂ hybrids differing in morphological structure, pigment contents, photosynthetic productivity, and grain crops were studied. F₁ hybrids received by crossing of Triticale lines contrasting in pigment contents showed in some cases a heterosis effect for chlorophyll (Chl) content per unit leaf area. Variation analysis demonstrated a polygenic control of Triticale pigment contents, and different rate of increase in F₂ generation. We found maternal type of heritability of Chl b content and Chl content in light-harvesting complex of photosystem 2.     

Genetic analysis of organogenesis in the cotyledons of zygotic embryos of sunflower (Helianthus annuus L.)

Crosses were made between five cytoplasmic male-sterile and five restorer sunflower inbred lines. Twenty-five F₁ hybrids and their parents were studied for their organogenesis ability in a randomized block design with four replications. Each replication per genotype consisted of ten petri dishes with four expiants. Regeneration medium consisted of full MS medium modified by the addition of hormones and solidified with 6 g/l agar. Statistical analysis showed that both general and specific combining abilities were significant for all of the organogenesis parameters studied, and both showed several significant positive or negative values. General combining ability values were usually higher than those of specific combining ability, indicating the importance of additive genetic control for organogenesis parameters in sunflower. Narrow-sense heritability for the number of explants producing shoots and roots was 65.8%, which suggests that organogenesis of currently inferior inbred lines in sunflower should be improved in a crossing program.     

Advanced backcross QTL analysis of a hard winter wheat × synthetic wheat population

Advanced backcross quantitative trait locus (AB-QTL) analysis was used to identify QTLs for yield and yield components in a backcross population developed from a cross between hard red winter wheat (Triticum aestivum L.) variety Karl 92 and the synthetic wheat line TA 4152-4. Phenotypic data were collected for agronomic traits including heading date, plant height, kernels per spike, kernel weight, tiller number, biomass, harvest index, test weight, grain yield, protein content, and kernel hardness on 190 BC₂F_2:4 lines grown in three replications in two Kansas environments. Severity of wheat soilborne mosaic virus (WSBMV) reaction was evaluated at one location. The population was genotyped using 151 microsatellite markers. Of the ten putative QTLs identified, seven were located on homoeologous group 2 and group 3 chromosomes. The favorable allele was contributed by cultivated parent Karl 92 at seven QTLs including a major one for WSBMV resistance, and by the synthetic parent at three QTLs: for grain hardness, kernels per spike, and tiller number. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Phenotypic and genetic analysis of spike and kernel characteristics in wheat reveals long-term genetic trends of grain yield components

Key message

Phenotypic and genetic analysis of six spike and kernel characteristics in wheat revealed geographic patterns as well as long-term trends arising from breeding progress, particularly in regard to spikelet fertility, i.e. the number of kernels per spikelet, a grain yield component that appears to underlie the increase in the number of kernels per spike.

Abstract

Wheat is a staple crop of global relevance that faces continuous demands for improved grain yield. In this study, we evaluated a panel of 407 winter wheat cultivars for six characteristics of spike and kernel development. All traits showed a large genotypic variation and had high heritabilities. We observed geographic patterns for some traits in addition to long-term trends showing a continuous increase in the number of kernels per spike. This breeding progress is likely due to the increase in spikelet fertility, i.e. the number of kernels per spikelet. While the number of kernels per spike and spikelet fertility were significantly positively correlated, both traits showed a significant negative correlation with thousand-kernel weight. Genome-wide association mapping identified only small- and moderate-effect QTL and an effect of the phenology loci Rht-D1 and Ppd-D1 on some of the traits. The allele frequencies of some QTL matched the observed geographic patterns. The quantitative inheritance of all traits with contributions of additional small-effect QTL was substantiated by genomic prediction. Taken together, our results suggest that some of the examined traits were already the basis of grain yield progress in wheat in the past decades. A more targeted exploitation of the available variation, potentially coupled with genomic approaches, may assist wheat breeding in continuing to increase yield levels globally.

     

小麦品质和农艺性状的配合力分析

依据田间试验和室内生化分析数据,按ｐｘｑ交配模式,对１０个冬小麦亲本２５个杂交组合Ｆ１的蛋白质含量,赖氨酸含量,穗粒重和千粒重的一般配合力和特殊配合力效应进行了分析。结果表明,除蛋白质含量的ｓｃａ外,其余性状的ｇｃａ和ｓｃａ效应均达极显著水平,表明在本研究中,基因的加性效应和非加性效应均起重要作用。由于一般配合力差δ＾２ｓｃａ大,表明基因的加性效应更加重要。根据ｇｃａ,ｓｃａ和δ＾２ｓｃａ估值,分     

Evaluation of circulant partial diallel crosses in maize

Summary The present study was conducted in maize (Zea mays L.) on crosses among 20 diverse parents. The materials were evaluated in four different environments for eight characters. Combining ability analysis was carried out following diallel and partial diallel crosses. The number of crosses per parent (s) varied from 3 to 19 and the results were studied to identify the critical value of s that would provide an adequate information with minimum resources. The S₅ partial diallel was as good as the S₁₉ for the detection of differences among general combining ability (GCA) effects. Even the S₃ gave adequate information in the case of characters with high heritability. However, partial diallel analysis was less efficient in detecting the differences due to specific combining ability (SCA) effects. These results varied with environments, and characters with low heritability were more prone to misinterpretation. GCA effects showed fluctuations in partial diallel analysis which were more pronounced in S₅ and S₃, particularly for characters with low heritability. The average standard error of difference between GCA effects increased with a decrease in s, with a steep slope for s < 7. The partial diallel analysis was more efficient for the estimation of the variance component of GCA than for SCA, as the estimate of SCA was biased upwards. Estimates of broad sense heritability obtained from the partial diallels agreed with the full diallel analysis better than the narrow sense estimates. Smaller partial diallels gave erratic estimates of heritability, particularly for the characters with low heritability.     

Genetic variation in resistance to vascular-streak dieback in cocoa (Theobroma cacao)

Summary Genetic variation in disease resistance to vascular-streak dieback (Vsd) was studied in 54 cocoa hybrid progenies from Trinitario x Amazonian crosses. The disease was assessed by the number of Vsd infected branches per tree, total length of infected branches, average depth of disease penetration within branches and percentages of infected and dead plants. Highly significant differences due to general combining ability for both Trinitario female parents and Amazonian male parents were obtained for all characters. Percent of dead plants was the only character where specific combining ability was also important. Gene effects were predominantly additive for most characters, indicating that selection for progenies resistant to Vsd is effective in the present breeding population. There is strong evidence that resistance to Vsd is in the form of horizontal resistance. It is polygenic and largely inherited as additive genes. Therefore, breeding for resistance is an effective means of controlling Vsd in Papua New Guinea.