Showing papers on "Diallel cross published in 2014"

Formation of Heterotic Groups and Understanding Genetic Effects in a Provitamin A Biofortified Maize Breeding Program

Abstract: Developing biofortified maize ( Zea mays L.) cultivars is a viable approach to combating the wide spread problem of vitamin A deficiency among people for whom maize is a staple food. To enhance CIMMYT’s provitamin A maize breed ing efforts, this study: (i) evaluated whether sep aration of experimental maize lines into groups based on maximizing their molecular-markerbased genetic distances (GD) resulted in het erosis for among-group crosses, (ii) assessed genetic effects (general and specific combining ability, GCA and SCA) for grain yield and provita min A concentrations in hybrids among 21 inbred lines representing the three proposed groups, and (iii) assessed the association between grain yield and provitamin A concentrations. The lines were crossed following a partial diallel design resulting in 156 hybrids that were evaluated at four environments with two replications of onerow plots. The first plant in each plot was selfpollinated to produce grain for provitamin A analysis. Significant but small yield advantage of among- versus within-group crosses (0.47 Mg ha -1 , P < 0.05) suggested that the groups identi fied by maximizing GD could be a practical start ing point for further breeding work to develop useful heterotic groups. Furthermore, the GDproposed heterotic groups were improved by later revising some line assignments to groups using estimates of SCA effects. General com bining ability effects were significant (P < 0.01) for all traits, whereas SCA effects were weak ( P < 0.05) or not significant for provitamin A carot enoid concentrations, indicating that these were controlled primarily by additive gene action. Grain yield was not significantly correlated with provitamin A concentration, indicating that both traits could be improved simultaneously.

Determination of heterotic groups for tropical Indica hybrid rice germplasm

Abstract: Two heterotic groups and four heterotic patterns were identified for IRRI hybrid rice germplasm to develop hybrid rice in the tropics based on SSR molecular data and field trials. Information on heterotic groups and patterns is a fundamental prerequisite for hybrid crop breeding; however, no such clear information is available for tropical hybrid rice breeding after more than 30 years of hybrid rice commercialization. Based on a study of genetic diversity using molecular markers, 18 parents representing hybrid rice populations historically developed at the International Rice Research Institute (IRRI) were selected to form diallel crosses of hybrids and were evaluated in tropical environments. Yield, yield heterosis and combining ability were investigated with the main objectives of (1) evaluating the magnitude of yield heterosis among marker-based parental groups, (2) examining the consistency between marker-based group and heterotic performance of hybrids, and (3) identifying foundational hybrid parents in discrete germplasm pools to provide a reference for tropical indica hybrid rice breeding. Significant differences in yield, yield heterosis and combining ability were detected among parents and among hybrids. On average, the hybrids yielded 14.8 % higher than the parents. Results revealed that inter-group hybrids yielded higher, with higher yield heterosis than intra-group hybrids. Four heterotic patterns within two heterotic groups based on current IRRI B- and R-line germplasm were identified. Parents in two marker-based groups were identified with limited breeding value among current IRRI hybrid rice germplasm because of their lowest contribution to heterotic hybrids. Heterotic hybrids are significantly correlated with high-yielding parents. The efficiency of breeding heterotic hybrids could be enhanced using selected parents within identified marker-based heterotic groups. This information is useful for exploiting those widely distributed IRRI hybrid rice parents.

Reciprocal Diallel Crosses Impact Combining Ability, Variance Estimation, and Heterotic Group Classification

Abstract: Questions such as the following often arise: "Should reciprocal crosses be included in a dial - lel?" and "Would their inclusion in a diallel impact grain yield (GY), estimates of general (GCA) and specific combining ability (SCA) effects, and heterotic group classification in maize ( Zea mays L.)?" We evaluated a 12-parent maize dial - lel cross (Griffing's Method 3 and Method 4) in three environments to determine (i) if recipro - cal crosses impact GY of crosses and GCA and SCA effects, (ii) if reciprocal crosses influence the GCA and SCA and residual variance esti - mates in a diallel analysis, and (iii) if reciprocal crosses impact maize heterotic group classifica - tion. The results showed that inclusion of recip - rocal crosses in a diallel greatly impacted GY and estimates of GCA and SCA effects. Under the assumption of a random-effects model, the inclusion of reciprocal crosses caused the resid - ual and GCA variances to decrease and the SCA variances to increase as the number of parental lines increased in a diallel cross. Because inclu - sion of reciprocal crosses impacted GY and SCA estimates, reciprocal crosses would have great impact on maize heterotic group classification. The maize heterotic groups might be classi - fied differently with and without the inclusion of reciprocal crosses. Based on our dataset from southwest China, three heterotic groups seemed to be an ideal number for improving maize- breeding efficiency.

Genetic Variability and Correlation Studies of Grain Yield and Related Agronomic Traits in Maize

Abstract: A total of fourty two maize hybrids produced through a full diallel mating design and seven parental inbred lines were evaluated in three sites located at different agro-ecological zones in Kenya to determine the genetic parameters governing the inheritance of grain yield and related agronomical traits. The genetic parameters studied among the traits included the mean performance, genotypic variances, phenotypic variances, genotype by environment variances, broad sense heritability and phenotypic and genotypic correlation coefficients. Significant differences were recorded for all traits studied thereby revealing the diversity of the maize genotypes. The grain yield and days to maturity which showed high heritability had low genotypic variances suggesting the involvement of non-additive gene action which could be utilized through heterosis breeding. Ear height and plant height showed the highest heritability and high genotypic variances suggesting the preponderance of additive gene action. Grain yield was positively and strongly correlated with ear height and plant height. The tall plants with high ear placement gave better yields and this could be attributed to the high dry matter accumulation function carried out by the high number of leaves possessed. The positive relationships observed in this study imply that the desirable traits in these hybrids could be exploited in further breeding activities for the development of composites and synthetics for the resource constrained maize farmers who cannot access hybrid seeds every year.

Genetic analysis of salt tolerance at seedling and reproductive stages in rice (Oryza sativa)

Abstract: Salinity is a major abiotic stress that limits rice production across rice areas as high-yielding modern rice varieties are generally sensitive to salt stress. The study was conducted to deduce heritability and combining ability estimates of rice for various morphological and physiological traits using a 7 × 7 full-diallel-cross analysis at seedling and reproductive stages. The salinity stress treatment was 12 dS m−1 at the seedling stage and 8 dS m−1 at the reproductive stage. Diallel analysis revealed high for salinity tolerance scores and shoot height, moderate for shoot dry weight and root dry weight and low for Na+ and K+ concentrations and K+/Na+ ratio. The low-to-moderate narrow-sense heritability for number of panicles, number of fertile spikelets, grain weight, spikelet fertility and K+/Na+ ratio suggests a large breeding population and delayed selection for tolerance until later generations. Significant maternal effects indicate that selection of the female parent is very important for desired trait development. The results of this study confirmed that salinity tolerance at the seedling and reproductive stages is regulated by a different set of genes that could be pyramided using different donors to enhance the level of tolerance.

Combining ability analysis in bread wheat

Abstract: Combining ability analysis was studied in a 10 × 10 half diallel set of bread wheat (Triticum aestivum L.). The analysis of variance for combining ability revealed that the mean squares due to both general combining ability (GCA) and specific combining ability (SCA) were highly significant for number of effective tillers per plant, length of spike, number of spikelets per spike, peduncle length of spike, number of grains per spike, grain weight per spike, 100-grain weight and grain yield per plant. This indicated that both additive and non-additive genetics variances played a vital role in the inheritance of all these eight traits.The GCA and SCA ratio (σ2GCA/σ2SCA) was less than unity for all the traits indicated that non-additive component play relatively greater role in the inheritance of all the eight traits.The line, HW 5018 and HI 1544 were good general combiners for grain yield per plant and some of its component traits. Nine crosses exhibited significant and positive SCA effects for grain yield per plant. The highest SCA effect for grain yield per plant was exhibited by the cross HW 5018 x K 604 followed by RAJ 4136 x UAS 281, KYZ 300 x RAJ 4136, KYZ 300 x HW 5018 and GW 173 x RAJ 4136. The cross KYZ 300 x RAJ 4136 was found most promising having high SCA effect together with per se performance for grain yield per plant, number of effective tillers per plant, grain weight per spike and 100-grain weight which could be further exploited in practical plant breeding programme.

Combining ability for yield and fruit quality in the pepper Capsicum annuum

Abstract: The objective of this study was to determine the effects of the general and specic combining abilities (GCA and SCA, respectively) of 15 characteristics and to evaluate the most promising crosses and the reciprocal effect between the hybrids of six parents of the Capsicum annuum species. Six parents, belonging to the Horticultural Germplasm Bank of Centro de Ciencias Agrarias of Universidade Federal da Paraiba, were crossed in complete diallel manner. The 30 hybrids generated and the parents were then analyzed in a completely randomized design with three replicates. The data were submitted to analysis of variance at 1% probability, and the means were grouped by the Scott-Knott test at 1% probability. The diallel analysis was performed according to the Grifng method, model I and xed model. Both additive and non-additive effects inuenced the hybrids' performance, as indicated by the GCA/SCA ratio. The non- additive effects, epistasis and/or dominance, played a more important

Combining Ability of Certain Agronomic Traits in Quality Protein Maize under Stress and Nonstress Environments in Eastern and Southern Africa

Abstract: Growing maize (Zea mays L.) hybrids tolerant to drought and low-nitrogen (N) stress would significantly reduce yield losses occurring in Africa. This study evaluated the performance of quality protein maize (QPM) F 1 hybrids, and general (GCA) and specific combining ability (SCA) of QPM inbred lines for grain yield and other agronomic traits under stress and nonstress environments. A diallel cross of 15 QPM inbred lines was evaluated under drought and low-N stresses and optimal conditions in a total of 17 environments in Eastern and Southern Africa. Significant varia tions were observed among the hybrids for all measured traits. TZMI703 ´ (6207QB/6207QA), GQL5 ´ (6207QB/6207QA), and CML511 ´ (6207QB/6207QA) were identified as the best single crosses across environments. The GCA and SCA mean squares were significant for all measured traits, indicating that additive and nonadditive genetic effects were important in this set of genotypes under all test environments. The GCA effects were more important under drought stress, and SCA effects were more important under low-N and optimal conditions for grain yield. There was preponderance of GCA effects for most agronomic traits tested in all environmental conditions. Inbred lines CML159SR, GQL5, CML159, and CML312SRQ exhibited favorable GCA effects for grain yield under stress and optimal conditions, indicating that the genetic systems controlling a given trait under different conditions are at least partially similar. Cross combinations with favorable SCA effects for grain yield and other traits were also identified. Generally, this study provided evidence that good performance can be achieved under stress and nonstress conditions in QPM germplasm.

Assessing the usefulness of GGE biplot as a statistical tool for plant breeders and agronomists

Abstract: Genotype main effect plus genotype-by-environment interaction (GGE) biplot produces a graphical display of results that facilitates a better understanding of complex genotype-by-environment interaction in multi-environment trials of breeding and agronomic experiments. However, the full potential and weaknesses of this powerful tool are not fully understood by breeders, agronomists, entomologists and pathologists. The objective of this paper was to review the usefulness of this statistical tool and enumerate some of its weaknesses. Its main application has so far been in the analysis of multi-environment data. It has been used to analyze the performance of crop cultivars under multiple stress environments, from which ideal cultivars, mega-environments, and core testing sites were identified. More recently, GGE biplot has been employed in genetic analysis of diallel data to estimate the combining abilities and identify heterotic groups among inbred parents. Genotype-by-trait biplot has also been utilized in trait profile analysis, and in identification of traits that are reliable for indirect selection of a target primary trait. Two major shortcomings of this tool are (i) failure to identify more than two distinct, contrasting groups in diallel studies and (ii) lack of statistical tests for most of its graphical displays. Other aspects of GGE biplot that need further study and development are (i) estimation of genetic variances, covariances, and heritability, including the analysis of data generated from North Carolina Designs I, II, and III as well as other genetic designs, considering their importance in plant breeding programs; (ii) analysis of Quantitative Trait Loci (QTL) data for proper understanding of the genetic constitution of each individual plant or line; and (iii) analysis of Genotype-by-pathogen or insect strain interaction data. Nevertheless, GGE biplot has helped greatly in the accurate analysis and interpretation of data from breeding and agronomic field evaluation experiments.

Analysis of genetic effects on a complete diallel cross test of Betula platyphylla

Abstract: The study utilized the offspring of a 5 × 5 diallel cross of Betula platyphylla as the experimental material. Tree height (H), diameter at breast height (DBH) and stem straight degree (SSD) were measured at the fourth and eighth growth year (SSD were measured only in the eighth growth year). ANOVA analyses showed that growth traits in different growth years were significant among families (P < 0.01). There existed extremely significant correlations between H and DBH in the same year. Although the sequencing of average H and DBH of different families were vicissitudinous at the 4th and 8th year, there also existed significant correlations between H and DBH in different year. The general combining ability, special combining ability (SCA) and reciprocal effect (REC) of different hybridized combinations were also different remarkably. The mean square of SCA was significantly higher than GCA, implied that the non-additive effect played major roles. When B5, B8 and MB15 were selected as parents, the offspring performed perfectly in traits of H, DBH and SSD at the eighth growth year respectively. B5 × XB11, B8 × XB11 and B8 × MB15 had highest SCA values in traits of H, DBH, and SSD at the eighth growth year respectively. Consequently, in order to achieve optimal outcomes, seed orchard building and clonal propagation should be considered simultaneously in birch’s genetic improvement process.

Balance between a Higher Degree of Heterosis and Increased Reproductive Isolation: A Strategic Design for Breeding Inter-Subspecific Hybrid Rice

Abstract: The application of heterosis (hybrid vigor) has brought great success to plant breeding, particularly of hybrid rice, achieving significant yield increases. Attempts to explore the heterosis of inter-subspecific hybrids between indica and japonica rice, which result in even greater yield increases, have greatly increased in the past decades. However, because of the reduced seed setting rate in F1 hybrids as a result of increased reproductive isolation, the application of inter-subspecific hybrids in rice has slowed. Understanding the balance between heterosis and the reproductive isolation of inter-subspecific hybrids will facilitate the strategic design of inter-subspecific hybrid breeding. In this study, five indica and seven japonica rice varieties were chosen as the parental lines of a complete diallel mating design. Data from six group traits from all of the hybrids and inbred lines were collected. We found that the grain weight per plant, grain number per panicle, tiller per plant, thousand grain weight and plant height, which reflected increased heterosis, were associated with the genetic divergence index (GDI) of the parents. Meanwhile, owing to the reduced seed setting rate, which was also associated with the parents' GDI, the grain production of the hybrids was negatively affected. After analyzing the relationships between the GDI of indica-japonica parents and the grain weight per plant of the F1 hybrids, an ideal GDI value (0.37) for the two indica-japonica parents that could provide an optimal balance between the inter-subspecific heterosis and reproductive isolation was proposed. Our findings will help in the strategic design of an inter-subspecific hybrid rice breeding program by identifying the ideal indica and japonica parents for a hybrid combination to achieve hybrid rice with an optimal yield. This strategic design of an inter-subspecific hybrid rice breeding program will be time saving and cost effective.

Diallel analysis among 16 maize populations adapted to the northern U.S. Corn Belt for grain yield and grain quality traits

Abstract: Genetically diverse germplasm is needed to increase frequency of favorable alleles of economically important traits in maize improvement. The objectives of this study were to determine the genetic components involved in grain yield and grain quality traits, and provide preliminary assessment of useful heterotic groups and patterns from a large sample of maize populations adapted to the northern U.S. Corn Belt. Sixteen populations were used in the diallel mating design following Gardner–Eberhart Analysis II to estimate variety (v i ) and heterosis (h ij ) genetic effects for grain yield and grain quality traits. Specific heterosis (s ij ) and predicted means of population crosses for grain yield were used to evaluate the heterotic relationships among the populations. Data for grain yield and grain quality traits were generated in partially balanced single lattice experiments across North Dakota (ND) locations in 2010, 2011, and 2012. Analyses of variance showed significant differences among genotypes. Heterosis effects explained most of the differences among diallel entries for grain yield, while v i effects had greater influence on grain quality traits. NDL, EARLYGEM 21c, NDSCD(FS-CS)C2, NDSS, and NDSM(M-FS)C9 were identified as elite populations for grain quality improvement. NDSS × NDBS22(R-T1)C9 and NDBS1011 × EARLYGEM 21c showed high s ij effects for grain yield with good grain quality. NDSS and EARLYGEM 21c represent stiff stalk synthetic (SSS) group, and NDBS1011 fall under non-SSS group. Further studies need to validate the heterotic group of NDBS22(R-T1)C9. Recurrent and pedigree selection programs will be established for selected populations and population crosses to integrate pre-breeding with cultivar development.

Diallel analysis of maize inbred lines for grain yield, oil and protein content

Abstract: This study aimed to investigate the combining ability and heterotic effects on grain yield (GY), oil content (OC) and crude protein (CP) in tropical and temperate maize lines. Hybrids and inbred lines were evaluated in a complete diallel scheme without reciprocals, in two experiments in randomized blocks with three replications. The partitioning of the sum of squares for general (GCA) and specific (SCA) combining ability indicated that both additive and non-additive effects were involved in the genetic control of the studied traits. The estimates of the quadratic components showed predominance of non-additive genetic effects in the trait control. However, for OC and CP, the non-additive effect had a clearly negative influence on the hybrid combinations. The cross L6x L10was considered promising, because it associated RG positively with BP and OC.

Heritability analysis of putative drought adaptation traits in sweetpotato.

Abstract: Drought stress is a constraint to sweetpotato ( Ipomoea batatas L (Lam)) production in many parts of Sub- Saharan Africa In this region, crop farming is predominantly rain fed; therefore, breeding for drought tolerance is appropriate for addressing low sweetpotato productivity since the crop is largely produced by resourcelimited farmers As part of developing drought tolerant genotypes in Uganda, this study aimed at determining the nature of genetic control and heritability associated with selected drought adaptation traits Ten randomly chosen clones from each family were evaluated for three traits; tuber yield, crop vigour and canopy cover as well as five traits (leaf senescence, leaf rolling, leaf retention, SPAD readings and root vertical pulling) at 80% field capacity and under no watering conditions for three weeks in a glasshouse Diallel analysis revealed significant effects for both GCA and SCA, indicating both additive and non-additive gene actions were present Baker’s ratio was large in most traits (>050), indicating predominance of additive effects Heritability coefficients were high in most traits (>050), indicating that genetic gains can be achieved by conventional breeding The predominance of additive genetic control realised in this study implies that use of small numbers of parents with suitable GCA effects is most appropriate for drought tolerance improvement in sweetpotato Key Words : Combining ability, diallel, Ipomoea batatas

Genetic effects of combining ability studies for yield and fibre quality traits in diallel crosses of upland cotton (Gossypium hirsutum L.)

Abstract: The present study was carried out to investigate the diallel analysis in upland cotton (Gossypium hirsutum L.) by involving seven parents and their 42 cross combinations. All the characters were predominantly controlled by additive gene action except number of sympodial branches, single plant yield and bundle strength. Non additive gene action was controlled for the characters sympodial branches, single plant yield and bundle strength. The parent BW4-1 had superior per se performance for single plant yield, boll weight, lint index, number of bolls per plant, seed index, and micronaire followed by MCU 13 which had recorded high per se for single plant yield, lint index, seed index and number of sympodial branches. The parent TCH 1726 exhibited positive and significant gca effect for single plant yield, ginning percent, number of sympodial branches, boll weight and plant height. Based on high per se performance and high gca effect, the parent MCU 13 was considered as best general combiner as it had significantly greater values for single plant yield, number of sympodial branches, lint index and seed index. The hybrids KC 2 × TCH 1726 and TCH 1705 × MCU 3 had recorded high per se for single plant yield, number of bolls per plant and number of sympodial branches. Based on sca effects, KC 2 × TCH 1726 showed significant sca effects for single plant yield and number of sympodial branches. Key words: Cotton, Combining ability, gca, fibre quality traits, sca, single plant yield.

Deducing Hybrid Performance from Parental Metabolic Profiles of Young Primary Roots of Maize by Using a Multivariate Diallel Approach

Abstract: Heterosis, the greater vigor of hybrids compared to their parents, has been exploited in maize breeding for more than 100 years to produce ever better performing elite hybrids of increased yield. Despite extensive research, the underlying mechanisms shaping the extent of heterosis are not well understood, rendering the process of selecting an optimal set of parental lines tedious. This study is based on a dataset consisting of 112 metabolite levels in young roots of four parental maize inbred lines and their corresponding twelve hybrids, along with the roots' biomass as a heterotic trait. Because the parental biomass is a poor predictor for hybrid biomass, we established a model framework to deduce the biomass of the hybrid from metabolite profiles of its parental lines. In the proposed framework, the hybrid metabolite levels are expressed relative to the parental levels by incorporating the standard concept of additivity/dominance, which we name the Combined Relative Level (CRL). Our modeling strategy includes a feature selection step on the parental levels which are demonstrated to be predictive of CRL across many hybrid metabolites. We demonstrate that these selected parental metabolites are further predictive of hybrid biomass. Our approach directly employs the diallel structure in a multivariate fashion, whereby we attempt to not only predict macroscopic phenotype (biomass), but also molecular phenotype (metabolite profiles). Therefore, our study provides the first steps for further investigations of the genetic determinants to metabolism and, ultimately, growth. Finally, our success on the small-scale experiments implies a valid strategy for large-scale experiments, where parental metabolite profiles may be used together with profiles of selected hybrids as a training set to predict biomass of all possible hybrids.

Heterotic grouping and patterning of quality protein maize inbreds based on genetic and molecular marker studies

Abstract: An investigation was done to study the heterotic grouping and patterning in quality protein maize inbreds. Biochemical screening resulted in the choice of 3 inbreds each with high (UQPM 2, UQPM 4, and UQPM 21) and low (UQPM 18, UQPM 19, and UQPM 20) lysine and tryptophan contents respectively for genetic studies using diallel analysis. UQPM 20 × UQPM 18 was notable as it possessed high standard heterosis and specific combining (sca) effect for grain yield, protein, tryptophan, and lysine. Based on yield sca, the 6 parental inbreds were classified into 3 heterotic groups. Intergroup cross UQPM 20 × UQPM 18 was the best in yield and quality. The superior heterotic pattern was flint × dent. In genetic diversity analysis using simple sequence repeat markers, the inbreds of the best hybrid, UQPM 20 × UQPM 18, lay in same cluster but different subclusters. Correlations between genetic distance and sca effects were low for grain yield, which hampers the prediction of heterosis from molecular data alone.

Gene effect and heterosis in Capsicum baccatum var. pendulum

Abstract: Heterosis has been exploited in Capsicum annuum commercial hybrids; however, the use of heterosis in C. baccatum still remains to be explored, and studies related to the genetics and breeding of this species are scarce. The present study aimed to estimate the combining ability of five parents of C. baccatum var. pendulum , representatives of two distinct types of fruits (namely, lady's finger and cambuci), to calculate heterosis and to evaluate the agronomic potential of the hybrids for yield and fruit quality. The hybrids were produced from a complete diallel without reciprocals. The parents and hybrids were evaluated under field conditions in a randomized block design with three replications, and the following traits were assessed: number of fruits per plant, fruit weight, yield per plant, fruit length, fruit diameter and soluble solids. All traits were significant for general and specific combining ability, indicating that additive and non-additive effects are involved in the genetic control of these traits. The hybrid combinations between the types lady's finger and cambuci provided elongated fruits with smaller diameters and greater weight compared with the parents of the cambuci type. However, these factors did not lead to a significant increase in the yield per plant due to the decreased number of fruits except in hybrid UENF 1616 x UENF 1732. Considering only the parents and hybrids within each type of fruit, the genitor UENF 1624 (lady's finger) and the hybrid UENF 1639 x UENF 1732 (cambuci x cambuci) stood out for achieving a high yield per plant.

Study on Combining Ability and Heterosis of Yield and Its Components in Pepper (Capsicum annum, L.).

Abstract: Six parental genotypes and their fifteen F1 hybrids in a diallel cross system, without reciprocals, were used in the present study to estimate heterosis percentage relative to both mid and better parents, potence ratios and combining ability (general and specific) for some characters in pepper (Capsicum annum, L.). The experiment was conducted at the Experimental Station Farm of Fac. Agric. Minufiya Univ., Shebin El Kom, Egypt, during two successive summer seasons of 2012 and 2013. The obtained results reflected generally that the mean squares for general (GCA) and specific (SCA) combining abilities were highly significant for all the studied traits, suggesting the presence of both additive and non-additive gene effects in the inheritance of the various studied characters. However, the high ratio of GCA: SCA mean squares showed that GCA effect was more important than SCA effect. The preponderance of GCA effects implied that these characters would respond favorably to direct selection. Estimates of GCA effects showed that the best combiner parents werer found to be those of P3 and P1 for early fruits number, P6 and P1 for early fruits weight, P3 and P2 for total yield as fruits number and weight, P1 for fruit diameter, P4 and P6 for fruit length, P6 and P1 for average fruit weight. For pericarp thickness and vitamin C content, the parental genotype P1 was the best combiner, while P2 for TSS content. Estimates of SCA effects showed that the F1 cross 1×6 reflected the highest value in all the studied traits. For heterotic effect, hybrid vigour was detected in many characters; i.e., early fruits yield, total yield, fruit length, vitamin C and total soluble solids contents. These results suggested that hybrid vigour is available for commercial production of sweet pepper hybrid, and that isolation of pure lines from the progenies of heterotic F1's is a possible way to enhance the fruits yield and fruit quality.

Parental Selection of Hybrid Breeding Based On Maternal and Paternal Inheritance of Traits in Rapeseed (Brassica napus L.)

Abstract: Parental selection is crucial for hybrid breeding, but the methods available for such a selection are not very effective. In this study, a 6×6 incomplete diallel cross was designed using 12 rapeseed germplasms, and a total of 36 hybrids together with their parental lines were planted in 4 environments. Four yield-related traits and seed oil content (OC) were evaluated. Genetic distance (GD) was estimated with 359 simple sequence repeats (SSRs) markers. Heterosis levels, general combining ability (GCA) and specific combining ability (SCA) were evaluated. GD was found to have a significant correlation with better-parent heterosis (BPH) of thousand seed weight (TSW), SCA of seeds per silique (SS), TSW, and seed yield per plant (SY), while SCA showed a statistically significant correlation with heterosis levels of all traits at 1% significance level. Statistically significant correlations were also observed between GCA of maternal or paternal parents and heterosis levels of different traits except for SS. Interestingly, maternal (TSW, SS, and OC) and paternal (siliques per plant (SP) and SY) inheritance of traits was detected using contribution ratio of maternal and paternal GCA variance as well as correlations between GCA and heterosis levels. Phenotype and heterosis levels of all the traits except TSW of hybrids were significantly correlated with the average performance of parents. The correlations between SS and SP, SP and OC, and SY and OC were statistically significant in hybrids but not in parents. Potential applications of parental selection in hybrid breeding were discussed.

Efficiency of circulant diallels via mixed models in the selection of papaya genotypes resistant to foliar fungal diseases.

Abstract: Diallel crossing methods provide information regarding the performance of genitors between themselves and their hybrid combinations. However, with a large number of parents, the number of hybrid combinations that can be obtained and evaluated become limited. One option regarding the number of parents involved is the adoption of circulant diallels. However, information is lacking regarding diallel analysis using mixed models. This study aimed to evaluate the efficacy of the method of linear mixed models to estimate, for variable resistance to foliar fungal diseases, components of general and specific combining ability in a circulant table with different s values. Subsequently, 50 diallels were simulated for each s value, and the correlations and estimates of the combining abilities of the different diallel combinations were analyzed. The circulant diallel method using mixed modeling was effective in the classification of genitors regarding their combining abilities relative to the complete diallels. The numbers of crosses in which each genitor(s) will compose the circulant diallel and the estimated heritability affect the combining ability estimates. With three crosses per parent, it is possible to obtain good concordance (correlation above 0.8) between the combining ability estimates.

Combining ability of white corn genotypes with two commercial hybrids

Abstract: White corn is a special type of corn used to make «canjica», a dish appreciated in many regions in Brazil. However, there is a shortage of scientific information, genetic statistical estimates for breeding programs and white corn cultivars for producers to produce grits. The objectives of the present study were to assess two groups of white corn genotypes in a partial diallel cross for the main agronomic traits, estimate the combining ability of the parents and identify promising white corn hybrids for yield and grits quality. The fourteen topcross hybrids obtained from a partial Diallel (2 x 7), using seven genotypes and two commercial testers of the white maize (IPR 119 e IPR 127). The resulting hybrids and the two commercial controls were assessed in the 2011/2012 in the experimental center Agronomic Institute in Campinas (IAC) in growing season at the in Campinas and Tatui, Sao Paulo state, Brazil. A randomized block design was used with four replications. The traits assessed were male flowering (MF), female flowering (FF), plant height (PH), ear height (EH), percentage of broken and lodged plants (Ld + Br) and grain yield (GY). There were two treatments for all the traits assessed in the two locations and some hybrids presented higher mean production than the commercial controls. The P7, P1, P3, and P2 genotypes presented the best general com¬bining ability for all the traits assessed. The best estimates for specific combining ability were observed in the P6 x P9, P2 x P9, and P7 x P8 hybrids, indicating dominant loci systems in the genetic control of the traits PH, EH and GY.

Combining ability of pod yield and related traits of groundnut (Arachis hypogaea L.) under salinity stress.

Abstract: A study was performed using F 1 diallel population without reciprocals to assess the mode of inheritance of pod yield and related traits in groundnut with imposed salinity stress. Heterosis was found for pod number and yield. Data on general and specific combining ability (gca and sca) indicated additive and nonadditive gene actions. The gca: sca ratios were much less than unity suggesting predominant role of nonadditive gene effects. Cultivars “Binachinabadam-2” and “Dacca-1” and mutant M 6/25/64-82 had the highest, second highest, and third highest pod number, as well as gca values, respectively. These two cultivars and another mutant M 6/15/70-19 also had the highest, second highest, and third highest pod yield, as well as gca values, respectively. Therefore, “Dacca-1”, “Binachinabadam-2”, M 6/25/64-82, and M 6/15/70-19 could be used as source of salinity tolerance. Cross combinations showing high sca effects arising from parents with high and low gca values for any trait indicate the influence of nonadditive genes on their expression. Parents of these crosses can be used for biparental mating or reciprocal recurrent selection for developing high yielding varieties. Crosses with high sca effects having both parents with good gca effects could be exploited by pedigree breeding to get transgressive segregants.

Estimation of heterosis for yield and some yield components in bread wheat (triticum aestivum l.)

Abstract: Heterosis estimated over mid and better parents in 7 x 7 half diallel design for ten different cross combinations of bread wheat. The crosses were estimated for yield and yield contributing characters. The maximum heterobeltiosis was recorded for Productive tillers per plant (47.64%) and Weight of grains per spike (26.41%). The crosses DI9 x MP-4080, LOK-62 × PHS-0622, PHS-0622 × MP-4080 and DI-9 × PHS-0622 were identified as promising for many desirable traits and they may be useful in exploiting hybrid vigour. The data provides information on heterotic advantage of important yield and associated components. The highest heterotic genotypes can be exploited in future breeding programs to attain self-sufficiency in food grains. However, comprehensive field evaluation over locations and years is advocated for the crosses having significant heterosis before their commercial exploitation.