Selfing and crossing methods were used to develop the cytoplasmic male sterility (CMS) lines from 2 elite F1 hybrids of CMS hot chilies. The pungency of the CMS lines was improved by backcrossing ...with the B cultivar. The first and second backcrossed progenies of the CMS lines showed significantly higher capsaicin contents than the F1 hybrids. One good female line K16 × BBC2 (K16), was selected and backcrossed with 3 good maintainer cultivars, C5, C9 and C0. Some incomplete male sterility of pollens was demonstrated in the F1 hybrids and the 1st backcrossed progenies while the partial sterility disappeared by the stage of the second and third generations of backcrossing. When K16 and P32 were crossed with restorers, fruit yields and yield components of certain F1 hybrids, parental lines and commercial varieties were significantly different. Heterosis of yield and yield components of the F1 hybrid chilies was significant. When K16 was used as a female parent, positive and significant heterosis of the F1 hybrids was the same as P32. Moreover, significant GCA of the restorer lines, C7, C8 and C9, was observed in some horticultural characteristics. Furthermore, significant differences of the specific combining ability of some characteristics were observed in a few F1 hybrids.
Root system architecture is important for common bean (Phaseolus vulgaris) adaptability to diverse environments. Beans employ complex adaptive root mechanisms for coping with multiple stresses in ...production environments. Understanding genetic control of root traits is central to improvement of common bean for adaptation to marginal environments. The objectives of this study were to (i) determine combining ability of root and agronomic traits and (ii) estimate the heritability and genetic correlation of root and agronomic traits in common bean. Four bean lines with superior root traits were crossed with four locally adapted varieties in a North Carolina II mating scheme to generate 16 crosses. The 16 F1s were selfed and advanced to F2 generation. Eight parents and their F2 progenies were evaluated in an alpha‐Lattice design with two replications. General and specific combing ability mean squares were significant (p ≤ .05) for all traits measured. General predictability ratios ranged from .47 to .68 across locations suggesting that both additive and non‐additive gene action modulate root traits and seed yield. Positive and significant (p ≤ .05) phenotypic and genetic correlations revealed significant association between root traits and yield. Moderate to high heritability estimates of between .43 and .67 were realized. Such estimates point to possible deployment of a successful selection programme. Genotype AFR398 displayed significant positive GCA effects among its crosses for both root and agronomic traits hence a potential candidate genotype for inclusion in a bean genetic improvement programme for marginal environments.
Fifty-seven lines of okra including ten parents, forty-five hybrids and two standard checks were evaluated in Randomized Block Design with two replications. Combining ability was carried out to study ...comparisons of lines in combinations for the traits days to 50% flowering, plant height at harvest, the number of branches per plant, the number of nodes per plant, days to first picking, the number of fruits per plant, the mean length of fruit, the mean weight of fruit, yield per plant , yield per plot , yield per hectare and reaction to yellow vein mosaic disease. The result revealed that the variance to general combining ability (gca) is less than specific combining ability (sca), ratio of that is less than unity indicated preponderance of non additive gene action for all the traits. The parent Akola Bahar was good general combiner, whereas, cross combination Shagun x VNR (Super Green) recorded a significant specific combining ability (sca) effects as far as yield is concerned.
Genetic advancement and gains in yield and related traits are dependent on the selection of best combiner parents and progenies under the prevailing growing conditions. This study was conducted to ...determine the combining ability effects of eight selected drought-tolerant groundnut parental lines and their F2 progenies under drought-stressed (DS) and non-stressed (NS) conditions to determine the gene actions involved in the inheritance of the studied traits and identify the best parents and progenies for further improvement of the crop for moisture stress tolerance. Experiments were conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in India during 2020 cropping season. Data on some of the important physiological, yield and yield component traits were collected. The general combining ability (GCA) effects of parents were significant (
P
< 0.05) for all assessed traits under all testing conditions, except for PB under DS and NS conditions in the glasshouse. The specific combining ability (SCA) effects of progenies were significant (
P
< 0.05) for all traits, except for PH across all testing environments and PB under field conditions. The genotype ICGV 10178 was the best general combiner with positive contribution and significance to SCMR, PY, SHP, KY, TBM and HI and reduced SLA. Crosses ICGV 10178 × ICGV 11369, ICGV 10373 × ICGV 15083, ICGV 98412 × ICGV 15094 and ICGV 10178 × ICGV 98412 were the best specific combiners for enhanced pod yield and drought tolerance. The GCA was found predominant over the SCA effect for the inheritance of PY, KY and TBM. Higher GCA: SCA rations were recorded for PY and KY under both DS and NS conditions, and SCMR, SLA and TBM under DS condition suggesting the predominant role of additive genes conditioning the inheritance of these traits. Therefore, the above new progenies are useful populations for developing improved pure line groundnut varieties with high pod yield and drought tolerance.
Genomic prediction provides an efficient alternative to conventional phenotypic selection for developing improved cultivars with desirable characteristics. New and improved methods to genomic ...prediction are continually being developed that attempt to deal with the integration of data types beyond genomic information. Modern automated weather systems offer the opportunity to capture continuous data on a range of environmental parameters at specific field locations. In principle, this information could characterize training and target environments and enhance predictive ability by incorporating weather characteristics as part of the genotype-by-environment (G×E) interaction component in prediction models. We assessed the usefulness of including weather data variables in genomic prediction models using a naïve environmental kinship model across 30 environments comprising the Genomes to Fields (G2F) initiative in 2014 and 2015. Specifically four different prediction scenarios were evaluated (i) tested genotypes in observed environments; (ii) untested genotypes in observed environments; (iii) tested genotypes in unobserved environments; and (iv) untested genotypes in unobserved environments. A set of 1,481 unique hybrids were evaluated for grain yield. Evaluations were conducted using five different models including main effect of environments; general combining ability (GCA) effects of the maternal and paternal parents modeled using the genomic relationship matrix; specific combining ability (SCA) effects between maternal and paternal parents; interactions between genetic (GCA and SCA) effects and environmental effects; and finally interactions between the genetics effects and environmental covariates. Incorporation of the genotype-by-environment interaction term improved predictive ability across all scenarios. However, predictive ability was not improved through inclusion of naive environmental covariates in G×E models. More research should be conducted to link the observed weather conditions with important physiological aspects in plant development to improve predictive ability through the inclusion of weather data.
The experiment was conducted to develop tomato hybrids by identifying parental lines with estimation of good combining ability effects and their variances through line x tester analysis of 44 ...genotypes including 32 F1 cross combinations using 12 parents after selfing (8 lines and 4 testers). The genotypes were evaluated for the yield and contributing traits. The analysis of variance (ANOVA) showed highly significant difference for all the characters suggesting the presence of genetic variability among the studied materials. The variance values of general combining ability (GCA) were lower than the specific combining ability (SCA) for all the traits except plant height. This indicates that these traits were under the control of non-additive (non-fixable) gene effects and could be exploited by heterosis breeding. The lines L1, L2, L3, L5, and testers T2, and T4 showed a desirable significant negative GCA effect for days to first flowering and days to maturity. The line L5 showed a positive significant GCA effect for most of the traits except fruit per cluster and L4 for plant height, cluster per plant, fruit per cluster, fruit per plant, fruit diameter, and yield per plant. Based on GCA effects across ten traits L4 and L5 were identified as the most promising parental lines for inclusion in hybridization programs. Outstanding crosses based on SCA effects across ten traits were L6XT1, L2XT3, L7XT2, and L4XT4. These crosses could be considered the most promising specific combiner for most traits which can be used to develop elite tomato varieties.
The inappropriate use of cacao clones either as female or male parents in seed gardens have been suggested as some of the reasons for the low yields of cacao hybrid varieties grown in West Africa. ...The concept of reciprocal effects in cacao crosses has not been well studied. To investigate the impact of maternal effect on growth and yield traits, reciprocal differences and combining abilities of recommended cacao parents in Ghana were evaluated. Six clones, comprising four important seed gardens clones used across West Africa and two clones previously used as standards in international breeding projects were crossed in a 6 × 6 complete diallel mating design to produce 30 F1 progenies. These progenies were tested in the field using a random block design with four blocks and elementary plots containing 20 plants. Growth and yield traits including stem cross-sectional area in juvenile stage, jorquette height, bean weight, number of beans per pod and bean yield were monitored over a 6-year period. Mean squares of general combining ability (GCA), specific combining ability (SCA) and reciprocal effects were significant for almost all the traits except jorquette height in SCA. This indicates that additive and non-additive gene effects are important in the inheritance of the traits. The presence of reciprocal differences for all traits suggests the influence of maternal effects in controlling the traits. Manual pollinations for commercial seed production should, therefore, follow established protocol and clones recommended as female and male parents used strictly as recommended. One of the standard clones, AMAZ15/15 had significant positive GCA effect for yield, and consistently produced progenies with high SCA values. It could be added to parental clones currently used in producing cacao varieties in the seed gardens in Ghana and other West African cacao growing countries.
Combining ability estimates were studied for kernel yield, its components and morphological traits in nine maize parents and 36 F1 hybrids generated from cross in half diallel mating design. Analysis ...of variance for combining ability revealed that mean sum of squares due to general combining ability were found significant for all the traits except cob length and cob girth, whereas, the specific combining ability effects were found highly significant for all the characters except cob length, cob girth and anthesis - silking interval. Based on estimates of general combining ability, two parents viz., WNC 40228 (6.17) and WNC 31702 (5.47) were found as good general combiners because they registered significant and positive gca effects. The estimates of sca effects revealed that 13 hybrids were exhibited significant positive sca effects. The top most three hybrids for kernel yield per plant on the basis of specific combining ability effects were Z 485-50 x Z 485-11 (22.77), WNC 40228 x BLD - 105 (20.13) and WNC 40228 x Z 485-11 (17.47). The low ratio (<1.0) of GCA to SCA variance for fourteen traits indicated that non-additive type of gene action was predominant in the expression of yield and component traits.
Background: The success of hybridization programme depends on the combining ability of parental lines.
Methods: Seven soybean genotypes and all their partial diallel crosses in the F2 generation were ...evaluated in a randomized complete block design at two locations in Nigeria, during the 2017-2018 growing season. Result: Analysis of variance showed that both environments and genotypes were significantly different for all measured traits. The genotype TGx 1988-5F was the best general combiner for earliness in flowering and poding, while TGx 1448-2E was the best general combiner for number of pods/plant and seed yield/plant. Crosses having significant and positive specific combining ability effect for number of pods/plant and seed yield/plant were TGx 1485-1D × TGx 1448-2E and TGx 1988-5F × TGx 1989-19F, respectively. Genotypes TGx 1988-5F and TGx 1448-2E exhibiting good general combining ability for earliness and seed yield/plant, are thus, promising for utilization in the future hybridization programme for soybean improvement.
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