Carrot is an important vegetable crop worldwide valued for its fleshy edible roots of varied colours. Owing to its highly cross-pollinated nature and small flower size, cytoplasmic male sterility (CMS) is being utilized for hybrid development. Among different types of male sterility, petaloid CMS is widely used for hybrid carrot breeding globally. This study aimed to develop selection criteria for parents in developing heterotic F1 hybrids using CMS lines. A large number of agro-morphological traits and Simple Sequence Repeats (genomic-SSRs) were used to assess the diversity among parental lines. We developed 60 F1 hybrids by crossing four petaloid CMS lines and 15 testers in line × tester mating design and evaluated them in replicated randomized block design trial for four vegetative and 11 economic traits. The mean squares of all the traits in line × tester interactions were significant. The estimates of genetic components of variance indicated predominance of non-additive gene action except for root maturity, root length and core diameter. The hybrids with highest per se performance also had significant positive specific combining ability effects. The root yield and root weight showed highest heterosis percentage (33%). The best performing heterotic hybrids were DCatH-5392, DCatH-700 and DCatH-9892. Correlation between genetic distance and relative heterosis of economic traits indicated no significant association and thus genetic distance could not be used to predict heterosis. As most of the yield-related traits were controlled by non-additive gene action, heterosis breeding could be potentially used along with combining ability analysis to reduce time in selection of best parents and crosses in tropical carrot.

Cauliflower is an important vegetable crop grown worldwide. Development and characterization of suitable cytoplasmic male sterile (CMS) lines and male fertile inbreds is instrumental in developing heterotic hybrids. A study was undertaken to estimate heterosis and combining ability in snowball cauliflower lines through line × tester analysis involving five Ogura CMS lines and seven male fertile testers. The assessment of F1s along with their parental lines for different horticultural traits revealed a wide range of heterosis. Ogu-13-01 was the best general combiner for leaf length, leaf width and plant height, Ogu-13-85 for number of leaves/plant, Ogu-101 for days to 50% curd initiation, days to 50% curd maturity and net curd weight and Ogu-119 for harvest index. The lines with better general combining ability (GCA) were involved in majority of the heterotic hybrids. The tester Kt-18 was the best general combiner for leaf width, DB-1305 for number of leaves/plant and DB-187 for leaf length, plant height, gross plant weight and days to 50% curd initiation. However, GCA alone was not sufficient to determine and identify the potential parental lines. Hybrids Ogu-101 × DB-1305 and Ogu-119 × Suprimax Late were the best specific combinations for marketable curd weight, marketable curd yield, net curd weight and net curd yield. The hybrid Ogu-119 × Suprimax Late was the best heterotic combination for marketable curd weight, marketable curd yield, net curd weight and net curd yield, followed by Ogu-101 × DB-1305, Ogu-119 × Sel-26 and Ogu-101 × DB-187. Our findings will be instrumental to identify suitable parental lines and developing heterotic F1 hybrids in cauliflower.

Selection of lines from segregating generations and breeding hybrids to exploit heterosis or heterobeltiosis is an effective tool for improving economically important traits in the genus Capsicum. The objective of this study was to identify high potential parents to obtain high-yielding F1 hybrids using a Line × Tester (8 × 2) mating design in the Habanero pepper improvement programme. Ten parents and 16 hybrids were evaluated in order to determine their values of general combining ability, specific combining ability, heterosis, and heterobeltiosis. Parent NKA-11 had the highest values of GCA for different quantitative variables of the fruit, which does it suitable for future improvement works, and tester RNJ-04 showed the highest value of GCA for fruit length. The quantitative variables evaluated confirm a significant genetic variability among the Habanero pepper genotypes studied. The best hybrids were NEK-03xRNJ-04, NBA-06xRNJ-04, AKN-07xRNJ-04, and RKI-10xRNJ-04, which showed their high productive potential with values between 3.13 and 4.92 Kg/Pta, a quality, that would open to them the national market for fresh consumption. Based on the GCA values of the parents and heterosis of the progenies, it is concluded hybridization would be the most appropriate genetic improvement method to increase both yield (YP) and the number of fruits for plant.

Existence of genetic divergence, appropriate characterization of breeding lines for economically important traits and determining parents with favourable alleles is the crux of crop genetic improvement programmes. This study is the first report of unravelling genetics and potential of petaloid-type cytoplasmic male sterile (pt-CMS) lines in carrot. Ten pt-CMS lines were crossed with 10 inbreds in line × tester mating fashion to generate 100 testcross progenies. Nutritional profiling of the 100 testcrosses progenies along with 20 parental types was carried out for two consecutive years for eight important traits to identify superior combiners. The pooled analysis revealed that the carotenoid content in root is under the genetic control of major genes (oligogenic). The pooled analysis revealed less than unity value of σ2A/D and σgca2/σsca2 for majority of the traits depicting preponderance of non-additive gene effects. The pt-CMS lines KT-28A, Kt-62A, KT-80A and KT-95A were identified as good combiners for carotenoids. The cross combination, KT-98A × KS-50 identified as the best heterotic combiner for CUPRAC and FRAP content over the years. Similarly, the combinations, KT-62A × KS-21, KT-80A × New Kuroda and KT-62A × KS-59 were found promising across the years for developing nutritionally rich F1 hybrids. The interaction analysis among the different antioxidant traits and plant pigments unveiled the scope of simultaneous improvement.

Emmer wheat (Triticum turgidum ssp. dicoccum) is one of the most promising gene sources for drought tolerance improvement of durum wheat (Triticum turgidum ssp. durum). Achieving desired results requires a conscious choice of crossing parents based on general and specific combining ability (GCA and SCA) and also understanding the genes action involved in controlling the desired traits. In this study a 12 × 12 full diallel cross was performed using four emmer and eight durum wheats. The 132 hybrid progenies along with their parental lines were field evaluated under water-stressed and non-stressed conditions. Based on the Griffing diallel analysis both GCA and SCA effects were highly significant for all measured traits under both water treatments indicating possibility of improvement for drought tolerance. In this respect, the amount of additive effect was higher than the non-additive suggesting the chance for genetic advancement through selection. Based on Hayman's graphical analyses under the two water conditions it was revealed that several grain yield component traits were under the control of partial dominance. In contrary, grain yield and most morphological traits showed either dominance or over-dominance gene action. Grain yield had a significant positive correlation with the number of kernels per spike, kernel diameter, grain weight per spike and harvest index. These traits also had greater share of additive effects, relatively high narrow-sense heritability and high Baker ratio suggesting effective indirect selection for grain yield. Most durum × emmer hybrids had grain yield and drought tolerance indices better than the parents indicating that Iranian emmer wheats have a great genetic potential for drought tolerance improvement of durum wheat.

Breeding for resistance to biotic stress and higher yield is a continuous process. Thus, the identification of desirable parents with good combining ability and nature of gene action for the target trait is of utmost importance. Hence, in this present investigation, 10 lines and three testers of Okra were crossed in line × tester mating design to generate 30 testcross progenies and their evaluation along with parents and check in a randomized complete block design with three replications. To depict the true picture of genetic variation among the parental genotypes, molecular diversity analysis was also carried out using genomic-simple sequence repeats before crossing to ascertain that sufficient variability is present among the parents. The molecular analysis grouped the parental genotypes into four clusters (I–IV). The analysis of variance revealed that all the treatments were significant for most of the traits. The combining ability analysis suggested Pusa A-4 as the best general combiner for earliness, Pusa Bhindi-5 for high yield, and DOV-92 for fruit length, plant height, yield per plant, and coefficient of infection for Yellow Vein Mosaic Virus Disease resistance. Similarly, the specific combining ability analysis suggested that the cross combinations DOV-92 × Pusa Bhindi-5 followed by DOV-92 × Pusa A-4 and DOV-92 × Pusa Sawani exhibit high economic heterosis for yield per plant as well as for disease resistance. Finally, estimation of the degree of dominance and predictability ratio was also worked out which indicated the prevalence of non-additive gene action for most of the traits pointing towards sufficient scope for heterosis breeding in Okra.

Hybrid breeding relies on selection of genetically unrelated and complementary parents for key traits. The objective of this study was to examine genetic variation and identify unique sorghum genotypes using phenotypic and simple sequence repeat (SSR) markers and to determine their relationships with combining ability and heterosis for grain yield. A total of 32 landraces and four cytoplasmic male sterile (CMS) lines were phenotyped using 25 agro-morphological traits and genotyped with 30 polymorphic SSR markers. The landraces were crossed with four CMS lines using a line × tester mating design. The 128 hybrids, 36 parentals and four check varieties were field-evaluated using a 12 × 14 alpha lattice design with three replications. General combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield were determined. Genetic distance estimates ranged from 0.39 to 0.60 and 0.50 to 0.79, based on phenotypic and SSR markers, respectively. Landraces 72572, 75454, 200654, 239175, 239208, 244735A and 242039B and CMS lines ICSA 743 and ICSA 756 displayed positive and significant GCA effects for grain yield. Based on the SCA effects of yield, lines were classified into three heterotic groups aligned to the different cytoplasmic systems of testers. Lines with high GCA effects rendered hybrids with highly significant SCA effects with high mid-parent heterosis (MPH) for grain yield. Both marker systems were effective in demarcating sorghum genotypes that provided desirable cross-combinations with high combining ability effects and MPH for grain yield. The selected genotypes are recommended as potential parents for sorghum hybrid breeding in moisture stress environments.

Combining ability analysis for three stem borer resistance parameters, i.e. “dead hearts”, leaf injury and stem tunnelling, revealed that both additive and non-additive types of gene effects were involved in the inheritance of these attributes. The specific combining ability (sca)/general combining ability (gca) variance ratios further indicated predominance of additive gene effects for stem tunnelling and non-additive effects for “dead hearts” and leaf injury. The genotypes, IS 2123 and IS 5469 are good general combiners for all the three parameters. Among F1 hybrids, IS 1054 × IS 5469 and IS 18551 × IS 2123 expressed good sca for all the parameters of stem borer resistance. The use of IS 2123 and IS 5469 parental genotypes in the future breeding programmes is suggested.

Inheritance of resistance to sorghum midge, Contarinia sorghicola Coq. was studied on a set of 21 diallel crosses involving four midge-resistant and three susceptible sorghum, Sorghum bicolor (L.) Moench cultivars under natural midge infestation at Dharwad during the late rainy season (August to November) 1983. Both additive and nonadditive genetic variances were important for midge resistance. The parents, DJ 6514 and TAM 2566, proved as better general combiners. Mean performance of the parents and their general combining ability (GCA) effects were strongly correlated. Crosses with positive specific combining ability (SCA) effects in both F1 and F2 generations had at least one parent with high GCA effects and better per se midge resistance. Midge-resistant parents, DJ 6514 and TAM 2566, with high per se resistance and GCA effects should be utilized in breeding for midge resistance.

Genetic analysis of sorghum resistance to stem-borers was performed in a 6 × 6 diallel cross. The results indicated that resistance to stem-borers is polygenically inherited. F1 hybrids did not differ significantly from mid-parental values suggesting intermediate inheritance. However, resistance was partially dominant to susceptibility. Combining ability analysis showed that resistance to primary damage, i.e. % ‘dead heart’ was governed by both additive and non-additive type of gene actions while secondary damage, i.e. % stem tunnelling was governed predominantly by additive gene action. It was noted that the inheritance patterns of primary and secondary damage were different. Tunnel length showed positive correlation with the number of larvae per plant and negative association with plant height, but had no correlation with grain yield per plant. On the basis of larvae recovered from the tunnelled plants, Chilo partellus was found to be the predominant stem-borer species followed by Sesamia calamistis, Eldana saccharina and Busseola fusca. Significance of genetic studies of host plant resistance in deciding breeding strategies for insect resistance has been discussed.