Showing papers on "Diallel cross published in 2021"

Linear models for diallel crosses: a review with R functions

Abstract: A new R-software procedure for fixed/random Diallel models was developed. We eased the diallel schemes approach by considering them as specific cases with different parameterisations of a general linear model. Diallel experiments are based on a set of possible crosses between some homozygous (inbred) lines. For these experiments, six main diallel models are available in literature, to quantify genetic effects, such as general combining ability (GCA), specific combining ability (SCA), reciprocal (maternal) effects and heterosis. Those models tend to be presented as separate entities, to be fitted by using specialised software. In this manuscript, we reinforce the idea that diallel models should be better regarded as specific cases (different parameterisations) of a general linear model and might be fitted with general purpose software facilities, as used for all other types of linear models. We start from the estimation of fixed genetical effects within the R environment and try to bridge the gap between diallel models, linear models and ordinary least squares estimation (OLS). First, we review the main diallel models in literature. Second, we build a set of tools to enable geneticists, plant/animal breeders and students to fit diallel models by using the most widely known R functions for OLS fitting, i.e. the ‘lm()’ function and related methods. Here, we give three examples to show how diallel models can be built by using the typical process of GLMs and fitted, inspected and processed as all other types of linear models in R. Finally, we give a fourth example to show how our tools can be also used to fit random/mixed effect diallel models in the Bayesian framework.

Genetic analysis of freezing tolerance in camelina [Camelina sativa (L.) Crantz] by diallel cross of winter and spring biotypes.

Abstract: Camelina biotypes had different responses to freezing stress, which was mainly inherited by additive gene effects and can be reliably used in breeding programs and for a better understanding of freezing tolerance mechanisms in camelina plants. Camelina [Camelina sativa (L.) Crantz] is a frost-tolerant oilseed plant that is cultivated as an autumn crop in semi-arid regions. However, camelina establishment in these areas is limited by low temperatures in winter that results in decreased seed yield. In the present study, genetic basis of freezing tolerance (FT) in spring and winter biotypes of camelina was analyzed at seedling stage using a diallel cross experiment. The parents consisted of two winter doubled haploid (DH) lines with high (DH34 and DH31), two spring lines with medium (DH19 and DH26), and two spring lines with low FT (DH08 and DH91). For this purpose, the parents along with F1 entries were subjected to freezing stress and survival percentage, electrolyte leakage, and lethal temperature for 50% mortality (LT50) of the lines were measured. Results showed that although both additive and non-additive effects of the genes determine the FT, further analyses indicated that it was mainly controlled by the additive effects. Therefore, selection-based methods may be more efficient for improving FT in camelina genotypes. The results of specific combining ability (SCA) and heterosis analysis among various DH lines suggested that more tolerant cultivars of camelina could be developed by targeted crossings. When a tolerant winter line and a susceptible spring line were crossed, their progenies showed a higher FT compared with the progenies of a cross between two susceptible spring lines indicating FT is controlled by additive effects of the genes in camelina plants. These findings provided new insight into the genetic basis of freezing-related traits in camelina and could be used for more sophisticated breeding programs.

Tomato fruit quality traits and metabolite content are affected by reciprocal crosses and heterosis.

Abstract: Heterosis occurs when the F1s outperform their parental lines for a trait. Reciprocal hybrids are obtained by changing the cross direction of parental genotypes. Both biological phenomena could affect the external and internal attributes of fleshy fruits. This work aimed to detect reciprocal effects and heterosis in tomato (Solanum lycopersicum) fruit quality traits and metabolite content. Twelve agronomic traits and 28 metabolites identified and estimated by 1H-NMR were evaluated in five cultivars grown in two environments. Given that the genotype component was more important than the phenotype, the traits were evaluated following a full diallel mating design among those cultivars, in a greenhouse. Hybrids showed a higher phenotypic diversity than parental lines. Interestingly, the metabolites, mainly amino acids, displayed more reciprocal effects and heterosis. Agronomic traits were more influenced by general combining ability (GCA) and metabolites by specific combining ability (SCA). Furthermore, the genetic distance between parental lines was not causally related to the occurrence of reciprocal effects or heterosis. Hybrids with heterosis and a high content of metabolites linked to tomato flavour and nutritious components were obtained. Our results highlight the impact of selecting a cultivar as male or female in a cross to enhance the variability of fruit attributes through hybrids as well as the possibility to exploit heterosis for fruit composition.

Enhancing Drought Tolerance and Striga hermonthica Resistance in Maize Using Newly Derived Inbred Lines from the Wild Maize Relative, Zea diploperennis

Abstract: Recurrent drought and Striga hermonthica (Del.) Benth parasitism constrains maize production in sub-Saharan Africa (SSA). Transfer of resistance genes from wild relatives can improve resistance to drought and Striga in tropical maize. The objectives of this study were to (i) determine the combining ability of 12 extra-early yellow maize inbreds derived from Zea diploperennis and tropical maize germplasm; (ii) classify the inbreds into heterotic groups using heterotic grouping based on the general combining ability (GCA) of multiple traits (HGCAMT) method; (iii) examine hybrid performance under contrasting environments; and (iv) examine the stability of hybrid combinations involving the inbreds. Sixty-six diallel crosses involving the inbreds plus four checks were evaluated for two years under drought, Striga-infested and rainfed environments in Nigeria. Significant differences (p < 0.05) were observed for the effects of genotype, environment, genotype × environment, GCA and specific combining ability (SCA) on grain yield and other measured traits. Inbred lines such as TZdEEI 7 × TZEEI 63 derived from Z. diploperennis and tropical germplasm exceeded the checks by a range of 28 to 41%. Across environments, the hybrid TZdEEI 1 × TZdEEI 7, which was derived from Z. diploperennis, was the highest-yielding with a grain yield of 4302 kg ha−1. The results revealed the predominance of GCA over SCA effects for most measured traits, suggesting that additive gene action governed the inheritance of Striga resistance and drought tolerance related traits in the inbreds. The 12 inbreds were classified into three heterotic groups, while TZEEI 79 and TZdEEI 7 were identified as inbred testers and TZdEEI 7 × TZEEI 12 as a single-cross tester across environments. Hybrid TZdEEI 9 × TZEEI 79 was the highest-yielding and most stable. Other promising hybrids were TZdEEI 7 × TZEEI 79, TZdEEI 1 × TZdEEI 7 and TZdEEI 12 × TZEEI 95. These hybrids should be extensively tested on-farm for potential commercialization in SSA. Overall, our results highlighted the importance of harnessing beneficial alleles from wild relatives of maize for improvement of resistance to Striga and tolerance to drought in adapted maize germplasm.

Identification of seed protein and oil related QTL in 944 RILs from a diallel of early-maturing European soybean

Abstract: Soybean [Glycine max (L.) Merr.] is a global protein source and is currently expanding in Central and Northern Europe. Protein and oil content are two important quality traits that have been studied in different germplasm, however, their genetic architecture in early-maturing European soybean has not been investigated yet. In this study, we therefore performed QTL mapping for both traits using 944 recombinant inbred lines derived from eight families from a half-diallel crossing design. We identified five QTL for each trait, with the QTL on chromosomes 8, 15, and 20 being identified for both protein content and oil content. The known major QTL on chromosome 20 was detected in four families whereas the other QTL were only found in single families. Further analyses revealed the QTL to have pleiotropic but inverse effects on both traits. The effect of the major QTL was comparable between families, illustrating that it is largely independent from the genetic background. Collectively, our results illustrate the quantitative nature of protein and oil content in early European soybean. Marker-assisted selection for the QTL is possible, but the inverse effect on protein and oil content should be kept in mind.

Emmer wheat as a source for trait improvement in durum wheat: a study of general and specific combining ability

Abstract: Emmer wheat (Triticum. turgidum ssp. dicoccum) as an ancestor of bread and durum wheats, can be a potential resource to restore genetic diversity in modern durum wheats. In order to estimate the combining ability, the type of gene action, heritability, and other genetic parameters of agronomic traits, a full diallel cross (12 × 12) was made between eight durum cultivars and four emmer wheat accessions. The F1 hybrids (132 combinations) and their parents were evaluated for important traits that account for productivity during two cropping seasons. Considerable genetic diversity among the parents and the hybrids was evident, with most of the hybrids showing higher grain yields than their respective durum parent. High general combining ability for all of the measured traits, and higher Baker ratios for most of the traits indicated that additive gene action was involved. Based on the Griffing diallel method, the specific combining ability was significant for most of the measured traits. The Hayman analysis revealed the presence of partial dominance gene action for traits such as the number of tillers per plant (NT), grain weight per spike (GWS), harvest index (HI), days to heading (DH), and number of kernels per spike (NKS). However, plant height (PH), days to maturity (DM), peduncle length (PL), and grain yield (GY) were under the influence of the over-dominance gene action. The narrow-sense heritability for GWS, NKS, kernel diameter (KD), and HI was relatively high and these four were positively correlated with grain yield. Therefore, selection for these four traits in early generations may indirectly improve yield. The results indicate that Iranian emmer wheats are a good source of wild type alleles and valuable QTLs to improve the elite durum wheat cultivars.

Genetic behavior for seed yield and yield components in sesame (Sesamum indicum L.) under normal irrigation and water stress conditions

Abstract: Six divergent genotypes of sesame (Sesamum indicum L.) were crossed using a half diallel excluding reciprocal crosses, to estimate heterosis, combining ability and nature of gene action for studied traits under two irrigation regimes. The two irrigation regimes were normal irrigation conditions with amount of applied water 5952.38 m3/ha and water stress conditions with amount of applied water 2976.19 m3/ha at Etay-El-Baroud Agricultural Research Station, Behaira governorate, Agricultural Research Center, Egypt during 2019 summer season. A randomized complete block design with three replications was used for each irrigation regimes. The variation of genotypes and their components from parents, crosses and parents versus crosses were highly significant for all studied traits under both irrigation regimes and their interactions with irrigation. Variation attributable to general and specific combining ability was highly significant for seed yield and yield components under both irrigation regimes. The parents L92 and L110 were the best combiners for seed weight per plant and most of its components under both irrigation regimes. The best F1 cross combination was L92 × L110 in specific combining ability and heterotic effects over mid- and better-parents under both irrigation regimes for seed weight per plant and most of its attributes. The preponderance of additive gene action in the inheritance of most studied traits was observed, that further confirmed by its significance and the value of average degree of dominance exceeding the unity. Narrow-sense heritability varied from 0.19 for number of branches per plant to 0.47 for 1000 seed weight under normal irrigation, whereas, under water stress conditions, it ranged from 0.14 for number of branches per plant to 0.42 for fruiting zone length. Parents L95 and L93 under normal irrigation and L93 and L110 under water stress conditions carried mostly genes with dominant effects for seed weight per plant, in contrary, L92 and L110 under normal irrigation and L92 and L12 under water stress conditions carried mostly recessive alleles for seed weight per plant. Hence, the results will be used to develop a sesame breeding scheme at Etay-El-Baroud Agricultural Research Station.

General and specific combining abilities in a lulo diallel cross (Solanum quitoense Lam.)

Abstract: Lulo (Solanum quitoense) is a promising agro-industry fruit tree, not only because of its nutritional value, taste, and appearance but also because it provides an alternative production system in mild and moderately cold climate zones. Lulo crop yield and production in the Department of Nariño (Colombia) has decreased in recent years when compared to other producing regions in Colombia. Therefore, the objective of this study was to estimate the effects of the general combining ability (GCA) and the specific combining ability (SCA) in a diallel cross of 10 promising parents in four growing regions of the Department of Nariño for use in breeding programs. A total of 45 hybrid combinations were obtained and assessed with Griffing method 4. The following variables were assessed: days to flowering onset (DFO), number of clusters per branch (NCB), fruit weight (FW), polar axis (PA) of the fruit, and yield (Y). The analysis of variance showed statistical differences for most variables in response to single-cross hybrid effects and locations, except for NCB and Y. Moreover, significant differences were found for the interactions between the GCA and SCA and the hybrids and locations, respectively, meaning that environment must be considered when selecting parents with specific adaptability. The effects of the GCA and SCA promoted higher positive values for the FW and Y in parents 4, 6, and 8 and their combinations. Therefore, these parental genotypes are promising for lulo genetic improvement programs since their additive effects and genetic dominance favor fruit weight and yield. Additional key words: Andean fruit trees; genetic improvement; hybrids; parental plants; yield. 1 Universidad de Nariño, Faculty of Agriculture Sciences, Grupo de Investigación en Producción de Frutales Andinos (GPFA). San Juan de Pasto (Colombia). ORCID Duarte-Alvarado D.E.: 0000-0002-8896-3594; ORCID Lagos-Burbano T.C.: 0000-0001-9222-4674; ORCID Lagos-Santander L.K.: 0000-0001-9932-0909; ORCID Benavides-Cardona C.A.: 0000-0002-9144-6168 2 Corresponding author. deduartea@unal.edu.co Doi: https://doi.org/10.17584/rcch.2021v15i1.11976 REVISTA COLOMBIANA DE CIENCIAS HORTÍCOLAS Vol. 15 No. 1, e11976, January-April 2021 e-ISSN: 2422-3719 · ISSN-L: 2011-2173 The lulo (Solanum quitoense Lam.) is a fruit tree species in the Solanaceae family, and is a promising crop for agro-industry because of its potent organoleptic characteristics and physical traits (Cardona et al., 2016; Criollo-Escobar et al., 2020). It is an economically important crop in Colombia, mainly in the Andean region (Almanza-Merchán et al., 2016; Sánchez-Reinoso et al., 2019). In Colombia, this crop is grown between 1,300 and 2,200 m a.s.l. mainly using two species: S. quitoense var. quitoense (sweet and without thorns) and S. quitoense var. septentrionale (acid and with thorns) (Ochoa-Varagas et al., 2016). In 2018, there were approximately 8,800 ha of this crop established in 21 departments, particularly Huila and Valle del Cauca, which had the larger crop areas, covering 2,005 and 1,029 ha, respectively. The domestic lulo production increased from 8.87 to 9.86 t ha-1 in the last 10 years (Agronet, 2020). In 2018, the Department of Nariño had 609 ha of lulo crops according to Agronet (2020), mainly distributed across the northern and southern municipalities. This crop area produced an average yield of 5.64 t ha-1; accordingly, Nariño ranked fourth for the domestic supply and had a yield deficit (i.e., lower yield than the national average). Moreover, departments such as Huila (7.15 t ha-1) and Valle del Cauca (12.2 t ha-1) had larger crop areas and production. One of the main factors limiting lulo cultivation in Colombia is the insufficient supply of improved cultivars, mainly the result of the scarcity of genetic improvement plans or programs for this species. There are no mediumand long-term solutions, making it necessary to generate strategies to increase productivity. One of these strategies is the evaluation of the germplasm with different approaches (LagosSantander et al., 2019). In these evaluations, a population analysis can be used to study the genetic control of quantitative traits, evaluating both general and specific combinatorial skills in breeding programs to obtain desired agronomic and genetic traits, depending on the research context (Manjarrez et al., 2014). In Colombia, studies on lulo have focused on the germplasm that has been collected and conserved, especially in the departments of the Andean region. This research has allowed advancements in RESUMEN El lulo (Solanum quitoense) es un árbol frutal prometedor para la agroindustria, no sólo por su valor nutritivo, su sabor y su aspecto, sino también porque constituye un sistema de producción alternativo en zonas de clima templado y moderadamente frío. El rendimiento de los cultivos y la producción de lulo en el Departamento de Nariño (Colombia) han disminuido en los últimos años en comparación con otras regiones productoras del país. Por lo tanto, el objetivo de este estudio fue estimar los efectos de la habilidad combinatoria general (HCG) y la habilidad combinatoria especifica (HCE) en un cruzamiento dialelico de 10 progenitores promisorios en cuatro regiones del Departamento de Nariño, que pueden considerarse en los programas de mejoramiento. Se obtuvieron un total de 45 combinaciones híbridas obtenidas con el método 4 de Griffing. Se evaluaron las siguientes variables: días para el inicio de la floración (DIF), número de racimos por rama (NRR), peso del fruto (PF), eje polar (EP) del fruto y rendimiento (RTO). El análisis de la varianza mostró diferencias estadísticas para la mayoría de las variables en respuesta a los efectos de los híbridos y a las localidades, excepto para NRR y RTO. Además, se encontraron diferencias significativas para las interacciones del HCG y HCE con los híbridos y las localidades, respectivamente, demostrando que debe considerarse el medio ambiente para seleccionar los progenitores con una adaptabilidad específica. Los efectos del HCG y HCE presentan valores positivos altos para PF y RTO en los parentales 4, 6 y 8 y en sus combinaciones. Por lo tanto, estos parentales son promisorios para los programas de mejoramiento genético del lulo, ya que sus efectos aditivos y de dominancia favorecen el peso y el rendimiento del fruto. Palabras clave adicionales: frutales andinos; mejoramiento genético; híbridos; parentales; rendimiento. Received: 28-10-2020 Accepted: 25-11-2020 Published: 13-01-202

Combining ability and genetic divergence among tropical maize inbred lines using SSR markers

Abstract: . Our objectives were to evaluate general and specific combining ability (SCA) and genetic divergence among tropical maize inbred lines using single sequence repeat (SSR) markers. Thirteen inbred lines were crossed based on a complete diallel scheme. Hybrids and three checks were evaluated in a lattice experimental design. Silk and anthesis flowering, average plant height, average ear height, white spot (Pantoea ananatis) and gray leaf spot (Cercospora zeae-maydis) severity, and grain yield were evaluated. Significant differences (p < 0.05) for general and specific combining abilities were observed for all traits. Based on additive effects, inbred lines 1 (Flash) and 12 (SG 6015) were selected to reduce the flowering period and plant and ear height. Inbred lines 2 (CD 303) and 3 (AG 8080) were selected to reduce disease severity. For the simultaneous increase in grain yield and reduced severity of diseases, line 11 (AG 9090) as a parent or tester in topcross schemes is recommended. According to non-additive effects, crosses 2 (CD 303) × 13 (DKB 747) and 11 (AG 9090) × 12 (SG 6015) were selected for grain yield and future breeding programs. Six groups were identified using SSR markers; a major group contained six inbred lines. Because of the minor relationship between genetic divergence and SCA effects on grain yield limits, the use of the groups for future divergent crosses is recommended.

Half Diallel Analysis for Biochemical and Morphological Traits in Cultivated Eggplants (Solanum melongena L.)

Abstract: Eleven morphologically diverse cultivated eggplant accessions were used for hybridization following half diallel mating design to obtain 55 hybrids. Evaluation of hybrids along with the parents was conducted over two locations followed by randomised complete block design with three replications to study gene action and combining ability of 15 morphological and biochemical traits. The analysis of variance indicated highly significant differences among the environments and interaction of genotype and environment, except for fruit length to width ratio. Additive gene effects were significant for the inheritance of these traits and expression of these additive genes were greatly affected by environments. The general combining ability (GCA) was greater than their respective specific combining ability (SCA) for all traits except for fruit yield per plant. High values of GCA and SCA effects for characters of interest were dispersed among different genotypes. From this study it was observed that the best parental line was BT15 based on days to first flowering, total number of fruits per plant, total soluble solids and total phenol content. Besides, the parent BM5 showed good general combining ability effects for fruit yield per plant, fruit length and fruit length to width ratio and the parent BB1 performed good general combining ability for fruit diameter, fruit girth and fruit weight. Besides, other parents showed the best performance for only one trait. On the other hand, the hybrid BT6 × BT15 was reported bearing early flowering with high total phenol content and the hybrid BM9 × BB26 has high fruit yield with high soluble solids. Besides, the hybrid BM9 × BB1 has a high fruit diameter and fruit weight. All other hybrids except for these three (BT6 × BT15, BM9 × BB26 and BM9 × BB1) were shown the best performance for only one trait. Hence, based on the desired trait, the hybrid can be selected for future use after large scale evaluation.

Combining Ability and Heterosis of Algerian Saharan Maize Populations (Zea mays L.) for Tolerance to No-Nitrogen Fertilization and Drought

Abstract: Drought and low nitrogen are major stresses for maize (Zea mays L.), and maize populations from the Sahara Desert are potential sources of stress tolerance. The objectives were to assess the tolerance and varietal and heterosis effects of Algerian populations under no-nitrogen fertilization and water stress. A diallel among six Algerian maize population was evaluated under drought (300 mm irrigation) vs. control (600 mm) and no-nitrogen fertilization vs. 120 kh ha−1 N fertilization. Genotypes showed significant differences and genetic effects for water- and nitrogen-stress tolerance. We propose a reciprocal recurrent selection to take advantage of additive and non-additive effects, using AOR and IGS, since they showed good performance in optimum and stress conditions, for improving yield heterosis for AOR × IGS. Negative effects are not expected on plant height, anthesis–silking interval or early vigor. These populations and BAH could be sources of inbred lines tolerant to drought and no-nitrogen fertilization. There was no relationship between origin and genetic group and stress tolerance per se or as parents of tolerant crosses. These populations and crosses could be used as base material among Algerian populations, for breeding programs focusing on tolerance to water or nitrogen stress.

Inheritance of some flag leaf and yield characteristics by half-diallel analysis in rice crops (Oryza Sativa L.)

Abstract: This study was conducted during 2018 and 2019 at the Rice Research and Training Centre farm, Sakha, Kafr el Sheikh, Egypt. Six genotypes of rice, Sakha 101, Giza 178, Irat 170, Wab-56-104, IR65500-127 and IR69853 were half-diallel crossed to estimate the combining ability effect as well as sink and yield potential in rice. Sink capacity (number of spikelets/panicle and 1000-grain weight), source leaf (flag leaf length, flag leaf width and flag leaf area), source-sink association (number of spikelets/panicle to flag leaf area ratio) and traits of yield components (filled grains number/panicle and panicle number) plant and grain yield/plant) were analysed. The results indicated that both general and specific combining ability were highly significant for all the studied characteristics. IR65500-127, Giza 178, and Sakha 101 were identified as good parents, so these parents were suggested for a further recombinant breeding programme. The cross of 3 × 5 was found to be superior for flag leaf width and grain yield, while the cross of 1 × 4 was found to be superior for flag leaf length, flag leaf length/width ratio, chlorophyll content and number of panicles/plant. Advancing these crosses and effected selections in segregating generation would be helpful to develop high yielding varieties. The genetic parameter showed a dominant deviation in one direction was controlled for all characters except flag leaf length. The analysis of the regression line showed that the over-dominance played an important role in the inheritance of gene action for grain yield/plant.

Parental genetic distance and combining ability analyses in relation to heterosis in various rice origins

Abstract: Information on parental genetic distance and combining ability is a fundamental prerequisite for hybrid rice breeding. Based on a study of genetic diversity using molecular markers, 12 parents representing various rice origins were selected to make diallel crosses, and hybrids were evaluated in tropical environments. Yield, yield heterosis and combining ability were investigated with the main objectives of (1) evaluating the genetic relationship between each type of rice by DNA marker, (2) estimating the heterosis and combining ability for yield of F1 hybrids from the crosses between indica and other types of rice, and (3) identifying hybrid parents for future hybrid rice breeding. Significant differences in yield, yield heterosis and combining ability were detected among parents and among hybrids. Results revealed that indica showed general combining ability higher than other type. Based on genetic distance identified, these rice varieties were classified into two distinct groups and seven subgroups. The varieties placed into the same cluster group were found to from the same origin. Results from the yield evaluation of hybrids and from clustering of genetic distance of the parents indicated that hybrids derived from crosses between parents with medium genetic distance (0.42) gave higher yield heterosis than those derived from crosses with extreme genetic distance (0.07 and 0.83). Heterotic performance and efficiency of breeding heterotic hybrid could be enhanced using selected parents within identified marker-based heterotic groups. This information is useful future for hybrid rice breeding.

Diallel analysis of yield and its important components in wheat (Triticum aestivum L)

Abstract: This study was carried out in Andro Research Farm, CAU, Imphal to study diallel analysis of yield and its important components in 10 genotype of wheat during two consecutive rabi season 2017-2019. All the 10 genotype and their 45 F1’s cross combination exhibited significant difference in characters under study Combining ability analysis showed that both gca and sca variances value were highly significant for most of traits studied in F1 progenies which suggest importance of both additive as well as non-additive genetic components for the expression of characters under study. VL 3017 was found good general combiner for the characters like fifty percent flowering, days to eighty percent maturity, plant height, total number of tillers per hill, total number of spikelets per spike, spike length, total number of filled grains per spike and grain yield per plant. Among all 45 crosses, cross combination VL 3018 x HS 490 and VL 892 x UP 3017 were good specific combiners for the grain yield per plant character in F1 generation.

Heterotic grouping of tropical maize inbred lines and their hybrid performance under stem borer infestation and low soil nitrogen condition in west and central Africa

Abstract: Low soil nitrogen (low-N) and stem borer attack are two of the major stresses limiting maize production in West and Central Africa (WCA). Thus, there is need to intensify efforts aimed at identifying inbred lines with resistance and tolerance to these stresses for hybrid development. The objectives of the study were to determine the combining ability of maize inbred lines, classify them into heterotic groups using both conventional and marker-based approaches, compare the efficiency of the different grouping methods and evaluate the performance of the hybrids generated from the inbred lines under contrasting environments. Ten white maize inbred lines with varying levels of resistance to stem borers were selected and crossed in a diallel in 2015. The resulting 45 hybrids were evaluated together with five checks in 10 environments under low-N, artificial stem borer infestation and non-stress conditions in Nigeria. General combining ability (GCA) and specific combining ability (SCA) were highly significant (p ≤ 0.01) for most of the traits studied but GCA was predominant over SCA under each and across research conditions. Inbred line 2 combined significant positive GCA for grain yield with significant negative GCA for traits of resistance to stem borers and tolerance to low-N. Each of the grouping methods classified the inbred lines into 3 heterotic groups but SCA and heterotic groups’ specific and general combining ability had the joint highest breeding efficiency. Hybrids 1 × 4, 2 × 3, 1 × 6 and 2 × 5 were identified to be high yielding and stable across environments and can serve as candidates for further on-farm evaluations and eventual release in WCA.

Study of genetic variability in relation to yield and yield components in forage sorghum (Sorghum bicolor L. Moench)

Abstract: The present investigation was carried out the genetic analysis of breeding material through components of variance, nature and magnitude of gene effects, genetic variability, heritability, genetic advance, correlation coefficients, general and specific combining ability effects and heterosis among yield and it components in parents and F1’s hybrids. Ten diverse parents i.e., UP Chari-1, HC-308, UP Chari-2, HC-171, Pant Chari-8, CSV-17, Pant Chari-6, CSV-84, Pant Chari-5 and Rajasthan Chari-1, germplasm selected from SVPUA&T, Meerut, U.P. Ten parents diallel set excluding reciprocals was made during the season of kharif 2018 by raising the crop at Crop Research Centre of Sardar Vallabhbhai Patel University of Agriculture & Technology, Meerut. All the 45 crosses and their ten parents were grown during kharif season 2019. All the 45 F1’s hybrids along with ten parents were sown in randomized block design with three replications. Observations were recorded on days to 50% flowering, plant height, leaf breadth, leaf length, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids and green fodder yield. Analysis of variance for parents and crosses showed highly differed significantly for all the characters. Parents vs crosses exhibited highly significant for the attributes namely, days to 50% flowering, plant height, leaf breadth, leaf length, leaf area and green fodder yield, which indicated that wide genotypic differences among the parental lines and F1’s hybrids. High heritability coupled with high genetic advance as percent of mean was observed for the traits viz., plant height, and leaves per plant, leaf area, stem girth, leaf stem ratio and green fodder yield, suggesting that the genes governing these characters may have additive effect.

Diallel Analysis of Eight Yellow Maize Inbred Lines for Earliness and Grain Yield

Abstract: Combining ability for grain yield and other traits were evaluated in a half diallel fashion in maize. Eight yellow maize inbred lines were crossed in half diallel fashion excluding the reciprocals during the summer season of 2018 at Gemmeiza station, the resulting 28F1 were evaluated along with check SC168 at two locations (Gemmeiza and Sids) in 2019 summer season. A randomized complete block design (RCBD) with four replications was used. Mean squares of GCA and SCA were highly significant for all the studied traits at combined data, except SCA for ear diameter. The non-additive gene effects were most responsible for controlling the inheritance of days to 50% silking, plant height, ear length and grain yield. While the additive gene effects had the important role in the inheritance of ear height and ear diameter. The parents; P6 and P7 were significant for general combiner for yield and p 4 for earliness. The crosses P3 xP7, P5 x P8 andP6 x P7 had desirable SCA effects for earliness. Meanwhile, the crosses P2 xP8, P3 x P6, P4 x P5 and P5 x p 7 showed high SCA effect for grain yield. The single crosses; P2 xP7, P2 x P8,P3 x P6, P5 x P7, P6 xP7 andP7 x P8 had desirable mean values for earliness and grain yield.

Development of a New Synthetic Korean Native Chicken Breed using the Diallel Cross-Mating Test

Abstract: We conducted a 4 × 4 diallel cross-mating test using 934 chickens from four grandparent stock lines to develop a new synthetic breed of Korean native chicken. The mean values, combining ability, and reciprocal effects on survival rate, body weight, and hen-day egg production were analyzed. In phenotypes, most chickens have yellowish-brown, reddish-brown and mixed color feathers. The average survival rate was 86.8±12.3%, with the highest in YH combination. Specific combining ability (SCA) had a greater effect on survival rate than general combining ability (GCA), and the SCA of HY combination was the highest. The 16 cross-combinations were distinctly divided into three weight groups according to their genetic characteristics. At 12 weeks of age, GCA showed a greater effect on weight than SCA, and the SCA of FH combination was the highest. The age at first egg laying was 157 days, and the crosses reached sexual maturity faster than the pure lines. The egg production rate was highest in SY at 79.5±2.1%. The GCA and SCA for hen-day egg production were similar, and the SCA was highest in the HS and FY combinations. The reciprocal effect showed that the offspring’s egg production rate was high when S and Y were maternal parents in almost all combinations. In conclusion, FH and HF combinations, which have excellent growth performance, are the most desirable paternal parent stock strains, and FY, FS, HY, and SY combinations, which have excellent laying performance with moderate weight, are the preferred maternal strains. (

Genetic dissection of physiological traits over trait based breeding in bread wheat conferring terminal heat tolerance

Abstract: Breeding of heat-tolerant cultivars requires knowledge of the genetic behavior of morpho-physiological traits. Gene action was investigated using wide phenotypic segregation ranging across six generations (P1, P2, F1, BC1, BC2 and F2) of four different tolerant × sensitive crosses for grain filling duration, GFD (40.14–46.20); canopy temperature depression, CTD (2.42–5.97); normalized difference vegetation index, NDVI (0.35–0.61); membrane thermostability index, MSI (31.40–40.93); no. of grains/spike, GN/SP (26.29–54.80); thousand-grain weight, TGW (31.70–44.45); and grain yield/plant, GY (15.37–24.89) under terminal heat stress. Scaling results indicated an absence of epistasis for MSI and TGW in cross PBN51 × HUW510. The prominence of Dominance × dominance interaction over additive × additive and additive × dominance interactions along with significant dominant gene effect [h] for all traits except MSI was observed. For MSI, similar signs of [d] and [i] along with significant [j] showed the possibility of exploitation of additive gene effect. CTD, NDVI and GN/SP were controlled by duplicated epistasis, whereas both complementary and duplicate epistasis was found for GFD. Digenic interactions with prominent duplicate epistasis indicate that biparental mating or diallel selective mating might be efficiently utilized for their improvement. The present investigation indicated a preponderance of non-additive gene action for studied traits, thus, implying toward delaying of selection to the later generations to exploit transgressive segregants. Any conventional breeding strategy would be followed for generating the cultivars with low CTD, reduced cell membrane injury, with higher NDVI, TGW, GFD, no. of grains/spike and grain yield/plant.

Combining Ability for Grain Yield and Some Agronomic Traits in Diallel Crosses of Bread Wheat under Nitrogen Stressed Conditions

Abstract: Six bread wheat genotypes and their 15 F1 crosses were evaluated under two nitrogen fertilization levels (40 and 80 kg N/fed) to estimate combining ability for days to heading, plant height, spike length, number of spikes/plant, kernels number/spike, weight of 100-kernels and grain yield/plant during 2018/19 season. Results revealed that significant nitrogen levels (N) mean squares were detected for all studied characters. Mean squares due to genotypes (G), parents and crosses for the studied characters were significant at both nitrogen levels and their combined analyses. Also, G x N interaction was highly significant for the studied characters. The general and specific combining ability variances were found to be significant for all studied characters at both-N-levels and their combined analyses. GCA/SCA ratios were less than unity for all studied characters at both N-levels and their combined data. The behavior of gene action varied from nitrogen level to another where the interactions of GCA and SCA with nitrogen levels were significant for most studied characters. Sakha 93 was identified as the most useful source for increasing favorable alleles for grain yield/plant, kernels number/spike and weight of 100-kernels under N-stress conditions, while Giza 168 was the best combiner for earliness at the two N levels. Cross combinations; Sakha 93 x Sids 12 and Sakha 93 x Misr 1 gave the best SCA effects for grain yield/plant under N-stress conditions. Significant positive correlations were detected between means of parents and F1 crosses with their GCA and SCA effects for most studied characters under the two nitrogen levels, respectively

Diallel Analysis on Breast and Thigh Muscle Traits in the Cross of Three South African Indigenous Chicken Genotypes

Abstract: The present study aimed to estimate carcass characteristics of pure and crossbred chickens produced from three parental populations. A 3 × 3 complete diallel mating system involving three indigenous breeds, namely Potchefstroom Koekoek (P), Venda (V), and Ovambo (O), was used to produce three purebred (P × P, V × V, O × O), three crossbreds (P × O, P × V, O × V) and three reciprocals (O × P, V × P, V × O). The nine genetic groups were reared from hatch to 10 weeks of age in an open house with deep litter. At 10 weeks of age, six chickens per genetic group were randomly selected for slaughter. After slaughtering the breast and thigh muscles samples for analysis of the carcass characteristics (Meat colour, meat pH, and Shear force). The results showed that the Potchefstroom Koekoek breed had higher values in all colour indicators, L* (lightness), a* (redness), and b* (yellowness), compared to the other chicken breeds. The Potchefstroom Koekoek and P × O breed had higher pH values ranging from 5.66 to 6 at two hours post-slaughter and from 5.54 to 6.38 at 24 hours post-slaughter. The pH declines in all the nine genetic groups after two to 24 hours, with the exception of the crossbred P × O, which increased from 6.06 to 6.38. In terms of shear force, the O × P had the highest shear value, ranging from 35.89N to 74.80N, compared to other genetic groups. Potchefstroom Koekoek had normal meat colour and pH, whereas the Venda breed had tougher meat than other genotypes. The results of the present study might be useful for local chicken farmers to improve carcass traits.

Combining yield, earliness and plant height in a single genotype: a proposal for breeding in grain sorghum (Sorghum bicolor L.)

Abstract: Grain sorghum production has expanded during the off-season when rainfall oscillates and becomes insufficient. Aiming to obtain better adapted cultivars, breeding programs have sought new combinations of hybrids with earliness, high grain yield, and ideal plant height for harvesting. This study aimed to estimate de combining ability of grain sorghum lines, proposing a breeding strategy, to identify hybrids gathering high yield, earliness, and desired plant height. Thirty-six hybrids from crosses of 12 lines were evaluated at two sites in the Brazilian region known as Cerrado biome. The evaluated traits were: days to flowering, plant height, and grain yield. For the diallel analysis, Method 4 of Griffing adapted to partial diallel was adopted. By combining ability analysis, we identified promising lines to be used as parents to obtain more yielding, early, and ideal height hybrids. The findings allowed us to propose a breeding strategy, in which complex crosses should be performed to gather favorable alleles in new restorer and male-sterile lines. The hybrids 7, 9, 19, and 22 are the most suitable for growing in the evaluated sites. Highlights: Combining ability analysis allows the identification of promising parents to be used in grain sorghum breeding program. Favorable alleles for each trait are contained in different parents, which makes gene pyramiding a necessary strategy to simultaneously gathering earliness, plant height suitable for harvesting, and high yield in a single hybrid. To improve the R lines, the cross between M2 (good donor for shorter height) x M5 (good donor for earliness) should be performed, and the hybrid resulting from M2xM5 can be crossed with the M4 line (good donor for high grain yield). The hybrid generated by the cross F1-B x F4-B (high earliness) should be crossed with the hybrid derived from F6-B x F5-B (shorter height), and the hybrid resulting should be crossed with the hybrid generated by F2-B x F3-B (high grain yield).

Gene action for grain protein content in durum wheat

Abstract: The aim of this study was to determine the gene action and combining ability of durum wheat for grain protein content. During the three year period a diallel cross was carried out with five modern parents of durum wheat – ‘Victoria’, ‘Deni’, ‘Superdur’, ‘Progres’ and ‘Predel’. Ten hybrid combinations and the parents were grown in the experimental field of the Field Crops Institute, Chirpan. The experiment was performed by the randomize block method design in three replications. It was found that in the inheritance of grain protein content dominance and overdominance in positive and negative directions were observed. Statistical processing of the results showed that both additive and non-additive genetic effects have influenced on inheritance. Non-additive gene effects (SCA) had a greater role in inheritance. This suggests that an effective selection for this trait could begin in later generations. The combining ability analysis has identified two good general combinators (Predel and Superdur varieties) that could be used as donors to increase the values of the trait protein content in grain. Several crosses showing positive and significant SCA effects have also been identified, suitable for achieving reliable transgressive genotypes.

Combining ability studies in sesame (Sesamum indicum L.)

Abstract: In the present investigation eight parents were grown for making half diallel crosses [n (n-1)/2] among them and next year eight parents and 28 f1 hybrids were grown in CRBD with three replications for evaluation of yield and yield attributing traits to assess the combining ability was carried out by using the procedure given by griffing (1956) of method 2 model. Analysis of variance for combining ability revealed that the mean sum of squares associated with gea and sea were highly. Significant for all the characters except for plant height and it is noticed that additive as well as non- additive genes were operating in the expression of these traits, indicating existence of hudge amount of genetic variability in the experimental material. Parent TKG-22 was the best general combiner for high seed yield and early maturing along with most of the yield attributing traits. Parent JLS-120 was also identified as good general combiner for seed yield along with most of the yield contributing traits. Five cross combination Viz JTS-8xTKG-22, JTS-8xJLS-120, PT-2xJLS-120, RT-366xTKG-22 and MT-11-8-2xRT-368 identified as good specific combiner for seed yield and its contributing characters. Cross RT-366xRT-368 showed highly significant negative sea effects in desirable direction for early maturing.

Gene Action, Heterotic Patterns, and Inter-Trait Relationships of Early Maturing Pro-Vitamin A Maize Inbred Lines and Performance of Testcrosses under Contrasting Environments

Abstract: Vitamin A deficiency is the leading cause of night blindness, total blindness, maternal and childhood mortality in developing countries. Drought, low soil nitrogen and Striga hermonthica parasitism are major constraints to maize production in sub-Saharan Africa (SSA). Thus, the development of multiple stress tolerant maize varieties with elevated levels of PVA is an economically feasible approach to simultaneously tackle malnutrition and food insecurity in SSA. The objectives of this study were to determine the gene action modulating the inheritance of grain yield and other traits, group the inbred lines, investigate inter-trait relationships among grain yield and other traits and assess the performance and stability of single-cross hybrids derived from a set of inbred lines under stress and non-stress environments. One hundred and ninety diallel crosses plus six hybrid checks were evaluated under managed drought at Ikenne during the 2016/17 and 2017/18 dry seasons, low soil N conditions at Mokwa and Ile-Ife, Striga infestation at Abuja and Mokwa, and optimal management conditions at Ikenne, Kadawa, Abuja, Bagauda and Mokwa during the 2016 and 2017 growing seasons. Both additive and non-additive gene actions were prominent in the inheritance of grain yield and other measured traits under stress and optimal management conditions. However, additive gene action was preponderant over the non-additive. The PVA inbreds were classified into three heterotic groups with TZEI 25 and TZEIOR 164 identified as inbred testers for heterotic groups 2 and 3, respectively. Plant and ear heights, ears per plant, plant and ear aspects were identified as reliable secondary traits for genetic enhancement of grain yield under both stress and non-stress conditions. Hybrids TZEIOR 4 × TZEIOR 158 and TZEIOR 119 × TZEIOR 158 were outstanding in performance and should be tested extensively for possible commercialization to combat malnutrition and food insecurity in SSA.