Showing papers on "Diallel cross published in 2017"

Relationships between genetic distance, combining ability and heterosis in rapeseed ( Brassica napus L.)

Abstract: Present study was conducted to evaluate the relationship between parental genetic distances, combining ability and heterosis in rapeseed (Brassica napus L.). Nine elite inbreds widely used in Chinese rapeseed breeding programs, were crossed in a diallel design to develop 36 hybrids and evaluated together with their parents across four environments. Genetic distances among lines were measured from 11 morphological traits, and SSR and SRAP molecular markers. Results showed that genetic distance evaluated by total molecular markers (GDtotal) had no correlation with heterosis. In order to make a better prediction, significant markers and favoring markers were selected from the total molecular markers, and results revealed that genetic distance measured by favoring markers (GDfavor) significantly and positively correlated with number of seeds per silique, thousand seed weight, seed yield per plant and seed yield per plot for high-check heterosis (HCK) and sum of parental general combining ability (GCA(f+m)). The selected favoring markers could be used for the further study on prediction of heterosis for yield and yield related traits. The magnitudes of correlation coefficients of morphological distances with mid-parent heterosis, high-parent heterosis and HCK for yield and other traits were mostly not significant. Interestingly, more higher levels of correlations were found between GCA(f+m) and heterosis, which indicated that using the information of GCA(f+m) to predict heterosis appeared an important method in rapeseed. Three out yielding crosses, 8D129 × 8E001 (HCK, 23.56%), 8C189 × 8C272 (23.31%), and 8C343 × 8D129 (20.08%), were identified as ideal hybrids evaluated across four environments and may be promoted for adoption and commercialization in China.

Genetic effects and genotype×environment interactions govern seed oil content in Brassica napus L.

Abstract: As seed oil content (OC) is a key measure of rapeseed quality, better understanding the genetic basis of OC would greatly facilitate the breeding of high-oil cultivars. Here, we investigated the components of genetic effects and genotype × environment interactions (GE) that govern OC using a full diallel set of nine parents, which represented a wide range of the Chinese rapeseed cultivars and pure lines with various OCs. Our results from an embryo-cytoplasm-maternal (GoCGm) model for diploid seeds showed that OC was primarily determined by genetic effects (VG) and GE (VGE), which together accounted for 86.19% of the phenotypic variance (VP). GE (VGE) alone accounted for 51.68% of the total genetic variance, indicating the importance of GE interaction for OC. Furthermore, maternal variance explained 75.03% of the total genetic variance, embryo and cytoplasmic effects accounted for 21.02% and 3.95%, respectively. We also found that the OC of F1 seeds was mainly determined by maternal effect and slightly affected by xenia. Thus, the OC of rapeseed was simultaneously affected by various genetic components, including maternal, embryo, cytoplasm, xenia and GE effects. In addition, general combining ability (GCA), specific combining ability (SCA), and maternal variance had significant influence on OC. The lines H2 and H1 were good general combiners, suggesting that they would be the best parental candidates for OC improvement. Crosses H3 × M2 and H1 × M3 exhibited significant SCA, suggesting their potentials in hybrid development. Our study thoroughly investigated and reliably quantified various genetic factors associated with OC of rapeseed by using a full diallel and backcross and reciprocal backcross. This findings lay a foundation for future genetic studies of OC and provide guidance for breeding of high-oil rapeseed cultivars.

Combining ability, heterosis, genetic distance and their intercorrelations for waterlogging tolerance traits in chrysanthemum

Abstract: Waterlogging tolerance (WT) is a major objective in chrysanthemum breeding programs, and although certain genotypes with different tolerance levels have been identified, their value as parents for WT breeding is unknown. Here, twelve F1 crosses derived from an incomplete diallel mating scheme were conducted to investigate combining ability and heterosis for WT and their relationships with parental genetic distance. The results showed that the membership function value of waterlogging (MFVW) was controlled by additive and non-additive gene effects, whereas other growth and biomass traits were mainly controlled by non-additive gene effects. The estimated broad and narrow sense heritabilities of the MFVW were 97.5 and 51.5%, respectively. Combining ability analyses indicated that ‘Nannong Xuefeng’ showing the largest general combining ability (GCA) effect for the MFVW was the best combiner, and identified several best cross combinations with high positive specific combining ability (SCA) effects for most WT-related traits. Mid- and high-parent heterosis occurred widely. The three distance measures, based on phenotypic traits (PD), molecular markers (GD) and markers linked with quantitative trait loci (QTL-GD), presented a non-significant correlation with combining ability except for the GD with GCA for the relative root fresh weight. The correlations between the QTL-GD and heterosis were significant for certain traits and generally higher than that of the PD or GD and heterosis. The SCA effects were positively correlated with heterosis for most of the WT traits (0.51 ≤ r ≤ 0.80). The findings benefit understanding the inheritance mode and then achieving desirable improvement for WT in chrysanthemum.

Genetic analysis of tropical quality protein maize (Zea mays L.) germplasm

Abstract: Maize (Zea mays L.) is an important source of carbohydrates and protein in the diet in sub-Saharan Africa. The objectives of this study were to (i) estimate general (GCA) and specific combining abilities (SCA) of 13 new quality protein maize (QPM) lines in a diallel under stress and non-stress conditions, (ii) compare observed and predicted performance of QPM hybrids, (iii) characterize genetic diversity among the 13 QPM lines using single nucleotide polymorphism (SNP) markers and assess the relationship between genetic distance and hybrid performance, and (iv) assess diversity and population structure in 116 new QPM inbred lines as compared to eight older tropical QPM lines and 15 non-QPM lines. The GCA and SCA effects were significant for most traits under optimal conditions, indicating that both additive and non-additive genetic effects were important for inheritance of the traits. Additive genetic effects appeared to govern inheritance of most traits under optimal conditions and across environments. Non-additive genetic effects were more important for inheritance of grain yield but additive effects controlled most agronomic traits under drought stress conditions. Inbred lines CKL08056, CKL07292, and CKL07001 had desirable GCA effects for grain yield across drought stress and non-stress conditions. Prediction efficiency for grain yield was highest under optimal conditions. The classification of 139 inbred lines with 95 SNPs generated six clusters, four of which contained 10 or fewer lines, and 16 lines of mixed co-ancestry. There was good agreement between Neighbor Joining dendrogram and Structure classification. The QPM lines used in the diallel were nearly uniformly spread throughout the dendrogram. There was no relationship between genetic distance and grain yield in either the optimal or stressed environments in this study. The genetic diversity in mid-altitude maize germplasm is ample, and the addition of the QPM germplasm did not increase it measurably.

Heterosis and combining ability of seven maize germplasm populations.

Abstract: Understanding the combining ability and heterosis of available germplasm is a prerequisite for successful maize improvement and breeding. The objectives of this study were to analyze the combining ability and heterosis of seven representative maize germplasm populations, and further, to evaluate their potential utility in germplasm improvement. A total of 21 crosses were made among these seven populations in a complete diallel without reciprocals. The parental populations and 21 crosses were evaluated for days to silking (DS), ear height (EH), and grain yield (GY) in the Northeast and Yellow and Huai River maize growing areas in China in 2012. Csyn5, Csyn7, Cpop.11, and Cpop.12 had desirable general combining ability (GCA) effects for DS and EH in both the Northeast China mega-environment (NCM) and the Yellow and Huai River Regions of China mega-environment (YHCM). Cpop.11 possessed a favorable GCA effect for GY in the NCM, as did Csyn5, Cpop.17, and Cpop.18 in the YHCM. Csyn6 and Csyn7 exhibited tremendous yield-enhancing potential in both mega-environments. Additionally, six combinations including Csyn7 × Csyn6, Csyn5 × Csyn6, Cpop.11 × Cpop.18, Cpop.12 × Cpop.17, Csyn7 × Cpop.17, and Csyn5 × Csyn7 exhibited better specific combining ability effects for GY, yield performance, and mid-parent heterosis in the appropriate mega-environment. These results indicated that the seven populations would be very useful for the improvement of related agronomic traits, and the six candidate combinations possessed great potential for further improvement and utilization.

Combining Ability and Heterosis in Maize ( Zea mays L.)

Abstract: Combining ability for growth parameter and yield components were evaluated in a 7×7 diallel fashion in maize at the research farm of Plant Breeding Division, Bangladesh Agricultural Research Institute (BARI), Joydebpur, Gazipur during Rabi season 2013-14 to determine the general combining ability and specific combining ability of parents and the crosses. Significant general and specific combining ability variances were observed for some of the characters. The overall study of gca effects suggested that parent WL3 was significant for general combiner for yield, WL2 and WL3for earliness and WL1 for short stature. These parents could be used in future breeding programme to improve maize yield with desirable traits. The good combiner parents for different traits could be used in hybridization to improve yield as well as with desirable traits as donor parents for the accumulation of favorable genes. For yield improvement in maize both additive and non additive genes should be exploited through a suitable breeding method. However, the crosses WL1×WL6, WL1×WL7, WL4×WL5, WL6×WL7showed high sca effect for kernel yield. The significant positive sca of crosses could be used for commercial variety development after verifying them. The maximum heterosis was recorded in WL1×WL6 (15.60**%) when BHM 7 used as check and heterosis ranged from -56.59 to 15.60%. Only one hybrid WL2×WL7 recorded negative heterosis against BHM 7 for days to maturity.

Genetic analysis of yield and fruit traits in cantaloupe cultivars

Abstract: The purpose of this research was to evaluate the combining ability of six local Iranian and one imported cantaloupe cultivar. Heritability of traits was estimated using a half-diallel mating design. Seven parents and their crosses were evaluated in 2013 and 2014. The greatest general combining ability (GCA) for yield and fruit number was for “Rish-baba” (0.53 kg/plant and 0.3, respectively). The cultivar “Ananasi” had the highest GCA for fruit weight and soluble solids content (SSC) (0.088 kg and 1.4, respectively). “Ananasi” presented the highest GCA values for fruit firmness, chlorophyll a and b and carotenoid content, as well as the highest total chlorophyll content. The cross Garmak × Rish-baba showed the highest specific combining ability (SCA) for yield with heterosis value of 99%. High heritability estimates for SSC (0.52), flesh thickness (0.61) and concentration of chlorophyll a (0.7) were obtained. Although there were significant SCAs for yield, the parents are suggested to be improved prior to hybrid development. The parent “Ananasi” appears to be a suitable donor in breeding programmes.

Genetic analysis of early-maturing maize (Zea Mays L.) inbred lines under stress and nonstress conditions

Abstract: Early-maturing maize (Zea Mays L) germplasm developed from diverse sources has the potential for use in developing maize hybrids suitable for increasing maize production in the dry ecologies of eastern Africa A diallel study was conducted to estimate general combining ability (GCA) of 12 early-maturing maize inbred lines, identify potential single-cross hybrids for use as parents, assess genetic diversity among the inbred lines, and relate genetic distance to specific combining ability (SCA) and hybrid performance Sixty-six F1 diallel hybrids were evaluated under optimal and drought stress conditions at four locations in Kenya and Uganda The parental inbred lines were genotyped using 94 single nucleotide polymorphism (SNP) markers Additive gene action was more important than nonadditive gene action for inheritance of grain yield (GY) under optimal conditions However, nonadditive gene effects were more important in the inheritance of GY under drought and across all environments Inbred lines

Genome-wide dissection of heterosis for yield traits in two-line hybrid rice populations.

Abstract: Heterosis has been widely utilized in agriculture and is important for world food safety. Many genetic models have been proposed as mechanisms underlying heterosis during the past century, yet more evidence is needed to support such models. To investigate heterosis in two-line hybrid rice, we generated a partial diallel crossing scheme, which consisted of approximately 500 F1 hybrids derived from 14 male sterile lines and 39 restorer lines. In this population, increased panicle number played the most important role in yield heterosis of hybrid rice. Genome-wide association studies identified many QTLs related to the yield traits of F1 hybrids, better paternal heterosis and special combining ability. Relevant genes, including Hd3a, qGL3, OsmiR156h, and LAX2, were identified as candidates within these QTLs. Nearly forty percent of the QTLs had only two genotypes in the F1 hybrids, mainly because the maternal lines were under intense selective pressure. Further analysis found male sterile lines and restorer lines made different superior allele contributions to F1 hybrids, and their contributions varied among different traits. These results extend our understanding of the molecular basis of heterosis in two-line hybrid rice.

Are strain genetic effect and heterosis expression altered with culture system and rearing environment in the Portuguese oyster (Crassostrea angulata)

Abstract: Re-ranking of strain additive genetic effect and heterosis expression in different culture environments is not well understood in shellfish species. This study was carried out to estimate the strain additive genetic and heterotic effects on harvest body weight in a 3 × 3 complete diallel cross involving three populations of Portuguese oyster (Crassostrea angulata), two populations from Cat Ba (RIA1) and Nam Dinh, northern Vietnam, and an imported stock from China. Strip spawning was applied to produce full- and half-sib families simultaneously of nine cross-combinations for performance testing at two locations (Cat Ba Island, Hai Phong city and Van Don Island, Quang Ninh province, Vietnam) using two culture systems (‘single seed’ and ‘cultch set’). A total of 7269 individual oysters were examined over a grow-out period of 270 days. A linear mixed model was used to estimate strain additive genetic and heterotic effects for body weight at harvest. Ranking of strains based on their additive genetic effects did not differ between the locations and culture systems. The non-additive genetic (heterotic) effects were low and not significantly different from zero for the traits studied among culture systems. There were no significant differences in levels of heterosis for harvest body weight between the two test environments or culture systems. Based on the non-significant heterotic and large additive genetic effects among strains used for this study, a future breeding programme in this species (C. angulata), setting aside issues of diversity, could be based simply on choice among different strains based on their performance.

Metapopulation patterns of additive and nonadditive genetic variance in the sea bass (Dicentrarchus labrax).

Abstract: Describing and explaining the geographic within-species variation in phenotypes ("phenogeography") in the sea over a species distribution range is central to our understanding of a variety of eco-evolutionary topics. However, phenogeographic studies that have a large potential to investigate adaptive variation are overcome by phylogeographic studies, still mainly focusing on neutral markers. How genotypic and phenotypic data could covary over large geographic scales remains poorly understood in marine species. We crossed 75 noninbred sires (five origins) and 26 dams (two origins; each side of a hybrid zone) in a factorial diallel cross in order to investigate geographic variation for early survival and sex ratio in the metapopulation of the European sea bass (Dicentrarchus labrax), a highly prized marine fish species. Full-sib families (N = 1,950) were produced and reared in a common environment. Parentage assignment of 7,200 individuals was performed with seven microsatellite markers. Generalized linear models showed significant additive effects for both traits and pleiotropy between traits. A significant nonadditive genetic effect was detected. Different expression of traits and distinct relative performances were found for reciprocal crosses involving populations located on each side of the main hybrid zone located at the Almeria-Oran front, illustrating asymmetric reproductive isolation. The poor fitness performance observed for the Western Mediterranean population of sea bass is discussed as it represents the main source of seed hatchery production, but also because it potentially illustrates nonadaptive introgression and maladaptation.

Diallel Analysis of Some Important Grain Yield Traits in Bread Wheat Crosses

Abstract: One of the most important tasks in wheat breeding program is development of high yielding wheat cultivars by crossing the lines with good general combining ability (GCA) and selecting desirable genotypes within its segregating population for grain yield traits. The objective of this study was to estimate the combining ability and gene action involved in the expression of the traits grain weight per spike and grain weight per plant of wheat in F1 generations, in 5 × 5 half diallel cross of bread wheat varieties (Triticum aestivum L.). The results of applying combining ability analysis indicated that among the parents, genotypes Sara, Pobeda and Renesansa were found to be the best general combiners for the both investigated traits. The best specific crosses for both traits were Sara/Partizanka, Pobeda/Sara, Renesansa/Partizanka, Partizanka/Pesma and Pobeda/Pesma. Most of the specific crosses involved high × high, high × low and low × low general combiners. The results of regression analysis, as well as the analyses of components of genetic variation indicated over-dominance in the inheritance of examined traits suggested that selection in later segregating generations may lead to fairly good improvement in these characters

Combining ability × environment interaction and genetic analysis for agronomic traits in safflower (Carthamus tinctorius L.): biplot as a tool for diallel data

Abstract: Combining ability × environment interaction is considerable to identify the effect of environment on the combining ability and gene action of the traits to select appropriate parents for safflower hybrid production. The 36 genotype (28 F 2 progenies of eight-parent half-diallel crosses across 8 parental genotypes) of safflower were studied to investigate the mentioned parameters across different geographical regions of Iran. The results indicated significant differences among parents for general and specific combining ability, except for seeds per capitulum across three environments. The overall results indicated that K 21 and Mex.22-191 were excellent parents with greater general combining ability for the improvement of seed yield in safflower. The K 21 × Mex.22-191 hybrid could be, therefore, employed for the production of high seed yield in safflower breeding. The estimates of genetic variance components recommended the importance of additive- dominance genetic effects that contributed to variation in yield per plant. Such gene action expression for seed yield needs auxiliary methods based on hybridization and selection for seed yield advancement in safflower.

Combining Ability and Heterosis of Selected Grain and Forage Dual Purpose Sorghum Genotypes

Abstract: Sorghum is an important food and feed source in mixed crop-livestock production systems where its dual usage is a preferred option, especially among the resource poor small-scale farmers. Attempts to improve fodder quality traits in maize have been at the expense of grain traits and vice versa, but other studies demonstrated that it was possible to select for high stem biomass without compromising the improvement of grain yields in sorghum. As a follow up to this effort, this study was undertaken to estimate the combining ability of grain and forage sorghum genotypes and determine heterosis for several traits as a criteria for improving dual purpose sorghum cultivars. Four grain and four forage sorghum cultivars were crossed to generate 23 crosses following the half diallel mating design scheme at Makerere University Agricultural Research institute Kabanyolo (MUARIK) in 2013. The crosses were evaluated at three locations in Uganda during two rainy seasons of 2014. Data were taken and analysed on leaf area, leaf-stem ratio, plant height, seed weight, grain yield, and biomass. Results indicated that the gene action for the traits under observation was controlled by both additive and non additive genetic effects. Majority of the parental lines had significant GCA estimates for all traits except line 20 for grain yield, lines 22 and 34 for plant height, line 35 for leaf-stem ratio, and line 22 for days to flowering. Significant (P ≤ 0.05) SCA estimates were prominent in most of the individual parental combinations for all traits except leaf area and leaf-stem ratio indicating the role of dominance gene action. Bakers ratio and heritability coefficients were > 52% for biomass, flowering duration and plant height indicating that genetic gains can be achieved by conventional breeding for the three traits. Heterosis in grain yield and biomass over both the mid and better parents was shown by more than half of the crosses studied. This study suggested that both inter and intra allelic interactions were involved in the expression of the traits.

Assessment of combining ability for yield and quality components in hot pepper (Capsicum annuum L.)

Abstract: Six parental genotypes and their thirty F 1 hybrids in a full diallel cross system with reciprocals, were used in the present study to estimate combining ability for five quantitative and five qualitative traits in hot pepper. The mean sum of squares due to general combining ability (GCA), specific combining ability (SCA) and reciprocal combining ability (RCA) were significant for all the characters which suggest that these parents could have performed differently in different combinations indicating interallelic interactions. All the traits studied exhibited greater SCA variance than GCA, suggesting that these traits are controlled by non-additive gene action. Analysis of the GCA effects of parents for various traits revealed that LCA625, K1 and PKM1 were the best general combiners for almost all the traits. Estimates of SCA effects showed that the hybrids LCA625 × K1, K1 × Arka LohitandPusa Jwala × PKM1were found to be the best combiners for yield and its attributes. The hybrid K1 × Arka Lohitwas the best reciprocal combiner for quality parameters based on its better mean performance and combining ability. These results suggest that commercial production of hot pepper hybrids and isolation of pure lines from these hybrids is a possible way to enhance the yield and fruit quality.

Combining ability analysis of quality protein maize (QPM) inbred lines for grain yield, agronomic traits and reaction to grey leaf spot in mid-altitude areas of Ethiopia

Abstract: A study was carried out to study the combining ability effects of diallel cross hybrids for grain yield, agronomic traits and reaction to grey leaf spot (GLS) Forty five experimental diallel cross hybrids made from ten quality protein maize (QPM) inbred lines with varying level of resistance to GLS were evaluated along with three checks at Bako and Jima Research Centers during 2014/2015 cropping season Analysis of variance showed significant variation (P≤005) among genotypes and between environments This depicted the existence of genetic variation among genotypes in all studied traits Mean squares characterized by general and specific combining ability effects were significant for the most traits and this suggested that both additive and non-additive gene actions have the contribution in the expression of the traits However, the ratio of General combining ability (GCA) to specific combining ability (SCA) sum of squares were greater than unity, this revealed that there was preponderance of additive gene action in the expression of all the traits under study Among inbred lines studied P6 and P10 had a desirable GCA effects for grain yield whereas P1, P4 and P10 were the best general combiners for GLS resistance Furthermore, P10 was identified as good general combiner for grain yield as well as GLS is therefore recommended to be used in breeding programs with a purpose of developing both high yielder as well as GLS disease resistant genotypes Crosses, P2×P8 and P4×P6 showed the most desirable performances and SCA effects for grain yield Grain yield showed positive correlation between ear per plant, plant and ear height, and ear position whereas negative correlation were observed with GLS, days to anthesis, days to silking, plant aspect and ear aspect traits The information which is generated in this study could be helpful to develop high yielding maize varieties with good agronomic traits as well as GLS resistance Key words: Agronomic traits, diallel, general combining ability, gray leaf spot, quality protein maize, specific combining ability

Identifying superior spring wheat genotypes through diallel approaches

Abstract: Diallel crosses enable plant breeders taking decisions concerning the parental choice for developing new varieties. Recently, a large number of methodological models have been reported. The objecti...

Combining ability, heritability and genotypic relations of different physiological traits in cacao hybrids.

Abstract: Selecting parents and evaluating progenies is a very important step in breeding programs and involves approaches such as understanding the initial stages of growth and characterizing the variability among genotypes for different parameters, such as physiological, growth, biomass partitioning and nutrient translocation to the aerial part. In these cases, facilitating tools can be used to understand the involved gene dynamics, such as diallel crosses and genetic and phenotypic correlations. Our main hypothesis is that the contrasting phenotypes of these parental genotypes of cocoa used are due to genetic factors, and progenies derived from crosses of these parental genotypes are useful for breeding programs related to plant architecture, physiological parameters and translocation of mineral nutrients. We aimed to evaluate the combining abilities in progenies of cacao (Theobroma cacao L) originating from contrasting parents for canopy vigor. Emphasis was given to the evaluation of morphological and physiological parameters and the phenotypic and genotypic correlations to understand the dynamics of the action of the genes involved, as well as in expression profile from genes of gibberellins biosynthesis pathway in the parents. Fifteen F1 progenies were obtained from crosses of six clones (IMC 67, P4B, PUCALA, SCA 6, SCA 24 and SJ 02) that were evaluated in a randomized complete block design with four replicates of 12 plants per progeny, in a balanced half table diallel scheme. It is possible to identify and select plants and progenies of low, medium and high height, as there is expressive genetic variability for the evaluated parameters, some of these on higher additive effects, others on larger nonadditive effects and others under a balance of these effects. Most physiological parameters evaluated show that for selection of plants with the desired performance, no complex breeding methods would be necessary due to the high and medium heritability observed. Strong genetic components were observed from many of the correlations, which indicate the possibility to formulate selection indices for multi-traits, such as dwarfism or semidwarfism, tolerance to increase of leaf sodium concentrations and maintenance of the photosynthetic apparatus integrity under these conditions. Additionally, plants with higher carbon fixation, better water use, higher carboxylation efficiency and greater magnesium accumulation in leaves can be selected.

Mode of inheritance of low-N tolerance adaptive traits in wheat (Triticum aestivum L.) under contrasting nitrogen environments

Abstract: Because of essential economic and ecological concerns, there is increased interest worldwide in developing wheat cultivars that are more efficient in utilizing nitrogen (N) and better suited to N limitations The objective of the present investigation was to get information on the type of gene action controlling the inheritance of wheat low-N tolerance traits in order to start a breeding program for improving such traits Six parents of contrasting low-N tolerance were crossed in a diallel fashion Evaluation of 6 parents, 15 F 1 crosses and 15 F 2 crosses was done using a randomized complete block design with three replications under two levels of soil N, ie low-N (0 kg N/ha) and high-N (180 kg N/ha)The magnitude of dominance variance inF 2 's for all studied traits was much greater than that of additive variance under both high N and low N, suggesting that selection should be postponed to later segregating generations in order to eliminate masking effects of dominance variance and take advantage of the additive variance for the improvement of nitrogen use efficiency and grain yield traits Narrow-sense heritability (h 2 n ) in F 2 's was generally of higher magnitude under low-N than high-N, suggesting that it is better to practice selection for studied nitrogen efficiency and grain yield traits under low-N conditions to obtain higher values of selection gain

Genetic analysis of morpho-physiological traits and yield components in F2 partial diallel crosses of bread wheat (Triticum aestivum L.)

Abstract: Wheat breeding in the semi-arid region of Algeria aims to develop new cultivars combining high productivity and good abiotic stress tolerance. Therefore, it is essential to understand the mode of gene effects implicated in the genetic control of these characteristics. Nine parents of bread wheat and twenty derived F 2 hybrid populations developed in a partial diallel scheme were evaluated with three replications at the experimental site of the National Agronomic Research Institute of Algeria (INRAA), Setif unit, during the 2012-2013 crop season. Results of the diallel analysis, indicated that the components associated with additive effects were more relevant than those associated with the dominance effects for most of the studied traits. Based on the proportion between dominant and recessive genes in all parents, the dominant alleles were present in greater frequency in group 1. Values of the gene proportion with positive and negative effects in the parents revealed an unequal distribution of dominant genes in the parents for almost all the traits except for chlorophyll content and grain number per spike which showed a symmetric distribution. The average degree of dominance indicated over-dominance for most of traits, suggesting that selection for these traits, in early generation, will be less efficient. Key words : genetic parameters, inheritance, selection, semi-arid, yield.

Combining ability, heterosis, and genetic distance among nine elite American Pima cotton genotypes ( Gossypium barbadense )

Abstract: American Pima cotton (Gossypium barbadense L.) is grown in the southwest United States, and no Pima cotton hybrid is commercially grown. In this study, six commercial Pima cultivars (Pima S-7, Pima S-6, Phy 76, BR 007, DP 340, and DP 744) and three elite germplasm lines (SI 1331, 93252, and 8810) were crossed in a diallel mating scheme without reciprocals, and their 36 F2 and F3 progeny were planted in replicated tests at two locations (L) in 2004–2005. Yield and fiber traits were analyzed using Griffing’s Model 1, Method 2 diallel analysis. Genetic distance (GD) of parent lines was determined using 661 AFLP molecular markers. Across locations, significant genotype (G) and general combining ability (GCA) effects were detected for yield, boll size, lint percent, micronaire, 2.5% fiber length, fiber strength, and elongation. Significant specific combining ability (SCA) effects were detected for yield, micronaire, and strength. Lint yield and the yield components- boll size and lint percent exhibited significant G × L interactions. Significant GCA × L interactions occurred for yield and lint percent. Yield, boll size, and micronaire also had significant SCA × L interactions. No significant GCA or SCA by L interactions were detected for fiber length, strength, and elongation. The mean mid-parent heterosis (MPH) of the 36 hybrids in lint yield was low in F2, but non-existent in F3. Among the nine parents, Pima S-7 and DP 340 had the highest and significant positive GCA effects for lint yield, lint percent, and boll weight across tests. Only several F2 hybrids with Pima S-7 and DP 340 as one parent displayed some levels of useful heterosis in lint yield in the two locations, as compared to Pima S-7 as the check. MPH for other agronomic and fiber quality traits was low to non-existent in both generations. The average GD of the parents were not significantly correlated with their GCA effects, and GD between parents was also not correlated with SCA and MPH of their hybrids, with the exception of lint yield at the Las Cruces location where a significant negative correlation was obtained. However, GD of the parents was correlated with the performance of hybrids in lint yield, fiber length, fiber strength and elongation in one or two tests. This study represented one of the first studies to estimate heterosis, combining ability, and their relationship with genetic distance of parents in a representative subset of Pima cotton genotypes.

Combining ability of spring barley varieties in the direct diallel cross system.

Abstract: It is necessary to know the combining ability of starting material for effective breeding to create varieties. The research aim was to determine the peculiarities of the general combining ability (GCA) and specific combining ability (SCA) and the ratio of their variances for awned and awnless varieties and their parental forms in F1. The study was conducted in 2014–2015. Spring barley varieties and their parental forms were used in direct diallel crosses. In 2014–2015, peculiarities of the combining ability of awned and awnless spring barley varieties and their parental forms were determined in F1. We highlighted varieties with strong GCA effects: ‘Badioryy’ for plant productivity; ‘Dzherelo’, ‘Badioryy’, ‘Vitrazh’ and ‘Maliovnychyy’ for grain number per spike; ‘Dzherelo’, ‘Badioryy’, ‘Etiket’, ‘Granal’, ‘Modern’, ‘Vitrazh’, and ‘Tolar’ for 1 000-grain weight; ‘Dzherelo’, ‘Granal’, and ‘Vitrazh’ for spike length; ‘Dzherelo’ and ‘Maliovnychyy’ for spikelet number per spike; ‘Dzherelo’, ‘Ba dioryy’ and ‘Granal’ for plant height; ‘Zvershennya’ and ‘Badioryy’ for productive tillering; ‘Zvershennya’ and ‘Badioryy’ for total tillering; and ‘Badioryy’ for straw weight. These varieties had the largest numbers of genes that positively determine these traits. The level of combining ability of parental forms may be manifested differently in varieties created via hybridization of them. GCA variances exceeded SCA variances in ‘Zvershennya’ in 2014–2015 for the trait “1 000-grain weight” (GCA – 4.20 and 4.03, respectively; SCA – 3.78 and 3.84, respectively), therefore, it is determined mainly by additive gene effects. Strong and weak SCA effects were observed for plant productivity (grain weight) and its structural components (productive tillering, grain number per spike, 1 000-grain weight). Strong SCA effects were the most numerous for the trait “1 000-grain weight.”

Response of wheat to post-anthesis water stress, and the nature of gene action as revealed by combining ability analysis

Abstract: Post-anthesis water stress is a major limitation to wheat grain yield globally. Understanding the nature of gene action of yield related traits under post-anthesis water stress will help to breed stress-resilient genotypes. Four bread wheat genotypes having varying degree of drought tolerance were crossed in a full-diallel fashion and the resultant crosses along with the parental genotypes, were subjected to water stress after the onset of anthesis in order to investigate their comparative performance and nature of gene action. Parental genotypes Babax (B) and Westonia (W) performed better compared with C306 (C) and Dharwar Dry (D) with respect to relative reduction in grain yield and related traits under stressed condition. Direct cross B × D and reciprocal cross W × C were more tolerant to water stress, while cross between C306 and Dharwar Dry, either direct or reciprocal, produced more sensitive genotypes. Combining ability analysis revealed that both additive and non-additive gene action were involved in governing the inheritance of the studied traits, with predominance of non-additive gene action for most of the traits. Among the parents, Babax and Westonia were better combiners for grain yield under stress condition. B × D in stressed condition, and C × W in both stressed and stress-free conditions, were the most suitable specific crosses. Moreover, specificity of parental genotypes as female parents in cross combination was also evident from the significant reciprocal combining ability effects of certain traits. Low to medium narrow sense heritability and high broad sense heritability were observed for most of the studied traits in both well watered and water stress conditions. The results of the study suggested that specific cross combinations with high specific combining ability involving better performing parents with high general combining ability may generate hybrids as well as segregating populations suitable for further breeding programs.

Combining ability and gene action estimates for some yield attributes in durum wheat (Triticum turgidum L. var. durum)

Abstract: Combining ability and gene action of a set of durum wheat characters were studied using 6 x 6 half diallel crosses. Results revealed that general (GCA) and specific (SCA) combining ability mean squares were significant for all studied traits, suggesting the importance of both additive and non additive components in the inheritance of these traits. Baker ratio indicated the predominance of additive gene effects for majority of traits studied except grain yield. From the GCA effect it was observed that, none of the six parents was good general combiner for all yield components. Among the fifteen crosses, Zenati-Bouteille/Flamengo x Gta/durum followed by Waha x Ofanto, Waha x Mexicali 75 and Ofanto x Guemgoum Rkhem expressed the greatest positive SCA effects for grain yield. Days to heading and spikes number index could be used as an indirect selection criterion for better grain yield. Therefore, selecting early heading genotypes having high fertile tillers number could improve grain yield.

Genetic control of dry matter, starch and sugar content in sweetpotato Section B Soil and plant science

Abstract: Sweetpotato (Ipomoea batatas L. (Lam)) is a nutritious food security crop for most tropical households, but its utilisation is very low in Ghana compared to the other root and tuber crops due to lack of end-user-preferred cultivars. Knowledge on the genetic control of important traits such as dry matter, starch and sugar content of sweetpotato storage roots in a breeding population is critical for making breeding progress in developing sweetpotato varieties preferred by farmers and consumers. This study used diallel mating design to elucidate general combining ability and specific combining ability, to determine the gene action controlling storage root dry matter, starch and sugar content in sweetpotato and the heterotic potential of the traits to facilitate the crop’s improvement for increased utilisation. A general model for estimating genetic effects, GEAN II, was used to analyse the data. Genetic variability was seen for dry matter, starch and sugar content of sweetpotato and much of this genetic variation was additive in nature. The study also revealed significant heterosis in sweetpotato which offers opportunity for breeding non-sweet, high dry matter sweetpotato varieties that are preferred by farmers and consumers in Ghana.

Inheritance pattern of earliness and yield traits in half-diallel crosses of spring wheat

Abstract: A half-diallel mating system was used to evaluate six wheat cultivars and their F1 and F2 populations for inheritance of earliness and morphological and yield traits. These genotypes were crossed i...

Diallel and prediction (REML/BLUP) for yield components in intervarietal maize hybrids

Abstract: Genetic improvement is essential to achieve increments in maize (Zea mays L.) grain yield components. It may be obtained through crosses, which enable to exploit the effects of intervarietal heterosis, allelic complementarity, as well as gene actions and effects. This study estimated the components of variance and genetic parameters (REML/BLUP) of an intervarietal diallel to select and predict the best genotypes for maize yield components. The experimental design was randomized blocks containing 60 intervarietal maize hybrids arranged in three repetitions. They were obtained through intervarietal crosses and evaluated in a diallel scheme, where 14 open-pollinated varieties were designated as parentals. Thus, 10 crosses were performed for each hybrid combination to obtain the number of seeds necessary for the competition test. The measured traits were: grain volume relative index, the mass of one hundred grains, and grain yield. The male parents and the additive genetic fraction were determinants for grain volume relative index. Mass of one hundred grains and grain yield were defined by the specific combining ability, and female parents revealed low narrow sense heritability. The female parent Taquarao and male parent Argentino Amarelo presented the best general combining abilities for the measured traits. The specific combining abilities were expressed for crosses AL 25 x Dente de Ouro Roxo, AL 25 x BRS Pampeano, and Taquarao x Argentino Branco. Genetic estimates and predictions were consistent and applicable to breeding programs and could be applied in future quantitative genetic studies of maize.

Breeding potential of raspberry primocane selections based on their combining abilities

Abstract: Information on the genetic potential of raspberry (Rubus idaeus L.) genotypes for their use in breeding programs is currently limited. We used a diallel mating design to study the breeding values of raspberry primocane fruiting cultivars in terms of their combining ability. The objectives of this study were to identify raspberry genotypes with high general combining ability (GCA) for use in cultivar development, detect the best crosses in terms of their specific combining ability (SCA), and determine the gene action type and heritability of yield and eight of its components. The obtained results showed that the parent cultivar MRSL exhibited the highest GCA effects for the total yield per plant, fruit weight, number of fruit per plant, fruit length, fruit diameter, and number of drupelets per fruit. Genotype C47 had good GCA for the number of canes per plant and plant height and TD-865 had high GCA for high soluble solids content. The narrow-sense heritability estimates were low to moderate (0.00–0.62) fo...