Selection In Later Generations Research Articles

Mapping QTLs for blight resistance and morpho-phenological traits in inter-species hybrid families of chestnut (Castanea spp.).

Chestnut blight (caused by Cryphonectria parasitica), together with Phytophthora root rot (caused by Phytophthora cinnamomi), has nearly extirpated American chestnut (Castanea dentata) from its native range. In contrast to the susceptibility of American chestnut, many Chinese chestnut (C. mollissima) genotypes are resistant to blight. In this research, we performed a series of genome-wide association studies for blight resistance originating from three unrelated Chinese chestnut trees (Mahogany, Nanking and M16) and a Quantitative Trait Locus (QTL) study on a Mahogany-derived inter-species F2 family. We evaluated trees for resistance to blight after artificial inoculation with two fungal strains and scored nine morpho-phenological traits that are the hallmarks of species differentiation between American and Chinese chestnuts. Results support a moderately complex genetic architecture for blight resistance, as 31 QTLs were found on 12 chromosomes across all studies. Additionally, although most morpho-phenological trait QTLs overlap or are adjacent to blight resistance QTLs, they tend to aggregate in a few genomic regions. Finally, comparison between QTL intervals for blight resistance and those previously published for Phytophthora root rot resistance, revealed five common disease resistance regions on chromosomes 1, 5, and 11. Our results suggest that it will be difficult, but still possible to eliminate Chinese chestnut alleles for the morpho-phenological traits while achieving relatively high blight resistance in a backcross hybrid tree. We see potential for a breeding scheme that utilizes marker-assisted selection early for relatively large effect QTLs followed by genome selection in later generations for smaller effect genomic regions.

Estimation of Genetic Variability Parameters for Various Yield Attributing Traits in Germplasm Collection of Rice (Oryza sativa L.)

Genetic variability parameters were studied in 2879 germplasm accessions of rice for 11 quantitative traits. Moderate value of genotypic coefficient of variation (GCV) and phenotypic coefficient variation (PCV) was observed for the traits, 100 seed weight, seedling height, L:B ratio, plant height, and number of effective tillers, whereas rest of the traits had low GCV and PCV values. High heritability was observed for all the traits except leaf length, leaf width and grain yield per plant. High heritability coupled with high genetic advance as percent of mean was observed for 100 seed weight, seedling height and L:B ratio. High heritability coupled with moderate genetic advance as percent of mean was recorded for days to 50% flowering and plant height. The presence of high heritability and high genetic advance as percent of the mean indicated the presence of additive gene effects for controlling aforesaid traits, hence selection in later generations will be rewarding in a breeding programme.

Inheritance of important metric traits of wheat (Triticum aestivum)

Development of salinity tolerant genotypes is important for sustaining wheat productivity in suppressive soils. The generation mean analysis of three bread wheat crosses viz., Lok 1 x Raj 3880, Job 666 x Kharchia 65 and Raj 1972 x Kharchia 65 under normal and saline-sodic environment revealed presence of both additive and non-additive gene effects in the inheritance of grain yield per plant and other contributing characters under both the environments. Among the digenic interactions, all three types of epistatic effects were involved in the inheritance of characters studied. Only duplicate gene interaction was present, wherever available. Hence, intermating in early generations and intense selection in later generations could be successfully adopted for breeding wheat varieties having appreciable salinity tolerance level.

Combining ability and heterosis for yield and grain quality characters in rice (Oryza sativa L.)

Twelve F1 crosses derived from four lines and three testers, crossed in L x T mating design were utilized to estimate the combining ability and heterosis for 17 yield and grain quality traits and also to detect the superior crosses for the breeding program. Analysis of variance showed significant differences among all the traits under study except for plant height in lines. In the case of testers, the traits viz., the number of tillers per plant, the number of productive tillers per plant, hundred seed weight, single plant yield, alkali spreading value, amylose content, gel consistency, kernel length, kernel length breadth ratio, kernel length after cooking and kernel breadth after cooking showed significant values. The SCA variance was higher than the GCA variance for all the characters under study except the alkali spreading value indicating the predominance of non-additive gene action in the inheritance of all the characters. The parents TKM 13, CO 52, ADT 52 and IRBB 21 were adjudged as good general combiners with respect to single plant yield. Hence, these parents can be exploited through pedigree breeding to obtain better recombinants by selection in later generations. Based on the results of per se performance, standard heterosis, and sca effects, the hybrids viz., CO 52 × IRBB 60 and ADT 52 × IRBB 21 were identified as the best specific combiners and these could be used for future breeding. Keywords: Combining ability, Heterosis, SCA, GCA, Rice

Estimation of parameters of genetic variation of spring durum wheat (Triticum durum Desf.) on the basis of “number of grains from the main spike”

Aim. To assess the combining ability, features and nature of the inheritance of the trait “number of grains from the main spike” in varieties of spring durum wheat for their further involvement in breeding programs. Methods. The investigations were carried out at the V. M. Remeslo Institute of Wheat of NAAS of Ukraine. Varieties (‘Zhizel’, ‘MIP Raiduzhna’, ‘Kharkivska 27’, ‘Kharkivska 39’, ‘Spadshchyna’, ‘Kuchumovka’, ‘Tera’) of domestic breeding were involved in crossings according to the full diallel scheme (7 ´ 7). Parental components and F1 were studied in the field in 2016, 2017. Results. The analysis of variance of combining ability showed a significant advantage in general combining abili­ty (GCA) effects. The mean square of the specific combi­ning ability (SCA) was significantly inferior to the GCA, but was significant in both years of the study. Consistently high GCA effects in 2016, 2017 were determined in the variety ‘Tera’ (gi = 1.35; 2.37). Non-alelic gene interaction was not found, which made it possible to analyze the main parame­ters of genetic variation. In two years of investigations, in the phenotypic manifestation of the number of grains from the main spike, dominant effects (H1 and H2) survived over additive ones (D). The average degree of dominance indicated overdominance (H1/D). The indicator of the ave­rage degree of dominance in loci () also indicated overdominance. Dominance was significantly oriented. Dominant effects of genes increased the number of grains, while recessive effects decreased them. At least one group of genes has been identified that has led to dominance. In general, dominant genes (F > 0) or groups of genes dominated quantitatively in cultivar investigated. A high coefficient of heritability in a broad sense (H2 = 0.88; 0.90) indicates a significant phenotypic conditionality to genetic factors. The coefficient of heritability in a narrow sense (h2 = 0.31; 0.38) indicates the average contribution of the additive effects of genes over the dominant ones. Conclusions. The identified breeding and genetic features on the basis of the “number of grains from the main spike” trait make it possible to predict the effectiveness of selections aimed at increasing the trait in the newly hybrid material. However, due to the predominance of dominant effects and overdominance in the genetic control of a trait, selection in later generations will be more effective. Varieties ‘Kharkivska 27’, ‘Kharkivska 39’ and ‘Tera’ should be used as genetic sources to increase the trait “number of grains from the main spike”.

Do lower nitrogen fertilization levels require breeding of different types of cultivars in triticale?

Key messageThe comparably low genotype-by-nitrogen level interaction suggests that selection in early generations can be done under high-input conditions followed by selection under different nitrogen levels to identify genotypes ideally suited for the target environment.Breeding high-yielding, nitrogen-efficient crops is of utmost importance to achieve greater agricultural sustainability. The aim of this study was to evaluate nitrogen use efficiency (NUE) of triticale, investigate long-term genetic trends and the genetic architecture, and develop strategies for NUE improvement by breeding. For this, we evaluated 450 different triticale genotypes under four nitrogen fertilization levels in multi-environment field trials for grain yield, protein content, starch content and derived indices. Analysis of temporal trends revealed that modern cultivars are better in exploiting the available nitrogen. Genome-wide association mapping revealed a complex genetic architecture with many small-effect QTL and a high level of pleiotropy for NUE-related traits, in line with phenotypic correlations. Furthermore, the effect of some QTL was dependent on the nitrogen fertilization level. High correlations of each trait between N levels and the rather low genotype-by-N-level interaction variance showed that generally the same genotypes perform well over different N levels. Nevertheless, the best performing genotype was always a different one. Thus, selection in early generations can be done under high nitrogen fertilizer conditions as these provide a stronger differentiation, but the final selection in later generations should be conducted with a nitrogen fertilization as in the target environment.

Breeding and genetic peculiarities of spring barley 1000 kernel weight under conditions of the central part of the Ukrainian Forest-Steppe

Purpose. To reveal the breeding and genetic peculiarities for spring barley 1000 kernel weight and to identify genetic sources for breeding under conditions of the central part of the Forest-Steppe of Ukraine. Methods. Investigations were carried out at the V. M. Remeslo Myronivka Institute of Wheat of the NAAS of Ukraine. Spring barley F1 of two comp­lete (6 ´ 6) diallel crossing schemes was investigated. The first scheme included modern both domestic and foreign spring barley malting varieties (‘MIP Tytul’, ‘Avhur’, ‘Datcha’, ‘Quench’, ‘Gladys’, ‘Beatrix’), the second – classic covered awned (‘MIP Myroslav’, ‘Sebastian’), awnless (‘Kozyr’, ‘Vitrazh’) and naked (‘Condor’, ‘CDC Rattan’) varieties. Results. Various types of inheritance of 1000 kernel weight were revealed, with the exception of negative dominance. The proportion of combinations with corresponding values ​​of the degree of phenotypic dominance varied depending on the genotypes involved in the crossing and the years of testing. In both crossing schemes, both in 2019 and in 2020, positive overdominance was found in most combinations. The grea­test number of combinations with the manifestation of hete­rosis under different growing conditions was noted when varieties ‘Gladys’ and ‘MIP Myroslav’ were used in crossing. According to the parameters of genetic variation, it was revealed that the trait was determined mainly by the additive-dominant system. The dominance was aimed at increasing the 1000 kernel weight. Only in the second crossing scheme in 2019 the value of the directional dominance indicator was unreliable. In the loci, incomplete dominance in 2019 and over-dominance in 2020 were revealed. Reliably high effects of the general combining ability in both years were noted for varieties ‘Datcha’, ‘Gladys’, ‘MIP Myroslav’, ‘Kozyr’ and ‘Vitrazh’. Conclusions. The revealed breeding and genetic peculiarities indicate that for the overwhelming majority of created hybrid combinations will be required the final selection in later generations, when the dominant alleles are homozygous. Spring barley awned varieties ‘Gladys’, ‘MIP Myroslav’ and ‘Datcha’, as well as awnless varieties ‘Kozyr’ and ‘Vitrage’ can be used as effective genetic sources for increa­sing the 1000 kernel weight

Estimation of epistasis and genetic components of variance for different traits in cucumber (Cucumis sativus)

To estimate epistasis and components of genetic variance a study was carried out during 2016 and 2017 at Experimental Research Farm of Department of Vegetable Science, Dr YSP UH & F Nauni, Solan, (HP) and data were recorded for different qualitative and quantitative traits using triple test cross (TTC) analysis of an inter-varietal cross LC-1-1 × K-75 of cucumber (Cucumis sativus L.). Three testers of cucumber named LC-1-1, K-75 and their F1 (LC-1-1 × K-75) were crossed to 15 inbred lines for detecting the additive, dominance and epistatic components of genetic variance. Good quantum of genetic variability has been generated through triple test cross progenies with respect to different traits studied as revealed by the significant analysis of variance. TTC analysis revealed that overall epistasis and j+l type component were found to be significant for majority of the traits except fruit breadth and total soluble solids. Further, experimental results showed that (i) type of epistasis were also significant for majority of the traits under study. The components of genetic variance were estimated using analysis of variance for sums and differences revealed the importance of both additive (D) as well as dominance (H) components of genetic variance in controlling various traits and showed partial dominance except over dominance for fruit breadth and severity of downy mildew. Therefore, kind of genetic variance revealed from triple test cross can be exploited by intermating selected individuals in early segregating generations with delayed selection in later generations, or recurrent selection followed by pedigree method to exploit both additive and non-additive components along with epistasis in cucumber.

Gene action for yield components and fruit quality characters of tomato genotypes possessing mutant genes through generation mean analysis

Nature of gene action for fruit yield and quality charactersof tomato was determined analyzing the mean and variancesof the six genetic populations (P1, P2, F1, F2, BC1 and BC2) ofthree cross combinations involving parental linespossessing mutant genes viz., Alisa Craig AftAftx Alisa Craighp-1 hp-1, Alisa Craig Aft Aftx Alisa Craig ogcogc and AlisaCraig AftAftx BCT 115 dg dg. In most of the characters inthree cross combinations, simple additive / dominance modelwas inadequate to explain the gene action which indicatedthe involvement of epistasis in the control of the characterconcerned. The characters were under the control of bothfixable and non-fixable gene effects, but non-fixable geneeffects were predominant. Duplicate type epistasis for mostof the characters would hinder the pace of progress throughselection. Postponement of selection in later generationsand development of hybrids were the best breeding strategybecause non-fixable gene effects were predominant for mostof the characters.

English

Common beans are an important nutritious food crop to many people in developing countries. Inadequate soil-P is one of the major constraints to high bean seed yield productivity. Information about genetic effects that control inheritance of root traits in common bean grown under low soil-P conditions is scarce, and that is a challenge for genetic enhancement. This study was therefore implemented to determine inheritance and gene action of root traits in common bean for tolerance to low soil-P. The six generations were evaluated in a completely randomised design with two replicates under low soil-P in a pot experiment. Generation mean analysis revealed that both allelic and non-allelic genetic interactions controlled inheritance of root traits studied. Cumulative main gene effect was higher than epistasis effects. Additive genetic effects were more predominant than dominance effects. Additive and additive × dominance epistatic gene effects were more important in controlling inheritance of root traits under low soil-P. Broad-sense heritability for hypocotyl root number was the highest (93.98 %) while the narrow-sense heritability was moderate (51.13 %). To develop improved genotypes tolerant to low soil-P, recombination crossing should be followed by screening and selection in later generations for high seed yield, root and other preferred traits. Key words: Common bean, inheritance, genotype, gene effect, heritability, low soil-P.

Genetic evaluation of growth and reproductive performances of crossbred pigs reared under intensive system in tropical humid coastal climate.

Pig farming is one of the most economically viable options for the rural backward and resource-poor farmers in Asian countries. Growth rate and litter size are the most important traits based on which the crossbreeding programs are typically planned in commercial pig farming. The modern system of farming with high yielding improved pig germplasm helps in economic growth in piggery enterprises. The present study was undertaken to evaluate the influence of various genetic and non-genetic factors on growth and reproductive performances of 75% crossbred progenies of Large White Yorkshire and indigenous Agonda Goan pigs. Body weights were recorded at birth, weaning, and at monthly intervals up to 10 months of age. Reproductive performances were also recorded for litter size and weights at birth and weaning stages, age at first farrowing, number of services per conception, farrowing interval, and pre-weaning mortality. The general linear model was used to estimate overall least square means of body weights at different ages considering the effects of different factors at certain levels viz., generation (i = first, second, third, fourth), sex (j = male, female), litter size at birth (k = 1-3, 4-6, 7-9, ≥10), parity (l = 1, 2, ≥3), season (m = summer, rainy, spring), and period of birth (n = 2012-2015, 2016-2019). The heritability and genetic correlations for different traits were estimated by restricted maximum likelihood (REML) method using WOMBAT software. The re(production) parameters were analyzed to assess the genetic improvement in successive generations. There was significant difference (p < 0.01) in body weights among different generations where animals belonging to latest generation showed maximum body weights indicating ideal selective breeding in the herd. Other fixed effects also had significant effects on growth performance which clearly signifies to the crucial influence of rearing environment and animal factors like parity of dams as well as litter size at birth. The overall birth weight, weaning weight, and weight at 10 months of age were 1.00 ± 0.01 kg, 7.57 ± 0.07 kg, and 81.58 ± 1.96 kg, respectively. Nevertheless, weaning weight and weight at marketing age (8 months) were 8.04 ± 0.27 kg and 75.48 ± 1.40 kg, respectively, in fourth generation, indicating higher post-weaning growth rate of 337.20 g/day. During this fourth generation, mean litter size at birth was 8.35 ± 0.43 and litter size at weaning was 7.79 ± 0.39 with lowest percentage of pre-weaning mortality (4.11 ± 1.51). The average age at first farrowing and farrowing interval was 293 ± 17.24 and 195 ± 4.78 days, respectively. There was apparently greater genetic gain in each generation except for the second generation which might be due to the environment and managemental issues that hindered reproductive performance traits and body growth. The heritability estimate for weaning weight was 0.45 and higher heritability values were observed for all the body weights except weight at third month. Genetic as well as phenotypic correlations were moderate to high among the growth traits. The heritability and genetic correlations at birth and weaning indicate the reliability of selection at an early age. The findings indicated that there is scope for improvement through genetic selection in later generations and the 75% crossbred pigs thrived well in the prevailing hot and humid tropical coastal climate. The improved germplasm could satisfy the farmers' need in a commercial venture with high economic return.

Gene effects for pod yield and horticultural traits of garden pea (Pisum sativum var. hortense L.) using Trigenic model of generation mean analysis

The inheritance of pod yield and related horticultural traits of garden pea using 12 generations was followed in three inter-varietal crosses. The non-fixable gene effects are higher than the fixable as a consequence of higher magnitude of epistatic interactions. Duplicate type of epistasis for different traits in three crosses in one or the other environment suggested to proceed with mild selection intensity in the early generations followed by intense in the later. The failure of the trigenic model for shelling (%), pods/plant, pod yield/ plant, pod length and seeds/ pod in all or in one of the crosses and environments revealed the complexity in the inheritance of these characters suggesting either presence of minor or modifier genes, and linkage rather than higher order interactions is responsible. The non-additive gene effects along with presence of non-allelic interactions for majority of the traits in respective crosses directed to adopt population improvement methods to break undesirable linkages through recombination or to defer selection in later generations following bulk pedigree or SSD methods with one or two inter-matings like recurrent selection.

Новый сорт сои Волгоградка 2

Purpose: creation of a new high-yield, mid-ripening, technological, with a high protein content soybean variety, responsive to irrigation and suitable for cultivation in crops without irrigation. Materials and methods. A collection of soybeans, numbering 2 thousand varieties of various ecological and geographical origin, including the selection of the Federal State Budgetary Scientific Institution VNIIOZ, created in 1983 and annually replenished with new genotypes. Hybridization and selection in later generations. The research was carried out on the chernozem soils of Volgograd region. Results. The original plant varieties were identified in the period 2008–2010, competitive variety trials were carried out in 2014–2016, state tests were held in 2018 and 2019. A new soybean variety called Volgogradka 2 has been included in the State Register of Varieties approved for use since 2020. In accordance with the indicators of its comparative with the standard characteristics, it stands out for its high yield (3.04 t/ha (an increase of 0.34 t/ha)), a short growing season (105 days), medium-sized (0.74 m) plants with a high attachment of lower beans (0.16 m), an increased protein content in seeds (41 %) and a gross crude protein and fat yield of 1.51 t/ha. It is drought-resistant in non-irrigated agriculture of the steppe zone of chernozem soils of Volgograd region, highly profitable and provides high-quality grain production suitable for food processing. Conclusions. A fundamentally new soybean variety with a complete type of stalk growth during the period of mass flowering, a low stem that is resistant to lodging and high attachment of lower beans, a short growing season, which contributes to a significant increase in the grain yield and quality in terms of protein content relative to standard varieties VNIIOZ 76 and VNIIOZ 86 was developed by traditional methods of breeding. The introduction of the new variety will allow expanding soybean crops in the Lower Volga region and increasing domestic soybean production.

Heritability of Waterlogging Tolerance in Wheat (Triticuma aestivum L.)

One of the most important objectives of wheat breeding is tolerance to waterlogging stress in high rainfall during critical stages and poorly drained areas. This study was conducted to estimate heritability parameters of characters associated with waterlogging tolerance by 5 x 5 complete diallel analysis in wheat (Triticum aestivum L.). The genetic material were evaluated for SPAD, CCI, MTS, Fe root and shoot contents, Mn root and shoot contents under waterlogging during Zadox Growing Stage 12 and 31 for 10 days and untreated conditions. The differences among genotypes for mostly studied characters were found to be significant under both treatments. The heritability of observed characters were controlled by both additive and dominance genes under two treatments. Also, significant reciprocals differences depends on items (c) and (d) showed the presence of maternal effects for observed characters. Consequently, the determination of maternal parents were very important for waterlogging tolerance. Moderately broad sense heritability (h2b) and low magnitude narrow sense heritability (h2n) values indicated that non-additive gene effects were more considerable on inheritance of studied characters. Therefore, the selection in later generations was recommended for waterlogging tolerant in wheat breeding programme.

Inheritance pattern of okra enation leaf curl disease among cultivated species and its relationship with biochemical parameters

Okra production in eastern India at present is severely threatened by whitefly-mediated okra enation leaf curl disease (OELCuD). Identification of resistant genotype and understanding the genetic control and biochemical relationship of OELCuD resistance are prerequisite for developing an effective breeding strategy. This study was conducted employing six populations (P1, P2, F1, F2, BC1 and BC2) of two selected (resistant x susceptible (RxS)) crosses. Associationship between severity of OELCuD and biochemical parameters of parents and hybrids at preflowering and flowering stages was studied. Segregation pattern of the genotypes in F2 generation showing OELCuD reaction of two crosses suggested that two duplicate recessive genes was operative for resistance to OELCuD. Generation mean analysis revealed involvement of both additive and nonadditive effects in the inheritance of disease resistance. Hence, postponement of selection in later generations or intermating among the selected segregates followed by one or two generations of selfing to break the undesirable linkage and allow the accumulation of favourable alleles could be suggested for the development of stable resistant genotype against this disease. Higher peroxidase activity and total phenol content in leaf emerged as reliable biochemical markers for early selection of genotype resistant to OELCuD.

Generation Mean Analysis and Molecular Markers for Salinity Tolerance during Wheat Germination and Seedling Stage

Generation mean analysis for salt tolerance in wheat was studied on P1, P2, F1, F2, BC1 and BC2 populations of three crosses. The cross-1 was between the salt tolerant Sakha-8 and sensitive Sham-8, cross-2 was between two salt tolerant varieties (Sakha-8 x Line-6) while cross-3 was between salt tolerant Line-6 and sensitive Sham-8. The genotypes were evaluated under control (0.0 mM NaCl) and salinity stress (150.0 mM NaCl) at germination and seedling stage for seven traits. The model of additive/dominance is inadequate for explaining the inheritance of all traits in control and salinity treatments in three crosses. The presence of epistasis in addition to the predominance of non-additive gene effects for all traits except SL indicated that the conventional selection procedure may not be effective enough to improve them. Therefore postponement of plant selection in later generations or the crosses between the selected segregants followed by selfing can be suggested to accumulate alleles favorable for the improvement of these traits. The molecular markers analysis revealed that only four SRAP primer combinations, three TRAP primer combinations and three SSR primer pairs generated polymorphic bands form the tested genotypes. The five polymorphic bands SRAP-2570bp, SRAP-3760bp, TRAP-1205bp, TRAP-3450bp and SSR-2215bp appeared only in the tolerant genotypes. These markers may be considered as specific markers for salt tolerance. The identified markers in this study would allow implementation of marker-assisted selection to screen wheat segregating populations for salt tolerance.

Estimation of combining ability of blackgram [Vigna mungo (L.) hepper] genotypes for grain yield and component traits

Combining ability for grain yield and its component traits were assessed utilizing line × tester method by involving three lines and six testers. For all the nine traits under study, the ratio of GCA (general combining ability) to specific combining ability (SCA) was less than unity as the relative estimates of variance due to GCA were lower than SCA, thereby reflecting the predominance of non-additive gene action. On the basis of per se performance and GCA estimates of the parents, Mash 114, RUG-46 and KU-99-21 were found to be the good general combiners for grain yield per plant. Based on SCA estimates, six hybrid combinations were found to be promising. They were: KUG 503 × KU 99–21, Mash 114 × VBN-6 and Mash 479 × RUG-46 with high × low/low × high general combiners, KUG 503 × KU 9921, Mash 479 × KU 99–21 with low × medium and KUG 503 × TU 94-2 with low × low general combiners. As the presence of high proportion of non-additive gene action was found to be pronounced, the breeding procedures such as pedigree method, bi-parental mating(s) or selection in later generations are suggested for expecting transgressive segregants on employing the promising parents and cross combinations.

Genetic studies for seed size and grain yield traits in kabuli chickpea

Seed size, determined by 100-seed weight, is an important yield component and trade value trait in kabuli chickpea. In the present investigation, the small seeded kabuli genotype ICC 16644 was crossed with four genotypes (JGK 2, KAK 2, KRIPA and ICC 17109) and F1, F2 and F3 populations were developed to study the gene action involved in seed size and other yield attributing traits. Scaling test and joint scaling test revealed the presence of epistasis for days to first flower, days to maturity, plant height, number of pods per plant, number of seeds per plant, number of seeds per pod, biological yield per plant, grain yield per plant and 100-seed weight. Additive, additive × additive and dominance × dominance effects were found to govern days to first flower. Days to maturity and plant height were under the control of both the main as well as interaction effects. Number of seeds per pod was predominantly under the control of additive and additive × additive effects. For grain yield per plant, additive and dominance × dominance effects were significant in the cross ICC 16644 × KAK 2, whereas, additive × additive effects were important in the cross ICC 16644 × JGK 2. Additive, dominance and epistatic effects influenced seed size. The study emphasized the existence of duplicate epistasis for most of the traits. To explore both additive and non-additive gene actions for phenological traits and yield traits, selection in later generations would be more effective.

Genetic analysis of various quantitative traits ininter-varietal crosses of Vigna mungo

Gene effects for 13 characters in four crosses of Vigna mungo were studied by six parameter generation mean model to determine the potential for the improvement of yield components. Scaling tests revealed inadequacy of the additive-dominance model for all the traits indicating the presence of non-allelic interactions. Duplicate gene action was observed for six characters in KUG-216 x HPBU-111, five in KUG-216 x Palampur-93, two in IPU-05-13 x Palampur-93 and one in IPU-05-13 x HPBU-111 and complementary gene action for one character each in KUG-216 x Palampur-93 and IPU-05-13 x HPBU-111 cross. Selection in later generations for duplicate gene action and early generation selection involving intermatings in F2 f or complementary gene action should be adopted for harnessing desirable recombinants.

Nature of gene action for yield and its components in mungbean (Vigna radiata)

The assessment of gene effect for some yield characters and detection of epistasis in mungbean [Vigna radiata (L.) Wilczek] was studied in four crosses involving five parents through generation mean analysis during kharif 2012 at Banaras Hindu University (BHU), Varanasi, UP. Six populations, viz. P1, P2, F1, F2, B1 and B2 of four crosses involving five parents were evaluated. The nature and magnitude of gene effects for yield and its components in mungbean was studied using six parameter model of generation mean analysis. The presence of epistasis was detected by joint scaling test and inadequacy of additive-dominance model was established except seeds/pod. Additive (d), dominance (h) gene effects along with one or more type of non-allelic interactions (i, j, l) contributed significantlytowards the inheritance of all the quantitative characters in majority of the crosses. Duplicate type of epistasis andpredominant dominance effects was also prevalent in most of the cases except in days to maturity in HUM 8 x ML 713 cross. Thus, postponement of selection in later generations may be suggested to obtain transgressive segregants for improvement of mungbean populations.