Non-additive Gene Effects Research Articles

Heterosis and Combining Ability of Pumpkin (Cucurbita moschata Duch. Ex Poir.)

Combining ability and heterosis studies carried out using half diallel method with six parents for nine characters. The analysis revealed that none of the parents was found good general combiner for all the characters consistently, however the parents P2, P3, P4 and P5 were best general combiner’s for yield and flowering traits. The gca variance for node order to first female flower open, fruit length, fruit diameter, flesh thickness, average fruit weight, fruits per plant, yield per plant and TSS was higher than the sca variance. While the days to first female flower open had lower gca value than the sca variance indicating the predominance of non-additive gene effects. Five crosses P1×P4, P3×P6, P4×P2, P5×P3 and P5×P6 found promising and should be maintained for development of future hybrid varieties for their sca effect and desirable level of heterosis.

Gene Action and Useful Heterosis in Interspesific Cotton Crosses (Gossypium hirsutum L. x Gossypium barbadense L.)

Conducted the breeding researches with interspecific cotton crosses are aimed to obtain genotypes have desired fiber characteristics like Gossypium barbadense L. and have high yields potential like Gossypium hirsutum L.. In this study, gene action and useful heterosis were investigated for fiber quality and yield traits in interspecific cotton crosses. The 12 F 1 ’s and their parents were evaluated in a Randomized Complete Block Design with four replications at the Nazilli Cotton Research Institute’s fields during 2011 and 2012 cotton growing season. Claudia, Candia, Sahin 2000, BA 308, Naz 07 and Fantom ( Gossypium hirsutum L.) were used as a female parents and Giza 45 and Avesto ( Gossypium barbadense L.) used as a male parents. Non-additive gene effects for yields, fiber strength and fiber length were greater than additive gene effects. The useful heterosis were positively significant for fiber strength and fiber length. Candia x Giza 45 hybrid was promising hybrid for all observed characters.

GENE ACTION AND HERITABILITY ESTIMATES OF QUANTITATIVE CHARACTERS AMONG LINES DERIVED FROM VARIETAL CROSSES OF SOYBEAN

<p>The knowledge of genetic action, heritability and genetic variability is useful and permits plant breeder to design efficient breeding strategies in soybean. The objectives of this study were to determine gene action, genetic variability, heritability and genetic advance of quantitative characters that could be realized through selection of segregation progenies. The F1 population and F2 progenies of six crosses among five soybean varieties were evaluated at Muneng Experimental Station, East Java during the dry season of 2014. The lines were planted in a randomized block design with four replications. The seeds of each F1 and F2 progenies and parents were planted in four rows of 3 m long, 40 cm x 20 cm plant spacing, one plant per hill. The result showed that pod number per plant, seed yield, plant yield and harvest index were found to be predominantly controlled by additive gene effects. Seed size was also controlled by additive gene effects, with small seed dominant to large seed size. Plant height was found to be controlled by both additive and nonadditive gene effects. Similarly, days to maturity was due mainly to additive and nonadditive gene effects, with earliness dominant to lateness. Days to maturity had the highest heritability estimates of 49.3%, followed by seed size (47.0%), harvest index (45.8%), and pod number per plant (45.5%). Therefore, they could be used in the selection of a high yielding soybean genotype in the F3 generation. </p>

Combining ability analysis for yield and quality traits in single cross hybrids of quality protein maize (Zea mays L.) using diallel mating design

Forty-five single-cross hybrids developed (in rabi 2014) from ten inbred lines of quality protein maize through diallel mating design along with four checks viz., Pratap QPM Hybrid- 1, Vivek QPM- 9, HQPM- 1 and HQPM-5 were evaluated in randomized block design with three replications for yield and quality traits during kharif-2014, to estimate the gca (general combining ability) of the parents and sca (specific combining ability) of hybrids considered for the development of high yielding varieties. The analysis of variance for combining ability revealed significant mean sum of squares due to gca and sca for all the traits, except mean sum of square due to gca for num-ber of grain rows per ear. Ratio of ?2 sca / ? 2 gca was greater than one for all the traits, thereby indicating the preponderance of non-additive gene effects in the expression of these traits. Inbred line P8 and P5 has been found good general combiner with highest magnitude of gca effects 10.46 and 8.89, respectively and high per se i.e. 52.33 g and 44.67 g, respectively for grain yield per plant and majority of traits. Hybrids P6xP8, P5xP8, P3xP5, P5xP7 and P1xP8 showed higher significant positive sca effects ranged from 25.66 to 34.59 along with good per se ranged from 98.00 to 107.67 g for grain yield per plant. These hybrids also exhibited significant positive sca effects for most of the yield and quality traits under study, indicating potential and may be used for exploiting hybrid vigour in in QPM hybrid breeding programmes.

Estimates of Heterosis, Combining Ability and Correlation for Yield and its Components in Bread Wheat

In order to realize the heterosis, general and specific combining ability of wheat, 28 crosses were synthesised in a 8 × 8 by using half diallel mating system, without reciprocals. Analysis of heterosis over mid parents (MP) as well as better parents (BP) and combining ability were conducted for yield and its contributing traits. The experiment was conducted in 2011–2012 and 2012–2013 seasons at the Experimental Farm of Faculty of Agriculture, Sohag University, Egypt. Heterosis was estimated for grain yield per plant revealed maximum heterosis over the mid parents (68.58% and 81.47%) for the crosses P5 × P8 and P5 × P6, followed by harvest index (53.32%), No. of spikes per plant (33.38%), biological yield per plant (30.71%), spike length (17.29%), 1000 kernel weight (15.13%),grain weight per spike (14.38%) and plant height (5.96%) for the crosses P7 × P8, P5 × P8, P4 × P5, P4 × P8, P3 × P4, P1 × P3 and P7 × P8, respectively. The maximum heterobeltiosis was recorded for grain yield per plant (82.56% and 49.3%) for the crosses P5 × P8 and P5 × P6, followed by harvest index (40.12%), biological yield per plant (28.29%), No. of spikes per plant (16.9%), 1000 kernel weight (14.05%), grain weight per spike (12.9%), spike length (9.53%) and plant height (4.76%)%) for the crosses P5 × P8, P5 × P6, P2 × P5, P3 × P4, P1 × P3, P2 × P6, and P5 × P7, respectively. The results indicated significant differences among the parents for general combining ability and crosses for specific combining ability for all studied traits, which indicated the importance of both additive and non-additive gene effects for these traits. General combining abilities were higher than those of specific combining abilities, then the GCA/SCA ratios were more than unity indicating the prepondorance of additive gene effect which have considerable roles in the inheritance of these traits. In general, The genotypes of P5 ( Sonora 64 ) confirmed to be good general combiner for plant height, No. of spikes / plant, 1000 - kernel weight, grain weight / spike, biological yield / plant, harvest index, grain yield / plant , and P4 ( Sahel 1 ) for plant height, spike length, No. of spikes / plant, 1000 - kernel weight, harvest index, grain yield / plant. The crosses P6 × P7, P5 × P6, P7 × P8, P5 × P8, P2 × P6, P4 × P8, were the best specific combiners for grain yield / plant and most of yield components. Grain yield had strong positive correlation with harvest index (0.85), biological yield per plant (0.65) and 1000 - kernel weight (0.59).

Diallel analyses of soluble sugar content in cowpea (Vigna unguiculata L. Walp.)

The content of soluble sugar in cowpea (Vigna unguiculata L. Walp.) seeds is important for their acceptability to consumers. The objective of this study was to evaluate the genetic control of soluble sugar content in cowpea using diallel analysis. For this purpose, half-diallel crosses were made among seven diverse parents. The amount of total soluble sugar was estimated by the phenol sulfuric acid reagent method and reducing sugar were measured by the DNS (3,5-dinitrosalicylic acid) reagent method. The total soluble sugar ranged from 11.12 (VYA) to 40.79mgg−1 (IT93K-693-2) with a mean of 22.31mgg−1. Reducing soluble sugar showed a mean value of 9.11mgg−1 and ranged from 13.61 (TVx 3236) to 4.98mgg−1 (Lori niébé). Diallel analysis showed that both additive and non-additive gene effects were significant in the genetic control of these traits. However, dominance variance was greater than additive variance for soluble sugar. The traits were controlled mainly by an overdominance model, suggesting the advantage of delaying selection to later generations. Soluble sugar content was found to be highly heritable, with broad-sense heritability ranging from 0.987 to 0.976. Narrow-sense heritability ranged from 0.154 to 0.422 and revealed the lower importance of additive variance. Parents and F1 hybrids differed significantly on the basis of their general and specific combining abilities, respectively. Recessive alleles had positive effects on total soluble sugar and reducing soluble sugar. These results could help cowpea breeders improve the acceptability of cowpea seeds and cowpea-based foods by appropriate selection.

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

ABSTRACTEarly-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 CKL0722, VL058014, and CZL0724 were among the best with positive GCA effects for GY across both optimal and drought stress conditions. The correlation between SCA and both genetic distance and F1 GY was significant under both drought stress and across all environments. Inbred lines with desirable GCA effects for GY and other agronomic traits and hybrids with good performance under both optimal and drought stress conditions are potential parents for development of various types of high-yielding, stress-tolerant, and early-maturing hybrids.

Estimation of Heterosis, Combining Ability and Some Genetic Parameters in Sweet Pepper

Four pure lines of pepper developing locally namely (S-1004, L-1008, K-1017 and E-1001) were used in a full diallel crossing program to evaluate the performance of those parents and their crosses, to estimate combining ability and genetic parameters for agronomic, fruit yield and its components traits. Crosses among parents were carried out in plastic house in fall season of 2012 using full diallel cross mating to produce 16 hybrids the parents, F1s and reciprocals hybrids plus hybrid check were sown in plastic house in fall season of 2013 using a R C B D design with four replicates. Data were recorded for plant height, branches number per plant, fruit number per plant, fruit diameter, fruit weight, fruit length and fruit yield per plant. The obtained results showed significant differences among the different genotypes for all traits under investigation. The hybrid (1×4) and the reciprocal hybrid (4×2) produced higher fruit number (73.90, 63.40) and fruit yield per plant (4.06, 3.28 Kg) while, the hybrid (1×3) and reciprocal hybrid (3×2) gave higher fruit length 8.02 cm. Positive and negative heterosis were found among the F1,s and reciprocals. The hybrid (1×4) and reciprocal (4×2) produced higher heterosis in fruit number (88.85, 62.02%) and fruit yield per plant (79.64, 53.99%) respectively. Significant differences were revealed in general and specific combining abilities for all studied traits. Suggesting the presence of both additive and Non-additive gene effects in the inheritance of the various studied traits. The ratio of σ²gca to σ²sca was less than unity for all studied traits, expect for fruit weight, which showed pre dominant role of non-additive gene action in the inheritance. Estimates of GCA effects showed that the best combiner parents were found to these of P1 for plant height, fruit diameter and fruit weight, while P4 for branches number, fruit number, and for fruit yield per plant, and P2 for plant height and P3 for fruit length. Estimates of SCA effects showed that the hybrid 1×2 reflected the highest value in fruit diameter (0.56) and fruit weight (1.35) and the hybrid 1×4 in fruit number (10.02) and fruit yield per plant (0.54) and 2×3 in branches number per plant (0.81) and fruit weight (1.21), and 3×4 in plant height (19.30) and fruit length (0.38). Estimates of RCA effects showed that the reciprocal hybrid 3×1 was the best for fruit weight (8.09), while the reciprocal hybrid 4×1 was the best for branches number per plant (1), fruit number (16.13), fruit length (0.55) and for fruit yield per plant (0.91) whereas 3×2 was the best for plant height branches number per plants (5.37) and fruit diameter, and 4×3 was the best for fruit number (6.03) and for fruit diameter (0.30). The values of σ² D and σ² D_r were more than that (σ² A) for all studied traits expect for fruit weight and fruit yield per plant, which were less than those for fruit diameter, fruit weight and fruit yield per plant, and this reflects the exceeded one for the value of average dominance degree for all studied traits in both diallel and reciprocal crosses expect for fruit diameter in reciprocal crosses which was less than one. As for broad sense heritability it was high for all studied traits in both diallel and reciprocal crosses, while, the values narrow of sense heritability were low in diallel and reciprocal crosses for all studied traits except for fruit weight, and fruit diameter were high value in reciprocal crosses (0.81) and (0.52) respectively. It was concluded that two inbred (p1 and p4) could be used in a breeding program to develop new versions of high fruit yield per plant and high SCA to produce better fruit yield hybrids and most studied traits were under over dominance gene action. This showed that developing elite hybrids, and most studied traits were under over dominance gene action. This showed that developing elite hybrids were the best method for improving pepper fruit yield per plant in pepper plant.

Genetic analysis of important antioxidant compounds in cabbage (Brassiaca oleracea var. capitata L.)

ABSTRACTThe paucity of research on development of antioxidant-rich hybrids in cabbage by utilizing combining ability estimates, gene action, and heterosis motivated us to undertake this study. We made 60 crosses between 5 cytoplasmic male-sterile lines and 12 male-fertile testers during the summer of 2015, as per the line × tester design. The seedlings of all the parents and 60 F1 crosses, along with three checks, were transplanted during the Rabi (winter) season of 2015–2016 and evaluated using a randomized complete-block design. Combining ability, gene action, and heterosis were determined for different antioxidant compounds. Experimental results revealed that the range of cupric ion reducing antioxidant capacity (CUPRAC) [parents = 1.26–7.33 and hybrids = 0.04–6.54 μmol trolox/g], ferric reducing ability of plasma (FRAP) [parents = 1.65–4.76 and hybrids = 0.16–4.67 μmol trolox/g], β-carotene (parents = 0.44–2.29 and hybrids = 0.04–1.89 μg/100 g), and chlorophyll-a (parents = 0.71–4.08 and hybrids = 0.19–3.08 mg/g f.w.) for hybrids was lower than that of the parents because of outbreeding depression. The parental lines 6A, 208A, 83-5-8, and Sel-5-83-6 were found to be good general combiners for most of the antioxidant compounds studied. Based on the mean performance, specific combining ability effects and heterosis, five hybrid combinations viz., 9A × KIRC-8 for CUPRAC and FRAP; 208A × C-122 for ascorbic acid; 6A × Chhaki-2 for total carotenoids and β-carotene; 831A × Chhaki-2 for chlorophyll-a; and 6A × 83-5-8 for chlorophyll-b and total chlorophyll content, were most promising. The ratio of general combining ability (GCA) and specific combining ability (SCA) variances, i.e., [2 σ2g/(2σ2g + σ2s)], which reflects the relative importance of GCA versus SCA, was less than unity for different antioxidant compounds, which implied that for these traits, nonadditive gene effects were more important than additive effects. The numerical values of range for contribution of lines × testers interaction for different traits (41.47–70.18%) were found to be higher than the individual contribution of lines (11.24–47.22%) and testers (8.31–21.76%). Hence, heterosis could be exploited for developing antioxidant-rich hybrid cabbage.

Combining Ability and Gene Action of Tropical Maize (Zea mays L.) Inbred Lines under Low and High Nitrogen Conditions

This study was conducted to determine combining ability and gene action in elite maize inbred lines under low and high soil nitrogen conditions for hybrid breeding. Forty two tropical inbred lines (three testers and 39 lines) were crossed using line × tester mating design. The resulting 117 F1 hybrids, along with 4 hybrids used as checks, were evaluated using an 11 × 11 lattice design with two replications for grain yield and yield related traits during the 2012 and 2013 cropping seasons at two sites (Mbalmayo and Nkolbisson). Results revealed predominant additive gene effect under high soil nitrogen (N) conditions. Non-additive gene effect influenced grain yield under low soil and thus could be exploited for hybrid development. Under high N conditions inbred lines CLYN246, J16-1, CLWN201, TL-11-A-1642-5, CLQRCWQ26 and 1368 were good general combiners. Lines CML 343, ATP S6 20-Y-1, CLWN201, 1368, ATP S9 30 Y-1 and CLQRCWQ26 were good general combiners for grain yield under low N. They could be used to develop low N tolerant varieties. Different single cross hybrid combinations were identified for high grain yields under both low and high N conditions. The selected lines and single cross hybrids are a useful source of valuable genetic material for future maize hybrid breeding or direct production under low N.

Combining ability and genetic analysis of fruit and leaf yield in gboma eggplant

Gboma eggplant (Solanum macrocapon L.) of the family Solanaceae is an important fruit and leafy indigenous vegetable in Africa. Despite the numerous nutritional, medicinal and economic benefits derived from the crop, little is known about the genetic parameters governing the inheritance and combining ability of the yield components. Thus, a study was conducted to investigate genetic information on the relevant yield components of the crop. Results showed significant mean squares for General Combining Ability, Specific Combining Ability effects for number of leaves per plant, fruit width and plant height, indicating the combining effect of additive, non-additive and maternal effects for expression for those traits. Conversely, significant (P< 0.05) SCA effects for number of branches per plant, leaf length, leaf width and fresh leaf weight indicated the preponderance of non-additive gene effect. GCA/SCA ratios for the various traits indicated that the relative contribution of additive to non-additive effects varied widely from trait to trait. Significant reciprocal effects for most of the traits were an indication that cytoplasmic or maternal gene effects played a major role in modifying the inheritance of the yield parameters, and that the choice of the maternal parent is relevant in breeding for these traits. Estimated GCA effect among the parents revealed that CAGRIC 03 has a breeding value for number of branches, plant height, fruit length, leaf length and fresh leaf weight, which makes it a valuable material for development of improved varieties. CAGRIC 01 was the promising combiner to increase fruit weight and number of leaves per plant. Hybrid P1xP2 was the best specific combiner to increase fruit width, leaf width and fruit width. High heritability estimates for most of the traits indicate that genetic variation was higher than the environmental variation in the study.Keywords: African eggplant, heritability, Solanum macrocapon

Genetic analysis of heat stress tolerance in Indian mustard (Brassica juncea)

A set of 53 Indian mustard [Brassica juncea (L) Czern and Coss] genotypes were evaluated for genetic variability and correlation for yield and physiological characters during the rabi season of 2012-13 and 2013-14 under heat stress (early sown) and normal (timely sown) environmental conditions. The study was undertaken to generate genetic information for seed yield/plant (g), population survival (%) at 10 and 25 days after sowing (DAS), membrane stability index (MSI) (%), excised-leaf water loss (%), relative water content (%), water retention capacity of leaves (%), 1000-seed weight (g) and oil content (%). Moreover, magnitude of relationships among these characters were also measured. Significant differences were observed for all the characters among the genotypes, except 1000-seed weight, which revealed the presence of sufficient variability for the characters. The phenotypic coefficient of variation (PCV) for all the characters were found to be higher than genotypic coefficient of variation (GCV). High PCV for MSI, seed yield/plant and population survival (PS) at 25 DAS obtained in the study showed the significance of additive genes. High heritability estimates coupled with high to moderate genetic advance as per cent of mean was recorded for PS at 25 DAS, WRCL and RWC indicating the significance of additive genes and the role of additive gene action for the inheritance of these characters. Moreover, it also became evident that selection may be performed for the improvement in these characters. Among the different characters oil content recorded low heritability estimates along with low genetic advance. Low heritability estimate for oil content indicated the predominance of non-additive gene effects for this trait and thus the scope of its improvement through selection might be very low. However, it may be improved through hybridization. Character association studies revealed that seed yield/plant and RWC are highly positive correlated (r=0.407**) which could be considered as one of the important selection criteria in the improvement of seed yield under heat stress situation. Adequate genetic variability was present within available Indian mustard genotypes to allow breeding improvement of seed yield and physiological characters.

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

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.

Evaluation and Classification of Maize Inbred Lines by Line X Tester Analysis for Grain Yield, Late Wilt and Downy Mildew Resistance

Twenty five new yellow inbred lines of maize were mated to two inbred lines(Sk11 and Sk2) as testers during 2014 season. The resulting 50 hybrids and the check hybrid SC168 were evaluated in three trials during 2015 season. The first for grain yield (t/ha) was conducted at Sakha and Sids research stations, the second and the third for late wilt and downy mildew resistance, each one was performed in two trials under two nitrogen levels(143 and 286 kg N/ha), respectively in two separate disease nurseries at Sakha Research Station. The first nursery under artificial soil inoculation by late wilt disease and the second nursery under artificial infection by downy mildew disease. The results were combined analysed across the two locations in the first trial and across two nitrogen levels in the second and third trials. Mean squares due to lines, testers and their interaction were significant for all traits, except for the interaction between lines x testers for late wilt resistance. The interactions lines, testers and lines x testers with locations were significant for grain yield, while their interactions with nitrogen levels were not significant for late wilt and downy mildew resistance. The non-additive gene effects were the most important component controlling the inheritance of all studied traits. The best inbred line for general combining ability effects was L6 for grain yield and downy mildew resistance and L10 for late wilt resistance. The best hybrid for specific combining ability effects was L22 x Sk2 for gain yield, L20 x Sk2 for late wilt resistance and L13 x Sk2 for downy mildew resistance. The hybrid L6 x Sk11 had high grain yield (>check) and high resistance to both late wilt and downy mildew. The 25 inbred lines were classified into the following two heterotic groups using HSGCA: for grain yield: group 1 (SK11): L9, L10, L11, L12, L15, L19, L22 and L23 and group 2 (SK2): L1, L2, L3, L5, L14, L16, L17, L21, L24 and L25 , for late wilt resistance: group 1 (SK11): L3, L15, L16, L19, L20, L21 and L25 and group 2 (SK2): L1, L4, L6, L7, L11, L12, L13 and L14. For downy mildew resistance: group 1 (SK11): L1, L2, L13, L15 and L21 and group 2 (SK2): L3, L4, L7, L12, L14, L17 and L25. These groups could be used in breeding programs for selecting the best parents in making crosses.

General and specific combining ability analysis for yield and yield contributing characters in groundnut (Arachis hypogaea L.)

The present study was undertaken to analyse the nature of gene action involved in the inheritance of seed yield and its components using F1s of 7 parents half- diallel cross. The 7 parents and 21 hybrids were planted in a randomized block design with three replications during summer 2016. General combining ability and specific combining ability were estimated for 12 characters viz.. days to first flowering, days to 50% flowering, days to maturity, plant height, number of pods per plant, pod length, pod yield per plant, shelling %, kernel yield per plant, 100 kernel weight, oil content and haulm yield per plant. The genetic analysis was done following Griffing’s Method II with Model I (1956). Analysis of variance for combining ability revealed that GCA and SCA were highly significant for all the characters under study in F1 generation. This suggested the importance of both additive and non-additive gene effects in the inheritance of traits under study. However, the estimates of variance due to SCA is greater than variance due to GCA for all the characters involved in the study indicating the predominance of non-additive gene action in controlling the expression of all the traits involved in the study.

Genetic analysis of seed yield and yield attributes in Indian mustard (Brassica juncea (L.) Czern and Coss.)

An experiment was conducted during winter seasons of 2005-06 and 2006-07 to study the nature and magnitude of gene effects involved in the genetic control of seed yield and yield attributing traits in Indian mustard [Brassica juncea (L.) Czern and Coss.] through generation mean analysis. Two crosses namely; RH 0115 x EC 126745 and RH 0120 x EC 126745 were grown in a randomized block design under normal and late sown conditions. In six parameter model additive gene effects were significant for days to maturity, number of primary and secondary branches per plant, number of seeds per siliqua and oil content. Both additive and non-additive gene effects were found to be significant for main raceme length, number of siliquae on main raceme, seed yield per plant and 1000-seed weight. Thus on the basis of above study it is advocated that the breeding methods which exploit both the components of genetic variation may be useful for further genetic amelioration. For the improvement of seed yield and its component characters; reciprocal recurrent selection or diallel selective mating would be helpful.

Combining ability for yield and yield attributing characters in brinjal (Solanum melongena L.)

A field experiment was carried out with a view to estimate, combining ability and gene effects in brinjal ( Solanum melongena L.). The experimental material comprised of 37 genotypes including 8 parents, 28 hybrids and one standard check (Surati Ravaiya) was laid out in Randomized Block Design with three replications at Regional Horticultural Research Station (R.H.R.S.), Navsari Agricultural University, Navsari, Gujarat during Rabi 2015-16. Combining ability analysis revealed that both additive as well as non-additive gene effects were important in the inheritance of all the traits studied. However, magnitude of variances due to sca were comparatively larger than those of gca for most of the economic traits indicated preponderance of non-additive gene action. Among the parents, JBGR-1, NSR-1 and JBL-08-8 were good general combiners for majority of the traits. The crosses viz., AB-09-1 × AB-12-10, AB-09-1 × AB-08-5, AB-08-5 × JBL-08-8 and GJB-3 × AB-12-10 showed higher order sca effects in addition to performance for fruit yield and its component characters.

Inheritance of yield and yield components in soybean (Glycine max (L.) Merrill.)

The present investigation was undertaken to study the genetics of yield and yield components in soybean through generation mean analysis. Three crosses viz., MACS-450 × Monetta, DS-9712 × Kalitur and MACS-450 × Kalitur were made involving four parents during kharif 2013 to study the gene action for ten characters in soybean. Six generations (P 1 , P 2 , F 1 , F 2 , B 1 and B 2 ) were obtained by intermating diverse parents. Dominant gene action was observed in the inheritance of yield and yield contributing characters viz ., number of pod per plant, 100 seed weight and yield per plant. Both additive and non-additive gene effects were significantly involved in the expression of number of pods per plant (cross II), number of clusters per plant (cross II and III) and all three crosses expressed duplicate epistasis for yield per plant. Bi-parental mating design may be used to improve these characters. Complementary epistasis was observed for the cross Kalitur × DS-9712 for plant height (cm) and cross Kalitur × MACS 450 for number of pods per plant, which suggested that the selection will be practiced in F 3 generation onwards for improvement of these characters.

Line × Tester Analysis of Tropical High Land Maize (<i>Zea mays</i> L.) Inbred Lines Top Crossed with Three East African Maize Populations

Maize breeding efforts to generate high yielding and adaptive cultivars have recently been given emphasis by national maize breeding program. In Ethiopia, the maize production system is mainly dominated by subsistence farmers where their production is below average. The objectives of this study were to determine the combining ability between lines and testers, and to evaluate the performance of crosses (hybrids) and parents for grain yield and yield component traits. Twenty-seven inbred lines were generated by crossing nine female lines (L1-L9) and three male testers (T1-T3) using line × tester mating system at International Maize and Wheat Improvement Center (CIMMYT), East African high land maize improvement program. The inbred lines along with parents were evaluated in randomized complete block design with two replications at three locations (Ambo, Kulumsa and Haramaya). Significant differences were observed among genotypes for all ten traits considered. Eight crosses (L1 × T2, L1 × T3, L3 × T3, L8 × T1, L4 × T2, L9 × T1, L2 × T1, and L2 × T2) had higher yield performance compared to other crosses across environments. Significant mean square differences were found across locations for general combining ability (GCA) due to lines for all traits except for number of kernel rows per ear, whereas GCA due to testers were significant only for grain yield, ear length and 1000-seed weight. Significant mean square due to GCA × Loc (both for lines and testers) was found for days to maturity (38.71*), 1000-seed weight (4582.36**) and grain yield (2756777**), while significant SCA × Loc interaction was found for all traits except number of kernel rows per ear (1.07), ear length (0.79) and ear diameter (0.12), suggesting that the importance of additive and non-additive gene effects in controlling these characters.

Heterosis, inbreeding depression and heritability for yield and yield components in cowpea

A field experiment was undertaken with a view to know the extent of heterosis, inbreeding depression, heritability and genetic advance for yield and yield components in cowpea [Vigna unguiculata (L.) Walp.]. Six generations viz., P1, P2, F1, F2, BC1 and BC2 of eight crosses involving sixteen diversified cultivars of cowpea [Vigna unguiculata (L.) Walp.] were evaluated for yield and its traits. Significant positive heterosis for seed yield per plant and its related traits followed by significant inbreeding depression indicated major role of non-additive gene actions in the inheritance of seed yield per plant and its attributes. For seed yield per plant top three heterotic crosses were cross II (GC-4 x Pusa komal) followed by cross VIII (Cowpea sabra x Waghai krushi) and cross I (GC-3 x Pusa falguni). High heritability coupled with high genetic advance for cross I (GC-3 x Pusa falguni) and high heritability coupled with moderate genetic advance for cross II (GC-4 x Pusa komal), cross III (GC-5 x Anand cowpea), cross IV (W-203-3 x W-3-1) and cross V (W-502-2 x W-3-2) for seed yield per plant indicated heritability was due to additive gene effects. Involvement of both additive and non-additive gene effects suggested that it would be desirable to follow cyclic method of breeding.