Specific Combining Ability Variance Research Articles

Combining Ability, Heterosis, and Heritability of Storage Root Dry Matter, Beta-Carotene, and Yield-related Traits in Sweetpotato

Orange-fleshed sweetpotato (OFSP) is an effective, low-priced, and sustainable source of β-carotene (provitamin A). However, most OFSP varieties have low storage root dry matter content (DMC), which influences their acceptance by small-scale farmers and hence needs to be improved. The objective of the study was to determine the combining ability, type of gene action, heterosis and heritability of storage root DMC, β-carotene content, and yield-related traits of selected sweetpotato clones for further evaluation and breeding. Crosses were conducted using a 7 × 7 half-diallel mating design and a total of 28 genotypes (seven parents and 21 crosses) were evaluated at four locations in Ethiopia using a 7 × 4 alpha lattice design with two replications. The performance of the genotypes was significantly different (P < 0.01) across the four locations for storage root DMC, β-carotene content, sweetpotato virus disease (SPVD) reaction, storage root yield, and harvest index (HI). The general combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P < 0.01) for all traits except the SCA effect of storage root DMC. The GCA to SCA variance ratios were 0.96, 0.94, 0.74, 0.96, and 0.97 for storage root DMC, β-carotene content, SPVD, fresh storage root yield, and HI, respectively, indicating that the inheritance of these traits was controlled mainly by additive genes. Progenies of crosses involving Ukerewe × Ejumula, Ukerewe × Pipi, Resisto × Pipi, and Ejumula × Pipi exhibited high levels of positive heterosis for storage root DMC. Similarly, progenies of crosses including Resisto × Pipi and Resisto × Ogansagan had higher positive heterosis for fresh storage root yield, reflecting the breeding value of these parents. Relatively high narrow sense heritability (h2) was obtained for β-carotene content (79.8%) and HI (48.6%). However, the h2 estimates of storage root DMC, SPVD, and fresh storage root yield were relatively low at 19.0%, 14.9%, and 20.4%, respectively. Crosses with high β-carotene content such as Ukerewe × Resisto, Resisto × Ogansagan, Eumula × Pipi, and NASPOT 1 × Temesgen exhibited high storage root DMC. These families also had medium-to-high mean fresh storage root yield. Therefore, progenies derived from these families are good candidates to develop improved OFSP varieties with high storage root DMC.

Assessment of Heritable Variation and Best Combining Genotypes for Grain Yield and Its Attributes in Bread Wheat

Grain yield in wheat is the resultant of several plant attributes. It is very important to assess heritable variation involved in the inheritance of these attributes in addition to find the best combining genotypes. For this purpose, the present study involving 5 × 5 full diallel analysis was performed. Twenty F1 hybrids along with their parents (9797, 9801, 9802, Chakwal-50 and Chakwal-86) were planted in field using randomized complete block design (RCBD) with three replications in the research area of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad during 2015-2016. Plant characters like plant height, flag leaf area, spike length, No. of fertile tillers per plant, No. of grains per spike, No. of spikelets per spike, 1000 grain weight and grain yield per plant were studied in this experiment. Mean squares due to general combining ability (GCA) were highly significant for all the traits except for spike length for which GCA effects were significant. Mean squares due to specific combining ability (SCA) and reciprocal combining ability (RCA) were highly significant for all the characters studied. GCA variance was higher than the SCA variance for spike length and No. of grains per spike exhibiting the predominant role of additive genetic variation in the inheritance of these traits. However, for the characters like plant height, flag leaf area, No. of fertile tillers per plant, No. of spikelets per spike, 1000 grain weight and grain yield per plant, the value of SCA variance was higher than the value of GCA variance showing non additive gene action for these traits. The variety Chakwal-50 proved to be the best general combiner for plant height, spike length, No. of spikelets per spike, No. of grains per spike and grain yield per plant. The cross, 9802 × Chakwal-86 was the best specific combination for grain yield and most of the yield attributes. The good general and specific combiners are important breeding resources for the initiation of future wheat breeding programmes aimed at enhancement of grain yield in bread wheat.

Genetic analysis of tropical maize inbred lines for resistance to maize lethal necrosis disease

Maize lethal necrosis (MLN) disease is a recent outbreak in eastern Africa and has emerged as a significant threat to maize production in the region. The disease is caused by the co-infection of Maize chlorotic mottle virus and any member of potyviridae family. A total of 28 maize inbred lines with varying levels of tolerance to MLN were crossed in a half-diallel mating design, and the resulting 340 F1 crosses and four commercial checks were evaluated under MLN artificial inoculation at Naivasha, Kenya in 2015 and 2016 using an alpha lattice design with two replications. The objectives of the study were to (i) investigate the magnitude of general combining ability variance (σGCA2) and specific combining ability variance (σSCA2) and their interaction with years; (ii) evaluate the efficiencies of GCA based prediction and hybrid performance by means of a cross-validation procedure; (iii) estimate trait correlations in the hybrids; and (iv) identify the MLN tolerant single cross hybrids to be used as female parents for three-way cross hybrids. Results of the combined analysis of variance revealed that both GCA and SCA effects were significant (P < 0.05) for all traits except for ear rot. For MLN scores at early and late stages, GCA effects were 2.5–3.5 times higher than SCA effects indicating that additive gene action is more important than non-additive gene action. The GCA based prediction efficiency for MLN resistance and grain yield accounted for 67–90% of the variations in the hybrid performance suggesting that GCA-based prediction can be proposed to predict MLN resistance and grain yield prior to field evaluation. Three parents, CKDHL120918, CML550, and CKLTI0227 with significant GCA effects for GY (0.61–1.21; P < 0.05) were the most resistant to MLN. Hybrids “CKLTI0227 × CML550”, “CKDHL120918 × CKLTI0138”, and “CKDHL120918 × CKLTI0136” ranked among the best performing hybrids with grain yield of 6.0–6.6 t/ha compared with mean yield of commercial check hybrids (0.6 t/ha). The MLN tolerant inbred lines and single cross hybrids identified in this study could be used to improve MLN tolerance in both public and private sector maize breeding programs in eastern Africa.

COMBINING ABILITY FOR FLOWERING AND YIELD TRAITS OF JATROPHA (Jatropha curcas L)

An experiment was conducted with 6 × 6 half diallel population to determine the combining ability for yield characters in Jatropha. Combining ability analysis revealed that both general and specific combining ability variances were significant for all the characters studied. GCA was observed to be higher in magnitude for majority of the characters except number of inflorescence per plant indicating that these characters were predominantly under additive genetic control. The non additive components of variance were also involved in the inheritance of number of inflorescence per plant. The parent P1 was the best general combiner for most of the traits including earliness and seed yield per plant and P5 was the poor general combiner for all the traits except hundred seed weight. Higher negative SCA effect was found in the cross combination P1×P3 for earliness and positive effect for seed yield per plant. Finally, it can be concluded that both additive and dominant genetic components are important for earliness and seed yield in Jatropha. The cross combination P1×P2, P1×P3, P2×P5 and P4×P6 is found promising for earliness and seed yield per plant. These combinations could be selected for the development of hybrid varieties in Jatropha.

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

Six parental genotypes and their thirty F1 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.

Studies on Combining Ability for Yield and Yield Attributes in Groundnut (Arachis hypogaea L.)

The specific combining ability variances was much greater than those of general combining ability variances for all the characters except pod yield per plant, which indicated the preponderance of non additive gene action. Among the lines, Prasuna had shown significant positive gca effect for kernel yield per plant. Narayani was found to be good combiner for pod yield per plant as it showed significant and positive gca effect. Among the testers, ICGV-91114 was found to be superior as it showed significant and positive gca effect for number of mature pods per plant, shelling per cent, kernel yield per plant and pod yield per plant. These parents could be used in breeding programme for yield improvement through pedigree breeding. The best specific cross Greeshma×Dharani was found to be desirable for kernel yield per plant. The cross Narayani×Dharani had showed significant sca effect for pod yield per plant. These crosses would be used for further selection to obtain high yielding seggregants.

COMBINING ABILITY, HETEROSIS AND GENE ACTION USING (LINE × TESTER) ANALYSIS IN CORN

A field experiment was conducted at the Field Crops Research Station of State Board of Agricultural Research at Abu Ghraib in spring 2015. Seven inbred lines of maize (IK8, ZP, W13R, H.S, IK58, ABS 5, ZP607) were used in this study, using Line x Tester analysis, to produced twenty F1 crosses. The parents and crosses were grown in fall season of 2015 using RCBD with three replicates to determine heterosis and general, specific combining ability effects and gene action. Significant differences were found among parental lines and their crosses for all the traits. The result were showed that the cross (IK8× IK58) gave the highest hybrid vigor in grain yield (42.46%) and produced highest grain yield 214.7 gm.plant-1. The values of specific combining ability variance for all the traits revealed superior to the variance of general combining ability. The dominance genetic variance more important than additive variance, the narrow sense heritability for ear length very low (2.5%), white was highest (36.42%). The result indicate that some inbred lines could be used in a breeding program to develop new versions of high yield hybrids and most studied traits were under dominance and over dominance gene action.

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

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.

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

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 1000-grain weight; ‘Dzherelo’, ‘Granal’, and ‘Vitrazh’ for spike length; ‘Dzherelo’ and ‘Maliovnychyy’ for spikelet number per spike; ‘Dzherelo’, ‘Badioryy’ 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 “1000-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, 1000-grain weight). Strong SCA effects were the most numerous for the trait “1000-grain weight.”

High accuracy of predicting hybrid performance of Fusarium head blight resistance by mid-parent values in wheat.

Mid-parent values of Fusarium head blight (FHB) resistance tested across several locations are a good predictor of hybrid performance caused by a preponderance of additive gene action in wheat. Hybrid breeding is intensively discussed as one solution to boost yield and yield stability including an enhanced biotic stress resistance. Our objectives were to investigate (1) the heterosis for Fusarium head blight (FHB) resistance, (2) the importance of general (GCA) vs. specific combining ability (SCA) for FHB resistance, and (3) the possibility to predict the FHB resistance of the hybrids by the parental means. We re-analyzed phenotypic data of a large population comprising 1604 hybrids and their 120 female and 15 male parental lines evaluated in inoculation trials across seven environments. Mid-parent heterosis of FHB severity averaged -9%, with a range from -36 to +35%. Mean better parent heterosis was 2% and 78 of the hybrids significantly (P<0.05) outperformed the best commercial check variety included in our study. FHB resistance was not correlated with grain yield in healthy status for lines (r=0.01) and hybrids (r=0.09, P<0.01). While a preponderance of GCA variance (P<0.01) was found, SCA variance was not significantly different from zero. Accuracy to predict hybrid performance of FHB severity based on mid-parent values and on GCA effects was high (r=0.70 and 0.86, respectively; P<0.01). Similarly, line per se performance and GCA effects were significantly correlated (r=0.77; P<0.01). The substantial level of mid-parent heterosis in the desired direction of decreased susceptibility and the negligible better parent heterosis suggest that hybrids are an attractive alternative variety type to improve FHB resistance.

Estimates of Combining Ability for some Quantitative Traits During Different Sowing Dates in Rice

Half diallel crosses among six genotypes of rice (Oryza sativa L.) as well as their parents were cultivated in a randomized complete block design to investigate general combining ability (GCA) effects of parents and specific combining ability (SCA) effects of crosses during different sowing dates. Analysis of variance in diallel analysis exhibited highly significant (P < 0.01) for most studied traits at the four sowing dates. The mean squares due to GCA and SCA were also highly significant for all studied traits during the four sowing dates, indicated that the importance of the both additive and dominance gene actions for these traits. Variances due to GCA were greater than these due to SCA for days to heading, panicle length and panicle weight traits during the second, third and fourth sowing dates and for grain yield/plant during the first and second sowing dates. However, the values of SCA variances were higher than the values of GCA variances for the other studied traits through the other studied sowing dates. Results showed significant differences among all the crosses means and their respective parental values for all examined traits at the four sowing dates. The most of parents and their F1 crosses were displayed significant or highly significant GCA and SCA effects either negative for days to heading or positive for the other studied traits at the four sowing dates. Concerning the four sowing dates, the variety Giza 179 was the best general combiner for days to heading, grain yield/plant, number of panicles/plant and 1000-grain weight traits while, the genotype CT 9882 was the best general combiner for panicle length and panicle weight traits. The best specific combinations during the four sowing dates were the cross Giza 178 x CT 9882 for days to heading and number of panicles/plant traits, the crosses Giza 178 x Sakha 105, Giza 178 x Sakha 106 and Giza 178 x Giza 179 for grain yield/plant and 1000-grain weight traits and the cross Giza 179 x CT 9882 for panicle weight and panicle length traits. Cluster analysis based on all studied traits resulted into two clusters from genotypes through all sowing dates in rice. The first cluster included the two exotic genotypes (CT9882 and CT 9506). The second cluster containing four genotypes, further divided into two sub clusters. Sub cluster-I containing the most earlier rice genotypes (Sakha105 and Sakha106). The Egyptian indica rice varieties (Giza178 and Giza179) were grouped together. The results of cluster analysis suggested that there is genetic diversity among the six genotypes for all studied traits. Hybridization among these genotypes in the two groups provided more possibility to having more genetic diversity and could be used in breeding programs to achieve maximum heterosis as well as earliness and yield improvement in rice. Generally, the parents involved in the previous combinations and the best crosses could be use in initiated the breeding program for growing at early sowing dates (first and second sowing dates) of rice crop in the north of Egypt.

Combining ability and heterosis on yield and its component traits in maize (Zea mays L.)

Combining ability and heterosis were studied in a 7×7 half diallel cross in maize for grain yield and yield contributing characters. Significant general and specific combining ability variances were observed for all the characters studied. The significant estimates of GCA and SCA variances suggested the importance of both additive and non-additive gene actions for the expression studied traits. In these studies, variances due to SCA were higher than GCA for all charactesr, which revealed the predominance of non additive gene action (dominance and epistasis) for controlling these traits. Parents P1 and P4 were excellent general combiner for days to tasseling and silking while P1 and P5 for early maturity. P4 for short height and, P4 and P7 for higher thousand kernel weight. The parents P4 and P6 having good combining abilities for yield. Heterosis estimation was carried out using two commercial varieties NK40 and 900MG. When standard commercial check NK40 was used, the percent heterosis for kernel yield varied from -51.39 to 12.53%. Among the 21 F1s, 3crosses exhibited significant positive heterosis for kernel yield. The highest heterosis was exhibited by the cross P4×P6 (12.43%), P6×P7 (10.89%) and P2×P3 (9.87%) respectively. Compared with 900MG as check, the percent heterosis for kernel yield varied from -53.73 to 7.01%. Among the 21 F1s, none of the crosses exhibited significant positive heterosis for kernel yield. The highest heterosis were exhibited by the crosses P4×P6 (7.01%), P6 x P7 (5.55%) and P2×P3 (4.57%). The crosses showed significant positive SCA values could be used for variety development after verifying them across the agro-ecological zones of Bangladesh.Bangladesh J. Agril. Res. 41(3): 565-577, September 2016

A multi-environment trials diallel analysis provides insights on the inheritance of fumonisin contamination resistance in tropical maize

In maize, the fungi that cause Fusarium ear rot result not only in decreased grain yield and quality, but also grain contamination by fumonisin. This study investigated the inheritance of fumonisin contamination resistance (FCR) in tropical maize, based on a multi-environment trials diallel analysis via mixed models. For this purpose, based on 13 inbred lines, single-cross hybrids were created and assessed in three environments. A mixed model diallel joint analysis across environments was performed, considering the existence of environment-specific variances and correlations between pairs of environments for general combining ability (GCA) and specific combining ability (SCA) effects, and additive genomic relationship between inbred lines for the prediction of GCA and SCA. For all environments, the SCA variance had a higher magnitude than the GCA variance, indicating a predominance of the dominance effects underlying FCR in tropical maize. Moreover, the proportion of the variance among single-cross hybrids that was due to GCA varied from 16 to 22 % across environments, suggesting that SCA is important to predict the hybrids performance. Through modeling variance–covariance structures for GCA and SCA, it was possible to observe that the GCA effects were stable, whereas the SCA effects were specific for each environment. Therefore, these results suggest that the selection of the best parents for the development of new inbred lines can be carried out through the average performance across the evaluated environments. Due to the importance of SCA effects and their complex interaction with environments, the selection of superior hybrids should be performed into specific environments.

COMBINING ABILITY FOR YIELD AND COMPONENT CHARACTERS IN WHITE GRAIN QUALITY PROTEIN MAIZE

Combining ability for yield and yield components were carried out in a 8×8 diallel cross of white grain quality protein maize (QPM) to determine the general combining ability (GCA) of the parents and specific combining ability (SCA) of the crosses. Significant mean sum of squares due to GCA and SCA were observed for all the characters studied. Higher magnitude of SCA variance than GCA variance clearly indicated the predominance of non-additive gene action for all the traits. The parental lines P4, P7 and Q6 were found to be the best general combiner for yield components and these parents could be used as donor parents in hybridization to improve traits like days to tasseling, days to silking, plant height, ear height, ear length, ear diameter, grains per ear and 1000 grain weight by accumulation of favorable genes. The significant positive SCA along with high mean yield, the crosses Q5 × P7, P7× Q6 and P7× Q2 could be used for commercial variety development, after verifying their performance over locations.

Combining Ability of Parents and Hybrids for Sugar Yield and Its Attributing Traits in Sweet Sorghum [Sorghum bicolor (L.) Moench

An investigation was carried out to assess the combining ability and nature of gene action in respect of sugar yield and its attributing traits in 25 new hybrids of sweet sorghum developed by crossing five (5) high-sugar lines with five (5) low-sugar lines in a North Carolina II mating design and grown in alpha lattice with two replications during long rains season of 2014 in western Kenya. The variance among the lines in respect of their general combining ability was highly significant for brix and plant height at 90 days. Specific combining ability variance was relatively higher in magnitude for grain weight and plant height indicating predominance of non-additive gene action in the genetic control of these traits. GADAM, MALON and PAISANO among the females and IESV93046, IS2331 and NTJ 2 among males were identified as good general combiners indicating their ability in transmitting additive genes in the desirable direction to their progenies. The best hybrids for total biomass and total sugar content were GADAM × IESV93046, GADAM × IS2331 and MALON × IS2331, and after adequate testing in many locations across the target production environments these hybrids can be recommended for commercial exploitation for ethanol production.

Genetic studies for seed yield and its components in safflower (Carthamus tinctorius L.)

General and specific combining ability variances and effects for ten characters related to yield and its contributing traits in safflower were studied using Line x Tester matting design in thirty CMS based hybrids involving 15 lines and two testers along with two checks (AKS 207 & PKV Pink). Combining ability analysis indicated the predominance of non-additive gene action for all the traits under study except seed volume weight for which both additive and non-additive gene actions were found equally important. The parents viz., GMU 2952, GMU 5609 and GMU 3420 among the males and AKS CMS 2A among the females were found good general combiners for seed yield and most of the yield contributing traits whereas for oil content GMU 3420, GMU 3715 and AKS CMS 2A were found good general combiners. For seed yield per plant the cross AKS CMS 3A x GMU 3638 was found significantly superior in addition to number of seeds per capsule. Whereas, AKS CMS 2A x GMU 2900 for seed volume weight, AKS CMS 2A x GMU 3923 for 100 seed weight, AKS CMS 2A x AKS 207 for number of seeds per capsule, AKS CMS 2A x GMU 322 for number of capsule per plant, AKS CMS 3A x GMU 3420 for number of primary branches per plant were identified as good cross combinations. Desired and fertile segregates may be isolated from segregating material of these crosses in the advanced generations if crosses are effected again by using ‘B’ lines of CMS based females along with same male parents in concerned crosses as these crosses involved CMS line as female parent. Further, early generation segregates may be intermated with each other to break undesirable linkages and obtain desirable segregates for seed yield and its contributing traits due to predominance of SCA variance for almost all the traits.

Gene Action Studies in the Inheritance of Economic Traits in Diallel Cross of Lentil (&amp;lt;i&amp;gt;Lens culinaris&amp;lt;/i&amp;gt; Medik)

The present study was conducted in 4 × 4 half diallel cross fashion using the genotypes named as NL-2002, NL-2006, Punjab Masoor-2009 and Markaz-2009 for the evaluation of gene action in the inheritance of economic traits of lentil by following the Griffing (1956) Method of analysis. Minirap 13.1 Copyright© 2000, Minitab inc. Method II, Model I was used for the analysis and gene action was computed by variance component analysis using Mixed Model with GLM (general linear model) procedure. The F1 direct crosses along with the parental genotypes were then evaluated by framing the experiment in RCBD in 3 replications. The data were recorded for the characters which are under the study are, plant height (cm), number of primary branches, number of secondary branches, number of pods per plant, number of seed per pod, seed yield per plant, biomass (gram), 100 seeds weight (gram), harvest index (%), yield per plant. The simple ANOVA for all the characters revealed that difference among genotypes was highly significant. As significant differences were present between the genotypes, it permitted subsequent analysis of the data. The Combining Ability (CA) results showed that value of variance for GCA (General Combining Ability) was significantly higher than that of those of the values of variance of SCA (Specific Combining Ability). Hence current results clearly depicted the role of additive type of gene action governing the characters under study.

Studies on Gene Action and Combining Ability of Cytoplasmic-Genic Male Sterility System based Hybrids in Pigeonpea [&lt;i&gt;Cajanus Cajan&lt;/i&gt; (L.) Millsp.

The present investigation was undertaken with different newly developed six cytoplasmic male sterile (A) lines and five pollen fertility restorers (R) lines as testers were crossed in a line x tester mating design for ascertaining their general and specific combining ability for yield and its component traits in pigeonpea [ Cajanus Cajan (L.) Millspaugh.]. The mean sum of squares due to line x testers interaction were significant for all the characters except plant height, revealed the significant contribution of hybrids for specific combining ability variance components. The ratio of σ2gca/ σ2sca being more than unity was found for the traits, days to flowering, days to maturity, plant height and biological yield, which indicated greater role of additive genetic variance for the inheritance for these traits suggesting and indicated to further improvement as a source of favourable genes for earliness and yield improvement through selection of desired transgressive segregants from segregating generation. The ratio σ2gca/ σ2sca being less than unity was found for the traits, number of branches per plant, number of pods per plant, number of seeds per pod, pod length, 100-seed weight, seed yield per plant, harvest index, protein content and leaf area, which exhibited greater role of non- additive genetic variance for the inheritance for these traits and indicated to exploitation of these traits for improvement of yield through heterosis breeding. Among parents, CMS GT 603 A (28.43) and GTR 95 (17.24) were good general combiner for seed yield and its contributing traits viz . pod length, number of branches per plant, number of pods per plant, number of seeds per pod, pod length, biological yield and leaf area, CMS GT 33 A (0.48) and CMS GT 301 A (0.19) for protein content, CMS GT 33 A (-17.93), CMS GT 288 A (-9.03), GTR 52 (-1.40) and GTR 8 (-0.62) recorded for earliness. These parents can be improved further through intensive crossing programme and subsequent selection of transgressive segregants in desired direction. Hybrids CMS GT 33 A X GTR 18 (29.31), CMS GT 302 A X GTR 8 (25.27), CMS GT 601 A X GTR 52 (21.35) and CMS GT 288 A X GTR 95 (20.89) were the best for seed yield per plant . These crosses had also high sca values for its contributing traits viz . number of branches per plant, number of pods per plant, pod length, harvest index, biological yield and leaf area. These crosses involved poor x average, poor x poor and average x poor combining parents and better performance reflected involvement of interaction of dominant and epistasis type gene action for this trait. So, these crosses can be exploited through hybrid breeding programme.

Wide Compatibility Gene Approaches and Heterosis Relationship in &lt;i&gt;Japonica x Indica&lt;/i&gt; Hybrid Rice (&lt;i&gt;Oryza sativa&lt;/i&gt; L.)

A special class of rice germplasm, referred as wide-compatible can produce hybrids with enhanced spikelet fertility when crossed with japonica×indicia rice lines having neutral allele. Present study was conducted to identify the presence of neutral allele and relationship in the hybrid performance. The wide-compatible genotype screening resulted positive selection having neutral allele and responsible for increased spikelet fertility with possible utilization as donor parent in hybrid development programme for achieving higher yield. Combining ability and heterosis for grain yield and its component traits derived from japonica×indica experimental hybrids revealed higher general combining ability variance than their respective specific combining ability variances indicating the predominance of additive gene action, opened the way for fixing the yield contributing gene by breeding through transgressive selection. Most of the experimental hybrids showed significant and positive SCA effects for grain yield as well as several other yield related component traits. Wide compatibility gene investigation clearly demonstrated the utility of InDel primer in the identification of wide compatible genotypes possessing neutral allele at S5 locus. The genotypes having natural allele (281-bp) can give rise to fully fertile panicle and significant contribution towards yield and heterosis. Association index between genetic diversity and three SH of GY hybrids on the basis of microsatellite data set surprisingly exhibited significant and positive correlation indicated the possible utility of microsatellite markers for successful utilization and establishing the strong heterotic relationship.

Quantitative genetic analysis of agronomic and morphological traits in sorghum, Sorghum bicolor.

The productivity in sorghum is low, owing to various biotic and abiotic constraints. Combining insect resistance with desirable agronomic and morphological traits is important to increase sorghum productivity. Therefore, it is important to understand the variability for various agronomic traits, their heritabilities and nature of gene action to develop appropriate strategies for crop improvement. Therefore, a full diallel set of 10 parents and their 90 crosses including reciprocals were evaluated in replicated trials during the 2013–14 rainy and postrainy seasons. The crosses between the parents with early- and late-flowering flowered early, indicating dominance of earliness for anthesis in the test material used. Association between the shoot fly resistance, morphological, and agronomic traits suggested complex interactions between shoot fly resistance and morphological traits. Significance of the mean sum of squares for GCA (general combining ability) and SCA (specific combining ability) of all the studied traits suggested the importance of both additive and non-additive components in inheritance of these traits. The GCA/SCA, and the predictability ratios indicated predominance of additive gene effects for majority of the traits studied. High broad-sense and narrow-sense heritability estimates were observed for most of the morphological and agronomic traits. The significance of reciprocal combining ability effects for days to 50% flowering, plant height and 100 seed weight, suggested maternal effects for inheritance of these traits. Plant height and grain yield across seasons, days to 50% flowering, inflorescence exsertion, and panicle shape in the postrainy season showed greater specific combining ability variance, indicating the predominance of non-additive type of gene action/epistatic interactions in controlling the expression of these traits. Additive gene action in the rainy season, and dominance in the postrainy season for days to 50% flowering and plant height suggested G X E interactions for these traits.