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Hybrids are widely accepted in all crops to improve yield, but genotype × environment interaction plays an important role in achieving high yield and superior quality traits. Three cytoplasmic genetic male sterile lines and seven testers of Gossypium hirsutum L. varying in seed cotton yield and fiber traits were assessed for hybrid vigor using a line × tester system across three different locations. The objectives of this study were to estimate 1) level of heterosis and specific combining ability (SCA) for fiber traits and seed‐cotton yield; 2) correlation between general combining ability (GCA) and line per se, as well as correlation between genetic distance and SCA; and 3) influence of environmental factors on combining ability estimates and trait correlations in parents and hybrids. The level of heterosis was acceptable for seed-cotton yield (32.46%) and fiber traits except uniformity ratio and fiber elongation. Combining-ability analysis across environments showed significant (P < 0.01) effects for genotypes, GCA, SCA, genotype × environment, GCA × environment, and SCA × environment interactions. Combining-ability variance revealed predominance of non-additive gene effects for seed-cotton yield, gin turnout, and micronaire, and additive gene effects for bundle strength and fiber elongation. A positive relationship was found between GCA effects and mean performance of parents, midparent value, and hybrid performance, with emphasis on the dominant gene effect for most of the traits studied. Positive correlation was found between GD and SCA effect. Environmental factors significantly affected the expression of fiber traits and seed‐cotton yield. The correlations among fiber traits and seed-cotton yield emphasized the possibility for improving both yield and fiber properties.

Breeding progress for drought tolerance in maize has been slow since drought tolerance is a complex trait controlled by many genes. Breeders improving maize for drought tolerance have therefore been using secondary traits and selection indices for selecting the best genotypes under drought stress. The objectives of this study were to determine the combining ability of the inbred lines in stress and non stress environments as well as compare the use and efficacy of secondary traits and selection indices in selecting for drought tolerant genotypes. Fifty hybrids formed through a North Carolina Design II and four checks were evaluated using the 0.1 alpha lattice planting design under optimum and drought environments. General combining ability (GCA), specific combining ability (SCA) and seven drought indices (SDI), stress susceptibility index (SSI), tolerance (TOL), yield index (YI), yield stability index (YSI), mean productivity index (MPI), stress tolerance index (STI) and geometric productivity index (GMP) were used in the computation of results. Results showed that under drought conditions, GCA was highly significant (P<0.001) for grain yield, anthesis-silking interval (ASI) and ears per plant (EPP) while SCA was significant for grain yield and EPP. Selection indices STI and GMP had positive and significant correlation (P<0.01) with grain yield under both drought stress (Ys) and optimum (Yp) conditions. EPP also had significant (P<0.01) and positive correlation with Ys and Yp. ASI had significant and negative correlation with Ys (P<0.01) and TOL (P <0.05). In addition EPP had a positive and significant correlation with STI (P<0.05) and GMP (P<0.01). The results indicated that ASI, EPP, STI and GMP are effective in identifying high yielding genotypes under different moisture regimes. Narrow sense heritability showed that phenotypic variation attributed to genetic effects increased under stress conditions for EPP and ASI and making them more reliable parameters for use in selecting for genotypes under stress conditions. The two secondary traits (ASI and EPP) together with two drought indices; (STI and GMP) can therefore be used in tandem for increased efficiency in selecting for genotypes under stress environments. Key words: Combining ability drought stress, drought index, heritability.

Seven wheat genotypes (Sirvan, Zarin, Pishgam, Karim, Baran, Heidary, and Rizhav) were crossed in diallel mating to develop 42 F1's hybrids. The resultant hybrids along with parents were evaluated during cropping season 2015-16 at agriculture and natural resources Pardis of Tehran University, Iran, using RCB design with 3 replications under drought stress and normal field conditions from the booting stage till physiological maturity. General combining ability (GCA) and specific combining ability (SCA) for agronomic traits were determined. The main objective of the research was the identification and proper selection of best-performing wheat parental genotypes and best F1's hybrids, based on GCA and SCA estimates. Significant differences were observed among the wheat genotypes for all the reported traits in this article. Results for combining ability analysis indicated that mean squares of GCA and SCA effects were significantly high for most of the traits. The estimates of σ2gca and σ2sca and its ratio (σ2gca/σ2sca) indicated that non-additive genetic expression was dominant for most of the traits studied, then the heterosis breading is a useful program, however selection on superior hybrids should be postponed to the next generation for these traits in recombination program. It is concluded that Zarin, and Baran are recommended as the best general combiners for a future wheat breeding program. The maximum values of SCA observed in flag leaf length in normal and peduncle length in drought condition related to crosses of Rizhav with other parents. So, it is suggested these series of crosses can be down to improve these traits at the mentioned condition

Combining ability analysis was studied in an 8 × 8 diallel set of black gram genotypes. Variance due to general combining ability (GCA) among the parents for all the traits, and due to specific combining ability (SCA) among the crosses was deduced. Combining ability analysis is an important tool to find out gene actions and it is frequently used by plant breeder to choose parents with high GCA and hybrids with high SCA effects. GCA is associated with additive genetic effects, whereas SCA is taken as the measure of non-additive type of gene actions, arising largely from dominance and epistatic deviations with respect to certain traits. GCA is attributed to additive and additive gene effects epistasis and is theoretically fixable on the other hand; SCA attributed to non-additive gene action due to dominance or epistasis or both and is non-fixable. The presence of non-additive genetic variance is the primary reason for initiating the hybrid programme. GCA variance (σ 2 gca ) was invariably lower than SCA variance (σ 2 sca ) for almost all characters indicating preponderance of non-additive gene action. The percentage of heritability in broad sense was highest with days to maturity (94.78%) followed by days to 50% flowering (94.67%). The gca effect ranged from -0.16 to 0.25. OBG-31 (0.25) had maximum significant positive gca effect followed by Keonjhar Local (0.24). OBG-17 (-0.16) and TU-94-2 (-0.16) witnessed the maximum negative gca effect for yield/plant followed by B-3-8-8 (-0.14). For yield the range of sca varied from -0.64 to 1.02. Among the 28 F 1 hybrids B-3-8-8 × PU-30 (1.02) had the highest sca effect followed by PU-35 × LBG-17 (0.71) and PU-30 × OBG-31 (0.48) for yield/plant. The mean yield per plant was recorded highest in PU-35 × LBG-17 (6.19) followed by OBG-31 × Keonjhar Local (6.16), LBG-17 × OBG-31 (6.15) and B-3-8-8 × PU-30 (6.14). Among 28 cross combinations 11 crosses exhibited positive sca effect (9 were significant) for this character whereas 17 crosses exhibited negative sca effect (13 were significant).

A study was carried out to study the combining ability effects of diallel cross hybrids for grain yield, agronomic traits and reaction to grey leaf spot (GLS). Forty five experimental diallel cross hybrids made from ten quality protein maize (QPM) inbred lines with varying level of resistance to GLS were evaluated along with three checks at Bako and Jima Research Centers during 2014/2015 cropping season. Analysis of variance showed significant variation (P≤0.05) among genotypes and between environments. This depicted the existence of genetic variation among genotypes in all studied traits. Mean squares characterized by general and specific combining ability effects were significant for the most traits and this suggested that both additive and non-additive gene actions have the contribution in the expression of the traits. However, the ratio of General combining ability (GCA) to specific combining ability (SCA) sum of squares were greater than unity, this revealed that there was preponderance of additive gene action in the expression of all the traits under study. Among inbred lines studied P6 and P10 had a desirable GCA effects for grain yield whereas P1, P4 and P10 were the best general combiners for GLS resistance. Furthermore, P10 was identified as good general combiner for grain yield as well as GLS is therefore recommended to be used in breeding programs with a purpose of developing both high yielder as well as GLS disease resistant genotypes. Crosses, P2×P8 and P4×P6 showed the most desirable performances and SCA effects for grain yield. Grain yield showed positive correlation between ear per plant, plant and ear height, and ear position whereas negative correlation were observed with GLS, days to anthesis, days to silking, plant aspect and ear aspect traits. The information which is generated in this study could be helpful to develop high yielding maize varieties with good agronomic traits as well as GLS resistance. Key words: Agronomic traits, diallel, general combining ability, gray leaf spot, quality protein maize, specific combining ability.

Drought and poor soil fertility are among the major abiotic stresses affecting maize productivity in sub‐Saharan Africa. Maize breeding efforts at the International Maize and Wheat Improvement Center (CIMMYT) have focused on incorporating drought stress tolerance and nitrogen‐use efficiency (NUE) into tropical maize germplasm. The objectives of this study were to estimate the general combining ability (GCA) and specific combining ability (SCA) of selected maize inbred lines under drought stress (DS), low‐nitrogen (LN) and optimum moisture and nitrogen (optimum) conditions, and to assess the yield potential and stability of experimental hybrids under these management conditions. Forty‐nine experimental three‐way cross hybrids, generated from a 7 × 7 line by tester crosses, and six commercial checks were evaluated across 11 optimum, DS and LN sites in Kenya in 2014 using an alpha lattice design with two replicates per entry at each site. DS reduced both grain yield (GY) and plant height (PH), while anthesis–silking interval (ASI) increased under both DS and LN. Hybrids ‘L4/T2’ and ‘L4/T1’ were found to be superior and stable, while inbreds ‘L4’ and ‘L6’ were good combiners for GY and other secondary traits across sites. Additive variance played a greater role for most traits under the three management conditions, suggesting that further progress in the improvement of these traits should be possible. GY under optimum conditions was positively correlated with GY under both DS and LN conditions, but GY under DS and LN was not correlated. Our results suggest the feasibility for simultaneous improvement in grain yield performance of genotypes under optimum, DS and LN conditions.

Combining ability and cultivar superiority of sorghum germplasm for grain yield across tropical low- and mid-altitude environments

This study was conducted at Egerton University, Njoro, Kenya for 2 growing seasons, 2001 and 2002. A diallel cross, without reciprocal crossings, involving 7 maize S1 lines: KSTP001, KSTP003, KSTP004, KSTP005, KSTP008, E2 and E3 was used to study the heterosis and inheritance of days to 50% flowering, plant height, ear height, leaf angle, number of leaves per plant, leaf area index, cob length, cob diameter, number of lines per cob, number of seeds per line, 100-grain weight and grain yield. A randomised complete block design with 3 replicates was used. Analysis of variance was conducted on the data generated at 0.05 significant level using MSTAT. The results showed that general combining ability (GCA) and specific combining ability (SCA) was significant (P&lt;0.05) for all traits under study, suggesting existence of both additive and non-additive gene effects for the traits. However, GCA : SCA ratio was &gt;1 for all traits except cob diameter and 100 seed weight, indicating preponderance of additive gene effects for inheritance of these traits. The study identified KSTP003 as the best combiner for most of the traits, while KSTP001 and E3 was the best combination for most traits. KSTP004 and E3 was good combiner for grain yield. Hybrid KSTP005 × E3 was the best cross for grain yield. KSTP003 × E2 was the best cross for reduction of leaf angle thus good source for erectophile canopies in a hybridisation program. Heterosis estimates showed that heterosis was more important in grain yield, yield components, plant height, number of leaves per plant and, leaf area index than other traits studied. Most of traits studied had a positive and significant (P≤0.01), while all traits studied except days to 50% flowering had a positive and significant (P≤0.01) genotypic correlations. It is recommended that based on their combining ability the lines be recombined to form synthetic maize varieties which can be released both as a variety or used for further improvement using recurrent selection. The lines which combine well for reduction in leaf angle from vertical should be utilised to develop erective maize varieties.

Accurate identification of promising parents is crucial for peanut (Arachis hypogaea L.) cultivar development. The objectives of this study were to (1) determine the combining ability for yield and yield components of six genetically diverse peanut cultivars, (2) examine the relationship between F1 diallel analysis predictions and performance in subsequent generations, and (3) determine if parental performance per se could be used to identify desirable parents. Six peanut cultivars were selected to represent a wide range of genetic diversity and intermated using a half-diallel mating design. The cultivars included two Spanish market-types, Dixie Spanish and Spancross; two runner market-types, Southeastern Runner 56–15 and Tifrun; and two Virginia market-types, Virginia Runner G26 and Georgia 119–20. Parents and progenies were field evaluated each year at Tifton, GA. The F2 and F3 generations were tested in 1986 and 1987, respectively. Combining ability analysis showed that general combining ability (GCA) and specific combining ability (SCA) effects were significant (P &amp;lt; 0.05) for all variables measured. Although SCA remained a significant source of variation in the F3 generation, it accounted for a relatively small portion of the total variation. Tifrun had the greatest GCA effects for plot yield, pod weight per plant, seed weight per plant and seed number per plant. GCA estimates from F1 progeny were not effective in predicting performance in subsequent generations. Parental performance per se was highly correlated with performance across cross combinations in the F2 and F3 generations. GCA estimates from F2 and F3 progeny provided little information not available from simply examining parental performance.

Utilization of stress tolerant maize is key to sustainable production and food security. Limited knowledge on genetics of drought tolerance hampers development of drought tolerant varieties. The aim of this study was to study inheritance and combining ability of drought tolerance and grain yield among early inbred lines of maize. Five inbred lines were mated in full diallel in 2015 major season. The resultant 20 hybrids, 5 parents and 2 checks were evaluated under drought stress and well watered conditions in a screen house. Data was collected on days to 50% tasseling (DT 50%), days to 50% silking (DS 50%), anthesis-silking interval (ASI), leaf rolling, leaf senescence, plant aspect (PASP), plant height (PHT), ear height (EHT), ears per plant (EPP), ear weight, hundred grain weight (100 GW) and grain yield per hectare (GY). Drought condition was induced 40 days after planting (DAP) but watering was continued once per week till maturity. Results from combined ANOVA showed there was high and significant (p<0.01) level of genetic variability among parental lines and hybrids used in all the traits studied except DT 50%, PHT, EHT, EPP and 100 GW. Both additive and non-additive gene actions were important as well as GCA/SCA ratio variance. Lines TZEI-23 (215.22) and TZEI-25 (76.84) had the highest and highly significant (p<0.01) positive GCA effects for GY under drought. Hybrids TZEI-25 x TZEI-13 showed the highest positive and highly significant (p<0.01) SCA effects for GY (385.74) followed by its reciprocal TZEI-13 x TZEI-25 (311.49) under water stress. High broad sense heritability was observed for almost all the traits. High narrow sense heritability were observed DT 50% (0.69), DS 50% (0.80) and leaf senescence (0.61) under drought condition. Eighteen and nineteen hybrids had positive high parent heterosis (HPH) under water stress and well watered conditions, respectively for GY. The parents TZEI-23 and TZEI-25 were identified as the best general combiners respectively under drought and well watered conditions. The highest HPH were observed in many traits for TZEI-13 x TZEI-25 and TZEI-124 x TZEI-13. It is recommended these hybrids are further evaluated in different environments for release to farmers to increase yield. Key words: Maize, inheritance, combining ability, drought, tolerance.

Knowing the type of gene action that controls agronomic traits is essential for the planning and development of a maize genetic improvement program. The objective of this study was to determine the genetic components of general combining ability (GCA), specific combining ability (SCA) and reciprocal effects (ER) involved in the expression of agronomic traits in a set of S3 maize lines. F1 crosses and their progenitors were evaluated at two planting dates: March 18 and May 28, 2014. The following agronomic traits were recorded: plant height, days to male and female flowering, days to physiological maturity, general appearance of the plant, crop yield and some of its components. Statistical differences were found between genotypes for all the traits in the two planting dates. Regarding the effects of GCA and SCA, significant differences were found for all the traits, with a predominance of GCA on SCA for days to male and female flowering, days to physiological maturity, plant height and yield. However, the most important component regarding general appearance of the plant and crop yield was SCA. The ER were significant in plant height, days to female flowering and general appearance of the plant. TNM-5 and TNM-4 lines showed high GCA in yield and its components, and greater precocity. In crosses with high and positive estimators in all the traits evaluated, lines with high ACG estimators and with low and negative effects intervene.

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.

The experimental material comprised nine parental maize inbred lines, which were crossed in a full diallel mating system to produce 72 hybrids during the rabi 2020. In the present investigation, data were recorded on sixteen yield contributing quantitative traits. The analysis of variance revealed significant differences for all traits, indicating substantial genetic variability among the parental lines. Cross combinations i.e. F1s hybrids, particularly EC-639008 x IC-552819, EC-639232 x IC-552819, HYD-52327 x IC-552819, IC-470475 x IC-55281 and HYD-52065 x IC-552819 exhibited high per se performance for various traits in almost all studied seasons. The present investigation recognized parental lines, such as IC-552819, EC- 639008, EC-639232, and HYD-52327, as superior for yield and yield-contributing traits in diverse environments. These parental lines could be considered as good general combines and will be used to develop synthetic varieties. Combining ability analysis showed highly significant mean sum of squares for both general combining ability (GCA) and specific combining ability (SCA), highlighting the importance of both additive and non-additive gene actions. Parents IC-552819 and EC-639008 were identified as good general combiners for multiple traits. Specific combining ability effects revealed promising cross combinations, with HYD-52065 x IC-552819 showing high SCA effects for kernel yield across all environments. Reciprocal effects indicated the importance of cytoplasmic inheritance for certain traits in specific crosses. The study identified hybrids stable under unfavorable and favorable environments based on per se performance and SCA effects. Thirteen hybrids and one check viz., IC-552819 x HYD-52212, HYD- 52212 x EC-639008, IC-470475 x HYD-52065, IC-470475 x HYD-52327, HYD-52327 x IC-472475, HYD-52184 x IC-552819, IC-552819 x HYD-52184, HYD-52184 x EC-639008, HYD-52065 x HYD-52327, HYD-52327 x HYD-52065, EC-639232 x HYD-52065, IC-552819 x IC-437070, IC-437070 x IC-552819 and check Parmeshwar found stable for all the three environments but should also study for multilocation stability so that it gives more clarity of stability for both seasonal and locational.

This study aimed at assessing the magnitude and nature of genetic variation present in seventeen pro-vitamin A (PVA) maize varieties, investigate the extent of association among agronomic characters responsible for yield and its components in the maize varieties and evaluate the performance of the maize varieties. The field experiment was carried out at the Teaching and Research Farm of the Rivers State University, Nkpolu, Port Harcourt under rain fed conditions in May, 2018 and were laid out in a randomized complete block design with three replications. Data were collected on established plants per plot, days to 50% silking, days to 50% anthesis, anthesis-silking interval, plant height, ear height, final stand count, number of ears harvested, grain moisture content, field weight and grain yield. Results showed significant differences (P &lt; 0.01) among varieties for all traits evaluated. PVASYN-13 had the highest grain yield per hectare among other varieties. High heritability estimates coupled with high genetic advance were observed in established plants per plot, anthesis-silking interval, final stand count, number of ears harvested, field weight and grain yield, an indication of the additive nature of their inheritance. Thus, the presence of variation could serve as basis for selection for yield improvement in maize.

In present study forty-five crosses produced from 9 lines and 5 testers using line × tester mating design were evaluated in Randomized Block Design. Estimation of general combining ability (GCA) gives important information for the selection of parents in terms of performance of hybrids and elucidate the nature and magnitude of gene action involved in the expression of quantitative characters. Present study was caried out to determine the type of gene action and identify inbred lines and crosses with good combining ability for yield and its contributing traits. Variance due to specific combining ability (SCA) was larger than general combining ability (GCA) for the all characters except plant height and ear height. It indicates the preponderance of non-additive gene action in expression of those character except plant height and ear height. Inbred lines WNC 40406 followed by BLD 2, BLD 125 and WNC 40080 showed good combining ability (gca) effect for yield and some of the important yield contributing characters. Among Forty-five hybrids, BLD 2 × BLD 103, WNC 40406 × BLD 125, BLD 114 × IMR 113, WNC 40456 × IMR 113 and BLD 114 × BLD 98 exhibited high specific combining ability (sca) effects for yield. These hybrids are recommended for further evaluation to determine their performance.