General Combining Ability Estimates Research Articles

Molecular and agro-morphological diversity assessment of some bread wheat genotypes and their crosses for drought tolerance.

Wheat, a staple cereal crop, faces challenges due to climate change and increasing global population. Maintaining genetic diversity is vital for developing drought-tolerant cultivars. This study evaluated the genetic diversity and drought response of five wheat cultivars and their corresponding F1 hybrids under well-watered and drought stress conditions. Molecular profiling using ISSR and SCoT-PCR markers revealed 28 polymorphic loci out of 76 amplified. A statistically significant impact of parental genotypes and their crosses was observed on all investigated agro-morphological traits, including root length, root weight, shoot length, shoot weight, proline content, spikelet number/spike, spike length, grain number/spike, and grain weight/spike. The parental genotypes P1 and P3 had desirable positive and significant general combining ability (GCA) effects for shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, shoot length, and root length under well-watered conditions, while P3 and P5 recorded the highest GCA estimates under drought stress. P3 and P4 showed the highest GCA effects for number of spikelets per spike, the number of grains per spike, and grain weight per spike under normal conditions. P5 presented the maximum GCA effects and proved to be the best combiner under drought stress conditions. The cross P1× P3 showed the highest positive specific combining ability (SCA) effects for shoot fresh weight under normal conditions, while P2×P3 excelled under water deficit conditions. P1× P2, P1 × P3, and P4× P5 were most effective for shoot dry weight under normal conditions, whereas P1×P3 and P3×P5 showed significant SCA effects under drought stress. Positive SCA effects for root fresh weight and shoot length were observed for P3×P5 under stressed conditions. Additionally, P4×P5 consistently recorded the highest SCA for root length in both environments, and P3×P5 excelled in the number of spikelets, grains per spike, and grain weight per spike under drought conditions. The evaluated genotypes were categorized based on their agronomic performance under drought stress into distinct groups ranging from drought-tolerant genotypes (group A) to drought-sensitive ones (group C). The genotypes P5, P2×P5, and P3×P5 were identified as promising genotypes to improve agronomic performance under water deficit conditions. The results demonstrated genetic variations for drought tolerance and highlighted the potential of ISSR and SCoT markers in wheat breeding programs for developing drought-tolerant cultivars.

Identification of superior clones of Satureja rechingeri Jamzad. using progeny test

Satureja rechingeri is a precious plant for the pharmaceutical, feed and food industries due to the high content of antimicrobials in essential oil, mainly carvacrol. As a part of domestication and introduction into the cultivation program, a poly cross design was performed to evaluate genetic parameters and the general combining ability of 58 promising clones of S. rechingeri. Half-sib family seeds were grown in an RCBD with ten replications, and plants were assessed for their quantitative and essential oil traits. General combining ability and genetic parameters, phenotypic and genotypic correlations were estimated for all assessed traits. Analysis of variance revealed significant variation among entries of all the characters, indicating the possibilities of exploiting the available variability for further genetic improvement. Estimates of the genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were highest for essential oil yield (98.38% and 213.95%) and essential oil content (91.60% and 135.14%) in 2021 and 2022, respectively. Broad sense heritability estimates for various traits ranged from 16.68 for leaf width to 91.88 for growth type. Essential oil traits showed a high and positive phenotypic and genotypic correlation with plant height, leaf width, number of lateral branches, plant fresh weight, plant dry weight, and growth type. The growth type, number of lateral branches, plant fresh weight, plant dry weight, leaf width, and number of main branches were identified as influential factors in increasing the quantity of S. rechingeri target traits essential oil traits, and dry weight. Based on general combining ability estimates of principal traits, half-sib families of S. rechingeri clones of ‘Z19′, ‘G48′, ‘Z16′, ‘K48′, ‘F3′, ‘K5′, ‘E41′, ‘G27′ and ‘F71′ showed the highest performance. These clones can be selected as parents of synthetic varieties or new genetic sources to select superior genotypes.

ESTIMATION OF COMBINING ABILITY EFFECTS FOR YIELD AND FATTY ACID-RELATED TRAITS IN BRASSICA RAPA USING LINE BY TESTER ANALYSIS

Brassica rapa is an important oilseed crop in Pakistan. It is a rich source of oil and contains 40%–46% oil. In addition, its meal has 38%–40% protein. Given their high levels of erucic acid and glucosinolate, mustard and rapeseed oil is unhealthy as regular cooking oil. A dire need to exploit the genetic variability of rapeseed germplasm is necessary to improve the performance of cultivars. The line × tester analysis helped estimate various types of gene actions that are important to quantitative traits. The key to successful research is selecting suitable lines and testers and designing good mating patterns. Choosing and developing genotypes with high yield and fatty acid profiles are the major concern of rapeseed breeders. The current research on hybridization and evaluation of Brassica rapa accessions sought better harvest and its related traits from the selected germplasm. The combining ability effects determination used line × tester analysis in rapeseed. The accessions’ variability analysis exhibited extremely significant differences in yield and related traits. Recorded data for different morphological and yield-related qualities provided days till 50% flowering, the number of major branches per plant, and the number of secondary branches per plant had positive and significant general combining ability estimates, and all yield-related variables had extremely notable specific combining ability estimates. All the yield-related characteristics displayed a favorable and substantial connection in the examined germplasm. Among the lines, 28244, 40980, and 40981 occurred to be the best general combiners showing the additive gene action. The cross combinations, 40977 × 26283, 40979 × 26283, and 40981 × 26283, indicated significant specific combining ability effects, which showed the non-additive genetic effects of total variance due to the dominance and/or epistasis. The results suggested that the research material used in the remarkable study can benefit by improving yield and fatty acids-related components and can further enhance upcoming breeding programs based on strong particular combining ability impacts.

Combining Ability of Quantitative Traits in Snake Gourd (Trichosanthes Cucumerina Var. Anguina)

The present study was carried out on snake gourd having seven diverse genotypes (TC 01, TC 05, TC 24, TC 33, TC 02, TC 46 and TC 53) used as parental lines and their 21 crosses generated from 7 × 7 half-diallel fashion at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) during March to June 2019 following RCBD with three replications. The aim of the study was to determine general combining ability (GCA) and specific combining ability (SCA) for fruit yield and its related traits including fruit quality traits. General prediction ratio (GPR) of these 14 traits was greater than 0.5 (50%), indicating predominance of additive gene effects over non-additive gene effects. The estimates of GCA for 19 quantitative traits revealed that the genotypes P2 and P6 were good general combiners for promoting earliness as well as most other important characters viz., number of fruits/ plant, individual fruit weight and fruit yield/ plant/ hectare; P2 and P6 were also good for fruit length and fruit diameter, respectively whereas, P4 was good for main vine length and number of nodes on main vine while, P3 was superior for long fruit and 100-seed weight whereas, P5 was good for number of seeds/ fruit and P1 good for less fruit fly infestation including individual fruit weight and fruit length. The most promising specific combiners for fruit yield, quality and yield components were from the 13 crosses viz., P1 × P2, P1 × P3, P1 × P4, P1 × P7, P2 × P3, P2 × P5, P2 × P6, P2 × P7, P3 × P7, P4 × P5, P4 × P6, P4 × P7 and P5 × P7. Out of 13 crosses only two crosses namely, P1 × P2 and P2 × P6 had both the good general combiner parents (high × high). These two crosses were therefore, amenable for improvement of the respective traits through pedigree selection. Remaining 11 crosses displaying high SCA effects for different traits were observed to be derived from parents having various types of GCA effects (high × medium, high × low, medium × low and low × low). The results of 13 crosses therefore, indicate the operation of additive × additive, additive × dominant and/ or dominant × dominant gene interactions for the genetic control of expression of the relative traits.
 Bangladesh J. Agril. Res. 46(4): 491-510, December 2021

Diallel analysis of selected yield-contributing traits in Okra [Abelmoschus esculentus (L.) Moench

Information on gene action controlling quantitative traits is important for effective selection. A five-parent diallel cross, which generated 10 F1 hybrids of okra (Abelmoscus esculentus) were evaluated during the early and late planting seasons of 2019 in Ibadan, Nigeria. Data obtained were subjected to diallel analysis and genotype by yield-trait (GYT) biplot analysis to estimate combining ability effects and identify stable hybrids for measured traits respectively. Genotype mean squares were significant (p≤0.01) for all most measured traits. Furthermore, General Combining Ability (GCA) and Specific Combining Ability (SCA) mean squares were significant (p≤0.05/0.01) for most measured traits, indicating the influence of additive and non-additive gene actions in expression of these traits. Preponderance of non-additive gene effects shows the high influence of the environment on most of the considered traits in this study. Iwo Nla had the most desirable GCA estimates of -0.98 and 1.14, for days to 50% flowering (DTF), number of fruits per plant (NoF) respectively while IK11 had the most desirable GCA values for mature-fruit width (0.21) and 1000-seed weight (5.71). SCA estimates were most desirable for NH47-4 × LD88, NH47-4 × Iwo Nla, with values of -4.21 and 4.32 for DTF and NoF respectively. Hybrids NH47-4 × Iwo Nla and IK11 × Clemson associated with higher NoF x trait might be useful for improvement of number of fruits per plant in this population.

Hybrid Seed Set in Relation with Male Floral Traits, Estimation of Heterosis and Combining Abilities for Yield and Its Components in Wheat (Triticum aestivum L.).

Breeding hybrids with maximum heterosis requires efficient cross-pollination and an improved male sterility system. Renewed efforts have been made to dissect the phenotypic variation and genetic basis of hybrid floral traits, although the potential of tailoring the appropriate flower design on seed setting is less known. To this end, elite wheat genotypes were crossed using a chemical hybridizing agent at different doses. A total of 23 hybrids were developed from a partial diallel design; and planted in an alpha lattice design with their parents at two locations in Morocco, for two years, to evaluate for yield components, heterosis and combining abilities. The 13.5 L ha−1 dose induced a maximum level of sterility (95%) and seed set showed large phenotypic variation and high heritability. In parallel, seed set showed tight correlation with pollen mass (0.97), visual anther extrusion (0.94) and pollen shedding (0.91) (p < 0.001), allowing direct selection of the associated traits. Using the combined data, mid-parent heterosis ranges were −7.64–14.55% for biomass (BM), −8.34–12.51% for thousand kernel weight (TKW) and −5.29–26.65% for grain yield (YLD); while best-parent heterosis showed ranges of −11.18–7.20%, −11.35–11.26% and −8.27–24.04% for BM, TKW and YLD, respectively. The magnitude of general combining ability (GCA) variance was greater than the specific combining ability (SCA) variance suggesting a greater additive gene action for BM, TKW and YLD. The favorable GCA estimates showed a simple method to predict additive effects contributing to high heterosis and thus could be an effective approach for the selection of promising parents in early generations.

Agroindustrial performance and heterosis in sweet sorghum using male-sterile lines with high stem sugar content

The objective of this study was to evaluate the performance of hybrids and the heterosis in crosses of sweet sorghum using juicy sweet male-sterile lines and fertility-restoring lines with and without sensitivity to photoperiod. Thirty hybrids and six controls were evaluated in experiments laid out in a 6 × 6 triple lattice design. The genotypes differed for all traits. The general combining ability (GCA) of the R lines affected all traits, while the GCA of the A lines only affected juice extraction, total soluble solids, and tons of Brix per hectare (TBH). The photosensitive-restoring line CMSXS5022 had the highest positive GCA estimates for the fresh mass production and TBH traits. Heterosis was significant only for days to flowering and plant height. Overall, the photoperiod-sensitive hybrids stood out. The development of male-sterile lines requires better complementarity from restoring lines to reap the benefits of heterosis.

Testcross vs. randomly paired single‐cross progeny tests for genomic prediction of new inbreds and hybrids derived from multiparent maize populations

AbstractNew maize (Zea mays L.) inbred lines are commonly evaluated based on the performance of their progeny when crossed to a single tester line from a different heterotic group (testcross), making tester choice critical. An alternative progeny test is pairing new lines between heterotic groups such that every parent is observed in one hybrid combination. This approach requires half the number of hybrids to test but the general combining ability (GCA) of each parent cannot be estimated. Genomic information can be used to partition parental GCA, while potentially enabling the prediction of dominance deviations. We evaluated doubled haploid lines extracted from two six‐parent synthetic populations from the Iodent (IO) and Stiff Stalk (SS) heterotic groups using either single crosses from random pairs of inbreds or testcrosses. Hybrids were evaluated for yield and agronomic traits in 2014 and 2015 in south‐central Wisconsin. The experiment was conducted using a randomized complete block design with each population type grown in two replicates within two environments. Coincidence of selection of the 25 top performing lines based on testcross yield and single‐cross hybrid yield was 48% for the SS and 11% for the IO doubled haploid lines, increasing to 56% for the SS and 56% for the IO with genomic prediction based on an additive genomic model. Partitioning dominance deviations with the model increased coincidence to 62% for the SS population. Genomic estimates of grain yield GCA in the single‐cross hybrids were significantly more correlated than phenotypic GCA to testcross values for the IO lines, but not SS. Natural and orthogonal interaction estimates of dominance variation were insignificant for all traits, indicating that the inability to partition dominance based on testcross performance should not be a major limitation to identification of high‐performing hybrids. Genomic information improves the prospects of using single‐cross hybrids made from random pairs of new inbreds as an efficient progeny test by allowing the recovery of parental GCA information.

Effect of genotype, sex and parity on growth traits of diallel crossed Nigerian indigenous and exotic pigs

Three breeds of pig namely; Indigenous (IN), Large white (LW) and Landrace (LR) breeds were crossed in full diallel arrangement to evaluate the effects of cross, sex and parity on growth traits as well as establish the nature of gene action due to the growth traits at birth, weaning and 20 weeks of age. Each line crossed in a full 3x3 diallel cross resulted in a total of 132, 107 and 105 pigs at birth, weaning and 20 weeks of age respectively. General Combining Ability (GCA), Specific Combining Ability (SCA) and Reciprocal Effects (RE) were estimated for eight traits which includes Body weight (BWT), Ear length (EL), Tail length (TL), Heart girth (HG), Snout circumference (SC), Snout length (SL), Height at wither (HW) and Body length (BL). There were significant differences (P &lt; 0.05) among the various crosses, sex and parity but no significant interaction. The LRxLW cross consistently expressed higher body weight and morphometric traits than other crosses at birth, weaning and 20 weeks of age, while the INxIN expressed least body weight at birth and 20 weeks of age, while LWxIN was the least at weaning. There was no significant GCA effect (P&gt;0.05) on all the traits measured, but SCA was significant (P&lt;0.01) for all morphometric traits and body weight. RE was significant for body weight at birth and weaning, while at 20 weeks, was significant for SC and HW. The non-significant GCA estimates along with significant SCA estimates suggest that the genes governing the eight traits measured do not act additively, but non-additively, implying that improvement of those traits may be attained by exploiting heterosis through planned crossbreeding. However, the significant reciprocal effect in body weight and some morphometric traits indicates maternal and sex-linked effect at the affected ages, implying that significant reciprocal cross may be used to attain high performance for the growth traits in the progeny.

Heritability and combined parental information to define the number of crosses in circulant diallels

Abstract: In many agricultural crops, the number of parents used in cross breeding make it difficult to obtain all possible hybrids in diallels. Therefore, using maize as a model plant and based on traits with high and low heritabilities, the aim of the present study was to quantify the correlation estimates of the general combining ability (GCA) and specific combining ability (SCA) between a complete diallel and a circulant diallel, with and without the inclusion of parents. For the high heritability trait, the GCA estimates can be obtained with low s values, whereas for the SCA estimates, s values close to half the number of parents should be used. For the low heritability trait, information from parents must be used to obtain the SCA estimates. For the GCA estimates, considering the stabilization of r above 0.70 for s=7, s values greater than half the number of parents must be used in the circulant models.

Combining ability for resistance to Fusarium wilt and yield in black bean

Abstract The objective of this work was to investigate the genetic control of black bean (Phaseolus vulgaris) and to select parents and segregating populations with high resistance to Fusarium wilt, high yield, and greater 100-seed weight (100SW), using a partial diallel cross. Twenty-five populations were obtained from two groups of parents – the first with five parents resistant to and the second with five parents susceptible to Fusarium wilt. The segregating populations were evaluated in experiments in three years/generations for reaction to Fusarium wilt, yield, and 100SW in an area naturally infested with the pathogen. The diallel analysis showed additive and nonadditive effects in control of the three studied traits, with predominance of additive effects. CNFP 15194, CNFP 15207, and 'BRS Esplendor' are the genotypes with high and negative general combining ability estimates (gi = -0.59, -0.76, and -0.13, respectively), being recommended for use as parents for resistance to Fusarium wilt. Among them, CNFP 15194 also forms populations with a greater 100SW (gi = 0.69). The BRS FP403 cultivar is recommended as a parent to increase yield (gi = 218) and 100SW (gi = 1.46). Six populations were selected to obtain black bean lines that combine resistance to Fusarium wilt, high yield, and high 100SW.

Effect of genotype, sex and parity on growth traits of diallel crossed Nigerian indigenous and exotic pigs

Three breeds of pig namely; Indigenous (IN), Large white (LW) and Landrace (LR) breeds were crossed in full diallel arrangement to evaluate the effects of cross, sex and parity on growth traits as well as establish the nature of gene action due to the growth traits at birth, weaning and 20 weeks of age. Each line crossed in a full 3x3 diallel cross resulted in a total of 132, 107 and 105 pigs at birth, weaning and 20 weeks of age respectively. General Combining Ability (GCA), Specific Combining Ability (SCA) and Reciprocal Effects (RE) were estimated for eight traits which includes Body weight (BWT), Ear length (EL), Tail length (TL), Heart girth (HG), Snout circumference (SC), Snout length (SL), Height at wither (HW) and Body length (BL). There were significant differences (P &lt; 0.05) among the various crosses, sex and parity but no significant interaction. The LRxLW cross consistently expressed higher body weight and morphometric traits than other crosses at birth, weaning and 20 weeks of age, while the INxIN expressed least body weight at birth and 20 weeks of age, while LWxIN was the least at weaning. There was no significant GCA effect (P&gt;0.05) on all the traits measured, but SCA was significant (P&lt;0.01) for all morphometric traits and body weight. RE was significant for body weight at birth and weaning, while at 20 weeks, was significant for SC and HW. The non-significant GCA estimates along with significant SCA estimates suggest that the genes governing the eight traits measured do not act additively, but non-additively, implying that improvement of those traits may be attained by exploiting heterosis through planned crossbreeding. However, the significant reciprocal effect in body weight and some morphometric traits indicates maternal and sex-linked effect at the affected ages, implying that significant reciprocal cross may be used to attain high performance for the growth traits in the progeny.

Tolerance to Fusarium verticillioides infection and fumonisin accumulation in maize F1 hybrids and subsequent F2 populations

AbstractFusarium verticillioides causes Fusarium ear rot (FER) in maize (Zea mays L.), thus reducing grain quality, yield, and contaminates grains with fumonisins. Grain infection by these fungi occurs before harvest and selection of parental lines resistant to fumonisin accumulation for breeding purposes is the most effective and environmentally friendly control strategy for F. verticillioides. This study intended to evaluate F1 hybrids and F2 breeding populations in Kenya for improved resistance to FER and fumonisin contamination. Trials were artificially inoculated and FER severity, F. verticillioides accumulation, and fumonisin contamination were determined. Inheritance of resistance was also determined in the F1 hybrids. CML444 × MIRTC5, R119W × CKL05015, and CML444 × CKL05015 exhibited little to no FER and had the least fungal and fumonisin contamination, respectively. Inbred lines CML495, CKL05015, and P502 had negative, significant general combining ability (GCA) estimates for F. verticillioides colonization and fumonisin contamination, but positive, significant GCA estimates for 1,000‐kernel weight, respectively. The genotype × environment interaction was the main source of variation observed in the F2 populations with R119W × CKL05015 and CML444 × CKL05015 being the most tolerant to fungal and fumonisin contamination in Kiboko and MIRTC5 × CML495 the most tolerant in Katumani.

Genetic analysis of Agronomic Traits of Wheat under Terminal Drought Stress

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 and gene action analysis in a half-diallel cross of Brassica rapa L.

Fifteen hybrids along with six parents were tested to identify good combiners through analyzing combining ability and gene action for yield and its attributes. The experiment was conducted in randomized complete block design with three replications during 2010/11 at research farm of Sher-e-Bangla Agricultural University (SAU), Dhaka. Data for days to 50% flowering and 80% maturity, plant height, number of primary and secondary branches, number of pods per plant, number of seeds per pod, pod length, seed yield and 1000-seed weight was recorded for analysis.The results showed that mean squares for parents, hybrids, parent vs hybrid were significantly different (p&lt;0.01 or p&lt;0.05) for most of the traits. Highly significant mean squares due to general combining ability (GCA) were found for all the traits except for length of pod, whereas highly significant mean squares due to specific combining ability (SCA) were also found for days to 50% flowering, number of secondary branches per plant, number of pods per plant, length of pod and seed yield per plant. This indicated that both additive and non-additive gene effects were important but additive gene effects were predominant for the expression of most of the measured traits. Estimates of GCA and SCA effects for yield and its attributes suggested that parent BARI Sarisha-6, BARI Sarisha-15 and Tori-7 was good combiners for different traits. Hayman’s graphical analysis indicated both over- and partial-dominance for growth and yield attributes. As dominant (non-fixable) variation was high for most of the attributes, substantial improvements of these traits may be possible by transferring complementary gene into non-epistatic high-dominance crosses or eliminating duplicate genes from high-dominance crosses. Considering GCA, SCA and per se performance BARI Sarisha-6, BARI Sarisha-15 and Tori-7 might be good parents towards an effective breeding programme.

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

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

MORPHOLOGICAL IDENTIFICATION AND EVALUATE THE COMBINING ABILITY AND HETEROSIS OF SOME INBRED LINES OF MAIZE AND ITS CROSSES

In 2016 five maize inbred lines were crossed in all possible combinations without reciprocals by using a half diallel crosses mating design to obtain 10 single crosses. Parental inbred lines and their F1 single crosses were evaluated through 2017 season to evaluate the role of general and specific combining ability, heterosis and the morphological characteristics. A randomized complete block design with three replicates was used. Results showed that mean squares of genotypes, general combining ability (GCA) and specific combining ability (SCA) were highly significant for all studied yield traits. The GCA/SCA ratio was less than unity for all studied traits, this means that these traits are predominantly controlled by non-additive gene action. Positive significant GCA effects were found for all studied traits. Based on GCA estimates, it could be concluded that the best combiners were Inb 209 and Inb 239 for most of studied traits. This result indicated that these inbred lines could be considered as good combiners for improving yield and its attributes. Positive significant SCA effects were found for all studied traits. Based on SCA effects, the best crosses for ear diameter, 100-kernel weigh and kernel number/row was C1; for ear length was C10 and for ear weight/plant, grain weight/plant and shelling percentage was C8. Results showed positive significant heterosis values for all studied yield traits. The best crosses over both their mid-parents and better-parents for ear diameter and 100-kernel weigh was C2; for ear length and kernel number/row was C5; for ear weight/plant and grain weight/plant was C9 and for shelling percentage was C8.

Genetic parameters and yield potential of polyembryonic maize genotypes

In the context of the mutants, polyembryony in maize (PEm) has agronomic potential; therefore, the inclusion of the PEm in new varieties may be useful when considering the ascending demand for food. The objective of this study was to develop new genotypes with high productivity potential, superior to in local area, and useful for family and extensive agriculture. In this work, single crosses were carried out between three pure lines and the high frequency polyembryonic populations. The resulting F1 were advanced to the third generation (G3) and the genotypes obtained from this last generation were used as progenitors of a mating plan, according to the Griffing method 4. The resulting crosses were evaluated in a yield test measuring common characteristics of economic importance (Days to Male Flowering (MF), Plant Height (PH), Cob Height (CH), Fusarium Rotten cobs, Cobs (CFUS), Yield (YLD), and analyzed with the computer routine DIALLEL-SAS05. The results allowed to indicate that both the source of variation Genotypes as additive effects (GCA) presented significance for all variables, while non-additive (SCA) were significant only in the variables of cob sanity (p≤0.01) and productivity (p≤0.05). In this regard, most of the variables showed a greater contribution of the effects of General Combining Ability (GCA) compared to Specific Combining Ability (SCA). In addition, it was observed that the crosses were superior in all the variables evaluated with respect to BAP and NAP, and statistically similar in some cases with respect to hybrids. This means that this type of segregant polyembryony crosses can compete with other materials evaluated in the region. The estimation of GCA and SCA generated information on the potential of the studied parents and their crosses and are worthy of being taken into account in the formation of varieties.

Selection of parents for low nitrogen stress through the combining ability of maize partially inbred lines

The objective of this work was to estimate the general combining ability of partially inbred lines under high and low nitrogen (N) conditions and to select promising lines to obtain high yields for both conditions. Fifty-five partially inbred S1 progenies were evaluated using the top-cross method, where the lines were crossed with two testers. The 110 top-cross hybrids were evaluated for grain yield during the off-season of 2012 at two sites in the Brazilian Midwest. Partial diallel analysis was performed with the adjusted means of each of the individual analyses of the top crosses. The combining ability of partially inbred lines and testers as well as their interaction with N levels, was estimated for each site. The coefficient of concordance among 15 partially inbred lines selected by the highest general combining ability estimates for each N level was 0.60. The S1 lines 39, 11, 41, 55, 38, 37, 6, 8, and 14 were selected at both N levels. This indicates that these lines can be used to identify ideal hybrids for growing in the off-season in the Brazilian Midwest.

Partial diallel and potential of super sweet corn inbred lines bt 2 to obtain hybrids

ABSTRACT The aims of this study were to determine the potential of S4 super sweet corn inbred lines for hybrid synthesis, identify the predominant types of gene action and correlations among different traits, significant for breeding programs. The 81 hybrids obtained from a partial diallel 9x9 and three checks were evaluated. A complete randomized block design, with three replicates, and two sowing seasons was used. We could notice significant hybrid effects, general combining ability (GCA) of GI and GII groups and specific combining ability (SCA) in relation to evaluated traits, highlighting the existence of hybrids with superior performance and the expression of additive and non-additive effects. The inbred lines: L1, L3, L6 and L9 (GI) and L1’, L7’ and L9’ (GII) showed the best GCA and SCA estimates, being present in the nine selected hybrids with superior and competitive performance in relation to the checks. The estimated correlations indicate that, for a breeding program aiming to increase grain productivity, evaluating, at least, the dehusked ears, prioritizing genotypes with larger ear diameters and longer ear lengths is important.