Heterosis,combining ability and genetic effect,and relationship with genetic distance based on a diallel of hybrids from five diverse <Emphasis Type="Italic">Gossypium barbadense</Emphasis> cotton genotypes

The cultivated tetraploid Gossypium barbadense L. cotton produces superior natural fibers for the textile industry in the world. However, the possibility in utilization of heterosis to further increase its lint yield has not been extensively explored. In this study, two commercial US Pima cotton cultivars and three exotic G. barbadense lines, together with all of their possible hybrids in F₁ and F₂ progeny without reciprocals, were tested for lint yield, yield components, and fiber quality traits in four environments in 2005–2007. With a few exceptions, genotype (G), environment (E), and G × E were all significant or highly significant for all the traits studied. General combining ability (GCA) variances for all the traits in both F₁ and F₂ were also significant, while specific combining ability (SCA) variances were detected only for lint yield, fiber length, and micronaire in both generations and boll weight in F₁. GCA × E was also detected for lint percent, seed index, and fiber length in both F₁ and F₂, and boll weight in F₁, but none of the traits had significant SCA × E. As a group, F₁ and F₂ out-yielded the parent group by 20–40% and 6–10%, respectively. Mid-parent heterosis (MPH) for lint yield in F₁ was generally positive, ranging from ?4.7 to 116.4% with an average of 21.2–48.7%, while lint yield MPH in F₂ ranged from ?23.3 to 69.4% with an average of 6.4–12.4%. However, useful heterosis in lint yield was only detected in the hybrid between the two US commercial cultivars Pima S-7 and DP 340. MPH for other traits was low or not detected. MPH in F₂ was lower than that in F₁ but they were generally positively correlated. The genetic distances (GD) of the parents (based on 467 polymorphic RAPD and AFLP markers) between the five parents was not consistently correlated with MPH and SCA of their hybrids and dominant effects for lint yield and other traits. However, significant and positive correlations between GD of parents and the performance of their hybrids were detected for lint yield, lint percentage, and lint index in both F₁ and F₂ in most of the tests. GD of parents was also correlated with their GCA and additive effects in lint yield, lint percent, lint index, micronaire, plant height, and elongation. The results suggest that the close correlation between GD and hybrid performance per se was mainly due to the existence of GCA and additive effects from parents.     

Estimates of additive and dominance effects for Fusarium head blight resistance of winter triticale

The most effective strategy to control Fusarium head blight (FHB), a devastating disease of small‐grain cereals, is breeding resistant cultivars. This resistance study of F₁ crosses, F₂ and backcross generations of triticale estimates heterosis, general and specific combining ability (GCA, SCA), additive and dominance effects and compares parents with segregating generations. The genetic material consisted of 10 parents with their 45 F₁ crosses and of six parents with their 15 F₂ progeny and backcrosses to each parent. Genotypes were grown in various environments and artificially inoculated with an aggressive isolate of F. culmorum. FHB was assessed, by visual rating, as the mean of four to five individual ratings of disease development. Heterosis for FHB was of little importance. The correlation between the FHB rating of F₁ crosses and their mid‐parent performance was close. GCA was the predominant source of variation, although the significance of the SCA variance also implied non‐additive allelic interaction. The preponderance of additive gene effects is encouraging for increasing resistance by a recurrent selection programme. The relationship between the GCA effect of a parent and its per se performance was close, which gives the possibility of predicting FHB resistance in F₁ crosses. Additive effects were predominant in the F₂ progeny and also in the backcrosses. Transgressive segregants could not be detected. Searching for them should be postponed to the F₃ or later generations.     

Relationship between genealogical distance and breeding behaviour in oats (Avena sativa L.)

Summary Eight oat cultivars and experimental lines from four germplasm sources were crossed in a diallel mating design without reciprocals. F₁ heterosis for grain yield was evaluated in two experiments, and 48 F₂-derived lines from each of the 28 matings were evaluated for bundle weight, grain yield, straw yield, harvest index, height, and heading date in two experiments. Number of transgressive segregates per trait and generalized genetic variance were calculated for each mating. Genealogical distance for each mating was obtained by using coefficient of kinship based on the pedigree of the parents. The relationship between genealogical distance and the three types of breeding behaviour was examined via correlation and regression. Significant correlations occurred only for genealogical distance with numbers of transgressive segregates for height and with generalized genetic variances. Both were positive. Significant heterosis was observed for matings of more distantly related parents. Regressions on genealogical distance, when significant, were linear. Genealogical distance between parents was positive associated with diversity on the basis of breeding behavior.Journal Paper No. J-11874 of the Iowa Agriculture and Home Economics Station, Iowa State Univ., Ames, IA 50011. Project 2447.     

Heterosis and combining ability for grain yield and other agronomic traits in winter triticale

Hybrid breeding is a widely discussed alternative for triticale. Heterosis as well as general (GCA) and specific combining ability (SCA) effects were estimated for eight agronomic traits. The experiment comprised 24 F₁ hybrids, produced by a chemical hybridizing agent, together with their six female and four male parents, grown in drilled plots in two locations. In comparison with the mid‐parent values, hybrids averaged a 6.4 dt/ha (10.1%) higher grain yield, 8.4% more kernels per spike, a 6.8% higher 1000‐kernel weight, 9.7% lower falling number (FN) and 4.4% greater plant height. SCA effects for grain yield were significant and ranged from 4.5 to 6.9 dt/ha for grain yield. Together with GCA x location interactions, they explained most of the variation. For 1000‐kernel weight, GCA effects were predominant. SCA and interactions with location accounted for most of the variation in FN, whereas interactions were negligible for plant height. Correlations between mid‐parent and hybrid performance and between GCA and per se performance of parents were tight for all traits except grain yield, which allows for pre‐selection of parental lines. Although the amount of heterosis in triticale at present is closer to wheat than to rye, by selecting parents for combining ability and identifying heterotic patterns, grain yield heterosis of up to 20% appears sufficiently encouraging to embark on hybrid breeding.     

黄淮地区大豆重要亲本间产量的杂种优势、配合力及其遗传基础

2003-2005年以选自黄淮地区及美国的8个大豆重要亲本品种(系)及其组配的28个双列杂交组合为材料, 分析大豆亲本间的产量杂种优势及其配合力, 探讨高优势组合的遗传基础, 包括杂种优势与亲本系数、SSR标记遗传距离的相关。结果表明: (1)黄淮地区大豆亲本间存在产量超亲优势, 平均20.39%, 组合间差异甚大, 变幅–5.34%~76.88%, 优选出豫豆22×晋豆27、淮豆4号×晋豆27、诱变30×蒙90-24, 超亲优势分别为76.88%、29.90%和34.42%, 超标率均在25.00%以上, 晋豆27和诱变30为优秀亲本材料。单株荚数及单株粒数的优势和产量优势相对一致;(2) 大豆亲本间产量杂种优势既与双亲一般配合力之和及特殊配合力有关, 又不完全相关。高优势高产组合的亲本产量配合力特点为亲本之一具有较高的一般配合力, 或双亲具有较高的一般配合力之和, 兼有较高的特殊配合力。单株荚数和单株粒数的情况和产量一致;(3) 按亲本系数聚类和按SSR标记遗传相似系数聚类揭示的8个亲本间的遗传关系相对一致, 均分为两组, 一组包含6个黄淮中、南部品种(系), 另一组包含1个山西和1个美国品种。要获得高优势高产组合, 亲本间必须具有一定的遗传距离, 但遗传距离大并不一定都高产高优势, 还有其他因素决定杂种优势。     

食葵主要经济性状的配合力及杂种优势分析

选用农家种改良过的6个食葵细胞质雄性不育系和4个优良的分枝型恢复系为亲本,按NCⅡ遗传交配设计,配成24个F₁杂种,研究了9个主要经济性状,即株高、茎粗、生育期、盘径、单盘总粒数、单盘实粒数、结实率、百粒重、单株产量的配合力及杂种优势表现。结果显示：（1）不育系中有8个性状,恢复系中有7个性状的一般配合力差异达显著或极显著水平;有4个性状的特殊配合力差异达到显著或极显著水平;（2）株高、茎粗、生育期、盘径、百粒重等5个性状主要受基因的加性效应控制;单盘总粒数、单盘实粒数、结实率、及单株产量等4个性状则受基因的加性效应和非加性效应共同影响;（3）从GCA分析看,参试的不育系以A6最为理想,A2次之;恢复系则以C3最为理想。从SCA分析看,组合A2C1单株产量效应值最高;（4）杂种优势分析表明,大部分经济性状存在杂种优势,甚至相当一部分存在超亲优势,并且这些优势都是可利用的,F₁多倾向于早熟、粗壮、高杆、大盘、多粒亲本。     

A diallel analysis of various traits in winter triticale

In triticale, preharvest sprouting tolerance is important for yield stability and quality of the grain. Therefore, an experiment was conducted to estimate quantitative genetic parameters of preharvest sprouting tolerance in triticale using a diallel of eight modern triticale cultivars and breeding lines. The 28 F₁‐hybrids and the parents were planted in the breeding nurseries in 2001 and 2002 at four locations. Heading, plant height, falling numbers of two harvest dates, thousand kernel weight (TKW) and preharvest sprouting (Spr) were measured. The heritabilities for plant height and TKW were the highest with 0.91 and 0.85, respectively. Falling number and sprouting showed heritabilities between 0.66 and 0.83. Mid‐parent heterosis (MPHET) was negative for heading, indicating a non‐significant earlier heading of the F₁‐hybrids. In plant height and TKW the heterosis was positive with 4.7% and 6.3% MPHET. Both falling numbers displayed a negative MPHET of nearly −15%. In contrast to falling numbers, the preharvest sprouting of hybrids was slightly reduced in comparison with the parents. In all traits analysed, general combining ability (GCA)‐variances were greater than specific combining ability (SCA)‐variances.     

Combining ability analysis for harvest index in winter wheat

Summary Cereal breeders have used harvest index (HI) as a selection criterion in segregating generations to identify physiologically superior lines with improved partitioning of total assimilate into grain. Information on combining ability for HI of the hard red winter wheat (Triticum aestivum L.) cultivars of the Southern Great Plains is not available. A study was undertaken to examine HI of seven genetically diverse winter wheat parents, evaluate their general combining ability (GCA) and specific combining ability (SCA) effects, and study correlations of HI with several agronomic traits. The seven parents were crossed in a half-diallel mating design to produce 21 crosses. The F₁'s, their F₂ progenies, and the parents were evaluated in replicated field tests at Stillwater and at Lahoma, OK. The combining ability analysis was performed using Griffing's Method 4, Model 1. The results showed significant variation among parents for HI. The GCA and the SCA effects were mostly inconsistent between generations and between environments. However, parents with consistently high HI and positive GCA estimates were identified. The progeny with high HI mostly resulted from parents with high GCA estimates. The correlations between HI and agronomic traits indicated that improvement in HI should also result in high grain yield, early maturity, and short plant height.     

Response to selection, combining ability and heritability of coleoptile length in winter wheat

Selection of winter wheat cultivars with long coleoptiles is an important component of improving emergence, weed suppression and grain yield in low rainfall regions of the world. Seven winter wheat cultivars were hybridized in a Griffing’s half-diallel mating design, method 2 (reciprocals excluded, parents included), model 1 (fixed), and the progeny analyzed for coleoptile length in the F₁ through F₄ for response to selection, general combining ability (GCA), specific combining ability (SCA) and heritability. Highly significant differences existed for GCA among progeny in each generation. SCA was highly significant in the F₁, F₂ and F₄, although SCA estimates were inconsistent among generations in each progeny population. The SCA/GCA ratio was 0.15, 0.11, 0.06 and 0.04 in the F₁ through the F₄, respectively, indicating that additive effects increased with homozygosity. Broad-sense heritability for coleoptile length was estimated at 0.86, 0.76, 0.60 and 0.78 for the F₁ through the F₄, respectively. Realized heritabilities ranged from −0.16 to 0.85 with a mean of 0.32 in the F₃ and ranged from −0.68 to 0.68 with a mean of 0.13 in the F₄. Spearman’s rank correlation coefficients (R_S) were significant for all generation comparisons except the F₁:F₂, indicating that changes in rank for coleoptile length were insignificant. Cultivars with long coleoptiles and high GCA were the best parents for improving coleoptile length. Sustained selection over generations for coleoptile length was more effective than one generation of selection for genotypes both with and without reduced height genes.     

Hybrid performance and heterosis in strawberry (Fragaria × ananassa Duchesne), regarding acidity,soluble solids and dry matter content in fruits

A top‐cross‐mating design among 29 S₄ inbred lines and tester (cultivar ‘Dukat’) was carried out to study their breeding value in terms of general combining ability (GCA). The objectives of this study were to evaluate the acidity, soluble solids and dry matter contents in fruits of progeny F₁ in comparison with S₄ inbred lines as well as the cultivars (S₀); identify strawberry genotypes with high value of GCA for use in cultivar development; and determine mid‐parent heterosis regarding S₄ inbred lines and cultivated strawberry. The 2‐year observations showed statistically significant differences between tested genotypes in terms of the studied traits. The highest breeding value based on GCA was estimated for Chandler 123‐5 for soluble solids and dry matter content, and Kent 7‐6 for acidity. Estimated mid‐parent heterosis had positive and negative values. The highest heterosis in terms of extract and dry matter content (26.71% and 17.50%, respectively) occurred in the offspring Chandler 123‐5 × ‘Dukat’, but as regards acidity in hybrid Chandler 123‐22 with cv. ‘Dukat’. The study of genetic divergence by dendrograms may help to identify parents suitable for obtaining hybrids with higher heterosis effects.     

转基因抗虫棉纤维品质性状的遗传分析

 根据ADAA遗传模型分析了7个转基因抗虫棉亲本、两个非转基因抗虫亲本和36个半双列杂交F1的纤维品质性状的两年资料,估算各项遗传方差和成对性状间的遗传相关性。结果表明,转基因抗虫棉纤维品质的5个性状受加性、显性和上位性的共同控制,其中麦克隆值、2.5%纤维长度和纤维比强度以基因显性效应为主,麦克隆值和纤维整齐度以上位性效应为主。除纤维比强度外,其余4个纤维品质性状都受到环境互作效应的影响,且影响较大。遗传相关分析表明,纤维比强度与2.5%纤维长度的基因型相关和表型值相关达极显著水平,其中加性相关未达显著水平,显性相关达极显著水平。比强度与麦克隆值的基因加性相关也达极显著水平,但表型相关未达显著水平。利用亲本和F₁的资料预测了F₂的基因型值和杂种优势。结果表明,F₂代的麦克隆值、伸长率、2.5%纤维长度、整齐度、纤维比强度的中亲优势分别为1.0%, 8.5%, 0.8%, 0和2.9%, 无超亲优势。     

Heterosis for yield and other agronomic traits of winter triticale F1 and F2 hybrids

Triticale is generally treated as a self‐pollinating crop and line breeding is practised. Hybrid breeding has been discussed for some time, but there is little information for winter triticale. This study investigated heterosis for eight agronomic traits in F₁ and F₂ hybrids grown together with their parents as drilled plots in three environments. On average, grain yield heterosis was 12.5 dt/ha (a relative 10.5%) compared with the mid‐parent value for F₁ hybrids, and 6.2 dt/ha (5.0%) for F₂ hybrids and withawide range of 4.4–17.1 dt/ha for F₁ hybrids. A positive contribution to the heterosis of yield was made by kernels/spike and 1000‐kernel weight, whereas spikes/m² showed negative heterosis. Hybrid plants in F₁ and F₂ were taller than mid‐parents (8.3 cm and 5.3 cm, respectively), with a tendency to earlier heading. The negative heterosis for falling number in F₁ and F₂ hybrids could be a problem for commercial production of triticale hybrids. By selecting parents for combining ability and the identification of heterotic patterns, grain yield heterosis of 20% appears feasible.     

棕色棉与白色棉杂交F1代吐絮期光合特性的杂种优势研究

 选择4个棕色棉品种（系）与5个白色棉品种进行不完全双列杂交,得正反交组合各20个,测定了吐絮期正反交组合的净光合速率、胞间CO₂浓度、叶绿素含量,叶绿素a/b、PSII的最大光化学效率,分析杂交F₁代光合参数的杂种优势表现与正反交之间的差异。结果表明：吐絮期杂种F₁各项光合参数没有明显的正向中亲优势、正向超亲优势。正反交组合之间,除胞间CO₂浓度存在显著差异外,其它光合参数差异不显著,胞间CO₂浓度受到细胞质效应影响。正交组合F1叶绿素含量与胞间CO₂浓度存在显著正相关,反交组合F₁净光合速率与胞间CO₂浓度存在极显著正相关。     

陆地棉遗传距离与纤维品质性状中亲优势及F1、F2表现的相关性研究

通过29个陆地棉品种(系)表型性状及SSR标记遗传距离聚类分析,依据遗传距离大小在不同类群中选择了8个遗传背景差异不同的陆地棉亲本,进行不完全双列杂交,共配制了28个组合,开展了陆地棉纤维品质性状F1、F2表现及其中亲优势与遗传距离之间的相关、回归分析研究.结果发现杂种F1、F2纤维上半部平均长度、整齐度指数、断裂比强度及其中亲优势均与表型及SSR标记遗传距离正相关,其中杂种F1纤维上半部平均长度与2种遗传距离均达到了显著水平,断裂比强度与SSR标记遗传距离达显著水平;伸长率的杂种F1、F2表现及其中亲优势均与表型及SSR标记遗传距离负相关,其中杂种F1伸长率与SSR标记遗传距离显著负相关.回归分析发现与遗传距离达到显著或极显著相关的纤维品质性状,均与对应遗传距离具有显著或极显著拟合的曲线模型.这些显著或极显著的纤维品质性状,可在育种实践中为利用杂种优势改良棉纤维品质提供参考信息.     

陆地棉主要农艺与纤维品质性状的双列杂交分 析简

 本文利用加性-显性与环境互作的遗传模型（ADE模型）,分析8个陆地棉亲本及其F1在不同环境下的农艺和纤维品质性状,在估算遗传方差分量、遗传效应的基础上,分析各类性状间的遗传相关性,并预测F1和F2的杂种优势,为棉花杂种优势利用和新品种选育提供了较有价值的信息。研究表明,农艺与纤维品质性状的遗传主要受加性、显性和加性与环境互作效应控制。遗传相关分析表明,皮棉产量与纤维品质性状的显性相关系数值较大,利用杂种优势在早期世代可以得到协同改良,纤维品质性状间易实现协同改良。杂种优势分析表明,F₁和F₂的皮棉产量均具有显著的超亲优势,纤维品质性状的杂种优势不明显。     

Bread wheat: F1 hybrid performance and parental diversity estimates using molecular markers

In wheat, the possibility of introducing F₁ seed into practical agriculture has been greatly enhanced by the discovery of effective chemical hybridising agents (CHAs). Although some technical and economic problems concerning the use of CHAs for large-scale production of F₁ seed remain to be solved, a first group of F₁ hybrids has been submitted for registration in several European countries i.e., France, England and Italy. Combining ability for grain yield and several agronomic and quality traits was studied in an eight-parent diallel cross. Highly significant combining ability effects were observed for all the traits while specific combining ability effects were statistically significant for grain yield, plant height, heading time and Chopin alveograph parameter P. The level of genetic diversity between parents as estimated using molecular markers is considered a tool for predicting the hybrid performance and heterosis of crosses. To explore this possibility, RFLP and RAPD markers were used to predict the performance of hybrids obtained from diallel and top crosses. The performance of the hybrids was determined in replicated plot trials sown at normal seed density in several locations. Coefficient of parentage (rp), based on pedigree information for all the pairwise combinations of the parents ranged from 0.01 to 0.34. The parents were assayed for random amplified polymorphic DNA (RAPD) with 87 primers which generated 304 polymorphic bands. Genetic similarity between parents, estimated on the basis of common bands using the Jaccard's similarity coefficient (J), ranged from 0.25 to 0.57. Correlation between parental diversity and hybrid performance was generally weak. A positive trend is observed in the yield potential of the hybrids produced in Italy in the last 10 years. In fact among the first set of hybrids produced by random crossing of the available cultivars, none produced 10% more than the checks whereas the last generation of hybrids includes combinations yielding 15% more than the best standards. Our results clearly indicate the need to develop specific strategies in order to identify and/or to select parental lines with a high level of general combining ability (GCA) and specific combining ability (SCA). The information regarding the genetic diversity of the parental lines do not appear helpful for predicting F₁ performance. This revised version was published online in August 2006 with corrections to the Cover Date.     

光子陆地棉种质资源主要性状的遗传评价

以102份光子陆地棉材料为母本,分别与遗传标准系TM-1杂交,获得102个F₁群体。采用随机区组设计,设置3个重复,对光子陆地棉材料主要性状进行遗传评价。结果表明,调查的11个性状表型差异均较大,材料间产量性状(株高、果枝数、铃数、铃重、衣分和子指)差异大于纤维品质性状(纤维长度、纤维强度、马克隆值、整齐度和伸长率),特别是衣分、铃数等性状差异更明显; 除果枝数、马克隆值、伸长率以外,光子亲本群体其他性状的平均值都小于F₁群体。而亲本群体所有性状的变异系数均大于F₁,不同光子材料的杂种优势有很大差别,中亲优势和超亲优势也有很大的差别,有些种质某些性状的中亲、超亲优势为负值,其后代性状表现劣势; 纤维品质性状的中亲、超亲优势与毛子程度均呈负相关,而产量性状的中亲、超亲优势与毛子程度均呈正相关,说明可利用光子材料杂种优势改良纤维品质,而其后代产量性状的杂种优势利用受到限制; SSR分子标记遗传相似系数与各个性状的中亲、超亲优势的相关都不显著,说明在光子材料的育种中,杂种优势是不能通过亲本之间的遗传背景相似程度来预测的。     

General combining ability and heterosis regarding the phytochemical properties in strawberry (Fragaria × ananassa) hybrids

Strawberries are a common and important fruit in human diet because of their high content of essential nutrients and beneficial phytochemicals, which have relevant biological activity in human health. In this study, six cultivars and 15 selected F₁ hybrids between S₄ inbred lines and tester (cv. ‘Dukat’) were evaluated in a field trial over a period of two consecutive years. The amounts of total anthocyanin, phenolics and vitamin C in fruits and antiradical activity were analysed. General combining ability (GCA) and mid‐parent heterosis were also determined for those characteristics. Among all the genotypes tested, the inbred lines of ‘Senga Sengana’ 17 showed the highest breeding value based on GCA for all studied traits. Estimated heterosis varied among genotypes tested. The highest heterosis in terms of vitamin C occurred in the offspring of clone 1387 18‐15 × ‘Dukat’, but with regard to phenols and antiradical activity in hybrid ‘Teresa’ 18‐15 with cv. ‘Dukat’. This study revealed that the differentiation in chemical composition of strawberry fruits between genotypes is clearly dependent on individual genotype combinations and demonstrated the presence of heterosis in phytochemical contents in some specific genotypic combinations.     

Genetic distance and its association with heterosis in peas

Summary The relationship between the genetic distance of parents and both the heterosis of F₁ hybrids and the variance of F₅ lines was investigated in 72 crosses of pea (Pisum sativum L.). The genetic distance between each pair of parents was estimated, using isozyme (GDi), morphological (GDm) or quantitative (GDq) markers and finally a combination of isozyme and morphological markers (GDi+m). GDm was poorly correlated with the other measures of genetic distance, which in turn were strongly correlated with each other. Genetic distance was moderately correlated with the level of heterosis for yield over midparent in the F₁ generation, with the highest correlation obtained from GDi+m. GD was not significantly correlated with heterosis for yield over the better or best parent but it was significantly correlated with all three measures of heterosis for pods per plant and hundred seed weight. There was no correlation between genetic distance and the level of heterosis for yield and total dry matter in the F₂ generation, but GDi, GDi+m and GDq were predictive for the level of inbreeding depression in grain yield and total dry matter. When parents were high in genetic distance, crosses produced highly transgressive segregants for basal branches per plant, hundred seed weight, harvest index and onset of flowering. Genetic distance between parents was thus a useful measure for predicting a portion of hybrid performance and also of the variance of derived inbred lines. It was concluded that when choosing parents for a cross, consideration should be given to their genetic distance as well as their overall adaptation and their yield. There is considerable potential for optimising choice of parental combinations in the development of improved pea cultivars.     

Combining ability and gene action for maturity and agronomic traits in different heterotic groups of maize inbred lines and their diallel crosses

Combining ability information is necessary for selection of suitable advanced lines for hybridization and identification of promising hybrids for development of improved varieties. A number of 14 maize (Zea mays L.) inbred lines and 91 related crosses were evaluated over two years, 2008 and 2009, in a temperate-zone of Iran. The objectives of the study were to identify the best general and specific combiners, heterosis and type of gene actions responsible for agronomic traits. Except for grain yield and growing degree day to milky, significant general (GCA) and specific (SCA) combining ability were observed for all traits. The Baker ratio for plant height (0.15), ear height (0.26), growing degree day to milky stage (0.04), and grain yield (0.002) showed the predominance of non-additive gene effects in the expression of these traits. The heterosis observed for grain yield, grain number, pollination period, ear and plant height was considerably higher than that observed for other traits. The correlations (r) of F₁ means and SCA effects were positive and significantly higher than that of r (F₁, mid-parents) and r (F₁, heterosis) for all the traits except cob percent, growing degree days to silking, and physiological maturity. MO17, K3547/5, and K3615/2 had negative GCA effects for growing degree day to milky stage and maturity. Among hybrids, MO17 × K3653/2, B73 × K3651/2, and K3545/6 × K3493/1 with positive SCAs for pollination period and grain yield had also negative SCA effects for degree day to silking and milky stages. Therefore, the use of these inbred lines and hybrids increases the response to selection for increasing grain yield and early maturity in maize.