Partial diallel analysis between maize inbred lines

(1)

http://dx.doi.org/10.15361/1984-5529.2016v44n1p71-82

71

Partial diallel analysis between maize inbred lines

Análise dialélica parcial entre linhagens endogâmicas de milho

Diego BARETTA¹; Maicon NARDINO²; Valmor Antonio KONFLANZ³; Ivan Ricardo CARVALHO¹; Carlos BUSANELLO¹; Antonio Costa de OLIVEIRA⁴; Velci Queiróz de SOUZA⁵;

Luciano Carlos da MAIA⁶

1 Pós-graduandos em Agronomia – Universidade Federal de Pelotas (UFPel). Área de Fitomelhoramento barettadiego@gmail.com; carvalho.irc@gmail.com; carlosbuzza@gmail.com

2 Autor para correspondencia. Pós-graduando em Agronomia – Universidade Federal de Pelotas (UFPel). Área de Fitomelhoramento. nardinomn@gmail.com

3 Melhorista da empresa KSP Sementes, Ltda. Pato Branco-PR. valmor@kspsementes.com.br

4 Professor Ph. D., Universidade Federal de Pelotas-RS. Departamento de Fitotecnia. acostol@terra.com.br

5 Professor Dr., Universidade Federal de Santa Maria, Campus de Frederico Westphalen. velciq@gmail.com

6 Professor Dr., Universidade Federal de Pelotas-RS. Departamento de Fitotecnia. lucianoc.maia@gmail.com Recebido em: 26-06-2015; Aceito em: 25-09-2015

Abstract

Diallels in maize provide the knowledge of genetic parameters of lines and heterotic groups used. In this study, the general combining ability and specific combining ability, GCA and SCA respectively, were estimated in a partial diallel cross between maize inbred lines in five crop environments. In the 2011/2012 crop, some important agronomic characteristics were evaluated in five environments of southern Brazil. The difference of hybrids and environments was significant for all characters, however, the hybrid x environment interaction was significant only for plant height (PH) and grain yield (GY). GCA effects for the two heterotic groups and SCA effects were significant for all characters when hybrids were evaluated by the average of environments. Only for PH and GY the SCA x environment interaction was significant. The heterotic group I (female), arising from commercial single hybrids with high grain yield, showed interaction only between GCA x environment for PH, indicating predominance of additivity for the other characters in these lines, which do not vary according to different environment conditions. In most cases, hybrids with the best SCA values are not obtained from lines with the best GCA values.

Additional keywords: general and specific ability; genetic effect; Zea mays L.

Resumo

Dialelos em milho propiciam conhecer parâmetros genéticos das linhagens e grupos heteróticos utilizados.

Neste trabalho, foram estimadas a capacidade geral de combinação e a específica de combinação, CGC e CEC, respectivamente, num cruzamento dialélico parcial entre linhagens endogâmicas de milho em cinco ambientes de cultivo. Na safra de 2011/2012, foram avaliados alguns caracteres de importância agronômica em cinco ambientes do Sul do Brasil. A diferença dos híbridos e ambientes foi significativa para todos os caracteres; entretanto, a interação híbrido x ambiente foi significativa somente para altura de planta (AP) e rendimento de grãos (RG). Os efeitos da CGC para os dois grupos heteróticos e de CEC foram significativos para todos os caracteres quando os híbridos foram avaliados pela média dos ambientes. Somente para AP e RG a interação de CEC x ambiente foi significativa. O grupo heterótico I (fêmeas), oriundo de híbridos simples comerciais com alto rendimento de grãos, apresentou somente interação entre CGC x ambiente para AP, indicando predominância de aditividade para os demais caracteres nestas linhagens, que não sofrem variações em função das diferentes condições do ambiente. Na maioria dos casos, os híbridos com melhores valores de CECs não são resultantes de linhagens com os melhores valores de CGCs.

Palavras-chave adicionais: capacidade geral e específica; efeito gênico; Zea mays L.

Introduction

Maize accounts for a significant growing area in Brazil. It is an important source of raw material for use in human and animal food and many industrial products. World maize production was 872.06 million tons, in an area of 177.38 million hectares. Brazil had an output of 75.19 million tons in 15.32 million hectares with an average yield of 4,902 kg ha^-1

(CONAB, 2014). The estimated average productivity lags far behind the genetic potential of maize cultivars, which, through the continuous process of improvement applied by the breeders with the adoption of different strategies, have raised the standards of productivity.

One of the first decisions to be made by breeders is the appropriate choice of the parents to set up the artificial crossings. Among the genetic-

(2)

72

statistical techniques used, diallel analyses stand out for the large number of genetic information they provide to the breeder (Seifert et al., 2006). This analysis aims to study the "diallel genetic design", extracting estimates of useful parameters in selection of superior parents for hybridization and in understanding of the genetic control of the characters (Cruz et al., 2012).

One of the most commonly used methodolo- gies, described by Griffing (1956), provides information on additivity, dominance, epistasis and maternal inheritance of parents in artificial crossings, where the sum of squares of the treatments is split into effects of general combining ability (GCA), specific combining ability (SCA), and, depending on the method, reciprocal effects. The relative importance of the variances of the GCA and SCA are related to the additive and non-additive effects (dominance and epistasis), respectively.

Several genetic studies on the grain yield character have been conducted in order to estimate the proportions of the total genetic variance that are attributable to additive and non-additive effects.

Additive genetic effects of 61.2% have been reported for this character, being the dominance effect of 38.8%, assuming that epistasis effect and connection do not occur (Hallauer et al., 2010). Attempts have been made to estimate the additive and dominance effects to other characters such as plant height, ear, number of ears per plant (prolificacy), ear length, ear diameter, number of kernel rows, number of kernels per row and depth of kernels in the ear. The rate for dominance effects, on average, is considerably lower for these characters when compared to grain yield, suggesting that most of the genetic effects may be attributed to additive effects (Hallauer et al., 2010).

Several examples of use of diallel analysis for parental selection and estimation of genetic effects are available in the literature for maize (Oliboni et al., 2013, Izhar & Chakraborty, 2013, Barreto et al., 2012, Rodrigues et al., 2009, Ferreira et al., 2008 and Pinto et al., 2007).

Thus, this study aimed to evaluate the genetic parameters of some important agronomic characteristics in hybrids of maize inbred lines, from different heterotic groups obtained by recombination of commercial single and triple hybrids, through a partial diallel in five different environments in the agricultural year 2011/2012.

Material and methods

Fifteen inbred lines were used as female parents (group I), obtained from crossings between commercial single hybrids that presented characteristics of high grain yield and eight inbred lines were used as male parents (group II), obtained from crossings between commercial triple hybrids with rustic characteristics, forming two distinct heterotic groups, previously obtained in KSP

Sementes Ltda. in Clevelândia-PR. In the agricultural year 2010/2011, these lines were subjected to artificial crossing according to the partial diallel model and the following crossings were performed: 1x1’, 1x4’, 2x3’, 3x1’, 3x4’, 4x3’, 4x7’, 4,8’, 5x3’, 5x4’, 6x3’, 6x4’, 7x4’, 8x4’, 9x4’, 10x5’, 11x3’, 12x3’, 13x3’, 13x4’, 14x4’, 15x3’, 15x5’, 15x8’ and 15x2’, resulting in a total of 25 hybrid combinations. The hybrid seeds obtained from the crossings were harvested by hand, dried and prepared for experiment seeding.

Experiments to evaluate the hybrids were conducted in the agricultural year 2011/2012, in five different locations of the three states of southern Brazil. In Rio Grande do Sul, it was conducted in the city of Frederico Westphalen, with coordinates 27°23'47 '' S, 53°25'35 ''W, 480 m. In Santa Catarina, in the city of Itapiranga (27º10'10"S, 53º42'44"W, 206 m). In Paraná, in three locations: Pato Branco (26°13′44″S, 52°40′15″W, 760 m), Ampére (25°54'20''S, 53º25'54''W, 718 m) and Clevelândia (26°21'17''S, 52°28'56''W, 860 m).

The experimental design was a randomized block design with three replications for each of the five environments. The experimental units were composed of two lines with five meters in length, spaced 0.70 meters, sown with no-till seeder. Sowing period was according to the agroclimatic zoning of each site and cultural practices were the same for the five locations. After crop emergence and estab- lishment, hand thinning was performed to adjust the stand of 42 plants per experimental unit, equivalent to 60,000 plants ha^-¹.

Characters were evaluated in five plants of each plot: a) plant height (PH) in meters; b) height of ear insertion (EH) in meters; c) grain yield per plot (GY) in kg; d) ear diameter (ED) in millimeters; e) ear length (EL) in centimeters. Data were subjected to analysis of variance of each environment individually to prove the homogeneity of variances and the joint analysis of data was later performed considering the five study environments. With the finding of significant effects of the interaction (GxA), diallel analysis was carried out for each location separately. In the absence of interaction, estimates were obtained by the joint average of the five environments. All analyses were developed in Genes computer program (Cruz, 2013). Model I (considered according to sample nature as a fixed template, since the parents are deliberately selected and do not match a random sample of the population) and Method IV (in which p(p-1)/2 combinations are included, in this method, we work only with information of F1, excluding parents and reciprocal F1 hybrids) described by Griffing (1956) were used, adapted to partial diallels for multiple environments, as follows:

Y_ij= μ+ g_i+ ǵ_j+ S_ij+ ε_ij (1) Where: Yij: average value of hybrid combination between the i-th line of the group 1 and j-th line of the group 2; μ: general average of the test; gi: effect of

(3)

73

general combining ability of the i-th line of the group 1; ǵ_j: effect of general combining ability of the j-th line of the group 2; S_ij: effect of specific combining ability between the order lines i and j of the groups 1 and 2, respectively; ε_ij: average experimental error.

Results and discussions

According to the analysis of variance (Table 1), for all characters F test showed significant differ-

ences for the sources of variation, general combining ability (GCA I, II) and specific combining ability (SCA), showing the existence of variability for GCA effects associated with genes of additive action and SCA effects associated with genes of non-additive action in the genetic control of the characters, corroborating with the results obtained in studies of Oliboni et al. (2013) and Ferreira et al. (2008) involving the diallel analysis with other maize lines.

Table 1 - Summary of joint diallel analysis of variance for characters ear height (EH), plant height (PH), grain yield of the plot (GY), ear length (EL) and ear diameter (ED) in maize single hybrids, evaluated in five crop environments. CGF/FAEM/UFPel, Pelotas, 2013.

Source of variation GL

Mean square (MS)

EH PH GY EL ED

(m) (m) (kg) (cm) (mm)

CROSSINGS (C) 119 3.481** 13.060** 152.996** 709.976** 5993.133**

GCA I 14 2.091** 7.889** 105.253** 441.731** 3737.334**

GCA II 7 15.833** 59.160** 670.176** 3159.322** 26970.413**

SCA 98 2.797** 10.506** 122.875** 573.344** 4817.013**

ENVIRONMENT (E) 4 0.523** 13.997** 49.033** 23.294** 65.607**

C x E 476 0.020^ns 0.453** 1.880** 1.078^ns 3.168^ns

GCA I X E 56 0.015^ns 0.272** 1.098^ns 0.823^ns 1.481^ns

GCA II X E 28 0.089** 2.011** 7.437** 3.355** 11.152**

SCA X E 392 0.016^ns 0.367** 1.594** 0.952^ns 2.839^ns

Residue 1180 0.021 0.030 1.016 1.226 4.621

General Average - 1.178 2.290 7.800 16.895 49.101

CV (%) - 9.31 10.45 13.44 5.78 4.22

GL - degree of freedom; ^ns and ** - non-significant F and significant at 1% of probability, respectively; CV - Coefficient of variation.

The source of environmental variation (E) showed a significant effect for all characters, showing different behavior of environments. Significant effect of the crossing x environment interaction is observed for characters PH and GY, indicating different responses of hybrids in relation to different environments evaluated for these characters, as for the characters EH, EL and ED the CxE interaction was non-significant, the split this source of variation into GCAIxE, GCAIIxE and SCAxE was not performed. The specificity of the performance of these hybrid combinations over the environments was possibly due to the different intrinsic soil and climate conditions of each growing region. The hybrid x environment interactions are frequently checked.

Possibly, the narrow genetic base of these hybrids is responsible for performance variations in different crop environments (Pinto et al., 2007), mainly due to lower phenotypic plasticity observed in single hybrids compared to double and triple hybrids.

The mean squares of GCA x environment interaction were significant only for the character PH for group I (females), demonstrating a certain stability of the crossings of that group to maintain the steady performance of the other characters in different environments. Similar results were reported by Rodrigues et al. (2009). With the significance of

GCA x E interaction, there are indications that the lines contribute differently in expressing these characters in different environments. In turn, in group II (male) significant GCA x E interaction was observed for all evaluated characters.

For the effect of the interaction between SCA x environment, characters PH and GY showed significant effect, deviating from the expected behavior based on general combining ability of these lines in different environments. Significant interactions between SCA x E for grain yield were also evidenced by Deitos et al. (2006), revealing that non-additive genetic effects were significantly influenced by environmental changes. Evidence of interactions showed that, for PH and GY, estimates of combining abilities have changed according to the variation in crop environments.

Regarding the relative contribution to the effects of GCA (group I and II) and SCA obtained from the sum of squares (resulting from multiplication of MS by the respective GL of each source of variation) of hybrid combinations, it was found that non-additive effects (SCA) showed greater relevance than additive effects (GCA group I and II) for all analyzed characters with proportions of 66%, 26% and 7% for SCA, GCA group II and GCA group I, respectively. This fact showed the predominance of non-additive effects

(4)

74

among loci related in the genetic control of characters.

Moreover, the high magnitude of the effects of SCA reveals that the lines have different degrees of complementarity between the groups, indicating that the hybrid combinations have a phenotypic performance different from the expected only for GCA in the expression of the characters in question.

Superiority of non-additive effects for the characters ear diameter, ear length and grain yield in maize were reported by Izhar & Chakraborty (2013). Ferreira et al.

(2008) found prevalence of non-additive effects for the character ear height in a partial diallel involving 24 single hybrids of maize. Souza Neto et al. (2015) reported the existence of non-additive effects in assessing the diallel analysis of maize forage hybrids for agronomic and nutritive characteristics of maize.

Low GCA estimates indicate the parents with combinations that do not differ much from the average of all crosses in the diallel system. On the other hand, large values, with positive or negative sign, indicate parents that increase or decrease a character, respectively, in relation to the average of all parents of the diallel through additivity. Regarding the behavior of lines of group I (Table 2), it was observed that for EH, negative GCA estimates were observed for lines 2, 7, 8, 9, 10, 11, 12 and 14 on the average of the five environments, highlighting the lines 14 (-0.106), 8 (-0.103), 9 (-0.101) and 11 (-0.098) with the highest negative magnitudes for the character.

These results indicate that this heterotic group has mostly genes/alleles that favor the reduction of EH.

Table 2 - Estimates of the effects of general combining ability (GCA) of 15 "female" lines (group I), for the character height of ear insertion (EH), plant height (PH), grain yield of the plot (GY), ear diameter (ED) and ear length (EL) in maize hybrids, for five crop environments. CGF/FAEM/UFPel, Pelotas, 2013.

Group I (Females)

Lines EH PH

GY ED EL

(1)A1 A2 A3 A4 A5 Average

1 0.052 0.097 0.165 0.107 0.050 0.089 0.102 0.356 2.033 0.715 2 -0.091 -0.176 -0.294 -0.187 -0.084 -0.167 -0.182 -0.666 -4.187 -1.403 3 0.042 0.098 0.141 0.076 0.033 0.072 0.084 0.293 2.180 0.535 4 0.178 0.317 0.621 0.358 0.161 0.328 0.357 1.266 8.077 2.867 5 0.042 0.070 0.157 0.080 0.044 0.075 0.085 0.309 2.227 0.808 6 0.055 0.108 0.152 0.144 0.041 0.094 0.108 0.279 1.881 0.700 7 -0.097 -0.190 -0.297 -0.209 -0.097 -0.153 -0.189 -0.683 -4.155 -1.409 8 -0.103 -0.197 -0.288 -0.222 -0.096 -0.177 -0.196 -0.729 -4.301 -1.475 9 -0.101 -0.169 -0.338 -0.216 -0.086 -0.161 -0.194 -0.605 -4.072 -1.333 10 -0.090 -0.166 -0.330 -0.172 -0.099 -0.161 -0.186 -0.628 -4.038 -1.450 11 -0.098 -0.162 -0.315 -0.212 -0.089 -0.154 -0.186 -0.689 -4.251 -1.380 12 -0.094 -0.174 -0.309 -0.188 -0.094 -0.160 -0.185 -0.649 -4.015 -1.474 13 0.058 0.103 0.152 0.120 0.069 0.083 0.105 0.362 2.269 0.629 14 -0.106 -0.179 -0.301 -0.238 -0.109 -0.174 -0.200 -0.741 -4.142 -1.372 15 0.352 0.621 1.083 0.759 0.353 0.565 0.676 2.525 14.494 5.042

(1)A1 - Ampére-PR, A2 - Clevelândia-PR, A3 - Itapiranga-SC, A4 - Pato Branco-PR and A5 - Frederico Westphalen-RS.

Considering the EH, line 6', which gave the lowest average estimate (-0.175) within the group II, can be highlighted together with line 7' (-0.171) (Table 3). Such parents, for showing greater negative GCA estimates, have high concentrations of favorable alleles to reduce the character, causing its reduction in crossings where they participate (Vencovsky &

Barriga, 1992).

The ten highest negative estimates, of greater SCA magnitude for EH, in the average of the five environments, were obtained in the crosses 15x4' (-1,036), 4x4' (-0,863), 1x3' (-0,710), 3x3' (-0,700), 10x4' (-0,595), 2x4' (-0,594), 12x4' (-0,590), 11x4' (-0,587), 10x3' (-0,568) and 7x3' (-0,561) (Table 4). It is noteworthy that, among these ten best hybrids with negative SCA for EH, six of them (60%) have in its cross at least one line with negative GCA. This demonstrates that the use of lines with negative GCA for EH may contribute to obtain hybrids with lower EH.

Since there was interaction of GCA x E (Table 2), for the character PH in group I (females), the effects of combining ability of these parents were estimated in each environment separately (Table 2). Lines 2, 7, 8, 9, 10, 11, 12 and 14 of group I, had negative GCA estimates, for the five environments, indicating that the additive genetic action of these lines reduces the PH in the crosses they take part in. Line 14 had the best estimates for the character reduction in the environments Itapiranga (-0.238) and Pato Branco (-0.109) and the best estimate of the environment average (-0.200) within the group of females. In Ampére and Frederico Westphalen, the greatest GCA estimates to reduce the character were expressed by line 8 with magnitudes of -0.197 and -0.177, respectively, besides presenting the second best average estimate among the lines (-0.196). In Clevelãndia, the highlight was line 9 (-0.338) (Table 2).

In group II, negative GCA effects were observed for the character PH of lines 1', 2', 5', 6', 7'

(5)

75

and 8'. Line 6 'showed the highest negative estimate for Clevelãndia (-0.544), Itapiranga (-0.368), Pato Branco (-0.170) and Frederico Westphalen (-0.280), and also showed the best average effect (-0.333) to character reduction in the environments. Line 7' had the highest negative estimate for environment of Ampére (-0.307) and the second best average effect among the group of parents (-0.326) (Table 3).

These lines can be identified as the most promising for use in height reduction in hybrid combinations.

For PH, effects were estimated individually for each environment, since the SCA x environment interaction was significant (Table 1). Negative SCA estimates of higher magnitude higher for the character PH were obtained in crossings 15x4' (-2.017), 4x4' (-1.698), 3x3' (-1.341) 1x3' (-1.358), 3x3' (-1.341), 2x4' (-1.160), 12x4' (-1.156), 10x4' (-1.156), 11x4' (-1.155), 10x3' (-1.071), 7x3' (-1.067), 9x3' (-1.063), 8x3' (-1.061) e 14x3' (-1.056) in the five environments (Table 5).

These results indicate a high degree of complementarity between these lines, resulting from high allelic frequencies present in both heterotic groups, which contributed to the reduction of PH and EH. Diallel analysis allows us to choose hybrid combinations with the best SCA, in which at least one of the parent lines have a good GCA performance (Engelsing et al., 2011). In this context, hybrid combinations 8x3' for the environments of Ampére (-0.972) and Frederico Westphalen (-0.872), 14x3' in Itapiranga (-1.155) and Pato Branco (-0.548) and 9x3' in Clevelândia (- 1.677) are highlighted.

Breeding programs aim promising geno- types, particularly with regard to optimal plant height and yield. Short stature hybrids have greater market potential (Ferreira et al., 2008). A time series between hybrids and varieties from 1930 to 2001 highlighted a tendency of reduction of height of ear insertion of about three centimeters per decade (Duvick, 2005). Plants that show reduced stature and height of ear insertion can take advantage of the use of nitrogen fertilizers more efficiently, because the plant's center of gravity is more balanced, reduc- ing lodging and stem breakage and favoring the absorption and translocation of nutrients to grain filling (Sangoi et al., 2002).

Regarding GCA of group I (females) for the characters GY, ED and EL (Table 2), it was found that lines 1, 3, 4, 5, 6, 13 and 15 had positive GCA estimates in the average of the five environments, indicating tendency of increasing additive genetic contribution to these characters in the crosses in which these lines took part. Such lines are noteworthy, since the additive effects are the predictable part of the genetic effects and, therefore, useful for genetic improvement programs (Lee et al., 2005). Lines 15 and 4 stand out with high averages of GCA estimates in the five environments for the characters GY (2.525 and 1.266, respectively), ED (14.494 and 8.077,

respectively) and EL (5.042 and 2.867, respectively), being the lines showing the highest concentrations of alleles with additive effect favorable for increasing these characters. Positive and high value estimates are of great interest in these characters, indicating the average of hybrids involving these lines in question is greater than the overall diallel average.

Analyzing table 3, for group II (male), it is found that lines 3' and 4' were the ones that have contributed positively in increasing GY, ED and EL in hybrid combinations in the average of the five environments. For character GY, estimates were obtained by environment. In the environments of Ampére (2.506), Clevelãndia (3.879), Itapiranga (3.148) and Frederico Westphalen (2.078), line 4' stands out for showing the highest GCA average (2.897) among parents. In turn, line 3' had the highest estimate for the character in the environment of Pato Branco (3.155), revealing the specificity of the line in this environment. For ED and EL, estimates were obtained by the average of the five environments, since there was no significance to C x E.

Line 4' was superior in the studied environments, with the highest overall average of the set of lines, revealing that it is more promising and has high frequency of alleles favorable for these characters.

SCA effect is interpreted as the deviation of the performance of a hybrid combination, compared to what would be expected based on its parents' GCA. Therefore, SCA low absolute values show the hybrid combination behaves as what would be expected based on its parents' GCA, while high absolute values show the behavior of a cross (Hybrid) has higher or lower performance than that expected based on GCA. In fact, high performances coming from SCA, even in the absence of GCA in the parents, directly represents the highest expression of heterosis, coming from different types of dominances and epistases of the parents.

For character GY, SCA effects were estimated for each environment separately, given the significance of the interaction between SCA x environment (Table 1). These results corroborate those obtained by Deitos et al. (2006). Considering all these evaluation environments, the ten best averages of SCA estimates for the character GY were the hybrid combinations obtained from 10x5' (7.693), 3x1' (6.478), 4x7' (5.969), 1x1' (5.947), 4x6' (5.862), 15x2' (5.493), 15x5' (4.742), 9x4' (4.223), 12x3' (4.174) and 11x3' (3.932) (Table 6). Of these ten crossings with the best positive SCA averages, only five hybrids had at least one parent with positive GCA, indicating that, in general, good heterosis performances (SCA) do not always require that one of the parents has good GCA. Hence, the ten best hybrids for SCAs per se were obtained only in three crossings, in which one of the parents has good GCA.

(6)

76

Table 3 - Estimates of the effects of general combining ability (GCA) of eight "male" lines (group II), for the character height of ear insertion (EH), plant height (PH), grain yield of the plot (GY), ear diameter (ED) and ear length (EL) in maize hybrids, for five crop environments. CGF/FAEM/UFPel, Pelotas, 2013.

Characters ⁽¹⁾Environment

Group II (male) Lines

(2) 1' 2' 3' 4' 5' ⁽²⁾6' 7' 8'

EH

Average -0.086 -0.166 0.412 0.439 -0.085 -0.175 -0.171 -0.169

PH

A1 -0.141 -0.304 0.728 0.785 -0.155 -0.305 -0.307 -0.301 A2 -0.276 -0.520 1.235 1.449 -0.289 -0.544 -0.521 -0.534 A3 -0.191 -0.351 0.878 0.914 -0.170 -0.368 -0.366 -0.347 A4 -0.087 -0.163 0.418 0.427 -0.089 -0.170 -0.169 -0.167 A5 -0.150 -0.270 0.642 0.749 -0.151 -0.280 -0.268 -0.271 Average -0.169 -0.322 0.780 0.865 -0.171 -0.333 -0.326 -0.324

GY

A1 -0.549 -0.920 2.442 2.506 -0.435 -1.065 -1.058 -0.921 A2 -0.758 -1.430 3.323 3.879 -0.741 -1.464 -1.348 -1.462 A3 -0.630 -1.072 2.520 3.148 -0.556 -1.101 -1.085 -1.222 A4 -0.675 -1.142 3.155 2.872 -0.486 -1.215 -1.244 -1.266 A5 -0.497 -0.702 1.761 2.078 -0.390 -0.741 -0.815 -0.694 Average -0.622 -1.053 2.640 2.897 -0.522 -1.118 -1.110 -1.113

ED

Average -3.716 -6.841 15.919 19.147 -3.633 -6.933 -6.996 -6.947

EL

Average -1.287 -2.433 5.428 6.566 -1.193 -2.383 -2.362 -2.336

(1) A1-Ampére-PR, A2-Clevelândia-PR, A3-Itapiranga-SC, A4-Pato Branco-PR and A5-Frederico Westphalen-RS; ⁽²⁾Parents.

Table 4 - Estimates of the effects of specific combining ability (SCA) for the character height of ear insertion (EH), ear diameter (ED) and ear length (EL) in maize hybrids, for five crop environments. CGF/FAEM/UFPel, Pelotas, 2013.

Group I Group II (male)

(female) 1' 2' 3' 4' 5' 6' 7' 8'

Height of ear insertion

1 1.025 -0.132 -0.710 0.410 -0.213 -0.123 -0.127 -0.129

2 -0.069 0.011 0.671 -0.594 -0.070 0.020 0.016 0.014

3 0.962 -0.122 -0.700 0.411 -0.203 -0.113 -0.117 -0.119

4 -0.338 -0.258 0.368 -0.863 -0.339 0.813 0.874 -0.256

5 -0.202 -0.122 0.530 0.346 -0.203 -0.113 -0.117 -0.119

6 -0.215 -0.135 0.566 0.389 -0.216 -0.126 -0.130 -0.132

7 -0.063 0.017 -0.561 0.605 -0.064 0.026 0.022 0.019

8 -0.057 0.023 -0.555 0.560 -0.058 0.032 0.028 0.026

9 -0.059 0.021 -0.557 0.575 -0.060 0.030 0.026 0.024

10 -0.070 0.010 -0.568 -0.595 1.176 0.019 0.015 0.013

11 -0.063 0.018 0.626 -0.587 -0.063 0.027 0.022 0.020

12 -0.066 0.015 0.648 -0.590 -0.067 0.023 0.019 0.017

13 -0.218 -0.137 0.545 0.425 -0.218 -0.128 -0.133 -0.135

14 -0.055 0.026 -0.552 0.543 -0.055 0.035 0.030 0.028

15 -0.512 0.765 0.251 -1.036 0.653 -0.422 -0.427 0.729

(7)

77

Table 4 – Cont...

Ear diameter

1 39.723 -5.395 -28.131 18.220 -8.575 -5.306 -5.241 -5.295

2 -2.306 0.825 26.153 -25.133 -2.356 0.914 0.978 0.925

3 40.476 -5.542 -28.278 18.352 -8.723 -5.453 -5.389 -5.442 4 -14.570 -11.440 14.775 -37.398 -14.620 37.748 36.845 -11.340

5 -8.720 -5.590 21.292 18.214 -8.770 -5.500 -5.436 -5.490

6 -8.374 -5.244 21.021 16.409 -8.424 -5.154 -5.090 -5.144

7 -2.338 0.792 -21.943 23.157 -2.388 0.882 0.946 0.892

8 -2.192 0.939 -21.797 22.132 -2.241 1.028 1.093 1.039

9 -2.421 0.709 -22.026 23.738 -2.471 0.799 0.863 0.809

10 -2.455 0.676 -22.060 -25.283 46.753 0.765 0.829 0.775

11 -2.243 0.888 25.710 -25.070 -2.292 0.977 1.042 0.988

12 -2.479 0.652 27.361 -25.306 -2.528 0.741 0.806 0.752

13 -8.762 -5.631 21.220 18.537 -8.812 -5.542 -5.478 -5.531

14 -2.351 0.780 -21.956 23.246 -2.401 0.869 0.933 0.880

15 -20.987 32.580 8.661 -43.814 27.848 -17.767 -17.702 31.181 Ear length

1 14.059 -1.805 -9.663 6.025 -3.015 -1.846 -1.862 -1.892

2 -0.822 0.313 9.332 -8.682 -0.897 0.272 0.256 0.227

3 13.621 -1.625 -9.483 5.381 -2.835 -1.666 -1.682 -1.711

4 -5.093 -3.957 5.056 -12.953 -5.168 12.966 13.193 -4.044

5 -3.033 -1.898 7.369 6.550 -3.108 -1.939 -1.955 -1.985

6 -2.925 -1.790 7.132 6.138 -3.000 -1.831 -1.847 -1.877

7 -0.816 0.319 -7.539 8.154 -0.891 0.278 0.262 0.232

8 -0.751 0.385 -7.473 7.696 -0.826 0.344 0.327 0.298

9 -0.893 0.243 -7.616 8.691 -0.968 0.202 0.185 0.156

10 -0.775 0.360 -7.498 -8.636 15.652 0.319 0.303 0.274

11 -0.846 0.290 9.498 -8.706 -0.920 0.249 0.233 0.203

12 -0.751 0.384 8.837 -8.612 -0.826 0.343 0.327 0.297

13 -2.855 -1.719 7.178 5.669 -2.930 -1.760 -1.777 -1.806

14 -0.853 0.282 -7.576 8.412 -0.928 0.241 0.225 0.196

15 -7.267 10.218 2.446 -15.127 10.659 -6.173 -6.189 11.433

Table 5 - Estimates of the effects of specific combining ability (SCA) for the character plant height (PH) in maize hybrids, for five crop environments. CGF/FAEM/UFPel, Pelotas, 2013.

Group I (female)

Group II (male) Plant Height

(1)Environment 1' 2' 3' 4' 5' 6' 7' 8'

1

A1¹ 1.856 -0.235 -1.266 0.733 -0.384 -0.233 -0.232 -0.238 A2 3.247 -0.424 -2.179 1.244 -0.655 -0.400 -0.423 -0.410 A3 2.012 -0.272 -1.500 0.998 -0.452 -0.255 -0.256 -0.275 A4 0.987 -0.126 -0.707 0.411 -0.200 -0.120 -0.121 -0.123 A5 1.635 -0.226 -1.138 0.738 -0.344 -0.215 -0.227 -0.224 Average 1.947 -0.256 -1.358 0.825 -0.407 -0.245 -0.252 -0.254

2

A1 -0.124 0.039 1.130 -1.051 -0.111 0.040 0.042 0.035 A2 -0.209 0.035 2.160 -1.934 -0.196 0.059 0.036 0.049 A3 -0.137 0.022 1.421 -1.243 -0.158 0.039 0.037 0.019 A4 -0.069 0.008 0.673 -0.583 -0.067 0.014 0.013 0.011 A5 -0.089 0.031 1.031 -0.988 -0.088 0.041 0.029 0.032 Average -0.126 0.027 1.283 -1.160 -0.124 0.039 0.031 0.029

3

A1 1.852 -0.236 -1.267 0.742 -0.385 -0.234 -0.233 -0.239 A2 2.984 -0.400 -2.156 1.364 -0.631 -0.376 -0.399 -0.386 A3 2.020 -0.241 -1.470 0.807 -0.422 -0.224 -0.226 -0.245 A4 0.917 -0.109 -0.690 0.378 -0.183 -0.103 -0.104 -0.106 A5 1.537 -0.209 -1.121 0.735 -0.327 -0.198 -0.210 -0.207 Average 1.862 -0.239 -1.341 0.805 -0.390 -0.227 -0.234 -0.236

(8)

78

4

A1 -0.617 -0.455 0.524 -1.544 -0.604 1.590 1.565 -0.458 A2 -1.124 -0.880 1.157 -2.849 -1.111 2.677 2.996 -0.866 A3 -0.683 -0.523 0.775 -1.788 -0.704 1.714 1.737 -0.527 A4 -0.314 -0.237 0.285 -0.828 -0.312 0.812 0.828 -0.234 A5 -0.584 -0.464 0.539 -1.483 -0.583 1.436 1.602 -0.463 Average -0.664 -0.512 0.656 -1.698 -0.663 1.646 1.745 -0.509

5

A1 -0.370 -0.207 0.911 0.643 -0.356 -0.206 -0.204 -0.211 A2 -0.660 -0.416 1.763 1.170 -0.647 -0.393 -0.415 -0.402 A3 -0.404 -0.245 1.030 0.748 -0.425 -0.228 -0.229 -0.248 A4 -0.197 -0.120 0.549 0.307 -0.194 -0.114 -0.115 -0.116 A5 -0.332 -0.212 0.828 0.672 -0.330 -0.201 -0.213 -0.210 Average -0.392 -0.240 1.016 0.708 -0.391 -0.228 -0.235 -0.238

6

A1 -0.408 -0.246 1.020 0.765 -0.395 -0.244 -0.243 -0.249 A2 -0.655 -0.411 1.653 1.250 -0.642 -0.388 -0.410 -0.397 A3 -0.468 -0.309 1.305 0.859 -0.489 -0.292 -0.293 -0.312 A4 -0.194 -0.117 0.508 0.332 -0.192 -0.111 -0.112 -0.114 A5 -0.351 -0.231 0.959 0.654 -0.349 -0.220 -0.232 -0.229 Average -0.415 -0.263 1.089 0.772 -0.413 -0.251 -0.258 -0.260

7

A1 -0.110 0.053 -0.979 0.973 -0.096 0.054 0.056 0.049 A2 -0.206 0.038 -1.718 1.929 -0.193 0.061 0.038 0.052 A3 -0.115 0.044 -1.185 1.231 -0.136 0.061 0.059 0.041 A4 -0.056 0.021 -0.561 0.573 -0.054 0.027 0.026 0.024 A5 -0.103 0.017 -0.895 1.021 -0.101 0.027 0.016 0.019 Average -0.118 0.034 -1.067 1.146 -0.116 0.046 0.039 0.037

8

A1 -0.103 0.060 -0.972 0.924 -0.089 0.061 0.063 0.056 A2 -0.215 0.029 -1.727 1.992 -0.203 0.052 0.029 0.043 A3 -0.102 0.057 -1.172 1.140 -0.123 0.074 0.072 0.054 A4 -0.057 0.020 -0.561 0.579 -0.055 0.026 0.025 0.023 A5 -0.080 0.040 -0.872 0.860 -0.078 0.051 0.039 0.042 Average -0.111 0.041 -1.061 1.099 -0.110 0.053 0.046 0.043

9

A1 -0.131 0.032 -1.000 1.120 -0.117 0.033 0.035 0.028 A2 -0.165 0.079 -1.677 1.642 -0.153 0.102 0.079 0.093 A3 -0.109 0.051 -1.178 1.186 -0.130 0.068 0.066 0.047 A4 -0.067 0.010 -0.571 0.649 -0.065 0.016 0.015 0.013 A5 -0.095 0.025 -0.887 0.966 -0.094 0.035 0.023 0.026 Average -0.113 0.039 -1.063 1.113 -0.112 0.051 0.044 0.042

10

A1 -0.134 0.029 -1.003 -1.061 2.082 0.030 0.032 0.025 A2 -0.173 0.071 -1.685 -1.898 3.435 0.094 0.071 0.085 A3 -0.152 0.007 -1.221 -1.258 2.574 0.024 0.023 0.004 A4 -0.054 0.023 -0.558 -0.567 1.072 0.029 0.028 0.027 A5 -0.095 0.024 -0.888 -0.994 1.868 0.035 0.023 0.026 Average -0.122 0.031 -1.071 -1.156 2.206 0.043 0.035 0.033

11

A1 -0.138 0.024 1.230 -1.065 -0.125 0.026 0.027 0.021 A2 -0.188 0.056 2.015 -1.913 -0.175 0.079 0.056 0.070 A3 -0.112 0.047 1.248 -1.218 -0.134 0.064 0.062 0.043 A4 -0.064 0.013 0.638 -0.578 -0.062 0.019 0.018 0.016 A5 -0.102 0.018 1.121 -1.001 -0.100 0.028 0.017 0.020 Average -0.121 0.031 1.250 -1.155 -0.119 0.043 0.036 0.034

12

A1 -0.126 0.036 1.145 -1.053 -0.113 0.038 0.040 0.033 A2 -0.194 0.050 2.056 -1.919 -0.181 0.073 0.051 0.064 A3 -0.137 0.023 1.417 -1.242 -0.158 0.040 0.038 0.019 A4 -0.058 0.018 0.597 -0.572 -0.056 0.025 0.024 0.022 A5 -0.096 0.023 1.081 -0.995 -0.095 0.034 0.022 0.025 Average -0.122 0.030 1.259 -1.156 -0.120 0.042 0.035 0.033

(9)

79

13

A1 -0.403 -0.240 1.085 0.667 -0.389 -0.239 -0.237 -0.244 A2 -0.655 -0.411 1.563 1.340 -0.642 -0.388 -0.410 -0.397 A3 -0.445 -0.285 1.078 0.945 -0.466 -0.268 -0.270 -0.289 A4 -0.222 -0.145 0.574 0.432 -0.219 -0.139 -0.140 -0.141 A5 -0.340 -0.220 0.893 0.654 -0.338 -0.209 -0.221 -0.218 Average -0.413 -0.260 1.039 0.807 -0.411 -0.249 -0.256 -0.258

14

A1 -0.121 0.041 -0.990 1.052 -0.108 0.043 0.045 0.038 A2 -0.201 0.043 -1.713 1.895 -0.189 0.066 0.043 0.056 A3 -0.086 0.073 -1.155 1.025 -0.107 0.090 0.089 0.070 A4 -0.044 0.033 -0.548 0.486 -0.041 0.039 0.038 0.037 A5 -0.083 0.037 -0.875 0.881 -0.081 0.048 0.036 0.039 Average -0.107 0.045 -1.056 1.068 -0.105 0.057 0.050 0.048

15

A1 -0.921 1.305 0.433 -1.847 1.190 -0.757 -0.755 1.352 A2 -1.586 2.540 0.487 -3.311 2.184 -1.319 -1.342 2.347 A3 -1.083 1.551 0.607 -2.189 1.330 -0.907 -0.909 1.600 A4 -0.506 0.711 0.373 -1.019 0.627 -0.423 -0.424 0.661 A5 -0.822 1.348 0.226 -1.720 1.040 -0.691 -0.703 1.322 Average -0.984 1.491 0.425 -2.017 1.274 -0.819 -0.826 1.456

Table 6 - Estimates of the effects of specific combining ability (SCA) for the character gain yield of the plot (GY) in maize hybrids, for five crop environments. CGF/FAEM/UFPel, Pelotas, 2013.

Group I (female)

Group II (male) Grain Yield

(1)Environment 1' 2' 3' 4' 5' 6' 7' 8'

1

A1 5.461 -0.748 -4.110 2.592 -1.234 -0.603 -0.611 -0.748 A2 7.836 -1.140 -5.893 4.459 -1.828 -1.105 -1.221 -1.108 A3 6.078 -1.093 -4.685 4.394 -1.609 -1.064 -1.080 -0.943 A4 6.931 -1.142 -5.439 4.574 -1.798 -1.068 -1.040 -1.018 A5 3.428 -0.554 -3.017 2.526 -0.866 -0.515 -0.441 -0.562 Average 5.947 -0.935 -4.629 3.709 -1.467 -0.871 -0.879 -0.876

2

A1 -0.275 0.096 3.327 -3.330 -0.390 0.241 0.234 0.097 A2 -0.543 0.129 5.783 -5.180 -0.560 0.163 0.047 0.161 A3 -0.255 0.187 3.675 -4.033 -0.329 0.216 0.200 0.337 A4 -0.471 -0.004 4.866 -4.018 -0.660 0.069 0.098 0.120 A5 -0.126 0.079 2.603 -2.702 -0.233 0.118 0.191 0.070 Average -0.334 0.098 4.051 -3.853 -0.434 0.162 0.154 0.157

3

A1 5.930 -0.899 -4.261 3.028 -1.385 -0.754 -0.761 -0.898 A2 8.765 -1.004 -5.757 2.714 -1.693 -0.969 -1.086 -0.972 A3 6.233 -1.032 -4.624 3.875 -1.548 -1.003 -1.019 -0.882 A4 7.139 -0.860 -5.158 2.678 -1.516 -0.787 -0.758 -0.737 A5 4.321 -0.514 -2.978 1.398 -0.826 -0.475 -0.402 -0.523 Average 6.478 -0.862 -4.555 2.739 -1.394 -0.798 -0.805 -0.802

4

A1 -1.811 -1.440 1.890 -4.867 -1.926 4.745 4.850 -1.440 A2 -3.040 -2.369 2.532 -7.677 -3.057 7.159 8.790 -2.337 A3 -2.366 -1.923 1.705 -6.144 -2.439 6.359 6.583 -1.774 A4 -2.650 -2.183 2.747 -6.197 -2.839 6.791 6.389 -2.059 A5 -1.552 -1.347 2.550 -4.128 -1.659 4.259 3.232 -1.356 Average -2.284 -1.852 2.285 -5.803 -2.384 5.862 5.969 -1.793

5

A1 -1.216 -0.845 3.713 1.929 -1.330 -0.700 -0.707 -0.844 A2 -1.832 -1.160 4.394 3.944 -1.849 -1.126 -1.242 -1.128 A3 -1.214 -0.772 3.656 1.741 -1.288 -0.743 -0.759 -0.622 A4 -1.435 -0.968 5.195 1.438 -1.624 -0.895 -0.866 -0.844 A5 -0.824 -0.619 2.565 1.521 -0.931 -0.580 -0.506 -0.627 Average -1.304 -0.873 3.905 2.114 -1.404 -0.808 -0.816 -0.813

(10)

80

6

A1 -1.176 -0.805 3.180 2.222 -1.290 -0.660 -0.667 -0.804 A2 -1.695 -1.024 3.997 3.521 -1.712 -0.989 -1.105 -0.992 A3 -1.351 -0.908 3.953 2.264 -1.424 -0.879 -0.895 -0.759 A4 -1.331 -0.864 4.106 1.902 -1.520 -0.791 -0.762 -0.740 A5 -0.822 -0.617 1.627 2.450 -0.929 -0.578 -0.505 -0.626 Average -1.275 -0.843 3.372 2.472 -1.375 -0.779 -0.787 -0.784

7

A1 -0.255 0.116 -3.246 3.123 -0.370 0.261 0.254 0.117 A2 -0.426 0.246 -4.507 4.410 -0.443 0.280 0.164 0.278 A3 -0.389 0.053 -3.539 3.986 -0.463 0.082 0.066 0.203 A4 -0.321 0.146 -4.151 4.099 -0.510 0.219 0.248 0.270 A5 -0.194 0.011 -2.452 2.758 -0.301 0.050 0.124 0.003 Average -0.317 0.115 -3.579 3.675 -0.417 0.179 0.171 0.174

8

A1 -0.222 0.149 -3.213 2.895 -0.337 0.294 0.286 0.149 A2 -0.439 0.233 -4.520 4.497 -0.456 0.268 0.151 0.265 A3 -0.435 0.007 -3.585 4.307 -0.509 0.036 0.020 0.157 A4 -0.250 0.217 -4.080 3.603 -0.439 0.290 0.319 0.341 A5 -0.007 0.198 -2.265 1.451 -0.114 0.237 0.310 0.190 Average -0.271 0.161 -3.533 3.351 -0.371 0.225 0.217 0.220

9

A1 -0.309 0.062 -3.300 3.502 -0.424 0.207 0.199 0.062 A2 -0.539 0.132 -4.621 5.203 -0.557 0.167 0.050 0.164 A3 -0.470 -0.028 -3.620 4.552 -0.544 0.001 -0.015 0.122 A4 -0.475 -0.008 -4.305 5.178 -0.664 0.065 0.094 0.116 A5 -0.183 0.022 -2.441 2.682 -0.290 0.061 0.135 0.014 Average -0.395 0.036 -3.657 4.223 -0.496 0.100 0.093 0.096

10

A1 -0.370 0.001 -3.361 -3.425 6.869 0.146 0.139 0.002 A2 -0.474 0.198 -4.555 -5.111 9.362 0.233 0.116 0.230 A3 -0.518 -0.076 -3.668 -4.296 8.595 -0.047 -0.063 0.073 A4 -0.548 -0.080 -4.378 -4.095 9.044 -0.007 0.022 0.043 A5 -0.104 0.101 -2.362 -2.679 4.596 0.140 0.214 0.093 Average -0.403 0.029 -3.665 -3.921 7.693 0.093 0.085 0.088

11

A1 -0.233 0.138 3.036 -3.289 -0.348 0.283 0.275 0.138 A2 -0.539 0.132 5.759 -5.177 -0.557 0.167 0.050 0.164 A3 -0.196 0.246 3.264 -3.974 -0.270 0.275 0.259 0.396 A4 -0.459 0.008 4.785 -4.007 -0.648 0.081 0.110 0.131 A5 -0.157 0.048 2.818 -2.732 -0.264 0.087 0.160 0.040 Average -0.317 0.114 3.932 -3.836 -0.417 0.179 0.171 0.174

12

A1 -0.384 -0.013 4.092 -3.440 -0.499 0.132 0.124 -0.013 A2 -0.455 0.216 5.170 -5.093 -0.473 0.251 0.135 0.248 A3 -0.360 0.082 4.410 -4.138 -0.434 0.111 0.095 0.232 A4 -0.370 0.097 4.162 -3.918 -0.559 0.170 0.199 0.220 A5 -0.188 0.017 3.034 -2.763 -0.295 0.056 0.130 0.009 Average -0.351 0.080 4.174 -3.870 -0.452 0.144 0.137 0.139

13

A1 -1.333 -0.962 3.876 2.471 -1.448 -0.817 -0.825 -0.962 A2 -1.779 -1.107 4.433 3.584 -1.796 -1.072 -1.189 -1.075 A3 -1.405 -0.963 4.425 2.117 -1.479 -0.934 -0.950 -0.813 A4 -1.398 -0.931 3.415 2.995 -1.587 -0.858 -0.829 -0.807 A5 -0.905 -0.700 1.737 2.839 -1.012 -0.661 -0.588 -0.709 Average -1.364 -0.933 3.577 2.801 -1.464 -0.868 -0.876 -0.873

14

A1 -0.264 0.107 -3.255 3.187 -0.379 0.252 0.244 0.107 A2 -0.494 0.177 -4.576 4.888 -0.512 0.212 0.095 0.209 A3 -0.152 0.290 -3.302 2.330 -0.226 0.319 0.303 0.439 A4 -0.228 0.239 -4.059 3.451 -0.417 0.312 0.341 0.362 A5 -0.155 0.050 -2.413 2.489 -0.262 0.089 0.162 0.041 Average -0.259 0.173 -3.521 3.269 -0.359 0.237 0.229 0.232

15

A1 -3.542 5.042 1.633 -6.598 4.490 -3.026 -3.034 5.036 A2 -4.345 6.340 2.361 -8.982 6.131 -3.639 -3.755 5.892 A3 -3.202 5.927 1.935 -6.981 3.964 -2.731 -2.747 3.836 A4 -4.133 6.334 2.296 -7.681 5.738 -3.593 -3.564 4.604 A5 -2.534 3.824 0.995 -5.109 3.386 -2.290 -2.216 3.943 Average -3.551 5.493 1.844 -7.070 4.742 -3.056 -3.063 4.662

(11)

81

Hybrid combinations that showed increase for the character ED were 10x5' (46.753), 3x1' (40.476), 1x1' (39.723), 4x6' (37.748), 4x7' (36.845), 15x2' (32.580), 15x8' (31.181), 15x5' (27.848), 12x3' (27.361), 2x3' (26.153), 11x3' (25.710) and 9x4' (23.738), which also had the highest ear length values (EL): 10x5' (15.652), 1x1' (14.059), 3x1' (13.621), 4x7' (13.193), 4x6' (12.966), 15x8' (11.433), 15x5' (10.659), 15x2' (10.218), 11x3' (9.498), 2x3' (9.332), 12x3' (8.837) e 9x4' (8.691) (Table 4). This result proves the correlation between these two variables as these crosses were the best for both characters. For these two variables, lines 3' and 15 participated in three of the best GCA. In these results, it can be seen that rarely a line that generated a good SCA in a hybrid will take part of other hybrids that also have good SCA, since, from the total of seventeen lines composing the twelve best SCA for ED and EL, only two lines (3 'and 15), i.e. 11.74%, participated as parents of three superior hybrids. Data agree with those obtained by Divan et al. (2013), where SCA was the main responsible for the expression of the characters ear diameter and length.

Allied to these characters directly associated with grain yield, grain yield in a maize breeding program is a decisive parameter for the success of cultivars (Engelsing et al., 2011). So the joint selection of agronomically important characters, allied with the ability of these lines to result in hybrids with high grain yield rates, becomes an important strategy in the search and identification of superior lines that will be kept in active germplasm for breeding programs.

Conclusions

Female lines (group I), obtained from the recombination of commercial single hybrids with high grain yield, only showed interaction between GCA x environment for PH, have concentration of genes/alleles with additive genetic action that do not undergo modulation with the changes in crop environment.

Male lines (group II), obtained from the recombination of commercial triple hybrids with characters of rusticity, showed interaction between GCA x environment for PH and GY of the plot, which may indicate that lines obtained by the interbreeding of current triple hybrids for these characters have higher concentration of genes of additive action that undergo modulation with changes of crop environment, compared with lines obtained from recombination of single hybrids.

SCA x E interactions were reduced, appar- ently there is only one modulation of the environment x SCA interaction for PH and GY, indicating that, for the other characters, genetic actions of dominance and epistasis do not undergo modulation by changes of crop environment.

Although PH have positive interaction with environment, the variable EH did not keep the same

standard, indicating that EH is indifferent to changes of PH due to the change of crop environment.

In most cases, hybrids with the best SCA values did not have lines with good GCA in its cross, distorting the common idea that, in order to obtain hybrids with good SCA results, it is necessary that at least one of their parents has a good GCA.

Acknowledgement

The authors thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Coordination for the Improvement of Higher Educa- tion Personnel) (CAPES), for granting the doctoral scholarship of the first author, and the company KSP Sementes Ltda., for providing the bank of inbred lines and hybrids used in this study. They also thank CNPq and FAPERGS.

References

Barreto RR, Scapim CA, Amaral Júnior AT, Araújo Rodovalho M, Vieira RA, Schuelter AR (2012). Avaliação da capacidade de combinação de famílias S2 de milho-pipoca por meio de diferentes testadores. Semina, 33(3):873-890.

CONAB - Companhia Nacional de Abastecimento (2014) Acompanhamento da Safra Brasileira.

Disponível em:

<http://www.conab.gov.br/OlalaCMS/uploads/arqui- vos/14_05_08_10_11_00_boletim_

graos_maio_2014.pdf> (Acesso em 05 mai. 2014).

Cruz CD, Regazzi AJ, Carneiro PCS (2012). Mode- los biométricos aplicados ao melhoramento gené- tico. 4ª ed. Viçosa: UFV, 514p.

Cruz CD (2013). GENES - a software package for analysis in experimental statistics and quantitative genetics. Acta Scientiarum. Agronomy 35(3):271- 276.

Deitos A, Arnhold E, Mora F, Miranda GV (2006).

Yield and combining ability of maize cultivars under different ecogeographic conditions. Crop Breeding and Applied Biotechnology 6(3):222-226.

Divan R, Khorasani SK, Ebrahimi A, Bakhtiari S (2013). Study on combining ability and gene effects in inbred lines and single cross hybrids of forage maize (Zea mays L.). International Journal of Agronomy and Plant Production 4(6):1290-1297.

Duvick DN (2005). The Contribution of Breeding to Yield Advances in maize (Zea mays L.). Advances in Agronomy 86: 83-145.

Engelsing MJ, Rozzetto DS, Coimbra JLM, Zanin CG, Guidolin AF (2011). Capacidade de combinação em milho para resistência a Cercospora zeae-maydis.

Revista Ciência Agronômica 42(1):232-241.

(12)

82

Ferreira EA, Guimarães PS, Silva RM, Paterniani MEGZ (2008). Capacidade combinatória de linhagens de milho de germoplasma tropical e temperado e heterose dos híbridos simples. Revista Biociências 14(1).

Griffing B (1956). Concept of general and specific combining ability in relation to diallel crossing sys- tems. Australian Journal Biology Science. East 9:463-493.

Hallauer AR, Carena JM, Miranda Filho JB (2010).

Quantitative genetics in maize breeding. New York:

Springer, 500p.

Izhar T, Chakraborty M (2013). Combining ability and heterosis for grain yield and its components in maize inbreds over environments (Zea mays L.). African Journal of Agricultural Research 8(25):3276-3280.

Lee EA, Ahmadzadeh A, Tollenaar M (2005).

Quantitative genetic analysis of the physiological processes underlying maize grain yield. Crop science 45(3):981-987.

Oliboni R, Faria MV, Neumann M, Resende JTV, Battistelli GM, Tegoni RG, Oliboni DF (2013). Análise dialélica na avaliação do potencial de híbridos de milho para a geração de populações-base para obtenção de linhagens. Semina 34(1):7-18.

Pinto RJB, Kvitschal MV, Scapim CA, Fracaro M, Bignotto LS, Neto ILS (2007). Análise dialélica parcial de linhagens de milho-pipoca. Revista Brasileira de Milho e Sorgo 6(3):325-337.

Rodrigues F, Von Pinho RG, Albuquerque CJB, Faria Filho EM, Goulart JC (2009). Capacidade de combinação entre linhagens de milho visando à pro- dução de milho verde. Bragantia 68(1):75-84.

Sangoi L, Almeida ML, Silva PRF, Argenta G (2002).

Bases morfofisiológicas para maior tolerância dos híbridos modernos de milho a altas densidades de plantas. Bragantia 61:101-110.

Seifert AL, Carpentieri-Pípolo V, Ferreira JM, Gerage AC (2006). Análise combinatória de populações de milho pipoca em topcrosses. Pesquisa Agropecuária Brasileira 41(5):771-778.

Souza Neto IL, Pinto RJB, Scapim CA, Jobim CC, Figueiredo AST, Bignotto LS (2015). Análise dialélica e depressão endogâmica de híbridos forra- geiros de milho para características agronômicas e de qualidade bromatológica. Bragantia, Campinas 74(1): 42-49.

Vencovsky R, Barriga P (1992). Genética biométrica no fitomelhoramento. Ribeirão Preto: Sociedade Brasileira de Genética, 496p.