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1609 
Original Article 

Biosci. J., Uberlândia, v. 31, n. 6, p. 1609-1617, Nov./Dec. 2015 

GENETIC VARIABILITY AND YIELD POTENTIAL OF THREE 
SEMIEXOTIC MAIZE (Zea mays L.) POPULATIONS 

 
VARIABILIDADE GENÉTICA E POTENCIAL PRODUTIVO EM TRÊS 

POPULAÇÕES SEMIEXÓTICAS DE MILHO (Zea mays L.) 
 

Aurilene Santos OLIVEIRA
1
; Edésio Fialho dos REIS

2
; Jose Branco de MIRANDA FILHO

3
;  

Udenys Cabral MENDES
4
; Luana de Oliveira RODRIGUES

5
 

1. Doutoranda em Agronomia, Universidade Federal de Uberlândia – UFU, Uberlândia, MG, Brasil; 2. Professor Associado 
III, Programa de Pós Graduação em Agronomia, Universidade Federal de Goiás – UFG, Jataí, GO, Brasil; 3. Professor 

Titular, Programa de Pós Graduação em Genética e Melhoramento de Plantas, Universidade de São Paulo – 
ESALQ/USP, Piracicaba, SP, Brasil; 4. Doutorando em Agronomia, Universidade Estadual Paulista – UNESP, 

Jaboticabal, SP, Brasil; 5. Ma. Eng. Agrônoma, Syngenta, Uberlândia, MG, Brasil. aurilene.s.oliveira@hotmail.com 
 

ABSTRACT: The rapid increase of the maize crop in the last decades in Brazil, mainly in the Central West 
region, has encouraged the second crop (usually maize after soybean) in the same year. For that reason the need for the 
exploitation of new sources of germplasm seems to be apparent to attend the challenge to create new cultivars (populations 
or hybrids) adapted to the extremely varying environments. Following this principle, the objective of the present work was 
directed to the study of genetic variability and yield potential of three semiexotic populations (CRE-01, CRE-02, CRE-03) 
under the condition of second crop in the Southwest region of the State of Goiás (Brazil). In addition, one cycle of 
recurrent selection with half-sib families was completed in each population. Half-sib families from each population (200, 
180 and 180, respectively) were evaluated in completely randomized block experiments with three replications in Jataí 
(GO). Parameters estimates were obtained for ear yield (EY), grain yield (GY), plant height (PH), ear height (EH), ear 
length (EL) and ear diameter (ED). The population means for GY were 5.68 t/ha, 5.83 t/ha and 5.83 t/ha, which were 
around 70% of the hybrid check. The coefficients of heritability (family mean basis) varied from 0.36 to 0.70; 0.47 to 0.69; 
and 0.39 to 0.68 for the respective populations. Estimates of the additive genetic variance for grain yield (g/plant) were 
316.1, 266.4 and 258.4; and the expected gain from selection were 11.8%, 10.1% and 9.3%, respectively.  

 

PALAVRAS-CHAVE: Exotic germplasm. Genetic parameters. Recurrent selection. Zea mays. 
 

INTRODUCTION 
 

The acreage of the maize crop in Brazil has 
increased spectacularly in the last decades, thus 
creating incentives for a second crop (usually maize 
after soybean) in many important agricultural areas. 
Such expansion was followed by a better use of 
modern technologies thus allowing to reach higher 
levels of productivity. The acreage for second crop 
maize increased from 356 thousand hectares in 1990 
to approximately 1.5 million ha in 1995 
(TSUNESHIRO; OKAWA, 1996), reaching 9 
million ha and producing 46.2 million tons in the 
last year (2012/2013); for comparison, the first 
(normal) crop covered 7 million ha producing 35.2 
million tons. The evolution of the second crop was 
from 24% in 2001/2001 to 56% in the last year. The 
highest production of the second crop maize is 
concentrated in the Central West region, represented 
by the states of Mato Grosso, Mato Grosso do Sul 
and Goiás, that together cover around 67% of the 
second crop production of corn (CONAB, 2013). 

Even cognizant on the importance of the 
maize crop (normal and second crop) expansion, 
other subjects must be taken into account in order to 
maximize its production and productivity. One 

important point is the appropriate choice and use of 
the available germplasm that, by the way, must be in 
accordance with the objectives of the breeding 
program. In this sense, broadening the genetic base, 
by exploiting new sources of germplasm (varieties, 
populations, composites, synthetics, races, etc.), 
including exotics, may be a recommended strategy 
for the conditions of the vast array of environments 
like those occurring in Brazil.  Exotic germplasm 
has largely contributed to increase the variability 
and the efficiency of breeding programs for the 
development of cultivars (MIRANDA FILHO, 
1992; REGITANO NETO et al., 1997; SANTOS et 
al., 2000). The development of commercial hybrids 
initiated with local germplasm represented by old 
varieties such as Cateto and Dente Paulista. After 
that an extraordinary advance occurred with the 
introduction of exotic germplasm, mainly Tuxpeño 
and related races of Mexico and Central America 
that largely contributed for the development of high 
yielding semident hybrids (MIRANDA FILHO; 
VIÉGAS, 1987). The importance of the introduction 
of the race Tuxpeño for the maize breeding in Brazil 
was stressed by Paterniani (1990). Several other 
introductions have contributed to the maize breeding 
programs along the time. In fact, several authors 

Received: 26/01/15 
Accepted: 10/06/15 



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Biosci. J., Uberlândia, v. 31, n. 6, p. 1609-1617, Nov./Dec. 2015 

have long been emphasized the importance of 
incorporation of exotic germplasm in maize 
breeding programs (NASS et al., 2001), but the 
introductions have been below the acceptable level 
of adaptation, thus making difficult to attain the 
desirable objectives. Nevertheless, some 
experiences have been accumulated and surely will 
contribute to overcome inherent obstacles 
(PATERNIANI, 1990; TATER et al., 2004; 
GOODMAN 2005) in Brazil, most of the introduced 
germplasm has been from tropical origin, which 
makes amenable the problem of adaptation. 

After incorporation or introgression of the 
exotic germplasm, the next phase is to establish 
means to get knowledge on the genetic properties of 
the new population, particularly on the genetic 
variability of important quantitative traits that are in 
some extent influenced by the environmental effect. 
In this sense, the additive genetic variance, the 
coefficient of heritability and the expected gain 
from selection are among the most important 
parameters that will provide information on the 
genetic structure of the breeding population 
(VENCOVSKY, 1987; FALCONER, 1981; CRUZ, 
2005; HALLAUER et al., 2010). There are several 
genetic designs that can be used to estimate the 
genetic variance and its components (HALLAUER 
et al., 2010). However, the use of half-sib families 
has been commonly used for that purpose in Brazil 
(VENCOVSKY et al., 1988). Several other reports 
have corroborated this fact (CARVALHO et al., 
2007; ANDRADE; MIRANDA FILHO, 2008; 
SOUZA et al., 2009; LIMA NETO; SOUZA 
JÚNIOR, 2009; FALUBA et al. 2010; KIST et al., 
2010; CANDIDO et al., 2011). 

The objective of this work was to evaluate 
the genetic variability and yield potential of three 
semiexotic populations for their use in recurrent 
selection programs, toward the development of 
germplasm specially adapted to the environmental 
conditions of the Southwestern region of the State of 
Goías. 

 
MATERIAL AND METHODS 

 
A sample of 682 inbred (S4) lines previously 

selected for resistance to corn stunt complex were 
introduced from CIMMYT (Centro Internacional de 
Mejoramiento de Maíz y Trigo, Colombia). A 
selected sample of 51 lines was crossed with three 
local testers: P-3041, represented by the F2 
generation of the commercial hybrid (Pioneer 
HyBred Seeds); CMS-14C, an open pollinated 
population derived from Pool-25 (CIMMYT, 
Mexico) and released by CNPMS/EMBRAPA; and 

ESALQ-PB23, a broad base population obtained 
from the cross ESALQ-PB2 (dent type) and 
ESALQ-PB3 (flint type). After evaluation, a sample 
of testcrosses representing each tester was 
intercrossed to develop three populations: CRE-01 ≡ 
38 lines x P-3041; CRE-02 ≡ 39 lines x CMS-14C; 
CRE-02 ≡ 32 lines x ESALQ-PB23. After the 
synthesis of the three semiexotic populations (CRE-
01, CRE-02, CRE-03) samples of half-sib families 
of sizes 50, 70 and 50, respectively, were evaluated 
in Jataí (GO) in 2008. A mild selection with 
intensities 13/50, 18/70, and 11/50 was applied and 
the recombined samples of the selected families 
represent the base populations in the present project. 
Isolated blocks from each population were used to 
generate half-sib families by random open 
pollination. The number of families were 200, 180 
and 180 in the sequence of populations, which were 
divided into four experiments of 50, 45 and 45 
families, respectively. The yield trials were in 
completely randomized blocks with three 
replications in one location (Farm Três Fronteiras, 
region of Jataí, GO). Plots were 4.0m long spaced 
0.90m apart with 20 plants per plot after thinning. 
The following traits were analyzed: PH – plant 
height (cm), EH – ear height (cm), EL – ear length 
(cm), ED – ear diameter (cm), DR – general disease 
resistance (notes: 1 – resistant to 9 – susceptible), 
EY – total ear weight (g/plot) and GY – grain 
weight (g/plot); both EY and GY were corrected by 
the linear regression of yield on the number of ears 
per plot, according to methodology suggested by 
Miranda Filho, J.B. (apud VENCOVSKY; 
BARRIGA, 1992). One commercial hybrid (DAS 
2B-710) was used as check, intercalated at ten plots 
in each block. The analyses of variance were 
performed according to the model  Yij = m + fi + bj 
+ eij where Yij is the experimental unit referring to 
the ith family in the jth block, represented by plot 
total  (EY and GY) or sample means of five plants 
(PH, EH, EL, ED).  In the model, m is the general 
mean, fi is the random effect of the i

th family, bj is 
the random effect of the jth block, and eij is the error 
term (random effect) for plots. For the purposes of 
this work, the following expectations are of interest: 

E(fi) = E(eij) = 0, E(
2
if ) = 

2
fσ (genetic variance 

among half-sib families), and  E(
2
ije )= σ

2 (plot-to-

plot error variance). In the analysis of variance the 
mean squares for Families and Error have the 

following expected values: E(Mf) = σ
2  + 3

2
fσ  and  

E(Me) = σ
2. Table 1 shows the procedures for 

estimating parameters in populations. 



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Biosci. J., Uberlândia, v. 31, n. 6, p. 1609-1617, Nov./Dec. 2015 

Table 1. Formulas for the estimation of quantitative parameters in populations represented by random samples 
of half-sib families. 

Parameters Estimates 

General mean  m0 = IJ
1

ΣYij 

Phenotypic variance among half-sib family means 
2
HSσ̂ = 3

1
Mf  

Genetic variance among HS families  
2
fσ̂ = 3

1
(Mf – Me) 

Additive genetic variance (only for HS) 2
Aσ̂ = 4 

2
fσ̂  

Error variance 2σ̂  = Me 

Coefficient of heritability (family mean  basis) 2
fh = (Mf – Me)/ Mf 

Coefficient of variation  CV%= 100 eM /m 

Genetic coefficient of variation CVg% = 100 fσ̂ /m 

Index of variation  θ = CVg/CV 

Expected gain from selection Gs = ds. 
2
fh  

[ds = ms – m0: differential of selection where ms is the mean of the selected sample for yield; for any other trait (x), ms is the mean of x in 
the same sample selected for yield]. 
 
RESULTS AND DISCUSSION  

 
The analysis of variance for all traits in the 

three semiexotic populations showed significance (F 
test; P < 0.01) for the variation among families 
(Table 2). The coefficients of variations were in the 
range of 4.0% (ear diameter) to 11.1% (grain yield). 
The set of means for ear yield (t/ha) and grain yield 
(t/ha) in the sequence [CRE-01, CRE-02, CRE-03] 
were [7.21, 7.39, 7.48] and [5.68, 5.83, 5.83], 
respectively. For check means, sets were [9.21, 
9.22, 9.54] for EY and [8.01, 8.17, 8.28] for GY, so 
that in percent of check the family means were in 
the range of 78.3% to 80.2% for EY and around 

71% for GY; it is then clear that the ratio GY/EY 
for the hybrid check is much higher than for half-sib 
families in all three populations, averaging 87.5% 
and 78.5%, respectively.  

Ear yield and grain yield of the three 
semiexotic populations were considered in a good 
level, expressed as near 80% and around 70% of the 
hybrid check and this fact is attributable to the 
genetic base of the three testers used for 
introgression of the exotic germplasm. The results 
are similar to those found by Kist et al. (2010) in the 
open-pollinated population MPA, a wide base 
composite undergoing recurrent selection in the 
State of Santa Catarina.  

 
Table 2. Mean squaresĸ for Families (MF) and Error (ME), coefficients of variation (CV%) and observed means 

(m) for six traits in three semiexotic populations. 
Population MF ME CV% mo mH mL mC 

 Plant height (cm)a 

CRE-01 299.6 ** 191.7 5.6 246.7 281.0 205.0 215.4 
CRE-02 277.6 ** 148.6 4.9 247.7 284.0 211.0 222.2 
CRE-03 222.9 ** 136.6 4.5 261.3 300.0 200.0 231.8 

 Ear height (cm)a 

CRE-01 246.6 ** 147.7 8.6 141.3 180.0 100.0 112.7 



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Biosci. J., Uberlândia, v. 31, n. 6, p. 1609-1617, Nov./Dec. 2015 

CRE-02 247.0 ** 127.2 7.7 147.4 190.0 100.0 118.2 
CRE-03 269.9 ** 139.9 7.6 156.6 190.0 113.0 126.9 

 Ear diameter (cm)b 

CRE-01 0.086 ** 0.041 4.3 4.7 5.3 4.0 4.9 
CRE-02 0.128 ** 0.044 4.5 4.7 5.5 4.0 4.8 
CRE-03 0.087 ** 0.037 4.0 4.7 5.5 4.3 4.9 

 Ear length (cm)b 

CRE-01 2.405 ** 1.113 7.0 15.1 19.3 10.0 14.7 
CRE-02 2.439 ** 1.256 7.3 15.4 19.0 10.8 14.5 
CRE-03 2.334 ** 1.081 6.8 15.2 19.8 11.8 14.8 

 Ear yield (t/ha)b 

CRE-01 546.5 ** 164.1 9.9 7.21 9.78 4.83 9.21 
CRE-02 516.3 ** 162.9 9.6 7.39 10.1 4.56 9.22 
CRE-03 429.4 ** 137.1 8.7 7.48 10.1 4.83 9.54 

 Grain yield (t/ha)b 

CRE-01 365.4 ** 128.3 11.1 5.68 7.94 3.44 8.01 
CRE-02 325.4 ** 125.6 10.7 5.83 8.00 3.50 8.17 
CRE-03 297.4 ** 103.5 9.70 5.83 8.33 3.66 8.28 

ĸ Degrees of freedom for MF and MF:  
a [199 and 199 for CRE-01; 179 and 179 for CRE-02 and CRE-03].   b [199 and 398 for CRE-01; 

179 and 358 for CRE-02 and CRE-03]. **[Significance of the F test: P<0.01].   mo: population mean and its range mH (higher) and mL 
(lower); mC: hybrid check mean. 
 

Figure 1 shows the grain yield (t/ha) of half-
sib families and their distribution (percentage) for 
the three semiexotic populations; a slight superiority 
on the average of CRE-03 is apparent in Figure 1. In 
fact, for EY and GY, expressed in percent of the 
hybrid check, the population means were [78.3, 

80.2, 78.4] and [70.9, 71.4, 70.4], respectively, in 
the sequence [CRE-01, CRE-02, CRE-03]. Even 
with means around 5.7 t/ha, some families reached 
yields beyond 7.0 t/ha (∼85% of the hybrid check). 

 

 
Figure 1. Distribution of  means for grain yield (t/ha) in three semiexotic populations (CRE-01, CRE-02, CRE-

03). Jataí (GO), 2012. 
 
For both PH and EH family means were in 

the order CRE-01<CRE-02<CRE-03, averaging 
252cm and 148cm, corresponding to 113% and 
124% of the check, respectively. The observed 
means for PH and EH were classified as 
intermediate to high in the three populations, but the 

higher values were for CRE-03. In fact, the 
population used as base for the development of 
CRE-03 was a wide base composite from typically 
tropical gemplasm with the well known 
characteristic of tall plants and high ear placement. 
All the semiexotic populations also were taller than 



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Biosci. J., Uberlândia, v. 31, n. 6, p. 1609-1617, Nov./Dec. 2015 

49 cultivars evaluated under second crop condition 
in five locations in the State of Goiás (CAMPOS et 
al., 2010), thus indicating the need of some strategy 
to decrease the plant height and ear placement 
toward a pattern of plant architecture that can be 
acceptable by the local corn growers. 

Very small differences were observed for 
ED and EL among populations, which were around 
4.7cm and 15.3cm; on the average, ED was a little 
lower and EL a little higher than the hybrid check. 
Other authors have reported means in the range of  
4.2cm to 4.8cm for ED and from 15.0cm to 17.5 cm 
for EL (ANDRADE; MIRANDA FILHO, 2008; 
GARBUGLIO et al., 2009). On the other hand, the 
expression of ED and EL in the three populations 
did not differ greatly from six commercial hybrids 
grown in the region of Jataí (MARCHÃO et al., 
2005). 

In Table 3 are the estimates of parameters 
for six traits in the three populations. For EY and 
GY the phenotypic variance among half-sib family 
means (g/plant) averaged 166 and 110 while the 

genetic variance among families (
2
fσ ) averaged 114 

and 70, respectively. The additive genetic variance 

(
2
Aσ ) is calculated directly from 

2
fσ̂  and the sets of 

estimates in the order of populations were [509.9, 
471.2, 389.7] and [316.1, 266.4, 258.4] for EY and 
GY, averaging 456.9 and 280.3, respectively; the 
averages were close to the upper limit of estimates 
(450 for EY and 333 for GY) reported by Santos 
and Miranda Filho (1992) for three semiexotic 
populations in two locations. For EY the estimate 

was within the range 250 < 
2
Aσ̂ < 600 shown by 

Miranda Filho e Nass (2001); the average of the 
three populations was similar to the estimate of 
581.7 reported by Andrade e Miranda Filho (2008). 
Also, for GY the estimate was similar to the average 
(306.1 g2) of 45 estimates in Brazilian populations 
reported by Miranda Filho (1985) ; and close to 276.8 
(average of three locations) given by Kist et al. 
(2010). For comparison, it is worthwhile to mention 

the estimates of 
2
Aσ for GY reported by Hallauer & 

Miranda Filho (1988), as 469.1 on the average of 99 
estimates; the authors also mentioned 188.0 as the 
average of four experiments in the population BSSS 
(Iowa Stiff Stalk Synthetic) and 241.2 as the average in 
seven cycles of recurrent selection in the BSK(S) 
population. Other estimates at the interpopulation 
level were also given, as 386.3  (BSSS x BSCB1 as 

tester) and 373.8 (BSCB1 x BSSS as tester) in eight 
cycles of reciprocal recurrent selection.  

The results of the three semiexotic 
populations under study, referring to variance 
estimates, indicate a good pattern of genetic variation 
for enabling them as base populations for a recurrent 
selection program in the Southwest region of the State 
of Goiás.   

Estimates of the additive genetic variance 

(
2
Aσ̂ ) for PH and EH were within the range 170cm

2 < 
2
Aσ̂ < 260 cm

2, with low variation among 
populations, averaging 215.5 cm2 and 232.4 cm2; 
the estimates were a little lower for PH and a little 
higher for EH, as compared to estimates (323.8 and 
170.3) given by Andrade & Miranda Filho (2008) 
and were also similar to the average (321.0 and 218.0 
cm², respectively) of 16 estimates summarized by 
Miranda Filho (1985) in Brazilian populations. The 
estimates were, however, greater for PH and about the 
same for EH in relation to 45 estimates summarized 
by Hallauer & Miranda Filho (1988). Estimates 
higher than those herein observed were found by 
Candido et al. (2011) in the population Isanão (a 
brachytic composite) in which the higher variability 
may be the result of different expression of the 
brachytic gene (br2) in the homozygous state in 
different genotypes. For PH the estimates also were 
very smaller than the average (579.3 cm2, over three 
locations) reported by Kist et al. (2010).  

The sets of estimates of 
2
Aσ  (x10

2) for ED 
and EL were [6.00, 11.20, 6.67] and [172.3, 157.7, 
167.1], averaging 7.96 and 165.7, which are higher 
than the averages (3.9 and  142.3) of four 
experiments  of BSSS population reported by 
Hallauer e Miranda Filho (1988); the same authors 
gave the average of 36 estimates as 4.6 and 152.4. The 
estimates given by Andrade e Miranda Filho (2008) 
for the population ESALQ-PB1 were 4.40 and 
264.0, respectively. For EL, Santos e Miranda Filho 
(1992) reported values of 139.4, 96.2 and 191.6 in 
the local population E (ESALQ-PB1) and crosses E 
x EC (race Cravo) and E x EE (race Entrelaçado), 
respectively. Even with a restricted amount of 
information, the results clearly indicate that the 
populations under study have expressive variability 
for  changing ear length and ear diameter by 
selection.  

 

 



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Table 3. Estimates of  the phenotypic variance among family means (
2
HSσ̂ ), genetic variance among families 

(
2
fσ̂ ), additive genetic variance (

2
Aσ̂ ), coefficient of heritability (

2
fh : family mean basis), genetic 

coefficient of variation (CVg%), index of variation (θ), expected gain from selection (Gs) and 
expected gain from selection in percentage (Gs%) for six traits in half-sib families  of three 
semiexotic populations. Jataí (2012). 

Population Parameters estimates 
 2

HSσ̂  
2
fσ̂  

2
Aσ̂  

2
fh  

CVg% θ Gs Gs% 

 Plant height (cm) 
CRE-01 149.8 53.98 215.9 0.36 2.98 0.53 -1.04 -0.42 
CRE-02 138.8 64.53 258.1 0.47 3.24 0.66 2.02 0.81 
CRE-03 111.4 43.11 172.4 0.39 2.51 0.56 0.12 0.05 
 Ear height (cm) 
CRE-01 123.3 49.42 197.7 0.40 4.97 0.58 -1.32 -0.93 
CRE-02 123.5 59.93 239.7 0.49 5.25 0.69 1.32 0.83 
CRE-03 134.9 64.99 259.9 0.48 5.15 0.68 -0.64 -0.41 
 Ear diameter (cm) 
CRE-01 2.85 1.50 6.00 0.53 2.59 0.61 0.04 0.84 
CRE-02 4.25 2.79 11.20 0.66 3.56 0.80 0.07 1.40 
CRE-03 2.90 1.68 6.67 0.58 2.73 0.68 0.04 0.84 
 Ear length (cm) 
CRE-01 8.01 4.30 172.3 0.54 4.34 0.62 0.32 2.12 
CRE-02 8.13 3.94 157.7 0.49 4.09 0.56 0.20 1.27 
CRE-03 7.78 4.17 167.1 0.54 4.25 0.62 0.04 0.26 
 Ear yield (g/plant) 
CRE-01 182.2 127.5 509.9 0.70 8.70 0.88 14.98 11.54 
CRE-02 172.1 117.8 471.2 0.69 8.16 0.85 14.12 10.62 
CRE-03 143.1 97.43 389.7 0.68 7.33 0.84 11.95 8.870 
 Grain yield (g/plant) 
CRE-01 121.8 79.03 316.1 0.65 8.70 0.79 12.07 11.81 
CRE-02 108.5 66.60 266.4 0.61 7.77 0.73 10.63 10.12 
CRE-03 99.12 64.61 258.4 0.79 7.66 0.79 9.731 9.274 

 

The coefficient of heritability (
2
fh ) for 

family means indicates directly the level of expected 
response by selection of each trait under study. For 
the yield traits (EY and GY) the estimates were in 
the range of 0.60 to 0.80, that can be considered in a 
good level for selection purposes; these estimates 
are much higher  than the average of 0.34 and 0.35 
given by Kist et al. (2010) and Miranda Filho e Nass 
(2001), for GY and EY, respectively. For plant and 

ear height, estimates of 
2
fh  were much lower (0.36 

to 0.49) than for the yield traits. Generally, the 
heritability is higher for PH and EH than for yield 
traits (EY and GY) because the later  are more 
affected by the dominant gene action (HALLAUER; 
MIRANDA FILHO, 1988); in the present case, the 
results are explained by the genetic structure of the 
semiexotic populations, rather than on type of gene 

action controlling the trait. For the ear traits (ED and 

EL), the estimates of 
2
fh were considered relatively 

high (around 0.5), which are similar to the 0.56 and 
0.66 reported by Andrade & Miranda Filho (2008). 

The index of variation (θ) is also related to 
the expected gain from selection and were above 0.5 
for all traits in the three populations. Vencovsky e 
Barriga (1992) indicated that values of θ near or 
above 1.0 assure a favorable condition for selection. 
Here, the estimates were the lower (0.53 < θ̂  < 0.68) 
for PH and EH, and medium (0.56 < θ̂  < 0.80) for 
ED and EL. For EY and GY, the sets of θ estimates 
were [ 0.88, 0.85, 0.84] and [ 0.79, 0.73, 0.79] 
averaging 0.857 and 0.770, respectively , in the 
sequence of populations. In the present work, θ 
estimates did not follow the usual pattern of other 
studies. In fact, KIST et al. (2010) reported θ̂ < 0.5 



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(0.418 on the average) for GY in three experiments 
of the population MPA; for EH θ̂  values were 
around 1 (average 1.061). In the same way, Miranda 
Filho & Nass (2001) reported results from five 
semiexotic populations, showing estimates in the 
range of 0.361 < θ̂  < 0.661 for EY, 0.702 < θ̂  < 
0.934 for PH, 0.735 < θ̂  < 0.987 for EH,  0.190 < θ̂  
< 0.664 for EL and 0.416 < θ̂  <0.793 for ED; 
averaging 0.528, 0.827, 0.852, 0.463 and 0.598, 
respectively.  

After a final analysis of all the parameters 
related to genetic variability, it seems clear that 
yield traits were identified as the most promising for 
an effective selection. In fact, selection of the 20 
higher yielding families was practiced in the three 
populations (CRE-01, CRE-02, CRE-03), 
representing selection intensities of 10.0%, 11.1% 
and 11.1%, respectively. After recombination of the 
selected families in isolated blocks with open-
pollination, the expected effective size in the 
improved populations should be Ne ∼ 80 that is 
considered an appropriate number in recurrent 
selection programs. The expected gain from 
selection, as explained above, were 11.8%, 10.1% 
and 9.3%, respectively, averaging 10.40%. After 
one cycle of selection considering 10% yield gain, 
the expected means (t/ha) would be 6.25, 6.41 and 

6.41, representing around 78% of the check yield. 
Under the same conditions (hypothesis of no 
changes in the genetic and environmental 
parameters), the expected mean of populations after 
two cycles of recurrent selection would be around 
85% of the hybrid check.  

The overall results of this work thus indicate 
that the three populations can be used successfully 
as base for a recurrent selection program toward the 
enhancement of their yield level, and agronomic 
traits at a less extent. The main purpose of this 
project seems to be achieved, that is to open the 
opportunity to make use of an interesting source of 
exotic germplasm, identified by the resistance to the 
corn stunt complex, by incorporation into local and 
adapted maize populations. In addition, because the 
tropical origin of the introduced germplasm, it can 
contribute immediately to widen the genetic 
variability of known or unknown characteristics of 
local breeding populations.  
 
ACKNOWLEDGMENTS 
 

The authors thank the National Council of 
Scientific and Technological Development (CNPq) 
for a scholarship granted to A. S. OLIVEIRA and 
the FAPESP for financial support. 

 
 
RESUMO: O rápido aumento da cultura do milho nas últimas décadas no Brasil, principalmente na região 

Centro-oeste, causou incentivo para o milho “safrinha” (segunda cultura, geralmente milho após soja) no mesmo ano 
agrícola. Por esta razão, a necessidade de explorar novas fontes de germoplasma parece óbvia para atender ao desafio de 
criar novas cultivares (populações ou híbridos) adaptadas aos ambientes extremamente variáveis. Seguindo esta diretriz, o 
objetivo do presente trabalho foi direcionado ao estudo da variabilidade e do potencial produtivo de três populações 
semiexóticas (CRE-01, CRE-02, CRE-03) sob a condição de cultura de “safrinha” na região Sudoeste do Estado de Goiás 
(Brasil). Além disso, foi completado um ciclo de seleção recorrente com famílias de meios irmãos em cada população. As 
famílias de meios irmãos de cada população (200, 180 e 180, respectivamente) foram avaliadas experimentalmente em 
blocos casualizados com três repetições em Jataí (GO). Foram obtidas estimativas de parâmetros para produção de espigas 
(EY) e de grãos (GY), altura da planta (PH) e da espiga (EH) e comprimento (EL) e diâmetro (ED) da espiga. As médias 
populacionais para GY foram, respectivamente, 5,68 t/ha, 5,83 t/ha e 5.83 t/ha, equivalendo a cerca de 70% do híbrido 
testemunha. Os coeficientes de herdabilidade (médias de famílias) variaram de 0,36 a 0,70; 0,47 a 0,69; 0.39 a 0,68 para as 
respectivas populações. As estimativas da variância aditiva para produção de grãos (g/planta) foram 316,1; 266,4 e 258,4; 
e os ganhos esperados por seleção foram de 11,8%, 10,1% e 9.3%, respectivamente, para as três populações.  

 
PALAVRAS-CHAVE: Germoplasma exótico. Parâmetros genéticos. Seleção recorrente,. Zea mays.  

 
 

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