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3 Material and Methods
The experiment was installed in the years 2002 and
2003 in the experimental field located at Capão do
Leão County-Rio Grande do Sul State (RS). In this
work, five oat cultivars (UPF 16, UPF 18, UFRGS 7,
UFRGS 17 and URPel 15) were crossed forming five
hybrid combinations. F
1
seeds from each combination
were obtained in greenhouse in the fall/winter 2002.
In the same year (spring/summer), the first backcross
generation [RC
1
F
1
(F
1
x P
1
) and RC
2
F
1
(F
1
x P
2
)] as
well as F
2
seeds were obtained. In 2003, three fixed
(P
1
, P
2
e F
1
) and three segregating (F
2
, RC
1
F
1
e RC
2
F
1
)
generations were sowed in the field. Plants were
conducted in 3 m long rows with 0.3 m spacing
between plants and rows. The experimental design
used was random blocks with three replications,
considering one plant as an observation unit. After
harvesting, the following characters were evaluated in
the laboratory: i) number of panicles per plant (NP P
-1
),
through the counting of fertile tillers of individual
plants; ii) production of grains per plant (GY P
-1
),
through the individual threshing of plants, in grams;
and iii) panicle weight (PP), obtained by weighing the
main panicle, in grams. From plant individual values
were estimated the means and variances for each
generation in the distinct crosses.
The phenotypic (σ
P
2
), genetic (σ
G
2
), additive (σ
A
2
),
dominant (σ
D
2
) and environment (σ
E
2
) variances and
the heritabilities in the broad (h
a
2
) and narrow (h
r
2
)
senses were estimated according to Allard (1960),
where: σ
P
2
=σ
F2
2
; σ
G
2
=σ
F2
2
-σ
E
2
; σ
A
2
=2
σF2
2
-(σ
RC1
2
+ σ
RC2
2
);
σ
D
2
=σ
G
2
-σ
A
2
; σ
E
2
=(σ
P1
2
+2σ
F1
2
+σ
P2
2
)/4; h
a
2
=σ
G
2
/σ
P
2
and
h
r
2
=σ
A
2
/σ
P
2
. When negative values for dominance
variance (σ
D
2
) were found, the following alternative
formula was used, according to Carvalho et al. (2001):
σ
D
2
=4(σ
F2
2
-σ
A
2
/2-σ
E
2
).
The heterosis estimate was based on a model similar
to the initially proposed by Matzingeret al. (1962) and
described by Gardner and Eberhart (1966): H1(%)=
(F
1
-MP)/MP*100, where: H
1
(%)=heterosis relative to
the parental mean, F
1
=hybrid mean and MP=parental
mean, obtained as: MP=(P
1
+P
2
)/2. The loss of vigor
(LV) was calculated based on the model described by
Vencovsky and Barriga (1992): LV(%)=(MF
1
-MF
2
)/
MF
1
*100, where: LV(%)=loss of vigor, MF
1
=mean of
F
1
generation, MF
2
=mean of F
2
generation.
The genic effects for each cross were estimated for the
characters GY P
-1
, NP P
-1
and PP, using the generalized
weighted least square method and testing the adjust-
ment of the model of six parameters (complete model:
mean “m”, additivity “a”, dominance “d”, additivity x
additivity “a x a”, additivity x dominance “a x d” and
dominance x dominance “d x d”) and three parameters
(reduced model: mean “m”, additivity “a” and domin-
ance “d”), according to Mather and Jinks (1982). The
significance of the genetic parameter was verified by
the t test, as follows: t=ê/DP, where: ê=parameter
estimate and DP= parameters standard deviation.
Authors’ contribution
IV, CL, JS and HL participated in the design of the study, in the
experimental conduction of essays, in the statistic analysis and
in the manuscript writing. ACO and FIFC participated in the
design and supervision of the study and preparation of the final
manuscript. All authors have read and approved the final
manuscript.
Acknowledgements
The authors are thankful to the Brazilian Council for Research
and Development (CNPq), Higher Education Improvement
Bureau (CAPES) and Rio Grande do Sul State Research
Assistance Foundation (FAPERGS) for grants and fellowship
support.
References
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st
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