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Evaluation of inbred lines from two maize (Zea mays L.) brachytic populations in single crosses following the two-factor mating design
Carlos S. MartinsI; José B. Miranda FilhoII
ICPATU-EMBRAPA, Caixa Postal 48, 66.000 Belém, PA, Brasil.
IIDepartamento de Genética, ESALQ/USP, Caixa Postal 83,13400-970 Piracicaba, SP, Brasil. Send correspondence to J.B.M.F.
ABSTRACT
Thirty dent and 15 flint inbred (S5) lines from the brachytic maize (Zea mays L.) populations 'Piranão-VD2B' and 'Piranão-VF1B', respectively, were used for the evaluation of 120 single crosses. The factor design (partial diallel) of six 5 x 5 sets was used. The flint lines entered twice because each one was evaluated with two different sets of dent lines. Field evaluation was in 5 x 5 balanced lattice trials and the following traits were analyzed: TE, total ear weight in the plot; SE and SG, ear weight and grain weight in a sample of five ears; PH and EH, plant and ear height; TB, tassel branch number; ED and CD, ear and cob diameter, and MF and FF, days to male and female flowering. The 10% best single crosses yielded from 119.0% to 138.7% relative to check variety ('Piranão-VD2'). General combining ability (GCA) was more important than specific combining ability (SCA) as a source of variation, although SCA effects were relatively important in some specific crosses. The GCA mean squares for yield were higher for flint lines relative to dent lines in five of the six sets. High correlation coefficients were observed between gj's (GCA of flint lines) obtained from crosses with different sets of dent lines: 0.923, 0.904 and 0.907 for TE, SE and SG, respectively. The reduced model Yij = µ + gi + gj was used for prediction of single crosses that were not included in the field evaluation. For the yield traits (TE, SE and SG), the coefficients of determination (R2) relative to the reduced model were in the range of 0.74 to 0.90. The use of the factor design for evaluating inbred lines in crosses and the reliability of predicted means as a guide for selection are discussed.
Keywords: Zea mays; inbred lines; mating design.
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