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Genetic variation for combining ability in the short-day onion cultivar pira-ouro in topcrosses with baia petrolini

W.R. Maluf^I,II; R.D. Corte^I; M. Toma-Braghini^I

^IBioplanta Tecnologia de Plantas SA., Caixa Postal 1141, 13100 Campinas, SP, Brasil
^IIPresent address: Departamento de Agricultura/Escola Superior de Agricultura de Lavras, Caixa Postal 37, 37200 Lavras, MG

ABSTRACT

Six onion cultivars [Granex Ouro (G.O.) F₁, Granex 33 (G-33) F₁, Brownsiville (BV) F₁, Pira-Ouro (P.O.) o.p., Baia Petrolini (B.P.) o.p. and Baia Periforme Superprecoce (B.P.S.P.) o.p.] were tested in a trial along with 40 different experimental hybrids, obtained by toperossing male-sterile So clones from P.O. to B.P. Significant differences among treatments were found for yield, cycle, percent bolting and average bulb weight. The highest yielding checks were P.O. (43.2 t/ha) and B.P. (38.9 t/ha), followed by G-33 (30.2 t/ha), BV (28.2 t/ha), G.O. (27.0 t/ha) and B.P.S.P. (24.7 t/ha). Variance among toperosses was significantly larger than zero for all traits under consideration, indicating the existence of ample genetic variation for combining ability within the cultivar Pira-Ouro in toperosses with open-pollinated Baia Petrolini. The average yield of the toperosses was similar to that of the lowest yielding parental cultivar (B.P.), but some toperosses outyielded the highest yielding parent (P.O.) by as much as 25.9%. The average cycle of the toperosses was comparable to that of the earliest parent (P.O. = 181 days), but some toperosses were considerably earlier, comparable to the earliest of the check cultivars in the trial (G-33 = 170 days). Genotypic and phenotypic correlations among all traits were low, except that between yield and average bulb weight, indicating the possibility of selection of toperosses that are simultaneously higher yielding, earlier and less prone to bolting than Pira-Ouro.

Keywords: Genetic variation; Combining ability; Onion.

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