Topcross in supersweet corn doubled haploids for the formation of heterotic groups and hybrid selection¹

Topcross em duplo-haploides de milho superdoce na formação de grupos heteróticos e na seleção de híbridos

Doubled haploid technology is widely used in conventional corn to accelerate the development of inbred lines. This study aimed to estimate the combining ability of supersweet corn doubled haploid lines, identify new tester lines and establish heterotic groups. Two tester lines (L_A and L_B) were crossed with 28 doubled haploid lines of six supersweet corn populations using the topcross method and evaluated together with five checks for dehusked ear yield, ear diameter, plant height and soluble solids content. The growing seasons and treatments had significant effects on all the investigated traits, as well as season x treatment interaction on ear yield and diameter. The H_A1, H_B1, H_B12, H_B13, H_B14, H_B15, H_B19, H_B20 and H_B22 hybrids exhibited a superior performance, with average yields ranging from 11.95 to 15.39 t ha^-1, and were grouped with the commercial check and Test₃. The L_B and L₁₉ lines showed the best general combining ability estimates for yield. There were significant specific combining ability effects for most variables. The lines obtained from the PD2005 and PD2006 populations were allocated to the same heterotic group as L_B, and those from the synthetic populations SD3002 and SD3003 to the same group as L_A. The L₁₉ line shows potential of use as a tester for SD3005 lines.

KEYWORDS:
Zea mays L. var. saccharata Koern; combining ability; tester lines