Thesis (Ph. D.)

The main objectives of this study were; (i) to know the general combining ability (GCA) and specific combining ability (SCA) of eight QPM maize inbred lines for CIMMYT maize program; (ii) to identify the best hybrids. The Griffing method IV was used to get all possible direct crosses (28) among the eight inbred lines. Crosses were evaluated at the "Ampuero Ranch" of Torreón, Coahuila, México, during 2001 and 2002. In both years a complete randomized blocks experimental design with two replications was used. Plant density was 80,000 plants ha-1 Agronomic characteristics such as plant height (PH), green forage yield (GFY), dry matter yield (DMY) and ear percentage (EP) were measured. Forage quality characteristics such as dry matter intake (DMI), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lactation net energy (LNE) and in vitro dry matter digestibility (IVD) were also measured. Results showed significant variation (P ≤0.01) between the crosses (genotypes) for the evaluated agronomic and chemical traits, with exception of IVD, all crosses agronomic and chemical characteristics showed significant variability. PH, GFY, DMY, DMI and CP showed GCA highly significant statistical differences among inbred lines. With the exception of IVD, all the other forage quality characteristics showed significant SCA effects. Mean squares analysis showed additive effects were more important for GFY, DMY, DMI and LNE, and no additive effects were greater than the additives in characteristics such as PH, EP, CP, ADF and NDF. Line 3 PH and CP, line 7 GFY, DMI and LNE; line 1 EP and NDF, line 4 DMY and line 2 IVD showed the highest GCA. Crosses 2x5, 4x5, 5x7 and 7x8 showed the best GFY and DMY but EP was low. The forage quality of these characteristics was inconsistent.

Spanish

0601

Thesis Collection