Yield Potential and Combining Ability of Tropical Quality Protein Maize Inbred lines

H. Córdova and A. Krivanek

Progress on breeding quality protein maize (QPM) germplasm at CIMMYT has contributed to the release of this type of maize in 21 countries in the developing world. The objective of this study was to estimate the combining ability of 34 new tropical QPM lines crossed to two testers and determine their yield potential in hybrid combinations. Testcrosses were evaluated in eight environments representative of the tropical lowlands. A line x tester model was applied to estimate general and specific combining ability effects. Our results demonstrate new hybrid combinations with outstanding yield potential and stability across sites. The best performing QPM hybrid yielded 7.0 t/ha, across seven sites and 12 t/ha at a Guatemala location, 40% more than the best seed industry check. Ten QPM inbred parents showed significant GCA estimates for yield and ranked from 0.414 to 0.884 t/ha, 2.5 to 4.5 times the standard error for GCA. Each of the 10 lines measured more than double the levels of lysine and tryptophan content than the normal maize checks.