Combining Abilities of Quality Protein Maize Inbreds

Abstract

Development and adoption of quality protein maize ( Zea mays L.) (QPM) would increase the nutritional value of food and feed maize products. Breeding programs at the International Center for Maize and Wheat Improvement, Mexico (CIMMYT); Texas A&M University (TAMU); and University of Natal, South Africa (SA) have developed high‐lysine inbreds. Information about how elite QPM inbreds of different origins combine and perform in hybrids will facilitate the selection of parents and breeding strategies for hybrid development. Our objectives were to estimate the general (GCA) and specific combining abilities (SCA) for grain yield and secondary traits among high‐lysine inbreds from different sources and to identify potential heterotic relationships among them. Seven white (CML176, CML181, CML184, Bo59W, Tx807, Tx811, and TxX124) and nine yellow QPM inbreds (CML190, CML193, Tx802, Tx814, Tx818, Tx820, Do940y, TxX808, and TxX806) were evaluated in two separate diallel experiments in five southern U.S. environments. The QPM hybrids yielded less than commercial checks. Across environments, GCA effects were nonsignificant for grain yield but highly significant for agronomic and kernel‐quality traits. On the basis of GCA effects, TAMU inbreds had earlier maturities, shorter plants, and less grain moisture content than more subtropical CIMMYT and SA inbreds. The best‐yielding hybrids and highest SCA effects resulted from crosses among inbreds from different programs: TxX124 × CML176, Tx811 × CML181, and Bo59w × CML184 among the white hybrids, and Tx802 × Do940y among the yellow hybrids. The QPM inbreds developed in different programs could represent potential heterotic groups for use in hybrid development and introgression of germplasm.