Heterosis and combining ability of CIMMYT's subtropical and temperate early-maturity maize germplasm
Vasal, S.K.; Srinivasan, G.; Crossa, J.; Beck, D.L.
Crop Science 32(4): 884-890
Knowledge about the combining ability and heterotic patterns among CIMMYT's maize (Zea mays L.) germplasm is essential for hybrid development work at CIMMYT, as well as at other national research programs using CIMMYT germplasm. This study was conducted to determine the heterosis and combining ability among CIMMYT's subtropical and temperate early-maturity maize germplasm. A seven-parent diallel involving two populations and five gene pools was made. The parents and 21 crosses were evaluated in 17 temperate and 5 subtropical environments during 1985-1986. Average yield across temperate environments (4.35 Mg ha-1) was comparable to that obtained in subtropical environments (4.59 Mg ha-1). Highest yield in subtropical environments was recorded by Population 48 X Pool 27 (5.42 Mg ha-1), with a high-parent heterosis of 9.9%. Maximum high-parent heterosis was observed in Population 46 X Pool 30 (13%), which yielded 5.17 Mg ha-1. Under temperate environments, the highest-yielding combinations included Population 48 crossed with Population 46 and Pools 27, 28, and 30, although maximum heterosis (10.2%) was recorded for Pool 27 X Pool 40. General combining ability (GCA) effects for yield were significant in both sets of environments, while specific combining ability (SCA) effects were significant only in temperate environments. Highly significant positive GCA effects for yield were observed with Population 48 (0.43 Mg ha-1) and Pool 30 (0.33 Mg ha-1) under temperate conditions. Pools 40 and 42 were poor general combiners in both sets of environments. Significant positive SCA effects for yield were observed with Population 46 X Population 48 and Population 46 X Pool 30 crosses in temperate environments and the Population 48 X Pool 27 cross under subtropical environments. Population 48 and Pool 30 way hold potential for use as source germplasm for both temperate and subtropical maize breeding programs.