Heterosis and Combining Ability of CIMMYT's Tropical × Subtropical Maize Germplasm

Abstract

Crossing maize (Zea mays L.) germplasm from different adaptation groups could result in better utilization of hybrid vigor. Such heterotic response is rarely exploited, due to problems in adaptation of some of these exotic materials. This study was conducted to determine the heterosis and combining ability between tropical and subtropical maize germplasm developed at CIMMYT. Six tropical and five subtropical populations were crossed in a Design‐2 mating scheme; the 30 crosses and 11 parents were evaluated in six environments. Data were recorded on days to silk, plant height, and grain yield. Midparent heterosis was calculated for the crosses and general combining ability effects (GCA) estimated for grain yield. The six environments were classified into three mega‐environments: tropical (TR), subtropical (ST), and transition and midaltitude (TM). Days to silk was lowest in TR environments (55.4 d), followed by ST (64.6 d) and TM (71.7 d) environments. Significant differences in grain yield were observed for entries, parents, crosses, and GCA effects under TR and ST environments. The three top‐yielding crosses that also showed high heterosis were Population 43 × Population 42 (7.43 Mg ha−1), Population 32 × Population 44 (8.31 Mg ha−1), and Population 22 × Population 47 (7.97 Mg ha−1) under TR, ST, and TM environments, respectively. Population 43 among tropical germplasm and Populations 42 and 44 among subtropical germplasm showed positive GCA for yield; both are ideal for hybrid development work. Population 47, which involves temperate germplasm, was a good combiner in TM environments. The results demonstrate the considerable potential that exists for improving the yield performance of subtropical germplasm by crossing to tropical materials; for the tropics, introgressing tropical with subtropical germplasm could be used to improve plant type and maturity. The well‐known Tuxpeño × ETO heterotic pattern, observed in many crosses, could be successfully exploited in many of these materials for hybrid development.

Line × Tester Analysis of Tropical High Land Maize (<i>Zea mays</i> L.) Inbred Lines Top Crossed with Three East African Maize Populations

“…Similar results reported by Beck et al [11] for SCA in grain yield, days to silking and plant height. Vasal et al [12] also found significant mean squares due to SCA for plant height and grain yield in tropical × sub tropical crosses of maize germplasm. In this study, additive gene actions were important for ear length, ear diameter, and grain yield, suggesting that additive gene action is important for selection of quantitatively inherited traits [13].…”

Potencial discriminatório de três testadores em "topcrosses" de milho

“…Porém, esta divergência não tem determinado necessariamente a máxima expressão da heterose (Dudley et al, 1992;Vasal et al, 1992b). Assim, a seleção de genitores e a utilização de métodos que identifiquem as melhores combinações são etapas de grande importância.…”

Combining Ability for Grain Yield Performance among CIMMYT Germplasm Adapted to the Mid-Altitude Conditions

“…Pingali and Pandey (2001) indicated the importance of doubling maize production from the period of the year 2000 to the year 2020, in an endeavor to offsetting the high demands that are being caused by increasing population sizes, especially in developing countries and the increased demands for feed and biofuels globally. Hence, the new knowledge generated regarding the breeding value of the new CIMMYT lines will be useful in the development of desirable cultivars (Masny et al, 2008;Amiruzzaman et al, 2011;Singh et al, 2013).…”