HETEROSIS AND COMBINING ABILITY AMONG COMMERCIAL HYBRIDS AND EXOTIC MAIZE GERMPLASM IN JALISCO, MÉXICO

Abstract

Diallel crosses were developed among twelve maize (Zea mays L.) progenitors, six adapted and six exotics. The adapted ones were the commercial hybrids Tornado, C220, D-880, P-3066, A-7573, and H357. The exotic progenitors were populations Pop-49 and Pop-32 from CIMMYT, the commercial temperate hybrid P-3394, the synthetics SynB73 and SynMo17 from the USA Corn Belt an the local landrace Blanco de Ocho. The crosses were done in an AutumnWinter season in 1996/1997, and evaluated in a lattice experimental design 10 X 10, in four locations (three in Jalisco and one in Nayarit) under rainfed conditions in the 1997 Summer season. Heterosis was calculated on the mid-parent basis using the average of the four locations. The effects of general combining ability (CGA) and specific combining ability (SCA) of progenitors were obtained in a crossedway (adapted x exotic), with the average of only three locations. The best cross for grain yield was P-3394 x D-880 (5,683 kg ha ^–1) with an heterosis of 183 %; it had also the highest SCA (825 kg ha^-1). The heterosis value for the region represented by the cross SynB73 x SynMo17 was higher (83 %) than that of the tropical-subtropical region represented by Pop-49 x Pop- 32 (23 %). The best adapted progenitors crossed by the exotics were D-880 and H-357 for grain yield and ear length; the best exotic progenitor was P-3394. The adapted hybrids P-3066 and A-7573 had the poorest combination with the exotic materials from the Corn Belt. The mean heterosis for grain yield among adapted x exotic (73 %) was superior than adapted x adapted (59 %) and than exotic x exotic (62 %). Based on these results, it is suggested to establish an heterotic pattern for the tropical-subtropical areas using the best combinations between Corn Belt materials and those from local regions. Therefore, it is important to initiate maize breeding projects for adapting temperate germplasm to tropical and subtropical areas.