AFLP analysis of maize hybrids and their F₂ and F₃ progenies

The high cost of hybrid seed in Mexico has induced the use of advanced generations of maize hybrids. In this work, 22 maize hybrids and their F ₂ and F₃ progenies were characterized on the basis of grain yield patterns and AFLP fingerprinting in order to determine the genetic relationships among hybrids and their progenies and the changes on genetic structure due to controlled pollination. Grain yield was estimated in a field-irrigated experiment conducted during 2002 at Rincón de Romos, México. Mean grain yield of the 22 progenies was 26% and 24% lower in F₂ and F₃ compared to the F1 hybrid. The highest grain yields were shown by the hybrids H-361 and Fuego. Genetic dissimilarities within generations varied from 4 to 8 %, and genetic diversity decreased from F ₁ (0.587) to F₂ (0.503) and F₃ (0.465), as did average allele frequencies. The analysis of molecular variance indicated significant differentiation among generations and populations. Maize germplasm was clearly separated by generation based on AFLP data. Despite the negative effects of endogamy on most hybrids and their progenies in grain yield and genetic diversity, the use of seed of advanced progenies having reduced negative effects in F₂ and F₃ grain yields such as SB-302, Gilsa-120, Tornado or Z-60 could be suitable for farmers with low economic resources.