Abstract

Twelve corn (Zea mays L.) cultivars were evaluated under two environments in Central America and one in Mexico in order to determine the genetic progress achieved for resistance to stunting, after four selection cycles of the population 73. The trial included the synthetics from the cycles 0, 1,2,3 and 4, composites from the cycles 2, 3 and 4, three tolerant control s N8-6, Santa Rosa 8073 and the hybrid H-53, and a susceptible control (hybrid 8-833). The percent averages of stunted plants were relatively low (between 10 and 20 %) at the three localities. The cycle 4 synthetic yielded an average (4214 kg/ha) statistically alike to the hybrids 8-833 and H-53 (4288 and 4030 kg/ha, respectively). The cycle 4 synthetic showed the lowest stunting percentage (8.9%), the commercial tolerant variety NB-6 showed 16.2% and the susceptible hybrid (B-833) 22.8%. A lineal regression between yield averages and the selection cycles reveal an average gain per cycle of 149 kg/ha (4.3 % per cycle) and a reduction per cycle of 2% of stunted plants (11 % gain/cycle). It is concluded that the proceedings among S1 lines has been effective in improving the performance of population 73, increasing productivity of grain yield and the stunting resistance.