During the past 70 years, genetic yielding ability of maize hybrids adapted to central lowa (USA) has increased at a linear rate of about 74 kg/ha/yr, according to trials conducted during 1991-1994. Comparisons of 36 widely grown hybrids released at intervals from 1934 to 1991 show continuing improvements in tolerance to abiotic and biotic stresses such as heat and drought, excessively cool and wet weather, low soil fertility, high density planting, root and stalk rot, and European corn borer (Ostrinia nubilalis). The hybrid series also exhibited linear increases in erect leaf habit and grain starch percent, and a linear decrease in grain protein percent. These continuing changes in plant architecture and grain composition conceivably can increase efficiency of grain production tinder stresses of high density planting, unfavorable weather, or low soil fertility. Maximum yield potential per plant has neither increased nor decreased during the past 70 years, as measured on non-stressed plants grown at very low densities (1 plant/m2). Results of the 1992-1994 trials agree with the hypothesis that increased grain yielding ability of widely successful maize hybrids for central lowa is due primarily to improved tolerance of abiotic and biotic stresses, coupled with maintenance of the ability to maximize yield per plant tinder non-stress growing conditions.

English

9802|AGRIS 9702

Jose Juan Caballero

CIMMYT Publications Collection