The effect of competition on yield and its components in corn (Zea mays L.)

Abstract

The phenotype of an organism is the expression of its genotype relative to the environment in which it develops. The increase in plant population, a general practice to Increase total yield, tends to suppress the potential expression of several plant charac- ters. It is of great importance to determine the stage of plant development in which these changes become permanent. The effect of competition stress was studied by thinning 32,000 plants/acre populations to 8,000 and 16,000 plants/acre at five stages of plant development, using six non-segregating popula- tions of corn. Most plant and ear characters were significantly influenced by stress in the period of rapid vegetative growth and after silking. Some attributes were able to recover considerably from retardations in early stages of plant development. Significant differences were observed between the two final plant populations, when population stress was decreased prior to silking. Observed yield losses were caused by increased barrenness and by decreased ear size as stress was maintained. The six genotypes showed different reactions to stress Hy2 x 0h07 proved to be the least affected hybrid and C103 and B37 germ plasm contributed to increased barrenness in the combinations used.