Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Plant, Environmental Management and Soil Sciences

First Advisor

Manjit S. Kang


Corn (Zea mays L.) hybrids with rapid ear moisture loss rate (EMLR) are needed to reduce post-harvest production costs relative to artificial grain drying. Previous investigations indicated that genetic variation for grain dry-down rate existed; however, genotype by environment interaction (GEI) for this trait has not been specifically investigated. The objectives of this study were: (1) to evaluate EMLR and stability of selected commercial corn hybrids in different environments, (2) to determine approximate optimum numbers of plants per plot, replications, and environments for evaluating EMLR, and (3) to assess the contribution of known environmental factors to GEI for EMLR. Experiments with two groups of corn hybrids (early maturity, and medium and full season maturity) were conducted during 1993-1995 at multiple planting dates. Relative efficiency (RE) increased with increased replications. With five to six plants per plot and four replications (20 to 24 plants total), the same efficiency can be achieved as obtained with 11 plants per plot and three replications (33 plants total). These results were validated by the experiments conducted in 1994. The RE increased as the number of planting dates (environments) increased. The same RE (100%) was achieved by using three to four plants per plot, three replications and four planting dates, as that obtained with 11 plants per plot, three replications and three planting dates. Restricted maximum likelihood method was used to estimate GEI variances and interpret the stability of each hybrid. Hybrids of both maturity groups differed significantly in their stability for EMLR. Precipitation and relative humidity were the most important, single environmental factors that contributed to GEI. When two factors were considered simultaneously, precipitation+growing degree days from planting to black layer maturity and relative humidity+growing degree days from planting to black-layer maturity accounted for the largest amount of GEI. Individual hybrids responded differently to these environmental factors. This provided a better insight into the causes and nature of GEI for EMLR, which should help reduce or exploit GEI.