Distribution of carbohydrate during grainfill in Leafy and normal maize hybrids

Abstract

The Leafy (Lfy) genotype in corn has extra leaves above the ear in comparison to normal non-leafy genotypes and has been shown to increase yields in some geographical areas. In this study, carbohydrate distribution in three Lfy hybrids (two of which were "staygreen") and a normal check (Pioneer 3790) were analyzed in a short-season area (2800 Crop Heat Units, suitable for 85 day Relative Maturity hybrids). Total sugar and starch were determined at all aboveground levels of leaf and stem on 1 August 1990 and this distribution was used to calculate total canopy carbohydrates in two subsequent years from samplings of leaf and stem at only three or four canopy levels bracketing the ear level. Husk, cob and kernel components were also analyzed at three sampling times during grainfill. Major differences in the 2 yr were observed, but in general there was approximately twice the carbohydrate in the canopy at and above the ear in the Lfy genotypes compared to the check. There was also more carbohydrate in the husk and cob in the Lfy lines, but substantially less carbohydrate below the ear in these lines. Rates of grainfill were generally higher in the Lfy hybrids, but the rate of Lfy hybrid A, the early senescent hybrid, was slower in the cooler growing season. Despite the greater amount of carbohydrate in the Lfy hybrids in comparison to the traditional check, their grain yields were not greatly increased, indicating that the kernel component provided a weak sink. This characteristic is probably associated with the long season and tropical origin of the Lfy germplasm. Key words: Maize, grainfill, leafy, carbohydrate distribution, phenology, sink size