Relative Stalk Sugar Yields among Maize Populations, Cultivars, and Hybrids1

Abstract

Recent emphasis on alternate energy sources has prompted research on several crops as carbohydrate sources for conversion to fuel energy. We have been assessing maize (Zea mays L.) stalks as a potential sugar source for conversion to alcohol fuel. Two methods of determining sugar yields and their relationships with plant height and maturity were also evaluated. Fifteen openpollinated maize cultivars or populations and 19 hybrids were evaluated for fermentable stalk sugar yields in replicated randomized complete block experiments in 1980 and 1981. The range of average sugar yields for the populations and cultivars was 23 to 55 g plant−1 when determinations were made on the basis of percent soluble solids by water content and 24 to 64 g plant−1 when determinations were based on high performance liquid chromatography analysis for fermentable sugars in the stalks. Comparable ranges for the hybrids were 25 to 50 g plant−1 and 17 to 52 g plant−1 by the respective methods. Hybrid means determined by the two methods were significantly correlated, while the methods for population and cultivar means were not significantly correlated because of the greater genetic heterogeneity within cultivars and populations compared to hybrids. Hybrid and cultivar or population 1980 means were highly correlated with those of 1981. The average sugar yields of cultivars and populations on a per plant basis were comparable to the hybrids, and large differences within both groups suggested that selection progress for improved yield is a reasonable expectation. The better performing entries of each group would be expected to produce sugar yields in excess of 3.5 Mg ha−1 at populations of 60 000 to 70 000 plants ha−1.