SWEET CORN SEEDLING EMERGENCE AND VARIATION IN KERNEL CARBOHYDRATE RESERVES

Seed of 24 sweet corn genotypes homozygous for either the sugary1 (su1 ),sugary enhancer (se1), or shrunken2 (sh2) endosperm mutations were p lanted in replicated field plots to evaluate for comparative seedling emergence, vigour and uniformity in cold spring soils. Percentage emer gence, averaged over the genotypes with either the su1, se1, or sh2 mu tations was 69, 46, and 44%, respectively. Variability among se1 genot ypes indicated that cold emergence could possibly be improved to equal that observed in some of the best su1 varieties. Quantitative amounts of individual sugars (fructose, glucose, sucrose, and maltose), phyto glycogen, and water insoluble starch from remnant mature dry seed of e ach genotype were determined by laboratory analysis. Mean kernel total sugar content in mg/g dry weight for su1, se1, and sh2 genotypes was 28.6,42.1 and 47.0, respectively. A highly significant correlation was found when the kernel sugar concentration of the 24 genotypes were re gressed against field emergence (r = -0.74, p < 0.0001) suggesting tha t a negative relationship exists between kernel sugar content and swee t corn germination and emergence in cold soils. Data on a mg/kernel ba sis showed a significant positive correlation between kernel starch co ntent and percentage field emergence (r = 0.63, p = 0.0008). This info rmation is valuable to breeders and commercial growers for selection o f superior cold tolerant genotypes.