Genetic variation for endosperm carbohydrates and total soluble solids in shrunken2, sugary1, waxy1, and wild-type near-isogenic corn lines across three harvest dates

Sweet corn (Zea mays L.) cultivars must meet stringent quality standards to be accepted in the marketplace. Breeding for eating-quality traits, such as sweetness, typically involves taste ratings or quantification of carbohydrate content. Total soluble solids (TSS) content is used as a proxy for sweetness in many fruit crops. Using a diallel of near-isogenic corn lines for sugary1, shrunken2, waxy1, and wild-type (WT) endosperm types, a combining ability analysis for carbohydrate traits and TSS content determined the relationship of these traits over three harvest dates. Variation existed for total sugar, sucrose, glucose, fructose, total polysaccharides, and starch content within and across endosperm types and harvest dates, but strong correlations with TSS content were present only when assessed across all endosperm types. Strong similarities existed among WT, waxy1, and sugary1 near-isogenic lines for general combining ability for carbohydrate traits, while shrunken2 near-isogenic lines had different desirable combiners. Line C40 was a desirable general combiner for carbohydrate traits among WT, waxy1, and sugary1 endosperm types, while Ia5125, P39, and Ia453 were desirable general combiners for shrunken2 endosperm. This experiment also determined that TSS content is not a useful trait in sweet corn breeding for quality traits.