Comparison of Sweet Corn Vigor with Ions and Sugars in Seed Leachate of Five Isolene Pairs with Two Endosperm Types

Supersweet corn contains more sugar and less starch than traditional sweet corn which increases the sweetness of the kernel. Supersweet corn has increased in consumer popularity due to its sweeter flavor and ability to retain this sweeter flavor longer than traditional sweet corn. Two sweet corn (Zea mays L. var. rugosa) endosperm types (traditional and shrunken-2) are popular with consumers. The problem growers face with supersweet cultivars (shrunken-2) is poor seed vigor as shown by low field emergence and non-uniform stands. Field emergence of plants was compared to laboratory germination for 5 sweet corn isoline pairs (genetically identical except for 1 allele or modifying allele), i.e. C68, Ia5125, Ia453, Il442a and Oh43 with each pair having 2 endosperm types, shrunken-2 (sh2) and traditional (su1). Field studies evaluated plant height, fresh weight, dry weight, leaf area and number of leaves. Ions, total sugars and individual sugars in leachate from sweet corn seeds soaked in water were evaluated for the same isoline pairs. These evaluations were performed using electrical conductivity (ion leakage), spectrophotometry (total sugars) and high pressure liquid chromatography (sucrose, fructose and glucose). Emergence and germination studies for sh2 and su1 endosperm types were compared to indicate seed vigor. Ions and sugars in seed leachate were examined for an association with seed vigor. Traditional sweet corn had higher emergence and in most cases, higher germination than sh2 for each isoline. Shrunken-2 isolines leaked the same or more ions than su1 isolines. The isolines that leaked more ions had lower laboratory germination and field emergence. Shrunken-2 isolines leaked more total sugars (mg/g seed) than sul isolines. The poorest germinating and emerging isoline also leaked the most sugars. Analysis of individual sugars (sucrose, fructose, glucose) revealed that sh2 leaked the same or more than su1. Differences between isolines showed the lowest field emerging and laboratory germinating isoline leaked more or the same amount of individual sugars. For individual sugars (sucrose, fructose and glucose) measured, more fructose leaked than sucrose or glucose. Of parameters measured, total sugars in leachate using spectrophotometry best predicted field emergence and laboratory germination between endosperm types and isolines except for germination of isoline Oh43. Ion leakage and individual sugars in leachate also showed trends of association with emergence and germination in isolines, but not as closely paralleled as total sugars between endosperm types (sh2 and su1)