THERMAL STARCH PROPERTIES IN CORN-BELT AND EXOTIC CORN INBRED LINES AND THEIR CROSSES

More knowledge is needed about variability of starch functional traits in adapted and exotic germplasm and possible genetic effects of these traits before conducting rigorous inheritance studies and breeding pr ograms for starch quality. We studied and compared the range of variab ility for starch functional traits in a set of Corn Belt inbred lines with a set of exotic inbred lines from Argentina, Uruguay, and South A frica. Reciprocal hybrids of some of the lines within each set were co mpared with their parents. Functional traits were examined by using di fferential scanning calorimetry on starch extracted from single kernel s of genotypes. The set of Corn Belt lines had a wider range of values for most traits than did the set of exotic lines. For both sets of li nes, the maximum value for peak height index was as high as that previ ously reported for the waxy endosperm mutant. Although the Corn Belt l ines exhibited a wider range of values for range of retrogradation tha n the exotic lines, the exotic lines showed a wider range of values fo r percentage retrogradation. Hybrid values were not consistently highe r, lower, midpoint, or similar with respect to the values of their par ents. This was true regardless of germ-plasm type or functional trait. Reciprocal cross values showed trends suggesting reciprocal differenc es, although there was no trend suggesting greater effect of the femal e parent. These traits seem to be controlled by many modifying effects in addition to major effects. Results indicate that sufficient variab ility exists in Corn Belt germplasm to conduct breeding and inheritanc e studies effectively and that there should be potential for breeding for functional traits.