Date of Award
Doctor of Philosophy
J. S. Burris
Incorporation of high sugar endosperm mutants into sweet corn genotypes has altered the carbohydrate composition of the resultant kernels which exhibit high post-harvest sugar retention and extended shelf life. However, acceptance of these genotypes has been limited because of problems associated with reductions in seed viability and seedling vigor and increased susceptibility to soil pathogens;The objective of this study was to characterize the physiological differences in seed viability and vigor associated with drying temperature and stage of maturity, and to determine the relationships between kernel soluble sugars during maturation and subsequent seed quality in sweet corn endosperm mutants;Seed of three genotypes, Jubilee (su), Sucro (sh2), and a genotype with the se gene, was harvested over a range of moisture contents during five harvests at 4-day intervals beginning 35 days after pollination. Ears were dried at 35, 40 and 45 C to 12% moisture. Seed viability was determined by the warm germination test, while the cold germination test, shoot to root ratio, and germination test after soaking seeds were used as indicators of vigor. Leachate conductivity was measured to indicate membrane integrity. Soluble sugars of embryos and endosperms obtained from fresh kernels at successive stages of maturity and from seed leachate, were separated by high performance liquid chromatography;Sweet corn seed exhibited a protracted period of high moisture retention throughout maturation. Seed moisture was poorly correlated with seed viability (r = -0.52) and seedling vigor (r = -0.46). Seedling vigor was more a function of genotype while seed viability varied with genotype, maturity, and drying temperatures. The se-genotype exhibited superior viability and vigor as compared with Jubilee and Sucro. Kernel maturity had less effect on electrolyte leakage than did drying temperature and genotype. Sucro exhibited the greatest rate of leakage when conductivity was read at 6, 12, and 24 h after soaking seeds. High seed quality was obtained when seed was dried at 35 C;The se-genotype exhibited the highest ratio of embryo sucrose to total sucrose and ratios of maltose and raffinose to sucrose. It is suggested that these ratios may play a role in membrane integrity during maturation drying and during imbibition and subsequent germination.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Henry R. Mloza-Banda
Mloza-Banda, Henry R., "Seed maturation and drying in sweet corn (Zea mays L.) endosperm mutants " (1992). Retrospective Theses and Dissertations. 10334.