Date of Award
Program or Major
Doctor of Philosophy
A detailed investigation was conducted to examine further the biochemical and genetic bases of the hull-less phenotypic condition in testae of seeds of pumpkin (Cucurbita pepo L.). During seed development, testa moisture declined substantially (30%) in both phenotypes, whereas testa dry and fresh weights increased dramatically between 10 to 20 days post-anthesis and then declined steadily until seeds reached maturity. Structural compositional analysis revealed marked reductions in lignin (78%) and cellulose (50%) in hull-less compared with normal phenotypes; whereas no differences in non-cellulosic polysaccharides were found at 20 days post-anthesis. Between 20 days post-anthesis and maturity, pectin content of testae was dramatically reduced in both phenotypes (80-90%). A similar reduction was observed for hemicellulose fractions.
Analyses of precursor pools and reserve compounds at 20 days post-anthesis did not reveal consistent differences in quantities of sugars, free amino acids, total phenolics, lipids and starch between phenotypes. By maturity, precursor pools and starch in testae had been essentially exhausted in all strains.
Total N values for testae of normal and hull-less phenotypes were not consistently different at 20 days post-anthesis and maturity. About 60% of total testae N compounds was recovered as soluble fractions at 20 days post-anthesis. A substantial amount of structural protein was bound to hemicellulose 'A' fractions and substantially lesser amounts were recovered from cellulose, pectin and hemicellulose 'B' fractions of cell walls in normal and hull-less phenotypes. No consistent differences in amino acid composition of hemicellulose 'A'-associated protein were observed between phenotypes. Some differences in amino acid composition of hemicellulose 'B'-associated protein were observed between normal and hull-less strains, however, discrepancies in amino acid composition between replicates preclude making definitive conclusions about the nature of the differences at this time.
Results of the inheritance investigation indicate that the hull-less condition in testae of seeds of pumpkin is controlled by a single major gene, and the degree of hull-lessness may be affected by modifying genes. Variable expression of hull-less phenotypes indicates some degree of environmental interaction with hull-less genotypes.
STUART, SUSAN GERARDETTE, "COMPARATIVE BIOCHEMICAL AND GENETIC STUDIES OF TESTA DEVELOPMENT IN NORMAL AND HULL-LESS PHENOTYPES OF PUMPKIN (CUCURBITA PEPO L)" (1983). Doctoral Dissertations. 1398.