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Seed Quality of lsogenic Endosperm Mutants in Maize
|Title:||Seed Quality of lsogenic Endosperm Mutants in Maize|
|Abstract:||Five studies were conducted based on ten near-isogenic corn hybrids converted to four endosperm genotypes — +, su, bt and sh2.|
Five different types of germination tests were conducted, including accelerated aging. Among the four endosperm genotypes, seed with wild type endosperm always had the best viability, followed in turn by su, bt and sh2 hybrids.
Electrolyte leakage caused by accelerated aging (AA) was highly correlated with the deterioration of viability caused by AA. Seeds with poor germination ability suffered more from AA, indicating that seeds with good germination ability will have better storability. The accelerated aging, therefore, should be useful for predicting viability loss in seed storage.
Pericarp thickness was influenced greatly by endosperm mutant genes. Pericarp thickness of sh2 hybrids at 36 days after pollination (DAP) were significantly greater than those at 18 DAP, while thinning trend of pericarp thickness was observed for wild type hybrids. There was no significant difference for bt and su hybrids from 18 to 36 DAP. A highly significant correlation was observed between seed weight and the difference of pericarp thickness harvested at 18 and 36 DAP. The data were interpreted as evidence for the effects of inner (endosperm) pressure on pericarp distension.
The comparisons of eating quality among su, bt and sh2 endosperm mutants showed in general, that su had the worst and sh2 had the best eating quality considering sweetness and flavor, although the difference between bt and sh2 was not significant for many hybrids. The extensive genotypic variability for these eating qualities among the bt hybrids suggests that the allelic variation at loci other than bt is probably involved.
Six germination-related characters were evaluated for bt and sh2 hybrids. These were seed weight, pericarp thickness, bubble volume, seed density, leachate conductivity and sweetness. In general, sh2 seed was sweeter with lower seed weight and density, and higher pericarp thickness, leachate conductivity and bubble volume (between endosperm and pericarp in mature seeds). These differences could be largely attributed to the efficiency of bt and sh2 genes in hindering the conversion of sucrose to starch.
A method of measuring bubble volume through the change of soapy water volume was developed. The hypotheses were proved that bubble volume was determined by both shrinkage of endosperm and pericarp thickness, and thick pericarp affects germination rates of super sweet corn adversely through its effect on the formation of a large bubble volume. Bubble volume was observed to cause severe imbibition damage even with intact pericarps.
The correlation between seed weight and germination was positive and significant at 5% level. The correlations of germination with pericarp thickness, bubble volume, seed density and conductivity were highly significant, as were the correlations among these four characters. However, germination was not significantly corrected with sweetness (organoleptic).
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M.S. - Agronomy and Soil Science|
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