Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Previously, only one system, the Ac-Ds system, has been found to cause chromosomal rearrangements such as duplications, deficiencies, inversions, and translocations. This study is about another system (En controlling system) that causes specific breaks on chromosome 3 of maize;An exceptional derivative arose from an original heavily mutating allele at the a locus (a-m (dense)) showing a (--->) A mutation. This derivative, in addition to the heavy a (--->) A mutation, showed chromosome breakage that is displayed as colored shrunken sectors when crossed to another allele, a-m-1 (a-m-1 sh2). These colored shrunken sectors illustrate a multiple gene loss event on chromosome 3;The goals of this study are to characterize and to determine the extent of this recurrently occurring multiple gene loss. The tests conducted provide proof that the loss includes at least the A function, the En element, and the Sh2 gene. In addition, a distal Et gene is also seen to be lost. Tests for the possibility of the presence of Ac in the a-m En Sh2 complex indicate the Ac is not present and the loss of a-m En Sh2 is only due to En. This unique En was designated as En61138-3;High heritability of the frequency of En61138-3 Induced Loss Event (En61138-3-ILE) was found ranging from 70-90%. As a result, it showed that significant responses to bidirectional selection can occur on high or low loss frequency of En61138-3-ILE. The high heritability is primarily due to the frequency of small-sized loss sectors. Early-occurring loss events as established in this study are a random consequence of the loss events according to the Poisson distribution;A number of modifiers, segregating independently, were found in the population of En61138-3. The frequency of En61138-3-ILE increases in proportion to the frequency of modifiers in a population. These modifiers can be maintained through selfing and sib-cross. The patterns of En61138-3-ILE and the frequency of En61138-3-ILE per kernel are also affected by these modifiers. Effects of planting dates and plant tissues (main stalk and tiller of the same plant) were not significant on the frequency or patterns of En61138-3-ILE.



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Yih Ching Huang



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381 pages