Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department

Biology and Microbiology

First Advisor

Donald Auger

Keywords

doubled-haploid Ga1-s maize, modifiers of gametophyte factor, polymorphism, quantitative traits

Abstract

The project was designed to conduct two independent projects. The first project was to identify the genomic localization of the modifiers of the maize gametophyte factor (Ga1-s) and the second project was to establish and identify heritable polymorphic lines that have descended from a single doubled-haploid B73 plant. The objectives were (1) to search for modifier genes and loci on the maize chromosomes for the trait and determine genetic effects of them using QTL mapping; (2) to demonstrate the heritable polymorphism of the quantitative traits emerged from the descendants of a single doubled-haploid maize plant. Regarding the QTL mapping of the modifiers of the maize gametophyte factor; two maize lines had been identified that are polymorphic to B73 relative to Ga1-s resistance to ga1 pollen: Ky21 shows less resistance and M162w shows greater resistance. The recombinant inbred lines (RILs) of both Ky21 and M162w have already been developed and genotyped for both of these with B73. 200 RILs each of Ky21 and M162w were sown in summer of 2014 and crossed with pollen from plants homozygous for Ga1-s. The strength of Ga1-s in each F1 line was evaluated by pollinating with Rscm2 ga1 pollen the first day and allowing open pollination on the second day. A strong effect of Ga1-s is indicated if the resulting ear has few or no blue kernels and a weak effect is ear being heavily contaminated with blue kernels. A standardized scale of contamination was established to score ears. Composite interval mapping method was conducted for the QTL analysis. RILs (B73 X Ky21) show QTLs on chromosome 1S and 4S while RILs (B73 and M162w) shows QTLs on 5L and 10L. On doubled-haploid maize, the source material was provided by James A. Birchler, University of Missouri. One kernel from this ear was used as a source germplasm for this project and was designated as S0. The diploid progeny resulting from self-pollination of the S0 plant was designated as S1. Similarly, one diploid progeny from self-pollination of an S1 plant was designated as S2 and so on to the S3 generation. From the S3 generation, ten random seeds from a uniform good-looking ear were selected to become the source of separate descent lineages. Each lineage was maintained through selfing and one progeny was selected for advancement to the next generation. In the summer of 2014, we planted the seed for two sequential generations from each of ten lineages. These were planted in triplicate in a randomized complete block design. The resulting plants were evaluated for 15 quantitative traits (plant height, number of tassel branches, 100 grains weight, etc.). A partial replication of experiment of 2014 was conducted in 2015. A heritable polymorphism for any particular trait is indicated if there is no significant difference between the two generations of a lineage but the lineage is significantly different from other lineages. Number of tassel branches, total number of kernels per ear, days to pollen shed and days to silk emergence has demonstrated heritable polymorphism.

Library of Congress Subject Headings

Corn -- Genetics.
Corn -- Genome mapping.
Genetic polymorphisms.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

89

Publisher

South Dakota State University

Rights

Copyright © 2016 Vivek Shrestha

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