Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department

Biology and Microbiology

First Advisor

Donald Auger

Keywords

cross-incompatibility, maize, male gametophyte mutants, plutonium-beryllium mutagenesis, tcb1, teosinte crossing barrier 1

Abstract

This thesis is split into two independent projects both involving the male gametophyte generation of maize. The first project looks at how pollen interacts with the female gametophyte to reduce its transmission in cross-incompatible reactions controlled by the unilateral cross-incompatibility system, teosinte crossing barrier 1. The second project explores two plutonium-beryllium induced male gametophyte mutants and attempts to uncover their genetic basis.

Identification of QTL Modifying the Activity of the Tcb1-s Locus
Teosinte crossing barrier 1 (Tcb1) is a unilateral cross-incompatibility system present in maize that provides a pre-zygotic pistil barrier to plants carrying Tcb1-s (strong allele) from pollen not carrying that allele (tcb1), the reciprocal cross however, is unencumbered. Due to this pollen specificity, Tcb1-s can be useful to organic, sweet corn, or maize landrace farmers to prevent cross-contamination from occurring between fields. Kermicle (personal communication) observed that the Tcb1-s allele requires the action of modifiers to confer a stronger pistil barrier. Such modifiers are present in the F1s of the maize inbred lines B73 and Mo17 who are polymorphic in Tcb1-s activity. In this study factors modifying the Tcb1-s locus were tracked using the F1s of the intermated B73 Mo17 recombinant inbred lines with W22 Tcb1-s/Tcb1-s. The ability of the Tcb1-s pistils to reject tcb1 pollen containing R1 C1 color markers and accept its own self-type pollen was measured. Eight QTLs were detected on chromosome arms 2S, 2L, 3S, 4S, 7S, 7L, 8L, and 10L explaining a total of 34.8% of the overall phenotypic variability. Knowledge of the QTL interacting with Tcb1-s could assist in the introgression of both Tcb1-s and positive acting modifiers so that Tcb1-s activity is maximized.

Characterization and Sequencing of Two Plutonium-Beryllium Induced Reduced Gametophyte Transmission Mutants in Maize
Two mutants generated by exposure to a plutonium-beryllium source had reduced transmission of the male gametophyte and not the female gametophyte. Both mutations are linked to the R1 color marker. We sequenced and compared both deletion haplotypes to the B73 reference genome. We detected a 4.5 Mb region linked to the R1 locus that may contain the mutation causing the reduced transmission phenotype. In the PB2 mutant we found 25 candidate genes impacted by deletions, one of which is a calcium-dependent protein kinase potentially involved in pollen tube tip growth. Candidate genes for PB1 remain elusive. These results could shed light on the short-lived male gametophyte generation of maize and could be applied to plant breeding to create male sterile lines

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

120

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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