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Genetic Dissection of Shoot Architecture Traits in Soybean (Glycine max L. Merr)

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posted on 2024-04-23, 03:53 authored by Chancelor B ClarkChancelor B Clark

Shoot architecture in plants refers to the spatial layout of the above-ground organs, which develops through complicated networks of genetic and environmental interactions. Modification of shoot architecture has been a major driver of yield increases in many crop species, but knowledge of the genetic control of shoot architectural traits in soybeans remains incomplete. Chapter 1 provides an overview of soybean shoot architecture traits, encompassing stem growth habit, plant height, branch number, branch angle, petiole angle, leaf size, and leaf shape. The review not only delves into the genetic basis of these traits but also underscores their importance, identifies knowledge gaps, and outlines avenues for future research leveraging cutting-edge technologies in gene editing, phenomics, and genomics. Chapter 2 describes the identification and mapping of a novel locus modulating semideterminate and indeterminate stem growth habits, dt3, on chromosome 10. Allelic and haplotypic analysis of the USDA soybean germplasm collection was conducted to find semideterminate soybean accessions which did not carry known stem termination alleles at the dt1 and Dt2 loci. Mapping populations were developed by crossing several of these accessions to indeterminate cultivars, and initial mapping revealed a region on chromosome 10 common to all populations. dt3 is a recessive mutation resulting in semideterminate growth habits, and this locus displays a unique pattern of inheritance compared with known stem growth habit genes in soybean or other plant species. Chapter 3 describes the identification of Dt4, a novel semideterminacy allele of FT5a originating from wild soybean. Dt4 was identified by quantitative trait locus (QTL) mapping using a population developed by crossing LD00-3309, an indeterminate cultivar with a semideterminate recombinant inbred line (RIL1890) originating from a cross between wild and domesticated soybean. A combination of fine mapping and candidate gene expression analysis pinpointed the allele of the floral inducer FT5a in RIL1890 as Dt4 for semideterminacy. Intriguingly, when the Dt4 allele was transformed into LD00-3309, it resulted in not only semideterminate stem growth habit but also narrowed leaf shape. Chapter 4 describes the identification and mapping of GmBa1, a novel locus specifying soybean branch angle, in which wide branch angle is completely dominant over narrow branch angle. This locus was identified in two distinct biparental mapping populations. The findings described in this dissertation deepen our understanding of genetic mechanisms underlying shoot architecture traits and provide a valuable resource for breeders looking to modify these traits for soybean improvement.

History

Degree Type

  • Doctor of Philosophy

Department

  • Agronomy

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Jianxin Ma

Additional Committee Member 2

Mitchell R. Tuinstra

Additional Committee Member 3

Katy Martin Rainey

Additional Committee Member 4

Michael V. Mickelbart

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