Author ORCID Identifier

https://orcid.org/0009-0004-6238-5249

Date Available

8-1-2024

Year of Publication

2024

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Agriculture, Food and Environment

Department/School/Program

Plant and Soil Sciences

Advisor

Dr. Seth DeBolt

Abstract

Maize stalk lodging reduces grain yields due to the permanent breakage or deformation of stalk tissue before grain harvest. To reveal new insights into the complex problem of maize stalk lodging, this dissertation will examine three primary objectives. First, the direct, diurnal influence of turgor pressure will be shown to have only marginal effects on stalk bending strength, a key trait associated with stalk lodging resistance. Up to a dozen individual stalks, grown to physiological maturity within the same field, were tested using a DARLING testing device. In parallel, stalk turgor status as measured by leaf water potential and turgor pressure were tracked within individuals of the same field. Experimental replicates spanning two years, three morphologically and physiologically distinct cultivars, and assessments across developmental stages ranging from late vegetative to the hard dough stages of development revealed only marginal associations between stalk turgor status and either stalk bending strength or flexural stiffness. Linear and non-linear regression analysis both confirmed only marginal effects on stalk stiffness and bending strength due to our measures of stalk turgor status under field conditions.

While turgor status has limited influence on stalk stiffness and bending strength, several whole stalk and internodal internodal-level phenotypes collected from approximately 30,000 individual stalks representing over 500 genotypes of maize inbred lines were queried to identify ordinal positions of phenotypes most associated with stalk mechanical strength. Morphological and mechanical traits associated with basal internodes were shown to best predict stalk strength. Finally, the phenotypes most predictive of stalk strength underwent an iterative, multi-trait GWAS (Genome Wide Association Study) process utilizing a selection of biallelic markers from a recently published, comprehensive genomic dataset. Significantly associated markers were identified and linked to genes based on ordinal proximity. The compiled gene list was compared against previously published datasets, confirming both the complexity of the genetics underlying stalk lodging resistance and highlighting several key genes and metabolic pathways with global and distinct associations with traits associated with stalk lodging resistance in maize. In-silico functional annotations hint at numerous previously characterized and unexplored sources of genetic tractability for the improvement of stalk lodging resistance in maize and underscore the importance of growth regulation as a key driver of stalk lodging resistance. Ultimately, more work remains to be done to validate these findings, but the work performed in this dissertation highlights the genetic tractability of maize stalk lodging resistance.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.346

Funding Information

This work was funded in part by the National Science Foundation (Award #1826715) and the United States Department of Agriculture—Hatch cooperative agreement.

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