Local adaptation of crop landraces

Author:

Mc Laughlin, Chloee

Graduate Program:

Plant Biology

Degree:

Doctor of Philosophy

Document Type:

Dissertation

Date of Defense:

March 25, 2024

Committee Members:

Teh-Hui Kao, Program Head/Chair
Liana Burghardt, Outside Field Member
Ruairidh Sawers, Major Field Member
Estelle Couradeau, Outside Unit Member
Jesse Lasky, Chair & Dissertation Advisor

Keywords:

local adaptation
crop landraces
genotype-environment associations

Abstract:

Abiotic and biotic pressures drive variation in evolving populations, often resulting in local adaptation. Exploring local adaptation in natural populations not only provides insight to the factors driving evolutionary processes and population-wide diversity, but also may identify adaptations that are useful for applied purposes. Landraces are traditional crop varieties that have long-term cultivation across diverse geographic and climatic regimes, culminating to localized fitness and within species variation. My dissertation explores adaptation in native crop systems of several species of cereal landraces, uncovering the mechanisms by which they adapt to their environment and the implications this adaptation has for native crop populations. In chapter two, I developed a novel modeling method to define biologically relevant clines that are predicted to drive root anatomical variation in maize landrace populations. The models, trained with a relatively small number of individuals, were in turn used to predict trait variation for a larger genotyped panel of maize landraces for the identification of putatively adaptive loci that are associated to the combined environmental gradients predicted to drive variation in root anatomy. I then linked variation in root anatomy to water banking strategies and found that maize landraces from primarily highland locations support root anatomy that slows the uptake of water, potentially as an adaptive strategy for water limited environments. Oftentimes, adaptive strategies come at a cost and may be coupled with fitness trade-offs. In chapter three, I described the impacts of variation in strigolactone profiles that are associated with resistance strategies to a parasitic plant in African sorghum landraces, but with evidence for potential trade-offs. Using CRISPR-edited plants, I gave context to the trade-offs associated with a host resistance strategy to a parasitic plant and more broadly contributed to understanding of the role strigolactones play in sorghum physiological processes, growth, and development. Much information can be gained given current genotype-environment relationships about the environmental gradients constraining the geographic distribution of adaptive loci. These relationships can further be used to identify populations that are expected to be resilient or vulnerable to changing climate. In chapter four, I used modeling methods that leverage current genotype-environment relationships to quantify disruptions to adaptation of several species of cereal crop landraces (barley, maize, rice, and sorghum) in the case of a climate catastrophe. I then identified landrace varieties best matched to specific post-catastrophic conditions, indicating potential substitutions for resilience. The diversity present in landraces of crop species is a sort of natural experiment that has been in progress for thousands of years, where selection imposed by environmental conditions and cultivation practices has given rise to native crops that are often locally adapted. By looking at broad-scale adaptation, a case study in adaptation, and predicting disruptions to adaptation, my dissertation aims to better understand the pressures by which crop landraces adapt to their environment and to gain insights of how landraces can be used as resources for agricultural improvement.