Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Maureen Donnelly

First Advisor's Committee Title

co-committee chair

Second Advisor's Name

Eric von Wettberg

Second Advisor's Committee Title

co-committee chair

Third Advisor's Name

Heather Bracken-Grissom

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Giri Narasimhan

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Joel Trexler

Fifth Advisor's Committee Title

committee member

Sixth Advisor's Name

Carl Lewis

Sixth Advisor's Committee Title

committee member

Keywords

domestication, phylogenomics, genomics, mango, Mangifera

Date of Defense

4-27-2018

Abstract

Domesticated species are vital to global food security and have also been foundational to the formulation and advancement of evolutionary theory. My dissertation employs emerging molecular genomic tools to provide an evolutionary context for crop improvement. I begin by providing a contemporary perspective on two components of domestication biology that have long been used to improve crop production: wild relatives of crop species and grafted rootstocks. First, I propose a method to systematically introgress crop wild relative diversity into crop breeding programs. Then, I explore rootstocks, the lesser-known half of the perennial crop equation, documenting prevalence and diversity, cataloging rootstock traits under selection, and discussing recent advances in rootstock biology. Both crop wild relatives and rootstocks remain largely underutilized resources and hold great promise for agricultural innovation.

While humans have domesticated thousands of plant species, research has largely focused on annual crops, to the exclusion of perennials. To improve our understanding of how tree species respond to domestication, I examine the evolution and domestication of one of the world’s most important perennial tropical fruit crops, the mango, Mangifera indica, and its wild and semi-domesticated relatives. I generated a dataset suitable for studying Mangifera across evolutionary time using double digest restriction site associated DNA sequencing (ddRADseq). I present a multilocus phylogeny that informs the classification of Mangifera and reveals, for the first time, the evolutionary relationships of wild, semi-domesticated, and domesticated species in the genus. Narrowing my focus to the intraspecific level, I examine how the introduction of M. indica into regions of the world impacted its genetic diversity. My results show M. indica maintained high levels of genetic diversity during its introduction into the Americas. However, the novel diversity I detect in Southeast Asian mango cultivars suggests that M. indica has a more complex domestication history than previously assumed. I also find evidence that M. indica hybridized with multiple congeners following its introduction into Southeast Asia, forming two hybrid lineages that may be maintained by clonal polyembryonic reproduction. Collectively, my research provides a comprehensive framework for understanding the evolution and domestication of a tropical tree crop of global economic importance.

Identifier

FIDC006564

Available for download on Thursday, April 02, 2020

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