Date of Award

Fall 9-5-2025

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Bioinformatics & Computational Biology

First Advisor

Michael Grillo

Abstract

Legumes are an incredibly diverse and agriculturally important family of plants. They have a special relationship with symbiotic bacteria known as rhizobia which fix nitrogen into ammonia within nodules on their roots. Astragalus is the largest plant genus on Earth, and the species Astragalus lentiginosus is extraordinarily diverse, consisting of approximately 40 varieties. However, the rhizobia of A. lentiginosus have never been studied. In this study, root nodules were extracted from 17 varieties of A. lentiginosus to obtain rhizobial strains and metagenomes. A. lentiginosus primarily associates with rhizobia from the genera Mesorhizobium and Allomesorhizobium. There was little evidence of horizontal gene transfer of the symbiosis genes between the two genera. Rhizobia were more closely related based on host variety for Mesorhizobium or geographic distance for Allomesorhizobium. Several of these rhizobia belong to novel species, warranting further analysis and demonstrating the potential wealth of taxa hidden within wild legumes.

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