Author ORCID Identifier

https://orcid.org/0000-0002-8856-9087

Year of Publication

2021

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Agriculture, Food and Environment

Department/School/Program

Plant Pathology

First Advisor

Dr. Nicole Gauthier

Second Advisor

Dr. Christopher Schardl

Abstract

Bipolaris leaf spot (BLS) disease emerged with the reintroduction of hemp as a crop in the United States following more than 60 years of prohibition. The causal agent was identified as Bipolaris gigantea (=Drechslera gigantea), a known minor pathogen of monocots which causes devastating disease on hemp. BLS has been confirmed throughout Kentucky and reported in 15 states. Morphology and growth characteristics of isolates from eight counties across Kentucky were similar with the exception of some isolates producing protoperithecial-like structures. Phylogenetic and whole genome analysis indicated that some isolates were haploid, containing a single allele at each gene (RPB2, TEF1) and only one mating type idiomorph. Others were “heteroploid,” having two alleles at each gene, both mating type idiomorphs, and an assembled genome approximately twice the size of haploid genomes. The phylogenies suggested that most heteroploids had a genome similar to most haploids, plus a related genome that was closely related but phylogenetically distinct. Haploids and heteroploids caused indistinguishable disease symptoms on field hemp and were both equally likely to be isolated from samples. The implications of the genetic diversity of populations causing BLS are unknown, as is the influence on the implementation and development of management strategies.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.122

Available for download on Tuesday, May 17, 2022

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