Date of Graduation

12-2016

Document Type

Thesis

Degree Name

Master of Science in Plant Pathology (MS)

Degree Level

Graduate

Department

Plant Pathology

Advisor

Jim Correll

Committee Member

Burt Bluhm

Second Committee Member

Ken Korth

Third Committee Member

Craig Rothrock

Fourth Committee Member

Ainong Shi

Keywords

Biological sciences; Anthracnose; Celery; Colletotrichum acutatum

Abstract

An anthracnose disease of celery, caused by Colletotrichum acutatum sensu lato, has been reported in the U.S. A phylogenetic analysis was conducted on a collection of isolates from celery and non-celery hosts to evaluate their taxonomic position within Colletotrichum acutatum sensu lato. Both celery and non-celery isolates were evaluated for pathogenicity on celery and for vegetative compatibility. Culture filtrates from celery and non-celery isolates were evaluated for their ability to reproduce the unusual leaf curl type symptoms. A total of 18 celery isolates were evaluated for their taxonomic placement based on analysis of the glutamine synthetase intron sequence. All isolates were closely related and belonged to the newly described species Colletotrichum fioriniae. A total of 57 isolates of Colletotrichum acutatum sensu lato and C. fioriniae, representing four previously defined genetic clades, were found to have a wide virulence spectrum on celery. All isolates originating from celery caused disease on celery whereas a wide range in virulence on celery was observed among the non-celery isolates. The 18 celery isolates grouped into six vegetative compatibility groups indicating the population was not clonal. Elevated temperatures greatly increased leaf curl symptoms in greenhouse tests. The degree of crown rot severity and the number of petiole lesions per plant were correlated with the percent of leaf curl symptoms. Although there were inconsistencies in the experiments to determine if culture filtrates can cause leave curl symptoms, some evidence indicates that certain isolates produce a metabolite that mimics the leaf curl symptoms of the disease. The filtrate may contain indole acetic acid (IAA), and purified IAA can also cause leaf curl symptoms on celery.

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