Date of Award

Spring 5-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair

Kenneth J. Curry

Committee Chair Department

Biological Sciences

Committee Member 2

Brian R. Kreiser

Committee Member 2 Department

Biological Sciences

Committee Member 3

Mac H. Alford

Committee Member 3 Department

Biological Sciences

Committee Member 4

Barbara Smith

Committee Member 5

Eugene Blythe

Abstract

Cultivated strawberry, Fragaria x ananassa Duchesne, is host for many pathogens. One of the most destructive diseases of strawberry is anthracnose, whose symptoms include fruit rot, leaf and petiole lesions, crown rot, wilt, and death. Three species of Colletotrichum are considered causative agents of anthracnose diseases of strawberry. Colletotrichum acutatum causes anthracnose fruit rot, has a broad host range, and occurs in most areas of the world where strawberries are grown. Colletotrichum fragariae, the primary causal fungus of anthracnose crown rot, may infect all aboveground parts of the strawberry plant, and has restricted host and geographic ranges. Colletotrichum gloeosporioides causes symptoms indistinguishable from those caused by C. fragariae but has much broader host and geographic ranges.

Plant breeding programs generally require many years to produce commercially acceptable disease resistant cultivars; however, molecular tools may be used to identify genes that convey disease resistance and decrease the overall time required to develop new disease resistant cultivars. Two disease resistance genes have been identified in strawberry through controlled crosses: Rpf1 for resistance to Phytophthora fragariae and Rca2, a dominant gene that has been suggested to provide resistance to pathogenicity group 2 (q.v.) of C. acutatum (Van de Weg et al., 1997; Denoyes-Rothan et al., 2005). Two sequence characterized amplified region (SCAR) markers for the Rca2 resistance allele were found in several European and U.S. cultivars and, although there was not a perfect association with anthracnose resistance, these SCAR markers provide a unique set of tools to use in screening for anthracnose-resistant genotypes in strawberry breeding programs.

The primary goal of this research was to establish the resistance or susceptibility of 81 strawberry germplasm lines to all three anthracnose-causing Colletotrichum species and to determine the degree to which an association exists between the resistance or susceptibility of these plants to the presence or absence of the Rca2 resistant allele SCAR markers. A secondary goal of this research was to determine if a detached leaf assay could be used to define the resistance or susceptibility of strawberry plants to anthracnose, thus providing an efficient, non-destructive method to screen strawberry germplasm for anthracnose resistance.

ORCID ID

0000-0002-3451-4718

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