Date of Graduation

Fall 2019

Degree

Master of Science in Plant Science (Agriculture)

Department

College of Agriculture

Committee Chair

Chin-Feng Hwang

Abstract

Black walnut anthracnose, caused by Gnomonia leptostyla, is the most widespread and destructive disease affecting black walnut trees (Juglans nigra). Breeding cultivars for a higher resistance to anthracnose is a natural and efficient strategy for improving the health and production quality of black walnut trees. The two goals of this study were to reveal that the ‘Sparrow’ cultivar of black walnut contains a significantly higher resistance to anthracnose than the ‘Football’ cultivar when separated from environmental factors, and to expand the ‘Football’ × ‘Sparrow’ F1 mapping population to evaluate how the trait of resistance is inherited in the progeny. A phenotypic assay was conducted under laboratory conditions using an ascospore inoculum to study the difference in symptom severity between two cultivars of black walnut named ‘Football’ and ‘Sparrow.’ The fungal suspension was used to artificially infect healthy ‘Football’ and ‘Sparrow’ leaflets to measure and compare the symptomatic responses over the course of thirteen days. The difference between the two cultivars was significant at eleven days post-inoculation with a p-value < 0.0001 as the leaflets from ‘Football’ averaged 15.1% diseased surface area while the ‘Sparrow’ leaflets had an average of only 1.2% diseased surface area. However, the most significant difference was seen at thirteen days post-inoculation as the ‘Football’ leaflets averaged 31.5% diseased surface area and the ‘Sparrow’ leaflets had an average of only 3.2%. The difference in susceptibility between the two cultivars confirmed a significant resistance to anthracnose in the ‘Sparrow’ cultivar compared to the ‘Football’ cultivar. To increase the F1 mapping population, hybrid identification was performed utilizing DNA markers which resulted in a total of 52 hybrids added to the mapping population in 2019. A preliminary phenotyping procedure was applied to the existing ‘Football’ × ‘Sparrow’ F1 mapping population which provided promising segregation for the trait of resistance to anthracnose.

Keywords

black walnut, anthracnose, Gnomonia leptosyla, cultivar, resistance

Subject Categories

Agricultural Science | Forest Sciences | Genetics and Genomics | Pathogenic Microbiology | Plant Breeding and Genetics | Plant Pathology

Copyright

© Sadie D. Land

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