Document Type

Dissertation - Open Access

Award Date

2023

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Shaukat Ali

Abstract

Pyraclostrobin, a QoI fungicide, is extensively used in the management of fungal leaf spot diseases. In this study, 215 P. tritici-repentis isolates collected from wheat fields in South Dakota were evaluated for their sensitivity to Pyraclostrobin. Of 215 isolates, 48 isolates (22%) exhibited insensitivity based on G143A mutation and EC50 values using spore germination assay. Our results indicate reduced sensitivity to insensitivity to pyraclostrobin in some isolates suggesting regular monitoring of the P. tritici-repentis population to QoI fungicides is essential to track the evolution of insensitive population. Spelt wheat (Triticum spelta L.) is an ancient cereal that is gaining small grain growers’ attention under an organic setup due to its high protein content, high fiber, and other health benefits. In this study, two hundred-eight spelt accessions from twenty countries were screened against leaf spot diseases and leaf rust at the seedling stage in the greenhouse. The genotypes exhibited varying responses ranging from susceptible to moderately susceptible, moderately resistant, and resistant. Spelt accessions resistant to leaf rust and leaf spots will be further evaluated for the agronomic traits in the field, and results will be shared with the growers to assist in selection of superior spelt genotypes. ToxA, a necrotrophic effector has been identified from the fungus Pyrenophora tritici-repentis that causes tan spot and was later identified from Parastagonospora nodorum and P. avenaria tritici. Recently, the ToxA gene has been identified in the fungus Bipolaris sorokiniana causing spot blotch in Australia and the winter wheat region of southcentral Texas. In this study, we have tested if B. sorokiniana population of South Dakota is having ToxA gene (BS ToxA) like P. tritici-repentis and P. nodorum. 53.5% (n=68) of 127 isolates amplified the ToxA gene. Further, the culture filtrates of isolates with the ToxA gene produced necrosis symptoms in ToxA sensitive wheat cultivars. Our results indicate that there is a diverse population of B. sorokiniana prevalent on wheat in South Dakota. To our knowledge, this is the first report of ToxA (BS ToxA) producing B. sorokiniana isolates in South Dakota.

Library of Congress Subject Headings

Spelt -- Diseases and pests.
Spelt -- Disease and pest resistance.
Fungicide resistance.
Plants -- Effect of fungicides on.
Fungal diseases of plants.
Phenotype.

Publisher

South Dakota State University

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Rights Statement

In Copyright