Document Type

Thesis - University Access Only

Award Date

2001

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy

Abstract

Crown rust, caused by Puccinia coronata f. sp. avenae, is a major foliar disease of cultivated oat. Control of oat crown rust has primarily been through the use of single gene-resistance (designated Pc genes). However, most Pc genes have limited durability because the pathogen adapts and produces new biotypes capable of overcoming the initial resistance. The main objectives of this study were to (i) identify gene interactions that may provide durable resistance to crown rust by pyramiding defeated Pc genes, and (ii) develop populations that may provide genetic crown rust resistance in oat. Single, double, and complex crosses were developed to generate populations with a large number of combined genes. Progenies of these populations were subjected to evaluations of rust reactions at the seedling stages under greenhouse conditions using a bulk of highly virulent crown rust races. The F3 populations were also evaluated for adult reactions under field conditions with natural infection. It was frequently observed that many of the complex and double crosses, especially in the field study, exhibited mean disease scores approximately intermediate between their parents. However, significant increases in resistance were indicated in two of the complex crosses (DG2-34, DG46-29) and two of the double crosses (DG3498, DG698) compared to their parental populations in both the greenhouse and field experiments. One complex population, DG51-54, demonstrated increases in resistance than most of its combinations. Along with populations DG2-34, DG46-29, DG3498, and DG698, cross DG51-54 consistently ranked in the top ten populations that conferred the lowest disease ratings. The single crosses also predominantly conferred intermediate resistance to that of their parents, although, some interesting two gene combinations were observed. Cross 64-63 may have displayed seedling resistance and cross 60-61 may have exhibited adult resistance. It could be concluded that selection in the above mentioned complex and double crosses to improve genetic resistance and the identification and utilization of such positive Pc gene interactions may provide an advantage for increased durability and thus a suitable method for developing highly resistant oat cultivars.

Library of Congress Subject Headings

Oats -- Disease and pest resistance -- Genetic aspects

Format

application/pdf

Number of Pages

105

Publisher

South Dakota State University

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