Document Type

Thesis - University Access Only

Award Date

1994

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Jackie C. Rudd

Abstract

Six homozygous genotypes of spring wheat (Butte 86, 2375, SD3116, SD3080, Sumai 3, and Fan 1), with different levels of resistance to Fusarium head blight, more commonly known as scab, were crossed in a modified half diallel design. Parents, F1, and F2 progenies were inoculated at anthesis with a pathogenic isolate of Fusarium graminearum (Schw) under greenhouse conditions. Disease severity was assessed on the basis of a 0-5 scale. Notes were taken three times: 7, 14, and 21 days after inoculation, to obtain area under disease progress curves (AUDPC). Combining ability analysis, following Griffing's Method 4 Model 1, showed a large general combining ability (GCA)/specific combining ability (SCA) ratio, both in F1 and F2, which indicated that resistance to Fusarium head blight was uniformly transmitted to the progeny of all crosses. Sumai 3 and Fan 1 had the largest GCA for resistance to disease spread, and Butte 86 the largest for susceptibility. The degree of resistance in the F1, as high or higher than the more resistant parent in those arrays of Sumai 3 and Fan 1, suggested the presence of non-additive effects. Sumai 3 presented consistently large values of GCA, in both F1 and F2 progeny; Fan showed the largest GCA in F1 but was not superior to other genotypes, except Butte 86, in F2. These results indicated that even though Sumai 3 and Fan 1 are both similarly resistant, resistance was transmitted more uniformly from Sumai 3 to its array, that means, Sumai 3 is a better combiner. The segregation pattern for Fusarium head blight resistance of Sumai 3 array in F2 was indicative of control by a small number of dominant genes.

Library of Congress Subject Headings

Wheat -- Disease and pest resistance
Wheat-scab

Format

application/pdf

Publisher

South Dakota State University

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Rights Statement

In Copyright