Subas Malla

Document Type

Thesis - University Access Only

Award Date

2005

Degree Name

Master of Science (MS)

Department / School

Agronomy

Abstract

Fusarium head blight (FHB) is an economically important disease of wheat in the U.S. This study was performed to investigate genetic diversity in advanced winter wheat genotypes for FHB resistance and gene effects in selected winter and spring genotypes. The plants were evaluated with artificial inoculation with the pathogen under field and greenhouse conditions. A total of 84 hard red and white winter wheat genotypes representing the South Dakota Advanced Yield Trial (A YT) and Crop Performance Testing (CPT) Variety Trial were evaluated for FHB resistance in a mist-irrigated field in 2003 and 2004. Forty-four genotypes, including 22 genotypes from the CPT, were also evaluated in the greenhouse in 2003. In both nurseries, genotypes significantly varied (P < 0.01) for flowering date, disease index and percent Fusarium damaged kernel (FOK) in field environments in both years. Flowering date was correlated with disease index but not with percent FOK. There was no correlation between disease index and percent FOK, except in the A YT nursery in 2003. This indicated that the disease index and percent FOK should be recorded separately to assess FHB resistance. In the CPT nursery, disease index and percent FOK significant (P< 0.01) differed between the year. The interaction was also significant (P < 0.05) between year and genotype for disease index and percent FOK. Deoxynivalenol (DON) was measured in all genotypes evaluated in the field environment in 2004. The DON content ranged from 17 .0 ppm to 56.0 ppm in advanced winter wheat genotypes. High DON in the winter wheat genotypes demonstrated that these genotypes were not resistant to mycotoxin. Nivalenol accumulation was low (<0.05 ppm) in all the genotypes. The DON content was correlated (r = 0.6 and 0.5, P < 0.05) with both percent FOK and disease index, respectively. Genotypes had high disease index values in the greenhouse compared to the field. Genotypes also varied significantly (P < 0.01) for disease index in the greenhouse. No correlation was observed between disease index in the greenhouse and the field. Diallel analysis included crosses from parents 'Ning7840', 'ND2710', 'Harding', '2137', 'BacUp' and 'Nekota' in the greenhouse evaluation and all but Nekota in the field evaluation. The F1 and F2 populations were evaluated in the greenhouse, whereas only F2 populations were evaluated in the field. In the field, F2 plants were both directly seeded and transplanted into two different nurseries. The general combining ability (GCA) effects were significant in both F1 and F2 populations across both environments. Specific combining ability (SCA) effects were significant only for the F2's in the greenhouse and direct-seeded field environments. Combining ability ratio was high and narrow sense heritability was moderate except for the direct seeded F2 populations. Ning7840 and ND2710 had large GCA effects for resistance (negative value) to FHB. 2137 had the largest GCA effect for susceptibility (positive value) to FHB. Progeny from Ning7840/ND2710 had low DON concentration. A positive and significant correlation was found between disease index and DON in both greenhouse and field environments. Though both GCA and SCA effects were significant, additive gene effects were found to be more important than non-additive gene effects in this study. Thus, crossing moderately resistant or moderately susceptible genotypes could produce transgressive segregants. A significant positive correlation between DON and each of FDK and disease index showed that genotypes selected for low FDK or disease index would also have low DON.

Library of Congress Subject Headings

Fusarium diseases of plants
Wheat -- Disease and pest resistance -- Genetic aspects

Format

application/pdf

Number of Pages

102

Publisher

South Dakota State University

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