Mohamed F. R. Khan

Characterization of Fusarium secorum, a new species causing fusarium yellowing decline of sugar beet in north central USA.

This study characterized a novel sugar beet (Beta vulgaris L.) pathogen from the Red River Valley in north central USA, which was formally named Fusarium secorum. Molecular phylogenetic analyses of three loci (translation elongation factor1α, calmodulin, mitochondrial small subunit) and phenotypic data strongly supported the inclusion of F. secorum in the Fusarium fujikuroi species complex (FFSC). Phylogenetic analyses identified F. secorum as a sister taxon of F. acutatum and a member of the African subclade of the FFSC. Fusarium secorum produced circinate hyphae sometimes bearing microconidia and abundant corkscrew-shaped hyphae in culture. To assess mycotoxin production potential, 45 typical secondary metabolites were tested in F. secorum rice cultures, but only beauvericin was produced in detectable amounts by each isolate. Results of pathogenicity experiments revealed that F. secorum isolates are able to induce half- and full-leaf yellowing foliar symptoms and vascular necrosis in roots and petioles of sugar beet. Inoculation with F. acutatum did not result in any disease symptoms. The sugar beet disease caused by F. secorum is named Fusarium yellowing decline. Since Fusarium yellowing decline incidence has been increasing in the Red River Valley, disease management options are discussed.

Sugar Beet Diseases: Cercospora Leaf Spot

Sugar beet (Beta vulgaris L.) was first commercially processed in 1802 in Cunern, now Germany, and since that time has become a provider of 25 % of the world’s sucrose requirement. Cercospora beticola causes Cercospora leaf spot which is one of the most damaging foliar fungal pathogens of sugar beet especially in warm and humid growing areas. Crop rotation, incorporation of infected plant debris, use of partially resistant varieties, and timely application of fungicides are combined to manage C. beticola. Fungicides are critical for disease control in areas where the pathogen is endemic. Most classes of fungicides have been used to control C. beticola; however, prolonged use and sometimes overuse have resulted in the pathogen developing resistance and rendering the fungicide ineffective in the field. In Minnesota and North Dakota, the United States, the use of different modes of action in a rotation program and/or fungicide mixtures comprising different modes of action in rotation always with different chemistries has contributed to successful control of the disease over the past 15 years, a reduction in the number of fungicide applications, and savings in fungicide use of

Characterization of cytochrome b from European field isolates of Cercospora beticola with quinone outside inhibitor resistance

14 million annually compared to the last epidemic in 1998.