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Fort Collins, CO, United States

Webb K.M.,Sugar Beet Research Unit | Case A.J.,Colorado State University | Brick M.A.,Colorado State University | Otto K.,Colorado State University | Schwartz H.F.,Colorado State University
Plant Disease | Year: 2013

Fusarium oxysporum f. sp. betae causes Fusarium yellows in sugar beet (Beta vulgaris). The F. oxysporum population from sugar beet can be highly variable in virulence and morphology and many isolates are nonpathogenic. Rapid and reliable methods to identify pathogenic isolates from nonpathogenic F. oxysporum generally are unavailable. Little is known about nonpathogenic isolates, including the role they may play in population diversity or virulence to sugar beet. Sugar beet is often grown in rotation with other crops, including dry edible bean (Phaseolus vulgaris) and onion (Allium cepa), with F. oxysporum able to cause disease on all three crops. Thirty-eight F. oxysporum isolates were collected from symptomatic sugar beet throughout the United States to investigate diversity of the F. oxysporum population and the influence of crop rotation on pathogenic variation. These isolates were characterized for pathogenicity to sugar beet, dry edible bean, and onion, as well as vegetative compatibility. Pathogenicity testing indicated that some F. oxysporum isolates from sugar beet may cause disease on onion and dry edible bean. Furthermore, vegetative compatibility testing supported previous reports that F. oxysporum f. sp. betae is polyphyletic and that pathogenic isolates cannot be differentiated from nonpathogenic F. oxysporum using vegetative compatibility. Source

Covey P.A.,Sugar Beet Research Unit | Kuwitzky B.,Sugar Beet Research Unit | Hanson M.,Sugar Beet Research Unit | Webb K.M.,Sugar Beet Research Unit
Phytopathology | Year: 2014

Sugar beet (Beta vulgaris) Fusarium yellows is caused by Fusarium oxysporum f. sp. betae and can lead to significant reductions in root yield, sucrose percentage, juice purity, and storability. F. oxysporum f. sp. betae can be highly variable and many F. oxysporum strains isolated from symptomatic sugar beet are nonpathogenic. Identifying pathogenicity factors and their diversity in the F. oxysporum f. sp. betae population could further understanding of how this pathogen causes disease and potentially provide molecular markers to rapidly identify pathogenic isolates. This study used several previously described fungal effector genes (Fmk1, Fow1, Pda1, PelA, PelD, Pep1, Prt1, Rho1, Sge1, Six1, Six6, Snf1, and Ste12) as genetic markers, in a population of 26 pathogenic and nonpathogenic isolates of F. oxysporum originally isolated from symptomatic sugar beet. Of the genes investigated, six were present in all F. oxysporum isolates from sugar beet (Fmk1, Fow1, PelA, Rho1, Snf1, and Ste12), and seven were found to be dispersed within the population (Pda1, PelD, Pep1, Prt1, Sge1, Six1, and Six6). Of these, Fmk1, Fow1, PelA, Rho1, Sge1, Snf1, and Ste12 were significant in relating clade designations and PelD, and Prt1 were significant for correlating with pathogenicity in F. oxysporum f. sp. betae. © 2014 The American Phytopathological Society. Source

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