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Pathogenicity, vegetative compatibility and genetic diversity of Verticillium dahliae isolates from sugar beet

Strausbaugh, Carl A., Eujayl, Imad A., Martin, Frank N.
Canadian journal of plant pathology 2016 v.38 no.4 pp. 492-505
Verticillium dahliae, Verticillium wilt, cultivars, genetic variation, haplotypes, leaves, loci, mitochondria, pathogenicity, pathogens, potatoes, roots, sugar beet, sugars, surveys, Idaho
Verticillium wilt of sugar beet is a disease that has received very little attention, but which has been reported to reduce sugar quality. A survey of sugar beet fields with wilt symptoms was conducted in 2007 (5 roots from each of 40 fields) and 2008 (5 roots from each of 45 fields) in Idaho. Verticillium dahliae was isolated from all root samples. From a collection of 106 V. dahliae sugar beet isolates, all were of the MAT1-2 mating type. The vegetative compatibility grouping (VCG) was evaluated for 93 of these isolates and 95, 3, 1 and 1% were VCG 4A, VCG 2B, VCG 4B and non-compatible, respectively. All the VCG 4A isolates had the same mitochondrial haplotype based on sequencing of cox3 to nad6 and cox1 to rnl loci, while the VCG 2B isolates had two haplotypes. Pathogenicity tests on sugar beet cultivar ‘Monohikari’ revealed that the VCG 4A isolates produced more foliar symptoms (P < 0.0001) than VCG 1, 1A, 2A, 2B, 3 and 4B isolates, but none of the VCGs consistently reduced root and foliage weight. Since V. dahliae VCG 4A isolates have also been reported as a pathogen of potato in North America, rotating sugar beet fields with potato could be a concern.