Genetic differentiation between Verticillium dahliae populations from asymptomatic and symptomatic hosts
M. d. JIMENEZ-GASCO (1), G. M. Malcolm (1), L. d. Bautista-Jalon (1), B. K. Gugino (1). (1) The Pennsylvania State University, University Park, PA, U.S.A.
<i>Verticillium dahliae</i> (Vd) causes disease on over 400 hosts. Monocotyledonous crops have been traditionally considered to be non-hosts of Vd, and cereal species have been used in rotations as a strategy to manage Verticillium wilts. When sampling oats planted in with potatoes in PA fields with a history of Verticillium wilt, we found Vd growing endophytically; the fungus was isolated from surface-disinfested internal stem tissue of asymptomatic oat plants. A population genetics approach was used to examine Vd obtained from potato and oats grown in rotation in the same fields. Microsatellite marker analysis showed that the populations were significantly different. While at least seven distinct Vd genotypes were present in the populations from potato samples, only one of those genotypes was consistently found associated with oats, in different sampling years and from different fields. These results indicate that the interaction between Vd and oats is highly specialized; not every Vd genotype seems to be able to establish an endophytic relationship with oats and possibly other monocots, but this is potentially restricted to certain Vd genotypes. The dual role of Vd, pathogenic on certain plants and endophytic on others, raises interesting questions about the biology, ecology, persistence, and spread of this fungus, and has important potential implications in the management of Verticillium wilts in agroecosystems.
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