Virulence and molecular characterization of Verticillium species from spinach
A. IGLESIAS-GARCIA (1), C. Feng (1), L. du Toit (2), K. Subbarao (3), J. Correll (1)
(1) University of Arkansas, Fayetteville, AR, U.S.A.; (2) Washington State University Mount Vernon NWREC, Mount Vernon, WA, U.S.A.; (3) University of California, Davis, Salinas, CA, U.S.A.
Phytopathology 100:S53

Verticillium wilt, caused by Verticillium dahliae, is a widespread, economically important disease affecting >200 plant species. V. dahliae is a pathogen of spinach seed crops, in which symptoms develop only after the initiation of bolting (onset of reproductive growth). The objective of this study was to characterize molecular diversity, parasitic ability (root infection, vascular colonization), and host specificity among a diverse collection of V. dahliae, V. tricorpus, Gibellulopsis nigrescens (= V. nigrescens), V. albo-atrum, and Lecanicillium fungicola (= V. fungicola) isolates. Isolates of Verticillium species from spinach and several other hosts were evaluated for variability using the ITS region, mtDNA RFLPs, and putative species-specific markers. Pathogenicity tests in the greenhouse on spinach, tomato, and cotton plants with root-dip or root-drench inoculations revealed a wide range of host specificity and virulence among isolates. Isolates of V. dahliae that originated from spinach were pathogenic on spinach, whereas some isolates that originated from other hosts were not pathogenic on spinach. Isolates of V. tricorpus and G. nigrescens recovered from spinach seed, and isolates of V. albo-atrum and L. fungicola were not pathogenic on spinach. Together, these results indicate that Verticillium and related species associated with spinach display substantial variability in parasitic ability, virulence, and pathogenicity to spinach.