Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2008
Publication Date: 8/20/2008
Citation: Phytopathology 98:S78
Technical Abstract: Verticillium dahliae is a soil borne fungus and the primary causal agent of Verticillium wilt, which affects many crops worldwide. Many crops grown in the Salinas Valley (SV) of California, including strawberry and lettuce (Lactuca sativa), are susceptible to V. dahliae and severe outbreaks are common in certain fields. Since 1995, V. dahliae has emerged as a serious threat to lettuce production. We documented two races of V. dahliae on lettuce in SV. Currently there are no known sources of race 2-resistant lettuce and costly fumigations with methyl bromide are necessary for successful production. Besides the presence of two races of V. dahliae, little is known about the population diversity of the pathogen in SV. We have sequenced the intergenic spacer region (IGS) of over 250 isolates collected from a variety of crops and weeds grown in SV. Clustering using IGS sequences parallels virulence on differential hosts. Additionally, we identified 100 simple sequence repeat (SSR, microsatellite) motifs in the genome of the lettuce isolate VdLs.17. These SSRs include the range of motifs from di to deca-nucleotides. Primers were generated to amplify the targeted SSR motifs and SSR genotypes from the isolate collection are currently being generated. Comparisons will be made with groupings generated by IGS sequences, AFLP genotyping and virulence analyses. Spatial population genetics studies of V. dahliae in lettuce fields will ensue to elucidate the population structure of V. dahliae.