Host Range, Biological Variation, and Phylogenetic Diversity of Eutypa lata in California

The objectives of this study were to investigate the host range of Eutypa lata in the major grape-growing regions in California and to analyze the phenotypic variation and phylogenetic diversity of E. lain isolates. Perithecia of E. lata were found on grapevines, in apricot, almond, cherry, apple, and pear tree orchards, and on ornamentals (oleander) and native plant species (California buckeye, big leaf maple, and willow). Multigene phylogenies of ribosomal DNA internal transcribed spacer, beta-tubulin, and RPB2 genes confirmed the identity of E. law recovered from the various host plants but also revealed sequence differences among isolates. The intraspecific phylogenetic diversity of E. law did not correspond to geography or source of isolation, and intraspecific groups were not consistent across the different DNA phylogenies. Significant phenotypic variation also was detected among E. law isolates, including ascospore and conidium length as well as level of aggressiveness on grapevines. Pathogenicity studies proved that all isolates were infectious to grapevine, suggesting that the native vegetation surrounding vineyards can serve as inoculum sources that may constitute an important element in the epidemiology of Eutypa dieback in grapevines.