Host range of Peronospora belbahrii, causal agent of basil downy mildew, in Israel

Downy mildew in sweet basil (Ocimum basilicum L) was first recorded in Israel in late 2011. Within one year, the disease was reported all over the country, causing devastating economic damage to basil crops. The pathogen was reported to have similarly spread widely in Europe, the USA and Asia. Seed transmission and seedling trade were suggested as possible causes for rapid spread. Here, we report that some members of the Labiatae family beside O. basilicum serve as hosts of Peronospora belbahrii in Israel, thus possibly aiding its spread and survival. One hundred and two entries of Labiatae (Syn Lamiaceae), belonging to 22 genera and 53 species, were tested for sensitivity to P. belbahrii in artificial-inoculated plants in growth chambers and in field. Following artificial inoculation of potted plants in growth chambers and of field-grown plants, sporulation of P. belbahrii was observed in seven species: Salvia eigii, Salvia fruticosa, Salvia pinnata, Rosmarinus officinalis, Nepeta curviflora, Micromeria fruticosa, and Agastache spp. Six other entries (belonging to four other genera) showed small chlorotic spots but not sporulation. All other entries were symptom-free. This is the first report showing pathogenicity of P. belbahrii to Salvia, Rosmarinus, Nepeta and Micromeria spp. in Israel. Whether these species play a role in the epidemiology of basil downy mildew in Israel needs to be studied.