Fuente: PubMed "wine" Phytopathology. 2025 Dec 15. doi: 10.1094/PHYTO-06-25-0226-R. Online ahead of print.ABSTRACTOomycetes in the genus Hyaloperonospora cause severe downy mildew that threatens the quality and yield of leafy vegetables in the Brassicaceae family. During 2022 and 2023, infected plant samples were collected from multiple fields across California's Central Coast, and a total of 26 downy mildew pathogen isolates were obtained. Morphological characteristics and molecular analyses based on ITS rDNA and cox2 mtDNA gene sequences identified the isolates as Hyaloperonospora brassicae, H. diplotaxidis, and H. erucae. To further evaluate the host specificity of these pathogens, one representative isolate from each species was selected and inoculated onto a group of commonly grown Brassicaceae crops. H. brassicae, originally isolated from Brassica oleracea, caused 45.8% disease severity in B. oleracea, while disease severity was significantly lower on wild arugula (Diplotaxis tenuifolia, 1.5%) and cultivated arugula (Eruca vesicaria, 0.0%). Similarly, H. diplotaxidis, originally isolated from wild arugula, caused 26.3% disease severity in wild arugula, compared to 2.0% on cultivated arugula and 0.3% in B. oleracea. H. erucae, derived from cultivated arugula, caused 10.4% disease severity on cultivated arugula, 1.4% on wild arugula, and only 0.6% on B. oleracea. This study underscores the host specificity of downy mildew pathogens while also suggesting a potential risk of cross-infection under favorable conditions. These findings may help growers optimize their cropping systems to enhance downy mildew management in the field.PMID:41397374 | DOI:10.1094/PHYTO-06-25-0226-R