The Host Range of Downy Mildew, Peronospora parasitica, from Brassica oleracea, Cabbage and Broccoli Crops.

Abstract

We collected three cabbage plants infected with Peronospora parasitica in Kagawa, two broccoli plants in Mie and one broccoli plant in Tottori. Five single spore isolates from each sample were prepared, and the host range of thirty single spore isolates in total was examined. Test plants used for the host range tests were Brassica oleracea (eighteen cultivars of cauliflower, cabbage and broccoli), B. campestris (eight cultivars of Pak-choi, mizuna, rape, Chinese cabbage and turnip), B. juncea (one cultivar of leaf mustard), B. napus (one cultivar of rutabaga) and Raphanus sativus (two cultivars of Japanese radish). In all the test plants, cotyledons with hypocotyl were used for the inoculation tests. All the B. oleracea plants except two cultivars of cabbage were highly susceptible to all the tested isolates, and it is considered that this is a host species of the fungus. B. napus was moderately susceptible, and suggested to be a possible host species. B. campestris, B. juncea and R. sativus were resistant, and considered to be non-host species. Therefore, all the isolates were considered to belong to the same strain of the fungus and the strain to be specific to B. oleracea and possibly to B. napus. Among B. oleracea plants, two cultivars of cabbage cv. Golden Best and cv. YR-Sawamidori were resistant. Difference in pathogenicity was not found among the tested single spore isolates.

Synergistic/antagonistic interactions between Neopseudocercosporella, Alternaria, Leptosphaeria, and Hyaloperonospora determine aggregate foliar disease severity in rapeseed

“…Downy mildew, caused by the biotrophic pathogen H . brassicae , is a widespread obligate foliar pathogen that is endemic in oilseed Brassica ‐growing regions worldwide, including Europe (Paul et al, 1998), Japan and China (Satou & Fukumoto, 1996), and India (Nashaat et al, 2004). H .…”

“…Seed yield losses of up to 90% have been recorded because of epidemics in Australia (Fitt et al, 2006;Sprague et al, 2006;West et al, 2001;Zhang & Fernando, 2018). Downy mildew, caused by the biotrophic pathogen H. brassicae, is a widespread obligate foliar pathogen that is endemic in oilseed Brassica-growing regions worldwide, including Europe (Paul et al, 1998), Japan and China (Satou & Fukumoto, 1996), and India (Nashaat et al, 2004). H. brassicae infects its host plant particularly at the seedling stage (Mohammed et al, 2018) and pod stage (Turner et al, 2003), and can also cause systemic symptoms on floral or nonfloral parts (Thines & Kummer, 2013).…”