Investigation on downy mildew of leaf mustard (Brassica juncea (L.) Coss), caused by Peronospora parasitica (Pers.). Fr.
1985
Chen, Yi-Sung
Peronospora parasitica (Pers.) Fr., which causes downy mildew of Chinese leaf mustard (Brassica juncea (L.) Coss), has been found all year-round in Thailand, especially in Nakorn Pathom and Pathum Thani Provinces. This pathogen attacks other important cruciferous plants including Chinese kale, Chinese cabbage, cabbage, Chinese radish, rape, and broccoli. Leaf mustard (B. juncea var. capitata Tsen et Lee) was the most suseptible to this disease. In this study, the morphology of P. parasitica was observed through SUMP microscopic printing, aniline blue in lactophenol staining and the scanning electron microscopic methods. The development of conidiophores initiated within 2 hours, elongation at 4 and 6 hours; branched at 8 hours, young conidia formed at 10 hours, and most of conidia mature at 12 hours of incubation. Sporulation and germination were highly influenced by the atmospheric temperature and humidity. The optimum temperatures for sporulation and spore germination were 20 deg C. and 10 deg C. respectively. The optimum humidity was 100 percent RH for both of these morphogenic processes
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