Peronospora viciae. [Descriptions of Fungi and Bacteria].
Abstract A description is provided for Peronospora viciae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Vicia faba, V. sativa, Lathyrus sativus, Pisum sativum, P. arvense and other related forms. DISEASE: Downy mildew of peas. Downy greyish-violet growth forms on the under surface of the leaves, in patches of varying size, sometimes covering most of the leaf surface. In severely infected plants downy growth also develops on the stem and inflorescence and the leaves wither. The withered leaves contain oospores (Butler, 1918). Oospores also develop in the inflorescence and stem (32, 233; 44, 1756a). Causes severe loss, particularly in cool, wet years at temps, between 15 and 20°C and with rise of air RH (41, 295, 495; 45, 2294). Infection appears in the early stages of growth (36, 530). GEOGRAPHICAL DISTRIBUTION: World wide on peas (29, 336; 30, 20, 361, 417, 546; 33, 708; 34, 213, 271, 509; 36, 380, 519; 37, 5, 126; 39, 656; 41, 189, 216, 494; 43, 616; 44, 1031; 46, 1513i). TRANSMISSION: Initially through oospore infected soil coming from old infected plant debris (41, 272). During the growing season the spread is through wind blown sporangia (51, 4473) but they are short lived and need the proximity of the host plant for further development (Butler, 1918). Dormancy period of the oospores is also very short (41, 272).