The Disease and Symptoms
The Sclerotinia diseases are known under a variety of names and the most common of these along with some of the host plants most seriously affected are the cottony rot, white mould, or watery soft rot of beans, cabbage, carrot, eggplant, citrus, peanut, potato, stock, tobacco etc.; stem rot and timber rot of cucumber, squash, beans, artichoke, asparagus, chrysanthemum, dahlia, delphinium, peony, potato, tomato, soybean, sweet potato etc.; lettuce drop, broad bean, beet, cabbage etc.; damping off of celery, lettuce, rapeseed-mustard etc.; crown rot or wilt of sunflower, safflower, columbine, snapdragon etc.; blossom blight of narcissus, camellia etc.; pink joint of red pepper, stem canker of hollyhock, root and crown rot of clover; white blight, white rot, stem blight, stalk break and stem canker of rapeseed-mustard, head rot of sunflower, safflower, castor and dollar spot of turf grass (causal fungus previously known as Sclerotinia homoeocarpa now considered as species of Lenzia and Moellerodiscus).
A new Sclerotinia sp. strain Let-19, isolated from lettuce in central China has been reported by Li, Guo-Qing et al. (1998). Results of pathogenicity tests showed that hyphae from myceliogenically germinated sclerotia readily causes infections on uninjured lettuce leaves but only causes infections of other plant species such as rapeseed on injured leaves. The fungus is not pathogenic to Chinese cabbage (Brassica pekinensis), radish (Raphanus sativus) and carrot. The optimum temperature for growth of Sclerotinia sp. strain Let-19 is 20°C and its growth rate is slower than S. trifoliorum. Sclerotia of Let-19 germinate readily to produce stipes, but the stipes rarely develops into apothecia under diffused light. Results of preliminary electrophoretic studies of soluble proteins and enzymes shows that strain Let-19 belongs to the genus Sclerotinia and it is distinctively different from S. sclerotiorum and S. minor which are known pathogens of lettuce drop.
KeywordsStem Canker Color Plate White Mycelium Dollar Spot Bend Grass
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