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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):The fungus appeared in the New York Zoological Park in c. 1901 and had probably been introduced from E. Asia. The American chestnut proved extremely susceptible and the disease spread with great rapidity over the whole natural range of C. dentata (Appalachian mountains). By 1922 half these chestnuts stands had been destroyed (2: 143). By 1940 the pathogen had spread over the entire range of this valuable tree (20, 183). For spread and loss in USA see (1, 30; 3, 493; 5, 642; 6, 685; 10, 276, 496; 11, 275). The disease later spread in Europe, particularly in Italy (27, 264, 589, 590; 29, 129, 182; 30, 127; 31, 358, 407; and for history and regression 56, 1751). The European chestnut (C. sativa) proved less susceptible. On young stems brown lesions form on the smooth bark, some discolouration also occurs when older stems are attacked, mainly through wounds. Lesions become sunken as bark and cambium are killed; there is swelling and cracking of the outer bark. Stem girdling causes wilt and dieback of the whole crown. Pycnidia are very abundant on the cankered bark, exuding spore tendrils in moist conditions. Pale brown, mycelial fans form in the inner bark. Water recovery shoots develop just below the lesions; but these can be destroyed in very susceptible trees. There has been considerable work on host resistance in USA using such Castanea material from Asia (5, 706; 10, 566; 14, 611; 15, 541, 692; 20, 140, 610; 21, 173; 23, 320; 25, 15; 30, 349; 32, 459; 649; 35, 558, 853; 40, 190). Other work includes studies in Italy (34, 327; 36, 218; 40, 632); France, Germany, Japan, Switzerland and Turkey (36, 434; 37, 251; 41, 176; 42, 280; 55, 4870; 58, 2406, 2407). Also on xylem blockage (17, 421); culture (28, 427, 428); vitamins and growth substances (36, 342; 38, 62); toxin (36, 796; 37, 646; 39, 246); antagonism (39, 742); sporulation (47, 28, 2609); homothallism and sexual reproduction (57, 4148, 58, 6072); association with Ceratocystis (58, 3464, 3465); bioassay for resistance (53, 1093); fungicide injection (54, 2983; 57, 4630; 59, 4775); electrical resistance in cankers (59, 466).
 
Description type:Non-original description 
Description:Cryphonectria parasitica (Murrill) Barr, Mycologia Memoir 7: 143, 1978.
Diaporthe parasitica Murrill, Torreya 6: 189, 1906.
Endothia parasitica (Murrill) P.J. Anderson & H.W. Anderson, Phytopathology 2: 262, 1912.
Anamorph: Endothiella sp.
Stromata scattered, often confluent, at first immersed in the periderm, becoming erumpent, valsoid, yellow to yellowish-brown, prosenchymatous, composed of loose weft of hyphae in the upper part and hyphae mixed with substratum cells in thelower region, up to 3 mm wide and 2,5 mm high. Perithecia grouped, more or less oblique, globose to depressed globose, up to 400 µm wide with dark brown to black, cylindrical, ostiolar beak converging through the stromatic disc and exposing the dark papilla at the surface with the pore lined on the inside by hyaline, filiform, periphyses; beaks up to 900 µm long and 200 µm wide; the perithecial wall composed of hyaline to subhyaline, pseudoparenchymatous cells towards the outside and hyaline, elongated, more or less rectangular cells towards the inside; the neck composed of vertically elongated, dark brown cells. Asci clavate to clavate-cylindrical, thin-walled, unitunicate, 8-spored, 32-55 x 7-8,5 µm, with a non-amyloid apical apparatus, loosening from the hymenium and freely floating in the centrum cavity. Ascospores irregularly biseriate in the ascus, hyaline, 1-septate, not or very slightly constricted at the septum, elliptic, usually straight, rounded at the ends, 7-12 x 3-5,5 µm. Conidiomata pseudostromatic, immersed, erumpent, separate or aggregated, yellow to yellowish-brown, globose, pulvinate, unilocular or complex and multilocular or convoluted, variable in size up to 300 µm wide, with one ostiole; the wall composed of subhyaline to pale brown, pseudoparenchymatous cells and between locules the cells are somewhat elongated. Conidiophores branched, septate, hyaline, smooth, up to 60 µm long, 1,5 µm wide, formed from the cells lining the conidiomatal cavity. Conidiogenous cells enteroblastic, phialidic, determinate, integrated, terminal or lateral, usually below a septum, hyaline, tapering at the apex with an indistinct channel and collarette. Conidia hyaline, non-septate, ellipsodial to somewhat bacilliform, 3-5 x 1-1,5 µm.
Hosts: Particularly Castanea dentata (American chestnut); other Castanea spp., Acer spp. Quercus spp., Carya ovata (shagbark hickory) and Rhus typhina (staghorn sumach), (30, 550; 33, 569; 34, 759; 42, 709; 43, 2426; 48, 946; 54, 1012; 56, 410; 57, 1569).
Disease: Chestnut Blight.
Geographical distribution: Asia (China, India (Uttar Pradesh), Japan, Korea, Turkey, USSR (Caucasus); Europe (Belgium, France, Greece, Hungary, Italy, Portugal, Spain, Switzerland, USSR (Ukraine), Yugoslavia); N. America (Canada (British Colombia, Ontario), USA (E. including Florida, California, Oregon and Washington) (CMI Map 66, ed. 4, 1973).
Physiological specialization: It was noted in Italy in the early 1950's that susceptible chestnut trees remained healthy even after attack by the fungus. Later, avirulent forms of the fungus were isolated (hypovirulent strains) which, when inoculated into cankers, cured the disease. The virulent strains seemed to become converted to the hypovirulent one. Subsequent work has been reviewed (60, 2792). Hypovirulence is a condition(s) that reduces pathogenicity but not saprophytic vigour. It is controlled by cytoplasmic genetic determinants, probably on, or associated with, ds RNA. All hypovirulent strains contain ds RNA which can be associated with particles like those of a virus. There is almost a continuous range of pathogenicities from avirulent to virulent among strains which contain ds RNA segments (45, 1213; 49, 861, 862; 53, 288; 55, 1481, 5360; 56, 1283, 2676; 57, 3638; 58, 1967; 59, 1889, 5385; 60, 2208, 2792; Dodds, Phytopathology 70: 1217, 1980).
Transmission: The slimy conidia are spread in water and carried long distances by birds and insects. The ascospores are air dispersed; acospore discharge has been described (59, 471).
Literature: Beattie & Diller, Journal of Forestry 52(5): 323-329, 1954; Boyce, Forest Pathology, McGraw Hill, 1961; Peace, Pathology of Trees and Shrubs, Clarendon Press, 1962; Burdekin & Phillips, Forest Record, Forestry Commission No. 111, 11 pp., 1977; Anagnostakis, Bulletin, Connecticut Agricultural Experiment Station No. 777, 9 pp., 1978.

 
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