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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Distinguished from some other root rots of woody crops by the absence of well defined rhizomorphs. The host range has been given (35: 532; 40: 90). A low temperature pathogen with an optimum in soil of 20°C or below. Diseases caused by infection from the soil have occurred in widely separated areas, e.g. on grapevine in Europe (17: 653; 25: 436), on apple in N. India (46, 3495), on strawberry in USA (33: 490); but all recent studies have been in Japan on fruit trees and tea. The fungus spreads from recently cleared forested areas to fruit (48, 2182). Woody mulches and grass covers increased spread whilst legume covers reduced it (34: 796; 45, 3299; 46, 3127). On tea the disease is most severe in spring and summer (34: 822; 35: 330). Infection of cereals has been reported and culture filtrates were phytotoxic (35: 595; 36: 65; 37: 182). Survival in soil may be for several years and infective debris should be removed in replanted areas which have a history of infection in the previous crop. Reports indicate resistance to soil fumigants but control with chloropicrin in certain soils was recently reported (50, 2749).  
Description type:Non-original description 
Description:Rosellinia necatrix Prill., Bull. Soc. mycol. Fr. 20: 34, 1904.
Conidial state: Dematophora necatrix Hartig, 1883.
Perithecia densely aggregated, globose, black, shortly pedicellate at the base, 1-2 mm diam., embedded in a ropey subiculum of brown, septate hyphae which form a thin crust on the host substratum at the base of the perithecium; hyphae of subiculum of two types; some uniform, 5-8 µm wide, and others exhibiting characteristic pyriform swellings 2-3 times the width of the hypha and formed immediately above a septum; wall 3-layered, the thicker outer layer composed of dark brown, thick-walled, rounded to polygonal cells, the middle layer of thin-walled, flattened, elongated, brown, polygonal cells and the innermost layer of cells similar to those of the outermost layer, these cells becoming gradually less coloured as they progress towards the interior; the pedicel composed of fused, intertwined filaments with thickened walls.; ostiole papillate. Asci cylindrical, long-stalked, unitunicate, 8-spored, 250-380 x 8-12 µm, with an apical apparatus blued by iodine. Ascospores monostichous, cymbiform, straight or curved, dark brown, 30-50 x 5-8 µm, with a longitudinal germ slit running parallel to the long axis of the spore for about one-third of its length. Paraphyses numerous and filiform. Conidiophores produced independently or in association with perithecia on brown ropey synnemata which project straight outwards as rigid columns. Synnemata up to 1,5 mm high. Stipe 40-300 µm wide, composed of flexuous, intertwined, repeatedly branched threads, 2-3,5 µm wide, often branched dichotomously towards the apex and splaying out to form a pale to brown head. Conidiogenous cells polyblastic and integrated and terminal on branches or discrete, sympodial, geniculate, denticulate, with short thin-walled separating cells which break across the middle leaving a minute frill at each geniculation which corresponds to a frill at the base of each conidium. Conidia solitary, acropleurogenous, simple, ellipsoid or obovoid, hyaline to pale brown, non-septate, smooth, 3-4,5 x 2-2,5 µm.
Hosts: On Acacia, almond, Annona, apple, apricot, artichoke, avocado, barley, bean, beet, Begonia, blackberry, Boemeria nivea, cherry, chestnut, Citrus, coffee, Cotoneaster, currants, Cyclamen neapolitanum, Cynara scolymus, elm, fig, Genista monosperma, jasmine, lucerne, maize, mulberry, Narcissus, oak, olive, peach, pear, peony, pepper (black), pistachio, Pittosporum crassifolium, plum, poplar, potato, quince, rose, Salix, sorghum, strawberry, tea, tulip, Vaucheria, vine, violet, walnut, wheat, Zantedeschia.
Disease: White root rot of temperate fruit crops particularly grapevine (Vitis vinifera). apple (Malus pumila) and mulberry (Morus spp.). Probably a plurivorous pathogen: it has also been reported causing disease in artichoke (Cynara scolymus; 7: 218), coffee (Coffea spp.; 36: 318), lucerne (Medicago sativa; 21: 23), mandarin (Citrus reticulata: 45, 3299), ramie (Boehmeria nivea) and tea (Camellia sinensis; 35: 330). The roots (young ones of tea being attacked first) are invested with a white mycelium which on older roots turns to brown and almost black; superficial black sclerotia may occur and the hyphae are swollen near the septa. Wilt and death of the tree may be slow or fairly rapid and infection is generally confined to the roots.
Geographical distribution: Widespread in Europe, W. Asia, central Africa and also occurs in Argentina, Brazil, Mexico, Philippines, Uruguay and USA (CMI Map 306, ed. 2, 1965). Additional records not yet mapped are: Colombia, Dominican Republic, India (Himachal Pradesh), New Zealand, UK (Scilly Is.).
Physiological specialization: None reported.
Transmission: Plant roots and debris in soil. There appears to be no evidence for spread by spores.
Literature: Berlese, Riv. Patol. veg., Padova 1: 5-17, 33-34, 1892; Butler & Jones, Plant Pathology, 1949; Hartig, Untersforstbot. Inst. Munchen 3: 122-126, 1883; Khan. Biologia Lahore 5: 199-245, 1959 (102 refs); Moore, British Parasitic Fungi, 1959; Nattrass, Rep. Long Ashton Res. Stn 1926: 66-72, 1927; Prillieux, Maladies des Plantes Agricoles: 133-144, 1897; Saccas, Agron. trop., Nogent 11: 551-595, 1956; Thomas, Wilhelm & Maclean, in Plant Diseases, USDA Yr book: 703-705, 1953; Thomas, Hansen & Thomas, Phytopathology 24: 1145, 1934; Viala, Monographie du Pourridie: 1-95, 1891; Wormald, Diseases of Fruit and Hops, 1955.

 
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