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Remarks (public):For a complete description including images see 
Remarks (internal):Berkeley & Broome (1850) found the fungus on peas and on Nemophila auriculata in England; they observed the chlamydospores and named the fungus Torula basicola. Zopf (Sitzb. bot. Prov. Brandenburg 18: 101-105, 1876) observed a fungus on Senecio elegans producing chlamydospores similar to those of Torula basicola; he also saw endoconidia and cleistothecia and, assuming a connection, named the fungus Thielavia basicola (Berk. & Broome) Zopf. It is now known that Thielavia basicola grows only in association with Thielaviopsis basicola which is a distinct fungus (McCormick, Bull. Conn. agric. Exp. Stn 269, 1925). Thielavia basicola occurs in and on tobacco roots only if they are infected with Thielaviopsis basicola (see Stover, Can. J. Res. C 28: 445-470, 1950). In the case of tobacco, blackening and decay of the root system and some stunting are major symptoms, the plants being killed in severe cases. The cortex and periderm of roots are invaded, entry being through ruptures in the cortex due to the emergence of secondary root primordia. Leaves of diseased plants have a lower nicotine content (42: 705). Soil factors favouring the development of the disease are: temperature of 17-23ºC, soil pH of about 5,7-5,9, a high soil moisture and inadequate aeration. Resistance has been explained as due to cork formation as a barrier to the invading fungus in resistant varieties; in susceptible varieties such corking apparently occurs only at higher temperatures, on the other hand, it is also thought that resistance may not be structural but chemical. In the presence of toxins, the disease is equally destructive to roots of resistant and susceptible varieties (42: 505, 528,704). Resistant varieties offer the best method of control. In tobacco, several have been developed in the U.S., e.g. Burley (Kentucky 16 and 41A and Burley 1), Flue-cured (400 and Yellow Special), Cigar (Havana 142, 211, 307, Kl and K2) (see Hopkins, 1956, pp. 99-102). Nicotiana rustica (24 varieties) is immune (34: 678).
Description type:Non-original description 
Description:Thielaviopsis basicola (Berk. & Broome) Ferraris, Flora ital. Crypt., I. Fungi. Hyphales, fasc. 8, pp. 233-34 cum icon., 1912.
= Torula basicola Berk. & Broome, Ann. Mag. nat. Hist. 2: 461, 1850.
= Milowia nivea Massee, 1884.
Colonies dematiaceous and producing two types of non-septate conidia: macroconidia (chlamydospores) which are brown, subrectangular, somewhat rounded at the tips, produced from hyaline basal cells in short chains 14-16 µm long, breaking apart at maturity and then blackish; microconidia (endoconidia) produced within 'endoconidiophores', cylindrical, abstricted in a linear series from an endogenous mother cell, catenulate, subhyaline, truncate at the ends, 6 x 4 µm, liberated through the apex in succession.
Hosts: On a wide host range attacking plants in over fifteen families, primarily belonging to the Leguminosae (groundnut, soybean, Lespedeza, clover, alfalfa, cowpea, lupin, sunn hemp, bean), Solanaceae (tobacco) and Cucurbitaceae; also from Citrus roots.
Diseases: Causes black root rot in tobacco and many other crops (see above). Recent reports suggest that it may be a serious pathogen on Citrus roots (39: 411; 42: 263, 761). Many species of Nicotiana are susceptible and some are considered resistant or immune (Johnson, 1916, J. agric. Res. 7: 289-300; 50: 248).
Geographical distribution: Africa (S. Africa, Egypt), Asia (Persia, Japan, India, Indonesia); Australasia (Australia, N. Zealand), Europe (Bulgaria, France, Germany, Italy, Netherlands, Norway, Poland, Rumania, Switzerland, U.S.S.R., Yugoslavia), N., C. and S. America.
Physiological specialization: Strains are known differing in cultural characters and pathogenicity: Stover (Can. J. Res. C 28: 445-470, 1950) found two types, one brown and the other grey the latter being the less pathogenic.
Transmission: Soil-borne; the pathogen is a soil inhabitant capable of prolonged saprophytic survival in soils.
Literature: Hopkins, Tobacco Diseases, 1956; Wolf, Tobacco diseases and decays, 2nd edition, 1957; Lucas, Diseases of tobacco, 1958.

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