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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):For earlier references see IMI Description sheet No. 212. The influence of soil type, and inoculum density on wilt has been investigated (51, 1030). Control is primarily by use of resistant host cultivars (49, 320; 56, 5309). Early cultivars of sweet potato grown in USA were very susceptible to wilt, but breeders now routinely screen cultivars for wilt susceptibility and a so range with good resistance is available in Brazil (64, 2886), China (69, 7612; 69, 6822), Japan (59, 3988; 69, 5418; Suzuki, 1989; Tarumoto et al., 1989) and USA (55, 504; Paterson et al., 1984; Hamilton et al., 1985; Pope et al., 1985; Collins & Moyer, 1987a, 1987b; Rolston et al., 1987; Sterrett, et al., 1987; Paterson et al., 1988; Hall & Harmon, 1989). An Ipomoea carnea rootstock with good wilt resistance was described by Dukes et al. (1990). Treatment of planting material with benomyl or thiabendazole may reduce transmission (56, 3376). Cross-protection using non-pathogenic strains of F. oxysporum has been demonstrated (63, 5261; 65, 1037; 66, 816; 69, 5418). VA mycorrhizal infection, temperature, and soil phosphorus levels may influence wilt incidence (64, 1924).
 
Description type:Non-original description 
Description:Fusarium oxysporum Schlecht. f.sp. batatas (Wollenw.) Snyder & H.N. Hansen, Amer. J. Bot. 27: 66, 1940.
Fusarium batatas Wollenw., J. agric. Res. 2: 268, 1914.
Fusarium bulbigenum var. batatas Wollenw., Z. ParasitKde 3: 414, 1931.
Teleomorph: None known.
The fungus causes a vascular wilt of sweet potato. It does not infect intact roots but enters via root wounds and then spreads in the xylem tissues (56, 509). Dark brown vascular discolouration extends up the stem from the roots. This may be purplish in underground tissues. Leaves turn yellow and wilt, eventually falling. In heavily infected plants, the fungus may spread from the xylem and cause cortical necrosis, killing the plant. The fungus may then sporulate from the nectrotic tissues. In other cases, the plants have stunted growth but survive to produce tubers. If storage roots from such plants are used for propagation, the disease will reoccur in the young plants. Infected tubers may rot in storage. When grown in culture the fungus is morphologically indistinguishable from strains of F. oxysporum causing surface rot of tubers or from saprobic strains inhabiting the soil. Strains of F. solani (Martius) Sacc., sometimes referred to as F. solani f.sp. batatas McClure, may also cause surface rot but are not capable of causing vascular wilt.
Hosts: Ipomoea batatas (sweet potato), Nicotiana (tobacco). The fungus may infect a wide range of other plants in Convolvulaceae (63, 1065) and other families, sometimes without causing wilt symptoms.
Disease: Vascular wilt, sometimes called stem rot.
Geographical distribution: Brazil (62, 525), China, Hawaii, India, Japan, Malawi, New Zealand. The disease
occurs in temperate rather than tropical regions.
Physiological specialization: Two races are distinguished within f.sp. batatas. Race 1 causes wilt of Burley tobacco, race 2 attacks both Burley and flue-cured tobacco.
Transmission: The fungus may survive in soil for many years as chlamydospores. Transmission may occur by means of infected plant material used for propagation, or through contaminated soil.
Literature: Collins, W.W. & Moyer, J.W. (1987a) HortScience 22: 679. Collins, W.W. & Moyer, J.W. (1987b) HortScience 22: 514-515. Dukes, P.D., Jones, A. & Schalk, J.M. (1990) HortScience 25: 238-239. Hall, M.R. & Harmon, S.A. (1989) HortScience 24: 176-177. Hamilton, M.G., Dukes, P.D., Jones, A. & Schalk, J.M. (1985) HortScience 20: 954-955. Jones, A., Dukes, P.D., Schalk, J.M., Hamilton, M.G., Mullen, M.A., Baumgardner, R.A., Paterson, D.R. & Boswell, T.E. (1985) HortScience 20: 781-782. Paterson, D.R., Earhart, D.R. & Boswell,
T.E. (1988) HortScience 23: 414. Paterson, D.R., Fuqua, M.C., Earhart, D.R. & Motes, J.E. (1984) HortScience
19: 455. Pope, D.T., Collins, W.W., Moyer, J.W. & Turner, J.L. (1985) HortScience 20: 145. Rolston, L.H., Clark, C.A., Cannon, J.M., Randle, W.M., Riley, E.G., Wilson, P.W. & Robbins, M.L. (1987) HortScience 22: 1338- 1339. Sterrett, S.B., Graves, B., Savage, C.P., Jr. & Cooler, F.W. (1987) HortScience 22: 332-333. Suzuki, M. (1989) Japanese Journal of Breeding 39: 499-506. Tarumoto, I., Shiga, T., Sakamoto, S., Ishikawa, H., Kato, S., Takemata, T. & Umehara, M. (1989) Bulletin of the National Agriculture Research Center, Japan 15: 15-29.


 
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