EUROPEAN A N D MEDITERRANEAN PLANT PROTECTION ORGANIZATION

DATA SHEETS ON QUARANTINE ORGANISMS

EPPO LIST A1

Angiosorus solani Thirumulachar & O’Brien

Basidiomycetes : Usti lag inales

Synonym

Tbecapbora solani Barrus

Common Names

Potato smut

Principal Hosts

Tuber-bearing Solanum spp. S. tuberoszcm S. stoloniferum S. tuberosum subsp. andigena

potato

Geographical Distribution

Central and South America : Mexico, Panama, Bolivia, Colombia, Ecuador, Peru and Venezuela only.

Biology

The fungus apparently survives in soil or in tuber debris (91, but it is not known how long it can persist. Incidence is increased in the absence of crop rotation and is favoured by high humidity and saline soils. Field observations (3) indicate that seed tubers transmit the disease.

Economic importance

The disease is reported to be serious. Losses of up to 80 % have been known in the very susceptible variety Peruanita (3). Susceptibility to infection varies, some varieties being resistant.

Potential within EPPO Region

The possible effect of the disease cannot be assessed as there is so little published information on the biology and life history of the causal organism. Being soilborne, it would presumably be virtually impossible to eradicate once established. Varietal resistance would seem, however, to offer the possibility of control. The evidence of climatic influence on the disease is confusing, as it is reported from the Andean region (not below 3,000 m) in Venezuela (latitude 9” N) ( 9 ) and from the mountains and

at near sea level in Peru (latitude 18" S) (3) the fungus would have potential to thrive from the Mediterranean to the North.

Means of Entry

The most likely way in which potato smut could enter Europe would be with tubers. It has been intercepted by the U.S. Dept Agric. in 52 consignments of tubers of S. tuberosum and S. stolonifsrum, almost all from Mexico, since 1946 (USDA Lists of Intercepted Plant Pests). Soil from infected areas could also introduce the fungus.

Identification (5, 7, 9)

Symptoms Infected tubers are mis-shapen, or have warty swellings on the surface, and are hard. The whole or part of the cuber may be infected. Numerous brown-black specks, interspersed with lighter brown specks, occur in the flesh. The specks (spore sori) are about 1 mm in diameter and are filled with rusty brown spore balls. Infected tubers later become a dry brown powdery mass containing numerous spores.

Confirmation Spore balls: when mature, are 2-8 spored (the spores are rarely solitary), cinnamon to rust brown, 15-50 X 12-40 pm in diameter (10). Spores ; are pressed together but can be teased apart ; subglobose to angular, smooth on the contiguous side and densely verrucose on the free side, 7.5-20 X 8-18 pm.

Relevant Inspections

Although malformed tubers are conspicuous, consignments from areas in which the disease occurs could carry infection at undetectable levels or as spores on the surface of healthy tubers. Inspections, therefore, cannot be fully reliable, and introduction of tubers from such areas has a certain risk.

This may indicate that, in Europe,

Key References

1.

2.

3.

4. 5.

6.

7. 8.

9.

10.

ABBOTT, E.V. (1928). RBna de la papa. I n : <( La RBna )) y la <( Raucha )) o <( Hielo )) de la papa. Estac. exper. Agric. SOC. nacional Agrar. (Peru) Circ. 7, 11 pp. - (1931). Enfermedades de las plantas cultivadas en el Peru. Estac. exper. Agric. Molina (Peru) Circ. 18, 20 pp. - (1932). La RBna. I n Enfermedades de las plantas cultivadas en el Peru. Estac. exper. Agric. Molina (Peru) Circ. 18 : 20-21. BARRUS, M.F. (1944). A Thecaphora smut on potatoes. Phytopathology 34 : 712-714. BARRUS, M.F. & A.S. MULLER (1943). An Andean disease of potato tubers. Phytopathology 33 : 1086-1089. BAZAN de SEGURA, C. (1960). The gangrena disease of potato in Peru. PI. Dis. Reptr 44 : 257. COMMONWEALTH MYCOLOGICAL INSTITUTE (1967). Distrib. Maps PI. Dis. No. 214. FERNOW, K.M. & O.C. GARCES (1949). Produccion de sernilla certificada de papa. Rev. Fac. nacional Agron. Medellin 1Q : 257-295. O'BRIEN, J. & M.J. THIRUMULACHAR (1974). The identity of the potato smut. Sydowia 26 :

ZACHMANN, R. & D. BAUMANN (1975). Thecaphora solani on potatoes in Peru : present distribution and varietal resistance. PI. Dis. Reptr 59 (11) : 928-931.

199-203.

September 1977 PARIS

1, rue Le NBtre

Photos: Courtesy R. Zachmann, CIP. Peru.

External view of potato tubers infected by Angiosoros solani, showing deformities and warty swellings.

m s C .-

0 u u n L

c 0 a

Cross

section of potato tuber infected

by A

ngiosorus solani,

showing the

individual spore containing cavities.