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Fungi - Potato

Contributors to this section: CIP, Lima, Peru (Carols Chuquillanqui, Segundo Fuentes, Ivan Manrique, Giovanna Muller, Willmer Pérez, Reinhard Simon, David Tay, Liliam Gutarra); CIP, Nairobi, Kenya (Ian Barker); FERA, UK (Derek Tomlinson, Julian Smith, David Galsworthy, James Woodhall).

Contents:
Potato scab
Wart disease of potato
Potato_smut

Potato scab

Scientific name

Streptomyces scabiei (ex Thaxter 1892) Lambert & Loria, 1989

Significance

The disease occurs in all potato growing regions throughout the world and reduces marketability of table, processing and seed potatoes (Loria et al., 1997; Wale et al., 2008)) and was ranked as the fourth most important disease in a 1991 survey of potato growers (Loria et al., 1997). S. scabiei has not been reported in Peru (CABI, 2007).

Symptoms

Foliage: No symptoms are visible.

Tubers: S. scabiei (formerly S. scabies) causes variable symptoms on the surface of potato tubers including erumpent, russet, and pitted lesions. Superficial lesions are usually circular, raised, tan to brown, cork-like in appearance and 5-10 mm in diameter, some cases are irregular in shape and larger especially when infections coalescence (Hooker, 1981). Erumpent lesions are raised lesions whereas pitted lesions are dark-colored sunken areas up to ½ in deep and crater-like (Loria et al., 1997; Hooker, 1981, Wale et al., 2008). Scab lesions can occur anywhere on the tuber surface and more than one type of lesion may be present on a single tuber. Small brown, water-soaked, circular lesions are visible on immature tubers associated with lenticels within a few weeks after infection (Lapwood, 1973). Scab affects young tubers with the lesions expanding as the tuber matures.

Hosts

Sugar beet, carrot, turnip, parsnip, rutabaga and radish, groundnut (peanut).

Geographic distribution

Asia, Europe, Africa, North America, Central America, South America, Oceania

Biology and transmission

S. scabiei survives for long periods on decaying plant parts in the soil or possibly on roots of living plants, in old feed lots, or fields heavily manured with animal wastes (Hooker, 1981). S. scabiei infects immature lenticels and gains access to older tissue through wounds and natural openings (Hooker, 1981; Wale et al., 2008; CABI, 2007). Once S. scabiei has entered the host, it grows both between and through cells and incites multiple cork layer formation, which results in the scabby appearance of the lesions. Common scab does not spread in storage. Micropropagated plants have not been reported to transport S. scabiei propagules (CABI, 2007).

Detection/indexing method in place at CIP

Treatment/control

Procedure followed at the centers in case of positive test

If pathogen is detected and cannot be erradicated, the germplasm must be destroyed. If the germplasm is scarce or unique, maintain it separately under containment so as not to present a risk to other germplasm.

References of protocols at EPPO, NAPPO or other similar organization

NAPPO. 2003. Regional standard for Phytosanitary Measures (RSPM) No.3. Requirements for importation of potatoes into a NAPPO member country. 53 pp.

References and further reading

CABI. 2007. Crop Protection Compendium [online] Available from URL: www.cabi.org/compendia/cpc/ Commonwealth Agricultural Bureau International (CABI), Wallingford, UK. Date accessed 07 May 2010

Hooker WJ. 1981. Compendium of potato diseases. St. Paul, Minn., USA: American Phytopathological Society.

Loria R. Bukhalid RA, Fry BA, King RR. 1997. Plant pathogenicity in the genus Streptomyces. Plant Disease, 81(8):836-846.

Lapwood DH, Wellings LW, Hawkins JH.1973. Irrigation as a practical means to control potato common scab (Streptomyces scabies): final experiment and conclusions. Plant Pathology, 22(1):35-41.

Schaad NW. (ed.). 1988. Laboratory guide for identification of plant pathogenic bacteria. The American Phytopathological Society.St. Paul (USA). 2nd. ed. pp114-127.

Wale S, Platt HW (Bud), Cattlin N. 2008. Diseases, Pests and Disorders of Potatoes. A color Handbook.Manson Publishing, London, UK.176 pp.

Seed Health General Publication Published by the Center or CGIAR

Jeffries C. 1998. FAO/IPGRI Technical guidelines for the safe movement of Germplasm. No. 19. Potato. Food and Agriculture Organization of the United Nations, Rome/International Plant Genetic Resources Institute, Rome.

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Wart disease of potato

Scientific name

Synchytrium endobioticum (Schilb.) Percival

Significance

S. endobioticum is on the A2 quarantine list of EPPO.

Symptoms

Aerial symptoms: Ocasionally warts can be found on stems, leaves and flowers during severe attacks (Noble et al., 1970; Hampson, 1981 and Torres, 2002). Subterranean symptoms may cause a reduction in vigor of plants.

Subterranean symptoms: Below ground galls
Galls vary in shape but are mostly spherical, with corrugated surfaces, and range from pea-size to fist-size (<1 cm to >8 cm diam.). Below ground galls are white to brown, turning black as they decay. These galls appear at stem bases, stolon tips and tuber eyes. They may not be evident until harvest-time (Wale et al., 2008). At harvest, galls may desiccate or decay. Tubers may be disfigured or completely replaced by galls (Torres, 2002). Tuber galls may develop after harvest, in storage. The host potato may not be killed but the meristematic tissue of sprouts may be so severely attacked that plants may fail to emerge from seed tubers. S. endobioticum does not attack the roots of potato but it does attack the roots of other hosts (e.g., tomato).

Hosts

Solanum tuberosum (potato) and Solanum (nightshade)

Geographic distribution

Asia, Europe, Africa, North America, South America, Oceania

Biology and transmission

S. endobioticum has a very limited means of spread and dispersal. Spread in soil by zoospores is limited (50 mm or less) to the infection zones of the plant. Soil water can carry zoospores downstream, although the lifespan of a released zoospore is 1-2 hours (Hooker, 1981; Harrison et al., 1997). Earthworms can move resting spores short distances (Hampson and Coombes, 1989. Wind is an active dispersal agent in regions of strong dry summer winds. Local dispersal has been shown in resting spores in soil attached to vehicles and contaminated manure. Long-range dispersal by tuber movement, especially in international trade, attached soil and plants present problems of control. Machinery, sacks, crates and boots should be sanitized to avoid the spread of pathogen inoculum (cysts) (Harrison et al., 1997). In some locations, potato tubers are only susceptible to infection by S. subterranea f.sp. subterranea during lenticel formation and proliferation; thus, apparently healthy seed tubers could carry low levels of latent infection without any obvious symptoms that would reject them as seed. This could result in long distance shipment of the pathogen; thereby introducing the disease to new potato-growing areas (Hampson, et al., 1996).Control through statutory methods has been largely successful due to the fungus’ self-limited means of dispersal. The disease is essentially social, dependant on commercial crop and soil movement. Seedlings and micropropagated plants are not liable to carry propagules in trade and transport (CABI, 2007).

Detection/indexing method in place at CIP

Treatment/control

Procedure followed at the centers in case of positive test

References of protocols at EPPO, NAPPO or other similar organization

CABI/EPPO, 1998. Synchytrium endobioticum. Distribution Maps of Quarantine Pests for Europe No. 243. Wallingford, UK, CAB International.

OEPP/EPPO. 1954-1968. Potato wart disease in Europe. EPPO Publications Series B Nos 8, 48, 52, 63, 65.

OEPP/EPPO. 1977. First report of the working party on potato wart disease. EPPO Publications Series C No. 50.

OEPP/EPPO. 1982. Data sheets on quarantine organisms No. 82, Synchytrium endobioticum. Bulletin OEPP/EPPO Bulletin, 12:1.

OEPP/EPPO. 1983. Second meeting of the EPPO panel on potato wart disease. EPPO Document No. 5205.

OEPP/EPPO. 1990. Specific quarantine requirements. EPPO Technical Documents, No. 1008. Paris, France: EPPO.

References and further reading

CABI. 2007. Crop Protection Compendium [online] Available from URL: www.cabi.org/compendia/cpc/ Commonwealth Agricultural Bureau International (CABI), Wallingford, UK. Date accessed 07 May 2010

Hampson MC, Coombes JW.1989. Pathogenesis of Synchytrium endobioticum VII. Earthworms as vectors of wart disease of potato. Plant and Soil, 116(2):147-150

Hampson MC, Wood SL, Coombes JW.1996. Detection of resting spores of Synchytrium endobioticum in soil from vehicles at Port-aux-Basques, Newfoundland. Canadian Journal of Plant Pathology, 18(1):59-63.

Hooker WJ. 1981. Compendium of potato diseases. St. Paul, Minn., USA: American Phytopathological Society.

Noble M, Glynne MD. 1970. Wart disease of potatoes. FAO Plant Protection Bulletin, 18:125-135.

Torres H. 2002. Manual de las enfermedades más importantes de la papa en el Peru. Centro Internacional de la Papa, Lima, Perú. 59 pp.

Wale S, Platt HW (Bud), Cattlin N. 2008. Diseases, Pests and Disorders of Potatoes. A color Handbook.Manson Publishing, London, UK.176 pp.

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Potato smut

Scientific name

Thecaphora solani (Thirum & M.J. O’Brien) Mordue

Significance

EPPO lists T. solani as an A1 quarantine pest (OEPP/EPPO, 1979).

Symptoms

No symptoms are visible above ground. Infected tubers are misshapen, or have warty swellings on the surface, and are hard. The whole or part of the tuber may be infected. Numerous brown-black specks, interspersed with lighter brown specks, occur in the flesh (Mordue, 1988). The specks (spore sori) are about 1 mm diameter and are filled with rusty brown spore balls (Bazan, 1960; . Infected tubers later become a dry brown powdery mass containing numerous spores (O’Brien and Thirumalachar, 1972). Galls resembling deformed tubers develop on the stems or stolons underground (Torres, 2002; Wale et al., 2008).

Hosts

Solanum tuberosum (potato), Solanum (nightshade), Datura stramonium (jimsonweed), Lycopersicum (Wale et al., 2008)

Geographic distribution

North America, Central America and South America

Biology and transmission

T. solani survives in soil or in tuber debris. Infection starts a few days after planting, especially in young sprouts, underground stems, stolons or eventually in tubers (Zachmann and Baumann, 1975).The infection is generally stimulated by high humidity in the soil during the first stages of growth (Hooker, 1981; Wale et al., 2008). Seedlings and micropropagated plants are not liable to carry propagules in trade and transport (CABI, 2007).

Detection/indexing method in place at CIP

Treatment/control

Procedure followed at the centers in case of positive test

References of protocols at EPPO, NAPPO or other similar organization

EPPO, 2006. PQR database (version 4.5). Paris, France: European and Mediterranean Plant Protection Organization. [online] Available from URL: www.eppo.org/ Date accessed 07 May 2010

OEPP/EPPO. 1979. Data sheets on quarantine organisms. No. 4, Angiosorus solani. Bulletin OEPP/EPPO Bulletin, 9(2).

References and further reading

Bazan de Segura C. 1960. The gangrena disease of potato in Peru. Plant Disease Reporter, 44:257.

Hooker WJ. 1981. Compendium of potato diseases. St. Paul, Minn., USA: American Phytopathological Society.

Mordue JEM. 1988. Thecaphora solani. CMI Descriptions of Pathogenic Fungi and Bacteria, No. 966. Wallingford, UK: CAB International.

O’Brien MJ, Thirumalachar MJ. 1972. The identity of the potato smut. Sydowia, 26(1/6):199-203.

Torres H. 2002. Manual de las enfermedades más importantes de la papa en el Peru. Centro Internacional de la Papa, Lima, Perú. 59 pp.

Wale S, Platt HW (Bud), Cattlin N. 2008. Diseases, Pests and Disorders of Potatoes. A color Handbook.Manson Publishing, London, UK.176 pp.

Zachmann R, Baumann D.1975. Thecaphora solani on potatoes in Peru: present distribution and varietal resistance. Plant Disease Reporter, 59(11):928-931.

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The Genebanks

The 11 CGIAR genebanks currently conserve 730,000 of cereals and grain legumes, forage crops, tree species, root and tuber crops, bananas and crop wild relatives.

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