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Powdery scab of potato
- 1. POWDERY SCAB OF POTATO COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po),ViaVaigai Dam, Theni-625 562 STUDENT Miss. SANKARESHWARI.S ID. No: 2015021115 COURSE TEACHER Dr. PARTHASARATHY S Asst. Professor (Plant Pathology)
- 2. Powdery Scab of Potato • Spongospora subterranea f.sp. subterranea (Wallr.) Lagerheim (1892)
- 3. History • In 1842, Wallroth described the symptoms for the first time in the scientific literature in Germany. • He called it as Erysibe subterranea. • In 1887, Brunchhorst named the pathogen Spongospora solani. • In 1892, Lagerheim proposed the name Spongospora subterranea Wallr.
- 4. Occurrence • It was first discovered in Germany in 1842. • It was found in Norway and England in 1846 and in U.S.A. in 1913. • It occurs in cooler areas of Australia, Tasmania, New Zealand and Kenya. • Its occurrence in India is restricted to higher hills of Himachal Pradesh, Darjeeling and Nilgiris in south.
- 5. Economic Significance • It is the second most important disease incited by a member of class Plasmodiophoromycetes. • Economically significant soil-borne plant pathogen which is also important as a vector of a virus, the potato mop-top furovirus. • They reduces the proportion of marketable production and carry infections to subsequent crops when used as seeds.
- 6. Host Plants • Underground parts of Tomato. • Other species of Solanum including S. nigrum and S. curtilobum. • Carrot, Cabbage, Celery, Beans and Peas, Onion, Kikiyu, Cucumber, Maize and Solanaceous weeds.
- 7. Symptoms •Attacks roots, stems, stolons and tubers. •Young tubers- Purplish-brown lesions that later develop into small blisters occurring as early as 43 DAP. •Mature symptoms- Round, slightly raised usually shallow lesions which shows raised margins. •Root galls are creamy white and turns dark brown when they mature.
- 9. Taxonomic classification Phylum: Cercozoa Class: Phytomyxea Order: Plasmodiophorales Family: Plasmodiophoraceae Genus: Spongospora Species: Spongospora subterranea
- 10. Pathogen • Obligate pathogen. • Forms zoospores that swim in free water which penetrate the root hairs. • They are uninucleate and on increase in size becomes multinucleate Plasmodium. •Forms spore balls that can survive in the soil for long periods of time. •Vector of the mop-top virus.
- 11. PATHOGEN ON ROOT HAIRS http://www.researchgate.net http://people.ohio.edu
- 12. Mode of Spread Primary spread : Spore ball present in the soil. Secondary spread : Zoospores released from the resting spore.
- 13. Favourable conditions •Free water is a prequisite for zoospores to cause infection. •Cool conditions: ±12 – 17ºC are optimal for the infection of tubers. •Spore ball germination- 10ºC.
- 15. Management • Selection of healthy seed tubers. • Avoid contaminated fields and excessive Nitrogen. •Treatment of tubers with organomercurial fungicides. •Use resistant varieties- S. tuberosum (CP 1742, 8-7), S. tuberosum × S. andigena (66-528/8, 66-587/4, 66- 619/4, 66-669/1), S. tuberosum × S. microdontum (BRB/A-24) and a polyploid of S. tuberosum (JHT/A- 1214). •Resistant exotic varieties- Panther, Patron and Red Skin.