Disease of Potato By S. Sankareshwari

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.

8. http://www.ag.ndsu.edu/publications/crops/powdery-scab-of-
potatoes/pp1891.pdf

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.

14. Life Cycle
http://extension.umaine.edu/publications2436e/

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.