symptoms,pathogen and management

1. BLACK SHANK OF TOBACCO
STUDENT COURSE TEACHER
MODHANA. V Dr. Parthasarathy. S
2016021021 Asst.Prof., (Plant Pathology)

2. Disease name: Black Shank of Tobacco
Pathogen name: Phytophthora nicotianae Breda de Haan
Hosts: Tobacco: Nicotiana tabacum and Nicotiana rustica

3. Systematic position
Kingdom: Chromista
Phylum: Heterokontophyta
Class: Oomycota
Order: Peronosporales
Family:Peronosporales
Genus: Phytophthora
Species: P. nicotianae

4. Significance
 Black shank is among the most destructive and
widespread of all tobacco diseases in North Carolina
 It is a devastating root rot disease caused by the
oomycete pathogen

5. HISTORY
 Black shank first appeared in the United States in
1915.
 It was first repored in North Carolina in Forsyth
country.

6. Distribution
In world
 USA, Dutch East Indies and Puerto Rico .
In India
 All the tobacco growing states
 Andhra Pradesh
 Tamil Nadu
 Gujarat and UP.

7. SYMPTOMS
 Black shank can affect any part of the tobacco plant at
any growth stage.
 Root and crown rot are the most common symptoms.
 It causes rapid yellowing, wilting of leaves and
eventually plant death.

8.  Leaf spots appear and form circular, yellowish-to-
brown lesions upto 3 inches in diameter with
concentric rings.
 A dark brown to black lesion often appears on the
stalk.
 When cut open, the lower stem and crown often show
blacken pith with distinct disk and white hyphae.
 The chlorophyll content of the infected plants will
reduced

9.  In leaves and causes blighting and drying of the
bottom leaves.
 A longitudinal cut through the stem reveals necrotic
pith that is often separated into disks
 Infected roots are initially water-soaked, lesion then
rapidly become necrotic spreads to stem causing
black shank

10. Leaf spots caused by P. nicotianae
content. ces . ncsu. edu

11. Stem infection caused by P. nicotianae
crosscreekseed. com

12. Plant affected by Black shank
tobacco-diseases. info

13. Field affected by Black shank
knowmoregrow. com

14. Pathogen Characters
 Hyphae:
 It is colourless and transparent.
 They lack internal partitions, or septa.
 Hyphae are also coenocytic.
 It has numerous hyphal swelling, and highly
branched.
 Mycelium:
It is intercellular, branched, coenocytic, hyaline
and non-septate.

15. Hyphae
en. wikipedia. org

16. ASEXUAL REPRODUCTION
P.nicotianae primarily reproduces asexually through
the formation of several types of structures.
 Chlamydospores:
• It is asexual, thick-walled spores produced at the
tips or in the middle of hyphae.
• It serve as the primary survival propagule and as
the primary inoculum that initiates epidemics.
• Survival for 4 to 6 years in soil has been reported.

17.  Zoospores:
• It is typically kidney –shaped, with a ventral.
• Groove from which two flagella emerge.
• The posterior flagellum is whip-like and the anterior
flagellum a tinsel type, is shorter with hairs along its
length.
• Zoospores emerge from sporangia and swim through
soil water.
• It encyst and a single germ tube emerges from the
spores.

18.  Sporangia:
• It can be ovoid, pear-shaped, or spherical.
• It have very prominent tips called papillae.
• Sporangia may sometimes directly produce hyphae,
but more often form zoospores.
• The number of zoospores produced by a single
sporangium is typically 5-30.

19. Chlamydospores Zoospores
en. wikipedia. org

20. Sporangia
en. wikipedia. org

21. SEXUAL REPRODUCTION
 Oospores:
• It are thick-walled .
• The oospore germinates by producing a germ tube.
• It serve as a primary survival propagule or initiate
infections that lead to epidemic development.

22. Oospores
en. wikipedia. org

23. Life cycle of P. nicotianae
en. wikipedia. org

24. MODE OF SPREAD
PRIMARY SPREAD:
 It is a soil borne disease.
 The fungi survives on plant residues in soil.
 The primary infection takes place in optimum
weather conditions by means of soil -inoculum .

25. SECONDARY SPREAD:
 The spread of diseases takes place by means of
zoospores which are disseminated by wind, water and
other suitable agencies .

26. FAVOURABLE CONDITION
 The organisms can grow vegetatively at temperatures
between 5°C and 37°C.
 Extended exposure to temperature above 40°C Is
lethal to the organism.
 Disease is favoured by Ph value is greater than 6.2.

27. Management
Cultural pratices
 It includes raising the beds, crop rotation and by
doing stalk and root destruction. Co
 Cover the seed beds with paddy husk or groundnut
shell at 15-20 cm thick layer and burn.
 Select health, disease free seedlings for transplanting.

28. Chemical control:
 The use of soil fumigants such as chloropicrin may
reduce pathogen populations.
 Application of fumigant nematicide such as 1,3-
dichloropropene reduce nematode populations that
enhance black shank incidence and severity.

29.  Provide adequate drainage in the nursery. Drench the
nursery beds with 1% Bordeaux mixture or 0.2%
Copper oxychloride, two days before sowing.
 Spray the beds two weeks after sowing with 0.2 per
cent Metalaxyl or 0.2 per cent Copper oxychloride or
1 per cent Boreaux mixture and repeat after 10 days.

30. REFERENCE
• Singh,R.S.,2018.Plant Diseases.Tenth
Edition.Scientific International(Pvt)Ltd.
New Delhi.
• Sushil Kumar Singh.,Dinesh Kumar and Adesh
Kumar.2015.Plant Diseases And Their
Management.Kalyani Publisher.
New Delhi.