symptoms,management and pathogen

1. STUDENT NAME COURSE TEACHER
RAMYA.V Dr. S. PARTHASARATHY
ID. No. 2016021037 Assistant Professor (Plant Pathology).
COLLEGE OF AGRICULTURAL TECHNOLOGY
Affiliated to Tamil Nadu Agricultural University, Coimbatore
Kullapuram, Via Vaigai dam, Theni-625 562
ROOT ROT AND POWDERY MILDEW OF
SUNFLOWER

3. ROOT ROT
SIGNIFICANCE
• It is also called as charcoal rot.
• It has wide host range responsible for loses on
more than 500 cultivated and wild plant species.
• In Pakistan, it has been reported to cause disease
on 67 economic host including pulses, field
crops, flowers and vegetables.
• It is soil, seed and stubble borne fungal
pathogen.

4. • 24 sunflower genotypes were analyzed under
charcoal rot stress conditions.
• Loses are often associated with hot and drought
conditions.
• It attacks 400 plant such as soybean ,edible beans,
corn and sorghum.

5. ECONOMIC LOSSES
• This disease cause yield reduction, decrease of weight
of 1000 seeds, decrease of the protein content in
seeds and changes in the fatty acid content of the seed
oil.
• Yield reduction upto 50%.

6. DISTRIBUTION
• WORLD: Warmer region of Europe, Sahiwal,
Slovakia.
• In the former, USSR, the charcoal rot was registered
in Russia(Northern Caucasus, Central Black Soil
Zone), Ukraine and Moldova.
• INDIA: Punjab and Sindh.

7. SYMPTOMS
• The pathogen attacks the root and stem of the
growing plant causing sudden wilting of the plant.
• Early symptom is not visible on infected plants, but
the plant becomes weak, mature early and when dry
show a presence of black ashy discolouration of the
plant.
• This pathogen primarily causes seedling blight and
collar rot in initial stages.
• The infected plants show drooping of leaves and
death occurs in patches.

8. • The bark of the lower stem and root shreds and
associated with large number of sclerotia.
• Dark coloured minute picnidia also develop on the
lower portion of the stem.

9. ROOT ROT OF SUNFLOWER
© www.eagri.org

10. Kingdom Fungi
Phylum Ascomycota
class Incertae sedis
order Incertae sedis
Family Incertae sedis
Genus Macrophomina
Species M.phaseolina
SYSTEMIC POSITION

11. PATHOGEN -CHARACTERS
• It was caused by fungal pathogen
Macrophomina phaseolina .
• This pathogen develop only during anamorphous stage
in its life cycle.
• The morphological structures of the pathogen are
vegetative mycelium and sclerotia.
• It also has a stage of sterile mycelium (Rhizactonia
bataticola)
• In the central cylinder of the affected tissue numerous
black small sclerotia are formed.
• The slerotia size varies from 50-200 mkm.

12. • The pycnidia are dark brown to black with an ostiole
and contain numerous single celled thin walled,
hyaline and elliptical pycnidiospores.
• Microsclerotia are black, smooth and round to oblong
in shape, uniformly reticulate, formed from hyphal
aggregates.
• Pycnidia are immersed in host tissue and erumpent
when mature.

13. • They are dark to greyish, globose and truncate
ostiole.
• Pycnidiospores are hyaline and single celled,
ellipsoidal or ovoid, with a length-width ratio of 3:1.

14. MYCELIUM CHARACTERS
• Hyphal branches are formed in a right angle and may
form a cross wall at the constriction point.

15. PYCNIDIUM OF ROOT ROT
© www.biologydiscussion.com

16. MYCELIUM OF Macrophomina phaseolina
© www.alchetron.com

17. DISEASE CYCLE
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18. EPIDEMOLOGY
MODE OF SPREAD
Primary spread
• The pathogen is seed- borne and it serves as primary
source of infection.
• m the infected heads land on the
later emerging florets and infect
the frequent rain showers, high humidity
and temperature. The disease is internally seed borne,
where pathogen infects the embryo in the seed.

19. Secondary spread
• Wind- borne conidia cause secondary spread.
• The soil borne sclerotia also spreads through rain
splash , irrigation water and implements.

20. FAVOURABLE CONDITIONS
• Charcoal rot thrives in the hottest, driest part of the
growing season.
• Moisture stress and higher temperature favour
development of the disease.

21. MANAGEMENT
• Closer planting of the seedling should be avoided.
• Optimum nutrition should be provided to maintain
the plant vigour.
• Whenever the soil becomes dry and the soil
temperature rises then irrigation should be provided.
• Seed treatment with Trichoderma viride formulation
at 4g/kg seed.
• In endemic areas long crop rotation should be
followed.
• Treat the seeds with carbendazim or thiram at 2/kg.
• Spot drench with carbendazim at 500mg/litre.

22. POWDERY MILDEW
SIGNIFICANCE
• This disease is caused by Erysiphe cichoracearum .
• This disease responsible for economic losses in
number of crops.
• This disease has a limited range of host species.
• This incidence of this disease is more severe in
closely planted crops.
• It is common in both irrigated and non irrigated
conditions.
• The most susceptible cultivar is Mega 363.

23. ECONOMIC LOSS:
• Severity of disease leads to potential decrease in seed
yield to an extract of 13 per cent.
• Yield reduction is characterized by the reduction in
photosynthetic activity and physiological changes.
• Disease causing considerable yield loss proportional
to the disease severity and the stage at which it
occurs.

24. DISTRIBUTION
• World: Pakistan, Romania, Serbia, USSR.
• India: Bombay, Rajasthan, West bengal, Punjab.

25. SYMPTOMS
• The first symptom are tiny, white superficial spots on
leaves and stems which become powdery as they
enlarge.
• White powdery growth appears on the upper surface
of the leaves and later on they enlarge, coalesce and
cover the leaves.
• Occassionaly, the symptoms appear on stems and
bracts.
• Severe infection may lead to premature defoliation of
the plant.
• The fruits remain undersized.

26. POWDERY MILDEW OF SUNFLOWER
©www.pnwhandbooks.org

27. SYSTEMIC POSITION
Kingdom Fungi
Phylum Ascomycota
Class leotiomycetes
Order Erysiphales
Family Erysiphaceae
Genus Erysiphe
Species cichoracearum

28. PATHOGEN -CHARACTERS
• The fungus, reported to overwinter as chasmothecia
on plant residue.
• Conidia in long chains, are ellipsoid to barrel-shaped .
• Cleistothecia are formed in autumn, gregarious or
scattered, globose, becoming depressed or irregular,
wall cells usually indistinct, 10-20mm wide.
• Appendages are numerous, basally inserted myceloid,
interwoven with mycelium, hyaline to dark brown, 1-
4 times as long as the diameter of the ascocarp, rarely
branched.
• Asci 10-25, ovate to broadly ovate, rarely subglobose,
more or less stalked.

29. MYCELIUM CHARACTERS
• Mycelium is usually well developed and evanescent,
but sometimes persistant and effused.

30. MYCELIUM
©www.flickr.com

31. DISEASE CYCLE
©www.grdc.com

32. EPIDEMOLOGY
MODE OF SPREAD
• The disease develops strongly under dry conditions,
at moderate to high levels of available nitrogen.
• If ascomycota are formed, the fungus may survive a
limited period of time in soil.

33. FAVOURABLE CONDITIONS
• Conditions that favour the host, also favour the
pathogen.
• Spores germinate optimally at 20-25°C under
conditions of high humidity, as quickly as two to four
hours after landing on the leaf.
• Under optimal conditions, infection will lead to the
production of more spores within five to seven days.

34. MANAGEMENT
• Dusting the crop with powdery sulphur @ 15.0 kg per
hectare or spraying the crop with any one of the
following fungicides is effective to control the
disease.
• Neem oil effectively manages powdery mildew on
many plants by interfering with the fungus
metabolism and terminating spore production.

35. • Sulfur and fish oil + sesame oil are effective bio
fungicides that act against powdery mildew.
• Pm3 allele is an effective genetic resistance strategy
that protects host species against powdery mildew
fungus.

36. REFERENCES
• Das.P.C.,2018.Plant Diseases. Kalyani
Publishers,New Delhi.
• Mehrotra.R.S., and Ashok Aggarwal.2017.Plant
Pathology.McGraw Hill Education (India) Private
Limited,Chennai.