4. introduction
โข The onion, is an important vegetable crop grown
in India.
โข Scientific name Allium cepa.
โข Also known as the bulb onion or common onion
โข Belong to family Alliaceae.
โข Use as salad and for cooking with vegetable.
โข Onion has several medicinal use; its use in case of
sun stroke is known worldwide.
โข prevent cardiovascular disease.
5. Contiโฆโฆ
โข Help to detoxify the
body
โข Reduce blood
pressure.
โข Reduction in
osteoporosis.
โข Reduce stomach
Ulcer.
6. History
โข Quadri et al., (1982) reported that the onion
spoilage caused by A. niger was as high as 80
per cent.
โข Rajam (1992) reported that among the post-
harvest diseases of onion, black mould rot
caused by A. niger was the predominant one.
โข Cook et al.,(1996), EL Hassani et al.(2007)
reported biologically and chemically
controlling modes of action.
7. Causes
โข High temperature favor
the growth of A.niger.
โข The effect of ozone on
A.niger causing black
mold rot disease.
โข Spores of this fungus
very common in air and
soil that are the source
of infection.
8. Disease symptoms
โข Infection through neck
tissues as foliage dies
down at maturity.
โข Infected bulbs are
discolored black
around the neck, and
affected scales shrivel.
9. Contiโฆ
โข Masses of powdery
black spores develop as
streaks along veins on
and between outer dry
scales.
โข Infection may advance
from the neck into the
central fleshy scales.
10. Diagnostic procedure
Growth of A.
Niger on PDA
media
After 3 to 4 days yellow
and white mycelia
covered by the thick
layer of large, brown to
black globose, conidial
heads.
11. Transmitting agents
Transmition
โข The pathogen is transmitted by contaminated
soil or seed and The infection usually begins
at germination of onion seeds and may
continue throughout storage.
โข Also transmit by air or water
12. Favorable condition
Black mold is common ;
โข High temperature in field (more than 30%).
โข Free moisture contents/high humidity (more
than 70%).
โข On high temperature in storage (more
than24%).
13. Treatment
Two methods are involved to reduce the
mycelial growth of A.niger;
1. Chemical control
โข Metalaxyl, a phenylamide
โข Subdue, a mefenoxam
โข Antibiotics, a cycloheximides
2. Biological control
โข Antibiotics, diacetylphloroglucinol,
phenazine.
14. Management
Cultural control:
Before planting:
โข Use a 2-3-year rotation between successive
crops of onion and its relatives on the same
land.
โข Choose land with good drainage.
โข Ensure that seed is "clean", i.e., free from
spores,
15. Management
and that transplants are healthy.
โข If you are not sure about the quality of the
seed, treat it with hot water at 60ยฐC for 15
minutes.
During growth:
โข Do not harvest crops during wet weather.
After harvest:
โข Collect and burn all debris after the harvest.
16. Contiโฆ.
โข Carefully dry bulbs after harvest and before
storage and marketing.
โข In hot climates, make sure that the humidity is
below 80%.
17. Resistant Varieties
โข Varieties of onions with red scale leaves tend
to be more resistant to Aspergillus niger due
to the presence of phenolic compounds that
have antifungal properties.
18. Conclusion
โข Black mould rot is a major field and storage disease of onion causing serious
storage losses at harvest.
โข Great economic losses in onion growing countries including India.
โข The emphasis should be given on a management approach including;
๏ผ selection of healthy planting material,
๏ผ crop rotation,
๏ผ soil solarization,
๏ผ deep ploughing,
๏ผ chemical control,
๏ผ field cares,
๏ผ harvest cares and storage cares for effective management of black mould of
onion.
