The disease of field and horticulture crops and their management || 3(2+1), Sclerotinia stem rot of sunflower , Symptoms, disease

1. ASSIGNMENT
Sclerotinia stem rot of sunflower
Disease of field and horticulture crops
and their management || 3(2+1)
2020-21
Ravi Yadav

2. Sclerotinia stem rot of sunflower
SYMTOMS
The study of symptomatology resulted in diagnosis of the disease as
Sclerotinia stem rot of sunflower. The initial symptoms produced on roots,
stems, leaves and other aerial parts of plant were examined under natural
infection. Appearance of lesions and the development of disease at different
stages of plant growth were also studied. Sclerotia formation was noticed
On different parts of plants .
Causal organism - Sclerotinia sclerotium
Etiology
The lifecycle of Sclerotinia sclerotium can be described as monocyclic, as there
are no secondary inoculums produced. During late summer/ early fall the
fungus will produce a survival structure called a sclerotium either on or inside
the tissues of a host plant. The following spring the dormant sclerotia will

3. germinate to produce fruiting bodies called apothecia, which are small, thin
stalks ending with a cup-like structure about 5-15mm in diameter (similar in
shape to a small mashroom). The cup of the apothecium is lined with asci, in
which the ascospores are contained. When the ascospores are released from
the asci, they are carried by the wind until they land on a suitable host. The
ascospores will then germinate on the host and begin to invade the host's
tissues via mycelium, causing infection. S. sclerotium is capable of invading
nearly all tissue types including stems, foliage, flowers, fruits, and roots.
Eventually white, fluffy mycelium will begin to grow on the surface of the
infected tissues. At the end of the growing season, S. sclerotiorum will once
again produce sclerotia. The sclerotia will then remain on the surface of the
ground or in the soil, on either living or dead plant parts until the next season.
Life cycle
The pathogenic fungus Sclerotinia sclerotium proliferates in moist
environments. Under moist field conditions, S. sclerotium is capable of
completely invading a plant host, colonizing nearly all of the plant's tissues
with mycelium. Optimal temperatures for growth range from 15 to 21 degrees
Celsius. Under wet conditions, S. sclerotium will produce an abundance of
mycelium and sclerotia. The fungus can survive in the soil mainly on the
previous year's plant debris. Like most fungi, S. sclerotium prefers darker,
shadier conditions as opposed to direct exposure to sunlight.
Management

4. 1. Use crop rotation do not plant highly suseptible crops more than once in for
icluding dry ediable beans,sunflower,musterd and canola .
2. Use atlest a five year rotation for severely infested fields.
3. Avoding planting next to a field that had severe sclerotinia in the past four
or five year .
4. Controll broad leaved weeds.
5. Plant throughly cleaned seed.
Refrence:
Agrios,george N.plant pathology .5th
ed.. burlington, MA:Elsevier Acedimic press
2005. 546- 550. print