WILTING

Wilt:
1. Fungal
2. Bacterial
3. Nemic
4. Sclerotial wilt/ foot rot/ soft rot/

Vascular Wilt:

They collapse the vascular system of the plant.

Two types:

1. Fungal wilt

2. Bacterial wilt e.g. Ralstonia solanacearum (Previously known as Pseudomonas solanacearum)

1.Fungal Wilt:

a.     In tropics or subtropics Fusarium wilt by F. oxysporum

b.     In temperate Verticillium wilt by V. alboatrum or V. dahlia

Formae species of Fusarium oxysporum:

Sl	Formae species	Host
1	Fusarium oxysporum f. sp. lycopersici	Tomato
2	F. o. f.sp. melongena	Brinjal
3	F. o. f.sp.conglutinans	Cucurbits
4	F. o. f.sp.cucumerinum	Cucumber
5	F. o. f.sp.cubense	Banana
6	F. o. f.sp.vasinfectum	Cotton
7	F. o. f.sp.dianthi	Carnation
8	F. o. f.sp.melonis	Muskmelon
9	F. o. f.sp.niveum	Watermelon
10	F. o. f.sp.tuberosi	Potato
11	F. o. f.sp.pisi	Pea
12	F. o. f.sp.lini	Flax
13	F. o. f.sp. batatas	Sweet potato
14	F. o. f.sp.tracheiphilum	Soybean, cowpea

Symptoms of Fusarium wilt:

1.     Epinasty

2.     Wilting phase

3.     Yellowing phase

4.     Vein clearing

5.     Drying

Development of Fusarium wilt:

Stage 1: The leaves start dropping out at the margin.

Stage 2: Total leaves drop out

Stage 3: Leaves become yellow

Stage 4: Chlorophylls start to degrade and the veins become clear.

Stage 5: The entire plant becomes dried.

Some important features about Fusarium wilt:

1.     Fusarium wilt occurs more at reproductive stage than vegetative stage.

2.     Partial wilting is observed.

3.     Partial wilting depends upon movement of the toxin secreted by Fusarium.

4.     Chocolate or deep brown discoloration is seen in the vascular system after transverse cut. (The color is light brown in case of Verticillium wilt.)

2. Bacterial Wilt:

Symptoms of bacterial wilt:

1.     Normally vegetables are affected by the bacterial wilt.

2.     It is occurred more in early vegetative stage.

3.     Total foliage wilts completely and die within 2-3 days.

4.     Light brown discoloration found in the vascular system when cut transverse.

5.     This discoloration is occurred due to bacterial ooze, cell etc.

6.     Bacterial ooze is secreted from the affected portion.

7.     If an affected cut portion is kept in a beaker of water, the water will be dizzy.

Mechanism of Wilting:

Water and minerals pass upward through xylem vessel. This is also called water conducting vessel. Bacteria collapse this vessel so that water can not pass upward. Water deficiency is occurred. As a result for the lack of water wilt is happened.

Bacteria secrets enzymes in the affected plants, which results in opened stomata. The stomata remain open all the time and never closed. Water is lost through stomatal opening. For the excess dehydration wilt can be occurred.

MECHANISMS OF WILTING:

1.     Presence of pathogen within the vascular bundle.

2.     Activity of pathogen in the within the vascular bundle.

1.     Presence of Pathogen in the Vascular Bundle:

Fungus- mycelium, hypha, conidia,

Bacteria- bacterial cell, colony, ooze.

2.     Activity of Pathogen:

 i.      Production of polysaccharide in xylem vessel.

ii.      Production of gum and gell.

     Pathogen secrets enzyme, which breaks down the cell wall. Substances of cell wall enters into         the intercellular space and then produce gum and gell like substances.

iii. Excessive division of parenchyma tissue.

    For the presence of enzyme and toxins, parenchyma cells devide excessively and intercellular         spaces become collapse.

iv. Formation of tylases in the vascular bundle.

    Balloon shaped overgrowth in the parenchyma cell is called tyalase. For the presence of enzyme     and toxins, tyalase is produced. Toxins are Fumosin-B1, Fusario toxin, Nivalenol, etc.

v.  Movement of toxins in the leaves, resulted vein clearing  and disruption of cell permeability.