Thursday, September 10, 2009

Fusarium and Verticillium Wilts of Potato

Crop of potato may be infected by the fungi that cause Fusarium wilt and Verticillium wilt.
The wilt organisms usually enter the potatoes plants through young roots and then grow into and up the water conducting vessels of the roots and stem.
As the vessels are plugged and collapse, the water supply to the leaves is blocked. With a limited water supply, leaves of plants begin to wilt on sunny days and recover at night.
Wilting may first appear in the top of thepotatoes plants or in the lower leaves.
The process may continue until the entire plant is wilted, stunted, or dead. Although potato plants may recover but are they become usually weak, unthrifty, and produce fruit of low quality.

Symptoms Fusarium Wilt

Fusarium wilt symptoms in potato as slight vein clearing on outer leaflets and drooping of leaf petioles.
Potato tubers may show browning of the vascular ring as well as browning at the stem end and decay where stolons are attached.

Verticillium Wilt

Verticillium wilt symptoms on potato are similar to those of Fusarium wilt. Often no symptoms are seen until the plant is bearing heavily or a dry period occurs.
The bottom leaves become pale, then tips and edges die and leaves finally die and drop off. V-shaped lesions at leaf tips are typical of Verticillium wilt of tomato. Infected plants
usually survive the season but are somewhat stunted and both yields and fruits may be small depending on severity of attack.
In potatoes the pathogen may be part of a complex that includes, among others, the root lesion nematode and the bacterial soft rot organism, resulting in premature plant death (“potato early dying disease”).
Tubers from Verticillium infected plants may show light brown vascular discoloration, usually restricted to the stem end.
Brown streaks in the vascular tissue can be observed well up into the plant, which rapidly collapses and dies.

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