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An Assignment on Seed Gall disease of Wheat

Shrestha k. Rajan

(350025)

(IN PARTIAL FULFILMENT OF THE REQUIREMENT OF PRACTICAL STUDY)

Submitted to

Sunita Adhikari

Plant Clinic Department

Himalayan College of Agricultural Sciences and Technology

Gathaghar, Bhaktapur

February 08, 2010

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Introduction

Seed gall of wheat is one of the earliest wheat diseases and the first disease caused by

a plant pathogenic nematode described.

Also known as Ear cockle

Causal Organism:Anguina tritici (nematode)

Hosts: wheat and Rye

Distribution: It was in the past reported in all the major wheat-growing areas.

However, it has now become rare or locally extinct in many countries. It is still found

in the Near and Middle East, the Asian Subcontinent, China, and parts of Africa.

Symptoms

Distorted leaves and stems are evident prior to heading.

On plant maturity, galls are formed in the florets, replacing the kernels.

The galls are similar in shape to the seed they replace but are dark brown to black in

color.

Large numbers of motile larvae are present within the galls and become active after the

galls have been moistened

Damage

Fig. infested seed and healthy seed Fig. damage on head leaf sheath awn

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If compared to normal wheat seeds, galls are smaller in size, lighter, and their color

ranges from light brown to black (normal wheat seeds are tan in color)

Yield loses up to 70% have been reported, ranging from 30-70% .Threshold of 10,000

juveniles/kg soil

Epidemiology

Cool and moist climate is especially favourable for the development of this nematode.

Wet weather favors larval movement and the infestation process

A film of moisture must be present when the young wheat plants are developing;otherwise, the very active larval nematodes cannot travel from the soil to the growing

point of the seedling.

Disease Cycle

Source: httpwww.ipmimages.org

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At maturity, the galls induced by the nematode contain large numbers of second stage

juveniles which are the survival, dispersal and invasive stage ofAnguina tritici.

Galls already in the soil or sown with contaminated seeds are the sources of infestation.

In the field, galls become moist and soft, facilitating release of second stage juveniles.

Juveniles move progressively to the growing tip until they penetrate the floral

primordia, where they develop to maturity.

Females lay thousands of eggs in the developing seed gall; these hatch and when the

juveniles reach the J2 stage they enter anhydrobiosis.

There is one generation per year Total life cycle is completed in 113 days.

Treatment/control

Seed cleaning and crop rotation together can achieve complete control.

Sieve Method (Mechanical)- Sieves of different mesh sizes are used and gallsare separated from the seed The most effective control is by mechanical seed cleaning

Table Salt Solution: If sieving is not possible, prepare 20% solution ofcommon table salt (NaCl) by dissolving 40 lbs of salt in 25 gallons of water. Galls may

be removed after submersion of the seed (galls float to the surface), followed by

thorough washing in water.

Hot water treatment at 54C for 10 min is also reported to be effective in

killing the nematodes.

In addition to clean seed, carryover from one crop to the next in the same or adjacent

fields needs to be avoided. Hence rotation with a non-host crop

Resistant Varieties: Wheat of Mexican blood is fairly resistant to the disease.

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References http://nu-distance.unl.edu

http://wheatdoctor.cimmyt.org

http://en.wikipedia.org

http://cropgenebank.sgrp.cgiar.org

http://agrihunt.com

httpwww.ipmimages.org