Ear cockle and yellow ear rot diseases of wheat

Ear-Cockle and Yellow Ear-Rot Diseases of Wheat Caused By Anguina tritici

Submitted By :- Jayant Yadav, C.C.S.H.A.University, Hisar, Haryana

Etymology & History

Common name : Wheat seed gall nematode (Anguina tritici)

Etymology :- anguinos = snake-like and tritici = host crop

First PPN to be recorded by Needham in 1743.

Steinbuch 1799 described it as Vibrio tritici.

Filipjev 1936 gave it the name Anguina tritici.

In India, first reported by Milne 1919 from Punjab.

Systematic Position

Phylum : Nematoda

Class : Secernentea

Order : Tylenchida

Suborder : Tylenchina

Superfamily : Tylenchoidea

Family : Anguinidae

Genus : Anguina

Diagnostic characters

Female Adult female obese in the middle, 2.64-4.36 mm long; body coiled when heat relaxed; spear weak; 8-10 1m long with small knobs; oesophagus with a lobed basal bulb; ovary single with one or two flexures, anteriorly extending up to basal bulb, oocytes arranged in multiple rows about a rachis; vulva posterior; tail elongated conoid. Male Shorter than females, 2.04-2.4 mm long, more straight than females; bursa not covering the tail completely,; spicules short and broad.

Fig :- Male and Female of Anguina tritici

Fig :- Adult Female

Distribution and Hosts Distribution Once present in all wheat growing regions of the world including Europe, Asia, USA, Australia, New Zealand, Russian states.

Problem in India, eastern Europe and middle east.

India – Northern wheat growing states : Bihar, UP, MP, Rajasthan, Haryana, Punjab, Delhi.

Hosts

Specific to wheat

Different species of Anguina form galls on different plant parts .

Biology and Life cycle

Parasite of above-ground parts. Source of infection – seed material contaminated with cockles.

Each seed gall (cockle) contains 3000-12000 J2 in quiescent stage.

Gain moisture in soil, become active and come out into soil.

Ascend the growing point of germinating seedlings.

Feed ectoparasitically between leaf sheaths and growing point till earhead emergence

Carried up along the growing plant, shielded among young leaves surrounding growing point.

Enter floral primordia when earhead still inside boot leaf, become endoparasite.

Earheads emerge, nematodes moult quickly to adults inside green galls.

Each gall may contain several adults, mate inside, females lay eggs, fecundity high.

Eggs hatch into J2 , and become quiescent inside the gall as the crop matures.

Only one life cycle in a season. Can survive inside a dried gall for 32 years.

Contd…..

Symptoms Name of the disease – Gegla, Sehun, Mamni, Earcockle.

Above-ground symptoms

Basal swelling of stem at 20-25 days.

Crinkling, curling and twisting of leaves.

Stunting and prostrate growth of the crop.

Increased tillering.

Earhead formation preponed.

Affected earheads are shorter and broader.

Glumes arranged loosely.

Galls replace the seeds.

Fig :- Basal Swelling, Crinkling and Curling of Leaves

Fig :- Healthy v/s Diseased Earheads

Fig :- Nematodes emerging from Green Galls

Fig :- Cockles and Healthy Grains

Fig :- Contents Of Ear Cockles ( i.e J2 ’s emerging from cockles )

Interaction with other pathogens Anguina tritici + Clavibacter tritici = Tundu disease or Yellow ear rot Nematode acts as vector.

Initial symptoms same.

Low temperature and High humidity favour disease.

Yellow slimy ooze on leaves, stem, earheads.

Upon maturity, turns brown.

No grain formation.

Earheads may not emerge from boot leaf.

Tundu is more damaging than ear cockle.

Control

Separation of cockles from seed.

Dry cleaning

Winnowing/Fanning

Plain Water or Salt water (10-20%) floatation.

Seed galls float on surface, seeds sink

Skim off the galls and destroy them

Use of certified seed.

Possible to eradicate both diseases easily.

CONCLUSIONS

In typical bacterial ear-rot disease, nematodes were not found in infected tissues.

Plants whose ears showed bacterial symptoms only rarely showed nematode galls.

Although such plants always showed typical symptoms of nematode attack in early stages of their growth.

Whenever an ear was partially infected with the bacterium the rest of the ear had normal wheat grains and only very ocasionally did the bacterium infected ears show gall formation. These galls however did not contain viable larvae.

In such instances , larvae had entered the wheat ovaries before the bacterium became the dominant pathogen.

In low concentrations bacterium is present without affecting nematode viability. But under favourable conditions of plant host the bacterium multiplied rapidly and produced an environment in which nematode can not survive.