LEAF BLIGHT OF WHEAT

Leaf blight of wheat

Pathogen:-  Alternaria triticina.

 Systematic position of pathogen:- class- deuteromycetes; order- moniliales; family- dematiaceae

Distribution :- This disease causes much loss in various parts of India . this disease was fist observed in 1924 and since then the plant pathologist are busy in various investigations. Several rust-resistant varieties have been proved quite susceptible for this disease. The symptoms of the diseases are not visible on the seedling, and they appear only when the plants become 7-8 week old. Durum wheat has been found to be most susceptible for this  disease. The disease has not been reported from other countries so far.

Symptoms:- is early stage, small , oval , irregular, hyaline lesions are found to be scattered on the leaves. On maturity, these lesions become quite irregular  are brown or grey-colored. The lesions remain surrounded by a bright yellow zone. Several lesions coalesce and cover most of the surface of the leaf, ultimately causing its death. Sometimes the leaves begin to dry up from their  apices. In moist conditions , the lesions are covered with black powdery conidia of the fungus. The lowermost leaves of the plants which are nearer to the irrigation channels get infected first. The symptoms of the disease appear on leaf sheath , leaf blade, ears , awns and glumes.

The pathogen :- disease is caused by Alternaria triticina. The hyphae are branched , septate, and 2-7 micron broad. The conidiophores are septate usually unbranched, rarely branched, erect, single or in group emerging out through the stomata, the conidiophores measure 17-28 micron * 3-6 micron. The conidium is light brown or ark olive-brown in color. Each conidium measure 15-89 micron * 7-30 micron. Each conidium possesses 1-10 transverse septa and 0-5 longitudinal septa.

 Nature and recurrence of disease:- this is a seed as well as soil borne disease. The intensity of the disease varies on different varieties and on an average it Is 12.2 per cent. The inoculums is found to be deep seated in the seed. Seven to fifteen days old seedlings are not susceptible. As the plants become older, they become more susceptible to the disease. If the suitable conditions of moisture and temperature prevail, the ten week old plants are heavily infected by the disease.

Control measures:-

 Hot water treatment-  after soaking the seeds for four hours in water at ordinary temperature, they are again soaked In water at 52 degree Celsius for fifteen minutes. By doing so the seeds become inoculums free and remain viable for sowing purpose.

 Sanitation – since the disease is soil-borne too, after the harvest, plant debris should be collected and destroyed by burning it.

 Resistant varieties- the most economical and suitable method of control is to sow the resistant varieties . they are- NP 4, NP 52, NP 200, NP 824  etc.