Yellow rust of wheat

Yellow rust of wheat

Pathogen:- Puccinia striiformis.

Distribution:-The yellow rust is limited to northern and eastern India, and rarely occurs in peninsular and eastern India. In comparison to other rust diseases of wheat, it appears earlier. The disease is seen in middle of January and if there are heavy rains it does much damage to the crop.

Symptoms :- The uredia are chiefly formed on the leaf blade, but when the attack is severe, they also appear on the leaf sheaths, stalks and glumes as well. Sometimes, the rust pustules are also seen on the pericarp and kernels. The green color of the leaves fades in long streaks, on which rows of small uredo-pustules appear. Each row consists of a series of oval, lemon-yellow pustules arranged end to end and each pustule remains distinct from that above and below. The uredospores eventually break through the epidermis and yellow uredospores are shed.

The telia appear later as dull black patches in long narrow lines resembling the uredia. The telia are sub-epidermal and remain as flat black crusts.

Uredospores:- The uredospores are nearly round and not oval or elliptic as in black rust. They measure 23 to 35 * 20 to 30 microns and possess a hyaline wall provided with fine spines and with 6 to 10 scattered germ spores. On germination, a small, fragile appressorium is formed over a stoma. The entry tube swells up to a large, thick-walled, cylimdrical, sub-stomatal vesicle, up to 19 micron broad and place just below the stomatal opening. From this as infection hypha arises.

Teliospores:- The teleutospores are dark brown, two-celled, often flattened or oblique at the top, and measure 35 to 63 micron *12 to 20 micron. The teliospores may occupy the complete telium or may be broken up into groups by rows of brown paraphyses. The yellow rust is heteroecious, but the alternate host is still unknown, and therefore, the pycnial and aerial stages have not been observed.

Nature and recurrence of disease:- The disease is air-borne. The inoculums causing the annual recurrence is brought from the hills to the plains every year. The uredospores of Puccinia striiformis over-summer on hill at 7000 feet and above.

Control measures:-  

Resistant varieties- Use resistant varieties is very simple and effective method to control this disease.

Chemical measure- Foliar spray of Tilt @ 0.1% for the control of brown and yellow rust and also spray of Plantavax @0.2% is used to control yellow rust