Status of wheat diseases in India with a special reference to stripe rust

Wheat is one of the leading cereal which have provided daily sustenance to the large proportion of world's population for millennia. Since the initiation of the Green Revolution in the mid sixties, India achieved remarkable increase in production and productivity of wheat. India is the second largest producer of wheat in the world and wheat production had touched a record of 85.93 mt during 2011. This achievement in India's wheat production has been perhaps the most important and unparallel in the history of developing world. Among the fungal diseases, rusts (yellow, brown and black), Karnal bunt, powdery mildew, foliar blights and loose smut are important. Other region specific diseases of minor importance are head scab, flag smut, foot rot and hill bunt. Control of rusts are more critical for achieving the higher yields. India in particular has not faced any rust epidemic since last three and half decades because of proper deployment of rust resistance genes in wheat breeding programmes. Wheat and wheat rusts have evolved hand in hand for centuries. With the domestication of wheat, new rust resistance genes were introgressed. However, rust pathogens are also evolving consequentially. The rust pathogens are highly variable. The evolution of new pathotypes occurs in each rust render a resistant variety susceptible. Monitoring of rusts is being done every year through extensive surveys and planting trap plot nurseries at hot spot locations. This has helped in identifying rust pathotypes and rust management.

During 2010–11, yellow rust appeared in severe form in plain areas in J & K, foot hills of Punjab and Himachal Pradesh, parts of Haryana, tarai regions of Uttarakhand. In Punjab, especially in the districts of Ropar, Nawan Shahar and Hoshiarpur, the disease was well spread over the area in most of the varieties being grown by the farmers. In Haryana, disease was severe in Yamuna belt. The weather was very congenial for the yellow rust and most of the varieties being grown were susceptible but timely action saved the crop from major damage. The surveys conducted revealed that stem rust was at the lowest level as in the past throughout the country. It was spotted in traces only at Khedgaon in Maharashtra. There was no report of the stem rust pt. Ug99 from anywhere in the country. Leaf rust incidence was low in NWPZ, however it was found in severe form in some local varieties in Karnataka and Maharashtra. Survey for rusts was also undertaken in off season in high hills of Himachal Pradesh and J & K. Twenty six pathotypes (pts.) were identified in more than 400 samples of leaf rust from 13 states of India and Nepal. 121R63-1 was the most predominant pathotype, followed by 21R55. About 700 samples of yellow rust were analyzed from 8 states of India and Nepal. 78S84 and 46S119 were the most prevalent pathotypes in NWPZ and NHZ. Another pathotype which was detected in a few samples, was 47S102. Stem rust was mainly confined to the Nilgiri hills from were 34 samples were analyzed, which yielded pt. 62G29, 62G29-1 (Sr 24 virulent pt.). Both these pathotypes were present in Maharashtra. Seven Lr genes (Lr1, 10, 13, 19, 23, 24, 26, 28 and 34), ten Sr genes (Sr2, 5, 7b, 8a, 8b, 9b, 9a, 11, 24 and 31) and four Yr genes (Yr2, A, 9, 8 and 27) were postulated in popular cultivars and advance lines of wheat. Keeping in view the narrow genetic base for stripe rust resistance in Indian material, there is an urgent need to broaden the genetic base for stripe rust resistance. This will help in developing stripe rust resistant varieties for nutritional and food security of the country.