ABSTRACT
554Stem rust caused by Puccinia graminis tritici is the most feared diseases of wheat and known to cause severe epidemics throughout the world. Stem rust resistance gene Sr31 in combination with other stem rust resistance genes kept the stem rust fungus under control until the emergence of Sr31 virulence; designated as TTKSK and popularly known as Ug99, in Uganda during 1998. The emergence of Ug99 is considered as a highly significant event, having far-reaching consequences not only for Africa but also for the global wheat production due to susceptibility of majority of the wheat cultivars to Ug99. Ug99 has got the ability to defeat the resistance imparted by most of the stem rust resistance genes. Since 1998 eleven variants in Ug99 lineage have been detected from different African countries. In India the stem rust prone area is less than 25% of the total area under wheat and commendable diversity for stem rust resistance has been reported in Indian wheat material. Nevertheless the consequences of entry of Ug99 race into the country or independent mutation for Sr31 or other Sr genes cannot be overlooked. Indian advanced wheat material is being continuously screened at Ug99 hot spot locations viz., Kenya, Ethiopia etc. Besides this, strong vigil is being kept on the evolution and spread of new Puccinia graminis tritici pathotypes in India and neighboring countries.
