Abstract
Survey of tie 11 districts of the province of Punjab, Pakistan revealed the 1313121ureincie of seven playaiologioal races of Leaf rust of wheat (Puccipria recancilita Rob. Ex Desna) during the year 1981-82. The most prevalent was race 77 (72.0) followed, by race 144 t1.1.9%), 149 (.6..2%), 12 (3,7/i,), 157 (2.5%4 122 (2,5%) and 117 (1.2%). Race 117 prevalent only in Faisalabad division and race 122, recorded from Faisalabad and Mahan divisions, are a new record in Pakietan,„
INTRODUCTION
Rustle cause enOrMillts 1044E4 to wheat crop and leaf rust is the most destructive due to its time. of appearance and prolonged season for development. in wheat growing tracts of Pakistan. More than 10 percent losses due to leaf rust were reported. (Hassan, 1979) during the leaf rust epidemics of 1978 and 1979. The sporadic appearance of epidemics during certain years and the break down of resistan.ec in othEr years ie due to the fact that race eEtuation ie ever changing through hybridization and ululation of the leaf rust fungus. The introduction and cultivation of susceptible cultivars results in the build up of the population of new virulent races leading to the sporadic out-breaks of el)iiicEnitAp esPeciallY when environmental conditions are favourable for such out.brealic The success of a resistance breeding program depends upon the knowledge of the source of genetics resistance against these races, This paper reports a survey on the identification and prevalence of races during the year 1981-82,
Puccini& recondita Rob. Ex Desna. is a fungal speoilizA, into numerous physiological raced (Johnston. and Browder, 1906) that can be idantified by their reactiors on certain wheat varieties and more than 200 races of leaf rust (LH) are known (Johnston and Levine, 1955), Relatively a few races are prevalent and widely ilstributed in Pakistan (Masan et al, 1978), The most. prevalerit
