Leaf rust, caused by Puccinia triticina Erkis., has a high degree of virulence variation and durable resistance to leaf rust through breeding makes it challenging. To investigate the sources of resistance in the Spring wheat germplasm, 341 lines were characterized for leaf rust at four different locations under field conditions. Nurseries were artificially inoculated at one location (Faisalabad) and the data was recorded three times on an average interval of 08 days using the Modified Cobb Scale method. Disease severity ranged from 0-100S during 2016-17, while 0-80S during 2017-18. During both years, the genotype HYT 60-5 and the isogenic lines Lr-19, Lr-26, Lr 27+31, Yr-1, Yr-10, Yr-24, Sr-5, Sr-6, AOC-YRA, AOC+YRA, SRGP, SRAC-1 showed no disease reaction. AUDPC/day was calculated to have a deep understanding of the disease progression. Wheat germplasm comprising on 500 lines was also characterized for seedling resistance in the green house using the predominating bulk leaf rust local races. 261 lines were resistant (IT < 3) at the seedling stage, an indicative of major R genes. These source resistances will be used in the breeding program pipeline for durable rust resistance varietal development and food security in Pakistan.