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Leaf rust caused by Puccinia triticina Eriks., is one of the main diseases of wheat (Triticum aestivum L.) in Egypt, causing up to 50% of yield losses. Genetic resistance is the most economic and effective means of reducing yield losses caused by the disease. However, breeding genotypes for disease resistance is a continuous process and plant breeders need to add new effective sources to their breeding materials. Among 42 Egyptian wheat varieties screened for leaf rust resistance, only 9 varieties (Sakha94, Giza168, Gemmiza9, Gemmiza10, Gemmiza11, Sids12, Sids13, Misr1 and Misr2) exhibited seedling and adult plant resistance during 2010/11 and 2011/12 growing seasons. Out of 41 monogenic line (Lr genes) tested, only 13 Lr genes (Lr9, Lr10, Lr11, Lr16, Lr18, Lr19, Lr26, Lr27, Lr29, Lr30, Lr34, Lr42 and Lr46) exhibited seedling resistance while, 9 Lr genes (Lr19, Lr20, Lr21, Lr24, Lr29, Lr30, Lr32, Lr34 and Lr44) showed adult plant resistance at both growing seasons. This result may add a depth of their resistance to be exploited as good sources of resistance. Partial resistance traits of wheat seedlings were present in 12 varieties (Sids12, Misr2, Sakha94, Misr1, Sids13, Giza168, Gemmiza9, Sids7, Beniswef4, Sakha93, Gemmiza11 and Sids6), recording the longest incubation and latent period. However, 10 varieties (Sakha8, Sakha93, Giza144, Giza155, Giza156, Giza157, Sids4, Sids5, Sids8 and Beniswef4) were marked as having high level of partial resistance of adult plant, recording ACI less than 20%, AUDPC less than 332.5 and r-value less than 0.101. The highest significant loss percentages were found in susceptible wheat cultivars i.e. Gemmiza7, Sakha61 and Giza164 (12.24%, 12.10% and 9.08%, respectively). However, insignificant loss percentages were found in resistant cultivars i.e. Giza168 (1.87%), Misr2 (2.44%) Sakha94 (2.46%). Inverse relation was present between the disease level and grain yield. Cultivating of resistant cultivars such as Misr2, Giza168 and Sakha94 is recommended to escape heavy yield losses wreaked by the leaf rust disease.

A total of twenty leaf rust resistance genes (Lr genes) were postulated in nine Egyptian wheat cultivars based on infection types (ITs) expressed on the tested cultivars by 72 Puccinia triticina pathotypes compared with the ITs expressed on the monogenic lines. The most carrier genes cultivars were Giza168 and Misr1 each may contain five genes i.e. Lr2c, 10, 18, 24, 41 and Lr3, 10, 19, 22b, 24, respectively. Five cultivars, Sakha94, Gemmeiza9, Gemmeiza10, Sids12 and Misr2 each probably contain four genes i.e. Lr9, 19, 29, 37; Lr18, 21, 24, 41; Lr3, 9, 19, 29; Lr9, 19, 26, 29 and Lr3, 10, 19, 26, respectively. Gemmeiza11 was the least cultivar carrying genes; it probably carries just two genes i.e. Lr24 and Lr41. The most postulated genes were Lr19 and Lr24, each postulated within five cultivars followed by Lr41 within four cultivars. Five Lr genes, Lr3, Lr9, Lr10, Lr26 and Lr29 each within three cultivars. The lowest postulated genes were Lr2c, Lr21, Lr22b and Lr37 each of them was postulated within only one cultivar. Five Lr genes, Lr9, Lr10, Lr19, Lr24 and Lr26 were identified by PCR-based molecular marker. The Lr9 gene was identified in cultivar Sids12 while, Lr10 was identified in cultivar Misr1. The Lr19 was present in two cultivars, Misr1 and Misr2. The Lr24 and Lr26 were absent in all the screened Egyptian cultivars. The obtained results for Lr9, Lr10, Lr19, Lr24 and Lr26 marker were in agreement with and confirm their identification by gene postulation. Markers for Lr9, Lr10 and Lr19 may be useful in marker-assisted breeding. Our findings showed the usefulness of the molecular marker in identifying leaf rust resistance genes in wheat cultivars, especially when used in conjunction with multipathotypes test at the pre-breeding stage. This approach may help understanding the wheat - P. triticina interaction and provide information to build an effective management program for leaf rust disease.