Molecular marker detection of the leaf rust resistance genes Lr34, Lr74, Lr75, and Lr80 and their importance for partial resistance in bread wheat genotypes

Wheat productivity suffers from a severe failure to achieve sufficiency, leading to an increase in global economic need. Leaf rust causes an ongoing issue due to the continuous emergence of new physiological races that break out resistant plant varieties. Molecular-assisted selection technology provides information about slow-rusting genes in the genotype gene pool, which could help the breeding process. The present study aimed to screen fifty genotypes for the slow rusting genes Lr34, Lr74, Lr75, and the new gene Lr80. The fifty genotypes were evaluated for leaf rust disease at the Nubaria Research Station during the 2019/20 and 2020/21 seasons. The presence of slow rusting genes was confirmed using a molecular marker tool, which recorded that the highest frequent gene was Lr74 (86%), and the least frequent gene was Lr67 (14%). The numbers and combinations of detected slow rusting genes differed from one genotype to another; Giza 168, Misr 3, and BW55213 had the highest observed number of genes among the studied genotypes. We recommend using these genotypes in pyramiding for durable resistance in breeding programs. Partial resistance was assessed simultaneously using the AUDPC, ACI, r-value, CARPA, and RRI parameters. The results of the field evaluation divided the tested genotypes into two main groups: the first group included most of the tested genotypes, which revealed a high level of partial resistance; the second group included Sakha 93, Gemmeiza 7, Gemmeiza 9, and Sids 1, which showed the lowest values of all the parameters and were classified as fast rusting genotypes.