The impact of yellow rust on quantitative and qualitative grain yield losses of five Egyptian wheat cultivars, i.e. Shandweel-1, Gemmeiza-11, Sids-1, Sids-12 and Sakha-94 was estimated under field conditions during 2019/20 and 2020/21 growing seasons. The wheat cultivars, Gemmeiza-11 and Sids-12 were recorded the highest final rust severity (FRS %), rate of yellow rust increase (r-value) and area under disease progression curve (AUDPC) compared to the check variety (Morocco). Where, FRS% ranged from 63.33% to 83.33%, r-value ranged from 0.043 to 0.063 and AUDPC ranged from 783.33 to 1350.00, respectively. The actual loss (%) values in five tested wheat varieties were ranged from 1.31% to 30.33% of 1000 kernel weight/gm and from 2.55 to 36.44% of the grain yield/plot (kg), while total losses (%) value was more than the actual loss (%) during the two seasons. Technological traits showed that Protein, carbohydrate and gluten content were the least in the highly susceptible wheat varieties. The regression analysis showed that a positive strong correlation between AUDPC and total losses of 1000 kernel weight (gm) (0.998, 0.934) and grain yield/plot (kg) (0.989, 0.994), respectively, during the two growing seasons. By studying climate changes (rainfall, relative humidity and wind speed), it become clear that the first season was more appropriate for the emergence of the disease in an epidemic than the second season.
