Leveillula taurica (Lév.) Arn., is one of the plant pathogens that infect many plant species. L. taurica is the only known cause of powdery mildew in pepper. Epidemiology of the disease is highly affected by the climatic conditions, on pepper, disease occurs in both humid and dry regions. Crosses between resistant doubled haploid lines provided by the pepper-breeding laboratory (INRA, Montfavet, France).and susceptible Sudanese hot pepper landraces obtained from the gene bank at the Agricultural Research Corporation (Wad Madani, Sudan). The F1's and F2's together, with the parental lines, were evaluated in open fields under natural conditions of infection for two seasons. Two susceptibility indices, sporulation intensity (Sp) and proportion of infection (Pr) were used to evaluate each plant. A general disease index (DI) was obtained by summing up the two indices: DI=(Sp+Pr) in a range of 0-10. The two susceptible parents were diseased, with mean disease index (DI) 6.6 and 6.3 respectively. While the resistant parents were completely resistant (DI=0). The F1's of the three parents were intermediate in their resistance with mean disease index (DI=1.9- 2.3) the distribution of the F2 individuals in DI classes Showed that most of the plants were distributed in the intermediate class (DI=5) and towards the higher intermediate resistance classes (DI=4, 3 and 2).
A linear relationship between the two susceptible indices Pr and Sp was observed in the susceptible parents (r=0.9) and in the F1's where the correlation coefficient is in the range of 0.8 -0.7. In the F2's this linearity is variable due to the low sporulation on the high level of resistance and those of intermediate level plants. The behavior of the F1's and F2's revealed that the resistance of HV lines to Leveillula taurica is controlled by several genes’ of partial effects.