Aggressiveness of Different Isolates of Coffee Leaf Rust from Cusco and Functioning of PSII of Coffee CV Bourbon

One of the main threats for coffee production is coffee leaf rust (CLR) caused by H. vastatrix.CLR research have predominantly focused on qualitative host-pathogen interactions, however, studies of quantitative aspects of the interaction of coffee and H. vastatrix are less documented.Therefore, this information is crucial for understanding the potential impact of new CLR races, coffee resistance durability and preventing new CLR outbreaks.In this experiment, we evaluated the aggressiveness of different populations of H. vastatrix and the effect on some ecophysiological parameters on coffee cv.Bourbon.Urediniospores of H. vastatrix were collected from coffee farms in La Convencion, Cusco.A total of 15 populations were obtained (from 1RS to 15 RS).The urediniospores were inoculated on coffee cv Bourbon in San Ramn (Chanchamayo).The aggressiveness (in term of Period of incubation, Frequency of infection, Latent Period and Medium latent period) and fluorescence (through OJIP analysis) were examined.It was recorded that a mean period of incubation, latent period and medium latent period for all the coffee leaf rust populations ranged from 18-20.22,28.1-33 and 32-38.14days after inoculation (dds).The variation in the infection period was of 2.75-8 degrees.3RS were also less aggressive than 5RS.At 41 degrees, we observed that the level of chlorophylls fell significantly, ranging from 4.6 to 31.15%.Regarding to OJIP analysis, the majority of coffee leaf rust populations did not cause significant modification in the variation of Fv/Fm displaying a range from 0.51 to 0.73, at 41 dds.In the case of populations 9RS, 10RS, 13RS, 14RS and 15RS, they presented significant fall in the value of Fv/Fm of 15, 27, 9, 18 and 32% at the end compared to the first sampling.On overall, the range of PI varied from 1.69 to 5.18.6RS caused in significant increment of ETo/RC.9RS, 10RS, 14RS and 15RS increased (P0.05) the value of ABS/RC in 23, 149, 74 and 108% (compared to the initial evaluation).9RS showed a significant increment of TRo/RC of 23.5% in the last sampling.Finally, we conclude that weather conditions and plant material used in this assessment caused a rapid period of incubation (IP).It also detected a photosynthetic defense mechanism that consisted in the increment of ABS/RC, ETo/RC and TRo/RC when the levels of Fv/Fm have fallen.