New specie of Melampsora on Populus deltoides Stoneville 70 in Mendoza, Argentina

In Argentina, as in other places in the world, poplar plantations have always been subject to plant health risks. The rust, caused by Melampsora spp., is one of the most serious illnesses at world level. The classification of Melampsora species is mainly based on the morphological characteristics of the states uredial and telial, and the hosts they have in those states. Since pustules with different characteristics of Melampsora larici-populina (only species refered for the province of Mendoza) were observed, the objective of this work was to identify the kind of Melampsora observed in poplars of clone Stoneville 70, located in the district of San Carlos, Mendoza province, Argentina. For that reason, samples of symptomatic leaves, were drawn at random to carry out a symptomatic and microscopic description. As a result, the morphometry of 100 uredosporas and teliosporas was registered. The analyzed characteristics, are consistent with those reported in bibliography about the M. larici-tremulae, M. magnusiana, M. pinitorqua and M. rostrupii species. Because these species are difficult to be distinguished, Wilson and Henderson (1966) take the name of M. populnea as a collective species. Therefore, it is appropriate to mention the species found as: M. populnea, until more detailed studies allow the definitive identification of the micro organism.