Characterization of genetic diversity and pathogenicity of Phakopsora pachyrhizi mono-uredinial isolates collected in Brazil

The diversity of Phakopsora pachyrhizi populations has often resulted in the selection of virulent pathotypes following the release of rust-resistant cultivars. Thus, knowledge of the pathogenicity and variability of P. pachyrhizi specie, coupled with an understanding of its biology and host-pathogen interactions, is essential for better comprehension of the evolution and rapid adaption of the pathogen. Such comprehension can be useful for genetic breeding programs and other research areas. Therefore, this study aimed to assess the genetic variability and virulence among P. pachyrhizi mono-uredinial isolates obtained from field samples collected in Brazil during the period from 2007 to 2012 by comparing the sequences of Internal Transcribed Spacer (ITS) regions and AFLP markers and analyzing the responses of differential soybean genotypes. The polymorphisms among the AFLP markers (locally) and ITS sequences (globally) demonstrated the high genetic diversity of this pathogen. Phenotypic analysis revealed the presence of at least 16 different pathotypes present in soybean fields in Brazil. The most effective resistance gene was Rpp5 (PI 200487), followed by Rpp4 (PI 459025) and Rpp2 (230970). This study represents the first report on the virulence and molecular characterization of a collection of P. pachyrhizi mono-uredinial isolates, which might represent different races occurring in Brazilian fields in the period from 2007 to 2012.