Virulence Diversity of Phakopsora pachyrhizi in Mexico

Asian soybean rust, caused by the pathogen Phakopsora pachyrhizi, is the main soybean disease in Mexico and worldwide, threatening its production. Knowledge about the virulence of Mexican rust populations (MRPs) is crucial to develop or introduce soybean cultivars with resistance to this disease. This study investigated the geographic variation in the virulence of 19 MRPs collected in two states of Mexico (Tamaulipas and Chiapas) using a set of 12 differential soybean varieties. The inoculation of MRPs showed that there was no large difference in virulence to differentials carrying Rpp4 or Rpp5 between MRPs from the two states. However, a contrasting phenotype was observed on Rpp1, Rpp1-b, Rpp2, and Rpp3. In the comparative analysis of virulence profiles with 157 and 20 P. pachyrhizi samples from South America and Asia, respectively, the MRPs from Chiapas form an isolated cluster, including the Tamaulipas state. The MRPs from Tamaulipas clustered with South American samples because of common characteristics, such as virulence to Rpp1 and avirulence to Rpp1-b. However, opposite reactions on Rpp1 and Rpp1-b that have been reported in major U.S. pathogens were also observed in Chiapas samples. A common trend between Chiapas and major U.S. pathogens was also observed in Rpp3. The main conclusion of the present study is that the 1,000-km distance between these two states in Mexico makes a big difference in the virulence of Asian soybean rust. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .