Stripe rust is the most important disease of wheat in Ecuador. Knowledge of race diversity of the pathogen population is limited. Here we present avirulence/virulence phenotypes found in Pst samples collected from wheat between 2001 and 2014. A total of 30 isolates from the Ecuadorian highlands were tested on 15 near-isogenic wheat lines carrying single resistance genes; 21 races were identified. Lines with Yr2, Yr3, Yr26 and Yr27 were not tested in some years. Virulences to Yr1, Yr6, Yr7 and Yr9 were the most frequent (over 70%) in all years, followed by virulence to Yr17 (67%) and Yr27 (53%). Virulence to Yr8 was not found in 2013 and 2014. Virulence to Yr24/Yr26 was present in each year except 2014, although at a low level. Virulence to Yr10 was low. There were some unconfirmed discrepancies from a perfect association of virulences to Yr24/Yr26 and Yr10. Virulence to YrSP increased up to 2013, but was absent in 2014. There was no virulence to Yr5 and Yr15. Despite limited sampling, a diverse population of Pst seems to be present in Ecuador, with virulence for most resistance genes being present. Based on these analyses resistance to Pst in Ecuador could be achieved with Yr5 and Yr15, together with Yr24Yr26, and perhaps YrSP. One possibility for the high pathogenic variation might be sexual recombination on one or more of the 32 Berberis species reported in Ecuador. This needs to be examined along with more intensive sampling from wheat and analysis of the actual resistance genes present in current cultivars.
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Identifying and tracking new races of wheat rust pathogens in a timely manner is important for early warning of disease potential in wheat-growing regions. Ecuador, located in northwestern South America, serves as a strategic monitoring location for rust fungi between the wheat production areas of North and South America. New races are likely to occur more often when the fungus is in the proximity of the alternate Berberis species host. More than 30 Berberis species have been reported in Ecuador, most of them endemic. However, most herbarium collections correspond to types, have only been found once, and/or date back 20 years or more. Therefore, the current status of diversity in Berberis spp. in Ecuador is largely unknown. Our goal is to collect Berberis species in Ecuador, document their distribution, prepare herbarium specimens, and identify the species morphologically and genetically. We will use this information to establish the relationships of neotropical Berberis species with Berberis in other parts of the world, and determine the pathogenicities of various rust fungi associated with them. Preliminary results show that the Ecuadorian Berberis spp. are phylogenetically distinct from those of Argentina and Brazil. To date, the rust fungi on Ecuadorean Berberis do not infect wheat. We have identified three potentially new rust fungal species based on DNA analysis.