Virulencia de la roya amarilla del trigo en las principales zonas productoras de riego en México

wheat yellow rust caused by puccinia striiformis f. sp. tritici could infringe huge losses in the wheat yield crop (triticum aestivum l.), planted under irrigated conditions during the winter season in mexico. this is in part due to the fact that the fungus have the capacity to evolve and overcome previously resistant varieties. because of the presence of new forms of virulence, during the crop seasons autumn-winter 2005-2006 and 2006-2007 the virulence analysis of this pathogen was carried out in irrigated wheat production areas in the states of guanajuato, jalisco, sonora and baja california norte. rusted leaves and heads were collected and processed at the international center for wheat and maize improvement (cimmyt). race identification was done by means of 24 wheat yellow rust differentials. during the crop season 2005-2006, 16 different races were identified, whereas during 2006-2007 12 races were identified in the states of baja california norte, sonora, jalisco and guanajuato. during the crop season of 2005-2006 in baja california norte virulence for the resistance genes yr1, 2, 6, 7, 8, 9, 17, 27, poll and a were present, whereas in guanajuato and sonora virulence for genes yr1, 2, 6, 7, 8, 9, 17, 27, y a.was found. during the crop season of 2006-2007 in sonora virulencia for yr1, 2, 3, 6, 7, 9, 17, 27, poll and yra was found. virulence for the yellow rust resistance genes yr1, 2, 6, 7, 9, 17, 27, poll and a were found in the states of jalisco and guanajuato. during the season of 2006-2007 virulence for yr8 was not found; but virulence for yr1, 2, 3, 6, 7, 8, 9, 17, 27, poll and yra was present. none of the races identified is associated with the presence of one resistance gene in particular but the presence of virulence for yr27, yr2 and some other non-identified race-specific resistance genes obligate to plant breeder to considerer the presence of this disease before a new variety is released, specially in those areas where yellow rust was not considered