Competencia entre aislamientos de "Septoria tritici" Rog. Ex. Desm., en trigos harineros ("Triticum aestivum" L

Inoculations with different isolates are done to obtain wheat genotypes resistant to Septoria tritici; however, there is evidence of competition between the isolates that overestimates the resistance response of the genotypes. To check this, the aim of this study was to test three wheat genotypes with different levels of resistance to this fungus, which was inoculated with isolates P8, P9 and B1, individually and in mixtures. The experiment was established in 2006 under a split plot design with three replicates. Pycnidia were collected from the flag leaf and the lower leaf to identify, using RFLPs, the isolates that established and prevailed in the different genotypes. When P8, P9 and B1 were inoculated individually, the original isolate was recovered; when they were inoculated in mixture, P9 was not re-isolated, which evidenced the competition between the isolates and the low aggressiveness of P9.B1 had the highest recovery rate. With B1 and P8, genetic variants were reisolated whose presence was influenced by the wheat genotype and the isolates with which they were mixed. Because competition can reduce the aggressiveness and pathogenicity of the isolates inoculated in mixture, the best strategy in wheat breeding programs to select resistance is to inoculate the isolates individually. Para la obtención de genotipos de trigo resistentes a Septoria tritici se hacen inoculaciones con diferentes aislamientos; sin embargo, existe evidencia de competencia entre estos que sobrevalua la respuesta de resistencia de los genotipos. Para comprobar esto, el objetivo de este estudio fue probar tres genotipos de trigo con diferente nivel de resistencia a éste hongo inoculado con aislamiento, P8, P9 y B1, individuales y en mezclas. El experimento se estableció en 2006 bajo un diseño de parcelas divididas con tres repeticiones. Se recolectaron picnidios de la hoja bandera y de la hoja inferior para identificar, mediante RFLP's, los aislamientos que se establecieron y prevalecieron en los diferentes genotipos. Cuando P8, P9 y B1 se inocularon individualmente se recuperó al aislamiento original; cuando se inocularon mezclados no se reaisló P9, evidenciando la competencia entre aislamientos y la baja agresividad de P9. B1 tuvo la frecuencia de recuperación más alta. Con B1 y P8 se reaislaron variantes genéticas cuya presencia fue influenciada por el genotipo de trigo y los aislamientos con que se mezclaron. Debido a que la competencia puede reducir la agresividad y la patoge