Specific resistance factors to yellow rust in seedlings of some French wheat varieties and races of Puccinia striiformis Westend in France

— Infection types in Triticum aestivum L seedlings induced by 9 French races of Puccinia striiformis Westend were used to assess the hypothetical content of specific genes for resistance to yellow rust in 21 wheat varieties widely grown in France.Resistance to the race 0E0 showed that none of the varieties lacked resistance factors.Most of the varieties possessed only 1 to 3 known Yr genes.The postulated genes were Yr 1, Yr 2, (Yr3a + Yr4a), Yr6 and Yr7.The varieties Festival, Fidel, Beauchamp, Gala, Castan, Scipion, Caton, Darius, Top, Soissons, and Thésée may carry one or more resistance factors belonging to the set of SD (Strubes Dickkopf), Yr 2, and (Yr 3a + Yr 4a).Further hypotheses were developed with the use of British races.Top was postulated to possess (Yr 3a + Yr 4a) and Darius to have Yr 2. Yr 7 was postulated in Prinqual, Talent, and Tango.Corin probably possesses Yr 1 and might also carry Yr 2 and/or ( Yr 3a + Yr 4a).Garant and Hardi may possess Yr 7 7 and Yr 2 or ( Yr 3a + Yr 4a).Récital and Austerlitz had reactions consistent with the presence of Yr 6, and the latter may have an extra gene.Camp Rémy and Arminda were resistant to all races tested.Surveys of P striiformis showed the importance of races whose virulence spectra were able to match most of these resistance genes.Two races (45E140 and 45E172) were mostly responsible for the 1987 and 1988 epidemics; 3 others (41 E136, 109E141, and 109E173) were also important.Triticum aestivum L / Puccinia striiformis Westend / virulence / Yr genes Résumé — Résistance spécifique à la rouille jaune de variétés françaises de blé tendre au stade plantule et inventaire des races de Puccinia striiformis Westend en France.Les facteurs de résistance spécifique à la rouille jaune ont été recherchés au stade plantule sur 21 variétés de blé tendre parmi les plus cultivées en France.9 races de Puccinia striiformis Westend d'origine française ont été testées sur la totalité de l'échantillon et 11 races d'origine de résistance générale.En effet, le suivi des races de P striiformis a montré leur complexité.Les races présentes en 1984 et 1985 dans les pépinières des sélectionneurs étaient virulentes sur Yr1, Yr2, ( Yr3a + Yr4a), Yr7 et celles res- ponsables de l'épidémie de 1987 et 1988 portaient les virulences capables de surmonter Yr 1, Yr2, (Yr3a + Yr4a) et Yr6 (45E140, 45E172) et certaines également Yr3b etYr4b (109E141 et 109E173).