Use of Infection‐Type Data to Identify Genes for Low Reaction to Puccinia recondita in Several Winter Wheat Cultivars 1

Knowledge of similarities and differences between cultivars in genotype for reaction to different pathogens is useful in the management of gene resources in disease control programs. To obtain such information about some important winter wheat ( Triticum aestivum L.) cultivars, we analyzed infection types produced by 30 cultivars and 20 lines having known Lr genes, each inoculated with 22 Puccinia recondita Rob. ex Desm. cultures. Analyses were made by comparing infection‐type spectra produced by the various host lines with the set of cultures. On the basis of these comparisons, we hypothesize that ‘Parker’, ‘Centurk’, ‘Centurk 78’, ‘Rocky’, and ‘TAM W‐105’ have Lr10 . These cultivars also produced low infection types with LR10(TC) virulent cultures; thus they must also have Lr genes other than Lr10 . The already known presence of Lr24 in ‘Parker 76’, ‘Sage’, and ‘Payne’ was indicated by these data. We hypothesize that Parker 76 has other Lr gene(s) in addition to Lr24 because of the occurrence of ✕‐infection types with ‘Agent’ virulent cultures. The Lr9 genotype of ‘Arthur 71’ and ‘Riley 67’ was also indicated. We hypothesize that ‘Newton’ and ‘Plainsman V’ have Lrl , and that Plainsman V has Lr3a . Newton must have other Lr gene(s) that are not Lr3a , based on low infection types produced with LR1(TC) and LR3A(TC) virulent cultures. Our indicated the presence of the now ineffective Lr3a in several other cultivars: ‘Bennett’, ‘Homestead’, ‘Gage’, ‘Lancota’, and ‘Warrior’. Hypotheses about host genotypes based on infection‐type data analysis have usually, but not always, been shown to be correct when the hypothesis is tested by making appropriate host crosses and inoculating their progeny with appropriate cultures. Intermediate ✕‐infection t~es were common in the hard red winter wheats and are believed to be important in disease control.