The use of quantitative resistance as a form to control oat (Avena sativa) crown rust can be a viable alternative, once there is differentiated reaction among oat genotypes in field, which shows great variation. The slow disease progress observed in the field is the result of combined effects of resistance components as low infection efficiency, longer latent period, low number of spores per pustule and little pustules size. This work was accomplished in 1999 and 2000, and its objective was to quantify the resistance components above mentioned in 31 white oat genotypes. The reaction of these genotypes was evaluated in the field, from 1996 to 2000, and they were classified in four groups. Evaluation of resistance components was accomplished in seedlings and adult plants maintained in controlled conditions, and the last two components were also quantified in leaves collected in the field trials. Genotypes showed variability for all measured characteristics, except for latent period in seedlings, and those genotypes classified as resistant in the field presented the best combination of desirable components.
