Six flax cultivars were evaluated for rust resistance under field conditions in
2001/2002 and 2002/2003 growing seasons. The tested cultivars could be divided into
two distinct groups. The first group included the susceptible cultivars Dakota, Wilden,
Williston Brown, and Cortland, while the second group included the resistant cultivars
Linore and C.I. 2008. There was a significant difference (p~ 0.05) between any
cultivar belonged to the first group and any cultivar belonged to the second group.
However, the differences were nonsignifigant within each group. Proteins of the
cultivars were separated by SDS-PAGE, and the obtained banding patterns were
visualized by using the Coomassie-blue staining system. Data for rust ratings and
amounts of protein fractions were entered into a computerized stepwise multiple
regression analysis. Using the predictors supplied by stepwise regression, a four-
factor model was constructed to predict rust severity. This model showed the rust
severity differences were due largely to the protein fractions nos. 1 , 1 8, 1 5 and 8,
which accounted for 99.71% of the variation in severity ratings. These results indicate
that SDS-PAGE of proteins may provide a supplementary assay to greenhouse and
field tests to distinguish quantitatively between rust resistant or susceptible genot/pes.