Electrophoretic analysis of detergent-soluble polypeptides of nine races ofPuccinia graminisf. sp.avenaeand their relation toP. graminisf. sp.tritici

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Abstract
Detergent-soluble polypeptides extracted from dormant uredospores of 9 races of oat stem rust (P. graminis f. sp. avenae) were analyzed by 2-dimensional isoelectric-focusing-polyacrylamide gel electrophoresis. More than 280 polypeptides were detected in each race, and at least 22 polypeptides varied among races. Some races had identical patterns and some differed by 4-16 polypeptides. A group of polypeptides, designated pga 1, 3, 4 and 12 was associated with races avirulent on hosts with genes Pg 9 or 15 and with virulence on hosts with genes Pg 1 or 8. Twenty polypeptides present in P. graminis avenae were absent in P. graminis tritici, stem rust of wheat; and 14 polypeptides were found in P. graminis tritici but not in P. graminis avenae. This interspecific difference of 34 polypeptides was more than the number of polypeptides which varied among races, suggesting that specialization into formae speciales involves a wider genetic variation than that for host specificity. Two polypeptides unique to oat stem rust and 2 to wheat stem rust were identified as markers.