Partial resistance of oats to P. coronata f.sp. avenae

Abstract

Several oat cultivars (Avena sp.) were inoculated on the lst, 2nd and 4th leaves with race 264 of P, coronata f. sp. avenae to characterize and determine components of partial resistance (slow rusting). Panfive was the only cultivar to exhibit partial resistance. It gave a moderately susceptible reaction but expressed a lower infection efficiency, fewer and smaller uredia, and a lower spore production compared to the susceptible cultivars Algerian and Sual for all three leaf ages tested. In the field this cultivar has consistently shown partial resistance. Garry, a cultivar reported to be slow rusting but highly susceptible in the field in Queensland, expressed a significantly lower infection efficiency and uredium density than Algerian and Sual on the first leaf. Older leaves of Garry, however, did not show a significant reduction in the components of partial resistance when compared to Algerian and Sual. Results suggested that uredium density gave the best indication of partial resistance across the three leaf ages tested for Panfive. A significant difference was present between uredium densities on upper and lower surfaces of the 4th leaf only for the susceptible and partially resistant cultivars. In general, the resistance of all cultivars tended to increase with an increase in leaf age.