RESISTANCE TO RACE-2 OF PERONOSPORA-PARASITICA IN UNITED-STATES PLANT INTRODUCTIONS OF BRASSICA-OLERACEA VAR CAPITATA

Evaluations for resistance against race 2 of downy mildew incite by Peronospora parasitica Pers. ex Fr., were conducted on 325 U.S. Plant Introductions (PI) classified as Brassica oleracea var. capitata L. (cabbage). A disease index (DI) was calculated for each entry. In 77 of the tested PIs, from 2% to 100% of the plants had reaction phenotypes less-than-or-equal-to 3. The DIs for 24 PIs were significantly lower than the DI for the most resistant cabbage control, 'Headstart' (DI = 5.9). Eight of these PIs were highly resistant, because all plants had a reaction phenotype less-than-or-equal-to 3. However, most of these eight are apparently misclassified as B. oleracea var. capitata.