SCREENING OF PORTUGUESE COLE LANDRACES (BRASSICA-OLERACEA L) WITH LEPTOSPHAERIA-MACULANS AND XANTHOMONAS-CAMPESTRIS PV CAMPESTRIS

Fifty-six landraces of Portuguese coles (Brassica oleracea L.), repres enting fourteen morphotypes, were screened for resistance to Leptospha eria maculans at the cotyledon stage. Three isolates of the pathogen b elonging to three pathogenicity groups were used in the screening. The mean disease interaction phenotype of the B. oleracea landraces with the L. maculans isolates confirmed their differences in pathogenicity. When compared to pathogenicity grouping using a B. napus differential set, a different classification was observed on B. oleracea for the t hree L. maculans isolates, suggesting possible differences in the gene tic interaction between the two plant species and the pathogen. Most o f the Portuguese cole landraces were found to be susceptible to all th ree isolates of L. maculans, although a few have shown intermediate in teraction phenotype. Some accessions, on the other hand, elicit a diff erential reaction with the three isolates tested, and can be further s elected to be used in host differential sets or in breeding for resist ance to black leg. Fifty-four landraces of Portuguese coles, represent ing eleven morphotypes, were also screened in the field for resistance to Xanthomonas campestris pv. campestris. A good level of resistance to the bacterium was found in several of the morphotypes. Accessions o f the 'Penca' type, particularly, were identified as highly resistant. Landraces belonging to the same Portuguese cole group presented a sim ilar range of mean interaction phenotype with the bacterium. Some Port uguese landraces of B. oleracea are potential sources for use in breed ing programs for black rot resistance.