The Genetics of Host–Parasite Interaction

Studies on the genetics of host-parasite interactions in white rust (WR) diseases have focused on the level of specificity among races of pathogen and genotypes of related host species. Even within the confines of race-cultivar specificity, the studies have been one-side in that no genetic information has been generated on Albugo, the causal organism. The resistance in host is governed by one, two or more dominant genes (AC-7-1, AC-7-2, AC-7-3), additive genes with epistatic effects, and single recessive genes (WPr) along with a single gene (WPR 4) conferring broad spectrum resistance to reces, AC-2,4,7 and 9. The inheritance of virulence in Albugo-Brassica system is controlled by a single dominant avirulence gene AC-2. Resistant genes effective against one or more reces of A. candida have been mapped and identified on the chromosome of B. juncea, B. rapa, B. napus and Arabidopsis thaliana. Slow white rusting, induced systemic resistance and plant defence resistant genes have been identified.