The intact avrXccE1 CDS of Xcc 8004 confers avirulence function on the host plant Chinese cabbage (B. rapa subsp. pekinensis) cv. Zhongbai-83 to other Xcc strains. (a) The black rot symptoms on Chinese cabbage cv. Zhongbai-83 infected by the strains CN01, CN05, CN10 and CN11. The avrXccE1-allelic loci of these strains are AHD. (b) The strains CN01, CN05, CN10 and CN11 harboring the plasmid pC2602 (pLAFR6 carrying the intact avrXccE1 gene) show incompatible reaction on Chinese cabbage cv. Zhongbai-83. The photographs were taken ten days after inoculation.