IDENTIFICATION OF RAPD MARKERS INKED TO A BLACK LEAF-SPOT RESISTANCE GENE IN CHINESE ELM

Black leaf spot (Stegophora ulmea) is a common foliage disease on Chin ese (Ulmus parvifolia) and Siberian elms (U. pumila), two species whic h have been widely used as sources of Dutch-elm disease-resistance gen es for interspecific elm hybrids. A dominant gene controlling resistan ce to black leaf spot was identified in a population derived from self -pollination of a single U. parvifolia tree. Using RAPD markers, in co mbination with bulked segregant analysis, we have identified three mar kers linked to this resistance gene. A survey of Chinese-elm hybrids r evealed that the same gene is likely to confer a high level of resista nce to black leaf spot in interspecific elm hybrids, although other ge netic factors may also be involved in the determination of a disease p henotype.