Plant Genome IV Conference

W30
Genetic Analysis of the Interactions Between the Common Bean and the Bean Common Mosaic Virus

The molecular mechanisms responsible for plant responses to pathogen invasion have been brought into focus by the recent isolation and characterization of several disease resistance genes. Moreover, mutation analysis in tomato has revealed the existence of additional genes that can trigger a response similar to that of an already characterized resistance gene. This finding points to the complexity of the plant response mechanisms. The Phaseolus vulgaris - bean common mosaic virus (BCMV) pathosystem lends itself as a model to study host-virus interactions. A dominant resistance (I) and four recessive resistance genes (bc-u,bc-1(1&2), bc-2(1&2), and bc-3) and combinations of them confer unique responses to an array of BCMV strains and other related potyviruses. The I gene confers resistance to strains of serotype B of BCMV, and conditions the development of systemic necrosis in response to serotype A strains. bc-u in combination with bc-3 confer protection against the necrotic strains in I carrying genotypes. We have detected a new gene in the cultivar 'Great Northern 1140' which is a suppressor of the systemic necrosis (Ssn) response conditioned by I. We are using different types of molecular markers to determine the map position of this gene and of other modifiers of the mosaic and systemic necrosis responses. Modifiers have been detected in a RI family segregating only for the I gene.