IDENTIFICATION OF LOCI IN ARABIDOPSIS THAT CONFER RESISTANCE TO GEMINIVIRUS INFECTION

The infection of susceptible plant hosts by single-stranded DNA viruse s in the geminivirus group depends on the interaction of host and vira l factors for the replication of viral DNA, the expression of viral ge nes, and the movement of virus throughout the plant. This paper report s that two strains of the geminivirus, beet curly top virus (BCTV) dif fer in their ability to infect certain ecotypes of Arabidopsis thalian a. Symptoms appeared on susceptible plants approximately 2-3 weeks aft er inoculation with BCTV-Logan and after 10-15 days with BCTV-CFH. Sym ptoms were more severe in BCTV-CFH-infected plants and included leaf c urling, the formation of stunted, deformed inflorescence structures an d the accumulation of anthocyanin pigments in symptomatic tissues. Ana lysis of viral DNA accumulation indicated that symptom development and severity were correlated with the amount of viral DNA present in the plants. Viral DNA was undetectable in two ecotypes that were phenotypi cally resistant to BCTV-Logan. Studies of viral DNA replication in exc ised inflorescence pieces demonstrated that BCTV-Logan could replicate in tissues from these resistant ecotypes, suggesting that resistance was due to a block in viral movement. Genetic studies of these two eco types indicate that resistance is due to a single, recessive locus. Th is is the first example of a single resistance locus to any geminiviru s. The identification of resistant and susceptible interactions betwee n different BCTV strains and A. thaliana ecotypes provides an excellen t model system for the genetic and molecular analysis of the interacti on of a plant host with this important group of plant pathogens.