Cucumber Mosaic Virus Isolates Seedborne inPhaseolus vulgaris: Serology, Host-Pathogen Relationships, and Seed Transmission

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Abstract
Selected cucumber mosaic virus (CMV) isolates seedborne in bean (Phaseolus vulgaris) were compared for serological relatedness, host-pathogen relationships, and seed transmissibility. CMV strains B, Le, F, B32, and Pg were found to be serologically indistinguishable by gel double-diffusion tests using antisera to formaldehyde-fixed immunogens (CMV-B and CMV-Le). Detection of CMV in infected bean leaves by gel double-diffusion tests was dependent on extraction in 0.05 M citrate buffer, pH 6.5, with 0.1% sodium thioglycollate (w/v), 0.1% Triton X-100 (v/v), and 1% formaldehyde (v/v). Time of appearance and severity of symptoms induced by CMV-B, and relative virus concentration varied among 32 bean cultivars representing diverse germ plasm. Virus titer was maximal in greenhouse-grown plants 1-2 wk after inoculation with CMV-B, -Le, and -F but declined sharply after the fourth week. CMV seed transmission varied according to variety and isolate and did not occur in seeds from plants inoculated 4 or 6 wk after planting. CMV-Pg occurred in all parts of bean seedlings infected from seed. The implications of these results for detection and diagnosis of CMV in bean plants are discussed.