Cucumber mosaic virus (CMV) is an aphid-transmitted virus that infects snap bean growing regions in New York State and Wisconsin. The core collection of common bean accessions (Phaseolus vulgaris), the complete collection of scarlet runner bean accessions (Phaseolus coccineus) and snap/dry bean cultivars were screened for resistance to CMV. Although variation in foliar symptom expression was observed, no resistance was observed in 93 snap bean and16 dry bean cultivars tested, and only one of the 406 accessions from the core collection (PI 309881) was symptomless. PI 309881 did not have common bean characteristics, and was later identified as a tepary bean (Phaseolus acutifolius) accession based on morphology and PCR-RFLP of chloroplast DNA. Screening of 260 P. coccineus accessions was inaccurate when a visual rating of foliar symptoms was used. It was necessary to determine infection using ELISA and test plant screening with grey zuccini. Using this approach it was determined that 80 P. coccineus accessions were susceptible to CMV; however, the remaining accessions provided possible sources for transfer of CMV resistance to snap bean. Crosses of P. coccineus accessions were made to breeding line 5-593 and backcrossed to 5-593 and snap bean cultivar `Hystyle'. PI 309881 was crossed with ICA Pijao in order to develop interspecific hybrids. Populations were developed from the interspecific crosses/backcrosses and evaluated for CMV resistance using ELISA and visual ratings of foliar symptoms.
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