Tolerance to cucumber mosaic virus in pepper: Development of advanced breeding lines and evaluation of virus level

Tolerance to cucumber mosaic virus (CMV) was introduced from an Indian small-fruited hot pepper accession, Perennial, into several bell-type sweet pepper lines by means of pedigree and backcrossing breeding procedures. Tolerance was determined to be incompletely dominant and quantitatively inherited. Breeding lines with variable degrees of tolerance were developed based on inspection of visual symptoms after mechanical inoculation. The breeding lines were subsequently tested for their agronomic performance in the field after mechanical inoculation. Their levels of tolerance in the field closely resembled their previous performances in the greenhouse. There was no association between virus accumulation levels in the upper leaves, as determined by enzyme-linked immunosorbent assay (ELISA), and the degree of tolerance to the virus, as determined by either visual symptoms or field performance. We concluded that the basis for developing tolerant breeding lines from Perennial is primarily their ability to recover from high virus titer and not their restriction of virus multiplication.