Developmental Changes of Recessive Genes-mediated Cucumber mosaic virus (CMV) Resistance in Peppers (Capsicum annuum L.)

Cucumber mosaic virus (CMV) is one of the most important viral diseases in pepper (Capsicum annuum L.), and several genes for resistance were reported in Capsicum spp. In Korea, a single dominant gene that is resistant to $CMV_{Fny}$ and $CMV_{P0}$ has been used for breeding. Recently, a new strain ($CMV_{P1}$) was reported that could infect cultivars resistant to both $CMV_{Fny}$ and $CMV_{P0}$. Therefore, breeding of more robust CMV-resistant cultivars is required. In this study, we surveyed the inheritance of $CMV_{P1}$ resistance and analyzed the location of the resistance loci. After $CMV_{P1}$ inoculation of various germplasms and breeding lines, one accession (ICPN18-8) showed no visual symptoms at 15 dpi (days post inoculation) but was susceptible after 45 dpi, and one resistant line (I7339) showed resistance until at 45 dpi. The latter line was used for tests of resistance inheritance. A total of 189 $F_2$ plants were examined, with 42 individuals showing resistance at 15 dpi and a phenotype segregation ratio close to 1:3 (resistant:susceptible plants). In a lateral ELISA test at 45 dpi, 11 plants showed resistance, and the segregation ratio was changed to 1:15. These results indicate that resistance in C. annuum 'I7339' is controlled by two different recessive genes; we named these resistance genes 'cmr3E' and 'cmr3L,' respectively. To locate these two resistant loci in the pepper linkage map, various RAPD, SSR, and STS markers were screened; only nine markers were grouped into one linkage group (LG). Only one RAPD primer (OPAT16) was distantly linked with cmr3E (22.3 cM) and cmr3L (20.7 cM). To develop more accurate markers for marker-assisted breeding, enriching for molecular markers spanning two loci will be required.