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

Abstract

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 F2 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. Additional key words: linkage group, RAPD

Pepper Crop Improvement Against Cucumber Mosaic Virus (CMV): A Review

“…The optimal time point for the identification of resistance to CMV in pepper is at an early stage of plant growth ( Agrios et al, 1985 ; Dogimont et al, 1994 ). Generally, seedlings are inoculated with inoculum at the cotyledon stage to 6-leaf stage (cotyledon stage, 1–2 leaf stage, 3–4 leaf stage, and 5–6 leaf stage) by manual rubbing ( Caranta et al, 1997 ; Chaim et al, 2001a ; Yao, 2013 ; Min et al, 2014 ). According to Tian et al (1989) , the 3–6 leaf stage is the best inoculation period for assessing the resistance level of pepper resources because young seedlings can show a higher disease index at the cotyledon stage and 1–2 leaf stage, while old seedlings show lower values at the 7–8 leaf stage.…”

“… Yao (2013) evaluated several breeding lines and accessions of C. annuum and found a resistant accession “ BJ0747-1-3-1-1 .” Screening of 199 genetic pepper resources by Shin et al (2013) resulted in the identification of 32 resistant or moderately resistant Capsicum accessions to CMV P 1 . Min et al (2014) reported three accessions, “ I7339 ,” “ ICPN-18-8 ,” and “ Daedlbo ,” with resistance to CMV P 1 . More recently, several accessions with resistance to CMV were identified from 50 pepper resources ( Naresh et al, 2016 ).…”

“…Kang et al found that resistance in “Bukang” is under the control of a single dominant gene ( Kang et al, 2010 ). Min et al (2014) reported two different recessive genes conferring resistance to CMV in C. annuum “I7339.” More recently, Choi et al (2018) showed that resistance in C. annuum “Lam32” is controlled by a single recessive gene, CMV resistance gene 2 ( cmr2 ). Zhang et al (2016) also described a single recessive gene cr underlying resistance to CMV.…”

“…A few monogenic, strain-specific resistance loci have been mapped ( Kang et al, 2010 ; Park et al, 2011 ; Min et al, 2014 ). The first single dominance resistance gene, Cmr1 , conferring resistance to CMV Korean and CMV FNY strains, was detected in C. annuum “Bukang.” Cmr1 is in the region on chromosome 2 associated with the ToMV resistance locus Tm-1 in tomato ( Kang et al, 2010 ).…”

“…The single recessive gene cmr2 , resistant to CMV P 1 , has been mapped to marker Affy4 (within 2.3 cM) on chromosome 8 ( Choi et al, 2018 ). Two recessive genes, cmr3E and cmr3L , were located on linkage group 4, associated with the RAPD primer OPAT16 ( Min et al, 2014 ). Zhang et al (2016) mapped a recessive gene, cr , to a linkage group including two SSR markers GI1354 and genSSR3000.…”