ABSTRACT :

Interspecific hybridization between Carica papaya and C. cauliflora hybrids was conducted to intro gress resistance into papaya. Hybrid plants regenerated via embryo rescue need to be screened thoroughly for resistance to papaya ring spot virus - type P (PRSV-P), before they can be introduced into the breeding program. Plants were manually inoculated with PRSV-P in the glasshouse and the reaction assessed 30 days later by back-inoculation to Cucurbita pepo L. plants and a plate trapped antigen-enzyme linked immunosorbent assay (PTA-ELISA). Plants of both parents and interspecific hybrids were also planted in a PRSV-P-infected field and tested 30 days later for PRSV-P by PTA-ELISA. All interspecific hybrid and C. cauliflora plants, manually inoculated or field-planted, did not become infected, whilst C. papaya plants, in both situations were infected by PRSV-P. In addition, the surviving interspecific hybrid and C. cauliflora plants were all negatively indexed, whilst all C. papaya plants were positively indexed for PRSV-P using both the back-inoculation test and PTA-ELISA. Thus, the interspecific hybrids and C. cauliflora plants were confirmed resistant to PRSV-P.