Randomly amplified polymorphic DNA markers for a Carica interspecific hybrid

Interspecific hybrid plants of Carica papaya (susceptible to papaya ringspot virus-type P: PRSV-P) and C. cauliflora (resistant to PRSV-P) were created through hybridization followed by embryo rescue. This resulted in single and multiple hybrid embryo types. Both embryo types were variable in size, colour and developmental stages and the hybrid plants produced through embryogenesis had variable phenotypic characteristics Eg. leaf morphology, precocity, stature, stem diameter and flower colour. Molecular markers generated by random amplified polymorphic DNA (RAPD) were developed to mark the genetic hybrids. Seventy-two Operon primers were screened for polymorphism across the DNA of C. papaya and C. cauliflora. A high level of polymorphism (64%) between C. papaya and C. cauliflora was detected. Seventeen of these primers yielded reliable, repeatable and easily scorable polymorphic banding patterns, that were further screened to reveal hybrids. Operon primers OPA-07, OPA-09, OPA-19, OPB-12 and OPC-06 generated RAPD markers that were used to mark the hybrids. All 120 hybrid plants analysed were confirmed genetic hybrids, as they contained at least 1 band from the C. cauliflora male parent. The hybrids were shown to be aneuploid mosaic as revealed by the RAPD markers and cytological data. A very low pollen fertility was also observed for the hybrids. Chromosome doubling by colchicine treatment is used to increase pollen fertility to be used for backcrossing work.