Gene for PRSV-P Resistance in Vasconcella Species and Development of PRSV-P Resistant Papaya via Intergeneric Hybridisation

Abstract

We report the first successful transfer of PRSV-P resistance from a Vasconcellea species to papaya (Carica papaya L.). There have been numerous attempts over the past 50 years to transfer Papaya ringspot virus (PRSV-P) resistance from Vasconcellea species to papaya. We have made intergeneric hybrids between V. quercifolia and papaya and selections resulting from four backcrosses to papaya display resistance to PRSV-P. Vasconcellea pubescens has been crossed with the PRSV-P susceptible species, V. parviflora, and fertile F1, F2 and F3 populations were produced. Resistant F3 individuals are being backcrossed to a BC4 generation to produce a PRSV-P resistant V. parviflora. When V. parviflora was crossed to papaya, hybrids with some pollen fertility were produced. It is therefore being used as a bridge species between V. pubescens and papaya. A co-dominant CAPS marker has been developed which is closely linked to PRSV-P resistance in V. pubescens and is being used at the in vitro stage following embryo rescue to facilitate selection of plants having the desired alleles of the resistant gene. A kinase gene linked to virus resistance is being sequenced. This gene is being transferred to papaya and resultant transgenic plants will be compared to intergeneric hybrids and backcross generations for reaction to PRSV-P.