Marker-Assisted Hybridisation and Backcrossing between Vasconcellea Species and Carica papaya for PRSV-P Resistance

Abstract

Vasconcellea species are wild relatives of papaya (Carica papaya) and contain genes that would be beneficial if transferred to cultivated papaya. Four Vasconcellea species are resistant to papaya ringspot virus (PRSV-P). Intergeneric hybrids have been made between V. quercifolia and papaya and selections resulting from backcrosses to papaya display high levels of tolerance to PRSV-P but not complete resistance. V. pubescens is immune to PRSV-P but when crossed to papaya produced infertile hybrids. V. parviflora is susceptible to PRSV-P but, when crossed to papaya, produced hybrids with some pollen fertility and is being used as a bridge species between V. pubescens and papaya. Crosses between V. pubescens and V. parviflora have resulted in fertile F1, F2 and F3 populations. Backcrosses to V. parviflora are producing a PRSV-P resistant V. parviflora which will be crossed with papaya. A co-dominant CAPS marker has been developed which is closely linked to PRSV-P resistance in V. pubescens. This marker is being used to facilitate these interspecific and intergeneric hybridisation programs and can be used at the in vitro stage after embryo rescue of wide crosses.