Lime Bush (<i>Citrus glauca</i>) hybrids resistant to CTV

The potential contribution of endemic Australian species to conventional citriculture has long been recognised,but nothing of commercial value has ever emerged. Rootstock experiments in Queensland, Australia havedemonstrated that severe CTV reaction is their major limitation, totally masking the expression of useful traitsthese species are known to possess. In the case of Citrus glauca, the extremely slow growth of seedlings andcuttings during the nursery phase further prevents commercial application. A breeding program commencedin 2002 to address these limitations and has already developed 2nd generation hybrids of C. glauca. Obstaclesencountered by previous breeders have been overcome by using Citrus wakonai as a bridging species, resultingin F1s that flower within two years, and readily hybridise with Poncirus trifoliata. F2 populations (85 hybrids)have been free of delayed lethality, segregate ~50:50 for CTV resistance, readily propagate from cuttings, anddisplay vigour comparable with conventional citrus rootstocks. Cuttings from CTV resistant F2 hybrids will bedeployed as rootstocks in field experiments in 2013.