Development CTV resistant citrus rootstocks using hybridization

Citrus is widely grown throughout tropical and subtropical regions of the world with 117 million tons ofproduction. There are some serious problems affecting citrus production. One of them is Citrus tristeza virus(CTV) that is the most significant viral pathogen of citrus. This disease causes quick decline of trees grafted onsour orange (Citrus aurantium) rootstock. The development of CTV resistant rootstocks has become a priorityobjective of citrus breeding programs. Genetic studies revealed that CTV resistance is controlled by a singledominant gene in Poncirus trifoliata. Regarding resistance to CTV some molecular markers had been identified. Seven of them were cloned and were converted as SCARs. Three of them are SCB 11, SC007, SCTO8. In this studysome citrus rootstocks (‘Volkameriana’, ‘Rough lemon’, ‘Cleopatra’, Citrumelo, ‘Troyer’ and ‘Carrizo’ citranges,‘Taiwanica’, sour orange, Yuzu, ‘Rangpur’ lime, pummelo and Fortunella spp.) and hybrids of P. trifoliata X sourorange were screened with the three markers at Alata Horticultural Research Station. SCT08 marker yieldedtwo bands for ‘Troyer’ and ‘Carrizo’ and one band for P. trifoliata and Citrumelo. On the other hand other citrusrootstocks had sensitive band at 400 bp. Five of P. trifoliata X sour orange hybrids have only one resistance band(homozygous resistant) and 30 of them have two bands (heterozygous resistant). SCB 11, SC007 SCAR markerswere tested at this study. This study showed that although SCB 11, SC007 SCAR markers could be use for CTVresistance. In the next step all materials will be evaluated by biological inoculation of plants for CTV resistance.