Obtaining viroïd-free ‘Nour’ clementine by shoot tip micrografting

Abstract: Aiming to produce nursery certified trees of Clementine “Nour”, 18 trees wereselected from Kabbage citrus orchards. All those were infected Citrus Exocortis Viroid d(CEVd) and Citrus Cachexia Viroid (CCaV). In order to clean the candidate trees fromviroids infection, we used Shoot Tip Grafting technique (STG) by in vitro micrografting it onCirtange carrizo rootstock cultured in Murashige and Skoog medium. The success rateobtained was about 20%. The successfully micrografted plantlets were double grafted onCitrus macrophylla in the greenhouse. 7 to 9 months later, the plants were biologicallyindexed. Screening by RT-PCR revealed that 16/26 (61%) plants obtained by STG areCEVd-free and 25/26 CCaV-free. Thus, STG technique abled us to clean up the Clementinevariety "Nour" from both viroids CEVd and CCaV. These viroids appear to infect most treesof this variety in Morocco.