In vitro shoot tip grafting of Carrizo citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.), Rough lemon (Citrus jambhiri) and Flying dragon (Poncirus trifoliata) to produce virus-free planting material in Guyana

In vitro shoot tip grafting (STG) is a method employed for production of virus-free plants. The present investigation was carried out to study the effect of three rootstock on the success of in vitro shoot tip grafting on four different scions. The four shoot-tips that were selected for this study were Valencia (C. sinensis (L.) Osbeck), Cleopatra mandarin (C. reshni Hort. ex. Tan.), ‘Santa Cruz’ Rangpur lime (C. limonia Osbeck) (LCRSTC) and Flying dragon (Poncirus trifoliata). These shoot-tips were grafted onto the three different rootstocks which were Carrizo citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.), Rough lemon (Citrus jambhiri) and Flying dragon (Poncirus trifoliata). The maximum STG success was observed in Carrizo citrange (50%) on 15-20-day old seedlings, followed by Rough lemon (22%) 14-20-day old seedlings and Flying dragon (11%) on 60- 190-day old seedlings. Moreover, pre-treatment of scion and stock with BAP (1.0 mg L^-1) was found to have a high rate of survivability. Additionally, further growth of micrografts was achieved when Murashige and Skoog medium (MS media) was fortified with 1.0 mg L^-1 BAP and 75g L^-1 sucrose which, resulted in maximum (83.3%) successful response in the micrografts. Overall, Cleopatra mandarin and Valencia showed relatively better response in combination with the surface placement method and produced 44.4% and 27.7% successful micrografts, respectively due to the high percent of survivability on Carrizo citrange, followed by Rough lemon. This report is the first report of in vitro Shoot Tip Grafting on citrus species in Guyana.