Original Articles
Kaouther Ben Mahmoud, Asma Naj
Abstract
In vitro somatic embryogenesis from citrus style and stigma culture is reported to be highly effective in the elimination of the main virus and virus-like diseases. This method was applied for the regeneration and sanitation of the Tunisian sweet orange (Citrus sinenesis L.), var “Half-blood” Maltese, which were infected with Citrus dwarfing viroid (CDVd) and Citrus bark cracking viroid (CBCVd). For this purpose, style/stigma explants were excised from unopened flowers and cultured in vitro on MS medium containing 0, 6.65 or 13.3 μM BAP to induce somatic embryogenesis. No reaction was observed in explants cultured on BAP-free medium. Embryogenic frequency was relatively high in presence of 13.3 μM BAP. Unfortunately, many cases of teratological forms affecting embryos ontogeny were scored during their maturation and hampered their conversion into plantlets. Even though the high frequency of those abnormalities, we succeeded to obtain well developed shoots after transfer of normal embryos on growth regulator-free MS medium. These shoots were then grafted on Troyer citrange rootstock and acclimatized in greenhouse. One year later, RT-PCR carried out on growing grafted plants revealed that they were free of viroids CBCVd and CDVd identified in the source material.