Plant regeneration and transient GUS expression in a range of lavandin (Lavandula x intermedia Emeric ex Loiseleur) cultivars

Five cultivars of lavandin were compared for their ability to regenerate pl antlets in vitro and for their susceptibility to genetic transformation. Bo th processes were shown to be strongly cultivar-dependent. For regeneration , best results were obtained with cultivar '37-70', which gave an average o f 7 shoots from one initial explant after 4 months culture in vitro. The ot her cultivars produced between 0.5 and 3.5 shoots per explant. These differ ences were mostly due to the variable efficiency of the shoot elongation an d rooting steps. An Agrobacterium-mediated transformation system using the beta-glucuronidase and neomycin phosphotransferase II genes was established . The beta-glucuronidase expression was analysed for both leaf explants six days after inoculation and kanamycin-resistant calluses obtained after a s ix-week culture on a selective medium. For each cultivar, kanamycin-resista nt calluses showing a beta-glucuronidase activity were obtained. The transf ormation efficiency ranged from 3% for cultivar 'Certitude' to 89% for cv. '41-70' and 'B-110'. Some kanamycin-resistant calluses were organogenic.