PLANT-REGENERATION AND MICROPROJECTILE-MEDIATED GENE-TRANSFER IN EMBRYONIC LEAFLETS OF PEANUT (ARACHIS-HYPOGAEA L)

Excised leaflets from mature embryos of peanut cultivars Rebut, Gajah, McCubbin and NC-7 produced multiple shoot primordia via organogenesis on Murashige and Skoog medium supplemented with 3 mg L(-1) BAP and 1 mg L(-1) NAA. Plants were regenerated by elongation of shoot primordia on transfer to MS medium supplemented with 5 mg L(-1) BAP. The regene ration frequency of five plants per embryonic leaflet was 10-40-fold h igher than previously reported from seedling leaflets. Microprojectile bombardment parameters were optimised for high transient expression r ates of the beta-glucuronidase (uidA or gus) reporter gene in peanut e mbryos (> 2000 cells per bombardment) and ih excised embryonic leaflet s (> 1200 cells per bombardment). The firefly luciferase reporter gene (luc) allowed repeated non-toxic assays, revealing the transition fro m hundreds of transiently expressing cells soon after bombardment, to a few stably expressing regions in callus grown without selection for 8 weeks after bombardment of embryonic leaflets.