INFLUENCE OF AUXIN TYPE AND CONCENTRATION ON PEANUT SOMATIC EMBRYOGENESIS

Somatic embryogenesis in peanut (Arachis hypogaea L.) using immature c otyledonary explants was induced on a wide range of 2,4-dichlorophenox yacetic acid (2,4-D) (5 to 60 mg l(-1)) and naphthaleneacetic acid (NA A) (20 to 50 mg l(-1)) levels. Percent embryogenesis ranged from 31 to 94%. As auxin level increased in induction medium, percent embryogene sis decreased and was associated with browning of explants. However, w ith higher 2,4-D induction levels (40 mg l(-1) and over), embryogenic explants had dense masses of embryogenic areas and repetitive embryoge nesis was enhanced. Higher auxin concentrations during induction decre ased precocious germination of embryos, but had no marked effect on so matic embryo morphology. The use of 2,4-D compared to NAA in the induc tion medium resulted in greater per cent embryogenesis and mean number of embryos. Embryos induced on NAA were harder, less pliant, and less succulent; cultures exhibited more extensive root development and non embryogenic callus proliferation.