REGENERATION OF TRANSGENIC PEANUT PLANTS FROM STABLY TRANSFORMED EMBRYOGENIC CALLUS

Embryogenic tissue cultures of Arachis hypogaea L. (peanut or groundnu t), have been transformed via microprojectile bombardment. We introduc ed a gene (hph) conferring resistance to the antibiotic hygromycin und er the control of the CaMV 35S promoter. Selection for resistant callu s was initiated 4-5 weeks post-bombardment on medium containing 10-20 mg/l hygromycin. Twelve percent of the bombardments resulted in recove ry of a transgenic cell line. An average of two transgenic embryogenic cell lines was isolated per bombardment experiment over 4-6 months of continuous selection. Each bombardment experiment consisted of 11-19 plates, and each plate contained approximately fourteen 25 mm(2) embry ogenic callus pieces. Thus, nearly 1% of the bombarded callus pieces p roduced a stably transformed cell line. Over 100 plants have been rege nerated collectively from all of the transformed cell lines. The prese nce and integration of foreign DNA in hygromycin-resistant callus line s and regenerated plants has been confirmed by polymerase chain reacti on amplification of a defined portion of the chimeric gene and by Sout hern hybridization analysis. Hygromycin resistance was expressed in le aflets from transformed plants which remained green when cultured on b asal medium containing hygromycin. Leaflets from control, non-transfor med plants turned brown within 3 weeks on the hygromycin-containing me dium.