Recovery of Primary Transformants of Valencia-type Peanut Using Agrobacterium tumefaciens¹

Four regenerable seedling explants of peanut cv. New Mexico Valencia A, two different strains of Agrobacterium tumefaciens, and two transformation protocols were used in peanut genetic transformation experiments. The putative transformation-competent cell types were identified by transient expression of the β-glucuronidase (GUS) reporter gene, and were compared to the regeneration-competent cell types identified histologically in the four explant systems. One primary transformant plantlet and two primary transformant shoots were recovered from petiolule-with-blade-attached explants inoculated with Agrobacterium strain CKS (A208:pTi37ASE X pEMZ) following a long cocultivation time on the regeneration medium and using low selection pressure for kanamycin resistance. The leaves of the primary transformants expressed nopaline accumulation used as a marker gene, and the engineered 35S-15kD zein protein coding sequence as determined by western blot. The results from these experiments may be useful for developing reliable methods of genetic transformation for valencia-type peanut.