INVITRO SELECTION FOR TOLERANCE TO S-(2-AMINOETHYL)-L-CYSTEINE AND OVERPRODUCTION OF LYSINE BY EMBRYOGENIC CALLI AND REGENERATED PLANTS OF PENNISETUM-AMERICANUM (L) SCHUM,K.

S-(2-Aminoethyl)-L-cysteine (AEC) tolerant callus lines were isolated from non-mutagenized embryogenic calli of Pennisetum americanum (L.) K Schum. cv. Gahi 3. Calli, 3-4 months in age, were slected by direct culture on medium containing 0.125, 0.25, 0.5, 1.0, 2.0, 3.0 and 4.0 mM AEC. Tolerant calli were capable of growth on medium supplemented with 0.5-4.0 mM AEC. However, non-tolerant calli were inhibited in the presence of 0.125 and 0.5 mM AEC. AEC-tolerant calli accumulated free lysine at concentrations five times that of the controls as determined by amino acid analysis. Embryoids were formed in the presence of AEC, but plantlets could be regenerated only in the absence of AEC. Plants were regenerated from tolerant calli that had been determined to be stable. Leaf tissue from the regenerated plants analyzed for amino acid content were found to contain seven times as much lysine as the control plants. Calli, initiated from inflorescence tissue of regenerated plants and cultured in the presence of AEC, were tolerant to AEC.