GENOTYPE-DEPENDENT RESPONSE OF SPINACH CULTIVARS TO INVITRO CALLUS INDUCTION AND PLANT-REGENERATION

Callus was induced from leaf explants of four spinach (Spinacia oleracea L.) cultivars on Murashige-Skoog (MS) medium supplemented with 2 mg 1-1 6-(furfurylamino)purine (kinetin) and 0.1, 0.5 or 1 mg 1-1 2,4-dichlorophenoxyacetic acid (2,4-D) either in darkness or exposed to light (50-mu-E m-2 s-1). Callus production was cultivar dependent. Maximum callus proliferation was obtained with 0.5 mg 1-1 2,4-D, which also gave rise to the highest percentage of shoot formation. Callus induced in darkness exhibited higher regeneration capacity than callus induced in the light. Regeneration capacity of the callus varied among cultivars and was enhanced by the addition of ascorbic acid. Gibberellic acid was required for shoot regeneration. Complete plants were obtained by inducing the shoots to root with 1 mg 1-1 indole butyric acid (IBA).