Plant production in pea (Pisum sativum L. cvs. Puget and Upton) from long-term callus with superficial meristems

Vigorously growing calluses were obtained in Pisum sativum L. cvs. Puget and Upton (but not in cvs. Maro, Melton and Vedette) which have continuously regenerated shoots, over a period of nearly 3 years. The calluses were induced on the bases of plumules, excised from germinated seed, cultured on Murashige and Skoog (MS) medium supplemented with 1 mg 1⁻¹ 6-benzylaminopurine (BAP) and 4 and 8 mg 1⁻¹ indole-butyric acid (IBA). Shoot regeneration took place 2–4 weeks after transfer to the same medium with IBA reduced to 0.25 mg 1⁻¹ and has continued while the callus has been regularly subcultured to fresh media. Regenerated shoots could be propagated as shoot cultures and rooted on medium containing half-strength MS salts, 1.5% sucrose and 2 mg 1⁻¹ indole-3-acetic acid (IAA). Plants regenerated during the first year of callus growth were diploid and mostly morphologically normal. Plants regenerated after 2 years show variable morphology as shoot cultures and are more difficult to root.