Changes in chromosome complement in long-term pea callus cultures

A prolonged callus culture from pea (Pisum sativum L. var. Kiir) cotyledons subcultured for 7.5 years on Torrey's solid medium was examined cytologically. The initially (and up to 3.5-year cultivation) predominantly diploid pea callus strain changed into triploid. The frequency of aberrant ana- and telophases increased during 5 year cultivation from 9 to 40 per cent and thereafter returned to the initial rate maintaining it at least for one year of subculturing. Some possible mechanisms of chromosomal variation tendencies in vitro are discussed.