EFFECT OF GROWTH-CONDITIONS AND ORIGIN OF TISSUE ON PLOIDY AND MORPHOGENETIC POTENTIAL OF TISSUE-CULTURES OF BEAN (PHASEOLUS-VULGARIS-L)

Callus cultures isolated from various somatic tissues and anther tissue of P. vulgaris seedlings on a defined growth medium contained few diploid cells. The proportion of diploid cells did not alter as cultures lost their ability to form vascular tissue. Meristematic cells of roots initiated after transfer to induction medium were diploid. All cultures lost their morphogenetic potential after 5-7 subcultures except anther callus which formed vascular tissue over a prolonged period of culture on maintenance medium. After 6 subcultures anther callus contained more polyploid cells than somatic cultures. Callus isolated from bean hypocotyl tissue in the presence of coconut milk consisted mainly of diploid cells and retained its morphogenetic potential for a greater number of subcultures than callus grown on defined medium. Transfer of callus isolated on the defined medium to medium containing coconut milk increased the proportion of diploid cells and prevented further loss of morphogenetic potential. An equivalent concentration of cytokinin to that in coconut milk prevented the loss of potential but did not affect the ploidy of the cultures.