Varietal variations in biochemical changes during growth and redifferentiation of rice callus cultures

Calli initiated from 7 rice varieties belonging to 3 subspecies, indica, japonica, and javanica were cultured for 2 and 14 months on the callus maintenance medium, transferred to the plant regeneration medium, and various organ redifferentiation/plant regeneration abilities were examined. Considerable variations especially in the shoot regeneration were observed among the varieties; four varieties [Tadukan (indica), Nipponbare and Sasanishiki (japonica) and Allorio (javanica)] retained the same redifferentiation abilities, while the remaining 3 varieties [Fujisaka 5 (japonica) and Te-tep and Choukoutou (indica)] showed only very much lowered abilities after 14 months. During the redifferentiation/regeneration period, samples were taken at 4-day intervals up to 36 days and peroxidase and acid phosphatase activities were measured. Activities of these enzymes increased after transfer to the regeneration medium. The patterns of the increase, although the same among varieties within the same subspecies, differed markedly between subspecies. Significant correlations between the redifferentiation/regeneration abilities and the activities of the two enzymes were observed.