MEDIUM AND GENOTYPE FACTORS INFLUENCING SHOOT REGENERATION FROM COTYLEDONARY EXPLANTS OF CHINESE-CABBAGE (BRASSICA-CAMPESTRIS L SSP PEKINENSIS)

Medium conditions for reliable shoot regeneration from cotyledonary ex plants of Chinese cabbage were examined. Maximum shoot regeneration wa s obtained in the presence of 5 mg/l BA and 0.5 mg/l NAA. Shoot induct ion was further improved by the addition of AgNO3 as well as higher co ncentrations (1.2-1.6%) of agar in the regeneration medium. When 123 g enotypes were tested, a large variation in regeneration frequency was observed, ranging from 95% to 0%. Shoot regeneration frequency was not related to origin and days to maturity of the genotypes. Ethylene pro duction from cultured explants seemed to play an important role in sho ot regeneration. Explants of highly responsive genotypes or if culture d on the medium solidified with a higher concentration of agar general ly showed low levels of ethylene production. However, AgNO3, which als o enhanced shoot induction, resulted in an increase in ethylene produc tion. The possible interaction between ethylene and shoot regeneration is discussed.