Effects of medium conditions on adventitious bud formation in immature mulberry leaves

Immature mulberry leaves isolated from winter buds were cultured on MS medi a(7)) differing in the nitrogen source, sugar(s) or pH, or containing vario us kinds and concentrations of plant hormones, antibiotics or a herbicide. The ratio of the concentration of nitrate ion to that of ammonium ion remar kably affected the frequency of adventitious bud formation (FABF) and ratio s in the ranges of 1:1 and 3:1 were optimum. The most suitable sugars for a dventitious bud formation were sucrose, glucose and fructose among the test ed sugars. The highest FABF was usually observed in the medium containing 1 mu M thidiazuron and the addition of 1 mu M abscisic acid further enhanced FABF. Changes of pH and addition of other plant hormones did not produce b etter results than in the control. Kanamycin, geneticin, hygromycin and bia laphos suppressed adventitious bud formation, showing that the antibiotics and the herbicide may be effective for the selection of transgenic plantlet s of mulberry.