Ethylene inhibitors enhance in vitro root formation from apple shoot cultures.

Effects of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and three ethylene inhibitors, AgNO3, aminoethoxyvinyglycine (AVG) and CoCl2, on root formation were tested in vitro using shoot cultures of the apple (Malus×domestica Borkh.) cultivar Royal Gala. ACC inhibited root formation by delaying root emergence and increasing callus formation at the bases of shoots. In contrast, ethylene inhibitors promoted root formation. Both AgNO3 and AVG at the appropriate concentrations increased the percentage of shoots producing roots and reduced callus formation at the base of these shoots. AgNO3 stimulated root emergence and enhanced root growth, while AVG increased the number of roots per shoot. CoCl2 slightly increased root number and rooting efficiency. These promotive effects may result from a reduction in ethylene concentration or inhibition of ethylene action. The results found in this study may be used to improve the rooting efficiency of other apple cultivars and rootstocks, and possibly of other plant species.