ETHYLENE RESPONSIVENESS OF SOYBEAN CULTIVARS CHARACTERIZED BY LEAF SENESCENCE, CHITINASE INDUCTION AND NODULATION

A total of 161 cultivars of soybean (Glycine max L. Merr.) were tested for their responsiveness to ethylene treatments, using senescence of the primary leaves and the induction of chitinase activity in the root s as response markers. Cultivar ''Gong jiao 6308-1'' showed rapid chlo rosis and the highest chitinase induction upon treatments with ethylen e. The inducibility of chitinase by ethylene increased with increasing age of the plant. In addition, it was found that upon repeated ethyle ne treatments nodule formation of cultivar ''Gong jiao 6308-1'' mas co mpletely blocked in the lower part of the root system when inoculated with Bradyrhizobium japonicum. In several other cultivars, e.g. in ''B ai tie jia qing'', ethylene treatments did not induce leaf senescence or induction of chitinase activity. Cultivar ''Bai tie jia qing'' also showed completely normal nodulation even after repeated ethylene trea tments. These results demonstrate that different soybean cultivars sho w a wide variation and strongly differ in their ethylene responsivenes s.