XVI International Botanical Congess

The Cuban economy is strongly dependant on sugar. After the discovery of Acetobacter diazotrophicus in sugarcane by Döbereiner, we investigated the role of this bacterium in our sugarcane agronomy. A. diazotrophicus is present in the outstanding Cuban sugarcane varieties, in intercellular spaces (mainly in the stalk., but also in the roots). NH3 stimulates its N-fixing capacity. Its sucrose hydrolysing activity is directly related to its N-fixation rate. Superoxide dismutase and catalase protect the bacteria from the high [O2] under which it fixes N. Heat treament of sugarcane sets (to control Ratoon Stunting disease) reduces the population of the bacteria immediately, but they partly recover and colonize the new plant. The mealybug Saccharococcus sacchari ingests A. diazotrophius and may spread it and other endophytic microorganisms in the sugarcane crops.