Does the routine heat treatment of sugarcane stem pieces for xylem pathogen control affect the nitrogenase activity of an N-2-fixing endophyte in thecane?

In sugarcane propagation the sett pieces are routinely heated at 50 degrees C before planting to control the xylem pathogen Leifsonia xyli ssp. xyli. T o determine whether this treatment also affects the diazotrophic endophyte, Gluconacetobacter diazotrophicus, found in the intercellular solution of c ane parenchyma, cultures of this bacterium were similarly heated. The nitro genase activity of the heated cultures was monitored by measurement of hydr ogen evolution. Activity was destroyed in cultures heated directly at 45 or 50 degreesC for 2 h. In contrast, when sett pieces were first heated for 2 h at 50 degreesC, G. diazotrophicus could still be isolated from the inter cellular fluid, and these cultures showed considerable nitrogenase activity . There was no difference in leaf nitrogen content of plants grown in nitro gen-poor soil from setts either heated or unheated. It is concluded that th e routine heat treatment of sugarcane setts for pathogen control does not t otally destroy the nitrogenase activity of the diazotrophic endophyte G. di azotrophicus.