Abstract

Effects of salinity (NaCl) and the carbon source mannitol (0-200 mM) on micropropagation of pineapple cv. MD2 were analyzed in temporary immersion bioreactors (TIBs). Shoot multiplication rate, shoot cluster fresh weight and levels of aldehydes, chlorophylls, carotenoids and phenolics were determined in the plant material. The content of soluble phenolics in the culture medium was also evaluated. NaCl or mannitol above concentrations of 50 mM decreased pineapple shoot multiplication and fresh weight significantly. Two hundred mM NaCl decreased multiplication rate by 71.5% and cluster fresh weight by 40.0%. NaCl increased 2.4 times the levels of other aldehydes; 1.4 times the soluble phenolics in shoots; and 1.4 times the phenolics excreted to the culture medium. On the other hand, mannitol decreased the multiplication rate and cluster fresh weight by about 60%. Mannitol increased the contents of chlorophyll b 1.4 times and soluble phenolics 2.1 times. Results indicated that pineapple cv. MD2 is more sensitive to NaCl than to mannitol. Multiplication rates indicate that a 50% reduction was obtained with 37.4 mM NaCl and 66.5 mM mannitol. These concentrations can be used to stress shoots during micropropagation in TIBs and screen for/detect somaclonal variants with an increased salinity or drought tolerance.