CARBOHYDRATES IN ALFALFA SEED DEVELOPED FOR SALT TOLERANCE DURING GERMINATION

Alfalfa (Medicago sativa L.) is an important forage crop in many areas of the world where salinity limits crop productivity. Alfalfa that is salt tolerant during the germination stage has been developed through eight cycles of recurrent selection starting with Mesa-Sirsa. We inve stigated physiological attributes that may have been affected by selec tion, recognizing that understanding the basis of tolerance could faci litate more precise techniques for identifying salt-tolerant plants in breeding programs. Free sugars in seed of Mesa-Sirsa and in Cycle 5 a nd Cycle 8 (C5 and C8) from the selection program were extracted with 95% (v/v) ethanol and the residue hydrolyzed with 4 M H2SO4. All carbo hydrates were quantified by HPLC. Percent galactomannan, glucose, and arabinose in the acid hydrolysate were not significantly different in Mesa-Sirsa, C5, and C8 seeds. Percent stachyose and glucose were not d ifferent in the free sugar extraction of the seed; however, raffinose and sucrose were significantly higher in C8 seed. The increase in thes e free sugars was not sufficient to explain the increased salt toleran ce of the selected populations.