GERMINATION INHIBITION OF ALFALFA BY 2-COMPONENT SALT MIXTURES

Soil and water salinity can severely constrain agricultural production by reducing plant stands and growth. Breeders have used germination i n saline (NaCl) media to screen plant germplasm for salt tolerance. Ho wever, salt tolerance during germination in NaCl may not adequately de scribe the ability of seeds to germinate in mixtures of salts. Natural ly occurring combinations of salts may be more or less inhibitory than the individual salts alone. The objective of this research was to qua ntify the effects of individual as well as two-component mixtures of v arious salts and ions on the seed germination of alfalfa (Medicago sat iva L.). Seeds of the alfalfa cultivars Condor and Rambler were germin ated in petri plates in a darkened growth chamber maintained at 25-deg rees-C and exposed to biologically equivalent concentrations of one- a nd two-salt solutions of NaCl, Na2SO4, KCl, KSO4, MgCl2, and MgSO4. Sp ecific interaction effects of the salts in two-salt combinations were detected; however, as indicated by simple correlations, germination wa s affected more by concentration of Na+ than any other single variable . When all independent variables were considered, concentrations of Cl - and Mg2+ were more important than Na+ and the other ions, choice of cultivar, or the osmotic tension and pH of the solutions. While maximu m genetic gain in salt tolerance during germination of alfalfa seeds m ay only be achieved by selection in solutions containing more than one salt, selection in NaCl solutions may account for most of the potenti al gain.