SALINITY RESISTANCE, WATER RELATIONS, AND SALT CONTENT OF CRESTED AND TALL WHEATGRASS ACCESSIONS

Salinity is a significant factor in reducing stand establishment and productivity of grasses on certain rangeland sites. Research was undertaken to identify crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] accessions potentially useful in breeding salt-resistant populations and to determine physiological factors associated with the superior salinity resistance of tall wheatgrass [Thinopyrum ponticum (Podp.) Barkw. & Dewey] compared to crested wheatgrass. Forage production under saline (irrigation with -0.6 MPa NaCl solution) and nonsaline conditions was examined in plants grown in sand culture. Consistent differences in forage salinity resistance (forage dry wt. of salinity stressed plants/forage dry wt. of unstressed plants) were not detected, but crested wheatgrass accessions were identified with both high salinity resistance at germination and high forage production under saline and nonsaline conditions. High forage-producing crested wheatgrass accessions under salinity stress showed certain physiological responses similar to salt-resistant tall wheatgrass. Tall wheatgrass and high producing crested wheatgrass maintained average leaf turgor of 1.0 MPa over a range of NaCl irrigation solutions from 0 to -1.8 MPa, but turgor of low-producing crested wheatgrass was reduced by -1.2 and -1.8 MPa solutions. In -0.6 MPa solutions, tall wheatgrass and high forage-producing crested wheatgrass accessions had higher concentrations of K, lower Na, and lower Na/K ratios in leaves than low-producing crested wheatgrass. Concentrations of K, Na, and Cl in root tissue did not differ in crested wheatgrass. Tall wheatgrass, however, had consistently higher root K, Na, Cl, and lower Na/K ratios than crested wheatgrass. The results suggest that high forage production under saline conditions was related to turgor maintenance, lower Na/K ratios, and mechanisms for partial exclusion of Na in leaves.