Field evaluation of tolerance to salinity stress in Iranian hexaploid wheat landrace accessions

The responses of 400 Iranian tetraploid and hexaploid landrace wheat accessions to variation in soil salinity were investigated at a field site in the San Joaquin Valley of California, U.S.A. The salinity treatments were represented by soil conductivity values (EC _e,) of 1.0 (control), 5.0, and 8.0 dS m^-1 and were maintained by irrigation with water of similar or slighly higher conductivity. A subset of 200 hexaploid accessions was analyzed from the first year of study. For the second year, 77 accessions were selected as having high, low, or random salinity tolerance based on the Fischer-Mauer stress index (S) estimated in the first year. In both years the accessions and three check varieties were evaluated in hill-plots. The interyear correlations for S were very low in contrast to grain yield whereas the correlations at the same salinity level between years were significant: 0.42, 0.46, and 0.44, respectively, for control, intermediate, and high salinity. High grain yield under salinity stress appeared to be a better selection criterion for salinity tolerance than biomass yield, harvest index, or S. Analysis of accessions from 12 Iranian provinces from which five or more accessions originated gave evidence for geographic differentiation for characters related to salinity tolerance. Several accessions, differing in geographical origin within Iran, were shown to be consistently high ranking for grain yield in the control and two salinity treatments.