Determination of salt tolerance threshold in five bread wheat (Titicum aestivum L.) cultivars

The important response of plant to saline condition is a general reduction in phytomass. With increasing in salt concentration at the plant root zone, both the crop growth rate and finally yield progressively decrease. However there are widely differences among different crop species based on salinity tolerance. To determine salt tolerance threshold of wheat, a field experiment arranged as spilt plot based on RCBD was counducted with three replication during 2001-2003. Experimental treatments were irrigation with saline water (2, 5, 8, 11, 14 and 20 ds.m-1) and wheat cultivars namely, Kavir, Roshan, Marvdasht, Mahoti and Qods. Results showed that salinity affected grain yield, significantly. Grain yield of wheat cultivars were significantly different regardless of salinity. Maximum grain yield for all cultivars was obtained with application of low saline water (2 ds.m-1). In general, Kavir produced more grain yield than other cultivars for all salinity levels. Salinity stress also affected biological yield significantly. Such that straw yield was reduced with increasing salinity level. The minimum straw yield was obtained at highest salinity level. Roshan and Marvdasht produced highest and lowest straw, respectively. Salt tolerance threshold for Kavir, Roshan, Mahoti, Marvdasht and Qods was 5.00, 4.58, 3.34, 5.67 and 5.92 dS.m-1, respectively. With every increase in salinity level above the salt tolerance threshold, grain yield for Kavir, Roshan, Mahoti, Marvdasht and Qods was reduced by 4.54, 4.07, 4.48, 5.48 and 4.48 percent, respectively. Among different varieties only Kavir and Marvdasht showed a linear relationship between relative grain yield and average root zone salinity of saturated extract. Based on Ussl rating, these cultivars are moderately tolerance.