Comparison of salinity response in tolerant wheat cultivars with introduced cultivars for non-saline condition

Salinity stress is a major constraint inhibiting yield of crops throughout the world. Salinity tolerance in crops responded to salinity stress by three main mechanism including osmotic tolerance, ion exclusion and tissue tolerance.
In order to study of salinity response of introduced salinity tolerant wheat cultivars and comparison of them with introduced wheat cultivars for non-saline condition, this experiment arranged in three steps of germination, greenhouse(one year) and farm( two years) during 2012-2014. In farm experiment, treatment includes salinity tolerant cultivars of Akbari, Sistan, Arg, Ofogh and Roshan and introduced cultivars for non-saline condition namely Morvarid, KohDasht and Falat. This cultivars cultured in two stations of Salinity research farm(Agh-Ghala) and Gorgan station(as non-saline condition) in randomized complete block design with four replications. In greenhouse experiment, all of the cultivars planted in pots with sandy medium and Hoagland solution. Salinity treatments were control condition and 15dS.m-1. Relative growth rate measured daily for seven days after salt exposure and then measured with two days interval for two weeks. The sodium content of leaves, the leaf area and total dry matter in all of the pots, measured three weeks after salt exposure. Additional pots for cultivars of Falat, KohDasht and Ofogh prepared and treated with salinities of 2, 7.5 and 15dS.m-1 in three replications. These pots continued until end of the season in order to determination of salinity threshold based on the grain yield. Also the germination of the cultivars measured at salinities of 0 until 30dS.m-1 with 5 unit intervals in three replications to calculate salinity threshold in germination stage.
Based on the results, salinity caused two phase growth reduction of osmotic and ionic, so that the osmotic effect influenced more than ionic effect. In the first week after salt exposure, the same dry matter reduction observed in cultivars, but reducing in leaf area starts immediately after salt exposure. The Sistan cultivar considered as osmotic tolerant and Falat as sensitive cultivar based on the reduction of relative growth rate in the first week after salt exposure. In the next two weeks of experiment more reduction occurred in growth rate in saline condition. This reduction attributed to accumulation of sodium ions and ionic effect phase of salinity stress. Based on the two linear model of response of crops to salinity, the cultivars of Falat, KohDasht and Ofogh had the threshold of 6.06, 5.27 and 4.00 dS.m-1 respectively. Based on the sigmoidal model these cultivars produced 50 percent relative yield in salinities of 11.86, 11.56 and 13.38dS.m-1 respectively.
At all pluralization of results showed that, the salt tolerance cultivars produced higher yields only in native climate condition. When they cultured in different climatic condition with salinity stress, they can’t produce higher yields and not shown salinity tolerance qualifications by effectiveness.