Evaluation of salt tolerance in two olive rootstocks based on growth characteristics and mathematical analysis of their regression equation with salinity

Salinity is one of the most important limiting factors for crops, because of most agronomic and horticultural crops are sensitive to salinity. On the other hands, considerable lands of the world were affected by salinity and they are increasing day by day. An experiment was conducted with five levels of irrigation water salinity in soilless culture and greenhouse condition to evaluate the effects of salinity on growth parameters of two olive rootstocks.Data showed that salinity decreases significantly some growth parameters such as shoot dry weight, root dry weight, shoot dry weight to root dry weight, and shoot elongation and decreasing amounts of all growth parameters by salinity in Zard rootstock were more than that of Mission. Shoot dry weight, leaf dry weight and root dry weight at 16 dS.m-1 salinity treatments were decreased 80, 80 and 69 percent respectively compared to control. Data also demonstrated that among different growth parameters, leaf aria had the most sensitivity to salinity and leaf relative water content(LRWC) had the lowest sensitivity to salinity. Base on the results, relative leaf aria was decreased 25 percent at 2.3 and 5.0 dS.m-1 salinity in Zard and Mission rootstock, respectively. Salinity status for 25 percent decrease of relative dry weight of these parameters were 2.8, 2.9 and 4.4 dS.m-1 in Zard rootstock and 5.3, 6.1 and 6.9 dS.m-1 in Mission rootstock respectively.Data analysis showed that there were a regression equation among salinity and some growth parameters such as relative leaf aria, leaf number, leaf water content and leaf chlorophyll. Data showed that the slope of regression fit line in Zard rootstock was more negative than Mission rootstock. These results confirmed that some variables such as relative leaf aria, leaf number, leaf water content and leaf chlorophyll content were more sensitive to salinity in Zard rootstock in compare to Mission rootstock.Data also showed that salinity status to for 25 percent decrees of relative leaf aria, leaf number, leaf water content and leaf chlorophyll content in Mission rootstock were 5.06, 5.51, 20.39 and 11.5 and for Zard rootstock were 2.33, 2.81, 15 and 8.61 dS.m-1 respectively. Data also indicated that 25 percent decrease in total relative dry matter were in 7.0 and 3.6 dS.m-1 salinity in Zard and Mission rootstooks, respectively. On the whole, evaluation of plant growth parameters and their sensitivity to salinity indicated that Mission rootstock had more tolerance to salinity and was recommendable to cultivation in salt affected soils.