Title : Quantitative assessment of some oilseed response to salinity stress at the early growth stage
Abstract:
In arid and semi-arid areas, salinity stress is one of the most serious global crop production problem. Furthermore, 90% of oil demand of IRAN are supplied through imports. In this regard, it is necessary to investigate the response of some oilseeds to salinity stress to identify salinity tolerant cultivars and achieve optimal yield. In this study, to quantify the response of Nima and Zafar rapeseed cultivars, as well as the Soheil camelina cultivar to salinity stress at the germination stage, an experiment including 17 water salinity levels of 85.0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 dS m-1, each with three replicates was conducted at Tarbiat Modares University in 1398. Germination indicators were calculated using the SeedCalc package of the R software. MATLAB software were used to fit the salinity models of Maas and Hoffman (MH), van Genuchten and Hoffman (HVG), Dirksen and Augustijn (DA) and Homaee et al. (HF) to predict seed germination indices. The salinity tolerance threshold of the final germination percentage index (FGP) for Soheil, Nima and Zafar cultivars is 32, 2, 4 dS m-1, respectively, and the reduction slope for Nima and Zafar cultivars is 1.14 and 1.84 %, respectively. Also, the salinity tolerance threshold of germination rate index (GSI) for Soheil, Nima, and Zafar is equal to 2, 2, and 0.86 dS m-1, respectively, and their reduction slope is equal to 2.4, 2.2 and 1.8 %. In addition to FGP and GSI indices, the salinity tolerance threshold of the seed vigor index for Soheil, Nima, and Zafar cultivars is 12, 4 and 8 dS m-1, and their reduction slopes are equal to 7.7, 1.7, and 3.5, respectively. Based on all three indices of FGP, GSI and seed vigor, Soheil and Nima cultivars are tolerant to salinity, whereas the Zafar cultivar is moderately tolerant. Among the models fitted to FGP, GSI and seed vigor indices, nonlinear models performed better than linear models due to the Sigmoid nature of the curve. Linear MH model in FGP and GSI indices for Zafar cultivar because of trend linearity of the data provided good performance and in GSI and seed vigor indices, HVG and HF models had the best performance.
