Effect of salinity stress on growth characteristics and quantitative and qualitative traits of different cultivars of canola

Introduction There is an increasing pressure to apply low quality brackish water for irrigation in the arid and semi- arid areas of the world. Consequently, there is a demand to identify the salt tolerant of conventional crops and varieties.   Materials and methods In order to investigate the effect of four salinity levels of irrigation water (including 1.15, 4, 7 and 10 dS.m-1) on phonology, morphology, yield component, yield, oil and water use efficiency of different cultivar of canola (Hyola 4815, 308 and 401 and RGS 003), an experiment was designed as factorial based on complete randomized blocks with 3 replications. Pot experiment was conducted in a semi- controlled environment. In order to avoid toxic effects of some ions, different levels of salinity were prepared with equal weight ratios composition of different salts.   Results and discussion The results of analysis of variance showed that the canola cultivar significantly affected days to flowering, days to maturity, plant height, height of the first secondary branch, height of the first silique, stem diameter, secondary branch number, silique length, silique number per plant, seed number per silique, 1000 seed weight and harvest index. Means comparison test indicated that the RGS cultivar had the highest value in aspect of days to flowering, plant height, height of the first secondary branch, height of the first silique and stem diameter. Given the significant positive correlation (r=0.58**) between the number of days to flowering and days to maturity, cultivars differences from the pattern of change of these traits were similar. The RGS and Hyola 401 cultivars had an average of 2.25 secondary branches less than other cultivars and this difference was significant. Significant negative correlation between number of secondary branches and days to flowering (r=-0.51**) showed that shortening the length of vegetative growth resulted to reduce the number of secondary branches. The RGS and Hyola 4815 cultivars had the highest and lowest stem diameter with 0.629 and 0.381 cm, respectively. Means comparison showed that cultivars differences of silique length and seed number per silique because of positive correlation between them(r=0.60**) were followed the same trend. Highest value of silique length, seed number per silique and 1000 seed weight were found in Hyola 401 cultivar. However, maximum values of silique number per plant, seed yield, biological yield, harvest index and seed water use efficiency have been seen in Hyola 308 cultivar. Regarding to positive correlation between seed yield with number of silique per plant and number of secondary branches on the one hand and remarkable advantage of Hyola 308 compared with other cultivars in aspect of these traits on the other hands, significant superiority of seed yield of Hyola 308 can be attributed to its more ability for production of silique and secondary branch. On the base of analysis of variance results, the salinity effect was significant on days to flowering, plant height, the height of the first secondary branch, height of the first silique and seed number per silique. Increase of salinity from 1.15 up to 10 dS.m-1 led to significant increase of days to flowering (6 days) in all cultivars and significant reduction of days to maturity in all cultivars except RGS. Results of means comparison showed that increase of irrigation water salinity from 7 up to 10 dS.m-1 led to significant reduction of plant height traits. The salinity significantly decreased number of seeds per silique, seed yield, biological yield, harvest index and oil yield. However, reduction of stem diameter and number of silique per plant and increase of 1000 seed weight and number of secondary branches were not significant. Increasing the salinity from 1.15 (control treatment) up to 10 dS.m-1 resulted in significant reduction of seed and oil water use efficiencies about 50 and 25 gr.m-3, respectively. Interaction effect between salinity and cultivar was significant on number of days to maturity, silique length, oil yield and oil water use efficiency that shows responsibility of rapeseed cultivars to different levels of salinity in terms of these traits is different. Accordingly, while increasing salinity resulted reduction in number of days to maturity in different varieties of Hyola, it was increased in the RGS cultivar. Hyola 4815 and 401 cultivars had lowest oil yield and oil water use efficiency in low (1.15 and 4 dS.m-1) and high (7 and 10 dS.m-1) water salinity levels, respectively. However, highest values of oil yield and oil water use efficiency observed in Hyola 308 cultivar in water salinity 4 dS.m-1.   Conclusion Results showed that due to the lack of interaction between salinity and cultivar in respect of many traits, the tolerance of different varieties to salinity was evaluated the same. Also, among the four studied cultivars, the Hyola 308 cultivar is recommended.