Assessment of yield and yield components of doubled-haploid lines of rapeseed under drought stress

Introduction Rapeseed (Brassica napus) as one of the most important oilseed crops is of great significance due to high amounts of unsaturated fatty acids and low amounts of saturated fatty acids. Among environmental stresses, drought stress is one of the most important factors limiting the growth and yield of crops, which reduces the yield and yield components. However, the yield trait is controlled by several genes, other traits such as yield components can be used to improve drought stress tolerance. Introduction of drought resistant cultivars and stress management strategies are required considering the cultivation of rapeseed cultivars in many areas of Iran dealing with water shortages. Accordingly, several rapeseed doubled haploid lines were evaluated in two conditions of non-stress and water stress through this study. Materials and methods A research was conducted at Ramin University of Agriculture and Natural Resources in Khuzestan under two water conditions (normal irrigation, post-flowering irrigation stop) in the form of augmented design with three control (Hyola 401, Hyola 420, and RGS003) in six replications during the period of 2014-2015 crop year in order to evaluate yield and yield components of 99 rapeseed doubled haploid lines. Under non-stress conditions, irrigation was performed when 50% of soil water was drained from field capacity, but for stress conditions, irrigation was performed when 70% of soil water was reduced from field capacity. To calculate the number of siliques per plant and the number of seeds per silique, 15 plants were selected from each line and the average were recorded for each treatment. Plants from each plot were dried in an oven at 70 °C for 72 h after drying outside. A seed counter device was then used to calculate 1000-seed weight. So that 1000 seeds were counted from each line and then weighed with a sensitive scale balance. Total seeds collected from each plot were weighed after separating seeds from straw to calculate the grain yield. Finally, yield was calculated per hectare using the proportion. Statistical analysis and computation of the results were performed using SAS and SPSS software. Mean comparison was conducted by using LSD method at 0.05 probability level. Results and discussion The results of analysis of variance showed that there are significant differences between the genotypes for number of siliques per plant, number of seeds per silique and grain yield in both environments. The results of this study showed that there is a great variety of rapeseed doubled haploid lines in terms of yield and yield components, which can be used to improve the rapeseed yield. According to the results of stepwise regression in non-stress conditions, it is possible to use the number of siliques per plant as a criterion for selection and improvement of superior lines, but in conditions under stress, the 1000-seed weight should be considered as a criterion of selection. Lines 87, 7, 53, 23 and control Hyola 401 in non-stress conditions and lines 53 and 87, 84 had the highest yield in stress conditions. Based on sensitivity and tolerance indices, G53, G87, and G84 showed highest level of STI and lowest level of STI, therefore, these genotypes were found to be drought tolerant. Conclusions Lines 87, 7, 53, 84, and control Hyola 401 could be used in future plant breeding programs. As well as, lines 85 and 53 showed the least yield loss among lines with high yield under drought stress conditions and were introduced as adaptable lines with high yield under stress conditions.