Extended Abstract
Introduction and Objective: Salinity is one of the major abiotic stresses and the most limiting factor in agricultural production worldwide, affecting the growth, development and final yield of crops. Due to the fact that rapeseed is one of the most important sources of oilseeds in the world, and its seeds contain more than 40% of oil, and the meal obtained from oil extraction has more than 35% of protein, and currently ranks third among oil crops in the world after soybean and oil palm, it is necessary to know the genotypes that tolerate salinity stress. The development and improvement of rapeseed cultivars with salinity tolerance and acclimation offer promising prospects for improving sustainable production in this area. Therefore, our current study was undertaken to investigate the response of rapeseed genotypes to salinity stress through an analysis of agronomic and biochemical traits.
Material and Methods: In order to investigate the genetic diversity between rapeseed lines in terms of agronomic, morphological and physiological traits in saline soils experimental research was done based on randomized complete block design with 17 autumn rapeseed genotypes in the research farm of East-Azarbaijan Agricultural and Natural Resources Research and Education Center with three replicates. Plant height, number of fertile pods, number of seeds per pod, pod length, pod area, plant growth rate, 1000 seed weight, seed yield, oil content, and oil yield, were measured. To explore relationships between yield, yield components, and morphological traits, as well as to understand the relative importance of traits affecting the yield of the studied genotypes, analysis of variance, comparison of averages, correlation analysis, cluster analysis and biplot was done.
Results: The studied genotypes had statistically significant differences among each other in pod length, pod area, number of fertile pods, number of seeds per pod, plant growth rate, seed oil percentage, plant height, 1000 seed weight, grain yield and oil yield. However, there was no significant difference between the genotypes studied in terms of harvest index and number of actual pods to potential pods. According to the mean comparisons, genotypes 5, 11 and 15 can be introduced as salinity tolerant lines and genotypes 2, 4, 6, 9 and 12 can be considered as salinity sensitive lines. According to other traits, genotype 11 had high pod length, number of fertile pods, oil percentage and oil yield, genotype 5 had high growth rate and oil percentage and genotype 15 had high height and number of fertile pods. According to cluster analysis, the second group contained tolerant genotypes and the third group contained susceptible genotypes. The genotypes in the second group had the highest percentage of positive deviation from the overall mean for grain yield, plant height, harvest index, seed oil percentage, pod length, pod area and number of fertile pods. Based on biplot analysis, it was found that Karaj 8 and 14 genotypes had a strong relationship with number of fertile pods, number of seeds per pod, pod length, pod area and plant growth rate. Based on the obtained results, it was also observed that the traits of plant height, 1000 seed weight, seed yield and oil content were closely correlated with Karaj 5, 7, 11, 10 and 15 genotypes. Based on the results of correlation analysis, the correlation coefficient of seed yield with three traits of plant height, oil percentage and number of fertile pods was positive and significant, among which the correlation coefficient of seed yield with seed oil percentage was the highest (r=0.879). Correlations of number of seeds in pods with pod length (r=0.699), pod area (r=0.555), number of fertile pods (r=0.678) and number of actual pods were positive and significant. Therefore, genotypes characterised by longer and more abundant pods play a crucial role in improving seed quantity, a key component of grain yield in saline environments. Consequently, the size and number of pods per plant serve as indicators of high yield potential under such conditions. Based on the results of the principal component analysis (PCA), it was observed that the first and second components had the highest relative variances, accounting for 44.66% and 31.22% of the total variance, respectively. Together, these two components accounted for 75.88% of the total variance. Factor loadings showed that in the first component, traits such as number of fertile pods, seed yield, oil yield and seed oil content had the highest factor loadings. Similarly, in the second component, plant growth rate had the highest factor load among all the traits studied. Cluster analysis divided the genotypes into four groups and the dendrogram of cluster analysis showed that all the studied genotypes were divided into four separate groups based on all the measured traits.The first groups had three genotypes of Karaj 1, 13 and 16, the fourth group like the first group contained three genotypes which included Karaj 5, 11 and 15 and the third group had five genotypes which included Karaj 3, 7, 8, 10 and 14 while the remaining genotypes were assigned to the second group.
Conclusion: The results of the present study showed that there is acceptable genetic diversity among rapeseed genotypes in terms of evaluated traits in saline lands, which shows the importance of these genetic resources and the possibility of using them to achieve promising and superior genotypes in breeding programs.