The effect of salt stress on morphological traits and electrophoresis pattern of proteins in recombinant inbred lines population of oilseed sunflower derived from PAC2 × RHA266 cross

Salinity is one of the main abiotic stresses, especially in arid and semi-arid conditions, which affects plant growth and thereby reduces seed yield.

In the first part of this study, the morphological changes in 98 recombinant inbred lines population of oilseed sunflower derived from the cross of PAC2 × RHA266 were investigated in a complete block design with 3 replications under normal and 6 dS/m of salinity stress conditions. In both conditions, after flowering stage the characteristics including, grain yield per plant, 100 seeds weight, leaf number, stem diameter, plant height, capitol diameter, leaf length, leaf width, petiole length, capitol dried weight, date to flowering were measured. The relationship between grain yield and other morphological characteristics were investigated by simple correlation and stepwise regression analyses. Cluster analysis was used for grouping the genotypes based on all studied morphological characteristics in each one of normal and salinity conditions. Based on the results of the first part of work, two salt tolerant and sensitive lines (respectively C86 and C64 lines) were selected and planted at different salinity levels (0, 2, 4, 6 and 8 dS/m) conditions and their protein electrophoresis patterns were investigated using SDS-PAGE.

Based on the results of analysis of variance, salinity × genotype interaction effect was significant on all studied traits except for plant height, which indicated that the reaction of lines was different depending on different environmental conditions. Comparison of mean of lines in normal and salt stressed conditions indicated that the average of lines under salinity stress conditions decreased compared to normal one. However, the percentage of reduction is different depending on the traits. Heritability of traits varied between 0.07 for width of leaf to 0.50 for leaf number and day to flowering in normal conditions and in salinity stress conditions it varied between 0.09 for petiole length to 0.48 for weight 100 seeds and day to flowering. Based on stepwise regression analysis, the head diameter and 100 seeds weight were entered in the model and explained some part of yield variation in both salinity and normal conditions. So, selecting for these traits will improve grain yield in both conditions. In grouping of lines by using the minimum variance method (Ward method), all genotypes were grouped in 3 clusters in each of the environmental conditions. Under normal conditions, 49, 29 and 12 genotypes were grouped in the first, second and third clusters, respectively, and under salinity stress conditions, 42, 37 and 14 genotypes were placed in the corresponding groups. Based on the results of molecular experiment, different electrophoretic patterns for C86 and C64 lines were observed at different levels of salt stress, indicating a different reaction of lines to salt stress.

The highest coefficient of phenotypic variations was observed for grain yield, petiole length, leaf width, 100 seeds weight and head dried weight in both normal and salinity stress conditions which indicated their determinant roles in the development of phenotypic variation. In this study, traits such as capitul diameter and 100 seed weight due to high genetic variation, positive correlation and high direct effect on grain yield and moderate heritability, are suggested as desirable traits for selection of promising genotypes. In the second part of the study, based on the results, different electrophoretic patterns for C86 and C64 lines were observed at different levels of salt stress, indicating a different response of the genotypes to salinity stress.