Evaluation of promising new Tritipyrum grain new grain lines for physiological traits and mineral elements in seedling growth stages under salinity stress conditions

Tritipyrum lines are obtained from a cross between durum wheat and Thinopyrum bessarabicum (2n=2x=EbEb) and its tolerance to salinity has been reported. Tritipyrum (2n=6x=42, AABBEbEb) is the third new man-made grain after triticale and tritordium, and needs further studies until release as a commercial cultivar. Therefore, this study was designed to investigate the effect of salinity stress on the amount of sodium and potassium in roots and leaves, the ratio of potassium to sodium in roots and leaves, the amount of soluble protein, soluble sugar and proline in a number of primary and combined tritipyrum lines.

In this study, 13 promising of primary and combined tritipyrum lines were tested in a factorial experiment based on completely randomized design with 3 replications. The first factor includes salinity levels (0, 80, 160 and 240 mM of sodium chloride salt) and the second factor includes 13 promising of primary and combined tritipyrum lines and 2 bread wheat varieties of Alvand and Qods (tolerant and sensitive to salinity, respectively). Measurement of sodium and potassium elements of leaves and roots was performed one month after salinity stress and the amount of proline, leaf soluble protein and leaf soluble sugars were also measured.

The results showed that with increasing salinity stress, root potassium decreased but root and leaf sodium increased. Levels of proline and soluble sugars also increased with increasing salt concentration. At 240 mM salinity stress, the highest amount of leaf potassium belonged to Ka/b and La(4B/4D)*b lines and the lowest amount of it belonged to Az/b, (Cr/b)(Ka/b)F3 lines and the Qods variety. The highest ratio of leaf potassium to sodium was belonged to (Cr/b)(Ma/b)F3, La(4B/4D)*b and St/b lines and therefore these lines are more tolerant to salinity stress. At 240 mM salinity stress, the highest leaf protein belongs to the Az/b line and the lowest value belongs to the (Cr/b)(Ma/b)F3 line. In both stress and non-stress conditions, the highest genetic variance belonged to leaf protein and the amount of this variance in stress conditions was much higher than non-stress conditions. The environmental variance of root and leaf sodium and leaf potassium traits was higher in salinity stress conditions than in non-stress conditions, which indicates that it will be more difficult to evaluate genotypes for stress traits under stress conditions. Phenotypic variance of root and leaf sodium and leaf potassium as well as leaf protein in salinity stress conditions was higher than non-stress conditions, i.e. the above traits are not suitable for selection. The highest general heritability in normal conditions belonged to proline and in stress conditions belonged to leaf soluble sugar. Under normal conditions, the most significant negative correlation was between root sodium and leaf sodium. There is also a significant positive correlation between leaf protein and soluble sugar. Under stress conditions, there is a significant correlation between leaf sodium and root sodium and also between leaf potassium and proline. There is a significant negative correlation between leaf proline and sodium and the root and leaf potassium to sodium ratio has a significant positive correlation with the amount of proline. The studied genotypes categorized in 3 groups under stress conditions and 4 groups under stress conditions using cluster analysis.

Based on the ratio of potassium to sodium in plant tissues, which is one of the important index for the identification of salinity-tolerant species, we can introduced (Cr/b)(Ma/b)F3 and La(4B/4D)*b and St/b lines as salinity tolerant lines. On the other hand, according to the results, the crossing of genotypes with maximum genetic distances can be used to hybridization and produce more tolerant hybrids in breeding programs.