Identification of salinity stress tolerant wheat genotypes using evaluation of enzymatic defense system changes and stress tolerance indices

Salinity is one of the major abiotic stresses that has been significantly affecting the plant growth and yield The continuous increase in salinity in arable land due to poor cultivation practices and climate change have devastating global effects, and it is estimated that about 50% of arable land will be lost by the middle of the 21st century. To date, about 1,125 million hectares of agricultural lands have already been seriously affected by salinity, thus it is considered a serious threat to agriculture. Salt stress also leads to increasing the level of ROS which results in oxidative stress, which in turn affects the plants both at cellular and metabolic levels . The plants overcome the oxidative damage through activation of antioxidants through enzymatic and non-enzymatic mechanisms. Moreover, the ROS, such as superoxide radicals ( O−2O2− ), hydrogen peroxide (H2O2), and small amounts of transition metals, also increases the concentration of OH−. Therefore, plants carry out detoxification to avoid the oxidative damage where these antioxidant enzymes play an important role. A study reported that the antioxidant enzymes positively correlate with the plant tolerance in drought and salt stress. Moreover, the higher antioxidant activities can help improving death in plants. Assessing the tolerance of crops to environmental stresses is an important factor in selecting them for cultivation in different conditions.

 In this regard evaluation and identification of wheat genotypes tolerant to salinity stress using stress tolerance indices and changes in some biochemical parameters, Experimental In completely randomized block design, with repeated three times. Factors included salinity at three levels (zero (control), 9 dS and 12 dS) and 20 genotypes of native Iranian wheat. The traits measured in this design include stress tolerance indices, protein, proline, lipoxygenase (LOX), polyethylene (TBARM), chlorophyll and carotenoids.

The results of this experiment showed that with increasing salinity stress, the amount of lipoxygenase, TBARM and carotenoids increased in all genotypes, but with increasing salinity level from 9 to 12 ds had a decreasing trend in some genotypes, however, in some genotypes, the salinity level increased with increasing salinity. Also, with increasing salinity stress, the amount of protein and proline concentration in a number of genotypes to a salinity level of 9 dS increased, but some genotypes showed a significant decrease with increasing salinity from 9 to 12 dS. Correlation analysis between indices and mean yield under normal and salinity conditions showed that all four indices are suitable for screening genotypes. Due to these indices and high yield in both environments as well as the results of biochemical properties evaluation, the best salinity tolerant genotypes were G2, G11, G86, G109, G209 and G151 genotypes.

The differences between the studied genotypes in terms of the studied traits indicate the diversity between them. The results showed that genotypes of had higher relative resistance to salinity stress than other genotypes and also the results of this study showed that the highest yield under normal conditions and salinity stress and also belong to these genotypes. High levels of proline and protein, photosynthetic capacity and LOX enzyme and low fat peroxidation also confirm this claim. Reduction malondialdehyde degradation biomarker reduced the damaging effects of oxidative stress due to salinity stress in these genotypesAlthough LOX levels were high in these genotypes, they still had good stability in salinity conditions, indicating the flexibility of these genotypes to salinity stress.Based on the obtained results and the protective role that genotypes had against salinity stress, it is speculated that these genotypes have an inherently high capacity to purify and eliminate reactive oxygen species under environmental stresses.