English abstract
Bread wheat (Triticum aestivum L.) is Oman's most important grain crop. However, its production
in the country is constrained by several challenges including salinity. This study, consisting of two
independent experiments, was conducted to characterize wheat genotypes of Omani origin for salt
tolerance and develop management strategies to improve salt tolerance. In the first experiment,
Omani wheat genotypes were characterized for salinity tolerance on morphological, physiological,
chemical, biochemical, and genetic basis. The genotypic responses to salt stress varied
significantly. Salt stress caused significant reductions in plant growth and carbon assimilation, and
these reductions increased as salinity levels increased. However, salinity increased tissue sodium
and chloride, malondialdehyde contents, leaf proline, and antioxidant enzyme activities. Bread
wheat genotypes SIS-12, Sayreea and Messani Black were better tolerant to salt stress due to higher
accumulation of leaf free proline and activities of antioxidant enzymes, and lower tissue sodium
and chloride levels. A high polymorphism information content ranged from 0.73 to 0.87 for the
microsatellite loci, with an average value of 0.81. In the second experiment, the potential of nano sized chitosan-proline seed priming (nano-priming) and biochar application in improving salt
tolerance in wheat genotypes Messani White and SIS-12 was evaluated. Salt stress caused a
significant reduction in the growth and carbon assimilation in both tested genotypes - more so in
the genotypes Messani White. Application of biochar and nano-priming significantly improved
plant growth and carbon assimilation. However, combined use of nano-priming and biochar was
more effective in improving salt tolerance in tested wheat genotypes than the sole application.
Biochar application instead triggered sodium and chloride but contributed to salt tolerance through
an increase in potassium contents, accumulation of proline and activation of antioxidant defense
system. Nano-priming improved the salt tolerance in tested wheat genotypes through ionic
homeostasis, osmotic adjustment and activation of the antioxidant defence system. In conclusion,
a moderate level of genetic diversity in Omani bread wheat genotypes may be exploited to develop
salt tolerant genotypes. Integrated use of nano-proline and biochar may help improve salt tolerance
in bread wheat.
