Physiological and molecular characterization of Kenyan barley (Hordeum vulgare L.) seedlings for salinity and drought tolerance

Genotype variation in selected Kenyan barley breeding lines was determined by differential profiles of seed hordein proteins using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Consequently, a phylogenetic relationship derived from unweighted pair group method with arithmetic mean Jaccard clustering matrix was generated based on absence or presence of hordein bands. In parallel, physiological and molecular responses to abiotic stresses were evaluated in seedlings. For physiological assays seedlings were exposed to 0, 300, 600 mM NaCl. Variation in physiological parameters including ionic conductance, lipid peroxidation, chlorophyll content, accumulation of proline, glycine betaine, sucrose was determined. Response to abiotic stress was found to be genotype dependent and varied with the stress magnitude. A low ionic conductance, lipid peroxidation and increased proline, sucrose, GB, chlorophyll were associated with stress tolerance. The lines Nguzo, MN-24 and MN-8 were tolerant while Karne, and Sabini were susceptible to abiotic stress. Transcript analysis of selected members of the dehydrin (Dhn) superfamily (LEA II) genes in root and shoot tissue were evaluated. Expression of Dhn genes was found to be genotype dependent, tissue specific and was affected by type and duration of stress. Dehydrin Dhn1 and Dhn9 genes were exclusively dehydration responsive while Dhn3, Dhn4 and Dhn7 were induced by both dehydration and increased salt treatments. Immunoblot analysis using polyclonal anti-sera detecting the K segment consensus peptide TGEKKGIMDKIKEKLPGQH showed a direct correlation between transcript level and accumulation of corresponding Dhn proteins in response to stress. These screening assays may be potential selection markers to aid rapid screening in breeding programs.