The Effect of Different Water Potentials on Seed Germination and Growth of some Persian Walnut Populations

In this study, seven walnut populations (Rabor, Hanza, Sardoueih, Dalfard, Bidkhan, Dehbakri, and Baft) were selected from Kerman province and compared for drought stress tolerance. Water potential between 0 and -1.5 MPa was obtained by polyethylene glycol 6000 solutions. Germination percentage, leaf relative water content (LRWC), and growth parameter of seedlings diminished with increasing drought stress, but it varied across the genotypes. The Dehbakri genotype was the most tolerant to osmotic stress. In contrast, Dalfard and Bidkhan were the most sensitive to osmotic stress in which no germination occurred at -1.5 MPa. Additionally, drought treatment increased proline and soluble sugar content in the shoot and root in the tolerant genotypes. These results suggest that the accumulated proline and soluble sugar promote drought stress. Overall, the concentration of phosphorus, potassium, calcium, magnesium, and manganese increased with a reduction in the water potential while nitrogen, copper, zinc, and iron elements dropped with the decrease in water potential. Using cluster analysis, Dehbakri was classified as the most tolerant genotype. Baft, Sardoueih, Rabor, and Hanza were semi-sensitive genotypes; finally Dalfard and Bidkhan were classified as the most sensitive genotypes. For future production of drought tolerant rootstock, Dehbakri genotype is suggested to be used in breeding programs.