Mineral Composition of Some Walnut Cultivars (Juglans regia L.) for Evaluation of Ionome and Ionomics under Salt Stress Condition

Walnut (J. regia L.) is a very sensitive plant to abiotic stresses and finding salt tolerant genetic resources is important in this species. Effects of salt stress on seed germination of seven walnut cultivars, 'Serr', 'Lara', 'Pedro', 'Chandler', 'Hartely', 'Vina' and 'Roun de Montignac', were studied. Stress treatments were applied using NaCl solutions ranging from 50 to 250 mM. With the increase in media salt stress, resistant cultivars accumulated K and Ca, especially in their shoots. However, in the semi-tolerant cultivars there was only accumulation of K in the root. It is proposed that different stress tolerant groups have different cell membrane transport properties. Salt stress increased K uptake from root to shoot, which is likely to be a regulation of osmotic adjustment. The differences in Mg accumulation in roots and shoots of all samples were significant at all stress levels and were not dependent on cultivars. Differences in Na accumulation were minimal compared to the other minerals at different stress levels. Na levels in roots were more than in shoots in most cultivars especially in the semi-sensitive and tolerant cultivars. It was proposed that the magnitude of K leakage from tissues after being exposed to osmotic stress might be used as a screen to identify salt tolerant walnut cultivars. There was a low correlation (P <= 0.15) between walnut seed traits (seed weight and kernel weight) and growth indices in tolerance to salinity.