Evaluation of Salinity Tolerance Threshold in 11 Selected Almond Cultivars and Genotypes

Salinity tolerance threshold of fruit crops is obtained based on the reduction in yield under saline conditions compared to non-saline conditions. In order to determine salinity tolerance threshold and yield reduction per unit increase in soil salinity in selected almond genotypes, a factorial experiment was carried out. The study was based on completely randomized design (CRD), with two factors: (1) genotypes in 11 types (Tuono, Nonpareil, Mamaei, Shokoufeh, Sahand, Shahrood12, A200,1-25, 1-16 and 13-40 budded on GF677 rootstock, and GF677 rootstock (without budding as control), and (2) salinity of irrigation water at five levels (0.5, 2.5, 4.9, 7.3 and 9.8 dSm-1). At the end of experiment, salinity tolerance threshold and yield reduction slope were calculated based on dry weight (biomass).The results showed that the type and combination of rootstock and scion affect the salinity tolerance threshold and yield reduction slope. The lowest salinity tolerance threshold was observed in 1-16 (2.22 dS/m), Mamaei (2.28 dS/m), and Sahand (2.39 dS/m) genotypes, respectively. On the contrary, the highest salinity tolerance threshold was observed in Shokoufeh (5.80 dS/m), Shahrood12 (4.84 ds/m) and 1-25 (4.80 ds/m).The highest yield reduction slope was observed in 13-40 (8.05%), A200 (7.86%), and Nonpareil (7.55%) genotypes, respectively. In contrast, the lowest yield reduction slope was observed in Shahrood 12 (5.60%). Overall, the results showed the level of salinity that reduced the yield by 50% in Shahrood 12, Shokoufeh, and 1-25, were 5.05, 4.43 and 3.55 dS/m greater than GF677 rootstock (without budding), respectively. EC50 in Shahrood 12, Shokoufeh, 1-25 and GF677 was observed in salinity intensity of 13.23, 12.59, 11.71 and 8.16 dS/m. It should be noted that in previous studies, 100% decrease in yield was reported by salinity level of 7 dS/m, while in Shahrood 12 and Shokoufeh cultivars budded on GF677 rootstock, we observed only 12% and 9% yield reduction by salinity of 7 dS/m. Therefore, we suggest that Shahrood 12 and Shokoufeh cultivars budded on GF677 rootstock could be cultivated in areas with moderate salinity.