The root is the organ of a plant that firstly is affected by salinity and may play a significant role in stress tolerance. There is limited information on the role of root morphological traits in different soil layers of salinity tolerance in halophytes. This experiment aimed at investigating the importance of root morphology attributes in salt tolerance of blue panicgrass (Panicum antidotale Retz.) using artificial neural networks (ANN). In a column experiment, blue panicgrass plants were exposed to four salinity levels of irrigation water (0, 86, 189 and 345 mM NaCl). The root dry weight decreased by 26, 54 and 54% at 86, 189 and 345 mM compared to the control, respectively. Salinity had no significant effect on root penetration, while it significantly decreased the length, diameter, volume, weight, number and area of plant root system. The ANN model used for predicting plant salt tolerance resulted in R2 and RMSE values of 0.95 and 0.013, respectively. According to sensitivity analysis, the root penetration in different soil layers was the most important root morphology attribute affecting salt tolerance of blue panicgrass. The role of length, diameter, volume, weight, number and area of root on salt tolerance of plant was dependent on the soil depth. For the weight, area and number of roots, the greatest sensitivity coefficient was related to the depth of 60-80 cm, while the length and diameter of roots at 0-20 cm showed the greatest sensitivity coefficient. The results showed that root penetration was the most effective factor in salinity tolerance of blue panicgrass. Although, it should be considered the most effective soil depth for each root trait.

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