Root Growth and Architecture Responses of Bread Wheat Cultivars to Salinity Stress

The screening of genotypes that perform better in saline soils is important for food security as the arable land affected by this problem is increasing. To mimic the conditions found in saline fields, a saline soil-based screening method was developed to distinguish genetic diversity in root growth responses and shoot growth rates of bread wheat (Triticum aestivum L.) cultivars, namely Roshan, Bam, Tabbasi, Mahooti, Shiraz, Qods, Falat, and Atrak. Soil-filled polyvinyl chloride (PVC) tubes perfused with 50 to 200 mM NaCl and a standard nutrient solution was employed. A constant salt concentration was maintained throughout the soil profile in the PVC tubes. Genetic variation in root growth and leaf Na+ concentrations was observed between cultivars in response to salinity. Salinity decreased the relative growth rate, seminal and total root length, and the distance between root tip and the first lateral root but increased total branch roots. For most traits, the growth reductions due to salinity were higher in salt-sensitive compared with salt-tolerant cultivars. The seminal root length was reduced more than branch root length in all cultivars. Roshan and Tabbasi were identified as the most tolerant to salinity due to their longer seminal axile roots, shorter distance from the tip, higher distal branch root numbers, and higher branch root length compared to the other cultivars. A positive relationship between genetic variations in root growth response and relative growth rate indicates that root growth might be the key factor driving shoot growth and can be used as a criterion for screening salinity tolerance.