Evaluating the Growth Response of Ricinus communis L. Cultivars to Salt Stress Using a Fast and Reliable Bioassay

Abstract Here is proposed an easy, fast, and economic technique to investigate plant physiological traits in response to salt stress by using castor bean ( Ricinus communis L.). Four Ricinus communis L. cultivars (TUNI 1, TUNI 4, C1012, and C1028) were grown in a growth chamber for 15 days on a sand substrate and were watered regularly with deionised water or NaCl solution (water electrical conductivity (EC) 4, or 8 dS m − 1 ) to keep soil moisture close to field capacity. According to roots, stem, and germination traits and derived indices, TUNI 1 and TUN4 showed the best growth performance on sand irrigated with 4 dS m − 1 and 8 dS m − 1 , respectively. Besides, comparing C1028 and C1012, the former showed a higher tolerance at the maximum electrical conductivity tested related to the latter, increasing salt tolerance index (STI) of roots (+ 25%) and stem (+ 20%). In conclusion, the present findings suggest that the TUNI 4 cultivar of Ricinus communis L. demonstrates superior overall performance, even under highly saline conditions, such as irrigation with 8 dS m − 1 . Conversely, the TUNI 1 cultivar shows a good ability to perform in marginal soils with moderate salinity levels, such as those irrigated with 4 dS m − 1 . Our results represent the first step towards optimization of a cost-effective method/bioassay for the selection of salt tolerant Ricinus communis L. cultivars and genotypes.