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

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.