Salinity-induced dynamics in root system architecture of Brassica juncea : Insights from rhizovision explorer-based root phenotyping for climate-resilient agriculture

Abstract

The salinity problem is still a major challenge in crop production in agricultural systems worldwide, yet the impact of salinity on crop root system architecture at trait level in Brassica juncea is still poorly known. The root architectural response is of special importance in the context of how mustard plants react to salt stress, as it is the first organ to be exposed. For this study, B. juncea seedlings were grown for 65 days under greenhouse conditions subjecting them to a range of NaCl concentrations (0, 12, 25, 50 and 100 mM). Root architectural features were quantified using RhizoVision Explorer, which has the ability to precisely image and quantify root complexity that would not be otherwise available in traditional studies. Unlike previous Brassica salinity studies that primarily focused overall root growth and physiological responses, this study comprehensively quantified multiple root architectural traits using RhizoVision Explorer to identify sensitive architectural indicators for salinity tolerance screening. It was observed that root architecture declined in a clear, concentration dependent manner with increasing salinity. One-way ANOVA revealed significant treatment effects on all measured root architectural traits (p < 0.001). At 100 mM NaCl, the root length and volume were reduced by 38.4% and 37.5%, respectively, compared with the control. Notably, lateral root growth and network area both dropped more than 50% at the highest salt concentration, indicating that lateral root growth and network area are much more sensitive to salt stress than total root mass. Pearson correlation analysis verified that all the measured traits decreased together, and the PCA accounted for 90.5% of the total variance in two components and showed a good spatial distinction between treatments of low and high salinity. Combined, these results indicate that salinity first systematically compromises the branching ability of the root system and then its explorative network in a non-random manner. The root tips and network area covered by roots were observed to be useful as early indicators of salt-induced architectural damage for salinity tolerance screening. Thus the findings demonstrate that root tips and network area can serve as rapid phenotyping traits for screening salinity-tolerant Brassica genotypes and may support breeding programs aimed at developing climate-resilient mustard cultivars for saline environments.