Exploiting halotolerant endophytes to improve growth and salinity resilience of Catharanthus roseus (L.) G. Don

Abstract

Increasing soil salinization severely threatens agricultural productivity in many coastal ecosystems and dryland regions. In this study, two halotolerant endophytic bacterial strains, Bacillus sp. CR-4 and Streptomyces sp. CR-7, was isolated from Catharanthus roseus collected from saline coastal areas and evaluated for its plant growth-promoting traits and salt stress-mitigation ability. The selected isolates displayed diverse plant-beneficial properties such as phytohormone synthesis, nutrient mobilization capacity, and stress-associated enzymatic activities. Inoculation with these strains significantly enhanced plant height, biomass, relative water content, and chlorophyll index under 100 mM NaCl stress in greenhouse conditions. Field trials in saline soils further confirmed improved survival, flower yield, and physiological traits in treated plants. Biochemical analyses revealed increased proline accumulation, enhanced antioxidant enzyme activities (SOD, POD, CAT), and reduced membrane damage, highlighting the stress mitigation effects of these endophytes. Multivariate analysis confirmed strong correlations between microbial traits and plant physiological performance. These results demonstrate the potential of CR-4 and CR-7 as effective bioinoculants for the sustainable cultivation of C. roseus and possibly other crops in salt-affected areas.