Influence of host plant selection on salinity tolerance and antioxidative defense in Sandalwood (Santalum album L.)

Abstract

Sandalwood (Santalum album) has been highly valued in India for centuries. However, detailed and comprehensive information on the physiological and biochemical changes in sandalwood particularly when associated with host plant species under salinity stress, is currently lacking. Considering the immense potential of sandalwood, an experiment was conducted under controlled conditions by growing sandalwood with ten different host plants and irrigated with good quality water (control: EC_iw∼0.82 dS m^-1) and saline water (EC_iw∼6 dS m^-1). Results indicated host-dependent significant variations in sandalwood growth under both controlled and salinity-stressed conditions. Among the different host plant species, Melia dubia, Dalbergia sissoo, and Azadirachta indica improved the plant height (46 %), biomass (45 %), haustoria number (120 %) and diameter (75 %) of sandalwood as compared to rest of the hosts under saline condition. These three host species also improved the physiological processes of sandalwood, such as, SPAD value (up to 22.55), proline content (by 460 %), membrane stability with electrolyte leakage as low as 10.85 %, K⁺/Na⁺ ratio (>1.0). Meanwhile, reduction in lipid peroxidation (by 10 %) and H₂O₂ accumulation were observed. Similarly, non-enzymatic antioxidants of sandalwood under salinity stress increased by over >40 %. Antioxidative enzyme activities, particularly superoxide dismutase, were upregulated by up to 50 % under salinity stress, with the highest increase observed in sandalwood grown with M. dubia. Principal component analysis indicated that D. sissoo and M. dubia are the most favourable hosts for sandalwood under salinity stress, while Citrus aurantium is the least supportive. Overall, findings suggested that M. dubia and D. sissoo are the most important species in the alleviation salt stress in sandalwood. Consequently, this presents an opportunity to establish high- value sandalwood-based plantations in saline ecologies.