Background/Introduction: Rising soil salinity poses a significant challenge to Mediterranean viticulture, particularly affecting grapevine productivity and sustainability. While established rootstocks have demonstrated capacity to mitigate salt accumulation in grafted scions, the mechanisms and performance characteristics of novel rootstock varieties remain insufficiently characterized, creating a critical knowledge gap in viticultural adaptation strategies.
Goals: This investigation aimed to evaluate and compare the salt tolerance mechanisms of two novel M-series rootstocks (M2 and M4) against established commercial standards (1103 Paulsen and R110), with specific focus on their physiological responses, growth patterns, and ion management strategies under varying salinity conditions.
Methodology: This study implemented a controlled irrigation protocol with four salinity levels (0, 25, 50, and 75 mM NaCl) over a five-month period. Comprehensive assessment included growth parameters, photosynthetic efficiency measurements, chlorophyll content (SPAD) analysis, ion homeostasis evaluation, and systematic monitoring of visual stress symptoms.
Results: Analysis revealed distinct genotype-specific tolerance strategies among rootstocks. 1103 Paulsen demonstrated superior salt tolerance through maintained photosynthetic efficiency (maintaining 85-90% of control Fv/Fm values) and effective ion exclusion, showing moderate biomass reduction (58.8% decrease in dry weight) under severe stress. M2 exhibited exceptional biomass retention (47.3% reduction in fresh weight) and moderate ion compartmentalization capability, despite showing 30-35% reduction in photosynthetic performance under elevated salinity. R110 displayed effective ion management under moderate stress conditions (maintaining K+/Na+ ratios above 2.71 at 50 mM NaCl) but suffered substantial growth decline (59.7% reduction in fresh weight) at higher salinity levels. M4 emerged as the most salt-sensitive genotype, exhibiting the highest reductions in both biomass (69.0% decrease in fresh weight) and ionic balance (91% decrease in K+/Na+ ratio). Organ-specific analyses revealed specialized roles in salt stress management: roots accumulated the highest Ca2+ concentrations (4.82-6.44%); leaves showed dramatic increases in Cl− content (from 0.08% to 3.25%); and stems maintained the highest Na+ levels (up to 2.37%), serving as crucial buffering zones protecting photosynthetic machinery.
Conclusions: These findings provide crucial insights into rootstock-specific salt tolerance mechanisms and establish a foundation for informed rootstock selection in salt-affected regions. The demonstrated variability in stress responses among genotypes offers valuable direction for breeding programs aimed at developing salt-tolerant rootstocks for sustainable viticulture in increasingly challenging environments.
