Association of Seedling Vigour and Salinity Tolerance in Field Pea

Soil salinity results in reduced productivity in field peas, making soil salinity tolerance a critical breeding objective. In this study, four pot experiments were carried out in semi-controlled environments over four consecutive years to assess the contribution of seedling vigour to salinity tolerance at the seedling stage. Split-plot designs were used to assess the effect of salt stress (sodium chloride solution at 16 dSm^-1) and control conditions. Extensive sets of advanced breeding lines were used in 2018-2020 to assess growth differences in relation to the treatment, with elemental analysis used on a subset of 15 lines in 2021. A salt tolerance index (STI) was defined as a proportion of shoot biomass under salt stress (DWstress) relative to the shoot dry weight under control (DWctrl). Visual scores of salt stress were recorded on a 1-10 scale (1 = tolerant, 10 = susceptible) from salt stress treatments. The consistent positive and significant correlations (p < 0.01) between shoot DWctrl and DWstress indicated that vigorous genotypes maintained higher shoot DWstress. Both the shoot DWctrl and shoot DWstress had negative and significant (p < 0.01) correlations with visual scores of salt stress. Shoot DWstress showed strong positive correlations with STI (p < 0.01). Both the shoot DWctrl and Shoot DWstress had negative correlations (p < 0.01) with shoot Na⁺ whereas shoot DWstress had a positive correlation (p < 0.05) with root Na⁺ concentration. The results indicated that seedling vigour (measured as shoot DWctrl) contributed to salinity tolerance by maintaining improved shoot DWstress, limiting Na⁺ deposition in shoot and enduring less tissue damage in field pea seedlings. Additional field evaluations are required to establish the correlations of tolerance at seedling stage with yield under saline conditions. The insights obtained from this study may assist field pea breeders in identifying salt-tolerant parent plants, offspring, and breeding lines during the initial growth phases.