Using leaf sodium concentration for screening sodicity tolerance in cotton (Gossypium hirsutum L.)

The ability of a plant to maintain low Na concentration is a critical component for its tolerance to salt affected soil stresses. Leaf Na concentration was investigated to understand its usefulness in screening of cotton for tolerance to soil sodicity and to assess its effect on agronomic performance. A set of family lines and high yield lines with low and high leaf Na concentration were tested in field experiments with sodic soils. The youngest fully expanded leaves at early flowering and whole plant biomass samples at the cut-out stage were collected for nutrient analysis. Plots were harvested for yield and fibre quality. Leaf Na concentration was found to be a reliable measure for differentiating test lines with low and high leaf Na trait. Leaf K/Na and P/Na ratio acted similarly. Low leaf Na concentration was due to higher Na accumulation in plant stems and roots. It was associated with higher K/Na and P/Na ratio in leaves and bolls, and responsible for improved K and P use efficiency. High performing lines with the low leaf Na trait had yield and fibre properties competitive with the control. It is concluded that the low leaf Na trait at flowering provided a reliable phenotypic indicator for cotton tolerance to soil sodicity. Breeding for the trait can improve sodicity tolerance, K and P use efficiency, while maintaining agronomic performance.