A procedure for assessing the salt tolerance of lucerne (Medicago sativa L.) cultivar seedlings by combining agronomic and physiological indicators

Abstract

Salinisation caused by irrigation is threatening the forage yield of lucerne pasture in the arid and semi‐arid areas of west China. To select lucerne cultivars with good salt tolerance, the relative salt tolerance of five lucerne cultivars was assessed based upon shoot dry weight, shoot KV Na+ ratio, leaf malondialdehyde (MDA) content and relative membrane permeability (RMP) at the seedling stage. NaCl reduced the shoot dry weight and shoot K+/Na+ ratio, and enhanced the leaf MDA content and RMP in all cultivars, but the degree of either reduction or enhancement differed between these lucerne cultivars. Under 200 mM NaCl for 5 days, ‘Rambler’ had significantly greater shoot dry weight (only dropped 17.2% to 0.17 g plant‐1) than other cultivars, and also maintained a better ion status, with higher K+ content, lower Na+ content, and thus a higher relative shoot K+/Na+ ratio. ‘Daye’ was healthier because neither the MDA content nor the RMP was significantly increased in its leaves. Through combining the relative values of these indicators, the relative salt tolerance of the five cultivars decreased in the order: ‘Rambler’, ‘Daye’, ‘Sandili’, ‘Gannong No.3’, and ‘Longdong’. This study indicated that ‘Rambler’ and ‘Daye’ might be suitable for pasture establishment on irrigated land in arid and semi‐arid areas of west China.