Multi-physiological-trait selection indices to identify Lotus tenuis genotypes with high dry matter production under drought conditions

Physiological breeding for improving drought tolerance in perennial forage legume species has been a complex task because of the low association between single physiological traits and dry matter (DM) production under drought conditions. The combination of physiological traits in selection indices may be a more effective alternative in identifying drought-tolerant genotypes. In this work, some physiological and agronomical traits were evaluated in 100 Lotus tenuis genotypes. Traits were measured in spaced plants under irrigation and rainfed conditions during two growing seasons in Chillán, Chile. Three multi-physiological trait indices were calculated based on multiple linear regression (SI1), Euclidean distance (SI2) and descriptive statistical parameters (SI3). SI1 and SI2 were significantly correlated with DM production under rainfed conditions, with correlation coefficients of 0.61 and –0.52, respectively. On the other hand, all single physiological traits showed broad genetic variability in the L. tenuis population but a low association with DM production under drought conditions. Therefore, the multi-trait indices are a more effective tool to select drought-tolerant genotypes.