Pre-breeding for drought tolerance in Lotus tenuis under saline-sodic soil conditions

Context Developing drought-tolerant forage legumes adapted to saline-sodic soils is essential to sustaining livestock production in marginal environments. Pre-breeding programs allow the identification of useful genetic variation within naturalized populations for this purpose. Aims This study aimed to (i) compare the performance of half-sib families (HSFs) from a naturalized population of Lotus tenuis, with a commercial cultivar under drought stress, and (ii) identify key traits and promising materials for breeding. Methods Twenty HSFs and one cultivar were evaluated under controlled conditions in a factorial design with two water regimes (field capacity and drought). Morphological, physiological and biochemical traits were measured, including aerial dry biomass, number of branches, leaf temperature, ion concentrations (Na+, K+), relative water content and oxidative stress indicators. Narrow-sense heritability and genetic correlations were estimated, and multivariate analyses were performed. Key results Drought significantly reduced growth and altered physiological traits, with differential responses among genotypes. Some HSFs matched or exceeded the cultivar for aerial biomass production under stress. High heritability (h2 > 0.8) was observed for aerial biomass, number of branches, leaf temperature and ion concentrations under drought. Growth traits were positively correlated and negatively associated with leaf temperature and Na+. Conclusions Five HSFs (9, 12, 13, 16, and 20) were identified as promising materials on the basis of their performance for aerial biomass, leaf temperature, and Na+ concentration, traits identified as reliable selection criteria for drought tolerance under saline-sodic soil conditions in L. tenuis. Implications These families provide valuable resources for breeding drought-tolerant cultivars for saline drylands, although further selection and recombination are required.