Root system architecture and anatomical traits variability of alfalfa at the seeding stage

Abstract Background and aims Alfalfa (Medicago sativa. L) growth is largely restricted by abiotic stress such as drought and nutrient deficiency. Identifying root architectural and anatomical characteristics is of great significance for breeding alfalfa genotypes with improved adaptation to adverse environments. Methods Using nutrient solution sand culture method and visual rhizobox cultivation system, we explored the variability in root system architecture (RSA) and anatomy of 53 alfalfa genotypes at the seedling stage. Results Among 44 measured traits, 23 root traits, nitrogen (N) and phosphorus (P) uptake exhibited larger coefficients of variation (CVs ≥ 0.25) across tested genotypes. The variation degrees of local root traits and root anatomical traits were larger than global root traits. Twenty-five traits with CVs ≥ 0.25 constituted 6 principal components (eigenvalues > 1) accounting for 88.9% of the total genotypic variation. Total root length, root length in diameter thin, root tips number, maximal root depth, root length and root tips number in different soil layers were positively correlated with shoot dry mass and root dry mass (P ≤ 0.05). Total stele area (P ≤ 0.05) and xylem vessel area (P ≤ 0.001) were positively correlated with N and P uptake. Conclusion The tested alfalfa genotypes showed larger variation in local root morphological and anatomical traits at the seedling stage. Some important root traits, including root length, root length in diameter thin, root tips number, maximal root depth, total stele area and xylem vessel area have potential function on breeding alfalfa genotypes with improved adaption to abiotic stress.