Abstract: INTRODUCTION: Identification of salt-alkali tolerant germplasm in faba bean lays the foundation for the exploration of salt-alkali tolerant genes and for the selection and breeding of salt-alkali tolerant varieties, which is of great significance for the utilization of saline-alkali land. RATIONALE: Most of the studies on the salt-alkali tolerance of faba beans were focused on the morphological and physiological traits of the aboveground parts, while there are few studies on the phenotypic traits of the roots. The root plays a crucial role in resisting salt-alkali stress. Deep research on the relationship between the phenotypic traits of the root and the salt-alkali tolerance of faba beans will help to comprehensively understand the physiological mechanism of the salt-alkali tolerance. RESULTS: The results showed that: (1) Under salt-alkali stress, the root overlap number was mostly affected, it was followed by the coila number, while the average diameter of root was affected slightly; (2) Between the overlap number and total number of connection points, among the bifurcation number and the overlap number and total number of connection points, most of indicators were significant positively correlation (P<0.01), while there were significant negatively correlation (P<0.01) among the average diameter of root and total number of root, the number of root tip, total length of root, endpoint number, coila number, linking number, bifurcation number, overlap number and total number of connection points; (3) Total root surface area of root, total projected area of root, total length of root and total volume of root could be used as the key indicators to identify the salt-alkali tolerance of faba bean during the germination period; (4) Two salt-alkali tolerant accessions H0000809 and H0000653, and two salt-alkali sensitive accessions H0001714 and H0002622 were screened out; and (5) The 399 faba bean accessions were divided into 4 groups: group I, salt-alkali tolerance germplasm, accounting for 0.75%; group II, moderately salt-alkali tolerant germplasm, accounting for 8%; group III, weakly saline-tolerant germplasm, accounting for 52.88%; and group IV, salt-alkali sensitive germplasm, constituting 38.35%. CONCLUSION: Variation and correlation of each index, and the key indicators used to identify salt-alkali tolerance were determined, extreme materials can be selected and used for future study of salt-alkali tolerance mechanisms in faba bean and the excavation of salt-alkali tolerance genes. Phenotypic differences of faba bean germplasms with different levels of salt-alkali tolerance at different growth stages (A) Root phenotype differences of faba bean germplasms with different levels of salt-alkali tolerance at germination stage (bar=5 cm); (B) Plant phenotype differences of faba bean germplasms with different levels of salt-alkali tolerance at flowering stage (bars=1 cm).

Key words: faba bean (Vicia faba), germination stage, salt-alkali stress, salt-alkali tolerant germplasm identification, comprehensive evaluation