Differences of morphological and physiological responses of sainfoin varieties/lines under simulated drought stresses

Sainfoin (Onobrychis viciaefolia) is an important legume forage. This study aims to explore the response mechanisms of sainfoin germplasm resource accessions to drought stress, which provides the theoretical basis for tolerant breeding of sainfoin. In this study, 20 sainfoin germplasm resource accessions were used as the test materials, and the effects of drought stress on morphological and physiological characteristics were determined under simulated levels of drought (−0.5, −1.0, −1.5 and −2.0 MPa) × exposure times (7 days) in pots. The results showed that leaf area, leaf relative water content, root-shoot ratio, root length, root surface area, root volume, root diameter, root tip number, chlorophyll a content, chlorophyll b content and catalase activity decreased with increasing drought stress. In contrast, proline, soluble sugar, soluble protein and malondialdehyde contents increased in response to drought. Root activity, superoxide dismutase and peroxidase activities increased first and then decreased and reached the maximum at −1.0 MPa. Cluster analysis showed that 20 sainfoin germplasm resources could be divided into three categories, of which four accessions were high tolerance types, and three accessions were low tolerance type. These findings will help provide some theoretical basis for cultivating new varieties.