Interspecific hybridization and inoculation with Pantoea eucalypti improve forage performance of Lotus crop species under alkaline stress

This study was designed to elucidate the physiological responses of three Lotus forage accessions to alkaline stress, and the influence of inoculating with Pantoea eucalypti endophyte strain on alkaline stress mitigation. A diploid L. corniculatus (Lc) accession, L. tenuis (Lt), and the interspecific hybrid Lt × Lc obtained from these two parental lines were exposed to alkaline stress (pH 8.2). Both Lt and the Lt × Lc hybrid are alkaline-tolerant compared to Lc, based on observations that dry mass was not reduced under stress, and there were no chlorosis symptoms on leaf blades. In all three Lotus accessions, Fe²⁺ concentration under stress decreased in aerial parts and simultaneously increased in roots. Inoculation with P. eucalypti considerably increased Fe²⁺ content in shoots of all three Lotus forage species under alkaline treatment. Photochemical efficiency of PSII was affected in Lc accession only when exposed to alkaline treatment. However, when cultivated under alkalinity with inoculation, plants recovered and had photosynthetic parameters equivalent to those in the control treatment. Together, the results highlight the importance of inoculation with P. eucalypti, which contributes significantly to mitigating alkaline stress. All results provide useful information for improving alkaline tolerance traits of Lotus forage species and their interspecific hybrids.