Screening and identification of excellent alkali-tolerant germplasm of barley at the germination stage

Soil salinization and/or alkalization is a major problem affecting agricultural production and ecological security in China, and screening barley germplasm with strong alkali tolerance plays a significant role in the improvement and utilization of saline-alkali land. To elucidate the acquisition of barley alkali tolerance and the associated physiological responses during the germination stage, we systematically evaluated the physiological responses of 199 barley germplasms with different genetic backgrounds during the germination stage under alkali tolerance. The results revealed that germination rate, germination index, vigor index, shoot length, and root length were selected as the key indexes to evaluate barley alkali resistance at the germination stage. These barley germplasms were divided into four categories based on the F value from principal component analysis and the Z value from the entropy-weighted fuzzy affiliation function method. They include 43 alkali-tolerant germplasms, 96 moderately alkali-tolerant germplasms, 35 alkali-sensitive germplasms, and 27 extreme alkali-sensitive germplasms. Among them, ‘2011C/26’ was the most alkali-tolerant germplasm, and the second one was ‘Edamai 259’. Further analysis of physiological characteristics responding to alkali stress showed that the alkali-tolerant germplasm has stronger enzyme activities of superoxide dismutase, peroxidase, and catalase, a more active AsA-GSH cycle, and less malondialdehyde accumulation.