Abstract:

In this study， we screened for Elymus sibiricus genotypes with strong cold resistance， and investigated the mechanism of cold resistance. In a pot experiment， 43 wild-type E. sibiricus germplasm lines were subjected to a freezing treatment at -4 ℃， and the relative electrical conductivity， chlorophyll content， and maximum photochemical efficiency were determined. The data were subjected to a multivariate membership analysis to evaluate the cold resistance of these diverse lines. On the basis of this analysis， a cold-resistant genotype （I-1-4-1） and a cold-sensitive genotype （09-244） were selected. Chilling （4 ℃） and freezing treatments （-4 ℃） were applied to I-1-4-1 and 09-244. The differences in leaf relative water content， cell membrane permeability， osmotic substance content， antioxidant system capacity， and chlorophyll fluorescence parameters between I-1-4-1 and 09-244 under cold stress were analyzed. Under -4 ℃ freezing stress， the chlorophyll content， maximum photochemical efficiency of photosystem II， actual photochemical efficiency， photochemical quenching coefficient， and non-photochemical quenching coefficient were higher in I-1-4-1 than in 09-244， indicating that I-1-4-1 could maintain efficient photosynthesis. Under -4 ℃ freezing stress， the superoxide anion and hydrogen peroxide contents in the leaves were lower in I-1-4-1 than in 09-244， while catalase activity was higher in I-1-4-1 than in 09-244， indicating that I-1-4-1 had a stronger ability to scavenge reactive oxygen species compared with 09-244. The relative electrical conductivity and malondialdehyde content were lower in I-1-4-1 than in 09-244， indicating that the membrane system of I-1-4-1 was less damaged under freezing stress. In addition， I-1-4-1 was better able to adapt to cell dehydration induced by freezing stress by accumulating more free proline to improve osmoregulation. Two principal components were extracted by a principal component analysis. Their cumulative contribution to explaining the variation in cold resistance was >85%. The first principal component was mainly related to photosynthesis and cell membrane permeability， and the second principal component was mainly related to osmotic regulation substances. These results provide reference data for the evaluation of cold resistance and the selection of cold-resistant germplasm resources of E. sibiricus.

Key words: Elymus sibiricus, chilling stress, freezing stress, chlorophyll fluorescence, reactive oxygen species