Selection Of Cold Tolerance Bermudagrass Accessions And Study On Its Mechanism Of Cold Tolerance Regulated By Glycine Betaine

Bermudagrass(Cynodon dactylon(L).Pers.)is a perennial grass in Poaceae.Bermudagrass is low,slender and trample-resistant that be widely used in lawns,sports field,and the vegetation restoration in slope.However,the use of bermudagrass is limited because of its weak cold tolerance.In this study,the cold tolerance of native bermudagrass collected from southwest of China were evaluated.Physiological responses of cold-tolerant and cold-sensitive accession under cold condition were researched.To explain the molecular mechanism of glycine betaine(GB)regulated cold tolerance of bermudagrass,the effects of exogenous GB on the differentially expressed genes and the metabolic pathway using transcriptome technology were analyzied.The main research results are as follows:1.The cold tolerance of 52 bermudagrass accessions was studied using methods of the green period,semi-lethal temperature and stolon regrowth experiments.Results were obtained as follows,52 bermudagrass accessions were clustered into three groups: cold tolerant,cold semi-tolerant,and cold sensitive.The cold tolerance of bermudagrass could be better evaluated through the three reference indicators together.2.The physiological responses of cold-resistant(Sau02040)and cold-sensitive(Sau9928)bermudagrass under cold condition were studied.The results showed that compared with the Sau9928,there were more accumulation of soluble carbohydrate and proline,higher antioxidant activity,and lower accumulation of reactive oxygen species in Sau02040.These may be the main physiological mechanism that Sau02040 had stronger cold tolerance.3.Many cold responsive genes were investigated by RNA-Seq.Transcription factors such as ERF,NAC,WRKY and DREB were identified.Gene ontology(GO)and Kyoto encyclopedia of genes and genomes(KEGG)pathway term enrichment analyses revealed that effects of exogenous GB on differentially expressed genes under cold condition involved many functional annotations including amino acid metabolism,carbohydrate metabolism,catalytic activity,biological regulation,stress response and many metabolic pathways,including flavonoids,plant hormone signals,plant MAPK signals,and photosynthetic metabolism pathways.In conclusion,this study researched the cold tolerance of bermudagrass accessions,and provided bermudagrass germplasm resources for cold-tolerance varieties breeding.Based on the transcriptome analysis,the molecular mechanism of cold tolerance in bermudagrass was determined.This study showed that exogenous GB was efficient in improving bermudagrass cold tolerance.The results were helpful for cultivation and management of bermudagrass under low temperature stress.