| Low temperature is the main influencing factor limiting the growth and development of maize in Tibet.In this study,298 Tibetan maize as the experimental materials,the cold resistance and further obtained the germplasm of low temperature resistance and analyzed the different metabolites at low temperature,in order to further analyze the physiological mechanism of Tibetan maize.The results indicate that:(1)After 4 days of low temperature treatment at 4 °C,the corn recovered and grew at room temperature at 25 °C for 2 days,and the average leaf area injury area was 24.18～100%.After 8 days of low temperature treatment at 2 °C,the growth of the corn was restored at room temperature at 25 °C for 14 days,resulting in the low-temperature death of some of the corn in the test,and the survival rate of the surveyed maize was 9.09～90.91%.Based on the leaf area,survival rate and cold resistance grade division under low temperature stress,a comprehensive evaluation of 298 Tibetan maize inbred lines was carried out,and 5Tibetan cold-tolerant maize varieties(L56,L66,L280,L53,L54),5non-cold-resistant varieties(L78,L90,L116,L231,L286).(2)Based on the early cold resistance screening,10 inbred lines of Tibetan maize with different cold resistance were used as experimental materials to further study the cold resistance and physiological mechanism of Tibet maize.The results showed that the MDA content in the leaves of 10 Tibetan maize cultivars was significantly higher than that in the control under low temperature stress,indicating that low temperature may increase the degree of membrane lipid peroxidation in the leaves of the participating maize,resulting in membrane damage.The contents of protective enzyme POD,SOD and CAT in the leaves of10 Tibetan maize varieties increased to varying degrees compared with the control under low temperature stress.Cold-resistant varieties increased significantly compared with non-cold-resistant varieties.The total chlorophyll content of different cultivars decreased to varying degrees after low temperature treatment.Based on the three methods of cluster analysis,correlation analysis and membership function value,8indexes of 10 varieties were comprehensively analyzed,and strong cold-resistant variety L 56 and non-cold-resistant variety L 78 were obtained Number.(3)In this paper,L56 and L78 were used as test materials for non-targeted metabolomics research,and the results showed that 1 106 metabolites were detected in the positive and negative ion modes(1 97 differential metabolites)and 723 metabolites(107 differential metabolites)are associated with maize cold resistance,with carboxylic acids and their derivatives as many as metabolites 26.8%。In the positive and negative ion mode,there are 9 6 kinds of differential metabolites shared by cold-resistant material L56 and non-cold-resistant material L78,mainly including methionine,5-aminosalicylic acid,coixine,valine,DL-Tryptophan,2-isopropylmalic acid,citric acid,L-threonine and other differential metabolites were significantly upregulated;There are 32 kinds of metabolites unique to L56,mainly including 2-hydroxycinnamic acid,clover,psoralenol,niacinamide,dodecaneedioic acid,corticosterone,itaconic acid and other differential metabolites significantly upregulated;There are 80 kinds of metabolites unique to non-cold-resistant L78 material,mainly including hydroxyproline,2-hydroxyphenylalanine,N-acetyl-5-aminosalicylic acid,and α-Ketoglutaric acid,niacin,2,3-dihydroxybenzoic acid,2,5-dihydroxybenzaldehyde,cis-cis-aconitic acid,azelaic acid,2-Differential metabolites such as furocarboxylic acid are significantly upregulated.The two maize cultivars were enriched into the 2-oxocarboxylic acid metabolic pathway related to energy conversion and the carbon-five-branched diacid metabolism pathway related to plant metabolism and carbohydrate metabolism at low temperature,indicating that the material energy conversion and metabolism of Tibetan maize under low temperature stress were the main physiological mechanisms to resist low temperature in the cold environment.This study laid a certain foundation for further research on the cold tolerance of maize in Tibet. |
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