Study On Cadmium Tolerance Of Different Rice Varieties Based On GC-MS And Near/Mid-infrared Spectroscopy

Environmental stress will adversely affect the growth and yield of plants,and it is also the main factor affecting the global crop productivity.Therefore,the development of environmental stress-resistant crops is an important means to improve crop quality and yield,and seeds are used to determine crops.An important factor of good and bad,the rapid,accurate and nondestructive method of screening rice seeds with strong cadmium tolerance is one of the current effective methods to solve the problem of heavy metal pollution in farmland.The rice varieties are of great significance to human health and food economic development.In this paper,a total of 30 rice seeds of randomly selected varieties and inbred lines planted in the south and in Tianjin are used as materials.First,the traditional detection methods and cluster analysis are used to select the most similar varieties of cadmium tolerance.Gas chromatography-mass spectrometry（GC-MS）,near / mid infrared spectrometer,through the detection of small molecule metabolites and spectral curves of different rice varieties,by principal component analysis,partial least squares discriminant analysis,systematic cluster analysis and twodimensional correlation Spectral and other chemometric methods are used to organize and analyze the data obtained,and find the metabolite and spectral differences of different cadmium-tolerant rice,and draw the following conclusions:1.According to the results of cluster analysis combined with the variation coefficients of cadmium tolerance index and translocation coefficient of rice roots and aboveground,it is concluded that after cultivating less cadmium-tolerant varieties and moderate cadmium-tolerant varieties into one category,the varieties are divided into two categories,namely 14 common rice varieties,Jinyuan E28,Jinchuan No.1 Tianjin Agricultural College inbred line 4,Jinyuan89,C418 restoration line,Tianjin Agricultural College inbred line 5,Jinyuan U99,Jinyuanxiang98,Tianjin Agricultural College inbred line 1,Jinyuan 45,Tianjin Agricultural College inbred line 3,Jinyuanhei No.1,C34 restorer line and Jindao 777,as well as 16 cadmium-tolerant varieties of iron stalks Wutai,Taishannuo,Lucai,Nanxiong,Willow leaf sticky,short feet early,fragrant rice,Zhuzhen B,Qingsi’ai 16 B,dry hemp rice,japonica 7623,Liusha No.1,Meihuanuo,Tiannongjing 518,C2106 restoration line and Tianjin Agricultural College inbred Line 2.2.Classify cadmium tolerance of 30 rice materials after cadmium stress,and divide rice into ordinary rice varieties and cadmium-tolerant rice varieties.The qualitative and quantitative analysis of small molecule metabolites by gas chromatography-mass spectrometry showed that there were significant differences in the types and contents of metabolites between ordinary rice varieties and cadmium-tolerant rice varieties,mainly reflected in organic acid metabolites.3.Principal component analysis（PCA）of unsupervised analysis of two types of rice seeds can not separate the two types of varieties well,and the use of supervised partial least squares discriminant analysis（PLS-DA）can separate the two types of rice The seeds are clearly distinguished.According to the VIP value（projection variable weight value）,T test（t-test）and cluster heat map analysis（HCA）of two types of rice seed metabolites,the two types of seed can be effectively distinguished.The metabolites that distinguish two types of rice seed are three organic acids（malonic acid,mandelic acid,9,12-linoleic acid）and one alcohol（Dmannitol）,of which the most obvious difference is D-mannitol.3.According to the analysis of the one-dimensional spectrum of rice varieties,the peak time of 30 rice is basically the same,and the peak wavelength is 1012 cm-1,1744 cm-1,2320cm-1,2848 cm-1,2912cm-1,4732 cm-1,5168 cm-1,5676 cm-1,6796 cm-1,and 8304 cm-1,the absorption peaks in this band represent the main groups that constitute proteins and starches,and Cadmium mainly produces complexes with starch or protein to produce toxic effects in plants,which is the feasibility basis for using infrared spectroscopy to judge rice cadmium tolerance.5.Utilizing The Unscrambler 10.5 to perform principal component analysis（PCA）on the near / mid-infrared spectra of 30 rice seed.The PC1 and PC2 factors in the near-infrared spectrum accumulated up to 99%,and the PC1,PC2 and PC3 factors in the mid-infrared spectrum accumulated up to 99%,so the principle component analysis method can be used to classify and discriminate the spectrum of rice seeds.One-dimensional principal component analysis of 30 rice seeds revealed that near / mid-infrared spectroscopy data can partially distinguish two types of rice seeds,of which near-infrared spectroscopy PC1 can roughly distinguish the two types of rice seeds,and mid-infrared spectroscopy PC2 can The two types of rice seeds are roughly distinguished,but individual samples still need to be judged further.Using 2Dshige to draw 2D correlation synchronous spectrum,2D correlation asynchronous spectrum and self-phase spectrum of indistinguishable samples,and using 2D method to accurately discriminate rice seeds,it can be concluded that the 2D synchronous spectrum of two types of rice samples There are fewer autocorrelation peaks on the diagonal,and there are more characterization information in the two-dimensional asynchronous spectrum,that is,the differences between the samples are large.Therefore,the combination of one-dimensional and two-dimensional analysis methods can better distinguish rice samples with different cadmium resistance characteristics.