浙江大学学报. 农业与生命科学版 (Jul 2015)
Seed identification between Sorghum halepense (a quarantine weed) and its closed species based on ultraviolet spectrum
Abstract
Sorghum halepense (L.) Pers is an important quarantine weed, which is native to the Mediterranean region, and now is considered as one of the ten worst weeds in the world. The species is mainly dispersed by seeds. Sorghum almum Parodi is also an important weed, and Sorghum bicolor (L.) Moench and Sorghum sudanense (Piper) Stapf are two cultivated plants. Due to their morphological similarity, it is difficult for entry-exit inspection and quarantine departments to properly and quickly identify the seeds of S. halepense from those of its closed species. Therefore, how to identify the seeds of S. halepense from those of its congeneric species is urgently needed.In this paper, seeds from the above four species were extracted with petroleum ether to get their extractions, which were analysed by ultraviolet (UV) spectrophotometer (Unicam UV540) to get 200 UV absorbance data within 200-400 nm with 1 nm slit and at a scan rate of 0.5 s. From these 200 absorbance data, the sensitive wavelengths whose absorbance data could be separated each other were firstly identified by SPSS 16.0 using oneway analysis of variance (ANOVA) . From these preliminarily-selected sensitive wavelengths, more sensitive wavelengths with high information load were further identified by principal component analysis (PCA) . With the absorbance data of these informative wavelength spectra in relation to four species, both cluster analysis and PCA were applied to produce a dendrogram and a two-dimensional scatter plot, respectively. In order to verify the effect of the informative wavelengths which were selected by one-way ANOVA and PCA, a spectrum chart, a dendrogram, a two-dimensional scatter plot from PCA were directly produced on the basis of the absorbance data corresponding to the 200 wavelengths.According to the above procedures, sixty-three wavelengths were preliminarily selected by using ANOVA. From these wavelengths, eighteen informative wavelengths from 283 to 300 nm with a step of 1 nm were identified by PCA. On the dendrogram, the scatter plot and the spectrum chart produced based on these eighteen informative wavelengths, the seed samples of S. halepense and its three congeneric species were well separated each other. All these three schemes were better than those on the basis of the absorbance data corresponding to the 200 wavelengths in the seed identification of these four Sorghum species.The above results indicate that the extraction scheme with petroleum ether, and the selected eighteen informative wavelengths by ANOVA and PCA, as well as the charts by cluster analysis, PCA, or directly based on absorbance data are effective to identify the seeds of S. halepense from those of S. bicolor, S. almum and S. sudanense.
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