小麦黑胚病籽粒黑变物质的理化性质分析

Analysis of Physical and Chemical Properties of Blacken Substance from Diseased Wheat Kernels of Black Point

黑胚病是危害小麦生产的重要籽粒病害。为了解小麦黑胚病症状产生的原因,用碱溶酸沉的方法提取感黑胚病籽粒黑变部位的物质(黑变物质)与健康籽粒相同部位提取物(BPF)以及致病菌麦根腐平脐蠕孢(Bipolaris sorokiniana)的胞内黑色素与胞外黑色素,并对其进行紫外-可见吸收光谱、红外光谱扫描以及光、热稳定性等理化性质分析。结果显示:(1)病粒黑变物质的紫外吸收峰(235 nm)与B.sorokiniana的胞外、胞内黑色素的紫外吸收峰不一致(210 nm),而与BPF的紫外吸收峰相同;(2)病粒黑变物质与BPF的红外光谱一致,而与B.sorokiniana的胞外、胞内黑色素不一致;(3)病粒黑变物质与BPF的光、热稳定性较差,而来源于B.sorokiniana的胞内、胞外黑色素相对稳定。综上所述,黑胚病籽粒的黑变物质与致病菌B.sorokiniana的黑色素的理化性质有较大差异,而与健康粒相同部位提取物的理化性质类似,推测该物质是由小麦籽粒本身合成,而不是来源于病原真菌。

Black point is a severe kernel disease in wheat production. To understand the causes of symptoms on diseased kernels of black point,the blacken substance from black point-affected kernels,the substance from the same part of black point-free kernels(BPF),and intracellular melanin and extracellular melanin of the pathogen causing black point(Bipolaris sorokiniana) were extracted by the method of alkali dissolution and acid precipitation. The ultraviolet-visible(UV-Vis) spectroscopy,fourier transform infrared(FT-IR) spectroscopy,photostability and thermal stability of these samples were analyzed. The results showed that the UV-Vis absorption peak of the blacken substance was at 235 nm,which is the same as the sample from BPF,but different from the intracellular and extracellular melanin from the pathogen B.sorokiniana(210 nm). The FT-IR spectroscopy properties between blacken substance and the sample from BPF kernels were very similar to each other. However,spectroscopic properties of extracts from wheat kernels were different from those of the melanin from B.sorokiniana. Photostability and thermal stability of the blacken substance were poor,which are consistent with the sample from BPF,while photostability and thermal stability of the melanin from B.sorokiniana were relatively good. These results indicated that physical and chemical properties of blacken substance from the diseased wheat kernels were different from the melanin from B.sorokiniana,which suggested that the blacken substance was not come from fungi,but from the wheat kernels.