陆地棉植株组织结构和生化代谢与黄萎病抗性的关系

Relationship of Verticillium Wilt Resistance with Plant Anatomical Structure and Biochemical Metabolism in Upland Cotton

通过对8个陆地棉品种的植株组织结构、酶活性和根系分泌物的比较分析,研究陆地棉黄萎病抗性机制。研究结果表明,陆地棉抗病品种根和茎的导管细胞壁厚、直径小、数目多,髓射线数目多、单位面积薄壁细胞数多,有助于抵御棉花黄萎病菌的侵入与扩展。过氧化物酶(POD)活性与棉花抗黄萎病的关系不明显,但苯丙氨酸解氨酶(PAL)活性与抗病性有密切的关系。感病品种根系分泌物中的氨基酸种类多、含量高。与之相比,抗病品种根系分泌物中少了天门冬氨酸、苏氨酸、谷氨酸、丙氨酸、异亮氨酸、亮氨酸、苯丙氨酸、赖氨酸和脯氨酸等9种氨基酸酸,多了精氨酸。不同抗性的陆地棉品种根系分泌物中糖类物质种类相同,但感病品种的葡萄糖、果糖和蔗糖含量均显著高于抗病品种。

Verticillium wilt is an important disease in the world, and it threatens the development of cotton production seriously. Since 1980' s, this disease has become more and more serious in China, especially in 1993 when a disaster broke out all over the main cotton production regions in China, which led to a huge economic loss caused from the decrease in the cotton yield and quality due to the disease, and it has threatened the cotton production in China greatly. It is useful to study the mechanism of cotton resistance to Verticillium wilt for the resistant cotton breeding and the integrated controlling. In this paper, the mechanism of cotton resistance to verticillium wilt was studied via the comparative analysis of the plant anatomical structure, enzyme activity and root exudates in the plants at the different time after inoculation with Verticillium dahlias , an Anyang strain with intermediate virulence, using 8 upland cotton cultivars with different level of the disease resistance as the materials. The results showed that there were more pith rays, xylem parenchyma cells, and vessels with thicker wall and smaller diameter in stems and taproots of the resistant upland cotton cultivars, comparing with that of susceptible ones (Table 1), which may conduce to the plant resistance to the infection and spreading of Verticillium dahliae. The relationship between the POD activity and verticillium wilt resistance in the upland cotton cultivars was not obvious at the different time after inoculation ( Fig. 1) , but the PAL activity was increased in the disease resistant cultivars much more greatly after inoculation than that in the susceptible cultivars. After reached the peak value, the descent rate of PAL activity in resistant cultivars was much less than that in susceptible ones, and the high level of PAL activity was hold longer in resistant cotton cultivars than that in susceptible ones as well (Fig. 2) . The amino acids in the root exudates of resistant cultivars were much less than that of susceptible ones. Compared with susceptible cultivars, there were lack of aspartic acid, threonine, glutamic acid, alanine, isoleucine, leucine, phenylalanine, lysine and proline in the root exudates of resistant cultivars, but arginine that was lack in the susceptive cultivars on the contrary ( Table 2) . The saccharide types in the root exudates were no difference between the two kinds of cultivars, but the contents of glucose,fructose and sucrose in the root exudates of susceptible cultivars were much higher than those in resistant ones (Table 3) . The results indicated that the character of PAL activity expressed after inoculation with Verticillium dahliae, as well as the kinds and contents of araino acids and soluble sugars in the root exudates can be used as the important biochemical criterions in the judgment of cotton cultivar resistance to Verticillium wilt.