| Changes of disease incidence and disease index of root rot in different rootstock varieties of pepper were investigated by manual inoculation, with'Chifengtexuan'(Pepper annuum L. var. Grossum Bailey) as control. The purpose is to screen a rootstock variety which has higher resistance to root rot. The effect of grafting on root rot resistance in pepper and its mechanism were studied, with the higher resistance to root rot of pepper as rootstock, and the own-root plant as control. The results were as follows.1.'Weishi'was diseased in later days, and showed the lowest disease incidence and disease index, therefore represent the highest disease resistance among the four rootstock varieties,'Buyeding'next,'Tiemuzhen'and'graft'had the lowest resistance.2. Effect of graft on root rot resistance of pepper were investigated, with'Chifengtexuan'scion grafted onto'Weishi'rootstock. The own-root plants was act as a control. The result showed that grafted plants showed remarkable lower disease incidence and disease index than control plants, but higher than rootstock plants. This indicated that rootstock and scion were interfered in each other.3. Rootstock and grafted pepper showed higher absorption area and absorption quantity in nitrogen, phosphorus, and potasium, compared with those of CK. This indicated that higher absorbency of grafted pepper was one of the important reasons of higher root rot resistance.4. The activity of POD, CAT and PPO in roots and leaves of pepper increased rapidly after be inoculated. 5~10 d later, POD and CAT activity decreased. Graferd plants showed an increase in activitis of POD, CAT and PPO, compared with control. These data indicated that graft increased activity of antioxidtion enzymes, inhibited production and accumulation of free radicals and reactive oxygen, therefore increased the disease resistance.5. Before inoculation, rootstock and grafted plants showed significantly higher soluble sugar content and PAL activity in roots, but lower solube sugar content and PAL activity in leaves, compared with control. Similar phenolic compounds and lignin contens were found in roots and leaves of rootstock, grafted and control plants before inoculation. The soluble sugar content in roots of rootstock, grafted and control plants decreased gradually after inoculation, PAL activity, contents of phenolic compounds and lignin increased at earlier stage, but trended to stabilize or decrease 10 days later. Rootstock and grafted plants showed significantly higher PAL activity and contents of phenolic compounds and lignin in roots and leaves than control plants. Soluble sugar content in roots of rootstock and grafted plants also higher than that of control plants, but lower in leaves than control plants. These data indicated that graft significantly increased the root rot resistance in pepper, and is closely related to the increase in phenylaprapanoid metabolism.6. The actinomyces population and ratio, activities of dehydrogenase, peroxidase and catalase in rhizosphere soil of rootstock and grafted peppers increased significantly, compared with those of control before inoculation. After be inoculated, rootstock and grafted peppers had significant higher quantities of bacterium, fungus and actinomyces, actinomyces ratio, and soil enzymes'activity, in comparison with control. The quantitiy of microoganism, ratio of actinomyces, and enzymes'activity in rhizosphere soil of grafted pepper are important reasons of enhancement of root rot resistance.7. The ether extracts of the root exudates were detected by GC-MS. The results showed that, the categories and the relative of graft seedings contents were different from the own-root seedings. And the root exudates of graft seedings have higher content of esters and phenolic compounds. Key words: Pepper; Rootstock; Graft;Root rot Resistance... |
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