Resistance And Its Mechanisms In Potato Tuber Slices Against Late Blight Induced By Some Microbial Extracts

Potato is one of the world's four major crops; China is one of the world's largest production bases of potato. Potato has an important status in the world crop production, and 2008 has been named as the "International Year of the Potato" by UN. Some fungal diseases have threated potato production, especially potato late blight, resulting in serious yield losses and even no harvest. Artificially induced resistance is a new technology with the characteristics of safe, efficient, broad-spectrum and persistence. It is conducive to opening up a new method of plant disease control because of its fundamentally improvement and enhancement to resistance. Moreover, in recent years the induced resistance to potato late blight by plant extracts, physical factor, chemical, fungal and bacterial extracts has been reported successively. But there was little knowledge about elicitor extracted from actinomycosis and complex elicitor that could induce resistance in potato to late blight.The effect and mechanism of the induced resistance in potato by actinomycetic extracts and mixture of two kinds'microbial extracts were preliminarily researched in this article. The main results were obtained as follows:1. We obtained fermented filtrates (F-0), intracellular component (F-1), and cell wall (F-2) and their mixture as elicitors, which were used for inducing potato tubers.9 kinds of microbial elicitors and 5 kinds of complex elicitors with inducing efficiency of up to 50% were acquired. The effectiveness of MK-F-0, A32910b-F-0 and A5295-F-0 was 60.42%, 63.97%, and 56.25%, respectively. The effectiveness of 5 kinds of complex elicitors (A5295 (F-0)+F32 (F-0),A5295 (F-0)+A32910b (F-0),Wf3 (F-2)+F32 (F-2),F32 (F-2) +M102 (F-2) and F32 (F-0)+A32910b (F-0)) is preferable, and the MK F-0+A5295 F-0 has the best induced efficiency which was 66.67%,better than that of single elicitors.2. After preliminary assay on the active inducing substance that were got from highly efficient fermented filtrates (MK F-0 and A32910b F-0) through the method of ammonium sulphate and ethanol depositing, we found that they were similar because they existed in the component that is ammonium sulphate depositing (A component) or ethanol depositing after that (B component). The active material's molecular weights is bigger than 8000-10000KD, so it is likely to be protein, polysaccharide, lipin etc.3. We found the activities of resistance-related enzyme POD, PAL and PPO in potato tubers were significantly enhanced by the induction of microbial extracts. With A5295 fermentation treatment, activities of POD, PAL and PPO were 250.40%,275.14%, and 27.88%, respectively, compared with control at 5d after treatment and reached the peak value rapidly before representation of resistance.4. Change of soluble protein in the potato tubers was analyzed after induction. The potato tubers induced had 41.53% more than the contrast and produced some new proteins. The new proteins' molecular weights is lower than 100 KD and three of them is lower than 40 KD.The new protein's appearance was followed with the increase of resistant-interrelated enzyme activity, so they could have resistant-interrelated enzyme activity and may be PR protein.Obviously, it is potential that elicitor extracted from actinomycosis induce resistance in potato against late blight. The appliance of complex microbial extract in inducing resistance to potato late blight also has a good prospect because of its improvement in inducing efficient.