The Response Of The Root Exudates In The Decreasing Of Fusarium Wilt Of Watermelon By Arbuscular Mycorrhiza Or Intercropping With Aerobic Rice

Watermelon (Citrullus lanatus (Trunb.) Matsum and Nakai) is an important fruit in the world. Wilt disease is the main obstacle to continuous cropping of watermelon, and usually results in stunted growth and low production in watermelon. Watermelon wilt disease is caused by soilborne pathogen, Fusarium oxysporum f.sp.niveum (FON). Our previous experiment showed that arbuscular mycorrhizal fungi (abbreviated as AMF) colonization obviously alleviated watermelon wilt disease. Intercropping system of watermelon/aerobically growing rice suppressed watermelon wilt disease. In addition, phenolic acids in root exudates of watermelon was an important allelochemicals. Amino acid and organic acid in plant root exudates were related to plant resistance. This study investigated the watermelon root exudates response to arbuscular mycorrhizal colonization and intercropped with aerobically growing rice against Fusarium wilt disease. It was elucidated that the mechanisms of suppression watermelon wilt disease by AMF colonization and intercropped aerobically growing rice on root exudates. The main results were summarized as follows:1. A rhizobox experiment, with aerobic rice under14CO2, investigate the assimilation of carbon (C) in rice root exudates transfer between rice and watermelon and the effect of AMF on assimilation of carbon (C) transferd from rice to watermelon. The results show that:no matter whether intercropping with aerobic rice or inoculated with AM fungi, root exudates always transfer to adjacent plants. Intercropping with aerobic rice or AM fungi inoculation, more root exudates of rice could be transfered to adjacent plants.2. Different agents we were used to extract phenolic acids of watermelon. Alkali extraction and acid precipitation respectively were used to extract phenolic acids o. The results show that:alkali extraction had lower recovery rate, which is24.32%in low phenolic acids concentration, which18.57%in high phenolic acids concentration. Using70%methanol,70%ethanol,70%alcohol as extracting agent to extract watermelon root exudates effect is poor, water as extracting agent is better. Using water culture method to extract watermelon root exudates can get rich kinds and high content, total phenolic acid is123μg g-1root FW. Rice root exudates extracted is also very rich, content is high, total phenolic acid was15.83μg g-1root FW.3. A pot experiment was carried out to study the effect of AM fungi inoculation and FON on composition and content of watermelon root exudates. The results show that:Compared to control, AMF inoculation can effectively reduce the incidence of Fusarium Wilt of watermelon, and inhibit the quantity of Watermelon Fusarium oxysporum in both rhizosphere and root. Inoculation of FON greatly improves the phenolic acid content of watermelon root exudates, AMF inoculation, coumaric acid content increased significantly, most of the remaining phenolic acid secretion decreased. When FON has been inoculated, inoculation of AMF could significantly reduce the content of most of phenolic acids. Compared with the contrast, inoculated with FON can greatly improve the watermelon root exudates of amino acids. Inoculation of both FON, and AMF secretion of amino acid and malic acid significantly reduced, secretion of succinic acid, oxalic acid decreased. Compared with the contrast, the FON inoculation significantly increased the amount of watermelon root exudation of organic acids.The result show that, FON inoculation increased watermelon root exudates of phenolic acids, amino acids, organic acids.Inoculation of AMF, regulate the secretion of root of phenolic acids, organic acids, amino acids, suppression of Fusarium wilt.4. A pot experiment was carried out to research the effect of intercropped with aerobic rice and FON on Composition and content of watermelon Root exudates. The results show that:Compared with monoculture, intercropping watermelon/aerobic rice significantly reduced the incidence of watermelon wilt disease rate, and inhibit the number of watermelon rhizosphere and root Fusarium oxysporum; compared with the control group, were inoculated with FON greatly improves the watermelon root exudates of phenolic acid content, increased phenolic acids such as p-coumaric acid, watermelon/aerobic rice intercropping, the majority of phenolic decreased. When inoculated with FON, watermelon/aerobic rice intercropping than monoculture decreased content of watermelon root exudates of phenolic acid. Compared with the control group, were inoculated with FON greatly improves the watermelon root exudates of amino acid content, and FON inoculation in watermelon/aerobic rice intercropping the amino acid content was no change in root exudates of watermelon. Compared with the control, the FON inoculation significantly increased the secretion of organic acids from roots of watermelon, watermelon/aerobic rice intercropping, most of the organic acid secretion decreased. When inoculated with FON, watermelon/aerobic rice intercropping than monoculture reduces the organic acid content of watermelon root exudates.In conclusion, FON inoculation caused watermelon disease and increased the content of phenolic acids, amino acids and organic acids in watermelon root exudates. AMF colonization and intercropped with aerobically growing rice regulated the secretion of phenolic acids, amino acids and organic acids by watermelon root and suppressed watermelon wilt disease.