Effects Of Arbuscular Mycorrhiza On Watermelon Fusarium Wilt In Aerobic Rice And Watermelon Intercropping System

Watermelon is such a popular fruit through the year that it has high consumption and big planting areas in China. Since the limited cultivatable field, watermelon has to be cultivated continuously. However, continuously cropped watermelon is susceptible to Fusarium wilt disease, which caused by pathogenic fungus F oxysporum f. sp. Niveum. Watermelon wilt disease caused yield reducing, quality declining and peasants'income decreasing greatly. Intercropped with aerobic rice or inoculated arbuscular mycorrhizal fungi (abbreviated as AMF) can suppress Fusarium wilt of watermelon. Both of them are used in planting watermelon have not been reported. Experiments were designed to study the effects of the mycorrhizal colonization on watermelon Fusarium wilt in the aerobic rice and watermelon intercropping system to find the better way on biologically controlling Fusarium wilt of watermelon in continuous cropping system. The results obtained are listed as followed.1. Pot experiment that the aerobic rice was inoculated either of two kinds of AMF, Glomus etunicatium Nicolson & Schenck (abbreviated as G.e) and Glomus clarum Becker & Gerdemann (abbreviated as G.cl), was carried out in monocropping system or aerobic rice/watermelon intercropping system. The results showed that the frequency and intensity of G.e mycorrhizal colonization on the aerobic rice was higher than that of G.cl, respectively. Irrespective of G.e or G.cl, the mycorrhizal frequency and intensity was higher in intercropping system than that in monocropping system. The dry weight of aerobic rice was increased significantly by G.e colonization, while it was deceased significantly by G.cl colonization in monocropping system. The similar results were shown in aerobic rice and watermelon system. So G.e was selected as the material of further research.2. Rhizobox separated by nylon mesh, inoculated with AMF G.e or Glomus intraradices Becker & Gerdemann (abbreviated as G.i), to the aerobic rice or watermelon seedlings in soil or sand medium, was carried out to investigate the formation of arbuscular mycorrhizal hyphal linkage between aerobic rice and watermelon, which effected expression of OsPT11 and P acquisition. The results obtained are listed as followed. (1) When neither aerobic rice nor watermelon was inoculated with AMF, none mycorrhiza colonized, OsPT11 which specially induced by AMF did not express. (2) Hyphal linkage between aerobic rice and watermelon induced OsPT11 expression when only watermelon was inoculated with AMF. (3) Both inoculations directly and by hyphal linkage were colonized at the equivalent mycorrhiza. The frequency of colonization on aerobic rice and watermelon were more than 80% and more than 70%, respectively. (4) The available phosphorus in the mycorrhizal rhizosphere of aerobic rice and watermelon were more than that in non-mycorrhizal rhizosphere. The phosphorus content in rice was decreased by mycorrhizal colonization, while it was increased in watermelon, compared to that in non-mycorrhizal treatments. (5) The hyphal linkage could be formed between aerobic rice and watermelon by G.i in sand medium and by G.e in soil medium, respectively. The equivalent frequency and intensity were detected in aerobic rice by inoculations directly or by hyphal linkage when inoculated by G. i in sand medium.3. The pot experiment was carried out to study the effects of G.e and G.i on Furasium wilt of watermelon. The results showed that the mycorrhizal frequency of watermelon was more than 90% and the mycorrhizal intensity of watermelon were about 50% when inoculated by either G.e or G.i. The biomass of watermelon inoculated by G.e was increased significantly while quantities of Furasium oxysporum and fungi were decreased in watermelon rhizosphere, the frequency and disease index of Furasium wilt of watermelon were declined, and quantities of bacteria, actinomycete and total microbiology were decreased significantly. However, watermelon inoculated by G.e could not counteract the effect of Furasium oxysporum on its tendril length, and quantities of bacteria and total microbiology. Watermelon inoculated by G. i had no effects on the quantities of Furasium oxysporum, bacteria, fungi and actinomycete and the frequency and disease index of Furasium wilt, except increasing quantity of total microbiology in watermelon rhizosphere. Different effects were detected on the growth and Furasium wilt of watermelon by different AMF, and microbiology in its rhizosphere. Watermelon inoculated by G.e can decrease Fusarium wilt disease but can not counteract the effects of Fusarium oxysporum on it.4. The experiment was carried out to study the effects of watermelon inoculated by G. e or G. i on Fusarium wilt of watermelon in aerobic rice and watermelon intercropping system. Mycorrhizal frequency and intensity of aerobic rice by G.e were similar to those by G.i, mycorrhizal frequency of aerobic rice by either of them was more 70%, and mycorrhizal intensity was about 30%. Mycorrhizal frequency and intensity of watermelon by G.e are similar to those by G.i, mycorrhizal frequency of watermelon by either of them was more 80%, and mycorrhizal intensity was about 30%. Two kinds of AMF could colonize aerobic rice and watermelon easily and the hyphal linkage could be formed between the two plant. Inoculating G.e or G.i decreased significantly the quantity of Furasiu oxysporum and fungi, the frequency and disease index of Furasium wilt, while increased the quantities of bacteria, actinomycete and total microbiology in watermelon rhizosphere. Different kinds of AMF had the same effects on growth and Furasium wilt of watermelon and microbiology in its rhizospherre. Inoculating AMF did not decrease the effect of Fusarium on watermelon biomass, but decreased the frequency and disease index of watermelon Fusarium wilt and counteract the effects of Furasium oxysporum on microbiology in watermelon rhizosphere.