| Banana (Musa spp.)is one of the four best fruits in Lingnan, and also the fourth major grain crops in the world. So banana industry has been developed into one of pillar industries. However banana industy had been affected for the spread of banana fusarium wilt. Fusarium wilt caused by Fusarium oxysporum f. sp. Cubense, is one of the most destructive plant diseases spreaded through the soil. Our research group found that if we added the cassava residue to the fermentation fertilizer, the number of banana growth promoting rhizobacteria increased, and that if we planted banana with the soil which rotated the cassava, the disease incidence(DI) decreased. Based on above great discover, we focused on the effects and mechanism of cassava in controlling of fusarium wilt through field trials, the pot and the laboratory experiments. The main results are following:1. The inhibitory effects of cassava extracts by the ethanol and water on the growth of FOC were researched in the laboratory. The results showed that:(1)the suppressed effect of FOC mycelium growth was best in50-100mg/L of the cassava underground extract by the ethanol or water in48h incubation time.(2)the inhibitory rate of spore germination was the highest at100mg/L of the extract, which are50.54%and47.34%respectively.(3)the inhibitory rate of the spore germination have differences significantly in the extracts of root, stem and leaf, and that the inhibitory rate of cassava roots extract by the ethanol and cassava leaves by water were the highest.2.The pot experiments inoculated with Foc4and irrigated extracts of cassava organ into the peat soil, were performed to identify the influence of the extracts of cassava organ on the growth and the DI. The results showed that:(1)the plant height and stem diameter in treatments irrigated extracts of cassava root and leaf were significantly higher than that in treatments irrigated stem extract and water, while the DI was significantly lower.(2)leaf areas had significant differences in the four treatments, and had a tendency of Leaf> root> stem> water.(3)SPAD value and leaf number had no difference.3.The treatwill test was performed to survey the allelopathic effect of extracts of cassava root exdudates, soil extracts of rhizosphere and non-rhizosphere on FOC. The results showed that the inhibitory rate of mycelial growth and spore germination of cassava root exdudates are32.17%and48.98%respectively, rhizosphere soil are15.54%and23.68%respectively, non-rhizosphere soil are6.71%and4.14%respectively.4. The field trials were performed to research the effects of different years of cassava rotation on soil disease suppression in the plantation planted banana for12years, and the incidence rate of wilt disease in this plantation were90.4%. The results showed that:(l) rotation can significantly decrease the total number of fungi, the number of FOC, sucrose activity and bulk density, pH value and DI.(2)rotation can increase the number of soil bacteria, A/F value, B/F value and the activity of catalase, urease, and the content of available phosphorus and nitrate significantly. Further more, the longer the rotation years, the greater the effect.(3)if rotation is above three years, the number of FOC would decrease to the critical mass of banana wilt incidence.5. The field trials combined cassava straw-returning were performed to shorten the rotation ages of cassava-banana crop. The results showed that:(1)the cultivation can significantly decrease the number of culturable fungi, FOC, the total number of fungal and DI.(2) the cultivation can significantly increase the number of culturable actinomycetes, the total number of bacteria, the content of nitrogen, the B/F and A/F of cultured microbial.(3)the cultivation can significantly increase the content of available nitrogen and activity of soil urease and soil invertase, the plant height, stem diameter, leaf areas and SPAD value of banana. |
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