| Banana (Musa spp.) is an important economic crop, and also a staple food, ranking the fourth after rice, wheat and corn. At present, bananas are planted in about 127 countries and regions around the world. China is one of the birth places of banana and has a cultivation history of over 3000 years. In 2009, the planting areas in China are about 311,100 ha (4,666,500 Mu), and the yields are up to over 8.2 million tons, making China one of the main countries producing banana. Now, banana industry has been devolved into one of pillar industries and plays an important role in development of rural economy and in increase of farmer income.Fusarium wilt, one of the most destructive plant diseases, is caused by Fusarium oxysporum f. sp. Cubense. The disease has been spread in banana plantations in Asia, Africa, Austria, and tropical America. Since the disease has been widely spread, it caused a great loss around the world. Scientists around the world have worked hard on Fusarium wilt for many years and have made great progresses. Unfortunately, effective control measure has not been found and widely applied in banana commercial production. However, an effective way to control the fetal disease by rotating bananas with Chinese leek (Allium tuberosum) has been widely used in commercial production of banana in Panyu area, Guangzhou, China. The Chinese leek-banana rotation system efficiently decreased the disease incidence (DI) and disease severity index (DSI). Based on the great discovery, we focused on the effects and mechanism of Chinese leek on control of Fusarium wilt by combinating field trials, artificial inoculation of potted banana in greenhouse and the laboratory experiments. The main results are followings:1. Field trials were carried out between 2006 and 2009. The results showed that average Fusarium wilt incidence of Baxi (AAA) and Guangfen No.1 (ABB) in the fields where Chinese leek had been commercially grown for 2-3 years were 1.7% (52.0% in control) and 2.7%(36.7% in control) in the first year, respectively. In 2007, the DI and the DSI of Guangfen No.1 (ABB) rotated with Chinese leek were reduced by 96.6% and 96.7%. In 2008, the DI and the DSI of Guangfen No.1 (ABB) rotated with Chinese leek were reduced by 92.3% and 94.2%. In 2009, the DI and the DSI of Guangfen No.1 (ABB) rotated with Chinese leek were reduced by 88.4% and 91.2%. None of the over 2,500 Baxi (AAA) plants intercropped in the fields where Chinese leek had been grown for 2 years were infected and showed visible symptom. And the control effect was 100%.2. Three rounds trials of potted banana planted in peat soil inoculated with Foc4 or the field soil naturally inoculated with Foc were performed in greenhouse to identify the effects of Chinese leek on the control of Fusarium wilt disease. In the first round trial, the suppression incidence of DIS in potted Baxi(AAA) planted in peat soil treated by leave pieces of Chinese leek was 86.9%, and that in Guangfen No.1 (ABB) planted treated by leave pieces of Chinese leek was 93.4%. The second round trial, the suppression incidences of DIS in Baxi (AAA) planted in the peat soil treated by leave pieces of Chinese leek and crude extract of Chinese leek were 54.4% and 63.6%; and those in Guangfen No.1 (ABB) planted in peat soil treated by leave pieces of Chinese leek and crude extract of Chinese leek were 75.0% and 62.5%. In the field soil naturally inoculated with Foc, the suppression incidences of DIS in Baxi (AAA) treated by leave pieces of Chinese leek and crude extract of Chinese leek were 78.6% and 64.3% and those in Guangfen No.1 (ABB) treated by leave pieces of Chinese leek and crude extract of Chinese leek were 44.4% and 66.7%; In the third trial, in the peat soil artificially inoculated with Foc4, the suppression incidences of DIS in Baxi (AAA) and Guangfen No.1 (ABB) treated by leave pieces of Chinese leek were 61.8%?80.7%, and in the field soil naturally inoculated with Foc, the suppression incidences of DIS in Baxi (AAA) treated by leave pieces of Chinese leek were 81.1%.3. The inhibitory effects of crude extract of Chinese leek on the growth of Foc4 were studied in the laboratory. The results showed that 10% of the crude extract of Chinese leek suppressed the growth of Foc4 mycelium by 64.6% on the Petri dishes. Chinese leek greatly damaged the structures of Foc4 mycelium. Various concentration of crude extract of Chinese leek significantly suppressed the germination of Foc4 spores. The concentration of 10% can completely suppressed the germination of the spores. The co-culture of Foc4 and the crude extract of Chinese leek on the shaking table suggested that in the PDA culture system,30% of crude extract of Chinese leek can suppressed the proliferation of Foc4 spores by 91.2%, and caused the spore death by 87.0%; And that in the water culture system,,low concentration of Chinese leek extract can increase the proliferation of the spores in some extent.The lethal incidence was 98.6%.4. The microorganisms and enzyme activity in rhizosphere soil of banana plants treated by Foc4 or Chinese leek were also studied. The results showed that Foc4 little affected total amount of the microorganisms and bacterial, but significantly increased the amount of the fungi by 2.72 times. The amount of actinomycete decreased by 42.29%, the ratio of bacterium and fungi (B/F) decreased by 89.58% and the ratio of actinomycete and fungi (A/F) decreased by 89.41%. Chinese leek significantly increased the amount of the microorganism in the rhizosphere soil of banana plants inoculated with or not inculcated Foc4. Without the existents of Foc4, Chinese leek treatment increased the total amount of microorganism by 277.70 times, bacterium by 288.72 times, fungi by 2.85 times, actinomycete by 2.14 times, B/F by 575.10 times; In the condition of inoculation with Foc4, Chinese leek Chinese leek treatment increased the total amount of microorganism by 314.82 times, bacterium by 347.18 times, fungi by 3.17 times, actinomycete by 1.65 times, B/F by 81.28 times; In addition, Chinese leek also significantly increased the enzyme activities in the rhizosphere soil of banana plants such as catalase, polyphenoloxidase, phosphatase, invertase, urease and cellulose. |
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