Effect Of Allelochemical SA From Allium Tuberosum On Fusarium Wilt Of Banana (Musa Spp.) And The Soil Microorganism

Banana wilt caused by Fusarium oxysporum f.sp.cubense(FOC)is a devastating soil-borne disease causing extensive failure of commercial plantations of banana through out the banana producing areas of the world.In this paper,the inhibitory effects of SA on FOC were investigated,and reduced the effects of the disease stress on banana seedlings was studied by added SA in medium with toxic production from Fusarium oxysporum f.sp.cubense.The pot experiments of SA on FOC-Banana-soil system were measured which FOC,microbe and enzyme activities were tested.The results showed:SA presented strong inhibitory effects on FOC colony growth.The inhibition rate of S A on FOC with the concentration increased.The inhibitory rate could reach 1 00%when SA at the concentration of 600 ?L/L in the solid medium.Application of SA significantly reduced the conidia number of FOC,which was 470 times less than that of the control treatment.In liquid medium culture,with SA treatment,the liquid medium was colorless while without SA the medium turn to be purple color.PH would affect SA inhibition on FOC which low pH might benefit for SA inhibition on FOC.In treatment with crude toxin of FOC,the seedlings of Banana wilted severely.However,the treatments of additional application of SA significantly reduced the desease symptoms.This result showed that additional application of SA could reduce the toxicity from FOC to banana seedlings,indicating that additional application of SA significantly reduced the microconidium number of FOC and the production of mycelium and fusaric acid of FOC.In banana-soil system,low SA concentration did not significantly restrain FOC,however high SA concentration significantly did.Comparing to plate experiment,inhibition rate was lower in soil experiment with the same SA concentration.It might due to SA was easy to volatilize which resulted in decrease the concentration in soil over time.Additionally,soil is a complicated buffer medium which resulted in reducing the activities of SA.Therefore,it is important to develop appropriate methodology and technology on application SA in soil.Different concentration of SA affect soil microbial quantity and soil enzyme activities in banana-FOC-soil system.Low-medium concentration of SA could promote the growth of soil bacteria and fungi;and low concentration of SA could promote the growth of soil actinomyces,but medium concentration of SA could inhibit the growth of soil actinomyces.High concentration of SA inhibited the bacteria,fungi and actinomyces in soil this indicated that when concentration of SA reach a high concertation number microorganisms would reduce in soil.Different concentration of SA showed different effect on soil enzyme,which the trend of effect was similar among urease,invertase and acid phosphatase.Low concentration and medium concentration of SA could promote the activity of this enzyme,while high concentration of SA would inhibit their activity.Respectively,low concentration of SA could promote the activity of catalase and polyphenol oxidase,and with increasing SA concentration,this two enzyme activity decreased.Thus,high concentration of SA could reduce the activity of these five above enzymes in soil.Therefore,high concentration of SA retrained FOC but at the same time inhibited microorganism and enzyme activity.Therefore,how to establish a good soil environment and application method is the key to the application of SA.Consequently,although our study demonstrated that SA could significantly retrain FOC,however,it is important that technology of applying SA on soil which result in an effective and consistent SA concentration at root surface of banana,and which need to further study.