Interaction Analysis Between Watermelon Root Exudates And Fusarium Oxysporum F. Sp. Niveum

Watermelon Fusarium wilt is a worldwide soil borne diseases caused by infection ofFusarium oxysporum f. sp. niveum, occurring in all watermelon regions to varying degrees,which has become one of the main factors limiting the sustainable development ofwatermelon production at present. This study using the susceptible varieties BlackDiamond（BD）,Sugarbaby（SB）and zaojia8424(ZJ), the resistant varieties Calhoun Gray（CG）, Sugarlee（SL）, PI296341-FR（PI）, and Watermelon Fusarium oxysporum race1and race2as materials, analysis the difference of category and content of chemicalcompositions in root exudates and bleeding sap of test materials inoculated with pathogenor not, and researches the effect of root exudates of different resistant watermelon on thegrowth of Fusarium oxysporum by the technology of hydroponics and Gas Chromatograph–MassSpectrometer-compute(GC-MS). In order to find the effective composition thatinhibit the growth of Watermelon Fusarium oxysporum, which explicit correlation ofwatermelon root exudates and watermelon Fusarium oxysporum, and provides newtheoretical basis for the prevention and control of watermelon Fusarium wilt. The mainresults are as follows:1. GC-MS analysis showed that there were three class materials detected in plant rootexudates and bleeding sap of test materials. The first materials were detected in bothresistant and susceptible watermelon varieties, and the content changed when inoculatedwith pathogen, such as Dibutyl phthalate, Octadecanoic acid, Hexadecan acid, and so on.The second materials were detected in susceptible watermelon varieties, and the contentchanged when inoculated with pathogen, such as D-Mannitol,5-(Adamantyl-1) salicylicacid,1-Methyl-2-phenylimino-1,2-dihydroanthra[1,2-d]thiazole-6,11-dione, and so on. Thethird materials were detected in resistant watermelon varieties, and the contentchanged when inoculated with pathogen, such as2,6-dicyclopentyl-4-methyl-Phenol,1-Isobutylsulfanylmethyl-2,8,9-trioxa-5-aza-1-sila-undecane, and so on. Inoculationtreatment had no obvious effect on chemical compositions of root exudates, but it changedthe content of some compositions. Whether these substances have allelopathy on Fusariumoxysporum, need for further research.2. Root exudates of resistant varieties SL, PI and CG inhibited the mycelium growth, sporulation and conidial germination of Fusarium oxysporum f. sp. niveum race1.After inoculated with pathogen, the inhibition of plant root exudates had been enhanced,increased3.68%-14.07%,2.00%-29.78%,2.33%-17.57%. The inhibition of root exudatesof3-9d were more obvious, the inhibition rate reached40.52%-79.87%,12.77%-59.46%and13.51%-58.14%. The inhibition of12d began to decrease, but the inhibition ratedecreased less after inoculated with pathogen, which showed that inoculation treatment canmaintain more lasting inhibition of root exudates, and the difference was significant at themycelium growth.Root exudates of susceptible varieties ZJ and SB promoted the mycelium growth,sporulation and conidial germination of Fusarium oxysporum f. sp. niveum race1. Thepromotion of root exudates of3-9d were more obvious, the promotion rate reached31.79%-72.19%,21.18%-81.82%,15.38%-72.00%. After inoculated with pathogen,promotion of plant root exudates had been enhanced, increased2.89%-22.33%,4.55%-22.73%,11.54%-44.00%, and the difference was significant at the myceliumgrowth. The promotion of12d began to decrease, especially root exudates of plantinoculated with pathogen, the promotion rate were only5.96%and14.89%, whichprobably related to plant wilting.Root exudates of resistant varieties PI inhibited the mycelium growth, conidialgermination of Fusarium oxysporum f. sp. niveum race2. But the inhibition of rootexudates of watermelon resistant varieties on the growth of mycelium of race2was moreobvious. The inhibition of root exudates of3-12d showed a decreasing trend. Rootexudates of susceptible varieties CG and ZJ promoted the mycelium growth and conidialgermination of Fusarium oxysporum f. sp. niveum race2. But the promotion of rootexudates of watermelon susceptible varieties on the growth of mycelium of race2wasmore obvious.The promotion of root exudates of3-12d on the mycelium growth showed adecreasing trend.3. By the method of GFP marker, researching the infection process of race2inwatermelon root of both susceptible and resistant varieties, we found that race2couldinfect both susceptible and resistant varieties of watermelon. Compared with the resistantcultivar PI, the main difference was that race2in the root of susceptible cultivar BD canproduced a lot of conidia, and further infection aggravated, resulting in root collapse andplant wilting. But PI showed disease resistance. Both race1and race2could invaded intothe roots of CG, but the infection process of race2was slower than race1. The sporulationand conidia germination of race2was the key to the success of colonization, but race1didnot show this feature, which showed that The infection characteristics of different strainswere different.