Genetic Diversity Among Fusarium Oxysporum F.sp. Cubense Isolates On Banana In China

In China, banana is one of the important tropical and subtropical fruit, the acreage and production being 350,000 ha and 9,000,000 tons in 2009.Fusarium wilt of banana or Panama disease caused by the filamentous fungus Fusarium oxysporum f.sp. cub ens e (FOC) is one of the most devastating deseases of banana, distributing on many banana growing areas in the world. Fusarium wilt comprising four Races differentiated by host plant reactions, the four Races are Race 1, Race 2, Race 3 and Race 4. Race 1 and Race 4 were determined in China. A long ago have Racel, and Race 4 found in Taiwan province in 1967, invasion to Guangdong province in 1996, after that rapidly invasion into other banana growing areas.In the present study, Several scholars identify of pathogen causing Fusarium wilt of banana from Fujian, Hainan, Guangdong and Guangxi provinces in China, respectively. Massive collection FOC isolates and studies pathogenicity differentiation from banana growing areas in China was haven’t seen reported. Domestic and foreign have not seen report about use of ISSR marker in detection of genetic variation among Fusarium oxysporum f. sp. cubense Isolates on Banana.According to massive collection FOC isolates in China, by root scratching inoculation method identify of pathogen and pathogenicity differentiation causing Fusarium wilt of banana. Use of ISSR marker in detection of genetic variation among FOC isolates. The primary results of the dissertation are summarized as follows:1. Collection FOC isolates and identifyDuring December 2001 to January 2010, we have got virulence of 114 F. oxysporum f. sp. cubense isolates from the 44 cities of Fujian, Guangdong, Guangxi, Hainan and Yunnan provinces. By root scratching inoculation method vaccination Brazil Xiangjiao or Fenjiao assessed the virulence of 114 isolates. The selected isolates are apparently showing the virulence, which cause disease,57 isolates is Race 1, host is Fenjiao; 57 isolates is Race 4, Brazil Xiangjiao, Fenjiao and Aigan Gongjiao is 43,13,1, respectively. 2. Pathogenicity differentiation of FOCBy root scratching inoculation method vaccination Brazil Xiangjiao of 57 isolates Race 1 or Fenjiao of 57 isolates Race 4 assessed the virulence.57 isolates Race 1 the strong pathogentic type is 32, the middle pathogentic type is 23 and the the weak pathogentic type is 2.5 provinces primarily to strong pathogentic type.57 isolates Race 4 the strong pathogentic type is 29, the middle pathogentic type is 9 and the the weak pathogentic type is 19, Fujian, Guangdong, Guangxi and Hainan provinces primarily to strong pathogentic type, from Yunnan province’s 2 isolates is weak pathogentic type.3. Select ISSR primers and optimize the ISSR-PCR reaction systemFrom 33 ISSR primers select the eight primers, UBC801、UBC811、UBC825、UBC826、UBC827、UBC835、UBC856 and UBC889, respectively. The uniform design was used to optimize the ISSR-PCR reaction system for FOC, which involved 5 factors (Taq DNA polymerase, template DNA, dNTPs, ISSR primer and Mg2+), each at 5 levels. An optimal 25μL reaction system of ISSR-PCR involved 5 factors was 0.03 U/μL、0.01ng/μL、0.8 mM、0.4 mM、2mM, respectively.4. Genetic variation of FOCGenetic variation of 95 isolates of Fusarium oxysporum f. sp. cubense and 1 isolate Fusarium oxysporum f. sp. niveum (FON) from China using ISSR molecular marker analysis, based on the Nei’s standard genetic distance is 0.57-1.00.96 isolates were grouped into six clusters (A, B, C, D, E, F) based on ISSR analysis using a genetic distance threshold of 0.68, the proportion of 51.06%,39.58%,5.20%,2.08%,1.04%,1.04%, respectively. The cluster A was further divided into two sub clusters (AⅠ, AⅡ), contains 48 FOC isolates and one FON isolate, Fenjiao primarily to host, Racel primarily to Races. The cluster B contains 5 isolates, all host is Fenjiao, Race 4 is all. The cluster C contains 2 isolates, one is FOC163-F-1-M, Fenjiao, Race 1; other is FOC150-B-4-W, Brazil Xiangjiao, Race 4. The cluster D was further divided into two sub clusters (DⅠ,DⅡ), contains 38 isolates, Brazil Xiangjiao primarily to host, Race 4 primarily to Races. The cluster E contains FOC246-B-4-M isolate, Brazil Xiangjiao, middle pathogentic type of Race 4, from Bolian town, Lingao county, Hainan province. The cluster F contains FOC165-B-4-W isolate, Brazil Xiangjiao, weak pathogentic type of Race 4, from Chenhai county, Shantou city, Guangdong province.The high levels of genetic variation among the FOC isolates, FOC had rich ISSR sequences, there was correlation between host. Races of the pathogen and their ISSR clusters. But there was little correlation between virulence, geographical origin of the pathogen and their ISSR clusters. Genetic variation in FOC might be due to adaptation and co-evolution of the fungus with the host and environmental factors of the location. Isolates FOC246-B-4-M and FOC165-B-4-W may be new variation, new afferent or single mutation.