| Banana is one of the most important fruit in the word which not only could be eaten but also could be appreciated,it was considered as the fourth food crop behind rice,wheat and maize by the FAO.But its production is seriously destroyed by Fusarium wilt,which was caused by the soil-borne fungal pathogen Fusarium oxysporum f. sp. cubense (Foc).Because of rapidly variation,strongly pathogenicity, high incidence and complex pathogenic mechanism,the pathogenic mechanism of pathogenic is still currently unknown.Therefore the process of resistance breeding is still not keep up with the variation speed of the pathogen. And also it was not effective to employ biology control to combant or manage disease.Fusarium oxysporum Fusarium oxysporum f. sp. cubense(Foc) comprises three races (Race 1、2 and 4) and 24 vegetative compatibility groups (VCGs).Banana production areas in China are mainly threatened by Race 1 and Race 4, which the former only infect Pisary awak but the latter infect both Pisary awak and Cavendish banana, its also cause serious blow to the banana industry. Therefore understanding the pathogenic toxin will be helpful for breeding resistant bananas.The hotspot research of banana fusarium wilt pathogenesis is the Foc strains of biosynthesis of mycotoxins, the secondary metabolites of Foc may the one of the main factors of pathopoiesia. So this study is about the ability of biosynthesis of mycotoxins and the relationship of pathogenic among the 24 different VCGs strains.The main results are as follows:24 different VCGs strains culture, mycotoxins extract and concentration analysis: Using rice culture medium to culture 24 different VCGs strains,extract and concentrate crude toxin after 28 days later,then detected Fusaric acid、Beauvericin and Enniatin B by HPLC-ESI-MS.As the results show that the concentration of Beauvericin is much higher than Fusaric acid and Enniatin B,the highest is up to 270 and 6000 times than Fusaric acid and Enniatin B.It is suggested that all the Foe strains can biosynthesis Fusaric acid、 Beauvericin and Enniatin B,and the Beauvericin became the most important mycotoxins.PCR amplify Fusaric acid、Beauvericin and Enniatin B biosynthesis related gene: According to the sequence of the Fusaric acid、Beauvericin and Enniatin B biosynthesis related gene,use Primer 5 design the primers,then PCR amplification,sequencing,finally use some Bioinformatics sofewares to alignment sequences and draw phylogeny trees.The results indicated that the homology among the three toxins biosynthesis related gene is up to 90%,it is correlate with the races and VCGs which the strain belongs to;The strains belongs to the same race can cluster together.and the sequences of the same VCG homology is cover 99%.Analysis the pathogenic of Race 4 to Brazil banana:Using PDB medium to culture Fusarium oxysporum Fusarium oxysporum f. sp. cubense race 4(Foc),then collect the spore suspension,and mix the spore suspension with soil,the finally concentration is 500cfu/g soil.After that plant Brazil banana seedings and counting the sick incidence.According to the statistics,all the seeding which infected with Race 4 has wilt symptoms,and the level of the symptoms is related with three toxin concentration. The strain which can synthesis three toxins and moderate concerntration has the highest pathogenic.The strains contain two high concerntration has the higher pathogenic than the ones only have one toxin.Therefore,we can conclude that the pathogenic of the Foc is regulated with the three toxins... |
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