Endophytic And Epiphytic Trichoderma Of Banana: Diversity, Population Structure And Biocontrol Activities With Banana Wilt

We chose two isolation media which can select Trichoderma spp from soil with high efficiency from five media.We isolated 187 Trichoderma spp from banana roots by the two select isolation media.There were 29 endophyte Trichoderma strains.Seven Trichoderma species were identified. There were T.asperellum,T.atroviride,T.virens,H,lixii,T.koningii, T.brevicompactum,T.aureoviride.Three distinct distributions of Trichoderma have been observed in the roots of bananas(Musa sapientum L.):The first one,T.asperellum and T.virens were found both inside and on the surface;the second,H.lixii,T.atroviride and H.koningii existed on the surface only,whereas the third,T.brevicompactum and T. aureoviride,could only be isolated from the inside.T.asperellum was the dominant species in epiphytes(60.7%) and endophytes as well(61.3 %).T.virens was the second largest population in the Trichoderma community of banana roots,the ratio of endophytes(10.7%) was lower than that of epiphytes(22.7%).For reveal the genetic distance and diversity of banana root trichoderma spp,we selected two AFLP primer pairs that can produce the most polymorphic fragments from six pair.The AFLP analysis revealed a high genetic diversity of Trichoderma with an interspecies polymorphism as high as 100%,aNei' s genetic distance of 0.2292-0.4035 and a Nei' s genetic identity of 0.6680-0.7952.The genetic diversity of endophytes of the two largest populations of Tricfloderma(T.asperellum and T.virens) was significantly lower than that of the epiphytes,which dominant that microenvironments of banana roots influence genetic structure of epiphytic and endophytic populations.By inoculation and micro-observation,we analyzed the distribution of endophyte Trichoderma in banana roots.The results showed that endophyte Trichoderma existed in the roots,stem and leaves.They grew inside and interval of banana cell and produced spores in the cells. Moreover,comparison was made between two inoculation methods:toothpick inoculation method and root injury method,we found that root injury method was more effective.Analyzed of antagonist activity of endophytes and epiphytes Trichoderma against Fusarium oxysporum f.cubense in vitro were carried out by the methods of dual-culture,bioactive metabolites test and micro-observation.Some T.asperellum and T.virens isolates displayed outstanding biocontrol ability;especial T.virens showed both forming distinct inhibition zones by metabolisms and inhibition of the growth of F.oxysporum by interaction of hyphae,moreover,they displayed outstanding antagonism ability in dual-culture experimence.By greenhouse experiment,we analysed the biocontrol ability of D21 and C6. We found that both of them could control the banana wilt effect that disease index declined from 37.15 to 19.55 and 25.25.Comprehensive study of this paper to prove that banana roots Trichoderma species were diversity,and the study results showed revealed that T.asperellum was dominant specie of banana roots.The genetic diversity of epiphyte Trichoderma was more abundant than endopyte Trichoderma,which in part revealed that the stable enviorment of inside banana slowed the evolution of Trichoderma,and in order to meet the variability of the soil environment that the epiphyte Trichoderma formed rich genetic diversity.Biocontrol experiments showed that endophytic virens C6 has a strong ability to control banana wilt,a better future.