| Exotic plants can accumulate local pathogens in the introduced range, and this in turn can affect adversely the growth of native plants. Sometime pathogen can change to be endophyte during the growth of the invasive plant. When the exotic plants suffer relatively less from these local pathogens than the native plants, or the pathogens lose the pathogenicity while they transform into endophytes, pathogen accumulation will provide the exotic plants with an indirect advantage in competition with the natives. Pathogen or endophyte interacting with their host plant, commonly results in the fungi host plant coevolution. Ageratina adenophora usually engage in close biotic interactions with the local microbes, and the outcome of such interactions can contribute to invasive successfully. Recently, this has been attracting more and more attention, however, the reason for such mechanisms of biological invasion has been rarely well understood. Therefore, understanding the interaction of A. adenophora-fungus systems over geological space and time is important to interpret the principle of invasion and it can also be a theoretical reference to investigate the correlation among biodiversity and their ecological factors.According to our previous research works, in this study,13populations of A. adenophora in Yunnan and their endophytes and the pathogens of the local plants were subject to be explored. The genetic diversity of A. adenophora based on inter-simple sequence repeat(ISSR) technique and the haplotypes based on ITS gene of the foliar endophytes of A. adenophora and the pathogens of the local plants were compared, and the correlation of genetic diversity from the samples and their ecological factors were determined. Several conclusions were made as following:1. The haplotypes of the dominant foliar endophytes from A. adenophora and the foliar pathogens of some local plants are same.Totally,753from the883strains of fungi we isolated can be investigated. Among them,562strains of fungi are identified preliminary belong to Colletotrichum. They can be divided into59kinds of haplotypes. Two kinds of haplotypes, called as Haplotype177and Haplotype158, are the dominant and the strains all were identified as Colletotrichum gloeosporioides due with the specific sequence5’-GGGCGGGT-3’. There are142and112strains of fungi in Haplotype177and Haplotype158, respectively, and accounted for the percentage of the foliar endophytes from A. adenophora and the pathogens of the local plants both more than60%and20%, respectively. It suggested that these foliar endophytes may turn into pathogens when they are in local plants.2. The host range of the pathogens that belong to the dominant haplotype of the foliar endophytes isolated from A. adenophora is very wide.The hosts of the pathogens that belong to the dominant haplotype of the foliar endophytes isolated from A. adenophora can be Mangifera indica, Musa nana, Phaseolus vulgaris, Rhus chinensis, Nicotiana tabacum, Urena lobata, Clematis peterae, Gonostegia hirta, Dioscorea hemsleyi, Artemisia dubia, Alnus nepalensis and many other local plants. Such a wide range of host can further suggest that A. adenophora can accumulate local pathogens to promote its invision.3. The genetic diversity of A. adenophora, its foliar endophytes and the foliar endophyte Colletotrichum gloeosporioides decrease with the increasing of latitude, and all reached significant level(P=0.027,0.011,0.022). It can be suggested that there must be a closed relationship among them.4. The coevolution between A. adenophora and the dominant foliar endophyte Colletotrichum gloeosporioides is not obviously congruent.Comparising the dominant foliar endophyte fungus ITS phylogeny with the host ISSR phylogeny, we could not find completely congruence. Only the population of A. adenophora from Yuanjiang is far away from other populations in the clades, which correspond to the population of the dominant foliar endophyte from Yuanjiang. |
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