| In recent years, biological invasion has been the social and ecological problem. Since the Ageratina adenophora has invaded into Yunnan province, China, in1940s, it has expanded fast into other regions and has set up a large number of populations. However, it still hasn’t been unclear for the mechanism of alien species invasion. In order to study the characteristics of the invasion of A. adenophora, the experiment was designed and performed, based on the hypothesis’’accumulation of local pathogens", to explain the interaction relationship between the A. adenophora and surrounding native plants from the perspective of foliar endophytic fungi.Different endophytic fungi previously isolated from A. adenophora were used to infect the seeds of different native plants, and then cultured in greenhouse to observe the seed germination rate and plant growth. Totally51strains, including26strains from Colletorichum,20strains from Alternaria.2strains from Axylaria, and3strains from Phomopsis were selected. Test plants included herbs Ageratina adenophora, Achyranthes aspera, Isachne globosa, and Amaranthus caudatus; vines Zehneria maysorensis and Polygonum multiflorum; shrub plants Urena sp., Sida acuta, and Abelmoschus moschatus.The following results were concluded:1. Most of foliar endophytes of A. adenophora have pathogenicity on native plantsAmong of those strains tested, Alternaria can infect7plants, including A. adenophora, Ac. aspera, I. globosa, Am.caudatus, P. multiflorum, Z. maysorensis and Ab. moschatus: Colletotrichum can infect8plants, including A. adenophora, Ac. aspera, I. globosa, Am. caudatus, P. multiflorum, Z. maysorensis, U. sp., Ab. moschatus; Phomopsis can infect6plants, including A. adenophora, Ac. aspera, I. globosa. Am. caudatus, P. multiflorum, and Zehneria maysorensis; Xylaria can infect5plants involving A. adenophora, P. multiflorum, Z. maysorensis, I. globosa and Am.caudatus. Relatively, it is rare to observe that three shrubs U. sp., Ab. Moschatus, and S. acuta were infected by these strains.2. Foliar endophytic fungi have little impact on the growth of native plantsWe tested the effects of four kinds of foliar endophytes on the growth of9plant species, involving the height of aerial part and underground part. On the whole, foliar endophytes of A. adenophora have little impact on the growth of native plants. Among the four kinds of dominant endophytic fungi, only a few of strains caused significant effect on the ground part or underground part. For example, Alternaria M4and Colletotrichum AX199can significantly affect the growth of Am. caudatus root. 3.There are different pathogenic patterns for four kinds of endophytic fungi of A. adenophoraFoliar endophytic fungi have the characteristics of both the generalist and specialist pathogens. Alternaria is as a generalist and there are many strains which can infect a variety of plants. For example, strain XS30is pathogenic on5species of plants; strain XS4is pathogenic on three species of plants; and strain XSH22is pathogenic on four species of plants. Relatively, Colletotrichum performed like a specialist. More than50%of the tested strains were observed to infect only one of plants. Otherwise, there are still a few which can cause more than3kinds of plants disease.Such as strain AX118and JK87. Both of them can reduce the germination rate of four kinds of plant. Phomopsis trends to be a specialist but Xylaria like a generalist.In conclusion, our results showed that four kinds of endophytic fungi have a great potential pathogeneicity on the seeds of vines and grass plants. Relatively, these strains play no influence on shrub plants. In particular, all tested strains, with the exception of JT1, are able to infect I. globosa. It could be expected that endophytic fungi can cause local plants disease after releaseing from leaves of A. adenophora, and indirectly enhance the invasive force of A. adenophora. |
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