| Fungal endophytes are those fungal microorganisms that colonize healthy plant tissues. They live there in part or whole life without causing asymptomatic infections in plant tissues, or at least, a long time later. They are found in almost all plants which have been studied, liverworts, mosses, lycophytes, ferns, hornworts, equisetopsids and seed plants included. They are so ubiquitous and considered hyperdiverse in plant kingdom. And 1.5 million of endophytic fungi have been estimated as so far. However, only 6-7 percent of these endophytic fungi has been described. A great mount of the rest are waiting their chances to be recognized and to exist in microbial world. The greater the number is, the greater the responsibilities are. It is reported that endophytic fungi are used in so many areas related to agriculture and pharmaceuticals industry. The host-fungal symbiosis could be beneficial to hosts, such as, resistance to pathogens, insects and herbivores[8-10]. They can also reduce the costs in terms of water relation, photosynthesis, stress and drought tolerance[11-13]. To enhance the growth of vegetables is another use of endophytic fungi[14]. What’s more, it is well recognized that plant-associated microbes have great influence on host populations, biosynthesis, plant communities, biotransformation and biodegradation[15-18]. Last but not the least, metabolites of endophytic fungi can also be beneficial to inhibit the growth of blue-green algae. Based on mentioned above, two kinds of flooding-resistant plants, Myricaria laxiflora and Distylium chinense, were chosen to research the biodiversity of endophytic fungi and the influence of metabolites from endophytic fungi on Microcystis aeruginosa.In order to finish missions mentioned above, endophytic fungi need to be obtained. A total of 45 endophytic fungi were isolated from the roots of Myricaria laxiflora while 46 were isolated from the stems of Myricaria laxiflora. Then the endophytic fungi from roots were identif ied into 17 morphotaxa while 11 from stems based on morphological and molecular characterizations. The dominant genera in roots of Myricaria laxifloraare. Sordariomycetes, Ascomycota and Dothideomycetes while Alternaria tenuissima and Alternaria alternate in stems. Then 45 isolates, 30 from roots and 15 from stems were picked to do the dural culture method against Verticillium dahliae, Colletotrichum destructivum O’Gara, Alternaria brassiscae and Fusarium roseum. It is shown that none of the endophytic fungi shows resistant activity on Verticillium dahliae, while 11 isolates show resistant activity on Colletotrichum destructivum O’Gara, 5 isolates show resistant activity on Alternaria brassiscae and 9 isolates show resistant activity on Fusarium roseum. Among the 5 isolates show resistant activity on Colletotrichum destructivum O’Gara, 1 isolate shows great resistant activity on it. In the 15 isolates from stems, 5 isolates show resistant activity on Verticillium dahliae, 7 isolates show resistant activity on Colletotrichum destructivum O’Gara, 7 isolates show resistant activity on Alternaria brassiscae and 3 isolates show resistant activity on Fusarium roseum. Then Oxford cup experiment was carried out on the 45 isolates chosen to test whether metabolites of them also have resistant activity on the pathogens used. Pitifully, it shows nothing. Up next, inhibition of cyanobacteria experiment with metabolites of the 45 endophytic fungi to Microcystis aeruginosa were taken. Results showed that 20 isolates from roots have positive influence on Microcystis aeruginosa while 10 iaolates show negative inf luence. In the 20 isolates, 3 isolates show greatest influence on it, the inhibition ratio is up to 50 to 60 percent, 3 isolates show greater influence on it, the inhibition ratio is up to 40 to 50 percent and 5 isolates show great influence on it, the inhibition ratio is up to 20 to 40 percent. As for the rest, they only have weak influence on Microcystis aeruginosa. In stems part, results showed that 7 isolates from stems have positive inf luence on Microcystis aeruginosa while 8 iaolates show negative influence. In the 15 isolates, only 1 isolate shows greater influence on it, the inhibition ratio is up to 40 to 50 percent and 1 isolates show great influence on it, the inhibition ratio is up to 20 to 40 percent. As for the rest, they only have weak influence on Microcystis aeruginosa.As for Distylium chinense, a total of 109 endophytic fungi were isolated from the roots of Myricaria laxif lorawhile 52 were isolated from the stems of Distylium chinense. Then the endophytic fungi from roots were identified into 13 morphotaxa while 11 from stems based on morphological and molecular characterizations. The dominant genera in roots of Distylium chinense are Phomopsis sp., Xylaria venosula and Neof usicoccum parvum while Xylaria venosula and Neofusicoccum parvum in stems. Then 34 isolates, 20 from roots and 14 from stems were picked to do the dural culture method against Verticillium dahliae, Colletotrichum destructivum O’Gara, Alternaria brassiscae and Fusarium roseum. It is shown that 2 of the endophytic fungi show resistant activity on Verticillium dahliae, while 4 isolates show resistant activity on Colletotrichum destructivum O’Gara, 7 isolates show resistant activity on Alternaria brassiscae and 11 isolates show resistant activity on Fusarium roseum. In the 14 isolates from stems, 2 isolates show resistant activity on Verticillium dahliae, 5 isolates show resistant activity on Colletotrichum destructivum O’Gara, 3 isolates show resistant activity on Alternaria brassiscae and 10 isolates show resistant activity on Fusarium roseum. Then Oxford cup experiment was carried out on the 34 isolates chosen to test whether metabolites of them also have resistant activity on the pathogens used. Pitifully, it also shows the same result with endophytic fungi from Myricaria laxiflora. Up next, inhibition of cyanobacteria experiment with metabolites of the 34 endophytic fungi to Microcystis aeruginosawere taken. Results showed that 14 isolates from roots have positive influence on Microcystis aeruginosa while 6 iaolates show negative inf luence. In the 14 isolates, only 3 isolates show greatest influence on it, the inhibition ratio is up to 50 to 60 percent. As for the rest, they only have weak influence on Microcystis aeruginosa. In stems part, results showed that 10 isolates from stems have positive influence on Microcystis aeruginosawhile 4 iaolates show negative inf luence. In the 10 isolates, only 1 isolate shows greatest influence on it, the inhibition ratio is up to 50 to 60 percent. As for the rest, they also only have weak influence on Microcystis aeruginosa.So, based on the results above, we have sufficient evidence to imply that biodiversity of endophytic fungi of plants in Three Gorges Reservoir Region are so huge and they have great potential to inhibit pathogens and blue-green algae. |
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