| Elymus nutants is an important forage with high quality in Tibetan Plateau,China,which plays important roles in the development of livestock husbandry and protection of ecological environment.Seedborne fungi is one of the main limiting factors in the production of E.nutants.This thesis was conducted based on seed samples of E.nutants collected from 11 main distribution areas of this forage in Gansu and Qinghai Provinces,and defined the diverse characters of seedborne fungi area and different areas of E.nutants.Through the vaccination experiment,the paper proves the impacts of main seedborne fungi on seedlings and young plants.The research findings include:1.Based on the morphology and ITS gene identification of the seeds samples of E.nutants from 11 different areas,fungi belong to 17 genus and 23 species were identified:Acremonium sclerotigenum,Alternaria alternata,Alternaria tenuissima,Aspergillus flavus,Aspergillus niger,Bipolaris sorokiniana,Botrytis cinerea,Chaetomium globosum,Chaetomium murorum,Cladosporium herbarum,Drechslera erythrospila,Epicoccum nigrum,Fusarium acuminatum,Fusarium avenaceum,Fusarium oxysporum,Fusarium tricinctum,Nigrospora oryzae,Penicillium italicum,Phoma bellidis,Purpureocillium lilacinum,Pyrenophora teres,Stachybotrys chartarum and Trichothecium roseum.2.The carrying rate and diversity of seedborne fungi of E.nutants varied from sampling areas.Fusarium and Alternaria were the dormant genus of the seedborne fungi of E.nutants with the relative isolation frequency over 10%across all sampling areas,which was isolated in all the sampling areas.Bipolaris,Aspergillus and Chaetomium were the common genus with the relative isolation frequency ranging from 5%to 10%while other genus were rare and their relative frequency was less than 5%.Diversity analysis showed that the sample from Zhuoni(Gansu Province)exhibited the highest Shannon-Weiner Index(2.872)and Chao1 Index(22.625),while the sample from Tianjun(Qinghai Province)exhibited the lowest Shannon-Weiner Index(2.198)and Chao1 Index(10.400).Evenness analysis showed inconsistent evenness index across all sampling areas with all the evenness index above 0.900except Lintan with the evenness index of 0.889,and the sample from Haiyan(Qinghai Province)showed the highest index of 0.965.Redundancy analysis showed that altitude had the greatest effects on the community composition of seedborne fungi of E.nutants among all environmental factors tested,followed by annual average temperature,and the redundancy analysis explained 54.8%of the variance,which indicated that the interactions among all environmental factors influenced the community composition of seedborne fungi of E.nutants.3.There was a significantly(P<0.05)negative correlation between fungi-carrying rate and seed germination rate of E.nutants(R~2=0.5817).Fifteen fungi with the isolation frequency over 1%all decreased the germination rate of seeds and the growth of seedlings.F.oxysporum exhibited the strongest inhibition on seed germination rate and seed germination potential,with a decrease rate of 58.3%in seed germination rate and 70.1%in seed germination potential compared with the non-inoculation control treatment;followed by C.herbarum,F.avenaceum and T.roseum,which decreased the germination rate of seeds by 39.6%,32.8%and 28.6%,respectively.B.sorokiniana,D.erythrospila,F.avenaceum and F.oxysporum decreased the height of seedlings by 44.7%,48.9%,46.4 and 45.8%,respectively.B.sorokiniana,F.avenaceum,F.oxysporum decreased the length of roots by 61.9%,61.0%and58.0%,respectively.F.acuminatum,F.avenaceum,F.oxysporum and B.sorokiniana had the most significant(P<0.05)impact on dry weight of seedlings with a decrease rate of 50.0%,57.1%,51.8%and 53.6%,respectively. |
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