Colonization Characteristics and Diversity of Arbuscular Mycorrhizal Fungi in the Rhizosphere of Iris lactea in Songnen Saline-alkaline Grassland

To understand arbuscular mycorrhizal(AM)fungi resources and develop AM fungal species in ornamental plants with saline-alkaline tolerances,Iris lactea,which grows in the Songnen saline-alkaline grassland with a high ornamental value,was selected as the experimental material,and the colonization characteristics of its roots and the AM fungal diversity in its rhizosphere were explored.The results of the observations and calculations of mycorrhizae from ten different samples showed that AM fungi colonized the roots of I.lactea and formed Arum-type mycorrhizal structures.There was a significant correlation between soil spore density and pH value,while the colonization rate showed a fluctuating trend with increasing pH values.The observed colonization intensities were of Levels II(1%–10%)or III(11%–50%),and the vesicle abundances were of grades A2 or A3 among different sites.AM fungi produced a large number of mycelia and vesicles in the roots of I.lactea after colonization.Thirty-seven species belonging to 15 genera of AM fungi were isolated from the rhizosphere of I.lactea and identified by morphological identification.Funneliformis and Glomus were the dominant genera,accounting for 21.79%and 20.85%of the total number,respectively.F.mosseae and Rhizophagus intraradices were isolated in all samples with importance values of 58.62 and 51.19,respectively.These results are expected to provide a theoretical basis for the analysis of the salt tolerance mechanism of I.lactea and for the discovery,exploration and further screening of AM fungal resources with salinity tolerances in saline-alkaline soils.

Fungal spore record of pastoralism on the NE Qinghai-Tibetan Plateau since the middle Holocene

Pastoralism is considered a crucial factor in the eventual year-round occupation of high-altitude regions(>3000 m asl)of the Qinghai-Tibetan Plateau,and the northeastern Qinghai-Tibetan Plateau(NE-QTP)was an important corridor for early human occupation.We analyzed fossil fungal spore records for the last 8500 years from a high resolution aeolian section at Langgeri(LGR)on the NE-QTP.Thirty-two fungal spore types were identified in the LGR section,including seven coprophilous types.We combined analysis of coprophilous fungal spores,Cyperaceae,Artemisia,and Hippophae pollen,and the charcoal>50µm fraction to explore the timing and controls of pastoralism on the NE-QTP since the middle Holocene.Pastoralism commenced at LGR shortly before ca.5.5 ka and gradually increased between ca.5.5–3.5 ka,but markedly intensified after ca.2.2 ka,with three periods of growth at ca.2.1–1.9,1.4–1.2,and 0.6–0 ka,and a decline at ca.1.1–0.6 ka.The timing of changes in pastoral activity on the NE-QTP based on the coprophilous fungal spore record is supported by regional archeology and historical documents.Technological and political developments,rather than climate change,played key roles in the long-term fluctuations of regional pastoralism on the NE-QTP in the late Holocene.

Effects of land use on the fungal spore richness in small crater-lake basins of western Uganda

Mycological tools to estimate the effects of diverse land-use practices on fungal diversity are scarce,because of poor knowledge of the taxonomic diversity of tropical fungi and their response to anthropogenic habitat change.Here,we investigate assemblages of fungal spores,recently deposited in the bottom sediments of 24 small crater lakes in western Uganda,to assess the relationship between the local richness of fungi and environmental variation in the crater basin along regional gradients of natural vegetation and land use.We recovered~9500 fungal spore specimens,which could be attributed to 216 morphotypes.Using an information-theoretic approach based on the corrected Akaike Information Criterion(AICc),we determined the environmental factors which best explained variation in the diversity of fungal spores among three datasets:(i)the full set of 24 crater basins,(ii)the subset of 22 basins with freshwater lakes,and(iii)the subset of 17 basins partly or completely in agricultural use(cropland,fallow land,pasture and plantation).In these 17 human-impacted crater basins our results revealed a negative relationship between fungal spore richness and the areal fraction of basins in agricultural use.However,this detrimental effect of land use on fungal spore richness was not apparent across the full set of both disturbed and(presently)undisturbed basins.This was due to large variation in fungal spore richness among the undisturbed basins covered either with forest or savannah vegetation,probably resulting from site-specific controls on fungal habitat diversity,such as climatic moisture balance and the composition of natural and/or secondary vegetation.The land-use effects on fungal spore diversity,as documented in this study,suggest that communities of tropical fungi progressively exposed to land-use practices are threatened by species loss.Hence,our study demonstrates the need to develop conservation strategies mitigating the impacts of agriculture on the biodiversity of tropical fungi.

A new spectral index for the quantitative identification of yellow rust using fungal spore information

Yellow rust(Puccinia striiformis f.sp.Tritici)is a frequently occurring fungal disease of winter wheat(Triticum aestivum L.).During yellow rust infestation,fungal spores appear on the surface of the leaves as yellow and narrow stripes parallel to the leaf veins.We analyzed the effect of the fungal spores on the spectra of the diseased leaves to find a band sensitive to yellow rust and established a new vegetation index called the yellow rust spore index(YRSI).The estimation accuracy and stability were evaluated using two years of leaf spectral data,and the results were compared with eight indices commonly used for yellow rust detection.The results showed that the use of the YRSI ranked first for estimating the disease ratio for the 2017 spectral data(R^(2)=0.710,RMSE=0.097)and outperformed the published indices(R^(2)=0.587,RMSE=0.120)for the validation using the 2002 spectral data.The random forest(RF),k-nearest neighbor(KNN),and support vector machine(SVM)algorithms were used to test the discrimination ability of the YRSI and the eight commonly used indices using a mixed dataset of yellow-rust-infested,healthy,and aphid–infested wheat spectral data.The YRSI provided the best performance.

Arbuscular mycorrhizal fungi in the rhizosphere soil of poisonous plants depressed the growth of pasture grasses in the Tibetan Plateau Alpine meadow

In order to explore the influence of arbuscular mycorrhizal(AM)fungi in the rhizosphere of poisonous plants on the neighboring pasture grasses in the Tibetan Plateau Alpine meadow ecosystem,rhizosphere soils were collected from eight different poisonous plants in degraded grasslands and one from pasture grass in non-degraded grasslands(CK).The collected soils were used as inocula to assess the influence of indigenous AM fungi on the growth of two typical pasture grass species,Elymus nutans and Poa pratensis,in a bioassay experiment.Five growth parameters and two AM parameters were determined.The mycorrhizal responsiveness and the importance value were calculated.Significant differences between the eight poisonous plants and CK were observed.Compared to CK,rhizosphere soil from the eight poisonous plants had lower AM fungal spore densities.The growth of E.nutans and P.pratensis seedlings was depressed with the inoculation from poisonous plants rhizosphere soil.This study demonstrated that the presence of poisonous plants with grassland degradation altered inherent AM fungal community abundance,and could exert inhibition effects on the growth of pasture grasses.It may attribute to discover the important role of rhizosphere soil of different poisonous plants to AM fungal community on the Alpine meadow.