Diversity Of Arbuscular Mycorrhizal Fungi Associated With Common Wild Plants In The Drawdown Zone Of Three Gorges Reservoir

Arbuscular mycorrhizal fungi (AMF, phylum Glomeromycota) are diverse and widely distributed in natural ecosystems. They are obligately symbiotic soil organisms which potentially form mutualistic associations with about 80% of the terrestrial plants. These fungi are functionally important for plants, as they can increase uptake of poorly mobile soil nutrients, especially phosphate and nitrogen, enhance tolerance to stressor such as root pathogens, drought and polluted environments and accelerate soil aggregate stability and plant establishment. The main soil is yellow sticky, purple soil and purple gritstone in the plant rhizospheric soils in the drawdown zone in the Three Gorges Reservoir. Previous studies have primarily focused on the vegetation reestablishment and ecological restoration in the drawdown zone of the Three Georges Reservoir. However, little attention has been paid to the diversity and roles of microfungi, especially arbuscular mycorrhizal fungi in this ecosystem. Thus, this study was undertaken to examine AM fungal community composition in the common wild host plants and to explore the relationship between AM fungi and soil factors in the wild plans in the drawdown zone of Three Gorges reservoir, China. The main results are as follows:1 Of the 10 plants species found in the drawzone of Three Gorges reservoir, all plants were colonized by AM fungi, rarely by dark septate endophytes. The Arum-type and Paris-type of arbuscules were observed. There were Arum-type arbuscules in plant roots of Myrsine africana L. Phytolacca americana L., Rubus corchorifolius L. f., Smilax china L., Distylium chinense (Fr.) Diels and Thalictrum delavayi Franch.. There were Paris-type arbuscules in the roots of Lysimachia phyllocephala Hand.-Mazz. and Veronicast-rum stenostachyum (Hemsl.) Yamazaki. The proportion of Arum-type to Paris-type was 4 to 1. No arbuscules were found in the roots of Itea oblonga Hand.-Mazz. and Rhus chinensis Mill.. The colonization of AM in plant roots varied with host plant species, ranging from 18.46%(Rhus chinensis) to 60.47%(Myrsine stolonifera).2 A total of 50 AM fungal species were detected and identified morphologically in this study. They belong eight genera of the Glomeromycota. The largest number of identified species belonged to the genera Glomus with 32 species, followed by Acaulospora with eight, Ambispora with three. Scutellospora and Diversispora had two species each. Entrophospora, Gigaspora and Paraglomus were represented by only one species, respectively. Besides, seven species belonged to new records species reported in China those were Ambispora callosa, Ambispora grantensis, Ambispora reticulate, Glomus caesaris, Paraglomus pernambucanum and Diversispora epigaea.3 The distribution of AM fungi in the rhizospheric soil varied with host plants. Twenty eight species of AM fungi belong to 5 genus were observed in soil samples from the rhizosphere of Itea oblonga Hand.-Mazz.. Twenty seven species AM fungi belong to 6 genus were observed in soil samples from the rhizosphere of Lysimachia phyllocephala Hand.-Mazz.. Thirty six species AM fungi belong to 7 genus were observed in soil samples from the rhizosphere of Myrsine africana L.. Twenty one species AM fungi belong to 4 genus were observed in soil samples from the rhizosphere of Phytolacca americana L.. Twenty five species AM fungi belong to 5 genus were observed in the soil samples from the rizosphere of Rubus corchorifolius L. f.. Twenty seven species AM fungi belong to 3 genus were observed in the soil samples from the rizosphere of Veronicastrum stenostachyum (Hemsl.) Yamazaki. Twenty five AM fungi species belong to 4 genus were observed in soil samples from the rizosphere of Smilax china L.. Sixteen AM fungi species belong to 3 genus were observed in soil samples from the rizosphere of Distylium chinense (Fr.) Diels. Eighteen AM fungi species belong to 6 genus were observed in soil samples from the rizosphere of Rhus chinensis Mill.. Nineteen AM fungi species belong to 4 genus were observed in soil samples from the rizosphere of Thalictrum delavayi Franch.4 The highest relative abundance AM species were Glomus geosporum in the wild plants in the drawdown zone in Three Gorges Reservoir, which were widely distributed in each sample host plant rhizosphere. A. excavate, A. undulate, G. monosporum, G. versiforme and G. brohultii were dominant species; G. etunicatum, A. koskei, G. caesaris, G. coronatum, G. flavisporum, G. heteroaporum and G. macrocarpum were common species.5 There were at least 8 genus AM fungi were observed, including Ambispora, Diversispora, Gigaspora, Paraglomus and Scutellospora, which reported infrequently in Three Gorges Reservoir. In all sample plant rhizospheric soils, Glomus had the highest frequency and abundance.6 The spore density and species richness in Myrsine africana L. were highest (1780 per 100 g soil, 36). The Shannon-Wiener diversity (H’) and Evenness (J) index were highest in Phytolacca americana L.. In contrast, Distylium chinense (Fr.) Diels and Rhus chinensis Mill. had the lowest spore densities and species richness and Rubus corchorifolius L. f. had the lowest Shannon-Wiener diversity (H’) and Evenness (J) index(1.69,0.40).7 Our research showed that the relationship between environmental variables and diversity index of AM fungi. Abrscular colonization (AC) had significant positive correlation with total nitrogen (TN) and soil moisture (SM), while had significant negative correlation with available K (AK) and C and N ratio. Besides, viscular colonization (VC) had significant negative correlation with available K (AK) and TN. Both spore density and specie richness were significantly positive correlated with TC and SM, while spore density was also significantly positive correlated with TN. Moreover, Shannon-Weinner diversity index (H’) and evenness index (J) had significant positive correlation with C and N ratio, while evenness had significant negative correlation with TN. Based on pearson correlation analysis, TN, C and N ratio, TC, AK and SM were important factors that influenced the AM colonization and AMF diversity in the common wild plants rhizospheric soils in the drawdown zone in the Three Gorges Reservoir.8 We examined root and rhizospheric soil samples of seven common submergence tolerant plants by molecular biology techniques. Glomeraceae were dominant family in most host plant roots and rhicprsss soil. In sample plant soils, Glomeraceae spp was dominant species in the most host species except for Houttuynia cordata Thunb.. Moreover, Glomus versiforme was dominant species in Cynodon dactylon rhizosphere soils, Septoglomus viscosum was dominant species in Hemarthria altissima rhizosphere soils and Glomus sp was dominant in Ophiopogon japonicas rhizosphere soils. AMF community composition had a significant difference between different plants roots and the dominant species in the plant roots varied with the host plants.