Project Number: WVA00379
CRIS Number: 0168978
Multi-State Project: S-297
Soil Microbial Taxonomic and Functional Diversity as Affected by Land Use and Management
Investigators: Morton, J. B.
Performing Department: Plant & Soil Sciences -- 1825
Start Date: 10/01/2000
Termination Date: 09/30/2005
Reporting period: 01/01/2001 to 12/31/2001
Progress Report:
At the present time, we continue to focus on assessing the complexity of the taxonomic diversity of arbuscular mycorrhizal fungi in a range of plant communities and habitats. In one study, we examined fungal communities in a wet tropical rainforest in Costa Rica varying in soil fertility, rainfall, and seasonality. Species richness did not vary from that found typically in temperate regions (13 species), but composition was unusual in that it was dominated exclusively by Acaulospora species. These results, combined with others, suggests that this genus might be favored in forested regions with fairly even distribution of rainfall. Amongst the seven tree species examined, which differed in maximum lifetime, fungal community composition did not differ significantly. All differences were expressed by variation in abundance of sporulating fungal species. In another study, we found that three management practices (one conventional and two low-input) associated with corn and soybean over 15 years did not appreciably alter fungal community structure (15 species). Again, differences attributed to agricultural practice and seasonality were expressed in abundance of sporulation by the fungal community. Work has begun to integrate data collected in these and other studies among collaborators and in the published literature to define species "saturation levels" and the correlate community diversity of fungi with that of their plant hosts. At the molecular level, primers have been designed to amplify conservative exons and more variable intron regions of the beta-tubulin gene from selected AM fungi. Amplified products of these primers currently are being cloned and sequenced. In the applied arena, infectivity assays were used to evaluate the effect of organic amendments commonly used in commercial inoculants on overall inoculum potential of a product. Humic acids did not reduce infectivity between 0.25 and 1% (v/v), but greatlly inhibited fungal colonization at 1.5-2%. Whey had no effect on infectivity at any of the tested levels (0.5-20% v/v). Seaweed extract simulated infectivity 1.5-2X relative to unamended controls at all concentrations. In contrast, hydrophilic beads severely reduced nfectivity at all levels. Shoot dry mass in all assays was too variable to draw any valid conclusions about growth benefit.
Publications:
Morton, J. B. and D. Redecker. 2001. Two new families of Glomales, Archaeosporaceae and Paraglomaceae, with two new genera Archaeospora and Paraglomus, based on concordant molecular and morphological characters. Mycologia 93:181-195.
Bever, J. D., P. A. Schultz, A. Pringle, and J. B. Morton. 2001. Arbuscular mycorrhizal fungi: More diverse than meets the eye and the ecological tale of why. BioScience 51:923-931.
Franke-Snyder, M., D. D. Douds, L. Galvez, J. G. Phillips, P. Wagoner, L. Drinkwater, and J. B. Morton. 2001. Diversity of communities of arbuscular mycorrhizal (AM) fungi present in conventional versus low-input agricultural sites in eastern Pennsylvania, USA. Applied Soil Ecology 16:35-48.
Impact:
Studies of diversity will provide the data by which we can begun to assess "assembly rules" for communities of symbiotic fungi and their plant hosts. Once we define these rules, then ecological variables can be manipulated to increase or decrease community diversity. The molecular research will provide new genes to complement existing ones (mostly small subunit rDNA) in understanding phylogenetic (and hence taxonomic) relationships among these fungi. The impact of various organic amendments used in commercial inoculant formulations is essential to designing a product which maximizes growth benefit to plants without compromising infectivity of the fungal inoculum.