Growing nonmycorrhizal loblolly pine (Pinus taeda L.) seedlings in a standard greenhouse setting.
Stottlemyer, Aaron*,1, Layton, Richard*,1, Wang, Geoff1, Wells, Christina*,2, Waldrop, Thomas3, Callaham, Mac4, 1 Dept. of Forestry and Natural Resources, Clemson University, Clemson, SC2 Deptartment of Horticulture, Clemson University, Clemson, SC3 USDA Forest Service, Southern Research Station, Clemson, SC4 USDA Forest Service, Southern Research Station, Athens, GA
ABSTRACT- Nonmycorrhizal seedlings are used for field and greenhouse bioassays of soil inoculum potential and for experiments that require inoculation with specific fungal symbionts. When growing nonmycorrhizal seedlings in greenhouses, airborne spores of mycorrhizal fungi are a potential source of contamination. Some researchers have successfully grown large numbers of nonmycorrhizal seedlings using only standard greenhouse space and sterilized growth media. Others have required growth chambers with high-efficiency air filtration systems to remove airborne spores from the atmosphere. The objective of our study was to determine the conditions necessary for growing loblolly pine (Pinus taeda L.) seedlings free of ectomycorrhiza. We used a 2 × 7 factorial design with two environment treatments (a HEPA-filtered growth chamber and standard, un-filtered greenhouse space) and seven non-soil and soil-based media treatments. Electronic particle counts differed markedly between the air of the greenhouse (1,345,067 ± 66,800 particles ≥ 0.5 m per m3 air) and that of the HEPA-filtered growth chamber (30 ± 23 particles ≥ 0.5 m per m3 air). Similar results were obtained with 9-cm Petri dish traps containing potato-dextrose agar media. The traps averaged 27 ± 9 fungal colonies per plate in the greenhouse and 0.2 ± 0.5 colony per plate in the growth chamber. Whether increased air contamination in the greenhouse was associated with increased levels of ectomycorrhizal colonization of pine seedlings is currently being determined.
Key words: ectomycorrhizas, soil bioassays, nonmycorrhizal
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