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In vitro propagation and life cycle of the arbuscular mycorrhizal fungus Glomus etunicatum

Published online by Cambridge University Press:  01 December 1999

TERESA E. PAWLOWSKA
Affiliation:
Department of Plant Biology, University of Minnesota, 220 Biological Sciences Center, 1445 Gortner Avenue, St Paul, MN 55108-1095, U.S.A. Present address: Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720, U.S.A.
DAVID D. DOUDS
Affiliation:
Eastern Regional Research Center, USDA/ARS, Wyndmoor, PA 19038, U.S.A.
IRIS CHARVAT
Affiliation:
Department of Plant Biology, University of Minnesota, 220 Biological Sciences Center, 1445 Gortner Avenue, St Paul, MN 55108-1095, U.S.A.
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Abstract

Progress in understanding the biology of arbuscular mycorrhizal fungi is hampered by the limited number of species that can be successfully propagated and studied in vitro. We report the establishment of monoxenic cultures of Glomus etunicatum in association with excised Ri T-DNA transformed carrot roots. The fungus can be propagated in vitro using monoxenically formed resting spores and/or colonized root fragments. Modified White's medium buffered with 10 mM MES (pH 6) or MOPSO (pH 6·5) was most optimal for the host root growth as well as for G. etunicatum spore germination and mycorrhiza formation. The number of resting spores formed in vitro correlated positively with the length of roots occupied by arbuscular mycorrhizal structures, including arbuscules and vesicles. Spores first appeared in dual cultures within two weeks of root inoculation. Sporulation was asynchronous and continued until root senescence. Under applied culture conditions, spores achieved mature appearance within 5–7 d after their initiation. Approximately 6% of monoxenic spores were aborted at different stages of their development. Although G. etunicatum spores formed in vitro exhibited general morphological and anatomical similarity to soil-borne inoculum, they were significantly smaller and had thicker spore walls than their soil-borne counterparts. Caution should, therefore, be exercised in utilizing the in vitro system as a model of growth and development of glomalean fungi in soil.

Type
Research Article
Copyright
© The British Mycological Society 1999

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