Optimization of Surface Sterilization for Legume Seed
- G. Caetano-Anollés,
- G. Favelukes and
- W. D. Bauer
- P lant Molecular Genetics (OHLD), Institute of Agriculture, University of Tennessee, Knoxville, TN 37901-1071
C átedra de Química Biológica I, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900- La Plata, Argentina
D ep. of Agronomy, Ohio State Univ., Columbus, OH 43210
Roots of alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), and soybean [Glycine max (L.) Merr.j seedlings are frequently contaminated with bacteria even after surface sterilization of the seeds and germination under aseptic conditions. Several seedsterilization procedures were compared for their ability to minimize or eliminate such contamination without damaging the plant. Mercuric chloride proved the best seed disinfectant for alfalfa and white clover. Calcium hypochlorite was the best for soybean. For alfalfa seeds, treatment with 95% ethanol (v/v) for 60 min followed by 0.2% HgCl2 (v/v) for IS min prior to rinsing and imbibition resulted in a low frequency (<5%) of seed and root contamination. This treatment resulted in no measurable damage to alfalfa seedlings with respect to root growth, nodulation efficiency, or rate of nodule emergence following inoculation with Rhizobium meliloti. Longer exposures to HgCl2 further reduced bacterial contamination, but also caused modest reductions in seed germination. None of the surface-sterilization techniques tested completely eliminated bacterial contaminants. It appears that these sterilization-resistant contaminants are borne within the seed and proliferate on plant surfaces after germination, with possible effects on plant health.
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