Optimization of Surface Sterilization for Legume Seed
1990
Caetano-Anollés, G. | Favelukes, G. | Bauer, W. D.
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. Salaries and research support provided by state and federal funds appropriated to the Ohio Agric. Res. and Development Ctr., Ohio State Univ. Manuscript No. 360-89. This work was supported in part by grants from SECYT, CONICET and CICBA (Argentina), by grant No. DE-FG02-86ER 13522 from the U.S. dep. of Energy, and by grant No. 86-CRCR-1-2118 from the USDA Competitive Res. Grants Office.
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