Plant DNA from alcohol-preserved samples

A process to isolate DNA from alcohol-preserved plant tissue is described. Key features are simple, inexpensive sample preservation, fast tissue disruption, and no organic solvents. Tissue preservation and homogenization are two rate-limiting steps and are major nuisances in the isolation of plant DNA. Fresh samples require hand grinding, which is problematic due to large tissue volumes and sample numbers, or when plants are grown in a remote location. Freezing requires equipment, complicates shipping, and the grinding is tedious. Freeze drying (Murray and Thompson, 1980)requires expensive equipment on location, although more recently, Tai and Tanksley (1990)demonstrated that a food dehydrator can be substituted. Regardless of how tissue is dried, grinding of dry samples remains tedious and messy. The reduction in DNA quantities needed for various PCR-based techniques has made all of the above somewhat easier, but situations remain where one needs DNA in the range of tens of [mu]g to mg. We avoid freezing or drying by pickling the plant tissue in reagent alcohol. Then we grind in a buffer containing hexylene-glycol for the isolation of nuclei, which makes nuclei tough enough to allow tissue disruption with a PolytronTM homogenizer. The preparation of a crude nuclear pellet achieves sufficient purification that purification extraction of the organic phase is generally unnecessary. The resulting DNA is clean enough for Southern blots and PCR-based techniques, though not necessarily of high enough quality for genomic cloning.