Analysis of Alternative Storage Conditions for DNA Recovery from Field Samples

As ecologists increasingly employ molecular methods, they find that tried and true preservation solutions (e.g. ethanol or formalin) may not be optimal when samples are targeted for genetic analyses. Before traveling to remote sample sites, researchers need to consider which preservation methods are likely to yield the largest quantity and highest quality of DNA based on their travel times and field conditions. They also need to consider whether they will have access to preservatives at remote sites and whether those preservatives can be safely transported. To determine which preservation methods would most reliably preserve tissue for genetic analysis under a range of field conditions, we examined total DNA recovery from female fruit flies (Drosophila melanogaster) individually held in various solutions (70% ethanol; 2% SDS, 100 mM EDTA; 1% SDS, 50 mM EDTA; 0.66% SDS, 33 mM EDTA; Zymo© lysis buffer; Zymo Xpedition© lysis buffer) at three different temperatures (22oC, 4oC and -20oC) for varying lengths of time (1 day, 4 weeks, and 8 weeks). We predicted that insects held in Zymo Xpedition© buffer would yield the overall highest DNA recovery since this buffer was designed for field collected animal tissue. We also predicted that variation in DNA recovery from insects held in different solutions would increase with preservation time and holding temperature. Although we observed significant differences in total DNA recovery from some of our samples, no trends were identified. Preliminary band quality analyses of PCR products utilizing stored DNA as template for amplification of the mCOI gene generally indicated decline in product quality as storage time increased. Future work will focus on better quantifying stored DNA quality and examining the relationship between total DNA recovered and overall DNA quality