«Comparison of Preservation Techniques for Silkworm (Bombyx mori L.) DNA Based on Polymerase Chain Reaction (PCR) Products Jiraporn Tayutivutikul1*, ...»
However, DNA quality from these specimens varies among insect groups. For example, DNA of beetles stored in ethanol will be degraded in six weeks (Reiss et al., 1995) whereas hymenopterans kept in ethanol for twenty four months still provides DNA in good condition (Dillon et al., 1996). Our silkworm adults preserved in 70% ethanol for six months provided results equal to live specimens. Although the amount of genomic DNA was less and its 900 bp DNA band fragment in the RAPDs genetic map was lighter than that from other preservation techniques in this study, this did not affect the analysis. It confirms that silkworm adults can be preserved by hot air drying and in 70% ethanol for at least six months without DNA degradation. Of these two preservation techniques, 70% ethanol is probably more practical because it is commonly available everywhere. Therefore, 70% ethanol will be a basic preservative of silkworm specimens for our future molecular studies. Furthermore, grinding techniques did not affect the recovery of DNA for PCR, therefore, silkworm samples will be ground directly in lysis buffer instead of using liquid nitrogen.
In conclusion, although we found a suitable way to do short term preservation of silkworm adults using 70% ethanol and a simplified grinding method, pilot studies for the whole procedure are still recommended for other insect studies before preserving large number of specimens, especially if the samples are difficult to collect or have limited availability. No method can be guaranteed to work universally well and exceptions may exist. For example, some beetle species preserved in absolute alcohol immediately after collection have yielded DNA that is seriously compromised and useless for amplification by PCR. On the contrary, the extracted DNA from those beetles would have been good if they had been kept alive and starved for a few days before preservation (Zhang and Hewett, 1998).
ACKNOWLEDGEMENTSWe would like to thank Faculty of Agriculture, Chiang Mai University who kindly provided an equipment for this study from the subproject of graduate study and research in agricultural biotechnology (Ag-Biotech).
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