Hirokazu Tsukaya
Because of a lack of molecular materials on specimens in herbaria, we are required to collect specimens for molecular analysis by ourselves. Collecting specimens from mang localities is a time consuming procedure. If herbarium specimens are made with corresponding samples from which DNA can be extracted, they would have been quite useful, In the above cases, we conld sample enough numbers of plants during short trips in Japan and we restricted our sampling to particular species. Nevertheless, researchers who make specific trips to collect DNA samples for their own research, should also collect herbarium specimens and molecular material of other species, even if they will not use it themselves. This is particularly important when collecting in areas that are difficult to access. How, then, should we collect DNA samples in the field?
We usually collect and dry leaves in silica gel and extract DNA in the lab. Even on extended field trips, the usual method for collecting plant samples for molecular analysis is to place leaves in silica gel. This type of sampling, however, is not suitable for long trips and large scale general collecting in a remote areas because it requires abundant silicagel. Due to this inconvenience, members of a botanical expedition do not usually collect DNA samples unless the members themselves intend to analyze DNA. Even if someone collect samples of DNA, they will not make a general collection and chose a particular taxa for the sampling. Thus, even after a long trip for general collection of herbarium specimen, only a limited kinds of DNA samples are collected. This is wasted effort if we consider the following: (1) the importance of DNA data for understanding taxonomy is undoubtedly increasing; (2) sets of DNA and corresponding herbarium specimens are quite useful for studies of plants, as shown above; (3) most plants in remote areas are not easily accessible and DNA samples from such plants are quite valuable. General collections should be carried out not only for dried specimens but also for DNA samples, if possible. But how can we make it possible?
Fortunately, simple kits for isolating DNA have recently become available. I evaluated the utility of these kits during field studies in remote areas and found the FTA Cards® (Whatman Company) to be useful for collecting DNA without any special equipment (Tsukaya, 2003). FTA Cards® are paper cards that immobilize nucleic acids and have been used for collecting a number of DNA samples from human individuals (Forrest et al., 2004) and microorganism (Subrungruang et al., 2004; Lampel et al., 2004). Collection of DNA from leaf samples is easy. We simply rub or squash leaves on the sheets and allow them to dry at room temperature. Dried cards can be stored indefinitely at room temperature without special care. The PCR reaction can be performed after washing the cards three times for five minutes in a special buffer (supplied with the FTA Cards® by the manufacturer) and three times for five minutes with Tris-EDTA (pH 8.0) buffer. The advantages and disadvantages of FTA Cards® for collecting plant DNA in the field are: Advantages :
Disadvantage :
Considering the above advantages and disadvantages, we examined the usefulness of the FTA Cards® in collecting plant DNA in remote areas.