Getting start on a molecular systematics project - a pdf file of advice from Dr. E.A. Kellogg. Worth reading

Rules
Material
Collecting equipment
Preservatives
Voucher specimens
Collection numbers

Another site with
information

1. Make sure that the material you collect is physically attached to a plant, or portion of a plant, that can be identified with confidence, preferably a plant of the species you are interested in.
2. Place the material for DNA studies in whatever preservatives you are using as soon as possible after it has been collected. This will minimize the possibility of degradation.
3. Make a voucher specimen of the portion of the plant that is not preserved for DNA studies.  This specimen should contain an inflorescence and vegetative material, i.e., be a GOOD herbarium specimen.
4. Select undamaged material.

Plant material: The best material for DNA studies are actively growing portions of the plant.  The need for a clearly identifiable plant usually means that the material should come from a plant with a well-developed inflorescence.  There are several active growing locations on grasses:

• Young innovations - preferably the base of the blade of the youngest leaf of an innovation.  Because this leaf will only recently have emerged from the lower leaf sheath, there is also a reasonably high probability that it has not been damaged.
• If there are no immature innovation leaves attached to the plant, look at the base of the blade of the top cauline leaf of each culm.  These are more likely to be damaged than an incompletely exposed innovation leaf, but sometimes one has no choice.
• Another possibility is a young inflorescence, one that is still included in the upper leaf sheath.
• Another growing point is the base of the internode of a plant that has not headed out.

Whatever material is used, cut it into segments about 1-2 cm long and place them in a container with preservative in. Each specimen needs to be in a separate container.  This helps ensure that, even if one container breaks or becomes contaminated, only one specimen is affected. 

Place a tag with your initials and the collection number in with the specimen and on the outside of the container.  Use your initials and collection number rather than the name of the species because a) you may collect more than one species, b) you might have misidentified the plant.

The reason that only undamaged material should be used is that damage makes it too easy for some other organism, such as a bacterium or fungus, to become established in the leaf tissue.  The effect of such invasions may not be visible for some time, but the presence of foreign DNA in the material can create major problems.  In almost all instances, no material is better than damaged material. 

Collecting equipment.  The equipment needed for collecting DNA material from grasses is very simple. 

• Standard collecting equipment
  Plant press with cardboards
  Newspaper
  Field notebook
  Stationary labels
  Pencil (not a pen - they do not work well in wet weather or alcohol)
  Geographic Positioning System (optional, but really nice to have)
• Cutting equipment
  Small, sharp scissors are the best choice.  A knife or razor blade can be used instead, but they are not nearly as convenient.
• Storage containers
  What is used depends on the preservative.

Preservatives: There are several substances that can be used to preserve plant material for DNA substances.   Preservatives that suitable for field work include:

• A saturated NaCl-CTAB solution See revised, improved solution
• Reagent grade absolute alcohol (100% alcohol, preferably AR grade). 
• Dehydrated amorphous silica gel.  It helps to add a few grains of indicator gel that will change color from blue to pink if it becomes rehydrated. 
• Liquid nitrogen (but the material must remain deeply frozen until being used for DNA extraction).

Saturated NaCl-CTAB Solution. [CTAB = Hexadecyltrimethylammonium bromide, information you will probably need when placing an order]. Steven Rogstad (Taxon 41:701-708) compared results of DNA sequencing from fresh material, deeply frozen fresh material, material stored in a saturate NaCl-CTAB solution, and material dried at 40C (as in a press over a drier).  Fresh or deep frozen fresh material yielded the best results but, if these procedures are not feasible, saturated NaCl-CTAB is the best alternative.  The solution can be made up in advance, stored at ambient temperatures, taken in the field, and sent through the mail.  On arrival, freeze the containers.  Exact concentrations are not critical, so extra solution can be made up in the field if necessary.  CTAB is hexadecyltrimethylammonium bromide.

To prepare the solution, boil as much water as needed, allow to cool almost to ambient temperature then add NaCl and mix thoroughly.  To ensure saturation, add so much that about a 1 cm layer will not dissolve, no matter how hard you try.  Then slowly add the CTAB (heading the warnings labels about avoiding eye contact, inhaling, and labeling containers etc.), stirring as you do so, until the mixture is like honey or motor oil - approximately 30-40 g of CTAB to 11 of salt solution.  CTAB takes several hours to become fully hydrated, so prepare in advance.  Scintillation vials or sealed plastic bags can be used as containers. 

John A. Thomson, in Telopea 9:755-760 (2002) recommends adding 200 mM sodium ascorbate to the saturaged NaCl-CTAB solution because it extends the range of plant species from which good quality DNA can be obtained without cryogenic transport and storage.

Containers.  If alcohol is used as a preservative, look for glass, screw top containers that close well.  These can be stored in a cardboard crate frame to hold the bottles upright.  If using NaCl-CTAB, scintillation vials or well-sealed plastic bags work effectively. 

If sending material in liquids by air (and parcels sent 'surface mail' through the US Postal Service are sometimes shipped by air), the packaging should include material for absorbing moisture and fumes that may leak out because of the changes in pressure - and just in case a bottle breaks.  Cotton batting works if you can find it. I could not find any recently, so used the absorbent material from incontinence underwear. It was the source of some amusement, but it worked. And none of the glass vials broke. We also used bubble wrap and Styrofoam packing pellets as shock  absorbing material.  

Specimens collected into silica gel are usually stored in sandwich bags that can be sealed tightly.  These can be kept in a box, but care must be taken to ensure that no holes are made in the bags, either before or after the specimens are placed in them.   Double-bagging is an inexpensive form of insurance if acquiring the material required field work. 

When liquid nitrogen is used as the preservative, the specimens are placed in small plastic containers that are then dropped in the nitrogen which needs to be kept in a Dewar flask iso that it remains liquid. 

Voucher specimens.  A voucher specimen is a herbarium specimen that can be used as evidence that the identifications used in a particular study are accurate.  It should be deposited in a herbarium that is listed in Index Herbariorum (Holmgren et al. 1983) and that will, upon request, loan specimens to other herbaria. Voucher specimens may document chromosome counts, photographs, floristic studies, or the material used in a DNA or other molecular study.

In a DNA study, the voucher specimen must be made from the same plant(s) as the DNA material was taken from, because the reason for making a voucher specimen is to make it possible to accurately identify the material collected.  If there is any question as to its identification, a taxonomist who is particularly familiar with the species should be asked to determine its identity.

The existence of voucher specimens also gives a study a longer term value because, if someone later makes taxonomic changes in the group, the identity of the voucher specimens, and the implications of the study itself, can be re-evaluated.  If voucher specimens have not been made, it is impossible to re-evaluate DNA data or the implications of the study.  In other words, the study will lose some, possibly all, of its value.

Collection number.  When a herbarium specimen is collected, the collector (or the assistant) records information about the collection site, date, and collectors, in a field notebook.  Each species collected from a given site on a given date is given a separate number.  (In some studies, it is advisable to give different plants of the same species different numbers). 

Some collectors use a consecutive numbering system throughout their life; others restart their numbers at the beginning of each year and precede the number by the last two digits of the year, e.g., 98.105 would be the 105th collection in 1998. (No collectors have been active for more than a century so there is no confusion as to which century is involved).