Collection of Plant Material for DNA Barcoding

Short Manual on How to Collect Plant Material for DNA purposes

The following is compulsory for each collected plant sample:

a) Herbarium voucher

At least two specimens of the same plant must be prepared. One will be kept at the University of Johannesburg Herbarium, and the second deposited in a central herbarium in the region where the plant was collected.

b) Leaves stored in silica gel

Silica gel is a hygroscopic material that is used to remove all moisture from plant material. It is thus the best method to effectively conserve DNA for further molecular work. Silica gel can be obtained from chemical companies. For further information on the sourcing of this chemical, feel free to contact us for a list of suppliers. Please note that although this product is not harmful, contact with the skin is best avoided.

Silica-dried leaf material is sent to Canada for sequencing the two relevant barcoding genes (rbcLa & matK). As this data remains your property, you will be able to access it via BOLD. For more information on data release and protection, please refer to the BOLDSystems.

c) Collecting information

The minimum identifying information required for plant samples includes:

  • Date of collection
  • The botanical family of the plant collected
  • The GPS position / precise locality
  • Collector information

Naturally, additional information is beneficial to each collection. Please refer to the sample sheet for more information (Download).

The above information, will be used to add your collection to the UJ-ACDB DNA bank. This is accessible online on the DNA bank page.

For creating your own project on BOLD you can follow the tutorial available on the system or contact us.

Herbarium Voucher Visual Protocol:

ACDB recommends collection of plant specimens that have either fruits, seeds or flowers in order to check field identification. Sterile material should be collected only if the collector can provide an utterly reliable identification. The herbarium specimen must be labelled with a unique voucher number. (i.e. collectors initial + collecting number from 1 to ∞).

Leaf Material for Silica Storage Visual Protocol:

It is compulsory that leaf material be collected from a SINGLE plant specimen. Labelling must contain the exact voucher name used for the herbarium specimens.

For each collection, enough (but not too much) plant material must be collected to perform at least one DNA extraction (0.3 g of dry leaf material is required per extraction). Too much material in a collection envelope might result in leaves becoming rotten, and therefore contaminated by fungi.

As examples:

A plant with a 4-6 cm x 3×5 cm leaf requires six to seven leaves stored in silica.

In the case of plants with very large leaves, a ¼ to 1/6 of the leaf cut in smaller fragments is sufficient.

In the case of succulent plants, it is strongly recommended that collectors peal and dry only the leaf surface. Removing the parenchyma will avoid extraction of low-quality DNA.

The most important protocol to follow when collecting material for DNA is ensuring that the plant material dries quickly. This is accomplished by cutting the leaves into smaller pieces, thus increasing the surface area. It is preferable to remove the midrib from leaf material before putting it into silica gel. The material is then placed in a Ziploc plastic bag with enough silica gel to ensure drying of the material in a couple of days. A few days after placing the leaves in silica, it is necessary to mix the bag’s contents by turning it upside down.

Once the material is dry, most of the silica gel can be removed from the sample and dehydrated for future use. Indicator silica gel should be used to help determine the overall “dryness” of the sample. Check the sample for signs of mold and add fresh silica gel if necessary. Once dry, the sample can be stored at room temperature, preferably in the dark, without degradation of DNA.

Collecting information

Collecting information must be recorded in the form available (Download) to enable us to transfer the data to the UJ-ACDB DNA Bank and Bold. Please follow the explanation provided on this samples sheet.