Wednesday, May 6, 2015

Barcoding local - Contributions by course participants (6)

And another guest post by a course participant. Jemilah Aliyu Ibrahim is a Senior Research Fellow at the National Institute for Pharmaceutical Research and Development in Abuja, Nigeria. Her area of interest are the complexities of the family Loranthaceae (mistletoes) in Nigeria. She leads the Institute's herbarium where she carries out and supervises identification of plant specimens for researchers, students and agencies. In addition she also documents indigenous knowledge on the use of plants for treatment of diseases and aims to verify such claims with appropriate laboratory studies. 

The Loranthaceae (mistletoes) is a family of parasitic plants that pose a serious threat to plantations and tended plants and impinges seriously on the productivity and the economic return of the host plants. Despite this, mistletoes are also medicinally very important in the treatment of ailments such as mental conditions, sterility, skin diseases, rheumatism, chest conditions and urino-genital problems, hypertension, diabetes, etc.  In Nigeria, leaves of mistletoes are packageed as herbal tea for treatment of some of the ailments mentioned above. The fruits also serve as food to some pollinators. 

In Nigeria, Loranthaceae poses serious challenges because the names available for most of the plants go only down to genus level. Characters for delineation and delimitation are overlapping either between the genera or within species. Observations made of specimens in the field and in herbaria also revealed very conspicuous similarities in the floral or vegetative features of some of these species which have made identification difficult. This has led to a high rate of wrong specific names being applied in many publications in Nigeria. The majority of herbal medicine producers labels their mistletoe remedies as just ‘mistletoes’ without referring to the specific name due to inadequate knowledge of the identity of the parasite used in the preparation. 

The above issues necessitated a revision of the family in Nigeria. Issues identified in the study are as follows:
1. Fifteen mistletoe species occur in Nigeria. Out of the 15 species, 7 could only be traced back to herbarium specimens. Some species found in the literature were neither found in the field nor traced to any herbarium specimen thereby raising serious issues about the conservation status of the species. 
2. There are wide phenotypic variations among individuals of the same species collected from different hosts in the same locality or different localities. 
3. The specimens of Tapinanthus globiferus from north-central, north-east to north-west zones might likely be harboring cryptic lineages evidenced from some clear morphological features. 
4. Most research works published on the plants in peer reviewed journals is likely based on wrong identifications.

All the issues mentioned above could be addressed by using DNA barcoding. The occurrence of the 15 recorded species needs to be confirmed and they require further documentation (at least one of these species is endemic to Nigeria). Secondly, DNA barcoding can be employed for routine identification because morphological characters are confusing and misleading. This will reduce the high rate of mis-identification observed and cases of adulteration of herbal remedies  can be avoided or reduced. Regulatory agencies can also use DNA barcoding to monitor genuineness of such herbal products.  Finally, DNA barcoding can be employed to determine if cryptic species occur in the Tapinanthus globiferus complex. 

Difficulties that might impede the use of this technique is the high cost of field surveys to collect representative specimens and this cannot be carried out by an independent researcher who does not have any sufficient funds, unless DNA can be extracted from herbarium specimens. Facilities for such studies are scarce and when available, it is too expensive and the technical Know-how is also lacking. 

Finally, when the above predicaments can be overcome, which I know it will be soon, then DNA barcoding will be a tool to watch out for in solving the taxonomic problems of this very important and highly medicinal family of Loranthaceae in Nigeria. 

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