Genetic Diversity Study Of Vanilla Planifolia G. Jackson, Syn. V. Fragrans Crop Grown In Tanzania Using Molecular Techniques

ABSTRACT

Natural vanilla (Vanilla planifolia G. Jackson, syn. V. fragrans) is native to the

tropic forest of Mexico. It is now cultivated in humid tropical areas of Africa,

America, Asia and Australia continents. In Tanzania it had been cultivated since

1940s in Kagera region but decline in coffee prices in the world market in the 1990s

resulted into more cultivation of the vanilla crop as an alternate crop in Kagera and

Kilimanjaro regions. Vanilla which had a remarkable high price compared to coffee

was consequently spread and grown in Tanga, Morogoro regions and Zanzibar

Island. A study was undertaken to identify cultivars and examine the extent of

genetic diversity of Vanilla planifolia using molecular technique.

A total of 126 samples were randomly taken from Bulinda, Bakabuye and Kibona

villages in Kagera Region, Mkunazini and Donge village in Zanzibar Island and

Mudio and Kidia villages in Kilimanjaro Region. The deoxyribonucleic acid (DNA)

extraction method that was used in this research was the Dellaporta protocol.

DNA quantification was done by comparing band intensity of different

concentrations of standard genomic DNA markers using agarose gel electrophoresis.

For the optimization of PCR, three different components; dNTPs, Taq DNA

polymerase and MgCl2 were tested in different combinations.Ten primers were

selected for the Random Amplified Polymorphic DNA (RAPD) reactions.

The results revealed genetic distances of 0.667, 0.705 and 0.805 for Kagera,

Kilimanjaro and Zanzibar respectively for intra population diversity and 1.28 for

interpopulation diversity. This indicates a narrow genetic diversity. Similarly

altogether the 126 cultivars included in this study generated 53 bands of which only

27 were polymorphic this indicates a low level polymorphism.

The fact that the vanilla cultivars from Kilimanjaro and Kagera did not markedly

diverge genetically from the vanilla cultivars in Zanzibar island suggests a narrow

genetic diversity of populations and probably present cultivars have been derived

from common source parents and maintained over several decades. Exchange of

cultivars between plantations and seedling selection may also have played a role.