Molecular analysis of genetic variation in an indigenous drylands tree species, melia volkensii (Gurke.) and implications for its conservation

Abstract

Melia volkensii (Gurke.) is a popular tree in the East Africa's arid and semi arid lands (ASALs) valued because of its high quality termite resistant timber. It is fast growing thus a good choice for commercial forestry establishment. Goats eat its fruits and small-scale farmers appreciate the tree as an agro forestry species. The benefits from the tree and the risks of depletion looming over its natural distribution have made it a priority species for conservation and improvement programmes. However, information on its existing genetic diversity in order to propose appropriate conservation measures and improves breeding strategy.

Eight RAPD primers generated 38 scorable bands. Genetic distances were computed between all populations and used to construct neighbour-joining phenograms. An Analysis of Molecular Variance (AMOVA) was also used to partition genetic variation components between regions, between populations, and between individuals within populations.

The phenograms grouped the nine populations into two groups, one consisting of populations from eastern Kenya, and the other one consisting of coastal populations. AMOVA results indicated significant genetic differentiation between populations in the eastern and the coastal regions with 21.1%, (P<0.0002) of the total variation attributed to a difference between these areas. Little differentiation was recorded between populations (3.5%, P<0.0002) and 75.4%, (P<0.0002) of the total variation was attributed to variation within populations.

The difference between populations in the eastern and coastal regions could be due to eco-geographical association with genetic variation and therefore they should both be conserved to retain the full breadth of genetic variation of the species