Estimates of outcrossing rates in Moringa oleifera using Amplified fragment length polymorphism (AFLP)

Muluvi GM¹*, Sprent JI², Odee D³, Powell W⁴

¹Biochemistry Department, Kenyatta University, P.O.Box 43844, Nairobi, Kenya.

²Department of Biological Sciences, University of Dundee, DD1 4HN, Dundee, Scotland, UK.

³Farm Forestry Programme, Kenya Forestry Research Institute, P.O.Box 20412, Nairobi, Kenya.

⁴Dupont Agricultural Biotechnology, Delaware Technology Park, Suit Zoo, 1 innovation Way, P.O.Box 6104, Newark, DE19714-6104, USA.

Abstract

The mating system in plant populations is influenced by genetic and environmental factors. Proper estimates of the outcrosing rates are often required for planning breeding programmes, conservation and management of tropical trees. However, although Moringa oleifera is adapted to a mixed mating system, the proportion of selfing has not been previously estimated. The current work therefore, shows the use of AFLP markers in a mating system study of M. oleifera seed orchard. Data revealed a mixed mating system with a multilocus outcrossing rate (t_m) of 0.74. It further demonstrated that AFLP markers, though dominant with a lower information content than co-dominant markers are adequate for the study of the mating system in plant populations. The 26% selfing observed in M. oleifera can lead to overestimation of the proportion of additive genetic variance and appropriate adjustments are therefore required. However, the presence of selfing as well as early sexual maturity (6 months to 1 year) in M. oleifera provides an opportunity for developing inbred lines and hybridisation. Additionally, in designing M. oleifera seed orchards, randomisation and minimum distance between related individuals need to be worked out to maximise cross-fertilisation among unrelated clones and minimise selfing or mating among related ramets.

Key words: Moringa oleifera, mating system, outcrossing rates, amplified fragment length polymorphism.