[1] Univ Pretoria, Forestry & Agr Biotechnol Inst, Dept Biochem Genet & Microbiol, Private Bag X20, ZA-0028 Pretoria, South Africa
[2] Univ Copenhagen, Dept Biol, Sect Ecol & Evolut, DK-2100 Copenhagen, Denmark
[3] Lab Genet, Arboretumlaan 4, NL-6703 BD Wageningen, Netherlands