Development of nuclear SNP markers for genetic tracking of Iroko, Milicia excelsa and Milicia regia

Iroko, Milicia excelsa, is an economically important tropical hardwood species widely distributed in tropical Africa, from Ivory Coast in Western Africa to Tanzania in Eastern Africa. The species occurs at low densities in contrasting habitats such as rainforest and woodlands. Former studies using chloroplast and nuclear sequences, as well as nSSRs, revealed a strong differentiation within the species among West and Central African populations and the presence of three genetic groups in Central Africa (Daïnou et al. 2010, 2014). The genus Milicia also includes another species, M. regia, co-occurring with M. excelsa in West Africa. Both species can be identified genetically and morphologically (Daïnou et al. 2014), but identification is difficult in the field. Although the spatial genetic structure of the species is well described, it is mostly based on nSSRs. Despite their lower diversity, SNP markers provide several advantages including the uncomplicated standardization of data among laboratories and the easy, rapid and low-cost development of markers for large sets of loci. These features make SNPs the ideal markers for setting up genetic reference data for timber tracking (Blanc-Jolivet and Liesebach 2015; Degen et al. 2017; Jardine et al. 2016; Pakull et al. 2016). In this paper, we describe the development of a new set of nuclear SNPs on M. excelsa meant to be used for genetic timber tracking.