Genetic diversity within and among southern African provenances of Uapaca kirkiana Müell. Årg using morphological and AFLP markers

摘要

Domestication of Uapaca kirkiana Müell. Arg is a high priority for improving rural livelihoods of smallholder farmers in southern Africa. Domestication efforts require knowledge of adaptive traits and intra-specific variation. Morphological traits and amplified fragment length polymorphic (AFLP) markers were used to assess genetic variation in twelve provenances of U. kirkiana collected from southern Africa. Assessment of morphological traits showed significant differences (P < 0.05) between provenances. Provenances from Zimbabwe and Zambia showed faster growth than those from Malawi (except Phalombe) and Tanzania. Morphological traits exhibited strong genetic differentiation between provenances and within provenances. The degree of provenance differentiation of traits (Q _ST = 0.03–0.139, Q _ST mean = 0.092) was in the same range with that of AFLP loci (F _ST mean = 0.089) detected among provenances and within provenances (0.002 < F _ST < 0.259). The differentiation for some morphological traits could be attributed to local adaptation and human selection of the U. kirkiana trees at the site of origin. Mean Nei’s (H) genetic diversity of AFLP showed high diversity within the provenances (H = 0.181–0.321, H mean = 0.256). An analysis of molecular variance (AMOVA) revealed higher genetic variation (90.8%) within provenances than among provenances (9.2%). There was no geographical pattern of variation in growth and morphological traits among the seed sources. Chipata provenance from Zambia was the most diverse while Mapanzure from Zimbabwe was the least diverse, though it was superior in height and earliest in fruiting. The pattern of genetic diversity indicates low selection in some areas and high gene flow which would be counteracting it. Therefore regional and country collections and conservation strategies should consider differences by focussing on the main range of the species by paying particular attention to unique populations within countries.