Genetic diversity and gene flow among pearl millet crop/weed complex: a case study

Abstract

Weedy plants with intermediate (domesticated x wild) phenotypes occur in most pearl millet fields in West Africa, even in the absence of wild populations. They are usually found, in high numbers, both inside and outside of drills. Questions pertaining to the evolutionary dynamics of diversity within the pearl millet complex (domesticated-weedy-wild forms) were addressed in this study. The diversity of the different components of this complex sampled in two pearl millet fields in two villages of southwestern Niger was assessed at both molecular (AFLP) and morphological levels. Results show that, in both fields, weedy plants found outside of drills are morphologically distinct from weedy plants found inside drills, despite their close similarity at AFLP markers. The data suggest some introgression from the wild to the weedy population but nevertheless that the gene flow between the parapatric wild and domesticated populations is very low. This challenges the traditional view that regular hybridization between domesticated and wild pearl millets explains the abundance of these weedy plants despite farmers' seed selection. The level of genetic differentiation between fields from the two villages was low when considering domesticated and weedy plants. This could be explained by high gene flow resulting from substantial seed exchanges between farmers. The fact that it is very difficult for farmers to keep their own selected seeds, and the consequent substantial seed exchanges between them, is probably the main factor accounting for the maintenance and dispersal of weedy pearl millets in the region, even in areas where no wild forms have been observed.

Estimation of Genetic relatedness among the germplasm accessions of Pearl millet [<i>Pennisetum glaucum</i> (L.) R. Br.]

“…The clustering pattern of the accessions showed that though the genotypes represent a single geographical origin, exhibited greater genetic diversity among them. Clustering pattern of this study thus indicated that geographical diversity was not related with genetic diversity which is in agreement with Mariac et al (2006). Murthy and Arunachalam (1966) had already pointed out that there is no close correspondence between the geographic diversity and genetic diversity in number of crop plants.…”

Association Studies Identify Natural Variation at PHYC Linked to Flowering Time and Morphological Variation in Pearl Millet

“…SSR and AFLP genotyping: DNA was extracted from inbred lines and pearl millet varieties as previously described (Mariac et al 2006b). Pearl millet inbred lines were genotyped three to four times, using a set of 27 microsatellite loci (Oumar et al 2008) on plants from 2005 and 2006 field trials.…”

Domestication

“…africana) (Hilu and de Wet 1976), between pearl millet (Cenchrus americanus ¼ Pennisetum glaucum) and its wild ancestor (P. glaucum ssp. monodii) (Mariac et al 2006;Oumar et al 2008), between wild (Triticum dicoccoides) and cultivated (T. dicoccum) emmer wheat (Luo et al 2007), and between Oryza sativa and O. rufipogon (Huang et al 2012). …”