Local genetic diversity of sorghum in a village in northern Cameroon: structure and dynamics of landraces

Abstract

We present the first study of patterns of genetic diversity of sorghum landraces at the local scale. Understanding landrace diversity aids in deciphering evolutionary forces under domestication, and has applications in the conservation of genetic resources and their use in breeding programs. Duupa farmers in a village in Northern Cameroon distinguished 59 named sorghum taxa, representing 46 landraces. In each field, seeds are sown as a mixture of landraces (mean of 12 landraces per field), giving the potential for extensive gene flow. What level of genetic diversity underlies the great morphological diversity observed among landraces? Given the potential for gene flow, how well defined genetically is each landrace? To answer these questions, we recorded spatial patterns of planting and farmers' perceptions of landraces, and characterized 21 landraces using SSR markers. Analysis using distance and clustering methods grouped the 21 landraces studied into four clusters. These clusters correspond to functionally and ecologically distinct groups of landraces. Within-landrace genetic variation accounted for 30% of total variation. The average F(is) over landraces was 0.68, suggesting high inbreeding within landraces. Differentiation among landraces was substantial and significant (F(st) = 0.36). Historical factors, variation in breeding systems, and farmers' practices all affected patterns of genetic variation. Farmers' practices are key to the maintenance, despite gene flow, of landraces with different combinations of agronomically and ecologically pertinent traits. They must be taken into account in strategies of conservation and use of genetic resources.

Genetic variability characterisation of Tanzania sorghum landraces based on simple sequence repeats (ssrs) molecular and morphological markers

“…The high variability observed by this study can be attributed to farmers' practice of interspecific intercropping of sorghum landraces, which increases the chances of gene flow within and outside the genotypes (Barnaud et al, 2007). Seed exchange among farmers could be another contributing factor to high variation among sorghum landraces.…”

“…Both morphological and molecular markers are used to save this purpose. Morphological characterisation was the first method used by researchers to select superior genotypes, spring wheat (Briggs, 1991), barn swallows (Cadee, 2000), and maize (Beta and Corke, 2001;Geleta and Labuschagne, 2005;Barnaud et al, 2007). However, several studies show that morphological markers are not suitable for traits with low heritability and are highly affected by environments (Smith and Smith, 1992;Redfearn et al, 1999;Cadee, 2000).…”

Genetic diversity among sorghum landraces and polymorphism assessment of local improved varieties for stay-green trait

“…Billot et al (2013) found similar result on a collections maintained by self-pollination. In contrast, high Ho value (0.11) was observed by Barnaud et al (2007) when assessing samples obtained directly from landraces. Local accessions contain an important number of private alleles whereas no private alleles were observed in improved varieties.…”

Ethnolinguistic structuring of sorghum genetic diversity in Africa and the role of local seed systems

“…As in other large-scale assessments of sorghum genetic diversity (9,11,12), we included one individual per accession to infer population structure, and, as in ref. 8, we included more than one individual per seed lot for local-scale calculation of diversity indices, F ST among landraces, and NJ analysis.…”