Massive Sorghum Collection Genotyped with SSR Markers to Enhance Use of Global Genetic Resources

Abstract

Large ex situ collections require approaches for sampling manageable amounts of germplasm for in-depth characterization and use. We present here a large diversity survey in sorghum with 3367 accessions and 41 reference nuclear SSR markers. Of 19 alleles on average per locus, the largest numbers of alleles were concentrated in central and eastern Africa. Cultivated sorghum appeared structured according to geographic regions and race within region. A total of 13 groups of variable size were distinguished. The peripheral groups in western Africa, southern Africa and eastern Asia were the most homogeneous and clearly differentiated. Except for Kafir, there was little correspondence between races and marker-based groups. Bicolor, Caudatum, Durra and Guinea types were each dispersed in three groups or more. Races should therefore better be referred to as morphotypes. Wild and weedy accessions were very diverse and scattered among cultivated samples, reinforcing the idea that large gene-flow exists between the different compartments. Our study provides an entry to global sorghum germplasm collections. Our reference marker kit can serve to aggregate additional studies and enhance international collaboration. We propose a core reference set in order to facilitate integrated phenotyping experiments towards refined functional understanding of sorghum diversity.

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

“…S4A) (F ST = 0.06, P < 0.01) was all relatively weak compared with the differentiation among the populations inferred with InStruct (n = 143 with Q > 0.90) (F ST = 0.21, P < 0.01). Moreover, as in other continent-wide assessments (9,12) we found that the differentiation among accessions belonging to the five discrete basic races (n = 82) was relatively weak (F ST = 0.13, P < 0.01) compared with the differentiation among the inferred populations. Thus, social and cultural factors reflected in the distribution of language families appear to be the strongest structuring factors behind the continent-wide pattern.…”

“…An obvious caveat in our case is that, during both the 1983 collecting and the 2010/2013 collecting of nyithin, we were unable to sample the full range of landraces included in the nyithin landrace complex in the Pari folk taxonomy. Furthermore, ex situ conserved accessions have undergone purification and forced selfing during regeneration (9), resulting in reduced heterozygosity compared with the original landrace. Thus, we limit our inference of the detected patterns to say that there is no evidence for loss of genetic diversity within nyithin.…”

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

“…In fact, since the collection in 1999, the accessions have been regularly regenerated by enforced self-pollination. 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.…”

“…The diversity was higher than that (He=0.37) reported by Barro-Kodombo et al (2008) on grain sorghum and slightly below the value (0.47) reported by Nebie (2014) on sweet stem sorghum. The genetic diversity values (0.674 and 0.61 respectively) reported by Billot et al (2013) and Sawaodgo (2015) were all beyond the values found in the present study. This weak diversity may be due to the relatively small number of accessions used here compared to the large number (3367) used by Billot et al (2013).…”

“…The genetic diversity values (0.674 and 0.61 respectively) reported by Billot et al (2013) and Sawaodgo (2015) were all beyond the values found in the present study. This weak diversity may be due to the relatively small number of accessions used here compared to the large number (3367) used by Billot et al (2013). It may also be due to the number and type of microsatellite markers used in the present study.…”