Genetic structure of the sorghum accession panel
Striga resistance is more prevalent in sorghum landraces from SSA
because of co-evolution of the host and the pathogen (Bellis et
al. 2020). Analysis of the geo-referenced origin of the SAP showed a
notable overlap with Striga distribution range in SSA (Figure 1a
and b). Further, the SAP was genetically diverse with representation
from all the major races and subraces of sorghum. The most common race
was caudatum and its subraces having 122 accessions with collections
mostly from Africa. Durra was also common with 79 collections from
eastern Africa and India. The least common race was bicolor with 10
accessions collected from eastern Africa (Figure S1a). To understand the
genetic structure of the SAP, we carried out population structure
analysis. We used both phylogenetic relationships and hierarchical
Bayesian clustering (HBC) to provide information on sorghum race
structure. In general, most races formed clusters based on their races
rather than geographical status as revealed by phylogenetic analysis
(Figure 1c). HBC further resolved the genetic structure of the SAP. At
the most likely K value (K=7) HBC grouped the panel into 5 distinct
clusters of durra, bicolor, guinea, caudatum and kafir caudatum. The
rest of the population was an admixture suggestive of multiple race
integrations in the development of the panel (Figure S1b). Based on
genetic diversity, and high representation from SSA, we determined that
the SAP collection was a good resource for Striga resistance
allele mining.