Population structure of the NPGS Senegalese sorghum collection and its evaluation to identify new disease resistant genes

Abstract

Sorghum germplasm from West and Central Africa is cultivated in rainy and high humidity regions and is an important source of resistance genes to fungal diseases. Mold and anthracnose are two important biotic constraints to sorghum production in wet areas worldwide. Here, 158 National Plant Germplasm System (NPGS) accessions from Senegal were evaluated for agronomic traits, anthracnose, and grain mold resistance at two locations, and genetically characterized according to 20 simple sequence repeat markers. A total of 221 alleles were amplified with an average of 11 alleles per locus. Each accession had a unique genetic profile (i.e., no duplicates), and the average genetic distance between accessions was 0.42. Population structure and cluster analysis separated the collection into four populations with pairwise FST values >0.15. Three of the populations were composed of Guinea-race sorghum germplasm, and one included multiple races. Anthracnose resistant accessions were present at high frequency and evenly distributed among the three Guinea-race populations. Fourteen accessions showed resistance to grain mold, and eight were resistant to both diseases. These results indicated that the NPGS of Senegal is a genetically diverse collection with a high frequency of disease resistant accessions. Nevertheless, its population structure suggests the presence of few sources of resistance to both grain mold and anthracnose, which are fixed in the germplasm. The phenotypic and genotypic information for these accessions provides a valuable resource for its correct use to broaden the genetic base of breeding programs.

Fig 1. Distribution of allele sharing genetic distance among 158 NPGS Senegal sorghum accessions.

Fig 2. Population structure analysis of 158 NPGS Senegalese sorghum accessions.

(A) The optimal number of populations was four based on the delta K method. (B) Hierarchical organization of the genetic relationships of the 158 Senegal accessions. (C) Collection sites of 107 Senegal accessions.

Fig 3. Neighbor-joining tree of 158 NPGS Senegalese accessions.

Admixture accessions are not colored. Red stars and blue check marks refer to anthracnose and grain mold resistant accessions, respectively.

Fig 4. Seed quality distribution of 158 NPGS Senegal sorghum accessions and three references lines.

Seed quality evaluations were completed at Isabela and Mayaguez, Puerto Rico, during the fall of 2014. Dashed lines indicate Tukey-Kramer HSD significant differences (p < .05) from PI 267548. ¹ Seed mold rating based on a scale of 1–5 where 1–2 are resistant and 3–5 are susceptible. ² Germination rate based on the percent of seeds that germinated after 10 days in flats containing Metro Mix 200 potting medium.