Genetic and Phenotypic Diversity in Downy-mildew-resistant Sorghum (Sorghum bicolor (L.) Moench) Germplasm


Genetic and phenotypic diversity among randomly selected 36 downy-mildew-resistant sorghum accessions were assessed, the former using 10 simple sequence repeat (SSR) marker loci and the latter using 20 phenotypic traits. The number of alleles (a j ) at individual loci varied from five to 14 with an average of 8.8 alleles per locus. Nei's gene diversity (H j ) varied from 0.59 to 0.92 with an average of 0.81 per locus. High gene diversity and allelic richness were observed in races durra caudatum (H j  = 0.76, a j  = 4.3) and guinea caudatum (H j  = 0.76, a j  = 3.8) and in east Africa (H j  = 0.78, a j  = 7.2). The regions were genetically more differentiated than the races as indicated by Wright's F st. The pattern of SSR-based clustering of accessions was more in accordance with their geographic proximity than with their racial likeness. This clustering pattern matched little with that obtained from phenotypic traits. The inter-accession genetic distance varied from 0.30 to 1.00 with an average of 0.78. Inter-accession phenotypic distance varied from 0.01 to 0.55 with an average of 0.33. Eleven accession-pairs had phenotypic distance of more than 0.50 and genetic distance of more than 0.70. These could be used as potential parents in a sorghum downy mildew resistance-breeding program.

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Kamala, V., Bramel, P.J., Sivaramakrishnan, S. et al. Genetic and Phenotypic Diversity in Downy-mildew-resistant Sorghum (Sorghum bicolor (L.) Moench) Germplasm. Genet Resour Crop Evol 53, 1243–1253 (2006).

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Key words

  • Downy mildew
  • Genetic diversity
  • Microsatellite markers
  • Phenotypic diversity
  • Sorghum bicolor