Uzoma Chizoba Kabeya, Muamba Jerry Kabeya, Berhanu D. Bekele and Ivan L. Ingelbrecht
Cassava (Manihot esculenta Crantz) is a staple food for millions of people both in the tropics and subtropics and is increasingly being used as an industrial crop for the production of starch and other products. Currently, the number of molecular markers available for cassava genetic studies is limited. This study was conducted for the characterization of Expressed Sequence Tags (EST)-derived microsatellites or Simple Sequence Repeats (SSRs) in cassava (Manihot esculenta Crantz). Ninety six EST- SSRs previously identified insilico, were validated and screened for polymorphism using a diverse set of cassava genotypes. Using the optimized PCR conditions, these SSRs were screened for polymorphism using two diversity panels: panel 1 which comprises of cassava landraces and elite clones cultivated in Africa while panel 2 which comprises of cultivated cassava from Africa, Asia and Latin America, as well as wild Manihot species and castor bean (Ricinus communis) belonging to the family Euphorbiaceae. About thirty one SSRs were polymorphic in panel 1 while forty two were polymorphic in panel 2. A greater number of polymporhism was observed for panel 2 compared to panel 1, as expected since panel 2 comprises a greater genetic diversity. A total of seventy alleles were detected in panel 1 and ninety six for panel 2. The number of alleles per locus ranged from one to four by using these new polymorphic SSRs, with distinct genetic relationships between different genotypes. The cluster analysis showed consistency on the available information of the accessions under study, thus showing that the markers can be used for cassava genotyping
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