Isolation and characterization of polymorphic microsatellites in Cocos nucifera L.

Microsatellites or simple sequence repeats (SSRs) were isolated from coconu t (Cocos nucifera) and tested for polymorphism on restricted germplasm. Seq uencing of 197 clones from a cv. Tagnanan Tall-enriched genomic library sho wed that 75% contained a microsatellite, of which 64% were dinucleotide (GA /CT, CA/GT and GC/CG), 6% were trinucleotide, and 30% were compound repeats . Of 41 primer pairs tested on Tagnanan Tall genomic DNA, 38 gave the expec ted size product, two amplified two loci, and another gave a multilocus pat tern. On 20 coconut samples, the 38 SSRs detected 198 alleles (average: 5.2 alleles per microsatellite). Genetic diversity (D = 1 - Sigma p(i)(2)) val ues ranged from 0.141 to 0.809. Heterozygotes were present at high frequenc ies among some dwarf samples. Analysis of similarity matrices based either on shared alleles at each locus (simple matching coefficient) or on allele bands across all loci (Jaccard coefficient) showed similar results. Dwarfs grouped separately from tails and showed less genetic diversity. In a wider test on 40 samples, 8 SSRs detected 64 alleles (average: eight alleles per microsatellite). These results indicate the high potential of microsatelli tes to detect genetic diversity in coconut germplasm.