Isolation and characterization of polymorphic microsatellites in Cocos nucifera L.
2001
Rivera, R.L. | Edwards, K.J. | Barker, J.H.A. | Arnold, G.M. | Ayed, G. | Hodgkin, T. | Karp, A. (Philippine Coconut Authority, San Ramon, Zamboanga City (Philippines). Zamboanga Research Center)
Microsatellites or simple sequence repeats (SSRs) were isolated from coconut and tested for polymorphism on restricted germplasm. The study was conducted at the Long Ashton Research Station, Long Ashton, Bristol, United Kingdom using plant materials from the coconut genebank of the PCA-Zamboanga Research Center [Philippines]. Results indicated the high potential of SSRs in detecting genetic diversity in coconut germplasm. Sequencing of 197 clones fron a cultivar Tagnanan Tall-enriched genomic library showed that 75% contained microsatellite of which 64% were dinucleotide (GA/CT, CA/GT and GC/CG), 6% were trinucleotide and 30% were compound repeats. Of the 41 primer pairs tested on Tagnanan Tall genomic DNA, 38 gave the expected size product, 2 amplified 2 loci and another gave a multilocus pattern. Of the 20 coconuts samples, 38 SSRs detected 198 alleles for an average of 5.2 alleles/SSR while genetic diversity values ranged from 0.141 to 0.809. Heterozygotes were present at high frequencies among some dwarf samples. Analysis of similarity matrices based either on shared alleles at each locus (sample matching coefficient) or an allele bands across all loci (Jaccard coefficient) showed similar results. Dwarfs grouped separately from talls and showed less genetic diversity on a test of 40 samples, 8 SSRs detected 64 alleles averaging 8 alleles/SSR.
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