Informativeness of minisatellite and microsatellite markers for genetic analysis in papaya

Abstract

The objective of this study was to evaluate information on minisatellite and microsatellite markers in papaya (Carica papaya L.). Forty minisatellites and 91 microsatellites were used for genotyping 24 papaya accessions. Estimates of genetic diversity, genetic linkage and analyses of population structure were compared. A lower average number of alleles per locus was observed in minisatellites (3.10) compared with microsatellites (3.57), although the minisatellites showed rarer alleles (18.54 %) compared with microsatellite (13.85 %). Greater expected (He = 0.52) and observed (Ho = 0.16) heterozygosity was observed in the microsatellites compared with minisatellites (He = 0.42 and Ho = 0.11), possibly due to the high number of hermaphroditic accessions, resulting in high rates of self-fertilization. The polymorphic information content and Shannon-Wiener diversity were also higher for microsatellites (from 0.47 to 1.10, respectively) compared with minisatellite (0.38 and 0.85, respectively). The probability of paternity exclusion was high for both markers (>0.999), and the combined probability of identity was from 1.65(-13) to 4.33(-38) for mini- and micro-satellites, respectively, which indicates that both types of markers are ideal for genetic analysis. The Bayesian analysis indicated the formation of two groups (K = 2) for both markers, although the minisatellites indicated a substructure (K = 4). A greater number of accessions with a low probability of assignment to specific groups were observed for microsatellites. Collectively, the results indicated higher informativeness of microsatellites. However, the lower informative power of minisatellites may be offset by the use of larger number of loci. Furthermore, minisatellites are subject to less error in genotyping because there is greater power to detect genotyping systems when larger motifs are used.