Assessment of Genetic Diversity of Mexican Guava Germplasm Using DNA Molecular Markers

In Mexico, more than 20,000 ha are used to produce guava. Significant morphological and biochemical variation among and between guava (Psidium guajava L.) orchards of Mexico have been previously observed. The aim of this work was to evaluate the diversity of guava from different parts of Central and Northern Mexico by DNA markers, using 6 SSR loci and 5 AFLP primer combinations in an automatic sequencer. In this analysis a total of 57 individual accessions (maintained at the INIFAP Pabellon Campus in Aguascalientes) from 10 different regions of Mexico were included. As a result of AFLP profiling, a total of 233 bands were identified, of which 82% were polymorphic, but region-specific bands were not observed. The similarity index varied from 0.64 to 0.97, being most similar for samples from Aguascalientes and Guanajuato. By SSR marker analysis, a total of 79 alleles were identified. The observed number of alleles per locus varied from 8 to 21 with an average of 13 alleles per locus considering samples from all regions. The microsatellite mPgCIR161 revealed the highest frequency of homozygosity. The AFLP- and SSR-based dendrogram clusters the analyzed guava accessions into 2 main groups with at least 5 different sub-clusters without specific separation based on the region of origin. The results show that Mexican guava is diverse and that a more detailed analysis is needed in order to determine the level of genetic variability for conservation, management, and development of new varieties.