Molecular variability and phylogenetic relationships of guava (Psidium guajava L.) cultivars using inter-primer binding site (iPBS) and microsatellite (SSR) markers

The main objective of this research was to add genotyping information to previous phenotyping findings of Pakistani guava for the purposes of selective breeding. Inter-primer binding site (iPBS) and microsatellite (SSR) markers were used to assess the molecular variation and genetic structure of 51 promising Pakistani guava (Psidium guajava L.) genotypes which were then compared with 19 others from different geographical regions across the world. PCR of 6 iPBS primers (dominant markers) produced a total of 97 bands (96.63 % polymorphic) ranging from 100 to 2800 bp and the mean PIC for primers ranged from 0.1687 to 0.3522. The mean unbiased expected heterozygosity (0.183), Shannon's information index (0.275) and average fixation index (Fst or inbreeding) (0.925) indicated a high level of inbreeding among the accessions tested. Multi-locus DNA fingerprints using 18 SSR loci unambiguously differentiated all accessions and demonstrated an absence of duplicated samples. Diversity analysis revealed a total of 172 alleles (from 124 to 553 bp) ranging from 2 to 17 with a mean value of 9.56 alleles per locus. The mean unbiased expected heterozygosity (0.091), Shannon's information index (0.130) and mean inbreeding coefficient (0.854) also indicated a high level of inbreeding among the accessions. Ordination and cluster analysis from both iPBS and SSR markers showed that the genetic relationships between all accessions could be separated into geographic origin, specifically Pakistan, Mexico, Hawaii and India. Guava accessions cultivated in Pakistan and wild guava germplasm are highly divergent and possess abundant genetic diversity. The iPBS PCR-based genome fingerprinting technology used in this study is low-cost and provides an effective alternative in differentiating accessions of guava and their related species or genera.