Genetic diversity assessment of avocado (Persea americana Mill.) germplasm from NIHORT genebank

Abstract Avocado ( Persea americana Mill.) is a fruit crop cultivated worldwide. This study assessed the genetic diversity of 15 avocado germplasm accessions conserved at the National Horticultural Research Institute in south-eastern Nigeria using 5 inter simple sequence repeat (ISSR) and 5 start codon targeted (SCoT) markers. Genomic DNA was extracted from young leaves using a modified CTAB protocol. Data analysis was performed in PowerMarker v 3.25 to determine allele frequency, gene diversity, cluster analysis, and polymorphic information content. A total of 41 polymorphic alleles were detected, with a mean of 4.1 alleles per locus. The polymorphism information content (PIC) ranged from 0.509 to 0.825, with a mean of 0.654. The genetic similarity coefficients ranged from 0.59 to 0.84. This indicates a moderate level of genetic diversity among the accessions. Cluster analysis using UPGMA grouped the accessions into two main clusters based on their geographical origins. Analysis of molecular variance (AMOVA) revealed that 99.3% of the genetic variation occurred within UPGMA clusters and only 0.7% between them (Phi = 0.007, P = 0.395, 9999 permutations), indicating an absence of significant geographic differentiation across the sampled accessions. This suggests a need for germplasm conservation and breeding programs to preserve genetic variability. The identified genetic variation can be used in breeding programs to develop better varieties with desirable traits. Future research could identify specific genetic markers linked to important agronomic traits, which would help improve breeding efforts for conservation strategies and future breeding. Both ISSR and SCoT markers detected moderate genetic diversity within the sampled NIHORT avocado accessions.