Genetic relationship analysis for avocado cultivars from Venezuelan germplasm bank (INIA-CENIAP) using molecular markers

Abstract

Avocado has been characterized using morphological and molecular traits, leading to establish three different horticultural groups: Mexican, Guatemalan, and West Indian. Microsatellites have allowed the identification of hybridization and/or backcross processes which have led to crop improvement. Reticulated phylogenies from evolutionary distances among species can also allow to identify hybridization and allopolyploid phenomena among accessions or species, but they were not conclusive to identify genetic kinship between pure and hybrid cultivars nor lineages in avocado. From 13 microsatellite markers, 96 accessions representing 49 cultivars were sampled from the Venezuelan avocado germplasm collection at the INIA-CENIAP bank in Maracay, Venezuela. Data were analyzed considering two groups: only pure cultivars and every sampled cultivar (pure and hybrids). In order to identify influential alleles in each data group, determination coefficients were obtained from PCA scores performed, identifying determination percentage for each allele and contrasting with the scatter plot. Based on the presence/absence character matrix of an allele for each microsatellite marker, reticulograms were obtained using the T-Rex software. Mexican (M) and Guatemalan (G) genotypes can be recognized and molecularly differentiated from WI. Polytomy between pure and hybrid Mexican specimens shows that the collection has three different lineages, at least, from different regions, and also West Indian accessions are represented from two different genetic groups. Genetic consistent cultivars were identified from clustering. Native Guatemalan × West Indian (G × WI) hybrid cultivars are genetically different from foreign G × WI in loci AVD006, AVD022, AVAG22, and AVAG25. This is a valuable tool for identifying alleles associated with Venezuelan avocado materials.