AFLP Molecular Markers-based Genetic Diversity Analysis on 90 Avocado Germplasms

  Objective  Genetic relationship of 90 avocado (Persea americana Mill.) germplasms collected from Dehong, Baoshan, Xishuangbanna, Puer, and Honghe in Yunnan, China and Shan and Kachin States of Burma was analyzed based on AFLP molecular markers for breeding reference and resource information.

  Method   Genomic DNAs were extracted from the leaves of the avocado plants following the CTAB method. They were amplified using the sequence-related amplified polymorphism molecular markers to determine their genetic diversity and similarity. Separation of the amplified fragments was performed on 5% denaturing polyacrylamide gels stained with AgNO₃ to obtain the “0,1” matrix. The number of polymorphic loci, percentage of polymorphic loci, effective number of alleles, and indices of genetic diversity were estimated by POPGENE version 32. The genetic similarity estimated by NTSYSpc-2.11F was used for UPGMA (unweighted pair group method analysis) and PCA (principal component analysis) to classify the avocado germplasms.

  Result  Eight primers with strong polymorphism and high repeatability were screened from 24 AFLP primers generating a total of 1 165 bands. Of the bands, 1 163 (99.83%) showed polymorphism. On average, the number of effective alleles was 1.294 4; Nei's gene diversity (H), 0.209 5; and Shannon's information index (I), 0.353 0. At the genetic similarity index (GS) of 0.752, the germplasms were classified into 4 groups. A single avocado germplasm, No. 70, collected from Baoshan was placed in Group I. Group II had 22 germplasms; Group III, one germplasm, No. 59, from Xishuangbanna; and Group IV, the 64 remainders. The germplasms in Group IV were further divided into Subgroups A, B and C at GS of 0.763. A similar grouping result was obtained from the cluster analysis on the PCR data applied AFLP markers confirming these germplasms shared a high similarity within a same region.

  Conclusion  The 90 collected avocado germplasms were found to be relatively high in genetic diversity. Among them, No. 59 and 70 stood out as two most unique varieties.