Assessment of genetic diversity in a Morus germplasm collection using fluorescence-based AFLP markers

To meet various breeding objectives and to conserve the existing genetic re sources of mulberry for future use, the present study was undertaken to inv estigate the amount of genetic diversity and to establish the relationships between mulberry genotypes using fluorescence-based AFLP markers. Genetic diversity was estimated in 45 mulberry accessions from different eco-geogra phic regions of Japan and other parts of the world. Five primer combination s amplified an average of 110 AFLP markers per primer combination, ranging in size from 35 to 500 bp. A high degree of polymorphism was revealed by th ese combinations that ranged from 69.7 to 82.3% across all the genotypes st udied. Several rare genotype-specific bands were also identified which coul d be effectively utilized to distinguish different genotypes. The wide rang e in genetic similarity coefficients (0.58-0.99) indicated that the mulberr y germplasm collection represents a genetically diverse population. The phe netic dendrogram generated by the UPGMA method grouped 35 accessions into f our major clusters, which was in agreement with the results from convention al methods. Clustering of some genotypes into strictly separate groups was not readily apparent and no clear interrelationships could be depicted, in spite of their different geographic origin. In addition, AFLP analysis prov ided sufficient polymorphism for DNA typing and contributed additional insi ghts into the genetic structure of the mulberry germplasm. These results wi ll help in the formulation of appropriate strategies for conservation and v ariety improvement in mulberry, for which little or no knowledge of genetic diversity is currently available.