Diversity in the breadfruit complex (Artocarpus, Moraceae): genetic characterization of critical germplasm

Breadfruit (Artocarpus altilis, Moraceae) is a traditional staple crop in Oceania and has been introduced throughout the tropics. This study examines important germplasm collections of breadfruit and its closest wild relatives and aims to (1) characterize genetic diversity, including identification of unknown and duplicate accessions, (2) evaluate genetic structure and hybridization within the breadfruit complex, and (3) compare utility of microsatellite markers to previously reported amplified fragment length polymorphism (AFLP) and isozyme markers in differentiating among cultivars. Data for 19 microsatellite loci were collected for 349 individuals (representing 255 accessions) including breadfruit (A. altilis), two wild relatives (Artocarpus camansi and Artocarpus mariannensis), and putative hybrids (A. altilis × A. mariannensis). Accessions were of mixed ploidy and regional origin, but predominantly from Oceania. Microsatellite loci collectively had a polymorphic information content (PIC) of 0.627 and distinguished 197 unique genotypes sorted into 129 different lineages, but a single genotype accounts for 49 % of all triploid breadfruit examined. Triploid hybrids and diploid A. altilis exhibited the highest levels of diversity as measured by allele number and gene diversity. Most accessions (75 %) of unknown origin matched either a known genotype or lineage group in the collection. Putative hybrids all had genetic contributions from A. mariannensis but ranged in the level of genetic contribution from A. altilis. Microsatellite markers were found to be more informative than isozyme markers and slightly less informative, with regard to accession discrimination, than AFLP markers. This set of microsatellite markers and the dataset presented here will be valuable for breadfruit germplasm management and conservation.