Location: Tropical Crops and Germplasm ResearchTitle: Diversity of the breadfruit complex (Artocarpus, Moraceae): Genetic characterization of critical germplasm
|ZEREGA, NYREE - Northwestern University|
|WIESNER-HANKS, TYR - Chicago Botanical Garden|
|RAGONE, DIANE - National Tropical Botanical Garden (NTBG)|
Submitted to: Tree Genetics and Genomes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2014
Publication Date: 1/10/2015
Citation: Zerega, N., Wiesner-Hanks, T., Ragone, D., Irish, B.M., Scheffler, B.E., Simpson, S.A., Zee, F.T. 2015. Diversity of the breadfruit complex (Artocarpus, Moraceae): Genetic characterization of critical germplasm. Tree Genetics and Genomes. doi: 10.1007/s11295-014-0824-z.
Interpretive Summary: The breadfruit tree plays an important role as a staple agro-forestry food crop in many tropical regions of the world. As taxonomy, genetic diversity and genetic integrity in germplasm collections are still not well defined; a large number of breadfruit germplasm accessions were characterized using DNA fingerprinting. DNA samples, representing the genetic diversity conserved in U.S. national collections, were provided by the USDA’s National Plant Germplasm System and the National Tropical Botanical Garden in Hawaii. The DNA markers were able to place the different wild species, hybrids, and cultivars into genetically related groups, as well as identify errors in labeling, misidentifications and genetic redundancy in the collections. The tools and data presented in the study are important for considering links between genetic, morphological, and agronomic characters, for understanding patterns of breadfruit domestication and distribution and, to improve germplasm management and conservation of this important crop.
Technical Abstract: Breadfruit (Artocarpus altilis, Moraceae) is a traditional staple starch crop in Oceania and has been introduced throughout the tropics. This study uses microsatellite markers to characterize the genetic diversity of breadfruit and its wild relatives housed in the USDA National Plant Germplasm System and at the National Tropical Botanical Garden, home of the largest and most diverse breadfruit collection in the world. The study aims to 1) characterize existing breadfruit germplasm genetic diversity, including identification of unknown and replicate accessions, 2) evaluate genetic structure and hybridization within the breadfruit complex, and 3) compare utility of microsatellite markers reported here to previously reported 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 (A. camansi and A. mariannensis), and putative hybrids (A. altilis × A. mariannensis). The accessions were of mixed ploidy (2n, 3n) and regional origin, but predominantly from Oceania. The microsatellite loci had an average polymorphism information content (PIC) of 0.627, and were able to collectively distinguish 197 unique genotypes sorted into 129 lineages. All lineage groups were unique to a single taxon with the exception of four lineage groups represented by both A. altilis and hybrids. A single genotype accounts for 49% of all triploid breadfruit examined. Cultivar names were found to be more indicative of provenance than lineage group. Nearly half the accessions of unknown origin matched a known genotype in the collection, while others matched a known lineage but represented a unique genotype, represented entirely unique lineages. Analysis of genetic structure of the collections revealed five main clusters: one each representing the wild relatives, and the three remaining clusters divided among cultivated breadfruit. Putative hybrids all shared the A. mariannensis cluster and ranged in the level of genetic contribution from various A. altilis clusters. Microsatellite markers were found to be more informative than isozyme markers, and slightly less informative, with regard to accession discrimination, than AFLP markers. However, diversity may have been underestimated due to difficulty assessing allele dosage in triploids. Morphological diversity displayed in triploid Polynesian cultivars remains challenging to differentiate with molecular markers examined to date. Genetic characterization of the collection was able to identify labeling errors and misidentifications, and this set of microsatellite markers and the dataset presented here will be valuable for breadfruit germplasm management and conservation.