Origin and diversity of an underutilized fruit tree crop, cempedak (Artocarpus integer, Moraceae)

PREMISE OF THE STUDY: Underutilized crops and their wild relatives are important resources for crop improvement and food security. Cempedak [Artocarpus integer (Thunb). Merr.] is a significant crop in Malaysia but underutilized elsewhere. Here we performed molecular characterization of cempedak and its putative wild relative bangkong (Artocarpus integer (Thunb). Merr. var. silvestris Corner) to address questions regarding the origin and diversity of cempedak. METHODS: Using data from 12 microsatellite loci, we assessed the genetic diversity and genetic/geographic structure for 353 cempedak and 175 bangkong accessions from Malaysia and neighboring countries and employed clonal analysis to characterize cempedak cultivars. We conducted haplotype network analyses on the trnH-psbA region in a subset of these samples. We also analyzed key vegetative characters that reportedly differentiate cempedak and bangkong. KEY RESULTS: We show that cempedak and bangkong are sister taxa and distinct genetically and morphologically, but the directionality of domestication origin is unclear. Genetic diversity was generally higher in bangkong than in cempedak. We found a distinct genetic cluster for cempedak from Borneo as compared to cempedak from Peninsular Malaysia. Finally, cempedak cultivars with the same names did not always share the same genetic fingerprint. CONCLUSIONS: Cempedak origins are complex, with likely admixture and hybridization with bangkong, warranting further investigation. We provide a baseline of genetic diversity of cempedak and bangkong in Malaysia and found that germplasm collections in Malaysia represent diverse coverage of the four cempedak genetic clusters detected

Molecular markers and the management of tropical trees: The case of indigenous fruits

Millions of people in the tropics benefit from the harvest, cultivation and consumption of indigenous fruit trees (IFTs). Knowledge concerning the structuring of genetic variation within these species is crucial for sustainable use and conservation, but the availability of such information has been limited. By reference to case study species that are currently the subject of active domestication initiatives, in this essay we provide guidance for the suitable application of molecular marker methods for characterising IFTs. We discuss three particular areas where molecular markers are able to provide unique insights for further promotion activities: (i) in understanding the past domestication of taxa, (ii) in determining effective population sizes; and (iii) in assessing the value of a decentralised approach for future domestication. Despite the potential utility of molecular markers, a disjunction between assessment and practical application is evident, which reflects a lack of integration of laboratory research with other species promotion activities. Greater emphasis is required on team-based research and partnerships, more work should be undertaken in agricultural landscapes, and further research on mating systems and gene flow are crucial. Our essay provides a model for molecular marker studies on other trees that are important to rural communities in the tropics.Ramni Jamnadass, Andrew Lowe and Ian K Dawso