  Background: Diversity estimates in cultivated plants provide a rationale for
conservation strategies and support the selection of starting material for
breeding programs. Diversity measures applied to crops usually have been
limited to the assessment of genome polymorphism at the DNA level.
Occasionally, selected morphological features are recorded and the content of
key chemical constituents determined, but unbiased and comprehensive chemical
phenotypes have not been included systematically in diversity surveys. Our
objective in this study was to assess metabolic diversity in sesame by
nontargeted metabolic profiling and elucidate the relationship between
metabolic and genome diversity in this crop. Results: Ten sesame accessions
were selected that represent most of the genome diversity of sesame grown in
India, Western Asia, Sudan and Venezuela based on previous AFLP studies.
Ethanolic seed extracts were separated by HPLC, metabolites were ionized by
positive and negative electrospray and ions were detected with an ion trap mass
spectrometer in full-scan mode for m/z from 50 to 1000. Genome diversity was
determined by Amplified Fragment Length Polymorphism (AFLP) using eight primer
pair combinations. The relationship between biodiversity at the genome and at
the metabolome levels was assessed by correlation analysis and multivariate
statistics. Conclusion: Patterns of diversity at the genomic and metabolic
levels differed, indicating that selection played a significant role in the
evolution of metabolic diversity in sesame. This result implies that when used
for the selection of genotypes in breeding and conservation, diversity
assessment based on neutral DNA markers should be complemented with metabolic
profiles. We hypothesize that this applies to all crops with a long history of
domestication that possess commercially relevant traits affected by chemical
phenotypes.

Populations and Evolution;Genomics