Abstract
Macadamia is a high value nut crop that is recently domesticated, ideal for testing the effect of artificial selection. Here, we sequence the genome of Hawaiian cultivar ‘Kau’ and assemble into 794 Mb in 14 pseudo-chromosomes with 37,728 genes. Genome analysis reveals a whole-genome duplication event, occurred 46.8 million years ago. Gene expansions occurred in gene families involves in fatty acid biosynthesis. Gene duplication of MADS-Box transcription factors in proanthocyanidin biosynthesis are relevant for seed coat development. Genome re-sequencing of 112 accessions reveals the origin of Hawaiian cultivars from Mount Bauple in southeast Queensland in Australia. Selective sweeps are detected in macadamia cultivars, including genes involved in fatty acid biosynthesis, seed coat development, and heat stress response. Such strong effects of artificial selection in few generations reveals the genomic basis for ‘one-step operation’ for clonal crop domestication. The knowledge gained could accelerate domestication of new crops from wild species.
Highlights
Macadamia is a high value nut crop that is recently domesticated, ideal for testing the effect of artificial selection
We identified gene families related to fatty acid chains elongation (Fig. 4b), desaturation, and acyl transfer such as ketoacyl synthases (KAS), stearoyl-ACP desaturase (SAD), fatty acid desaturases (FAD), diacylglycerol acyltransferase (DGAT), and acyl-CoA:sn-glycerol-3-phosphate acyltransferase (GPAT) in 14 species (Supplementary Table 20)
Most modern macadamia cultivars are just two to four generations from their wild ancestors, and the most widely cultivated Hawaiian cultivars are just two generations away[13], which appeared to be in stage 1 of domestication[4]
Summary
Macadamia is a high value nut crop that is recently domesticated, ideal for testing the effect of artificial selection. Selective sweeps are detected in macadamia cultivars, including genes involved in fatty acid biosynthesis, seed coat development, and heat stress response. Such strong effects of artificial selection in few generations reveals the genomic basis for ‘one-step operation’ for clonal crop domestication. Long tracks of terminal homology were detected in 10 chromosomes of the cultivar ‘Singapore Spanish’ These are likely the result of multiple mitotic recombination events at the single-cell stage of the clonal reproductive tissues, crowns, suckers, or slips selected for propagation and provide strong support for ‘one-step operation’ of domestication in this linage.
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