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Macadamia, a genus native to eastern Australia, includes four species: Macadamia integrifolia, M. tetraphylla, M. ternifolia, and M. jansenii. Only the first two species and their hybrids are widely cultivated for commercial production. Despite its growing significance as a global crop, macadamia has been domesticated from a narrow genetic base, mainly Hawaiian germplasm, which has limited its genetic diversity and resilience. This study aims to expand the genetic resources available for macadamia through high-quality genome assemblies of all four species.
A study (DOI: 10.48130/tp-0024-0029) published in Tropical Plants on 21 October 2024, helps widen the gene pool, increasing resilience while maintaining or enhancing the desirable qualities of macadamia nuts, such as flavor and oil content.
Researchers used PacBio HiFi long-read sequencing technology to assemble the genomes of four Macadamia species: M. jansenii, M. integrifolia, M. tetraphylla, and M. ternifolia, achieving sequencing depths between 27X and 42X. The assemblies produced highly contiguous genomes with N50 values exceeding 45 Mb, indicating excellent genome completeness. Among the species, M. integrifolia had the highest number of contigs, while M. tetraphylla had the least. BUSCO analysis confirmed genome completeness of over 97%, with most genes identified as single-copy. The study also conducted chromosome-level assemblies, with genome sizes ranging from 735 Mb to 795 Mb. M. tetraphylla had the largest collapsed assembly, while M. jansenii had the smallest. The researchers identified structural variations in chromosomes 9 and 10 across the species. Genome annotation revealed that 61% to 62% of the genomes consisted of repetitive elements, and the number of predicted genes ranged from 37,198 to 40,534. Notably, genes associated with fatty acid biosynthesis and antimicrobial properties were conserved across species. Comparative analysis identified significant structural differences between species, enhancing understanding of genetic diversity within the Macadamia genus. These insights lay the groundwork for improving macadamia breeding programs by leveraging the genetic diversity of wild species to address challenges such as disease resistance and climate adaptability.
According to the study’s lead researcher, Dr. Robert J. Henry, “Having access to the genomes of all four macadamia species offers unprecedented opportunities to improve crop resilience and productivity. This comprehensive genomic data provides the foundation for more informed breeding programs, which are crucial to meet the demands of a changing climate and growing global markets.”
This comprehensive sequencing of all four Macadamia species lays the groundwork for significant advancements in macadamia breeding, with the potential to boost global production and improve crop resilience. The new genomic data offer a critical tool for breeders and researchers working to secure the future of this economically important crop in a changing world.
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References
DOI
Original Source URL
https://www.maxapress.com/article/doi/10.48130/tp-0024-0029
Funding information
This project was funded by the Hort Frontiers Advanced Production Systems Fund as part of the Hort Frontiers strategic partnership initiative developed by Hort Innovation, with co-investment from The University of Queensland, and contributions from the Australian Government. RH was funded by the Australian Research Council (CE200100015).
About Tropical Plants
Tropical Plants (e-ISSN 2833-9851) is the official journal of Hainan University and published by Maximum Academic Press. Tropical Plants undergoes rigorous peer review and is published in open-access format to enable swift dissemination of research findings, facilitate exchange of academic knowledge and encourage academic discourse on innovative technologies and issues emerging in tropical plant research.
