Southern Cross Plant Science, Southern Cross University, Lismore, NSW, Australia.
AgResearch NZ, Grasslands Research Centre, Palmerston North, New Zealand.
Sci Rep. 2020 Mar 19;10(1):5048. doi: 10.1038/s41598-020-61708-6.
The Proteaceae genus Macadamia has a recent history of domestication as a commercial nut crop. We aimed to establish the first sequence-based haploid-correlated reference genetic linkage maps for this primarily outcrossing perennial tree crop, with marker density suitable for genome anchoring. Four first generation populations were used to maximise the segregation patterns available within full-sib, biparental and self-pollinated progeny. This allowed us to combine segregation data from overlapping subsets of >4,000 informative sequence-tagged markers to increase the effective coverage of the karyotype represented by the recombinant crossover events detected. All maps had 14 linkage groups, corresponding to the Macadamia haploid chromosome number, and enabled the anchoring and orientation of sequence scaffolds to construct a pseudo-chromosomal genome assembly for macadamia. Comparison of individual maps indicated a high level of congruence, with minor discrepancies satisfactorily resolved within the integrated maps. The combined set of maps significantly improved marker density and the proportion (70%) of the genome sequence assembly anchored. Overall, increasing our understanding of the genetic landscape and genome for this nut crop represents a substantial advance in macadamia genetics and genomics. The set of maps, large number of sequence-based markers and the reconstructed genome provide a toolkit to underpin future breeding that should help to extend the macadamia industry as well as provide resources for the long term conservation of natural populations in eastern Australia of this unique genus.
坚果树属 Macadamia 是一种最近被驯化的商业坚果作物。我们旨在为这种主要为异花授粉的多年生树木作物建立第一个基于序列的单倍体相关参考遗传连锁图谱，其标记密度适合基因组锚定。我们使用了四个第一代群体，以最大限度地增加全同胞、双亲本和自交后代中可用的分离模式。这使我们能够组合来自 >4000 个信息性序列标记的重叠子集的分离数据，以增加由检测到的重组交叉事件代表的染色体组的有效覆盖。所有图谱都有 14 个连锁群，对应于 Macadamia 的单倍体染色体数，并能够将序列支架锚定和定向，以构建坚果树的拟染色体基因组组装。个别图谱的比较表明高度一致，在整合图谱内可以很好地解决小的差异。组合图谱集显著提高了标记密度和基因组序列组装锚定的比例（70%）。总的来说，增加我们对这种坚果作物遗传景观和基因组的了解是坚果树遗传学和基因组学的一个重大进展。图谱集、大量基于序列的标记和重建的基因组为未来的育种提供了一个工具包，这应该有助于扩大坚果树产业，并为澳大利亚东部该独特属的自然种群的长期保护提供资源。
