Establishing a chromosome map for Spirodela polyrhiza, chromosome homeology and karyotype evolution within the aquatic, largely asexual Lemnoideae, a basic monocot group of potential economic importance

浮萍亚科（Lemnoideae）是单子叶植物泽泻目（Alismatales）中的一个单系亚科，是一种小型、表型简单的自由漂浮水生生物，具有非常快的营养繁殖。因此，一些物种被认为是有效的生物质生产，以产生生物燃料，喂养牲畜和（同时）清洁废水。浮萍亚科有5属37种。多根螺旋藻的基因组已被测序，作为浮萍亚科基因组的参考。我们已经证实了该物种的小基因组大小（158 Mbp/1C），2n=40染色体。该提案的目的是建立遗传组成，多样性和染色体组型的进化，为S。polyrhiza，和所有五个属的代表物种，显示可变的基因组大小和染色体互补。由于很少有性繁殖和缺乏遗传图谱，我们证实并部分校正了S。多根需要通过原位杂交排列成20个连锁群。然后，基于染色体特异性的S。Polyrhiza BAC池，将揭示染色体同源性和核型多样性和进化（染色体间和染色体内重排，倍性突变）之间的自然克隆的S。多根和其他浮萍亚科物种，显示不同的基因组大小和/或染色体数目以及不同的身体大小和幼化程度。用其他技术进行这种比较会复杂得多。本研究结果将有助于阐明浮萍无性系间的遗传多样性，并为浮萍这一潜在作物的应用研究提供可靠的依据。

Lemnoideae, a monophyletic subfamily within the monocot order Alismatales, are small and phenotypically simple free-floating aquatic organisms with very fast vegetative propagation. Therefore, some species are considered for efficient biomass production to generate biofuel, to feed livestock and (simultaneously) to clean waste water. The Lemnoideae comprise 5 genera of together 37 species. The genome of Spirodela polyrhiza has been sequenced as a reference for Lemnoideae genomes. We have confirmed the small genome size (158 Mbp/1C), and 2n=40 chromosomes for this species. The aim of the proposal is to establish the genetic composition, diversity and evolution of karyotypes for S. polyrhiza, and for representative species of all five genera, displaying variable genome sizes and chromosome complements. Because of rare sexual propagation and lacking genetic maps, the genomic contigs (which we confirmed and partially corrected) of S. polyrhiza need to be arranged into 20 linkage groups by means of in situ hybridisation. Then, comparative chromosome painting, based on chromosome-specific S. polyrhiza BAC pools, will reveal chromosome homeology and karyotype diversity and evolution (inter- and intrachromosomal rearrangements, ploidy mutations) between natural clones of S. polyrhiza and other Lemnoideae species that display different genome sizes and/or chromosome numbers as well as different body size and degree of neotenisation. Such comparison would be much more intricate by other techniques. Our approach will elucidate the genetic diversity between vegetative clones of duckweeds and provide a reliable basis for application-oriented research on this under-investigated potential crops.