Fixing heterosis in Canola using apomixis

无融合生殖是植物通过种子自然发生的无性生殖形式，它与有性种子形成有三个重要的发育事件不同，这些发育事件受遗传控制：(1)染色体未减少的卵细胞的形成（无减数分裂），(2)孤雌生殖（不受精）卵细胞的胚胎发育，以及(3)极核与雄性配子受精产生染色体平衡的胚乳（假配子）。这些事件一起产生无融合种子，胚胎是母株的遗传克隆。重要的是，这项技术在作物中的发展将使任何杂合基因型能够在一代内永久固定，而不考虑其基因组遗传和表型复杂性。多种用途的无融合生殖在农业长期以来被认为是重要的未来的可持续发展和粮食安全的步骤,因为这可能(我)显著缩短和降低风险所需的成本和时间产生新的作物品种,(2)它将使复杂multi-genic特征不能繁殖的固定使用目前的技术,和(3)它将使作物杂交育种和种子生产这并不存在(如脉冲作物和块茎)2。据估计，将无杂交技术引入水稻的市场改良价值每年可达25亿美元1。尽管无融合性很重要，但尚未成功地将其引入作物中，尽管在全球研究界（例如盖茨基金会，马克斯普朗克学会等）以及工业中正在进行深入研究。我的研究项目的长期目标是将无融合植物引入加拿大最重要的作物之一油菜（Brassica napus）。在这种情况下，我的实验室研究了Boechera属，一种油菜的野生亲戚，我们最近完成了有性和无融合基因组的染色体水平测序，并在一个正在进行的回交实验中证明，我们可以在一代内将无融合转移到有性植物上。重要的是，我们有一个核心无融合基因候选列表（见下文），因此我的计划的短期目标是：(i)筛选这些候选无融合基因的拟南芥突变系，以及（ii）在油菜（和其他芸苔属作物）中对这些候选无融合基因进行多重操作。在过去的15年里，我的实验室已经培训了大量的国际hqp，在目前的发现资助申请中，新的hqp将被培训，将我们的最新发现转移到油菜籽上，这将使加拿大处于全球作物植物研究的前沿。在育种计划中利用无杂交的影响将是巨大的，因为在一代中显示杂种优势的性状的固定将允许快速发展适应不断变化的环境条件、多样化的农业生态位和系统以及不断发展的市场的优良作物品种。

Apomixis is a naturally occurring form of asexual reproduction through seeds in plants which differs from sexual seed formation in three essential developmental events that are genetically controlled: (i) formation of a chromosomally unreduced egg cell (apomeiosis), (ii) parthenogenetic (without fertilization) embryonic development of this egg cell, and (iii) fertilization of the polar nuclei with male gametes to produce chromosomally balanced endosperm (pseudogamy)1. Together these events produce apomictic seeds with embryos that are genetic clones of the mother plant. Importantly, the development of this technology in crops would enable the permanent fixation of any heterozygous genotype, regardless of its genomic heredity and phenotypic complexity, in a single generation1. The multiple uses of apomixis in agriculture have long been recognized as important future steps for sustainability and food security, as it could (i) significantly shorten and lower risk in the costs and time required to produce new crop varieties, (ii) it would enable the fixation of complex multi-genic traits which cannot be bred using present technologies, and (iii) it would enable hybrid breeding and seed production in crops for which this does not exist (e.g. pulse crops and tubers)2. The estimated market improvement value of having apomixis introduced to rice alone would be $2.5 billion per year1. Despite its importance, apomixis has not yet been successfully introduced into crops, although it is under intense study in the global research community (e.g. Gates Foundation, Max Planck Society, etc.) as well as in industry. The long-term goal of my research program is to introduce apomixis into Canola (Brassica napus), one of Canada's most important crops. In this light, my lab studies the genus Boechera, a wild relative of Canola, and we have recently completed sequencing of a sexual and apomictic genome to the chromosome level, and have demonstrated in an ongoing backcrossing experiment that we can transfer apomixis to a sexual plant in a single generation. Importantly, we have a core apomixis gene candidate list (see below), and thus the short-term proposed objectives of my program are: (i) screening Arabidopsis mutant lines for these candidate apomixis genes, and (ii) multiplex manipulation of these candidate apomixis genes in Canola (and other Brassica crops). Over the last 15 years, my lab has trained a significant number of international HQPs, and in the present Discovery Grant Application new HQPs will be trained to transfer our latest discoveries to Canola, which would place Canada at the forefront of global crop plant research. The impact of utilizing apomixis in breeding programs would be enormous, as the fixation of traits demonstrating heterosis in a single generation would permit the rapid development of superior crop varieties adapted to changing environmental conditions, diverse farming niches and systems, and evolving markets.