栽培稻与斑点野生稻不同基因组构成杂种的遗传、进化分析及应用评估

The deficiency of valuable genes and low genetic diversity of cultivated rice lead to the difficulty of increasing its yield greatly at present. At the same time, the abundant wild rice species in Oryza genus provide valuable germplasm resource for genetic improvement of cultivated rice and evolution research. Under the direction of breeding strategy ‘Using double superiority of wide cross and polyploid to breed super rice’, different ploidy levels and genome constitution hybrids between Oryza sativa and O.punctata were constructed in previous research. This hybrid system that included AB, AAB, AABB, AAAB, AAAABB and AAAABBBB, formed an integrated material system for rice breeding and evolution research. Preliminary results showed that there were obvious difference on morphology and agronomic characters among different materials. On this basis, the genetic characteristics of each material will be scientifically studied from the meiosis behavior of pollen mother cells, the homology and interaction between different genomes, the development of pollen, embryo sac and embryo, and the gene differential expression. The reason and mechanism of difference forming will be further summarized by synthesizing and associating all results. Then, the evolutionary advantage and application value of different ploidy level and genome constitution hybrid will be analyzed and evaluated. In theory, the results will provide important data for revealing the evolution relation between genomes of Oryza species, the interaction between different genomes after genome entire transforming and the key role of genome constitution balance in allopolyploidization. In practice, the results can confirm the application pathway and value of different materials, and also can provide theoretical basis and method instruction for taking full advantage of wild rice germplasm resource, allopolyploid rice breeding and distant heterosis utilization.

目前栽培稻优良基因贫乏，遗传多样性低造成难以大幅增产。而丰富的野生稻物种可为栽培稻遗传改良及进化研究提供宝贵资源。在“利用远缘杂交和多倍体双重优势选育超级稻”策略的指导下，前期成功构建栽培稻与斑点野生稻不同基因组构成的杂种体系（AB、AAB、AABB、AAAB、AAAABB），获知不同材料间表型差异明显。在此基础上，本研究将从减数分裂行为，基因组同源性与相互作用，花粉、胚囊及胚胎发育，基因差异表达等方面系统研究各材料的遗传特性，并综合关联分析差异机制，确定最具进化优势的倍性水平和基因组构成，评估不同材料的应用价值。研究结果在理论上可为揭示稻属物种基因组间的进化关系、整体基因组转移后基因组间的相互作用、基因组构成的平衡性在异源多倍体化过程中的关键作用等提供重要资料；在实践上则可明确不同材料的应用方向和价值，为野生稻种质资源充分利用、异源多倍体水稻育种及远缘杂种优势利用提供理论基础和方法指导。

本研究以栽培稻（AA）与斑点野生稻（BB）为基础构建不同基因组构成系列材料AB、AAB、AABB、AAAB、AAAABB，并从基因组构成及同源性、形态及农艺性状、气孔及光合生理特性、花粉母细胞减数分裂行为、花粉育性与活力、转录组测序及基因差异表达分析等方面系统研究了各材料的遗传特性及差异。GISH证实了杂种的真实性，减数分裂时期GISH发现A、B基因组染色体之间存在异配二价体，说明A、B基因组存在部分同源性，这为通过远缘杂交将斑点野生稻基因转移到栽培稻提供了遗传基础。形态上，不同倍性材料随着染色体组数倍增，具有籽粒变大、分蘖减少、茎秆变粗等变化趋势；同倍性而染色体组构成不同的材料，也存在较大差异。不同材料气孔大小随倍性增加而增大，气孔密度随倍性增加而减小，叶绿体含量随倍性增高有增加的趋势。随着倍性的增加，净光合作用速率有增加的趋势；同一倍性条件下，基因组构成不同，净光合速率也不相同。减数分裂行为研究显示，AB、AAB、AAAB减数分裂过程中染色体配对紊乱，高频率出现单价体、三价体等不正常配对形式，染色体分离过程中出现大量落后染色体。AABB的减数分裂最正常，其可育性也是最好的，说明基因组平衡性的重要性。花粉育性与活力观察表明，杂种AB几乎没有可育和有活力的花粉，绝大部分为典败花粉；杂种AAB、AAAB、AAAABB偶尔出现可育和有活力的花粉；AABB的可育花粉率和有活力花粉率最高。研究还对全部材料进行了转录组测序，对AB、AABB和AAAB，进行了全长转录组测序，获得基因差异表达和基因功能注释方面的丰富信息。另外，还进行了栽野杂种与栽培稻回交利用探索，发现通过不育杂种与栽培稻进一步回交可以获得回交后代，这为创造栽野异附加系、异代换系、易位系等育种中间材料及具有基础研究价值的材料创造了条件，为野生稻有利基因的利用奠定了基础，异源多倍体水稻的创造和利用为水稻育种开辟了新途径。