作物驯化和品种改良所选择的关键基因及其特点

近15~20年作物基因组学迅速发展,特别是第2代测序技术的普及,显著降低了测序成本,使单核苷酸多态性(SNP)分析和单元型区段(也称单倍型区段)分析渗透到生命科学的各个领域,对系统生物学、遗传学、种质资源学和育种学影响最为深刻,使其进入基因组学的全新时代。一批驯化选择基因的克隆,特别是对一些控制复杂性状形成的遗传基础及其调控机制的解析,更清晰地揭示了作物驯化和品种改良的历史,提升了人们对育种的认知,推动育种方法的改进。驯化和育种既有相似之处,也存在明显的差异。驯化选择常常发生在少数关键基因或位点,对基因的选择几乎是一步到位;而现代作物育种虽然只有100年左右的历史,但其对基因组影响更为强烈,是一些重要代谢途径不断优化的过程。随着生态环境或栽培条件的变化,育种选择目标基因(等位变异)会发生相应的变化或调整,因此对基因(等位变异)的选择是逐步的。此外,强烈的定向选择重塑了多倍体物种的基因组,使其亚基因组与供体种基因组明显不同。在群体水平上,系统分析驯化和育种在作物基因组和基因中留下的踪迹,凝炼其中的规律,将为品种改良和育种提供科学理论和指导,本文也简要介绍了"十三五"国家重点研发计划专项"主要农作物优异种质资源形成与演化规律"的基本研究思路。

Characteristics of Genes Selected by Domestication and Intensive Breeding in Crop Plants

Crop genomics made great progress in last 15–20 years. Second generation sequencing technology has dramatically reduced the cost of genome sequencing, brought life science into the times of genomics,and strongly promoted development of system biology, genetics, breeding and genetic resources. Single nucleotide polymorphism (SNP) and haplotype block analysis are currently widely used forexploring animal and plant genetic resources and breeding. Successful isolation of many important genes help us elucidate the history of crop domestication and breeding, andpredict the future of breeding. It has been changing the breeding concepts and strategies. Most crop cultivars used today have experienced two major steps of harsh artificial selection, i.e., domestication and breeding. Despite so many similarities between domestication and breeding, they are different in some aspects. Domestication relatively affects small regions of plant genome. The dramatic reduction of diversity is usually caused by bottleneck effect.Although the breeding history is only about 100 years, it has brought tremendous alteration in most crop genomes.Breeding targets much more genes than domestication.It is very difficult for further selection of alleles at domestication targeted locus, usually only one alleleiskept, which referred as fixed. However, it is not in the case of selecting alleles at breeding targeted locus. Few alleles can be present at the same time in varient populations and rotate at the same locus in cultivars released in different periods or regions. Frequency of favored alleles in new cultivars has been increased dramatically because of positive selection. In addition,strong artificial selection usually reshapes the sub-genomes in polyploid species, which made them quite distinct from donor’s genomes. Therefore, it would be a good strategy to highlight future breeding through elucidating the basic rule of crop genome and gene in reaction to artificial selection at the targeted regions. Here, webriefly review the current major strategies for dissection of genes, haplotype blocks as well as the major genes targeted in crop domestication and breeding selection. We also give a brief introduction on the mission and strategies for “formation and evolution mechanism of funder genotypes and famous cultivars in major crops”, a newly initiated national key research and development program of China.