BREAD: Fast Breeding for Slow Cycling Crops: Doubled Haploids in Cassava and Banana/Plantain

主要研究者：陈伟霆（加州-戴维斯大学）CoPI：Paul Chavarriaga和Hernan Ceballos [国际热带农业中心（CIAT），哥伦比亚]和Jim Lorenzen [国际热带农业研究所（IITA），乌干达]高级合作者：Leena Tripathi [国际热带农业研究所，乌干达]木薯和香蕉/大蕉是发展中国家粮食安全的关键作物，特别是在撒哈拉以南的非洲。通过育种来改良这些作物是极具挑战性的，因为它们的世代时间很长，而且缺乏能够产生一致性状的纯近交系。产生仅含有一组亲本染色体的双单倍体植物的能力可能会彻底改变香蕉和木薯等慢周期作物的育种。然而，在这些作物中没有可用于双单倍体生产的方法。最近在模式植物拟南芥中开发了一种产生单倍体的新策略。该策略基于细胞分裂期间精确遗传所需的着丝粒蛋白的突变。当含有缺陷型着丝粒蛋白（CENH 3）的拟南芥植物与野生型或正常植物杂交时，来自突变体的染色体被消除，得到仅具有来自野生型亲本的染色体的单倍体。本项目的目标是发展这种新的着丝粒工程技术，用于木薯和香蕉的双单倍体生产。为了实现这一点，将通过下调CENH 3的表达并在其位置表达改变的转基因蛋白来创建单倍体木薯和香蕉。将表达改变的CENH 3蛋白的转基因植物与野生型杂交，并筛选后代的单倍体个体。将使用基因组学方法表征单倍体植物并将其转化为可育二倍体用于育种。木薯和香蕉育种的根本改进有可能提高小农的粮食安全和经济福祉。本研究中开发的加倍单倍体生产方法可能会改变香蕉和木薯育种，并促进这些重要作物的合理改良。通过该技术产生的纯合植物可以加速有利性状的渐渗，并发育出有活力的杂种。该项目的结果将确定该技术用于其他慢循环粮食安全作物（如甘薯和山药）的可行性。 该项目还将为来自哥伦比亚、乌干达和美国的研究人员和学生提供独特的培训机会。哥伦比亚和乌干达的研究能力将得到加强，办法是对来自美洲热带农业研究中心和国际农业研究所的研究人员进行基因组学和细胞遗传学技术方面的培训，并提供职业发展机会，包括在科学和小组会议上作专题介绍，以及对本科生进行辅导。来自代表性不足群体的学生的参与将通过从NIH资助的MARC计划和加州大学戴维斯分校的少数民族丰富的生物学本科学者计划中借鉴来促进。将通过每年举行会议，将教育推广扩大到哥伦比亚和乌干达的场地，在会议上，PI将提出关于植物育种的一般性兴趣讲座。结果和可用序列、试剂和种质的描述将在项目网站（待构建;可通过http://biosci3.ucdavis.edu/FacultyAndResearch/FacultyProfile.aspx?访问）中描述FacultyID=182），并通过植物研究会议，出版物，并通过现有的CIAT和IITA计划向木薯和香蕉育种者推广进一步传播。 该项目将产生的数据包括木薯和香蕉中CENH 3基因的核酸序列（将通过基因库发布），以及通过项目网站对育种系的基因分型标记。分子试剂包括基因构建体和克隆，其将从UC Davis免费获得。将通过CIAT和IITA向公众提供遗传资源，包括育种种质、转基因单倍体诱导香蕉和木薯植物以及非转基因双单倍体木薯和香蕉植物。

PI: Simon Chan (University of California - Davis)CoPIs: Paul Chavarriaga and Hernan Ceballos [International Center for Tropical Agriculture (CIAT), Colombia] and Jim Lorenzen [International Institute of Tropical Agriculture (IITA), Uganda]Senior collaborator: Leena Tripathi [International Institute of Tropical Agriculture (IITA), Uganda]Cassava and banana/plantain are crucial crops for food security in the developing world, especially in sub-Saharan Africa. Improving these crops through breeding is extremely challenging, because they have a long generation time and lack pure inbreds that yield consistent traits. The ability to produce doubled haploid plants containing only one set of parental chromosomes could revolutionize breeding in slow cycling crops such as banana and cassava. However, there are no methods available for doubled haploid production in these crops. A novel strategy for producing haploids was recently developed in the model plant Arabidopsis thaliana. The strategy is based on mutations in centromeric proteins that are required for accurate inheritance during cell division. When Arabidopsis plants containing a defective centromere protein (CENH3) are crossed to wild type or normal plants, chromosomes from the mutant are eliminated to give haploids with only chromosomes from the wild type parent. The goal of this project is to develop this novel centromere engineering technology for doubled haploid production in cassava and banana. To accomplish this, haploid cassava and banana will be created by down-regulating the expression of CENH3 and expressing an altered transgenic protein in its place. Transgenic plants expressing altered CENH3 proteins will be crossed to wild type, and progeny will be screened for haploid individuals. Haploid plants will be characterized using genomics approaches and converted into fertile diploids for breeding. Radical improvements in cassava and banana breeding have the potential to increase food security and economic well-being for smallholder farmers. The doubled haploid production approach to be developed in this study could potentially transform banana and cassava breeding and facilitate rational improvement of these vital crops. Homozygous plants resulting from this technology can accelerate introgression of favorable traits, and development of vigorous hybrids. Results of this project will establish the feasibility of this technology for other slow-cycling food security crops such as sweet potato and yam. This project will also provide unique training opportunities for researchers and students from Colombia, Uganda, and the US. Research capacity in Colombia and Uganda will be strengthened by training researchers from CIAT and IITA in genomics and cytogenetic techniques, and providing opportunities for career development, including presentations at scientific and group meetings and mentoring of undergraduate students. Participation of students from underrepresented groups will be promoted by drawing from an NIH-funded MARC program and the minority-rich Biology Undergraduate Scholars Program at UC Davis. Educational outreach will be extended to Colombian and Ugandan sites by holding yearly meetings at which PIs will present general interest lectures on plant breeding. Results and a description of available sequences, reagents and germplasm will be described in a project website (to be constructed; accessible via http://biosci3.ucdavis.edu/FacultyAndResearch/FacultyProfile.aspx?FacultyID=182), and further disseminated through plant research conferences, publications, and outreach to cassava and banana breeders through existing CIAT and IITA programs. Data to be generated in this project include nucleic acid sequences for CENH3 genes in cassava and banana, which will be released through GenBank, and genotyping markers for breeding lines through the project website. Molecular reagents include gene constructs and clones which will be freely available from UC Davis. Genetic resources including breeding germplasm, transgenic haploid-inducing banana and cassava plants, and non-transgenic doubled-haploid cassava and banana plants will be made available to the public through CIAT and IITA.