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

合作伙伴：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（IITA），乌干达]木薯和香蕉/大蕉是发展中国家粮食安全的重要作物，特别是在撒哈拉以南非洲地区。通过育种来改善这些作物是极具挑战性的，因为它们的世代时间很长，而且缺乏产生一致性状的纯自交系。生产双单倍体植物的能力只包含一组亲本染色体，可能会彻底改变香蕉和木薯等慢循环作物的育种。然而，目前尚无方法使这些作物产生双倍单倍体。最近在模式植物拟南芥中发现了一种产生单倍体的新策略。该策略是基于在细胞分裂过程中精确遗传所需的着丝粒蛋白的突变。当含有有缺陷的着丝粒蛋白（CENH3）的拟南芥植株与野生型或正常植株杂交时，来自突变体的染色体被消除，产生单倍体，只有来自野生型亲本的染色体。本项目的目标是开发这种新的着丝粒工程技术，用于木薯和香蕉的双倍单倍体生产。为了实现这一目标，单倍体木薯和香蕉将通过下调CENH3的表达并表达一种改变的转基因蛋白来实现。将表达改变的CENH3蛋白的转基因植株与野生型杂交，筛选单倍体个体。单倍体植物将利用基因组学方法进行鉴定，并转化为可育的二倍体进行育种。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。本研究开发的双单倍体生产方法有可能改变香蕉和木薯的育种，促进这些重要作物的合理改良。该技术产生的纯合子植株可以加速有利性状的渐渗和健壮杂交的发育。该项目的结果将确定该技术在其他慢循环粮食安全作物（如甘薯和山药）上的可行性。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，方法是对CIAT和IITA的研究人员进行基因组学和细胞遗传学技术方面的培训，并提供职业发展的机会，包括在科学和小组会议上发表演讲以及指导本科生。来自代表性不足群体的学生的参与将通过美国国立卫生研究院资助的MARC项目和加州大学戴维斯分校少数族裔丰富的生物学本科学者项目来促进。将举行年度会议，将教育推广活动扩大到哥伦比亚和乌干达的场址，在会议上，专业人员将发表关于植物育种的一般兴趣讲座。结果和可用序列、试剂和种质的描述将在项目网站（待建设；可通过http://biosci3.ucdavis.edu/FacultyAndResearch/FacultyProfile.aspx?FacultyID=182访问）上进行描述，并通过植物研究会议、出版物进一步传播，并通过现有的CIAT和IITA计划向木薯和香蕉育种者进行宣传。本项目产生的数据包括木薯和香蕉CENH3基因的核酸序列，将通过GenBank发布，以及通过项目网站对选育品系进行基因分型标记。分子试剂包括基因构建和克隆，这些将从加州大学戴维斯分校免费获得。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、非转基因双单倍体木薯和香蕉植物，将通过CIAT和IITA向公众开放。

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.