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.
