Location: Crop Germplasm Research
2020 Annual Report
Objectives
Objective 1: Utilize unadapted germplasm to increase genetic diversity of elite sorghum inbreds with improved agronomic performance through a collaborative effort involving public and private sector breeders.
Objective 2: Create nested association mapping resources from backcross-derived introgression populations to facilitate marker-assisted sorghum improvement.
Approach
A major challenge facing crop geneticists and breeders is how to develop strategies that combine genetic resources with the vast amount of knowledge and tools in genomics, marker-trait associations, high-throughput phenotyping platforms, genome editing, and bioinformatics to accelerate the rate of genetic gain in applied breeding programs. This project aims to utilize recent advances in high-throughput genotyping and phenotyping, knowledge of gene-to-phenotype trait relationships, whole genome profiles of genetic diversity within and between sorghum germplasm accessions, and emerging information management systems to acquire knowledge of sorghum genes and germplasm, and utilize this information to enhance the rate of genetic gain for complex traits such as grain yield through the development of new adapted breeding material. Utilizing a pre-breeding backcrossing scheme augmented with robust genomic and phenotypic tools, this project focuses on the improvement of sorghum hybrids by the introgression of desirable traits from unadapted and wild germplasm into elite sorghum inbreds, which will introduce new elite germplasm and favorable genes for complex traits, including grain yield, into sorghum breeding programs. The products of this research will include well-characterized elite sorghum inbreds with new genetic diversity and desirable traits, improved effectiveness of hybrid breeding programs through the introduction of new superior-performing diverse elite inbreds, and the development of public resources including backcross-nested association mapping (BC-NAM) populations and associated phenotypic and genotypic characterization to facilitate genomic-assisted breeding and innovative approaches for dissecting the genetic architecture of complex traits.
Progress Report
Work under this project during fiscal year (FY) 2020, in collaboration with university partners, resulted in significant progress in sorghum germplasm development, which addressed the four FY2020 milestones. Advancements were made towards developing genetically diverse sorghum germplasm through introgression breeding for use in applied breeding programs, and for development of genetic resources for basic researchers. The research represents significant progress towards introducing novel genetic diversity into elite sorghum inbreds, and towards developing the genetic resources for genomic prediction efforts that will enable the deployment of next generation genomic-based breeding tools in sorghum improvement programs. Specific accomplishments during FY2020 in support of Objective 2 include advancing and generating testcross hybrids of 180 elite BC1F4 selections originating from 20 Backcross-Nested Association Mapping (BC-NAM) populations, each with elite breeding value. Specific accomplishments under Objective 2 also include advancing the best individuals from 30 BC1F4 BC-NAM populations to develop new elite inbreds for grain and forage hybrids, and to construct genomic prediction models for grain yield within each BC-NAM population. To meet additional Objective 2 milestones, select inbreds from each of these 30 BC1F4 BC-NAM populations were distributed for phenotypic evaluation by ARS researchers at Lubbock, Texas, and university researchers at Clemson University, Kansas State University, and The University of California. Under Objective 1, a second set of unadapted female lines were used to generate new BC-NAM populations to address the limited genetic diversity present in elite female inbreds; BC1F2 populations with agronomic fitness were selected for generational advancement.
Accomplishments
1. Elite sorghum germplasm with novel genetic diversity. Sorghum is an important grain crop in many areas of the U.S. and other temperate regions worldwide. However, much of the potentially valuable sorghum germplasm is tropical in origin and does not successfully flower and produce seed in temperate environments, making these sources of genetic variability unavailable to many of the world's sorghum producing areas. ARS researchers at College Station, Texas, working with university collaborators, utilized classical plant breeding techniques and genomics tools to introgress novel genetic diversity into elite sorghum inbreds, with the objective of making new elite inbreds with superior hybrid performance. From large panels of converted tropical germplasm, and Backcross-Nested Association Mapping (BC-NAM) populations, elite sorghum plants with potentially superior breeding value, including enhanced grain and forage yield, were selected, evaluated and will be made available for use by breeders in developing higher producing sorghum hybrids for farmers in the U.S. and worldwide.
Review Publications
Horne, D., Patil, N., Klein, R.R., Miller, F., Hoffmann, L., Klein, P., Rooney, W. 2020. Registration of 11 diverse sorghum germplasm lines for grain and silage hybrid production. Journal of Plant Registrations. 14:179-188. https://doi.org/10.1002/plr2.20001.
Crosier, D., Hoffmann, L., Klein, P., Klein, R.R., Rooney, W. 2020. Predicting heterosis in grain sorghum [Sorghum bicolor (L.) Moench] hybrids using sequence-based genetic similarity estimates. Journal of Crop Improvement. https://doi.org/10.1080/15427528.2020.1748152.
Foster, T., Baldi, H., Shen, X., Burson, B.L., Klein, R.R., Murray, S., Jessup, R. 2020. Development of novel perennial Sorghum bicolor x S. propinquum hybrids. Crop Science. 60:863-872. https://doi.org/10.1002/csc2.20136.
