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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Crop Germplasm Research » Research » Research Project #424404

Research Project: Innovative Genetic Approaches to Sorghum Germplasm Improvement and Analysis of Traits Critical to Hybrid Development

Location: Crop Germplasm Research

2018 Annual Report


Objectives
This project aims to utilize recent advances in high-throughput genotyping, bioinformatics, and molecular biology 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. Sorghum breeding stocks, landraces, and elite tropical sorghums will be phenotyped and genotyped with an amalgamation of approaches, and knowledge of the genetic basis for key traits that impact productivity will be acquired. New sorghum genetic stocks will be developed, characterized, and released with new genes and traits not presently available to sorghum breeders. Specifically, during the next five years the project will focus on the following objectives. Objective 1: Develop and use markers in molecular marker-assisted approaches to introgress day-neutral flowering response into elite tropical sorghums and thereby create new sources of temperate-zone adapted sorghum germplasm. Objective 2: Identify genes and alleles in sorghum breeding stocks for pollen fertility restoration, and exploit this information to accelerate development of new parental lines. Subobjective 2.A: Identify an exhaustive set of fertility restoration (Rf) and partial fertility (Pf) genes in cultivated sorghum using genetic linkage analysis, association mapping methodology, and bioinformatics. Subobjective 2.B: Elucidate the genetic and molecular basis of cytoplasmic male-sterility (CMS) in sorghum A1 cytoplasm by sequencing mitochondrial genes and transcripts in CMS- and normal cytoplasms, and examine the effect of Rf genes and unfavorable temperatures on the expression of CMS-associated genes.


Approach
The long-term goal of this project is to utilize recent advances in high-throughput genotyping, bioinformatics, and molecular biology 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. The challenge facing scientists is how to exploit the vast amount of knowledge and tools in molecular biology, genomics, and bioinformatics to accelerate the rate of genetic gain in applied breeding programs. We have targeted several agronomically critical objectives that include introgressing day-neutral flowering response into elite tropical sorghums to create new sources of temperate-zone adapted sorghum germplasm, and identifying genes and alleles in sorghum breeding stocks for pollen fertility restoration, and exploit this information to accelerate development of new parental lines. In ongoing collaboration with scientists at Texas A&M University and private sector plant breeders at MMR Genetic LLC, a classical breeding approach augmented with robust genomic and bioinformatics tools will be used to identify elite tropical sorghums and convert these lines to temperate adaptation. The approach developed under Objective 1 will introduce new germplasm and favorable genes for complex traits, including grain yield, into sorghum breeding programs in the USA and worldwide. In ongoing collaborations with our collaborators in Queensland and Perth, we will use genetic linkage analysis, association mapping methodology, and bioinformatics under Objective 2.A to identify an exhaustive set of fertility restoration (Rf) and partial fertility (Pf) genes. Under Objective 2.B, we will sequence mitochondrial genes and transcripts in CMS- and normal cytoplasms, and examine the effect of Rf genes and unfavorable temperatures on the expression of CMS-associated genes. Through the combined approaches outlined under Objectives 2A. and 2B. we will elucidate the genetic and molecular basis of cytoplasmic male-sterility (CMS) in sorghum A1 cytoplasm. The overall approach of objective 2 will permit breeders to exploit this information to accelerate development of new parental lines for hybrid production fields. Objectives 1 and 2 are complementary, and the knowledge gained under one objective will facilitate the success in all.


Progress Report
Work under this project during FY 2018 in collaboration with university partners resulted in significant progress in sorghum germplasm breeding, which included the advancement of a final set of temperate-zone adapted sorghum lines derived from tropical sorghum germplasm (Objective 1). The discoveries made by this collaborative team will facilitate ongoing efforts focused on exploiting molecular technologies in developing improved sorghum hybrids for effective utilization by farmers in all production areas of the world. During the life of this project significant accomplishments were made in functional comparison/analysis of the sorghum genome and in the mapping and cloning of genes controlling important traits in sorghum. Specific accomplishments under Objective 1 encompass converting nearly 150 tropical sorghum accessions to temperate adaptation utilizing a breeding scheme augmented with robust genomic and bioinformatic tools. Achieving this goal resulted in the release of new germplasm and favorable genes for complex traits including grain yield into sorghum breeding programs. The development of genomic resources under this project (Objective 1) also facilitated the high-resolution mapping of important agronomic traits and to the eventual allele mining of ma1, a flowering time gene critical to sorghum production in temperate climates. Significant accomplishments under Objective 2 were made towards elucidating the genetic and molecular basis of cytoplasmic male-sterility (CMS) in sorghum A1 cytoplasm by sequencing mitochondrial genes and transcripts in CMS- and normal cytoplasms. These efforts resulted in the identification of novel mitochondrial genes that are associated with male-sterility in sorghum A1 cytoplasm, which is critical to hybrid sorghum seed production worldwide. This project expired in FY 2018 and was replaced by 3091-21000-043-00D which is continuing and expanding upon the work.


Accomplishments
1. New sorghum breeding germplasm from converted tropical lines. 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 including most sorghum-producing regions of the U.S. ARS scientists at College Station, Texas, working with Texas A&M University collaborators, utilized classical plant breeding techniques to select for short stature, early flowering versions with the objective of making new elite inbreds available to the sorghum industry. From a large panel of converted germplasm, individual converted plants with potentially superior breeding value were selected and are being evaluated for the development of higher-producing sorghum hybrids for farmers in the U.S. and worldwide.