Location: Crop Germplasm Research
2017 Annual Report
Objectives
The primary objectives of this project are enhancement of sorghum productivity by identifying lines with multiple disease resistance genes and utilization of genomic DNA sequence information to assess variability in new and emerging fungal pathogens. Over the next 5 years we will focus on the following objectives.
Objective 1: Evaluate national and international sorghum germplasm resources for resistance to anthracnose, grain mold, and head smut diseases.
Subobjective 1.A. Identify new sources of resistance to anthracnose within converted and exotic sorghum.
Subobjective 1.B. Identify sources of resistance to grain mold.
Subobjective 1.C. Identify sources of resistance to pathotypes (P5 and P6) of Sporisorium reilianum, causing sorghum head smut.
Objective 2: Determine the population structure of diverse anthracnose (Colletotrichum sublineolum) and head smut (Sporisorium reilianum) isolates utilizing genomic DNA sequencing and phenotypic expression patterns of virulence on host differentials to characterize resistance to these diseases.
Subobjective 2.A. Determine the variability of C. sublineolum isolates based on genomic DNA sequencing.
Subobjective 2.B. Monitor changing populations and identify new pathotypes of C.
sublineolum present in the U.S. and Puerto Rico.
Subobjective 2.C. Determine genetic variability among diverse isolates of S. reilianum using genomic DNA sequence information.
Subobjective 2.D. Identify pathotypes of S. reilianum among head smut isolates collected from different sorghum growing regions in the U.S. and Puerto Rico.
Approach
Sorghum productivity and profitability in the U.S. are limited by several biotic constraints, most notably plant pathogens causing anthracnose, grain mold, and head smut. Presently, there is limited information on host-plant resistance to these pathogens within sorghum collections obtained from the center of origin (Ethiopia, Mali, and Sudan) or from other available sorghum germplasm. The focus of this project will be to mitigate the impact of these diseases by identifying host resistance in diverse sorghum germplasm. Germplasm that will be included in the evaluations will be collections or subsets of collections from Africa, newly converted, hybrids, parental, and elite lines. The goal will be to select accessions with host resistance to anthracnose, grain mold, and newly documented head smut pathotypes. All germplasm will also be evaluated for ten priority agronomic traits in order to provide breeders with new disease resistant, agronomic lines that will broaden the genetic base for hybrid development. Sorghum also has great potential as a biofuel source. However, biofuel crops require high plant densities that will increase the vulnerability of the crop to foliar and stalk diseases such as the hypervariable anthracnose pathogen, Colletotrichum sublineolum. Pathotypes of C. sublineolum and Sporisorium reilianum will be identified and characterized using genomic DNA sequencing to enhance our knowledge of the genetic potential for pathogenicity of these organisms. Determination of pathogen variability and identification of molecular markers associated with geographic distribution of pathotypes will provide researchers and breeders with tools needed to guide the deployment of appropriate resistant host varieties across the U.S. and abroad.
Progress Report
This is a new project which replaced the expired 3091-22000-030-00D and which is continuing and expanding upon the work of the precursor project. In FY 2017, project objectives to determine the population structure of diverse anthracnose (Colletotrichum sublineolum) and head smut (Sporisorium reilianum) isolates utilizing genomic DNA sequencing and virulence patterns were addressed. Greenhouse evaluations were conducted to establish the virulence patterns of 5 isolates of the anthracnose pathogen obtained from North Carolina and Georgia, and 5 isolates of the head smut pathogen from Texas. Cooperative work with scientists from ARS and academia to evaluate more than 200 sorghum lines from the U.S. Sorghum Collections, converted sorghum lines, and commercial hybrids for resistance to anthracnose, grain mold, and head smut progressed in FY 2017. Five hundred recombinant inbred lines, derived from the crosses of the anthracnose resistant lines QL3 and IS18760 with the susceptible parent PI609251, were evaluated in the field for resistance against the anthracnose pathogen in Texas. Work is also underway in Texas to determine the effect of fungicides (Headline, Priaxor, Quadris, Aproach, Topguard, Proline, and Quilt Xcel) on anthracnose and grain mold response and yield of two commercial sorghum hybrids.
Accomplishments
1. New sources of anthracnose, downy mildew, and grain mold resistance in sorghum. Annually, these three diseases cause economic losses in sorghum yield and seed quality amounting to hundreds of millions of dollars globally. The most appropriate strategy in controlling these fungal diseases would be development of new disease-resistant sorghum varieties. ARS scientists at College Station, Texas, and Mayaguez, Puerto Rico, working with collaborators from Texas A&M University and Kansas State University, evaluated a number of sorghum lines drawn from various sources, with focus on identifying resistance to anthracnose, downy mildew, and grain mold. The work established that a number of these lines are highly resistant to one or more of the diseases. This work is a significant advancement in sorghum disease research in that it provides to sorghum breeders and other researchers critical new germplasm that will be foundational in developing new, disease-resistant sorghum varieties for productive use in world agriculture.
