Location: Crop Germplasm Research
2018 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
In work in FY 2018, project Objective 1, cooperative research with scientists from ARS and academia evaluated 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. In addition, 123 recombinant inbred lines, derived from the cross of the anthracnose resistant line IS18760 with the susceptible parent PI609251, and 232 sweet sorghum lines were evaluated in the field for resistance against the anthracnose pathogen in Texas. Under project Objective 2, greenhouse evaluations were conducted to establish the virulence patterns of 15 isolates of the head smut pathogen from Texas. Work was also conducted in FY 2018 at two Texas locations to determine the effect of fungicides (Priaxor, Trivapro, Miravis Neo, Nexicor, BAS75106 and Quilt Xcel) on anthracnose and grain mold response and yield of two commercial sorghum hybrids (DKS37-57 and DKS37-07). The data obtained in these studies are under analysis/evaluation.
Accomplishments
1. New sources of anthracnose, grain mold, and long smut resistance in sorghum. Globally, these three diseases cause economic losses in sorghum yield and seed quality amounting to hundreds of millions of dollars each year. The most appropriate strategy for controlling these fungal diseases is development of new disease-resistant sorghum varieties. ARS scientists at College Station, Texas, and Mayaguez, Puerto Rico, working with collaborators from Kansas State University and the Centre National de la Recherches Agronomique, Senegal, evaluated a number of sorghum lines drawn from various sources, with focus on identifying resistance to anthracnose, grain mold, and long smut. 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 has identified critical new germplasm that will be foundational in the work by sorghum breeders and other researchers to develop new, disease-resistant sorghum varieties for productive use in world agriculture.
2. A new biocontrol agent against sorghum fungal pathogens. Although management strategies such as the use of resistant sources have been effective in most cases in reducing the impact of a number of sorghum fungal diseases, there is little information on the use of biocontrol agents as a disease management tool for sorghum. ARS scientists at College Station, Texas, used both plate and paper disc assays to test the activity of an unknown bacterium (called LP16S) against the destructive sorghum pathogens Fusarium thapsinum, Colletotrichum sublineola, Curvularia lunata, and Bipolaris sp. The work established that LP16S was capable of inhibiting both mycelial growth and spore germination of these pathogens. Identification of the bacterium using a molecular biology technique known as 16S rDNA sequence analysis characterized LP16S as most likely a Bacillus sp. Work is underway to determine the effectiveness of LP16S in suppressing sorghum diseases in the greenhouse. This work is significant because the use of biological control agents to minimize the impact of important sorghum diseases may be an effective alternative to the use of pesticides which can be harmful to the environment.
Review Publications
Prom, L.K., Magill, C., Droleskey, R.E. 2017. Aggressiveness of loose kernel smut isolate from Johnson grass on sorghum line BTx643. Journal of Agriculture and Crops. 3(11):94-96.
Prom, L.K., Cisse, N., Perumal, R., Cuevas, H.E. 2017. Screening of sorghum lines against long smut and grain mold pathogens. International Journal of Plant Pathology. 8:23-27.
Prom, L.K., Medrano, E.G., Isakeit, T., Jacobsen, R., Droleskey, R.E. 2017. A pictorial illustration of the inhibition of mycelial growth and spore germination of various sorghum fungal pathogens by a Bacillus species. Research Journal of Plant Pathology. 1(1):002.
Prom, L.K. 2017. Sorghum production and anthracnose disease management in future global energy and food security. Journal of Plant Diseases and Biomarkers. 1(1):1-3.
Prom, L.K. 2017. The role of plant pathology and plant pathology journals in future food security. Research Journal of Plant Pathology. 1(1):001.
Cuevas, H.E., Prom, L.K., Rosa, G.M. 2018. Population structure of the NPGS Senegalese sorghum collection and its evaluation to identify new disease resistant genes. PLoS One. 13(2). e0191877. Available: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0191877.
Cuevas, H.E., Prom, L.K., Copper, E.A., Knoll, J.E., Ni, X. 2017. Genome-wide association mapping of anthracnose (Collectotrichum sublineolun) resistance in the U.S. sorghum association panel. The Plant Genome. II:170099.
