Location: Crop Germplasm Research
2020 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 fiscal year 2020 under Objective 1, cooperative work with researchers from ARS at College Station, Texas, and academia evaluated more than 200 sorghum lines from the U.S. Sorghum Collections. The cooperative team also converted sorghum lines and commercial hybrids for resistance to anthracnose, grain mold, and head smut. In addition, 476 recombinant inbred lines, derived from the cross of the anthracnose resistant lines SC265 and SC1103, with the susceptible parent RTx430, were evaluated in Texas fields for resistance against the anthracnose pathogen.
Under Objective 2, greenhouse evaluations were conducted to establish the virulence patterns of 10 isolates of the anthracnose and head smut pathogens. Work is also underway at the Texas A&M AgriLife Research Farm, Burleson County, Texas, to determine the efficacy of fungicides (Azoxystrobin and Pyraclostrobin) and an experimental biocontrol agent, Bacillus velezensis LP16S, on anthracnose and grain mold response and yield of one commercial sorghum hybrid (BH 4100). Results from these fungicide and biocontrol agent studies will be important in developing new procedures and protocols for effective disease management in sorghum.
Accomplishments
1. New sources of anthracnose, head smut, and downy mildew resistance in sorghum. Globally, anthracnose, head smut, and downy mildew cause annual economic losses in sorghum yield and seed quality amounting to hundreds of millions of dollars. The most appropriate strategy in controlling these fungal diseases would be the development of new disease-resistant sorghum varieties. ARS researchers at College Station, Texas, and Mayaguez, Puerto Rico, working with collaborators from Texas A&M University, evaluated a number of sorghum lines drawn from various sources, with a focus on identifying resistance to anthracnose, head smut, and downy mildew. The work established that a number of these lines are highly resistant to one or more of these diseases. This work is a significant advancement in sorghum disease research in that it provides sorghum breeders and other researchers with critical new germplasm that will be foundational in developing new, disease-resistant sorghum varieties for productive use in world agriculture.
2. New sources of grain mold resistance in sorghum. Grain mold is the most important sorghum disease worldwide, and annually causes losses amounting to hundreds of million dollars in yield and seed quality. The most effective control strategy to this disease complex is the use of resistant sources. ARS researchers at College Station, Texas, and Mayaguez, Puerto Rico, working with collaborators from Texas A&M University, evaluated the Sorghum Association Panel lines for resistance against several grain mold fungi, and also used genome-wide association analysis to identify annotated gene(s) that may play a role in grain mold resistance. The work identified three sorghum lines PI533871, PI576130, and PI656036, that were resistant to grain mold. Molecular techniques known as single-nucleotide polymorphisms (SNPs), also were tracked to the specific chromosome location based on the sorghum genome sequence. This work is significant because gene products that may play a part in grain mold resistance response were mapped to the nearest, or to a nearby known gene(s) in the ten sorghum chromosomes, and this will in turn provide a platform for testing the effectiveness of each gene listed for sorghum defense against grain mold disease complex. The work is aimed at developing productive and highly grain mold resistant sorghum for productive use in U.S. and world agriculture.
Review Publications
Kumi, F., Badji, A., Mwila, N., Odong, T., Ochwossemakula, M., Tusiime, G., Gibson, P., Biruma, M., Prom, L.K., Cuevas, H.E., Agbahoungba, S., Rubaihayo, P. 2019. New sources of sorghum resistant genotypes to downy mildew diseases in Uganda. Biodiversitas. 20(11):3391-3397. https://doi.org/10.13057/biodiv/d201136.
Prom, L.K., Isakeit, T., Radwan, G. 2019. Response to anthracnose and germination rate of Colletotrichum sublineola acervuli of greenhouse-grown sorghum. Journal of Agriculture and Crops. 5(12):266-269. https://doi.org/10.32861/jac.512.266.269.
Prom, L.K., Cuevas, H.E., Isakeit, T., Magill, C. 2020. Screening sorghum accessions for resistance against anthracnose and grain mold through inoculating with pathogens. Journal of Experimental Agriculture International. 42(1):73-83. https://doi.org/10.9734/jeai/2020/v42i130453.
Prom, L.K., Adamou, I., Haougui, A., Abdoulkadri, A.A., Karimou, I., Ali, O., Magill, C. 2020. Response of the set of anthracnose differentials to other foliar and panicle diseases in Niger. Journal of Agriculture and Crops. 6(1):1-4. https://doi.org/10.32861/jac.61.1.4.
Ahn, E., Odvody, G., Prom, L.K., Magill, C. 2020. Late growth stages of johnsongrass can act as an alternate host of Colletotrichum sublineola. Plant Health Progress. 21(1):60-62. https://doi.org/10.1094/PHP-11-19-0084-RS.
Prom, L.K., Haougui, A., Adamou, I., Abdoulkadri, A.A., Karimou, I., Ali, O., Magill, C. 2020. Survey of the prevalence and incidence of foliar and panicle diseases of sorghum across production fields in Niger. Plant Pathology Journal. 19(2):106-113. https://doi.org/10.3923/ppj.2020.106.113.
Prom, L.K., Cuevas, H.E., Ahn, E., Isakeit, T., Rooney, W., Magill, C. 2020. Genome-wide association study of grain mold resistance in sorghum association panel as affected by inoculation with Alternaria alternata alone and Alternaria alternata, Fusarium thapsinum, and Curvularia lunata combined. European Journal of Plant Pathology. 157:783-798. https://doi.org/10.1007/s10658-020-02036-3.
