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United States Department of Agriculture

Agricultural Research Service

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Location: Crop Germplasm Research

2011 Annual Report

1a. Objectives (from AD-416)
The objectives of this project are to: 1) identify and characterize different races of anthracnose (Colletotrichum sublineolum) based on their virulence patterns and by using molecular marker techniques; 2) evaluate sorghum germplasm for resistance to anthracnose; and 3) evaluate germplasm for resistance to grain mold, downy mildew, and head smut diseases.

1b. Approach (from AD-416)
1) Large-scale evaluations of the base collection through screening of the core (2,400 accessions), and the Sudan and Mali working (600 accessions) collections will be carried out. The core collection represents a random selection of the base collection. The Sudan and Mali working collections are accessions that breeders have selected based on agronomic performance and yield potential. Selected resistance sources will be screened over locations in different years to assess their horizontal disease resistance. 2) Two hundred fifty C. sublineolum single spore isolates collected over the past four years from various locations of the United States and Puerto Rico and are currently in long-term storage in the laboratory will be used. Host plant evaluations in the greenhouse will be conducted to establish the pathotypes of C. sublineolum. 3) Two closely related pathotypes of P. sorghi, P1 and P3, will be used to identify the differentially expressed unique sequences using standard AFLP technology as well as SSH. 4) A total of six cultivars, B1, BTx7078 and SC170-6-17 (susceptible lines), BTx635 (resistant line), SC140 and SC64 (their reaction to head smut is unknown), will be included in this study. Four inoculation methods--seed treatment, soil treatment, media placement, and syringe injection--will be employed. Four Texas isolates collected from College Station, Corpus Christi, Weslaco, and Beeville will be evaluated, with three replications for all four inoculation methods and all six cultivars simultaneously. In each replication, disease incidence (i.e., whether the inflorescence is replaced with sori or not) will be recorded.

3. Progress Report
In FY 2011, project work validated the virulence pattern of sorghum anthracnose isolates in the greenhouse to identify the different races of the pathogen. Several new races of the sorghum anthracnose pathogen were identified. Work on the sorghum head smut pathogen focused on virulence and molecular genotyping. Documentation of these new anthracnose and head smut races is important to breeders in their efforts to develop new, disease-resistant sorghum cultivars, and also to support ongoing efforts to manage these diseases through conventional disease control approaches. Other work in FY 2011 involved cooperative efforts with other scientists from ARS, academia, West Africa, and Mexico to evaluate more than 450 sorghum accessions chosen from the U.S. Sorghum Association Panel, converted sorghum lines, commercial hybrids, and exotic germplasm from Zimbabwe for resistance to anthracnose, downy mildew, grain mold, long smut, and rust. Several promising lines were identified that possess significant resistance to one or more of these important sorghum diseases. These lines may be useful in sorghum enhancement programs in the U.S. and other parts of the world.

4. Accomplishments
1. New method for assessing head smut resistance in sorghum. Head smut disease is a significant obstacle to profitable sorghum production in many areas due to the susceptibility of many commercial sorghum cultivars, and also likely to variation in/evolution of the causative pathogen. Experience has shown that the disease cannot effectively be controlled with either cultural practices or chemicals; therefore, the only option available is use of resistant cultivars. ARS scientists at College Station, TX, working with scientists at Texas A&M University, developed a new inoculation technique for assessment of large numbers of sorghum germplasm types for head smut resistance/susceptibility. The new technique (hypodermic injection of 18- to 20-day-old plants) is much more effective in identifying the smut resistance/susceptibility status of various sorghum types than is the technique previously used. The new technique will greatly facilitate work by sorghum breeders and other researchers to identify/develop new head smut resistant sorghums for use by farmers in those regions where smut is a significant obstacle to production.

2. New anthracnose, rust, and long smut resistant sorghum. Sorghum is an important grain crop used for human food and animal feedstuffs in many parts of the world. Sorghum diseases cause annual economic losses in yield and seed quality amounting to tens, if not hundreds, of millions of dollars. The most appropriate solution to major sorghum disease issues would be development of new disease-resistant sorghum varieties. ARS scientists at College Station, TX and Mayaguez, PR, working with collaborators from the Centre National de la Recherche Agronomique, Senegal, intensively studied more than 400 sorghum lines drawn from a number of sources, with focus on their inherent resistance to anthracnose, rust, and long smut. The work established that a number of these lines were 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.

Review Publications
Prom, L.K., Perumal, R., Erattaimuthu, S., Erpelding, J.E., Montes-Garcia, N., Odvody, G., Greenwald, C., Jin, Z., Frederiksen, R., Magill, C. 2011. Virulence and molecular genotyping studies of Sporisorium reilianum isolates in sorghum. Plant Disease. 95:523-529.

Radwan, G.L., Isakeit, T., Magill, C.W., Perumal, R., Prom, L.K., Little, C.R. 2011. Screening exotic sorghum germplasm, hybrids and elite lines for resistance to a new virulent pathotype (P6) of Peronsclerospora sorghi causing downy mildew. Plant Health Progress. Available: doi:10.1094/PHP-2011-0323-01-RS.

Montes-Garcia, N., Prom, L.K., Montes-Rodriguez, N., Garcia-Garcia, M., Pecina-Quintero, V., Diaz-Franco, A. 2010. Effect of systemic fungicides in the control of sorghum grain parasitic mycoflora. Mexican Journal of Phytopathology. 28(2):156-158.

Last Modified: 2/23/2016
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