Research Counterattack Against New Sorghum Fungus

Sorghum ergot (UR-get), an emerging fungus disease, faces more scrutiny at the Agricultural Research Service. ARS has released $100,000 in funds to expand research against the disease, found this year in Puerto Rico and Texas.

Grain sorghum is the nation’s number two feed grain. Sorghum ergot mainly threatens hybrid sorghum seed crops. Texas is the world’s major supplier of hybrid sorghum seed, and U.S. sorghum winter-nursery programs are concentrated in Puerto Rico. First found in the western hemisphere in 1995, sorghum ergot raced through South and Central America and the Caribbean. Scientists found it in Puerto Rico in February and Texas in March.

Ergot infects only unfertilized ovaries of female sorghum flowers, just before the flowers are ready to accept pollen. The fungus multiplies rapidly, and infected flowers can’t make seed. Instead, they exude honeydew, sticky droplets containing spores. Fungal structures are carried readily via harvested seed, wind, insects, machinery and people.

To combat the ergot, ARS will expand research at its Tropical Crops and Germplasm Research Laboratory, Mayaguez, P.R., and its Foreign Disease-Weed Research Laboratory, Frederick, Md. The research will be conducted in cooperation with Texas A&M University. The scientists will:

• Continue evaluating fungicide treatments that were tested by ARS scientists in Puerto Rico to kill ergot spores contaminating seed of breeding lines shipped to North America.

• Identify resistant plants from ARS’ germplasm collection. Resistant varieties would give growers long-term protection.

• Test a fungicide to suppress ergot infections on sorghum plants. Texas A&M University plans tests on commercial seed farms in south Texas and Mexico.

• Confirm the ergot’s identity. Principal sorghum ergot species are Claviceps sorghi from India and C. africana, of African origin, the species found so far in the western hemisphere. Evidence to date shows C. africana makes no toxins, unlike a different ergot species, C. purpurea.

ARS scientists in Puerto Rico operate a World Wide Web site as an ergot resource for scientists, industry and growers. The site, which includes photos of ergot on plants, is at:

http://www.sorghumgrowers.com/Research/sorghum.html

Scientific contacts: Morris Bonde, ARS Foreign Disease-Weed Research Laboratory, Frederick, Md., phone (301) 619-2860, fax 619-2880, bondem@ftdetrck-ccmail.army.mil

Jeff Dahlberg, ARS Tropical Crops and Germplasm Research Laboratory, Mayaguez, P.R., phone (787) 831-3435, fax 831-3386, jdahlberg@ars-grin.gov

Richard Frederiksen, Texas A&M University, College Station, Texas, phone (409) 845-1227, fax 845-6483, r-frederiksen@tamu.edu

Gary Odvody, Texas A&M Research and Extension Center, Corpus Christi, Texas, phone (512) 265-9205, fax 265-9434, wpodom1.corpus-ctr.godvody@wpo-smtp-gate.tamu.edu.