ARS | Publication request: Response of sorghum accessions from Chad and Uganda to natural infection by the downy mildew pathogen, Peronosclerospora sorghi in Mexico and the USA

Submitted to: Journal of Plant Diseases and Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 10, 2009
Publication Date: January 29, 2010
Citation: Prom, L.K., Montes-Garcia, N., Erpelding, J.E., Perumal, R., Medina-Ocegueda, S. 2010. Response of sorghum accessions from Chad and Uganda to natural infection by the downy mildew pathogen, Peronosclerospora sorghi in Mexico and the USA. Journal of Plant Diseases and Protection. 117(1):2-8.

Interpretive Summary: Downy mildew is a serious fungal disease of sorghum which can reduce the crop yield and quality, especially if susceptible sorghum lines are planted in areas where the disease occurs regularly. In recent years, a new race of the sorghum downy mildew fungus was identified in southeast Texas. As a result, sorghum lines from Chad, West Africa; and Uganda, East Africa were screened in Texas and Mexico to identify new sources of downy mildew resistance. Several sources of downy mildew resistance were identified. Six accessions: PI282860, PI282864, and PI563505 from Chad and accessions PI297210, PI576386, and PI576395 from Uganda showed high levels of downy mildew resistance in Mexico and Texas. This work is significant because it has identified potential new sources of downy mildew resistance in sorghum that can be utilized by breeders in both countries to develop new lines and hybrids.

Technical Abstract: In this study, 78 accessions from Chad, West Africa and 20 photoperiod insensitive accessions from Uganda, East Africa were evaluated for downy mildew resistance in Ocotlan, Mexico in 2004 and 2005. Ninety-four of these accessions were also evaluated at two locations in Wharton County, Texas, USA, in 2005. Accessions were planted in a randomized complete block design with each sorghum accession replicated three times. Disease incidence was determined from natural infection. Disease incidence varied between locations, with the highest mean disease incidence observed for the Mexican evaluation. Germplasm from Chad also showed a higher mean disease incidence than germplasm from Uganda. Several sources of downy mildew resistance were identified. Three accessions PI282860, PI282864, and PI563505 from Chad were shown to possess high levels of downy mildew resistance in Mexico and Texas, whereas PI282843, PI282877, PI549196, and PI563438 also from Chad exhibited high levels of resistance to the disease in Texas. Accessions PI297210, PI576386 and PI576395 from Uganda also showed downy mildew resistance in Mexico and Texas. These sorghum accessions from Chad and Uganda can be utilized in breeding for downy mildew resistance in Mexico and Texas.