Submitted to: Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2006
Publication Date: 7/1/2006
Citation: Prom, L.K., Erpelding, J.E. 2006. Ergot response for the sorghum genotype IS8525. Plant Pathology. 5(2):216-220. Interpretive Summary: Sorghum ergot pathogen infects the unfertilized ovaries of the sorghum plant and therefore poses a serious threat to sorghum, especially in hybrid seed production fields. As a result, it is important to develop good and cost-effective means of controlling the disease. The best approach for controlling sorghum ergot is the use of host resistance. Two sorghum lines taken from IS8525 (juicy midrib and dry midrib) were tested for ergot resistance at different flowering stages. The treated sorghum heads were either bagged or not bagged. The lines were also crossed with male-sterile sorghum, ATx623. The IS8525 dry midrib was more resistant to ergot than the IS8525 juicy midrib. However, plants from the IS8525 lines crossed with ATx623 had very high levels of ergot. The results indicated that these lines do not have genes for ergot resistance, but will escape infection because of their flowering pattern. This work also has shown that bagging of ergot treated sorghum heads resulted in more disease infections than non-bagging. The screening technique used in this study can be utilized in mass screening of sorghum lines to identify resistant sources.
Technical Abstract: Experiments were conducted during the 2002 and 2003 growing season at Texas A&M Agricultural Research Farm near College Station, TX to determine the response of two germplasm lines derived from IS8525 (juicy midrib=IS8525J and dry midrib=IS8525D) to ergot infection. Ergot inoculation was conducted at different flowering stages with bagging versus non-bagging of inoculated panicles to determine the disease response of IS8525. On IS8525J, bagged panicles had mean ergot severity of 21.3% compared to 1.8% for non-bagged panicles. Mean ergot severity for bagged panicles for IS8525D was 3.9% and non-bagged was 1.0%. The stage of anthesis at the time of inoculation also affected the severity of the disease with the highest level of infection occurring when panicles were inoculated at 25% flowering. Ergot severity decreased at later flowering stages. Bagging of the inoculated panicles at the beginning of anthesis generally increased ergot severity on both lines. In both years, IS8525J was more susceptible to ergot than IS8525D. Male-sterile hybrids derived from crosses between the two IS8525 lines with A2Tx623 were evaluated in 2004 and found to be highly susceptible to ergot. These results suggest that the tolerance of IS8525 is due to floral morphological characteristics and the flowering pattern.