ARS | Publication request: Identification of a new race of Sporisorium reilianum and characterization of the reaction of sorghum lines to four races of the head smut pathogen

Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 17, 2010
Publication Date: July 1, 2011
Citation: Zhang, F., Ping, J., Du, Z., Cheng, Q., Huang, Y. 2011. Identification of a new race of Sporisorium reilianum and characterization of the reaction of sorghum lines to four races of the head smut pathogen. Journal of Phytopathology. 159:342-346.

Interpretive Summary: Head smut, one of the most important diseases of sorghum worldwide, is caused by the fungus Sporisorium reilianum. Several physiologic races occur on sorghum and corn, and new races continue to appear in the crop fields. Thus, it is necessary to monitor changes in disease dynamics and virulence of the pathogen. Recently, we have collected many isolates of the pathogen from various sorghum fields, and then experiments were conducted to characterize all collected isolates. Here, we report that a new physiologic race, named as race 4, was discovered in the sorghum field based on the bioassay. Today, use of resistant cultivars is the major IPM strategy for managing head smut diseases. In this study, a collection of 34 sorghum genotypes including commercial cultivars and germplasm lines were evaluated for resistance to the newly-described race of the head smut disease. According to host reaction to this race, resistance sources of sorghum were identified. The information presented herein will be valuable for the rational design of disease control strategies and facilitate development of more disease-resistant sorghum varieties to be used by sorghum producers in regions where head smut is a frequent problem.

Technical Abstract: Sporisorium reilianum is the causal agent of head smut on sorghum and maize. In order to effectively utilize host resistance to control this important disease in crops, it is necessary to monitor changes in disease dynamics and virulence of the pathogen. An outbreak of head smut was recently observed in a sorghum field, near Gaoping, Shanxi, China, and research was undertaken to characterize a putative new race of S. reilianum. A set of differential sorghum lines with resistance to several conventional races was used to characterize the newly collected isolate of S. reilianum. The reactions of differential cultivars / germplasm lines to the new isolate indicate that it is a new physiological race of S. reilianum. The new race is highly virulent on sorghum line A2V4 and its hybrid, Jinza 12, that are known as resistant to all existing Chinese races of S. reilianum, including races 1, 2, and 3. The new isolate of S. reilianum is different from all of the described races of the pathogen; thus, it is designated as race 4 of S. reilianum. Furthermore, a collection of 34 sorghum genotypes including commercial cultivars and germplasm lines was evaluated for disease reaction to the newly described race and the three known races of the pathogen.