Identification of a New Race of Sporisorium reilianum and Characterization of the Reaction of Sorghum Lines to Four Races of the Head Smut Pathogen

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 A 2 V4 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.

Response of Sorghum Accessions against Newly Documented Pathotypes 5 and 6 of Head Smut Pathogen, <i>Sporisorium reilianum</i>

“…Indira et al [4] identified 20 lines resistant to head smut including A7050, A232E, BICS 49, and Lian-Tang-Ai the Chinese pathotype 3. Further, PI961560 and SA281 were identified as resistant sources to all four Chinese head smut pathotypes [11]. In the United States, six converted sorghum accessions, including SC103-11E, SC155, SC166, and SC425 evaluated in Texas exhibited head smut resistance to pathotypes 1 to 4 [25].…”

“…Sorghum mono-cropping, planting susceptible hybrids, and the appearance of new virulent pathotypes in the United States (Table 1), China, and other sorghum growing regions have increased the incidence of head smut [3] [4] [6] [7] [8] [9] [10] [11]. In the 1990s, a head smut epiphytotic in China covered about 58 thousand hectares with an average incidence ranging from 18 to over 80% [4] [12].…”

Understanding Genetic Control of Biotic Stress Resistance in Sorghum for Applied Breeding

“…Dodman and Obst (1985) reported race 3 of S. reilianum in Southeast Queensland, Australia. Recently, Zhang et al (2011) documented that there are four races found in the sorghum fi elds in China.…”

“…Several good sources of resistance to head smut have been identifi ed and characterized (Peterson et al 2009;Zhang et al 2011). Some resistance sources have been utilized in various sorghum breeding programs (Rooney et al 2002;Zhang et al 2011).…”

“…Several good sources of resistance to head smut have been identifi ed and characterized (Peterson et al 2009;Zhang et al 2011). Some resistance sources have been utilized in various sorghum breeding programs (Rooney et al 2002;Zhang et al 2011). Inheritance of resistance to head smut is variable, depending upon the source of resistance, the race of pathogen (i.e., race-specifi c reaction), and the environment where host-pathogen reaction is evaluated (Cao et al 1988;Magill et al 1996).…”