Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 20, 2011
Publication Date: May 16, 2012
Citation: Goodwin, S.B. 2012. Resistance in wheat to Septoria diseases caused by Mycosphaerella graminicola (Septoria tritici) and Phaeosphaeria (Stagonospora) nodorum. In: Sharma, I, Editor. Disease resistance in wheat, 2012. Wallingford, UK: CABI. p. 151-159. Interpretive Summary: Septoria of wheat is a disease complex caused by three pathogens that are not closely related, but cause similar symptoms so have been grouped together. Historically the disease caused collectively by these pathogens has been called the Septoria complex, which can be divided into Septoria tritici blotch (STB) and Stagonospora leaf and glume blotch. The Septoria complex occurs throughout the world wherever wheat is grown and can cause losses to yield and quality of 50% or more. Breeding for increased resistance is the most economically and ecologically beneficial way to manage the disease. The purpose of this book chapter is to review recent progress on the identification and analysis of resistance, discuss the genetic basis and mapping of resistance in the wheat genome, and indicate sources of resistance and genetically linked molecular markers that can be used to transfer the resistance to new cultivars of wheat through marker-assisted selection. Excellent progress during the past decade has elucidated the genetic basis for resistance to STB and resulted in the identification and publication of 13 major genes for resistance, compared to zero that were known previously. For Stagonospora blotch, we now know that disease is due to dominant genes for toxin sensitivity rather than to resistance per se. Identification and elimination of toxin sensitivity genes from wheat breeding populations can significantly increase the levels of resistance. Use of the toxins to select resistance plants can minimize environmental influence for more rapid and accurate phenotyping. This information can be used by plant pathologists and wheat breeders to increase the level of resistance to the Septoria/Stagonospora disease complex in wheat cultivars of the future.
Technical Abstract: Septoria of wheat is a disease complex caused by three pathogens: Mycosphaerella graminicola (anamorph: Septoria tritici); Phaeosphaeria (anamorph: Stagonospora) nodorum; and P. avenaria f. sp. triticae (anamorph: Stagonospora avenae f. sp. triticae). These pathogens are all in the fungal class Dothideomycetes, but are not closely related; M. graminicola is in the order Capnodiales while P. nodorum and P. avenaria are in the Pleosporales. However, the diseases caused by these pathogens are superficially very similar and they often have been considered together by plant pathologists and breeders. The name for the disease caused by M. graminicola usually is referred to as Septoria tritici blotch (STB) or simply Septoria blotch, while that caused by P. avenaria and P. nodorum is called Stagonospora blotch, reflecting the anamorphs of all three pathogens. In addition to infecting the leaves, S. nodorum can cause severe infection of the heads, or glume blotch. For the purposes of this chapter, Septoria will refer to the complex caused by all three pathogens, STB will mean the disease caused by M. graminicola, and Stagonospora blotch will refer to leaf and glume blotch caused by P. nodorum and P. avenaria. Resistance to Septoria/Stagonospora blotch can be quantitative or qualitative. Mechanisms of resistance and the methods used for its identification have been discussed along with recent progress in resistance breeding. Much progress has occurred during the past ten years, including the identification of toxins produced by P. nodorum that can be used to screen for resistance. Strong resistance to M. graminicola and P. nodorum has been identified and mapped in the wheat genome, and molecular markers now are available for marker-assisted selection in the future.