Sources of resistance to septoria tritici blotch and implications for wheat breeding

Abstract

Twenty-four wheat cultivars and breeding lines were screened for isolate-specific resistance to septoria tritici blotch (STB) caused by 12 isolates of Mycosphaerella graminicola. New isolate-specific resistances that could be used in wheat breeding were identified. Major sources of resistance to STB used in world breeding programmes for decades, such as Kavkaz-K4500, Veranopolis, Catbird and TE9111, have several isolate-specific resistances. This suggests that 'pyramiding' several resistance genes in one cultivar may be an effective and durable strategy for breeding for resistance to STB in wheat. Several cultivars, including Arina, Milan and Senat, had high levels of partial resistance to most isolates tested as well as isolatespecific resistances. Resistance to isolate IPO323 was common, present in all but one of the major sources of resistance tested. This suggests that resistance to IPO323 may be an indicator of varietal resistance to STB in the field.

New sources of resistance to Septoria tritici blotch in wheat seedlings

“…Extensive variations in the virulence of the fungus towards different cultivars have been detected during pathogenesis at the seedling stage Chartrain et al 2004;Eyal et al 1985;Kema et al 1996a, b;Simón et al 2005). In Argentina, breeders have classified most commercially-grown cultivars in the range of moderate resistance to susceptibility, suggesting the presence of quantitative, nonspecific resistance in those cultivars, although isolate-specific quantitative resistance may also be present in some cultivars.…”

“…The former typically gives nearly complete resistance that is isolate-specific, and simply inherited, following a gene-for-gene relationship (Brading et al 2002). In contrast, quantitative or partial resistance is incomplete, polygenic (Jlibene et al 1994;Simón and Cordo 1998;Zhang et al 2001), and isolate-nonspecific (Chartrain et al 2004), and often more durable (Simón and Cordo 1998). Although complete resistance is preferential because of the almost total absence of symptoms in the host, a partial resistance is highly relevant owing to the concomitant durability and expression under a broad spectrum of pathogen isolates.…”

“…Although complete resistance is preferential because of the almost total absence of symptoms in the host, a partial resistance is highly relevant owing to the concomitant durability and expression under a broad spectrum of pathogen isolates. Several authors have reported specific interactions between wheat cultivars and particular isolates of Z. tritici (Chartrain et al 2004;Eriksen et al 2003;Kema and Van Silfhout 1997) although quantitative resistance has also been found among different genotypes Chartrain et al 2004;Jlibene et al 1994;Simón et al 2005). Eighteen major resistance genes have been identified in bread wheat (Triticum aestivum L.): Stb1 to Stb15 (McIntosh et al 2008), and Stb16 to Stb18 (McIntosh et al 2012).…”

“…This fecundity increases the risk of adaptation of the pathogen to resistance genes acquired in the host population. The use of fungicides to control STB is expensive as well as not entirely reliable (Chartrain et al 2004) and may lead to the emergence of fungicide-resistant strains. Although the use of fungicides in some situations is unavoidable, resistant cultivars provide an effective, economical, and environmentally friendly approach to the control of STB epidemics (Eyal 1999).…”

“…STB is a major foliar disease of wheat worldwide. Therefore, new sources of resistance along with a more extensive knowledge concerning the genetics of resistance have become necessary in order to improve the breeding for resistance to this disease (Chartrain et al 2004). Z. tritici is a highly genetically diverse pathogen (McDonald et al 1999); moreover, the fungus may reproduce sexually several times during the growing season of wheat (Kema et al 1996c).…”