Prospects for Exploitation of Disease Resistance from Hordeum Chilense in Cultivated Cereals

Abstract

Hordeum chilense is a South American wild barley with high potential for cereal breeding given its high crossability with other members of the Triticeae. In the present paper we consider the resistance of H. chilense to several fungal diseases and the prospects for its transference to cultivated cereals.All H. chilense accessions studied are resistant to the barley, wheat and rye brown rusts, the powdery mildews of wheat, barley, rye and oat, to Septoria leaf blotch, common bunt and to loose smuts, which suggests that H. chilense is a non-host of these diseases. There are also lines resistant to wheat and barley yellow rust, stem rust and to Agropyron leaf rust, as well as lines giving moderate levels of resistance to Septoria glume blotch, tan spot and Fusarium head blight. Some H. chilense lines display pre-appressorial avoidance to brown rust. Lines differ in the degree of haustorium formation by rust and mildew fungi they permit, and in the degree to which a hypersensitive response occurs after haustoria are formed.Unfortunately, resistance of H. chilense to rust fungi is not expressed in tritordeum hybrids, nor in chromosome addition lines in wheat. In tritordeum, H. chilense contributes quantitative resistance to wheat powdery mildew, tan spot and loose smut. The resistance to mildew, expressed as a reduced disease sekrity, is not associated with macroscopically visible necrosis. Hexaploid tritordeums are immune to Septoria leaf blotch and to common bunt although resistance to both is slightly diluted in octoploid tritordeums. Studies with addition lines in wheat indicate that the resistance of H . chilense to powdery mildew, Septoria leaf blotch and common bunt is of broad genetic basis, conferred by genes present on various chromosomes.

Resistance of Hordeum chilense against loose smuts of wheat and barley (Ustilago tritici and U. nuda) and its expression in amphiploids with wheat

“…Hordeum chilense was also found to be resistant to the barley, wheat and rye brown rusts, the powdery mildews of wheat, barley, rye and oat and to Septoria leaf blotch suggesting that H. chilense is a non-host of these pathogens (Rubiales et al 1991(Rubiales et al , 1992(Rubiales et al , 1993a(Rubiales et al , 1993b. There are also lines resistant to wheat and barley yellow rust, stem rust and to Agropyron leaf rust, as well as lines giving moderate levels of resistance to Septoria glume blotch, tan spot and Fusarium head blight (Rubiales et al 1991(Rubiales et al , 2001. Hordeum chilense chromosome addition and substitution lines in durum and bread wheat and wheat -H. chilense translocations have been obtained and the feasibility of transferring traits from H. chilense to cereals is previously discussed (Martı´n et al , 2000.…”

“…Hordeum chilense was also found to be resistant to the barley, wheat and rye brown rusts, the powdery mildews of wheat, barley, rye and oat and to Septoria leaf blotch suggesting that H. chilense is a non‐host of these pathogens (Rubiales et al 1991, 1992, 1993a, 1993b). There are also lines resistant to wheat and barley yellow rust, stem rust and to Agropyron leaf rust, as well as lines giving moderate levels of resistance to Septoria glume blotch, tan spot and Fusarium head blight (Rubiales et al. 1991, 2001).…”

“…In contrast, fertile amphiploids with wheat were easily produced using H. chilense. Among several approaches for its use in cereal breeding are the development of hybrids and amphiploids with wheat to be used as a possible new crop or as bridges to transfer useful genes to cultivated cereals (Martı´n et al 2000, Rubiales et al 2001. The purpose of the present experiments was to determine the level of resistance of H. chilense accessions to loose smuts, and its expression in amphiploids with wheat.…”

“…Among several approaches for its use in cereal breeding are the development of hybrids and amphiploids with wheat to be used as a possible new crop or as bridges to transfer useful genes to cultivated cereals (Martín et al. 2000, Rubiales et al. 2001).…”

Powdery mildew susceptibility and biotrophic infection strategies

“…Quantitative resistance of mildew host plant genotypes is often observed as a slow‐disease phenotype or mild disease severity without leaf necrosis e.g. [61]. The factors restricting fungal development in these cases are largely unknown, and corresponding quantitative trait loci have not been isolated yet.…”