Effectiveness of Twenty‐Four Barley Resistance Genes Against Powdery Mildew (Erysiphe graminis DC f. sp. hordei Em. Marchal) in Spain

Abstract

Twenty-four near-isogenic barley lines, with a cv. 'Pallas' background, carrying different mildew resistance genes were subjected in 1987,1989 and 1990 to natural infection by the pathogen at several different and contrasting Spanish sites in order to study its virulence. The virulence genes proved to be geographically grouped into three regions: western (Valladolid), southern (Sevilla) and northern and northeastern (Navarra, Lleida and Girona). The mildew population of Lleida was more variable when compared with Navarra and Valladolid. Overall, the most effective resistance genes were: Ml-al3 -\-Ml-(Ru3), mlo and Ml-(1402).

Virulence spectrum in populations of the barley powdery mildew pathogen, Erysiphe graminis f. sp. hordei in Tunisia and Morocco in 1992

“…Corresponding patterns have also been described from southern Spain (Molina-Cano et al, 1992). Since no geographical barriers exist between the areas, it is quite possible that populations on both sides of the Mediterranean sea influence each other.…”

“…Virulence compositions of powdery mildew populations from the northern Mediterranean area are known to differ considerably from those described for large parts of Europe (Limpert et al, 1990;Molina-Cano et al, 1992). Phenomena contributing to evolution patterns of the pathogen in Europe have been discussed by Limpert et al (1990) and Wolfe & McDermott (1994).…”

“…Some information is also available on virulence patterns of the fungus from the northern Mediterranean regions (Limpert et al, 1990;Molina-Cano et al, 1992. Little is known about virulence patterns of mildew from North Africa (Caddel, 1976).…”

Mildew-resistant mutants induced in North American two- and six-rowed malting barley cultivars

“…Both F 1 s and F 2 s were tested for resistance to powdery mildew by exposure in the greenhouse to a composite powdery mildew population from the Lleida region (Molina- Cano et al 1992), using the genotype SM4142, which does not carry any resistance gene (G. Fischbeck, personal communication), as a spreader. The URS2 mutant was test-crossed to Alexis (mlo) and Rupal (Mla13) ( Table 3).…”

“…This developed when the plantlets had two unfolded leaves, covering almost all their foliar area. The mixture of isolates used was known to be virulent on all known resistance genes except Ml-a, Ml-(1402) and mlo (Molina- Cano et al 1992). Putative mutants were selected that showed an almost complete absence of mildew colonies, and these plants were reared until maturity.…”