Near‐Isogenic Barley Lines with Genes for Resistance to Powdery Mildew¹

Abstract

Near‐isogenic lines differing in resistance genes were developed to study the effects of genes in barley (Hordeum vulgare L.) giving specific resistance to powdery mildew (Erysiphe graminis DC f.sp. hordei Em. Marchal). This paper describes breeding techniques, degree of similarity between isolines, and resistance genes present in the isolines. Twenty‐four donors of resistance genes were crossed and backcrossed five times to the spring barley cv. ‘Pallas’, and homozygous resistant BC5F2 plants were selected. Resistant lines were evaluated and selected for phenotypic similarity with the recurrent parent in the BC5F3, through BC5F7 generations. To select for genetic similarity in the region of the resistance locus Ml‐a, two linked hordein loci, Horl and Hor2, were studied in the BC5F4 generation. The resulting 24 near‐isogenic lines originated from single BC5Fs4 plants in each of 24 different progenies. With a few exceptions, the near‐isogenic lines were similar to the recurrent parent in morphological and physiological characteristics. Tests with the hordein genes indicated that double crossing‐over occurred very close to the resistance locus Ml‐a in five of the isogenic lines. With 22 powdery mildew isolates, 22 lines were similar to their donors in resistance reaction, while two lines gave reactions that indicated that they have lost a second resistance gene. The 24 near‐isogenic lines comprised 14 lines with one resistance gene each, and 10 lines with two or more resistance genes. All the isogenic lines differ in resistance. The degree of genetic similarity between the 24 isogenic lines and the recurrent parent Pallas is high according to the morphological and physiological observations and may be even higher than theoretically expected in lines with double recombination in the region of locus Ml‐a. These near‐isogenic barley lines are recommended for both practical and theoretical research work in the barley‐powdery mildew system.

Functional analysis of barley RAC/ROP G‐protein family members in susceptibility to the powdery mildew fungus

“…Their generation was described previously by Kùlster et al (1986). The mutant mlo5 ror1-2 was obtained from Paul Schulze-Lefert (Max-Planck-Institute for plant breeding research, Cologne, Germany).…”

Selections from barley landrace collected in Libya as new sources of effective resistance to powdery mildew (Blumeria graminis f.sp. hordei)

“…It was purified by single colony isolation and was maintained and propagated on young seedlings of the powdery mildew susceptible cultivar Manchuria (CI 2330). The virulence spectrum of this isolate was determined based on observation of its infection types on the Pallas isoline differential set (Kølster et al 1986), provided kindly by Dr. L. Munk (Royal Agricultural and Veterinary University, Copenhagen, Denmark). This isolate was chosen for this experiment because it was the most avirulent isolate available.…”

Assessment of powdery mildew resistance in wild barley (Hordeum spontaneum L.) populations in the aegean region of Turkey

“…Pallas near isogenic lines of barley (Koelster et al 1986) and other lines from Ris0 National Laboratory, Denmark, were used as a differential set for comparison with the résistance reaction of the wild barleys. In addition, we included 14 lines with résistance derived from H. spontaneum collected in Israël (Jahoor and Fischbeck 1987b).…”