BGN 19: New genes for powdery mildew resistance in Hordeum spontaneum derived lines allelic or closely linked to the M1-2 locus

New genes for powdery mildew resistance in Hordeum spontaneum derived lines allelic or closely linked to the Ml-p locus

A. Jahoor, A. Ludwig, and G. Fischbeck
Lehrstuhl für Pflanzenbau und
Planzenzüchtung der Technischen Universität München
D-8050 Freising-Weihenstephan, F.R. Germany


Wild grown populations of Hordeum spontaneum in Israel represent a large gene pool for disease resistance. This assumption has been repeatedly confirmed by different authors (Fischbeck et al., 1976; Wahl et al., 1978; Moseman et al., 1983; Giles and von Bothmer, 1985; Jahoor and Fischbeck, 1987a, 1987b, 1987c). Jahoor and Fischbeck (1987b) reported that many resistance genes for powdery mildew of H. spontaneum derived lines do not belong to the Ml-a locus. They also aetermined the presence of Ml-p resistance in the H. spontaneum derived line Diamant /7B-5A. Schaller and Briggs (1955) located the Ml-p locus on the short arm of chromosome 5 which has been confirmed by several other authors including Jensen and Jergensen (1975). In 1985 Jensen mentioned unpublished data which indicate that Ml-p is not located on chromosome 5, but did not publish fürther details. Our results (Jahoor and Fischbeck, 1987) showed again linkage between Ml-a and Ml-p on chromsome 5.

Table 1. F2 segregation for powdery mildew reaction in testcrosses between H. spontaneum lines and cv. Roland and isogenic line P 19.*

Table 2.Mildew reaction of cv. Psaknon and two H. spontaneum derived lines possessing new Ml-p genes for mildew resistance.

From earlier studies (Fischbeck, 1981), it is known that virulence against Ml-p resistance is present in the mildew population spread on wild grown H. spontaneum stands in Israel.

Two H. spontaneum derived lines were crossed with 'Roland' (susceptiEle reaction against mildew cultures MC-IS-2 and 184-21) as well as with the isogenic line P 19 which carries the Ml-p mildew resistance gene. The crosses RS 145/Aramir B//Roland and RS 170-35 /Aramir B//Roland segregated into a 3:1 ratio indicating the presence of a dominant gene for powdery mildew resistance in both H. spontaneum derived lines (Table 1). Testcrosses with line P 19 were used to test allelism with the Ml-p locus. Since no segregation occurred in these crosses, the conclusion seems justified that the genes of both H. spontaneum derived lines are allelic to or closely linked with the Ml-p locus.

The reaction pattern of RS 145-1/Aramir B and RS 170-35/Aramir B with 7 mildew cultures are given in Table 2. The isolates MC-IS-2 and PS-IS-2 collected from wild grown populations of H. spontaneum in Israel clearly distinguish the reaction of line RS 145-17Aramir B from Psaknon. Upon infection with the European mildew culture 201/107, line RS 170-35/Aramir B reacted as moderately susceptible whereas Psaknon showed a clearly distinguishable I-II type of reaction. Less noticeable differences were also observed in the reactions against cultures 184-2 and AI-1.

On the account of these results, it is concluded that the resistance genes present in the two H. spontaneum derived lines are different from the resistance gene of the cv. Psaknon (Ml-p) to which they are either allelic or closely linked. Estimates of the 95% upper confidence limit of recombination resulted in values < 0.095% for line RS 145-1/Aramir B and < 0.067% for line RS 170-35/Aramir B (Table 1). Therefore it is suggested that the genes present in line RS 145-1/ Aramir B and line RS 170-35/Aramir B should be designated Ml-p2 and Ml-p3, respectively.

Acknowledgement:

Thanks are due Ms. C. Stockenreiter for technical assistance in this research.

References:

Fischbeck, G. 1981. Ergebnisse von Untersuchungen uber Krank- heitsresistenz in israelischen Populationen von Hordeum spontaneum im Hinblock auf Gegenwartsprobleme der Resistenzzuchtung. Tagungsbericht der "Arbeitsgemeinschaft der Saatzuchtleiter". Gumpenstein 32:3-13.

Fischbeck, G., E. Schwarzbach, Z. Sobel, and I. Wahl. 1976. Mehltauresistenz aus israelischen Populationen der zweizeiligen Wildgerste (Hordeum spontaneum).Z. Pflanzenzuchtg. 76:163-166.

Giles, B.E., and R. von Bothmer. 1985. The progenitor of barley (Hordeum vulgare ssp. spontaneum) - its importance as a gene resource. Sveriges utsadesforenings Tidskrift 95:53-61.

Jahoor, A., and G. Fischbeck. 1987a. Genetical studies of resistance of powdery mildew in barley lines derived from Hordeum spontaneum collected from Israel. Plant Breeding 99:265-273.

Jahoor., A, and G. Fischbeck. 1987b. Sources of resistance to powdery mildew in barley lines derived from Hordeum spontaneum collected in Israel. Plant Breeding 99:274-281.

Jahoor, A., and G. Fischbeck. 1987c. Identification of new genes for the powdery mildew resistance on the Ml-a locus collected in Israel. BGN 17:94-98.

Jensen, J., and J.H. Jørgensen. 1975. The barley chromosome 5 linkage map. II. Extention of the map with four loci. Hereditas 8:17-26.

Jensen, J. 1985. Coordinator's report. Chromosome 5. BGN 15:74-77.

Kolster, P., L. Munk, 0. Stolen, and J. Loh. 1986. Near-isogenic barley lines with genes for resistance to powdery mildew. Crop Sci. 26:903-907.

Moseman, J.G., E. Nevo, and D. Zohary. 1983. Resistance of Hordeum spontaneum collected in Israel to infection with Erysiphe graminis hordei. Crop Sci. 23:1115-1119.

Schaller, C.W., and F.N. Briggs. 1955. Inheritance of resistance to mildew, Erysiphe graminis hordei, in the barley variety, Black Russian. Genetics 40:421-428.

Wahl, I., N. Esched, A. Segal, and Z. Sobel. 1978. Significance of wild relatives of small grains and other wild grasses. In D.M. Spencer (ed.) The powdery mildew. Academic Press Longdon. pp. 83-100.


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