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Doctoral thesis, 2002

Broadening of mildew resistance in wheat

Forsström, Per-Olov

Abstract

Poudery mildew (Blumeria graminis f. sp. tritici) is a prevalent foliar disease in maritime and semicontinental climates and occurs wherever wheat is grown. The pathogen is an obligate fungus that seldom kills its host and winters at the asexual stage. Mildew-resistant lines was selected from a broad material derived from crosses between mildew-susceptible bread wheats and mildew-resistant: (1) triticale, (2) a double disomic wheat-rye substitution line, and (3) a wheat-Leymus mollis amphidiploid (containing 12 chromosomes from L. mollis). Mildew tests were conducted on later generations (BC1F4 or F5) in order to increase the isolation of resistant lines under homozygous conditions. The choice of parents influenced the results and a large-sized population was a prerequisite in order to succeed in exploiting the full potential of these interspecific crosses. A combined approach of a mildew test and cytogenetics was used to obtain lines with transferred rye chromatin from a double disomic wheat-rye substitution line. The material showed a fairly high rate of translocations derived from misdivision and centric fusions, i.e. lines that are suitable for plant breeding. The most prominent result was the isolation of a Robertsonian translocation, 2BS.2RL. Molecular cytogenetics was used to characterise mildew-resistant lines that contained the rye chromosomes 1R | 2R, 1R | 4R, 1R | 6R, 1R and an inversion of 1R, all derived from triticale x wheat crosses. C-banding was used to identify the aberrant chromosome 1R and molecular cytogenetics was required to describe the chromosome as a pericentric inversion. The inverted 1R was characterised with five different repetitive probes using FISH and the breakpoints were localised between (1) the 5S rDNA and the NOR region on the satellite of the short arm, and (2) between hvo ACC(5) sites close to the centromere of the long arm. We developed a strategy for converting a wheat RFLP-based assay into a PCR-based sequence-tagged site (STS). Two RFLP-loci located on 2L were chosen and STS markers were obtained for the three wheat genomes A, B, D and the rye genome R. The PCR markers can be used for marker-assisted selection (MAS) in the selection of mildew-resistant translocation 2BS.2RL.

Keywords

wheat; rye; triticale; wheat-rye hybrids; wheat-rye introgressions; chromosomal substitution; pericentric inversion; Leymus mollis hybrids; powdery mildew (Blumeria graminis f. sp. tritici); resistance breeding; C-banding; molecular cytogenetics; physical chromosome mapping; GISH; FISH; molecular markers; RFLP; SSCP; STS; MAS

Published in

Acta Universitatis Agriculturae Sueciae. Agraria
2002, number: 336
ISBN: 91-576-6182-0
Publisher: Swedish University of Agricultural Sciences

Authors' information

Forsström, Per-Olov
Swedish University of Agricultural Sciences, Department of Crop Science

UKÄ Subject classification

Agricultural Science

URI (permanent link to this page)

https://res.slu.se/id/publ/107405