Development and validation of a PCR-based marker assay for negative selection of the HMW glutenin allele Glu-B1-1d (Bx-6) in wheat

Polymorphisms between the coding sequences of high-molecular-weight (HMW) glutenin x-type genes at the Glu-1 locus were used to amplify Glu-1B x-type-specific PCR fragments. PCR analysis in a wheat cultivar subset carrying different Glu-1B x-type alleles resulted in PCR fragments that differed in size for Glu-B1-1d (B-x6) and non -Glu-B1-1d (B-x6) genotypes. Subsequent sequencing analysis revealed a 15-bp in-frame insertion in the coding regions of all Glu-B1-1d (B-x6) genotypes which allowed the development of a B-x6-specific PCR assay for high-throughput allele sizing by ion-pair reversed-phase high-performance liquid chromatography. The assay was validated in a set of 86 German wheat cultivars, and genotyping data unequivocally verified the presence of HMW glutenin subunits GLU-B1-1D (Bx-6) + GLU-B1-2A (By-8) by means of sodium dodecyl sulphate-polyacrylamide gel electrophoresis. These results demonstrate that the PCR assay can be applied for the detection and negative selection of the 'poor breadmaking quality' Glu-B1-1d (B-x6) alleles in wheat breeding programs.

Identification and quantitative expression analysis of genes that are differentially expressed during conidial germination in Pyrenophora teres

Net blotch, caused by Pyrenophora teres, is a common disease of barley ( Hordeum vulgareL.). Two PCR-based differential screening techniques, cDNA-amplified fragment length polymorphism (cDNA-AFLP) and suppression subtractive hybridisation (SSH), were employed to clone cDNA copies of transcripts that are up-regulated during conidial germination. The nucleotide sequences of 35 transcripts were analysed, and the amino acid sequences of their predicted products were compared with entries in databases. Eleven of these clones showed homology to genes from other ascomycetes coding for a transcription factor, two regulatory proteins, a putative transposase, a protein required for the biogenesis of cytochrome C oxidase, a threonine synthase, a probable subunit of a phenylalanine-tRNA synthetase, a subunit of RNA polymerase I, a cation transport protein, a vacuolar ATP synthase subunit, and an RNA processing protein. One conserved hypothetical protein was found and 23 sequences could not be functionally classified. The relative expression of five transcripts at 0, 1, 2, 3, 6, 12 and 24 h after induction of germination was determined by real-time RT-PCR using 18S rRNA as the endogenous reference sequence. All transcripts showed a significant increase in expression during early stages of germination. The maximum change in expression relative to ungerminated conidia ranged between 2.6- and 6-fold. The characterisation of genes involved in biochemical processes during the germination of conidia could be useful for target-specific development of new antifungal agents.