A PCR‐Based Screening Assay of Ph1, the Chromosome Pairing Regulator Gene of Wheat

Abstract

Ph1 is the principle gene regulating chromosome pairing of wheat (Triticum aestivum L. em Theli.). Ph1 dictates that only the homologous (not homoeologous) chromosomes can pair at MI of meiosis. In the absence of the gene, homoeologous chromosomes may also pair, however. Homoeologous chromosome pairing can be activated by temporarily replacing the normal copy of the gene with its null allele, which is present in the ph1b mutant. One of the main difficulties during these manipulations is the scoring plants for the presence or absence of the Ph1 gene. We developed a polymerase chain reaction (PCR) based screening assay for the Ph1 gene. The probe pHvksu8, which maps in the interstitial deletion of the ph1b mutant encompassing the Ph1 gene, was sequenced and forward and a reverse primers, 20 bp each, were generated. These primers amplified a fragment each for chromosomes 5A, 5B, and 5D. The 5B specific fragment was not amplified in the ph1b mutant, and can be used as a diagnostic fragment to score plants for the presence of Ph1 gene. The reliability of the primers for the Ph1 gene scoring was tested on an F2 population of 40 plants, segregating for the Ph1 gene. No discrepancy was observed between the PCR‐based assay and gel blot DNA hybridization for detection of the fragment associated with the Ph1 gene.