Chromosome pairing in durum wheat haploids with and without ph1b of bread wheat

Abstract

Durum or macaroni wheat (Triticum turgidum L., 2n = 4x = 28; AABB) is an allotetraploid with two related genomes, AA and BB, each with seven pairs of homologous chromosomes. Although the corresponding chromosomes of the two genomes are potentially capable of pairing with one another, the Ph1 (Pairing homoeologous) gene in the long arm of chromosome 5B permits pairing only between homologous partners. As a result of this Ph1-exercised disciplinary control, durum wheat and its successor, bread wheat (Triticum aestivum L., 2n = 6x = 42; AABBDD) show diploid-like chromosome pairing and hence disomic inheritance. The Ph mutants in the form of deletions are available in bread wheat (ph1b) and durum wheat (ph1c). Thus, ph1b-haploids of bread wheat and ph1c-haploids of durum wheat show extensive homoeologous pairing that has been shown by us and several others. Here we study the effect of ph1b allele of bread wheat on chromosome pairing in durum haploids, whereas we studied earlier the effect of ph1c allele in durum haploids that we synthesized. In durum wheat, the ph1b-haploids show much higher (49.4% of complement) pairing than the ph1c-haploids (38.6% of complement).