Isolation of the dwarfing Rht-B1p (Rht17) gene from wheat and the development of an allele-specific PCR marker

Abstract

Plant height is one of the most important traits of wheat because it influences lodging resistance, harvest index and yield. Reduced height of wheat is achieved mainly by the introduction of Rht-B1b (Rht1), Rht-B1e (Rht11) or Rht-D1b (Rht2) dwarfing genes, which produce mutant DELLA proteins that constitutively restrain plant growth irrespective of gibberellin hormone level. The exploration of new variations of these genes is necessary for plant breeding purposes. A set of alleles with various degrees of height reduction may be useful for optimization of wheat plant height in different environments. Also, new alleles may give different pleiotropic effects on other important traits, as leaf area, coleoptile length, disease resistance and preharvest sprouting tolerance. In the present work, we discovered a new allelic variation at the Rht-B1 locus in the ‘Chris Mutant’ bread wheat line that carries the Rht17 gene. The Rht-B1 gene from the Chris Mutant line was cloned and sequenced. The alignment showed an C-to-T substitution at a position 178 nucleotides from the start codon that created a stop codon in the DELLA domain. We designated the new allele as Rht-B1p and developed a diagnostic PCR marker for its identification. As a result of crossing and segregation analysis, we showed that Rht-B1p reduced plant height by approximately 30 and 50 % in bread wheat and durum wheat, respectively, under greenhouse conditions. We concluded that Rht-B1p was identical to the earlier identified gene Rht17.