Interaction of Genes Determining the Spike Shape of Wheat and Those Located in the 5AL Chromosome

Abstract—The spike parameters of hexaploid wheats from the genus Triticum L. are determined by the major genes and play an important role in systematics. Having a strong pleiotropic effect, they also have practical importance. In this work, the interaction of the dominant genes Q^S and Q with the dominant gene C¹⁷⁶⁴⁸ determining the shape of the spike was investigated. The gene Q is located in the 5AL chromosome and determines the formation of the elongated lax spike in the T. spelta L. species. The homoeoallelic gene Q^S introgressed into bread wheat from Aegilops speltoides Tausch. and causing the formation of the speltoid spike is also located in the 5AL chromosome of the 84/98^w line. The C¹⁷⁶⁴⁸ gene is analogous in the phenotypic manifestation to the C gene determining the formation of a dense short spike on a short culm as in T. compactum Host. It was mapped to the 5AL chromosome in the bread wheat line ANBW-5A and the donor of the gene was a mutant of durum wheat. In the present work, the spike length, spikelet number, index of spike density, and stem length were studied in F₁, F₂, and F₃ of three different hybrid populations. It was shown for the first time that the C¹⁷⁶⁴⁸ gene is epistatic to the dominant genes Q^S and Q. It was manifested in the formation of compact spikes in F₁ hybrids and in the numerical predominance of plants with a compact spike in F₂. At the same time, the gene C¹⁷⁶⁴⁸ showed a smaller effect on stem length and did not affect the number of spikelets. Using the genetic analysis, it was found that genes Q^S and Q are independently inherited from gene C¹⁷⁶⁴⁸, although a strong link was observed between the Q^S or Q and b1 gene.