Novel Tetraploid Triticale (Einkorn Wheat × Rye)-A Source of Stem Rust Resistance

Abstract

Among cereals, triticale (×Trititcoseale Wittmack ex A. Camus) represents a number of advantages such as high grain yield even in marginal environments, tolerance to drought, cold and acid soils, as well as lower production costs. Together with high biomass of grain and straw, triticale is also considered as an industrial energy crop. As an artificial hybrid, it has not evolved naturally, which is reflected in narrow genetic diversity causing a resistance collapse in recent years. Here, we describe a novel, synthetic tetraploid triticale, which was developed by the crossing of rye (Secale cereale L.) with einkorn wheat (Triticum monococcum spp. monococcum), which possess Sr35 stem rust resistance gene. Three subsequent generations of alloploids were obtained by chromosome doubling followed by self-pollination. The cytogenetic analyses revealed that the amphiploids possess a set of 28 chromosomes (14 of Am-genome and 14 of R-genome). The values of the most important yield-shaping traits for these tetraploid triticale form, including thousand-grain weight, plant height and stem length were higher compared to parental genotypes, as well as standard hexaploid triticale cultivars. This study shows that this tetraploid triticale genetic stock can be an interesting pre-breeding germplasm for triticale improvement or can be developed as a new alternative crop.

Keywords: einkorn; fluorescence in situ hybridization; genetic diversity; resistance genes; steam rust; triticale.

Figure 1

PCR products for NL9F5 marker linked to Sr35 stem rust resistance gene. 1–24—T. monococcum genotypes (Table 1). 25 and 26—positive controls (GSTR 526 and PI 428170). An arrow indicates a 719 bp product linked to resistance allele.

Figure 2

Karyotypes of (a) T. monococcum PI 191383 accession and (b) rye cv. Hadron. Yellow FISH signals are from probe pTa-86, red signals—pTa-535 and green signals are from probe pTa-713.

Figure 3

Chromosome sets analysed by genomic in situ hybridization (GISH) and fluorescent in situ hybridization (FISH) for (a) dihaploid plant (S₁ generation) and (b) double haploid plant (S₂ generation). A-genome chromosomes were labelled using digoxigenin-11-dUTP (green) and R-genome chromosomes were labelled with tetra-methyl 5dUTP-rhodamine (red). (c) FISH pattern of pTa86 (green) and pTa535 (red) probes on chromosomes of double haploid plant (S₂ generation). Scale bar: 10 µm.

Figure 4

Chromosomes of tetraploid triticale at metaphase I of meiosis of pollen mother cells (PMCs) originated from (a) S₂ generation plant; and (b) S₃ generation plant. A-genome chromosomes were labelled using digoxigenin-11-dUTP (green) and R-genome chromosomes were labelled with tetra-methyl 5dUTP- rhodamine (red). Scale bars = 5 µm.

Figure 5

Infection scores collected from three experimental trials. Each trial consisted of 1–20 S₄ and following control genotypes: T. aestivum “Thatcher”, (susceptible control, Sus1–Sus10) and T. aestivum Thatcher + Sr57 (moderate resistant control, Mod1—Mod10). Infection types (ITs) were scored according to Stakman et al. (1962): “0”, “1”, “2”—resistant; “3” to “4”—susceptible.

Figure 6

Graphical comparison of the mean and range scores for the following 8 yield-related traits investigated among Triticum monococcum (PI 191383), Secale cereale (Dankowskie Hadron) and tetraploid triticale (amphiploids—S₄ generation): plant height (PHt), stem length (StL), spike length (SpL), number of spikelets per spike (SplPS), number of grains per spike (GPS), grain length (GL), grain width (GW) and thousand-grain weight (TGW).

Figure 7

Spike (a) and whole plants (b) of S₄ generation of tetraploid triticale. Seeds of: (c) Triticum monococcum (PI 191383), (d) Secale cereale (Dankowskie Hadron) and (e) tetraploid triticale (S₄ generation). Scale bars: 1 cm.