Diversified Chromosome Rearrangements Detected in a Wheat‒ Dasypyrum breviaristatum Substitution Line Induced by Gamma-Ray Irradiation

Abstract

To determine the composition of chromosome aberrations in a wheat‒Dasypyrum breviaristatum substitution line with seeds treated by a dose of gamma-rays (200 Gy), sequential non-denaturing fluorescence in situ hybridization (ND-FISH) with multiple oligonucleotide probes was used to screen individual plants of the mutagenized progenies. We identified 122 types of chromosome rearrangements, including centromeric, telomeric, and intercalary chromosome translocations from a total of 772 M1 and 872 M2 plants. The frequency of reciprocal translocations between B- and D-chromosomes was higher than that between A- and D-chromosomes. Eight translocations between D. breviaristatum and wheat chromosomes were also detected. The 13 stable plants with multiple chromosome translocations displayed novel agronomic traits. The newly developed materials will enhance wheat breeding programs through wheat‒Dasypyrum introgression and also facilitate future studies on the genetic and epigenetic effects of translocations in wheat genomics.

Keywords: chromosome rearrangement; fluorescence in situ hybridization; gamma ray radiation; wheat‒Dasypyrum substitution.

Figure 1

The sequential ND-FISH patterns of wheat‒D. breviaristatum substitution lines D11-5 (2V^b/2D) and D2230 (2V^b-1/2D) with multiple probes. The probes Oligo-B11 (green) + Oligo-pDb12H (red) (a,d), Oligo-pSc119.2 (green) + Oligo-pTa535 (red) (b,e,h), Oligo-k566 (red) + Oligo-713 (green) (c,f), Oligo-k288 (green) + Oligo-D (red) (g) were presented, respectively. Arrows indicated the D. breviaristatum chromosomes. The karyotypes of D. breviaristatum chromosomes 2V^b and 2V^b-1 are shown (i). Bars represent 10 μm.

Figure 2

ND-FISH detection of chromosomal structure aberrations in M0 generation with Oligo-pSc119.2 (green) and Oligo-pTa535 (red). Six representative plants, 16-W289 (a), 16-W320 (b), 16-W695 (c), 16-W462 (d), 16-W777 (e), and 16-W473 (f), were selected for displaying huge structural aberrations in root tip metaphase chromosomes. The arrows indicate abnormal chromosomes. The karyotypes of deleted, dicentric, and translocated chromosomes are shown (g).

Figure 3

The profile of 112 interchromosomal translocation events among A-, B- and D-genome chromosomes by ND-FISH with Oligo-pSc119.2 and Oligo-pTa535 probes. (a) Yellow lines indicated the translocations occurred in the same genome; blue lines showed the rearrangements happened between A-genome and B-genome; the translocations occurred between B-genome and D-genome are marked with red lines; green lines show the translocations between A-genome and D-genome. (b) The number of interchromosomal translocation events in six different combinations was calculated. (c) Several chromosomal rearrangements, including 22 Robertsonian translocations and 12 small-segment translocations, are shown.

Figure 4

Sequential ND-FISH analysis of the metaphase chromosomes of wheat‒wheat translocation lines. T1BS.1BL-4DL and T4DS.4DL-1BL translocation (a,b) and T1DS.1DL-5BS and T1DL-5BS.5BL translocation (d,e) with the probes Oligo-k288 (green) and Oligo-D (red), Oligo-pSc119.2 (green), and Oligo-pTa535 (red); the A line included two non-Robertsonian translocation events involving 5B, 4D, 6D, and 7B, that were analyzed using Oligo-pSc119.2 (green), Oligo-pTa535 (red), Oligo-713 (green), and Oligo-18 (red) as probes (g,h). Images show enlargements of the FISH pattern of chromosomes with structural changes (c,f,i). Arrows and black lines indicate the breakage points.

Figure 5

Summary of the irradiation-induced chromosome translocations that occurred between wheat chromosomes and D. breviaristatum chromosomes. The translocation T2V^b:6B was confirmed using the probes Oligo-k288 (green) and Oligo-D (red) (a), the combination of the three probes Oligo-pDb12H (green), Oligo-B11 (green), and Oligo-k288 (red) (d), and Oligo-pSc119.2 (green) + Oligo-pTa535 (red) (b,e) by sequential ND-FISH analysis. Two translocation chromosomes, T2V^bS.2V^bL-6BS and T2V^bL-6BS.6BL, showed the breakpoint closed to the centromere (c,f). Karyotype of wheat‒D. breviaristatum 2V^b translocation lines T2V^b-1:2B and T2V^b:5A (g,h). Seven types wheat‒D. breviaristatum 2V^b translocation chromosomes were compared to the corresponding normal chromosomes below them (i,j). White arrows indicate the translocation chromosomes T2V^b:6B.