Identification of P genome chromosomes in Agropyron cristatum and wheat-A. cristatum derivative lines by FISH

Abstract

Agropyron cristatum (L.) Gaertn. (P genome) is cultivated as pasture fodder and can provide many desirable genes for wheat improvement. With the development of genomics and fluorescence in situ hybridization (FISH) technology, probes for identifying plant chromosomes were also developed. However, there are few reports on A. cristatum chromosomes. Here, FISH with the repeated sequences pAcTRT1 and pAcpCR2 enabled the identification of all diploid A. cristatum chromosomes. An integrated idiogram of A. cristatum chromosomes was constructed based on the FISH patterns of five diploid A. cristatum individuals. Structural polymorphisms of homologous chromosomes were observed not only among different individuals but also within individuals. Moreover, seventeen wheat-A. cristatum introgression lines containing different P genome chromosomes were identified with pAcTRT1 and pAcpCR2 probes. The arrangement of chromosomes in diploid A. cristatum was determined by identifying correspondence between the P chromosomes in these genetically identified introgression lines and diploid A. cristatum chromosomes. The two probes were also effective for discriminating all chromosomes of tetraploid A. cristatum, and the differences between two tetraploid A. cristatum accessions were similar to the polymorphisms among individuals of diploid A. cristatum. Collectively, the results provide an effective means for chromosome identification and phylogenetic studies of P genome chromosomes.

Figure 1

Comparison of P genome chromosomes on the basis of FISH patterns from two individual plants of diploid A. cristatum Z1842. The green signals represent the probe pAcTRT1, and the red signals represent the probe pAcpCR2.

Figure 2

Integrated idiogram of A. cristatum chromosomes showing the locations of the pAcTRT1 and pAcpCR2 bands. The green signals represent the probe pAcTRT1, and the red signals represent the probe pAcpCR2. The colour gradient on the right shows the frequency of pAcTRT1 signals from five specimens of A. cristatum.

Figure 3

Classification of added chromosomes in fourteen wheat-A. cristatum addition lines identified by pAcTRT1 (a) and pAcpCR2 (b) and the corresponding chromosomes in diploid A. cristatum (c).

Figure 4

FISH patterns of wheat-A. cristatum derivative lines II-3-1 (a), II-23-1 (b) and II-11-1 (c) with multiple P genome chromosomes using pAcTRT1 and pAcpCR2 as probes and the corresponding chromosomes in diploid A. cristatum (d).

Figure 5

FISH performed on mitotic chromosomes of diploid A. cristatum Z1842 with probes for pAcTRT1, pAcpCR2, 45S rDNA, rye tandem pSc200 and pAs1.

Figure 6

FISH patterns of the two tetraploid A. cristatum accessions Z559 (a) and Z589 (b) and a comparison of FISH patterns of these accessions (c). The green signals represent the probe pAcTRT1, and the red signals represent the probe pAcpCR2.