Identification and genetic analysis of multiple P chromosomes of Agropyron cristatum in the background of common wheat

Abstract

Agropyron cristatum, a wild relative of common wheat (Triticum aestivum L.), provides many desirable genetic resources for wheat improvement, such as tolerance to cold, drought, and disease. To transfer and utilize these desirable genes, in this study, two wheat-A. cristatum derivatives II-13 and II-23 were identified and analyzed. We found that the number of root tip cell chromosomes was 44 in both II-13 and II-23, but there were four and six P genome chromosomes in II-13 and II-23, respectively, based on genomic in situ hybridization (GISH). The chromosome configurations of II-13 and II-23 were both 2n=22II by the meiotic analysis of pollen mother cells (PMCs) at metaphase I, indicating that there were two and three pairs of P chromosomes in II-13 and II-23, respectively. Notably, wheat chromosome 7D was absent in derivative line II-13 while II-23 lacked chromosomes 4B and 7A based on SSR analysis combining fluorescence in situ hybridization (FISH) analysis with pAs1 and pSc119.2 as probes. Chromosomes 2P and 7P were detected in both II-13 and II-23. Another pair of P genome chromosomes in II-23 was determined to be 4P based on expressed-sequences tags-sequence tagged sites (EST-STS) markers specific to A. cristatum and FISH with probes pAcTRT1 and pAcpCR2. Overall, these results suggest that II-13 was a 7P (7D) substitution line with one pair of additional 2P chromosomes and II-23 was a multiple 4P (4B), 7P (7A) substitution line with one pair of additional 2P chromosomes. Moreover, we obtained six alien disomic addition lines and five alien disomic substitution lines by backcrossing. These new materials will allow desirable genes from A. cristatum to be used in common wheat.

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

“…In this study, we found that pAcTRT1 and pAcpCR2 enabled the identification of P genome chromosomes in wheat- A. cristatum derivative lines. The P genome chromosomes identified in the wheat- A. cristatum derivative lines in this study were the same as those in our previous studies 34,38,39 , indicating that the present data are reliable. The arrangement of diploid A. cristatum chromosomes in this study was determined through their correspondence to the P chromosomes in these introgression lines.…”

“…We found that two, three and two different pairs of P genome chromosomes were present in II-3-1, II-23-1 and II-11-1, respectively; these pairs were determined to be 1P and 2P in II-3-1; 2P, 4P and 7P in II-23-1; and 2P and 5P in II-11-1 (Fig. 4) in our previous reports 34,38,39 .

Figure 4FISH 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 ).

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“…II-11-1 was a wheat- A. cristatum 2P and 5P double disomic addition line. The P genome chromosomes in these lines were identified based on the homoeology with wheat in our previous studies 25,27–29,33,34,38,39 . These materials were stored or created by our laboratory.…”

“…34 II-23-1 c T. aestivum L.AABBDD-II(4B + 7 A) + II(2P + 4P + 7P)44Chen et al . 39 II-11-1 d T. aestivum L.AABBDD + II(2P + 5P)46Zhou et al . 38 a Wheat– A. cristatum addition lines; b wheat- A. cristatum derivative II-3-1 was a 1P (1A) disomic substitution and 2P disomic addition line; c wheat- A. cristatum derivative II-23-1 was a multiple 4P (4B), 7P (7A) substitution line with one pair of additional 2P chromosomes; d wheat- A. cristatum derivative II-11-1 was a 2P and 5P disomic addition line.…”

Identification of 5P Chromosomes in Wheat-Agropyron cristatum Addition Line and Analysis of Its Effect on Homologous Pairing of Wheat Chromosomes

“…So far, wheat-A. cristatum 1P, 2P, 3P, 4P, 6P, and 7P disomic addition lines have been successfully created, and many excellent genes were located in specific chromosomes and transmitted into wheat (Wu et al, 2006;Han et al, 2014;Li et al, 2016a;Lu et al, 2016;Pan et al, 2017;Chen et al, 2018;Zhou et al, 2018). For instance, it has been found that A. cristatum 6P addition line carried gene clusters related to yield, such as multiple florets and grains per spike, and the 2P addition line possessed gene clusters related to disease resistance including powdery mildew, leaf rust, and stripe rust (Wu et al, 2006;Han et al, 2014;Li et al, 2016a).…”