Introduction: The Ph1 locus in polyploid wheat enforces strictly bivalent behaviour in meiotic metaphase I, by preventing homoeologues from crossing over. It has always been considered as completely dominant as no homoeologous metaphase I pairing has ever been detected with its single dose present. However, Ph1 also affects pairing and crossing over of homologous chromosomes. Methods: Homologous crossover frequencies with Ph1 in two, one, and null doses were scored cytologically, as exchanges within a ca. 9.5–9.9 Mbp terminal wheat segment of a wheat-rye translocation T-9 and corresponding segments in chromosome arms 1BS originating from four wheat cultivars. Results: In all cases, the crossover rates in the tested homologous segment of wheat genome, with a single dose of Ph1 present, were intermediate between those at two and null Ph1 doses. Averaging across all four chromosomes, the crossover rate with a single dose of Ph1 present was 37% higher from that with two doses and 46.4% lower of that with a zero dosage. Conclusion: The Ph1 locus in wheat affects homologues and appears to operate in a dosage-dependent manner.

1.
Riley
R
,
Chapman
V
.
Genetic control of the cytologically diploid behaviour of hexaploid wheat
.
Nature
.
1958
;
182
(
4637
):
713
5
.
2.
Sears
ER
.
Genetic control of chromosome pairing in wheat
.
Annu Rev Genet
.
1976
;
10
(
1
):
31
51
.
3.
Sears
ER
,
Okamoto
M
. Intergenomic chromosome relationships in hexaploid wheat. Proc 10th International Congress of Genetics, Montreal.
1958
;
2
:
258
259
.
4.
Dubcovsky
J
,
Luo
MC
,
Dvořák
J
.
Differentiation between homoeologous chromosomes 1A of wheat and 1Am of Triticum monococcum and its recognition by the wheat Ph1 locus
.
Proc Natl Acad Sci USA
.
1995
;
92
(
14
):
6645
9
.
5.
Luo
MC
,
Yang
L
,
Kota
RS
,
Dvořák
J
.
J Recombination of chromosomes 3Am and 5Am of Triticum monococcum with homoeologous chromosomes 3A and 5A of wheat: the distribution of recombination across chromosomes
.
Genetics
.
2000
;
154
(
3
):
1301
8
.
6.
Danilova
TV
,
Poland
J
,
Friebe
B
.
Production of a complete set of wheat-barley group-7 chromosome recombinants with increased grain β-glucan content
.
Theor Appl Genet
.
2019
;
132
(
11
):
3129
41
.
7.
Rey
MD
,
Calderón
MC
,
Prieto
P
.
The use of the ph1b mutant to induce recombination between the chromosomes of wheat and barley
.
Front Plant Sci
.
2015
;
6
:
160
.
8.
Koebner
RMD
,
Shepherd
KW
.
Controlled introgression to wheat of genes from rye chromosome arm 1RS by induction of allosyndesis: 1. Isolation of recombinants
.
Theor Appl Genet
.
1986
;
73
(
2
):
197
208
.
9.
Naranjo
T
,
Fernandez-Rueda
P
.
Pairing and recombination between individual chromosomes of wheat and rye in hybrids carrying the ph1b mutation
.
Theor Appl Genet
.
1996
;
93
(
1–2
):
242
8
.
10.
Lukaszewski
AJ
.
Physical distribution of translocation breakpoints in homoeologous recombinants induced by the absence of the Ph1 gene in wheat and triticale
.
Theor Appl Genet
.
1995
;
90
(
5
):
714
9
.
11.
Lukaszewski
AJ
.
Manipulation of the 1RS.1BL translocation in wheat by induced homoeologous recombination
.
Crop Sci
.
2000
;
40
(
1
):
216
25
.
12.
Devos
KM
,
Atkinson
MD
,
Chinoy
CN
,
Francis
HA
,
Harcourt
RL
,
Koebner
RMD
, et al
.
Chromosomal rearrangements in the rye genome relative to that of wheat
.
Theor Appl Genet
.
1993
;
85
(
6–7
):
673
80
.
13.
Lukaszewski
AJ
,
Porter
DR
,
Baker
CA
,
Rybka
K
,
Lapinski
B
.
Attempts to transfer Russian wheat aphid resistance from a rye chromosome in Russian triticales to wheat
.
Crop Sci
.
2001
;
41
(
6
):
1743
9
.
14.
Dvořák
J
,
McGuire
P
.
Nonstructural chromosome differentiation among wheat cultivars with special reference to differentiation of chromosomes in related species
.
Genetics
.
1981
;
97
(
2
):
391
414
.
15.
Fan
C
,
Hao
M
,
Jia
Z
,
Neri
C
,
Chen
X
,
Chen
W
, et al
.
Some characteristics of crossing over in induced recombination between chromosomes of wheat and rye
.
Plant J
.
2021
;
105
(
6
):
1665
76
.
16.
Fan
C
,
Luo
J
,
Sun
J
,
Chen
H
,
Li
L
,
Zhang
L
, et al
.
The KL system in wheat permits homoeologous crossing over between closely related chromosomes
.
Crop J
.
2023
;
11
(
3
):
808
16
.
17.
Crossway
A
,
Dvorák
J
.
Distribution of nonstructural variation along three chromosome arms between wheat cultivars Chinese Spring and Cheyenne
.
Genetics
.
1984
;
106
(
2
):
309
24
.
18.
Dvořák
J
,
Wang
L
,
Zhu
T
,
Jorgensen
CM
,
Deal
KR
,
Dai
X
, et al
.
Structural variation and rates of genome evolution in the grass family seen through comparison of sequences of genomes greatly differing in size
.
Plant J
.
2018
;
95
(
3
):
487
503
.
19.
Clark
JA
,
Martin
JH
.
The Club wheats, USDA bulletin to farmers no. 1303
.
Washington
:
Government Printing Office
;
1922
.
20.
McCallum
BD
,
DePauw
RM
.
A review of wheat cultivars grown in the Canadian prairies
.
Can J Plant Sci
.
2008
;
88
(
4
):
649
77
.
21.
Datta
A
,
Hendrix
M
,
Lipsitch
M
,
Jinks-Robertson
S
.
Dual roles for DNA sequence identity and the mismatch repair system in the regulation of mitotic crossing-over in yeast
.
Proc Natl Acad Sci U S A
.
1997
;
94
(
18
):
9757
62
.
22.
Shen
P
,
Huang
HV
.
Homologous recombination in Escherichia coli: dependence on substrate length and homology
.
Genetics
.
1986
;
112
(
3
):
441
57
.
23.
Shen
P
,
Huang
HV
.
Effect of base pair mismatches on recombination via the RecBCD pathway
.
Mol Gen Genet
.
1989
;
218
(
2
):
358
60
.
You do not currently have access to this content.