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in meiosis using GISH, 1BL.1RS/1R chromosome pairing was detected in 62.4 %
of the pollen mother cells (Molnár-Láng et al. 2010 ). The use of fl uorescent in situ
hybridization (FISH) with repetitive DNA probes allowed the 1R and 1BL.1RS
chromosomes to be identifi ed. The use of rye SSR markers RMS13 and SCM9
demonstrated the presence o f the 1RS arm from Kriszta besides that of Petkus in the
F 1 hybrids. In four of the 22 BC 1 progenies analyzed only Kriszta-specifi c bands
were observed with these markers, though the presence of the 1BL. 1RS transloca-
tion was detected using GISH. It can be concluded that recombination occurred
between the Petkus and Kriszta 1RS chromosome arms in the translocated chromo-
some in thes e plants (Molnár-Láng et al. 2010 ).
4.5 Genetic Mapping of the Crossability Alleles
The substitution of Chinese Spring chromosome 5B into the variety Hobbit sib was
initiated by Snape et al. ( 1987 ) to transfer crossability alleles into UK wheat variet-
ies. This task was complicated, as Hobbit sib, like other PBI wheats, did not have a
normal 5B, 7B karyotype, but contained the 5BL–7BL and 5BS– 7BS transloca-
tions. Following fi ve backcrosses to the Hobbit sib monosomic 5BL-7BL line a
disomic substitution was extracted. The substitution line Hobbit sib (Chinese Spring
5BL, 7BL) was crossed to Hobbit sib and disomic single chromosome recombinant
lines were developed. Three lines were identifi ed which had the 5BL–7BL,
5BS–7BS karyotype but were crossable with H. bulbosum and were non-necrotic
(Snape et al. 1987 ). Later, a total of 71 homozygous disomic recombinant substitu-
tion lines were generated from these crosses, exhibiting recombination between
H obbit sib and Chinese Spring 5BL (Bertin et al. 2009 ). Initially the Kr1 locus was
mapped to a 13 cm region between the microsatellite markers Xgwm213 and
Xgwm371 (Bertin et al. 2009 ). These markers were used to screen the Ph1 mutant
line, ph1b , which revealed that Kr1 mapped within the ph1b deletion region. Three
wheat BACs and the cdc2 - 2 gene, located within the Ph1b deletion region, were
used to develop additional markers for mapping. A series of recombinant substitu-
tion lines were developed in which the genome of the normally non-crossable wheat
variety Hobbit sib carried a recombinant 5BL chromosome arm containing seg-
ments from the crossable variety Chinese Spring (Bertin et al. 2009 ). The crossabil-
ity of the recombinant lines was studied by pollinating with rye in the greenhouse
over four seasons. The crossability locus Kr1 was fi ne mapped using molecular
markers with the help of 29 lines exhibiting recombinations between the Xw5145
and DR740708 markers on the 5BL long arm. A second region responsible for
crossability was detected on the 5BL arm (Bertin et al. 2009 ).
An attempt was made to improve the crossability of the semi-dwarf wheat culti-
var Courtot with rye so that it could be used in the development of primary triticale
(Gay and Bernard 1994 ). The Courtot chromosomes 5A, 5B and 5D were replaced
by their counterparts from the highly crossable Japanese cultivars Norin 29 and
Fukuhokomugi using the monosomic back-crossing technique. Throughout the
M. Molnár-Láng