1712007 ) and this may explain confusing results of individual experiments: the yield
effect was present, or was more pronounced only in some, usually more demanding
environments (Villareal et al. 1997 , 1998 ) and in spring rather than winter wheats.
Perhaps for this reason the spread of the translocation has accelerated after the
involvement of CIMMYT (Rajaram et al. 1983 ) as it introduced the translocation to
spring wheats with a global reach and its benefi ts became more pronounced. The
translocation has also been transferred to durum wheat, by backcrosses (Friebe et al.
1987 ) where it appears to have a similar positive effect on grain yield (Villareal
et al. 1997 ).
While the positive effect of the 1RS.1BL translocation on grain yield is indisput-
able, so is its negative effect on bread making quality. It is not entirely clear whether
this negative effect is due strictly to the presence of the rye secalin locus Sec - 1 on
1RS, or the absence of wheat storage protein loci on 1BS ( Glu - B1 , Glu - B3 plus
some others) or the combination of both factors. In pairs of isogenic lines that differ
by the presence/absence of the translocation, the presence of Sec - 1 is always associ-
ated with the absence of all 1BS-located wheat storage protein loci, and vice versa.
Hence, the actual contribution of each locus cannot be measured. However, tests of
sets of isogenic lines indicated that the negative impact of rye secalin ( Sec - 1 ) pres-
ence is greater than that of the absence of wheat loci (Kumlay et al. 2003 ) and of the
three possible positions of 1RS in the wheat genome , that in the D-genome ( trans-
location 1RS.1D L) was the most detrimental to bread making quality while
1RS.1AL was the least. This position effect of course measures relative contribution
of the storage protein loci on the short arms of group-1 chromosomes to the overall
bread making quality, as the Sec - 1 locus is always the same.
Sebesta and Wood ( 1978 ) created another centric translocation, 1RS.1AL, to
transfer into wheat a locus for resistance to greenbug, a serious pest of wheat in the
South-Eastern USA. While the translocation was offi cially produced by irradia-
tion, the fact that it is centric makes it much more likely to be a product of centric
misdivision and fusion, very much of the same nature as the 1RS.1BL transloca-
tion (Zeller and Fuchs 1983 ). This translocation was fi rst released in cv. Amigo;
since then it has spread to many soft wheats in the USA. Among the 1RS wheats in
nurseries listed at http://www.ars.usda.gov/Research/docs.htm?docid=11932 about
one half are 1RS.1AL. In the compendium of Schlegel ( http://www.rye-gene-map.
de/rye- introgression /index.html ) about 10 % of cultivars released since 2000 carry
1RS.1AL and it appears that it has begun to spread beyond the USA. This translo-
cation also appears to enhance grain yield in wheat (Villareal et al. 1996 ; Kumlay
et al. 2003 ; Kim et al. 2004 ) apparently also by increasing the root biomass (Ehdaie
et al. 2003 ; Waines and Ehdaie 2007 ). Its impact on breadmaking quality appears
to be less severe than that of the 1RS.1BL translocation (Espita-Rangel et al.
1999a , b ).
Transloc ation 1RS.1BL served for many cytogenetic exercises, including un-
translocating the two arms, moving the 1RS arm to each of the three wheat genomes
and re-translocating it again to each of the long arms of group-1 homoeologues in
Pavon 76 wheat. In the end, a set of isogenic lines was produced (Fig. 7.2 ) where the
same chromosome arm 1RS, as it was originally derived from rye cv. Petkus (Zeller
7 Introgressions Between Wheat and Rye