173desirable alleles, such as disease resistance early on and root biomass to this day,
and no better alleles are present in rye. The 1RS from cv. Petkus (in 1RS.1BL from
Aurora/Kavkaz) does not carry the greenbug resistance locus present in 1RS from
cv. Insave rye in the 1RS.1AL Amigo translocations, and the two 1RS arms carry
different rust and powdery mildew resistance loci (Hsam and Zeller 1997 ; Graybosch
et al. 1999 ). Centric translocation 1RS.1DL produced from the cv. Imperial rye
chromosome 1R carries a Sr locus allelic to Sr31 of the Aurora/Kavkaz transloca-
tion which still offers good protection against stem rust, including Ug99
(Anugrahwati et al. 2008 ). Attempts have been made to map/combine some of these
alleles into single translocations (Lapitan, personal communication; Hsam et al.
2000 ). Given the level of heterozygosity in rye, it would appear sensible to assume
that more allelic variation for various resistance and the root biomass locus/loci
must exists but testing for their presence is somewhat complicated, as it requires
sets of wheat–rye additions from wide sources.
Several different experiments with 1RS arms from different sources translocated
to different positions in the wheat genome (Ehdaie et al. 2003 ; Kim et al. 2004 ;
Waines and Ehdaie 2007 ) suggest that the Amigo-originating 1RS arm (from Insave
rye), as well as an arm from a different wheat line apparently unrelated to the
Aurora/Kavkaz source (CIMMYT line E12165) produce larger increases in root
biomass under water stress than the 1RS arm from the Aurora/Kavkaz (rye cv.
Petkus). In addition, there appear to be signifi cant position effects involved, with
1RS.1AL having the best positive effect on root biomass and the least negative
effect on the end use quality of wheat. On the other hand, Karki et al. ( 2014 ) suggest
that the 1RS.1AL translocation where the 1RS arm originates from Aurora/Kavkaz
produces larger root biomass only under normal moisture levels, and this increase
may come at the cost to grain yield.
There are several 1RS.1AL translocations with 1RS from different sources apart
from Amigo (including the original Petkus source, triticale cv. Rhino and the
E12165 wheat line from CIMMYT) but these are yet to be tested for root character-
istics. The 1RS.1BL confi guration involves more sources of 1RS, including six in
the possession of the author, one of which includes 1RS from S. montanum. Yang
et al. ( 2009 ) generated a new 1RS.1BL translocation with 1RS from S. africanum ;
another new 1RS.1BL was created from a Korean rye (Ko et al. 2002 ) and an entire
swarm appears to have occurred spontaneously in China and even recombined
themselves to produce small segment introgression s (Fu et al. 2010 ). Ren et al.
( 2009 ) generated a new 1RS.1BL translocation with a different profi le of disease
resistance, somewhat surprisingly as the donor was an inbred of Petkus, the source
of the original 1RS.1BL translocation.
Rapid spread of the 1RS.1BL Aurora/Kavkaz translocation clearly points to its
agronomic value but this does not mean that this s pecifi c 1RS arm carries the most
benefi cial alleles possible. Only careful screening may uncover the range of avail-
able variation. Moreover, research of Waines (Ehdaie et al. 2003 ; Waines and Ehdaie
2007 ) suggests that as far as root characteristics are concerned, translocation of 1RS
to 1BL may not be the best possible and in this sense the true potential of introgres-
sions of rye 1RS chromosome arm has not yet been completely exploited.
7 Introgressions Between Wheat and Rye