225An alternative to the ph1b mutant for inducing homoeologous rec ombination in
wheat is to use Ph suppressors in Ae. speltoides. Riley et al. ( 1968a , b ) transferred
stripe rust resistance gene Yr8 from Ae. comosa chromosome 2M to wheat using a
Ph1 -suppressing line of Ae. speltoides and produced the line known as Compair.
Chen et al. ( 1994 ) reported the transfer of a gene infl uencing homoeologous chro-
mosome pairing from Ae. speltoides to a wheat chromo some.
In this chapter, we review all the formally named genes transferred to common
wheat from Aegilops species, except those from Ae. tauschii. Species in Sitopsis
section, such as Ae. speltoides and Ae. longissima , have high p airing and low pair-
ing genotypes that require different transfer strategies.
9.6 Ae. speltoides
Wells and coworkers (Lay et al. 1971 ; Wells et al. 1973 , 1982 ) used radiation treat-
ment to transfer Gb5 , conferring resistance to greenbug ( Schizaphis graminum
Rond.), and Lr47 conferring resistance to leaf ru st (caused by Puccinia triticina
Eriks.) from a group-7 Ae. speltoides Tausch (2 n = 2× = 14, SS) chromosome to 7A
of wheat (Friebe et al. 1991 ; Dubcovsky et al. 1998 ). Genomic in situ hybridization
(GISH) and meiotic pairing analyses suggested that the wheat– Ae. speltoides
recombinant chromosomes present in lines CI 17883, CI 17884, and CI 17885 con-
sisted of the complete long arm of 7S#1, most of the short arm of 7S#1, and a small
distal segment derived from the short arm of wheat chromosome 7A, and therefore
it was designated as T7AS-7S#1S•7S#1L (Friebe et al. 1991 , 1996 ; Dubcovsky
et al. 1998 ). Dubcovsky et al. ( 1998 ) used induced homoeologous recombination
to shorten the Ae. speltoides segment and recovered two interstitial recombinant
chromosomes. Ti7AS-7S#1S-7AS•7AL conferring resistance to leaf rust and
Ti7AS•7AL-7S#1L-7AL conferring resistance to greenbug. This placed Lr47 on the
short arm and Gb5 on the long arm of the Ae. speltoides chromosome 7S#1.
Miller et al. ( 1988 ) used i ndu ced homoeologous recombination and transferred
leaf rust resistance gene Lr28 from Ae. speltoides to wheat. Lr28 is present in the
lines 2A/2M#4/2 and 2D/2M#3/8 (McIntosh et al. 1982 ) that were actually selected
for stripe rust resistanc e ( Yr8 from Ae. comosa ). Chromosome C-banding analysis
suggested that the wheat– Ae. speltoides recombinant chromosome in these lines
consists of the short arm of chromosome 4A of wheat, most of the long arm of 4A,
and a distal segment derived from Ae. speltoides (Friebe et al. 1996 ). Chromosome
4A of T. turgidum and T. aestivum is highly rearranged and the distal region of the
long arm is actually homoeologous to group-7S arms (Miftahudin et al. 2004 ).
Therefore, the Ae. speltoides segment transferred to the 4AL arm most likely is
homoeologous to the group-7S and the recombinant chromosome should be
described as T4AS•4AL-7S#2S.
ER Sears used induced homoeologous recombination to transfer Sr32 conferring
resistance to stem rust ( Puccinia graminis Pers.: Pers f. sp. tritici Eriks. & Henn.)
from an Ae. speltoides chromosome 2S#1 to wheat chromosomes 2A, 2B, and 2D
9 Wheat–Aegilops Introgressions