230
The Ae. speltoides introgression line S13, with ge nes for resistance to all three
rust pathogens, transferred by Marais et al. ( 2003 ) involves the complete 3AS of
wheat and a proximal region of 3AL. However, it could not be used commercially
due to associated gametocidal gene ( Gc ) with strong effects on plan t development,
fertility and seed quality. Marais et al. ( 2010c ) recovered interstitial recombinants in
which the leaf rust resistance gene Lr66 in S13 was separated from the Gc gene
using homoeologous recombination. Unfortunately, the stripe rust and stem rust
resistance genes in S13 were lost during selection of the line with Lr66.
Miller et al. ( 1987 ) transferred Pm12 , conferring resistance to powdery mildew
(caused by Blumeria graminis DC E. O. Speer f. sp. tritici Em. Marchal), from
Ae. speltoides to wheat chromosome 6B using induced homoeologous recombi-
nation and the recombinant chromosome can be described as T6BS-6S#1S•6S#1L
(Jia et al. 1996 ).
Lapochkina and coworkers (Hsam et al. 2003 ) transferred powdery mildew
resistance gene Pm32 from Ae. speltoides to wheat in the form of a Robertsonian
translocation (ROBT) T1BL•1S#2S using the process of uni valent misdivision dur-
ing meiosis followed by the centric fusion of the broken chromosome arms.
In addition to these formally named stem and leaf rust resistance genes, many
more introgressions/additions of Ae. speltoides chromosome segments carrying
temporarily designated genes are listed in Mujeeb-Kazi et al. ( 2013 ).
9.7 Ae. longissima
Coeloni and coworkers (Ceoloni et al. 1988 , 1992 ; Donini et al. 1995 ; Biagetti et al.
1998 ) used induced homoeologous recombination to transfer the powdery mildew
resistance gene Pm13 from Ae. longissima (Schweinf. & Muschl. in Muschl.) Eig
(2 n = 2× = 14, S l S l ) to whe a t c hromosome arms 3BS and 3DS. The wheat– Ae. longis-
sima recombinant chromosomes present in the two germplasm lines R1A and R1D
were characterized as T3BL•3BS-3S l #1S and T3DL•3DS-3S l #1S, respectively.
9.8 Ae. sharonensis
Ae. sharonensis Eig (2 n = 2× = 14, S sh S sh ) is the source of leaf rust and stripe rust
(caused by Puccinia striiformis f. sp. tritici Westend.) resistance genes Lr56 and
Yr38 (Marais et al. 2006 ). Genetic and molecular marker analyses suggested that
the wheat– Ae. sharonensis recombinant chromosome in germplasm 0352-4 was
characterized as T6AL-6S sh #1L•6S sh #1S, which consists of a distal segment of wheat
chromosome 6AL, part of the long arm of the Ae. sharonensis chromosome 6S sh #1,
and the complete short arm of 6S sh #1. Marais et al. ( 2010b ) used induced homoeolo-
go us recombination to reduce the Ae. sharonensis chromatin in this translocation
chromosome a nd obtained three leaf rust and stripe rust resistant lines (#39, #157,
P. Zhang et al.