236
Worland et al. 1988 ). The wheat– Ae. ventricosa recombinant chromosome T7D-7D v #1
is present in the germplasms H-93-70 and VPM1, and has also been transferred to
other wheat cultivars. In addition to Pch1 , VPM1 has the Ae. ventricosa - derived leaf
rust, stripe rust, and stem rust resistance genes Lr37 , Yr17 , and Sr38 , and cereal
cyst nematode resistance gene Cre5 present on the wheat– Ae. ventricosa recombi-
nant chro mosome T2AL•2AS-2N v #1/6N v #1 (Bariana and McIntosh 1993 , 1994 ;
Bonhomme et al. 1995 ; Jahier et al. 2001 ; Tanguy et al. 2005 ; Badaeva et al. 2008 ).
Ae. ventricosa is also the source of cereal cyst nematode resistances genes Cre2
(Delibes et al. 1993 ) and Cre6 (Ogbonnaya et al. 2001 ). Delibes et al. ( 1997 ) also
transferred the Hessian fl y resistance gene H27 to wheat in the form of a 4M v #1
chromosome addition line and a 4M v #1(4D) substitution line (H-93-33) (Delibes
et al. 1997 ).
9.17 Ae. neglecta
Marais et al. ( 2009 ) transferre d leaf rust resistance gene Lr62 and the stripe rust
resistance gene Yr42 from Ae. neglecta Req. ex Bertol. (2 n = 6× = 42, U n U n X n X n N n N n )
using induced homoeologous recombination. Meiotic pairing and microsatellite
marker analyses suggested that the wheat– Ae. neglecta recombinant chromosome
T6AL-6 n #1L•6 n #1S in germplasm 03M119-71A consists of a distal segment of
wheat chromosome 6AL, a proximal segment of the long arm, and complete short
arm of a group-6 Ae. neglecta chromosome. The exact breakpoint and the homoeol-
ogous and genomic origin of the Ae. neglecta chromatin in this translocation remain
to be determined.
9.18 Concluding Remarks
The genus Aegilops has been the most favorable genetic source for wheat improve-
ment through alien gene introgression due to its close relatedness to wheat and rich
sources of unique genes for resistance to various biotic and abiotic stresses. During
the boom era of wide hybridization in wheat in the twentieth century, most of the
Aegilops species were successfully crossed with wheat (Sharma and Gill 1983 ;
Ozkan et al. 2001 ; Schneider et al. 2008 ), despite various problems preventing
transfer of genes from Aegilops species to wheat, such as crossability barriers,
gametocidal genes, and high vs. low pairing variants. Some were not successful
because they were either too large or noncompensating. Much of the more recent
work has focused on thei r improvement by further round of homoeologous pairing
and use of markers to facilitate in shortening them.
A large number of wheat– Aegilops amphiploids and chromosome addition, sub-
stitution, translocation, and introgression lines have been produced (Schneider et al.
2008 ). A total of 41 formally named resistance g enes have been transferred from
P. Zhang et al.