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genome is a rich source of resistance to various biotic and abiotic stresses that could
contribute to the improvement of wheat (Cox et al. 1994 , Assefa and Fehrmann
2000 ; Colmer et al. 2006 ).
Wild barley has also shown to be an important source of genes/traits for crop
improvement. Various morphological, agronomic and physiological traits of inter-
est have been reported in wild barley, which result in tolerance of barley under
drought stress conditions (Ivandic et al. 2000 ; Grando et al. 2001 ). Wild barley is
also a source of resistance to diseases such as powdery mildew (Blumeria gramin-
isf.sp. hordei), rust (Puccinia hordei) and scald (Rhynchosporium secalis)
(Ceccarelli and Grando 1987 ; Eglinton et al. 1999 ).
Natural hybridization may have occurred for evolution of wheat species and
types; the wild diploid wheat Triticum monococcum (genome AmAm) naturally
crossed with the Aegilops speltoides (genome BB) millions of years ago which led
to evolution of tetraploid emmer wheat, Triticum dicoccum (AABB) (Mujeeb-Kazi
et al. 1996 ). The domestication of emmer give rise to durum wheat, Triticum turgi-
dum var. durum. Somewhere in Fertile Crescent around 8000 to 10,000 years ago
the durum wheat (2n = 28, AABB) hybridized with a diploid wild grass Aegilops
tauschii (genome DD) which led to the origin of hexaploid wheat (Triticum aesti-
vum) (Mujeeb-Kazi et al. 1996 , Feldmann 2001 ).
Hawkes et al. ( 2000 ) reported that the old wheat varieties are now difficult to find
in Turkey, Iraq, Afghanistan and Pakistan, which 30 years ago were easily available.
Smale et al. ( 2002 ) reported that in 1997 the landraces of spring bread wheat were
planted on only 3 % of the cropped area. Hirano et al. ( 2008 ) reported that landraces
have rare alleles. There are many landraces which have not been explored some of
them are now only limited to gene banks these genetically diverse germplasm col-
lections in genetic resource centers is of great importance (Hoisington et al. 1999 )
and the use of this germplasm is vital to raise yield potential and stability and for
improvement in tolerance to diseases and pests (Tanksley and McCouch 1997 ; Van
Becelaere et al. 2005 ).
In grain legumes, important sources of resistance in wild species can be exploited
in chickpea, pigeonpea and groundnut. Wild species of chickpea, pigeonpea and
groundnut have been extensively studied and quite few of them have demonstrated
high level of resistance/tolerance to a number of stresses. Such as wild chickpea
species, C. bijugum, C. judaicum, and C. pinnatifidum have shown important
sources resistance/tolerance to multiple stresses (Sharma et al. 2013 ). Wild pigeon-
pea species particularly, C. scarabaeoides, C. acutifolius, C. platycarpus, C. reticu-
latus, C. sericeus, and C. albicans have resistance to pod borer (Sujana et al. 2008 ;
Sharma et al. 2009 ). Wild pigeonpea species have resistance to Alternaria blight,
Phytophthora blight, mosaic virus, nematodes and also show tolerance to drought
and salinity (Upadhyaya et al. 2013 ). Wild groundnut species possess resistance/
tolerance to many biotic/abiotic stresses (Upadhyaya et al. 2012 ).
Q. Sohail et al.