96
Synthetic hexaploid lines and their derivatives were intensively used in breeding
programmes for stress resistance. They provide new genetic variability for adapta-
tion to drought, high temperature, salinity, waterlogging and soil micronutrient
imbalances (Trethowan and Mujeeb-Kazi 2008 ). Concerning their resistance to
biotic stresses, these lines carry resistance to all three rust diseases, caused by
Puccinia triticina, P. graminis f.sp. tritici and P. striiformis f.sp. tritici. Their resis-
tance reactions varied from 1 % for Septoria nodorum glume blotch to 82 % for
Septoria tritici blotch. In addition, numerous authors reported the succeesful use
of synthetic-derived backcross lines in environments with constraints such as
drought, and white-grained lines resistant to pre-harvest sprouting were selected
(Ogbonnaya 2011 ).
According to studies carried out by Warburton et al. ( 2006 ) using SSR molecular
markers , there has been a very signifi cant increase in the genetic diversity of recently
developed synthetic hexaploid wheat derivatives. The inherent diversity of the new
synthetic derivatives is comparable to that of the landraces; however, they also
exhibit improved yield, disease resistance, abiotic stress tolerance and better end-
use quality.
The aim to use alien gene introgression to increase genetic diversity goes back to
a long tradition, it is almost as old as the conscious selection. When a trait of interest
was not available in the same species plant breeders screened related species to
identify the desired character. Common wheat is an excellent crop in this respect as
it has several relatives within the same genus to produce interspecifi c hybrids and
intergeneric hybrids between different genera to develop new genotypes with useful
traits. Plant breeders put a lot of emphasis to select new genetic resources derived
from alien gene introgression. Many decades of tremendous work characterized
these activities to overcome “bottlenecks” to introduce genes into the cultivated
crops and new varieties, useful for the whole mankind. Effi cient alien gene intro-
gression programs require new molecular methods and genomic tools to develop
new germplasm in pre-breeding programmes, and the introgression of new germ-
plasm into the elite wheat pool. It is evident using alien genes in crop breeding that
both the food security and safety became better in the World agriculture.
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