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Cold tolerance
In several countries cold and frost cause serious damage to wheat in
a number of ways, such as partial to complete killing of plants,
foliar damage, partial to complete head damage and spike sterility.
At ICARDA we are screening the materials in the field and employ the
crown freezing test (Tahir et al. 1991) in the laboratory. In total
2806 lines/cultivars from different countries (Table
2) were evaluated at Haymana - Turkey under field conditions and
in the freezing chambers at -11oC. Since the mortality
under field conditions in the germplasm. from Algeria, Ethiopia,
Pakistan and Afghanistan was more than 80%, hence not evaluated in
the freezing chambers. The data from the freezing chambers revealed
that 30 and 45% of the material from Iran and Turkey, respectively,
had more than 50% survival, however, 15 and 25% of the lines from
these two countries showed high level of cold tolerance (75%
survival) at -11C, whereas from other countries (Syria and Morocco)
none of the lines was found to have more than 50% survival (Fig.
4). To overcome the problem of massive cold damage in wheat in
countries of West Asia and North Africa efforts were made to
incorporate cold tolerance from other sources into the locally
adapted germplasm. The breeding material is subjected to evaluation
and screening at different stages of development. In the initial
years of 1980-82 the cold tolerance was relatively very low, however
in the subsequent years through continuous evaluation/testing
significant progress was made to generate and develop cold tolerant
wheat material. The new wheat germplasm (Fig.
5) shows very high level of cold tolerance and only a small
proportion of the material had more than 50% damage at -11C in
comparison to local germplasm (Fig. 4).
Majority of the segregating populations (IWFWSP) and International
Winter/Facultative Wheat Observation Nursery (IWFWON) had 63 and 57%
lines, respectively which had more than 75% survival. Only a very low
percentage (<l0%) of the new material was completely killed,
inspite of the fact that 30% of the material was of facultative type
and 15% of spring type. The results clearly show that cold tolerance
level of spring/facultative wheats can also be improved without
incorporating vernal or photoperiod sensitive gene(s) which are
generally associated with cold tolerance.
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