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Wheat Information
Service
Number 74: 12-16 (1992)
Monosomic
analysis of some quantitative characters in wheat, Triticum
aestivum L. cv. "Chinese Spring".
Fauzia Iqbal and Ahsan A. Vahidy
Department of Genetics, University of Karachi, Karachi-75270,
Pakaistan
Monosomics occur spontaneously and can be recognized by phenotypic
observations and cytogenetic analysis. These can be used to determine
gene linkage groups, especially in polyploid plants, for
identification of genes on particular chromosomes and for
transference of genes from one chromosome to the others. Monosomic
series in hexaploid wheat, Triticum aestivum cv. "Chinese
Spring" was developed by Sears (1954).
Leaf size has a positive effect on biomass and yield of plants. In
wheat, the flag leaf makes important contribution of photosynthates.
This contribution is greatest during the stage of grain filling. Days
to heading in wheat depends upon many factors such as temperature,
sowing dates, length of days and latitude. It is a complex character
controlled by many genes. Spike length is controlled by the additive
gene action of different minor genes. The genes affecting spike
length may thus be located on many chromosomes.
In the present study, observations were taken to locate genes
governing some quantitative characters to specific chromosomes in cv.
"Chinese Spring" of common wheat through monosomic analysis. The
characters studied were: days to heading, length and width of flag
lesf and spike length.
Materials and Methods
The material for the present study comprised of 17 monosomic
lines of common wheat c v. "Chinese Spring" which germinated and
could be maintained at the Department of Genetics, University of
Karachi. The seeds were kindly provided by Prof. E. R. Sears of the
University of Columbia, Missouri, U. S. A.
Chromosomes of every seedling were counted by the general procedure
of Jahan and Vahidy (1989). The seeds were first sown in Petri dishes
and placed at 20oC. After 3 days the root tips were
harvested for the cytological confirmation of the monosomics and the
seeds were transplanted individually in small pots and kept at
20oC. Root tips were pretreated in a mixture of 0.05%
colchicine, 0.025% 8 hydroxyquinoline, and 25 drops DMSO in 100 ml
distilled water for 3 hours. They were then transferred into 1.8%
acetoorcein. The root tips were heated to just boiling point on the
spirit lamp and then squashed in 45% acetic acid. The slides were
made permanent in liquid nitrogen and mounted in euparal.
Cytologically confirmed seedlings were transferred into large pots
and kept in the screen house under natural conditions.
Days to heading was considered as the average day the spike emerged
from the boot leaf counting from the day of sowing. Observations were
also recorded on the spike length, flag leaf length, and flag leaf
width at maturity. Observations on disomics were included to make
comparisons.
The means and standard errors of the four variables were calculated.
Each monosomic line was compared with the disomic for each variable
utilizing the statistical package SPSS/PC+. The contrast used in the
analysis was "SIMPLE" as described by Norusis (1988). This allows the
comparison of a particular variable, in this case, disomics with the
rest, the monosomics. This comparison is non orthogonal in
nature.
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