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Results and
Discussion
The plants were grown in the open, under natural conditions. They
were kept in the screen house to protect them from rodents and birds.
The plantation was done in Karachi during the period December 1988 to
March 1989. Karachi lies at a latitude of 24.51N and a longitude of
67.02E. During the plantation period, the maximum monthly temperature
ranged from 26.4C to 31.6C, the mean temperature being 28.4C and the
minimum from 12.7C to 17.8C, the mean temperature being 14.4C. The
range of relative humidity during this period was 58.6% to 74.6%. The
mean relative humidity was 66.3%. The monthly rainfall ranged from
1.0 to 8.0mm, they mean rainfall being 3.5mm (Source: Regional Daily
Weather Report for Sindh and Baluchistan, Regional Meteorological
Centre, Karachi Airport, Karachi).
Many genes have been identified in wheat but most of the characters
with which the plant breeder is concerned show quantitative
variation. In recent years, procedures have been developed which
enable biometrical analysis of quantitative characters. To examine
the inheritance of such characters, statistical analysis has to be
carried out and interpretations made through means, variances and
covariances.
The progress of spike development can be measured by the time taken
to achieve defined developmental stages (Kirby and Appleyard, 1987).
It is possible to quantify development by analysing the rate of
initiation of heading. When the ditelosomics were compared to the
disomics, Ditelo-1AL, 2AS, 4AL, 5AL, 6AL, 7AL, 3BL, 5BL, 6BS, 3DL,
5DL, 7DS, and 7DL showed highly significant deviations as far as days
to heading was concerned. All of these were early as compared to the
control population, their mean days to heading being less than that
of the disomics (Table
1). Literature
available showed the effect of all these chromosomes on heading time.
Bhat and Goud (1979), working on monosomic
F2
population derived
from the cross of monosomic lines of Pb. C591 with UP 301, reported
the effect of chromosomes 5A, 7A, 3D and 7D. Out of these four,
monosomic populations 7A, 3D and 7D were early while monosomic
population 5A showed delayed heading. Yoshida and Kawaguchi (1984)
worked on the monosomics and ditelosomics of 'Chinese Spring'. They
grew the monosomics for 3 weeks in the greenhouse and then
transferred them outdoors. According to them monosomic 3D and
telosomic 1AL were early and monosomics 2B, 3B, 6B, 7B and 6D and
telosomics 2AS, 6AS, 5BL, 6BL, 2DS, and 5DL were late. In addition,
the effect of chromosomes 1A, 4A, 5A, 3B, 2D and 7D of the hexaploid
wheat variety DWR. 39 of T. aestivum on heading time was
reported by Goud and Sridevi (1988). Of these the populations of Mono
6A and 7D were early while the rest were late as compared to the
control population. They, in another report, (Sridevi and Goud 1988)
found the influence of chromosomes 4A, 5A, 2B, and 6B in the
trisomics of Triticum durum cv. HD 4502. All the populations
which were trisomic for these chromosomes were late. This indicates
the presence of genes imparting lateness on these chromosomes. The
other lines which, according to our analysis, differed highly
significantly from the disomics were 3AL (F value= 42.25), 1BL
(47.90), 4BS (20.70), 7BS (50.23), 7BL (14.22), 1DS (10.17), 1DL
(60.35), 4DS (63.38) and 4DL (20.47)(Table
2). All of these
were early as compared to the disomics.
The length of the spike in wheat is predominantly controlled by
polygenes with an additive gene action (Bhat and Goud, 1979). A
comparison of the spike lengths of the ditelosomics with the disomic
population indicated that Ditelo-3AS, 4AL, 5AL, 1BS, 3BL, 4BS, 5BL,
6BS, 4DS, 4DL, 5DL and 7DS differed substantially from the disomics.
Out of these the length of the spike was increased only in
Ditelo-5BL, 5DL and 7DS, while in the rest it was reduced
(Table
1). The
involvement of these chromosomes, as far as the spike length is
concerned, is in confirmation with the work done by Bhat and Goud
(1979), Yoshida and Kawaguchi (1984), Goud and Sridevi (1988) and
Sridevi and Goud (1988). Chromosomes 3A, 4A, 1B, 2B, 3B, 5B, 3D, and
7D were reported to carry genes for spike length by Bhat and Goud
(1979). Of these, monosomic populations 4A and 2B had longer spikes
when compared to the disomics. Monosomic populations 3A, 1B, 3B, 5B,
3D and 7D were found to have reduced spike length. Yoshida and
Kawaguchi (1984) reported the effect of chromosomes 3A and 5A on
spike length. According to them, Mono 5A and Monotelo-disomic 5AS had
longer spike length (speltoidy) and Telo 3AS had shorter spike
length. Goud and Sridevi (1988) found the influence of chromosomes
4A, 5A, 6A, 7A, 3B, 4B, 5B, 6B and 7D on the length of the spike. The
families derived from Mono 1B increased the mean spike length whereas
the rest reduced it. Sridevi and Goud (1988) reported the effect of
chromosomes 4A, 5A, 2B, and 7B. Of these, populations derived from
trisomics 5A decreased the mean spike length while the rest increased
it. The other ditelosomics which, according to our study, influenced
the spike length were 1AS (F value= 4.00), 2AS (11.35), 1DS
(10.90), 1DL (14.94) and 2DL (12.64)(Table
2). Of these only
1DS increased the length while the rest of the ditelos reduced
it.
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