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Materials and methods
The experiment was conducted in the research area of the
Department of Plant Breeding & Genetics, University of
Agriculture, Faisalabad. The experimental material comprised six
wheat genotypes viz., Pak.81, LU26S, Faisalabad 85 (Fsd.85), Pasban
90 (Psbn.90), 4943 and 4072. These genotypes were crossed in all
possible combinations in a diallel fashion during the crop season
1995-96. All the F1's along with their parents were
planted in the next crop season in lines using a triplicated
randomized complete block design. Plant to plant land row to row
spacings were 15 and 25 cm, respectively. Seeds were sown in holes
(made with the help of dibble) at the rate of 2 seeds per site which
were later thinned to single healthy seedling per site after
germination. Each treatment was a single line of 5 meter length
comprising of approximately 30 plants. All the other cultural
operations including hoeing, weeding, irrigation, fertilizers, etc.
were carried out to reduce experimental error.
For the measurement of flag leaf traits, flag leaves from the main
tillers of ten guarded plants from each treatment were collected when
the plants attained their maximum vegetative growth and the leaves
had fully expanded. Flag leaf area (FLA) was measured according to
Muller (1991). Flag leaf weight was also recorded and specific flag
leaf area and weight were calculated as under:
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Specific flag leaf area = Flag leaf area / Flag leaf
weight
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Specific flag leaf weight = Flag leaf weight / Flag leaf
area
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Data collected were subjected to analysis of variance according to
Steel and Torrie (1984). To determine the gene action, graphical
analysis according to Hayman (1957) was carried out.
Results and discussion
Gene action studies
Analysis of variance revealed highly significant differences among
genotypes for all the flag leaf traits studied. Graphical analysis
conducted revealed that in case of flag leaf area positive intercept
of regression line (Fig. 1a) indicated an
additive gene action with partial dominance. These results are
similar with those of Singh et al. (1988) and Alam et al. (1990) who
also reported an additive gene action for the trait. On the basis of
location of array points, Psbn. 90 possessed the maximum dominant
genes while 4072 possessed the most recessive genes. To see whether
the distribution of dominant alleles was correlated with the
phenotype of the common parent, the values of Wr+Vr from each array
were plotted against parental values. The graph (Fig.
1b) presented that parents with smaller flag leaf area had
smaller Wr+Vr values and parents with larger flag leaf area had
greater Wr+Vr values. The correlation coefficient was positive
(0.49). Thus, it was clear that greater flag leaf area resulted due
to more recessive genes. Dominant genes decreased the flag leaf area.
Therefore, 4072 which possessed maximum recessive genes had largest,
flag leaf area and Psbn. 90 with minimum recessive genes or more
dominant genes had the smallest flag leaf area. Lonc et al. (1993)
has also reported recessive gene control for flag leaf area.
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