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Wheat Information Service
Number 90:42-44 (2000)
Research information
Genotypic variation for chlorophyll content and
leaf area in wheat and their relation to grain yield
M. Yasin Ashraf
Nuclear Institute for Agriculture and Biology, P.O. Box No. 128,
Jhang Road, Faisalabad, Pakistan
Wheat (Triticum aestivum L.) is an important cereal crop of
world and a staple food of the people of Pakistan. In order to feed
the ever growing population increase in the cultivated land area has
a limitation due to the problems waterlogging, and salinity, drought
and unavailability of new lands. Methods to increase yield per unit
area have therefore, to be explored. Although with the advent of high
yield varieties, the increase in wheat grain production has been
commendable during the past few years, there is scope yet for
improvement. Since yield is the result of genotype by environment
interaction, it has been suggested that by increasing photosynthetic
efficiency, productivity could be increased (Rosenow et al. 1983). It
is known that photosynthetic efficiency depends on leaf area,
chlorophyll content and the stomatal response/gas exchange.
Therefore, it is worth determining these parameters and analyzing the
correlation if any, in various locally available genotypes.
A preliminary experiment was conducted in the field at AEARC, Tando
Jam, Pakistan, using 16 wheat genotypes with five replicates.
Fertilization was done @ 172 kg N, 115 kg P205
and 5.6 kg K ha-1 with normal cultural practices. Ninety
days after sowing, six upper leaves of each tiller of each plant were
excised and their area was measured with a Leaf Area Meter (LI-3100;
LI-COR, Inc, USA) and average/leaf was calculated. Chlorophyll
content (a, b and total), of these leaves was determined according to
Arnon (1949) and the yield per plant was determined at maturity.
The results showed variation for the chlorophyll content of the
genotypes tested (Table 1). As the
chlorophyll content was calculated on per gram fresh weight however,
if same was done on per leaf, wide variations may be recorded as the
case with Vu et al. (1987) and Ashraf et al. (1994) who also
indicated that the plants with higher chlorophyll content may have
higher photosynthetic efficiency. On the basis of these facts, the
authors seem to be largely equivocal in suggesting a direct
relationship between chlorophyll content and rate of photosynthesis
(Vu et al. 1987; Ashraf and Khan 1993; Ashraf et al. 1994). By
contrast, wide variation for chlorophyll content, have also been
reported (Wright et al. 1983; Sinha and Patil 1986; Ashraf and Khan
1990; Estill et al. 1991). Leaf area and grain yield per plant also
varied significantly in these genotypes. There are many reports
indicating that genotypes with higher leaf area may have higher grain
yield (Duncan et al. 1981; Rosenow et al. 1983; Ludlow and Muchow
1990; Ashraf et al. 1992). The highest leaf area was observed in
SH-8921 and the highest yield per plant in SH-8918, but the non
significant positive correlations were recorded among total
chlorophyll content (r=0.37), leaf area (r=0.16) and grain yield per
plant. However in many cases in present study, it was observed that
varieties with higher chlorophyll content or leaf area may have
higher grain yield per plant, which is also confirmed by the
correlation values which are positive but non significant. Therefore,
these results show that leaf area and chlorophyll content cannot be
correlated with higher grain yield in the genotypes tested.
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