Genetic Variability and Association of Characters in Wheat (Triticum aestivum L.)
Bangshi Dhari Kotal,
In the present investigation, an attempt has been made to evaluate the genetic variability and correlation of different contributing characters associated with grain yield per plant in wheat. Fourteen genotypes were grown in Randomized Block Design with three replications and evaluated for ten characters. Analysis of variance was done from the mean data obtained in each character and correlation and path coefficient analysis were carried out. Highly significant differences and adequate genetic variability were observed among the genotypes for all the ten selected characters. In this context, it was found that numbers of effective tillers per plant and grain yield per plant were characterized by high GCV, high heritability and high genetic advance and would be effective for selection. Correlation studies and path coefficient analysis revealed the importance of number of effective tillers per plant, number of spiklet per panicle, number of grains per panicle and harvest index for improving grain yield per plant as they had positive direct effects on yield and these traits were also significantly and positively correlated with grain yield per plant. So for increasing grain yield per plant a wheat genotype should have more number of effective tillers per plant, more number of spikelet per panicle, more number of grains per panicle and high harvest index value because these characters were positively associated with grain yield and resemble high estimates of heritability along with high genetic advance. In this regard the importance of large panicle length and more 1000 grain weight could not be under mined for yield improvement.
Received: February 22, 2010;
Accepted: May 13, 2010;
Published: July 27, 2010
Wheat (Triticum aestivum
L., Graminae) is the world most cultivated food
crop known as the king of all cereal crops as its cultivation is easier, ecologically
suitable and contain high amount of nutrients. It is rich in protein (7-22%),
carbohydrate, calcium, lysine, iron, glutein, vitamin and minerals. Wheat is cultivated
over an area of 230.16 million ha with a production of 673.09 million ton in the
world (FAOSTAT, 2003
). In India it is the second important
crop after rice and covers an area over 27.75 million hectares which is about
20% of the total cultivated area under cereal. India has attained a record of
80.58 million tones of wheat production in 2008-2009 and continues to remain as
the second largest producer of wheat in the world (USDA, 2009
In the context of yield enhancement, in order to have a good choice of character
for selection of desirable genotypes under planned breeding programme, the knowledge
of nature and magnitude of variation existing in available plant breeding materials,
the association of component characters with yield and their exact contribution
through direct and indirect effects are very important. Genotypic variation,
heritability, genetic advance were calculated for different yield attributing
characters in wheat by several workers (Kheiralla et
al., 1993; Subhani and Khaliq, 1994; Gupta
and Verma, 2000; Jedynski, 2001) which revealed
that selection was effective for a population with broad genetic variability
and character with high heritability. Several workers studied the components
of variance, correlation between different yield attributing characters and
their direct and indirect effects on yield (Ismail et
al., 2001; Kumar and Sukla, 2002; Satyavart
et al., 2002; Tamam et al., 2000).
So in this background, the objective of the present investigation was to estimate
the genetic variability, association of different characters and their direct
and indirect effect on grain yield per plant with a view to identify the genotypes
with best potentiality for upgrading yield and its component characters.
MATERIALS AND METHODS
Experimental Material and Design
The present investigation was conducted at Instructional Farm of Bidhan
Chandra Krishi Viswavidyalaya, West Bengal, India during the Rabi season of
2004-2005. The farm is situated at 22.93°N latitude and 88.59°E longitudes
with an average altitude of 9.75 m above mean sea level with gangetic alluvial
sandy loam soil having good drainage facility. Fourteen genotypes (PBW 443,
HD 2733, K 0307, C 306, PBW 343, HUW 468, K 9107, UP 262, Raj 4084, PBW 550,
PBW 533, Lok 17, HD 2932 and HD 2824) were collected from different parts of
India and planted in Randomized Block Design (RBD) with three replications.
Observations were recorded from ten plants from the middle rows of the plot
excluding the border plants, for ten plant characters viz. Plant height (cm),
number of effective tillers per plant, panicle length (cm), number of spikelets
per panicle, number of grain per panicle, 1000 grain weight (g), days to flower,
days to maturity, harvest index and grain yield per plant.
Analysis of variance was done from the mean data obtained in each character.
Estimates of genetic parameters were computed (Johnson et
al., 1963). Phenotypic and genotypic correlation coefficients for all
pairs of ten characters were estimated (Robinson et al.,
1951). As there is no suitable statistical procedure for testing the significance
of genotypic correlation (Nasr et al., 1973)
only phenotypic correlations were tested. Path coefficient analysis was carried
out as described by Dewey and Lu (1959) at phenotypic
RESULTS AND DISCUSSION
Highly significant differences were obtained among the genotypes for all the ten selected characters (Table 1); this indicated adequate variability among the genotypes considered in this study. The genotype K 9107 produced the highest value regarding panicle length, no. of spiklet per panicle and no. of grains per panicle. In case of 1000 grain weight best result was found in UP 262. Genotype K 9107 with lowest plant height resembled the highest harvest index value. Regarding grain yield per plant HD 2824 showed the best result than other.
|| Mean of ten characters of fourteen genotypes of wheat (Triticum
|| Mean, range and other genetic parameters in wheat (Triticum
It was evident from the (Table 2) result that the magnitude
of Phenotypic Coefficient of Variation (PCV) was higher than the Genotypic Coefficient
of Variation (GCV) for all the characters studied. This indicates that the apparent
variation was not only due to genotypes but also due to influence of environment.
The characters like grain yield per plant, thousand grain weight, plant height,
number of effective tillers per plant and harvest index showed larger difference
between phenotypic and genotypic coefficient of variation indicating the greater
influence of environment on these characters. However, in rest of the characters
minimum difference between phenotypic and genotypic coefficients of variation
was observed indicating less environmental influence and scope of selection
for these traits. The heritability showed highest value for days to flower,
followed by number of effective tillers per plant and days to maturity. This
result showed close resemblance with the report of Fida
et al. (2001) where these characters also exhibited high heritability.
However, the genetic advance as percent over mean was found high in number of
spikelet per panicle, days to maturity, grain yield per plant, harvest index
and number of effective tillers per plant. GCV alone is not sufficient for determination
of the extent of variation that perpetuate from one generation to the next.
GCV together with heritability estimates would give a better picture of the
extent of genetic advance that can be made through selection (Johnson
et al., 1963) for estimating genetic gain under selection. In this
context, number of effective tillers per plant and grain yield per plant was
characterized by high GCV, high heritability and high genetic advance and might
be considered to be governed by additive genes and was less influenced by environmental
effect. So selection for these traits would be effective. Similar findings were
also observed by Ghimiray and Sarkar (2000) and Kumar
and Sukla (2002) where number of tillers per plants and grain yield showed
high heritability associated with high genetic advance. Mean square for GCA
effects of these two characters was also highly significant (Kashif
and Ihsan, 2003) which resemble additive genetic effects and supported the
present finding. On the other hand, characters like, panicle length, plant height,
number of grains per panicle, thousand grain weight, days to flower having high
heritability values, had low estimates of genetic advance. Therefore, these
characters are expected to be controlled by non-additive genes. The high heritability
was being exhibited due to favorable influence of environmental effects rather
than genotype and selection for such traits would not be rewarding.
Correlation coefficient at genotypic levels was, in general higher than phenotypic
level in all the characters (Table 3). Genotypic correlation
was found more significant than phenotypic correlation indicating that, there
was prevalence of environmental interaction. The high positive significant genotypic
correlation were found between number of spikelet per panicle and number of
grains per panicle, days to flower and days to maturity, panicle length and
days to flower and panicle length and days to maturity than phenotypic correlation
which indicated that there was a strong association between characters genetically
and there was some scope for selection of better yielding types. Number of effective
tillers per plant, number of spikelet per panicle, number of grains per panicle
and harvest index gave significantly positive correlation with the grain yield
per plant both at genotypic and phenotypic levels. So these characters exhibited
correlated response with the grain yield and therefore might be considered for
selection of better yield. Similar findings were observed by several previous
workers (Fida et al., 2001; Tamam
et al., 2000; Korkut et al., 2001).
They reported positive significant correlation between days to heading and plant
heights, Number of effective tillers per plant with grain yield per plant and
harvest index and between panicle length and number of grains per panicle. Sultana
et al. (2002) reported that No. of effective tillers per plant, spikelet
per spike, florets per spike, grains per spike were significantly positively
associated with grain yield per plant which was similar with the present finding
but they also reported that these characters exhibited negative correlation
with total tillers per plant.
|| Genotypic and phenotypic correlations among the ten characters
of wheat (Triticum aestivum L.)
|**Significant at 1% level, * Significant at 5% level
|| Direct and indirect effects of different characters on grain
yield/plant of wheat (Triticum aestivum L.)
|Residual effect = 0.3412
However, Randhawa et al. (1975) observed positive
and genotypically significant negative Correlation between numbers of tillers
per plant with 1000 grain weight.
In order to obtain a clear picture of the inter-relationship between different
characters, the direct and indirect effects of the different characters on grain
yield per plant were worked out (Table 4). All the direct
effects towards grain yield per plant were positive except days to flower and
days to maturity. In general, the indirect effects were either positive or negative
and lower in magnitude with low residual effect (0.3412). Considering the relationship
of all the traits with grain yield per plant the present investigation showed
the importance of number of effective tillers per plant, number of spiklet per
panicle, number of grains per panicle and harvest index for improving grain
yield per plant as they had positive direct effects on yield and these traits
were also significantly and positively correlated with grain yield per plant.
So, direct selection for these characters would be effective for yield improvement
in wheat. Direct effect of panicle length and 1000 grain weight on grain yield
was also high although these two traits showed insignificant but positive correlation
with grain yield at both the levels. Positive direct effect of panicle length
and 1000 grain weight on yield was also reported by Dokuyucu
and Akkaya (1999).
So for increasing grain yield per plant a wheat genotype should have more number of effective tillers per plant, more number of spikelet per panicle, more number of grains per panicle and high harvest index value because these characters were positively associated with grain yield and resemble high estimates of heritability along with high genetic advance. In this regard the importance of large panicle length and more 1000 grain weight could not be under mined. However, in case of selection for yield improvement the genotype should have short plant height with less time required for days to flowering and grain filling.
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