GENETIC DIVERSITY IN COTTON (Gossypium hirsutum L.)
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Date
2011
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ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY
Abstract
The present investigation was carried out during kharif 2010-11 at
Agricultural College Farm, Bapatla, with 40 genotypes of cotton (Gossypium
hirsutum L.).
The variability, genetic divergence, character association and the
magnitude of direct and indirect effects of yield component traits with seed cotton
yield were studied along with morphological characterization of the lines using
IBPGR descriptors. The data were recorded on 27 morphological characters, viz.,
stem pigmentation, stem hairiness, leaf shape, leaf lobe number, leaf size, leaf
colour, leaf pubescence, leaf appearance, leaf gossypol glands, leaf nectaries, leaf
petiole pigmentation, type of bract, number of serrations of bract, sepal
pigmentation, petal colour, petal spot, position of stigma, filament colouration,
anther colour, boll bearing habit, boll size, boll colour, boll shape, boll surface,
boll prominence of tip, boll opening and plant habit, and 15 quantitative characters
viz., days to 50% flowering, plant height (cm), number of monopodia per plant,
number of sympodia per plant, number of bolls per plant, boll weight (g), ginning
out-turn (%), seed index (g), lint index (g), 2.5% span length (mm), micronaire
(10 -6 g/in), bundle strength (g/tex), uniformity ratio, fibre elongation (%) and seed
cotton yield per plant (g).
IBPGR descriptors data revealed that variability was present for thirteen
characters out of twenty seven descriptors studied and they can be exploited for
varietal identification and IPR protection along with crop improvement
programmes.
The analysis of variance revealed significant differences among the
genotypes for all the characters studied indicating the data generated from the
diverse material will yield reliable information.
The genotypic coefficients of variation for all the characters studied were
lesser than the phenotypic coefficients of variation indicating the masking effects
of the environment. The characters viz., number of sympodia plant-1, number of
bolls per plant, boll weight and seed cotton yield per plant exhibited moderate
phenotypic coefficient of variation. Moderate heritability coupled with moderate
genetic advance was noted for number of sympodia plant-1, number of bolls per
plant and seed cotton yield per plant. This indicates the presence of non-additive
gene action and further improvement of these traits would be possible through
heterosis breeding rather than simple selection.
The correlation and path coefficient analyses together indicated that plant
height, number of sympodia plant-1, number of bolls plant-1 and seed index had
significant positive and positive direct effects on seed cotton yield per plant
indicating the existence of true relationship between these characters and their
exploitation in selection programmes.
The results of multivariate analysis revealed that the distribution of 40
genotypes into seven clusters in case of D2 analysis and agglomerative cluster
analysis. The distribution of genotypes into these clusters was at random
indicating genetic diversity and geographical diversity were not related.
Mahalanobis’ D2 statistic indicated that the characters, fibre elongation,
seed index, number of monopodia plant -1, boll weight, lint index, micronaire,
ginning out-turn, 2.5% span length, seed cotton yield per plant and uniformity
ratio contributed maximum towards genetic divergence.
Based on the inter- cluster distances among the groups suggestions were
made to attempt crosses after confirming the general combining ability of the
genotypes from the clusters IV (KH-11, RAH-101) and VII (COP-420) which had
maximum inter-cluster distance (276.846) to obtain better heterotic and desirable
segregants.
In the principal component method, first 5 principal components explained
78.35% of the variability. The first component was characterized by the high
loading values of plant height, boll weight, days to 50% flowering, seed cotton
yield per plant, number of bolls per plant, ginning out-turn and fiber elongation in
assessing the genetic diversity. Agglomerative cluster analysis revealed crosses
can be attempted between the clusters III (KH-11, RAH-101) and VII (COP-420)
which had maximum inter cluster distance to obtain desirable segregants.
The genotypes KH-11 and RAH-101, and COP-420 showed maximum
inter-cluster distance and wide genetic distance in multivariate analysis. These
genotypes can be exploited in hybridization programme for identification of
desirable segregants.
Description
Keywords
livestock, manpower, organic compounds, aromatic compounds, summer, purification, seasons, biological phenomena, glucose, acidity, COTTON, Gossypium hirsutum L.