“AN EMPIRICAL ASSESSMENT OF GENETIC DIVERGENCE IN COTTON (Gossypium hirsutum L.): A MULTIVARIATE APPROACH”
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Date
2018-07
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JAU,JUNAGADH
Abstract
The present investigation was carried out on secondary data of the “Preliminary evaluation trial under irrigated conditions” conducted during kharif – 2015 at Cotton Instructional Farm, Junagadh Agricultural University, Junagadh with 58 genotypes of cotton (Gossypium hirsutum L.). The data were subjected to different statistical analyses viz.; ANOVA, D2 statistical analysis and principal components analysis to assess the magnitude of genetic variability present in the test material, the extent of genetic diversity in cotton, group the genotypes by using Tocher method and identify indicator of genetic diversity of genotypes.
The analysis of variance revealed that mean squares due to genotypes were found significant for the days to 50% flowering (139.384**), plant height (161.175**), number of sympodia per plant (4.560**), number of bolls per plant (138.983**), seed cotton yield (kg/ha) (568611.54**), ginning % (8.588**), number of monopodia per plant (1.637*) and seed index (1.480*) except for the boll weight (0.204NS) and lint index (0.549NS).
The values of PCV for all the characters were found more than it’s GCV. High estimates of GCV were reported for the characters viz.; number of monopodia per plant (29.99) and seed cotton yield (kg/ha) (21.56), while the number of boll per plant (19.54) had moderate and the remaining characters had low GCV. The characters viz.; number of sympodia per plant (14.0) and plant height (24.0), then the boll weight (44.9), seed index (52.6) and lint index (53.8) and then the ginning percentage (70.3), numbers of bolls per plant (77.8), seed cotton yield (kg/ha) (78.3), numbers of monopodia per plant (94.6) and days to 50% flowering (95.6) were categorized as the characters with low, moderate and high heritability, respectively.
The results of test of significance for total D2 values carried out by χ2 test revealed that out of total possible combinations 1653 among 58 genotypes based on 10 characters 47, 40 and 1566 cases were found non - significant, significant and highly significant, respectively. By using Tocher method, 58 genotypes of cotton were grouped into 20 clusters based on genetic divergence assessed by Mahalanobis’ D2 - statistics. Among which, the clusters III, V, VI, XI, XIII, XV, XVI, XVIII and XIX were solitary, the cluster II had 12, the cluster I had 9, cluster
ABSTRACT
VIII had 8, the cluster IX, X, XII and XIV had 3 and the clusters IV, VII, XVII and XX had 2 genotypes.
The maximum intra cluster distance was recorded for the cluster XX (38.04) followed by the cluster XVII (37.36), cluster XIV (34.64), clusters X and I (32.72), cluster VIII (28.42), cluster VII (27.97), IX (26.02), cluster (30.23), cluster XX (38.04), cluster XVII (37.36), cluster XIX (35.89), clusters II (25.57) and IV (21.85). Whereas the inter-cluster distance was maximum between cluster IX and XVI (482.20) followed by cluster XII and XVIII (407.46), clusters IX and XX (393.83), clusters XVIII and XX (393.55), clusters XIX and XX (391.60) and clusters III and XVI (382.10). This suggested that there is wide genetic diversity among genotypes for studied characters.
It could be inferred based on the results of percent contributions of different characters towards the total genetic divergence in 58 genotypes of cotton that the days to 50 % flowering contributed maximum (39.75 %) followed by number of bolls per plant (23.23 %), ginning percentage (6.47 %), number of monopodia per plant (6.41 %) and number of sympodia per plant (4.90 %) as they have ranked first 657, 384, 107, 106 and 81 times in all possible pairs of 58 genotypes, respectively so these characters are to be considered as crucial for further breeding programme to improve cotton crop.
The result of principal component analysis presented in scree plot revealed that all ten principal components showed greater than one eigen values which contributed 100.00 per cent of total variation among 58 cotton genotypes. By examining scree plot it was evident that first five PCs had been captured considerable variability, among which PC1 and PC2 showed (28.55 %) and (19.18 %) variability with the eigen values (2.86) and (1.92), respectively.
The biplot based on factor loadings of 58 genotypes and 10 characters of cotton showed that the lint index, ginning percent, numbers of monopodia per plant, days to 50% flowering, numbers of sympodia per plant and plant height were found crucial among these first two characters had positive and remaining with negative effects to PC1 and PC2, respectively. While 11, 15, 21, 32, 33, 37, 39, 40, 41, 45, 53 and 55 with positive effects and 7, 8, 9, 10, 14, 17, 19, 20, 22, 23, 24, 25, 30 and 58 with negative effects towards the total variation exhibited by PC1 and PC2, respectively were found important.
The comparison of results obtained by principal component analysis and D2 statistics analysis showed that except the characters i.e. numbers of bolls per plant the remaining characters viz., days to 50% flowering, ginning %, numbers of monopodia per plant and numbers of sympodia per plant were found crucial. Incase of genotypes viz., G7, G8, G10, G17, G22, G37, G53 and G56 were found to be important, except the genotype viz., G1, G27, G43 and G44
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AGRICULTURAL STATISTICS