GENETIC DIVERSITY IN UPLAND COTTON (Gossynium hirsutum L.)

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GENETIC DIVERSITY IN UPLAND COTTON (Gossynium hirsutum L.)

Abstract:

Two hundred and fourty seven genotypes of upland cotton were grown at Maroua and Garoua (Cameroon), and Samaru (Nigeria), in 1994 to (i) investigate the nature and extent of their genetic diversity using Principal Component and Cluster Analyses, (ii) assess the relative contribution of different traits to their total variation, and (iii) determine the relation between the clustering patterns and the geographic distribution of these accessions. A 16 x 16 partially balanced lattice experimental design, with four replicates, was used for this study. Plots consisted of single rows 5m long, spaced 1m apart at Maroua and Garoua, and 0.91m at Samaru with a plant to plant spacing of 0.40m. Data were collected on five competitive plants, wherever possible, for 25 agronomic and fibre technology traits. Analysis of variance for each trait was performed on plot mean basis. In the combined analysis of variance across locations, all the upland cotton genotypes were significantly different for all the traits evaluated. The location x genotype effects were highly significant for all the traits measured and their patterns varied appreciably over environments, indicating differential response of different traits in varying environments. At each location, significant variability for all the traits observed was also found among the genotypes of upland cotton selected. The seed cotton per plant on average was low at Samaru (43.5g), presumably due to late planting period, medium at Maroua (70.6g), and high at Garoua (I99g). Simple linear correlations, principal component and cluster analyses were performed on adjusted treatment means. At Samaru, seed cotton per plant was positively associated with reproductive traits, boll number, number of flowers per plant, but negatively correlated with (lays to first and 50% flowers opening (presumably due to an important shedding of young capsules), and fibre length. At Maroua coefficients of correlation were moderate. At Garoua strong associations were observed between seed cotton yield, plant height, number of monopodia and sympodia, flower and boll number, percent fibre and 2.5% Span Length. Two-dimensional scatter diagrammes displayed results of the principal component analyses. There was a poor resolution of individuals into groups due to the fact that the two principal components captured only about 30% of the total variation. Two large groups were formed. All genetic materials originating from African countries grouped together and showed good adaptation to the environments at the test sites. The cluster arrangements delineated more precisely the individuals into 8, 7, and 6 groups at Samaru. Maroua, and Garoua, respectively. Despite some discrepancies, in general. cluster patterns were in agreement with pedigree information The intercluster divergence measured by the Mahalanobis’ D distance varied from 1.8 to .3.8, indicating a moderate to low degree of diversity within the genetic materials studied at each location.

GENETIC DIVERSITY IN UPLAND COTTON (Gossynium hirsutum L.)

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