Abstract
Inherent divergence and parenthood of germplasm could play an important role in genetic improvement of cotton. The present investigation was conducted to assess the genetic divergence among fourteen locally cotton genotypes and six exotic genotypes using multivariate Mahalanobis D2 statistics and metroglyph analysis. The results showed highly significant differences among these genotypes for all the studied quantitative characters. The Mahalanobis D2 statistics showed that the dissimilarity coefficients were significant and highly significant, which ranged from 3.263 to 190.89, indicating highly genetic divergence for these cotton genotypes. Seed cotton yield and fiber strength were account about 83% of total genetic divergence. The metroglyph analysis grouped these genotypes into eight different clusters based on seven quantitative cotton characters. The inter-cluster D2 values ranged from 11.381 to 178.902 between these groups, while, the intra-cluster D2 values ranged from 3.263 to 47.806 within each group. On the basis of this grouping, it was concluded that hybridization between genotypes of different clusters might be expected to give new genetic recombinants for different economic characters. These informations could be utilized for hybridization between distinct genotypes to increase genetic cotton variability.
Highlights
Genetic divergence is the basis for any crop improvement program
Metroglyph analysis and index scoring have been used as tools to assess genetic variability within seven cotton cultivars (Khan et al 2007), and to separate cotton genotypes based upon their reaction to biotic (Haidar et al, 2012) or abiotic stress (Aslam et al, 2013)
Data were subjected to an analysis of variance (Steel et al, 1997), followed by calculation of genetic divergence using the Mahalanobis D2 statistic with the genotypes grouped on the basis of minimum generalized distance as described by Mohammadi and Prasanna (2003) using Toucher’s method (Rao, 1952)
Summary
The present investigation consisted of the selfed seeds of 20 cotton genotypes belonging to G. barbadense. These genotypes were raised in a completely randomized block design with three replications during the 2012/2013 growing season at the Sakha Experimental Station, Kafr El-Sheikh, Agricultural Research Center, Egypt. Data were subjected to an analysis of variance (Steel et al, 1997), followed by calculation of genetic divergence using the Mahalanobis D2 statistic with the genotypes grouped on the basis of minimum generalized distance as described by Mohammadi and Prasanna (2003) using Toucher’s method (Rao, 1952). A scatter diagram was plotted taking the two most variable characteristics: seed cotton yield as ordinate (X axis) and lint percentage as abscissa (Y axis). All other characteristics were represented as rays at different positions on the
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