Evaluation of Variation and Identification of Effective Traits on Seed Cotton Yield in Iranian Upland Cotton Genotypes (Gossipium hirsutum L.)

Cotton (Gossypium spp.) is one of the most important agricultural products in the world. It is one of the crops that have provided the connection between the two sectors of agriculture and industry and it plays a very valuable role in the economies of countries. The objectives of this study were to investigate the diversity of agronomic and morphological traits, to identify the traits affecting the seedcotton yield and finally the grouping of tetraploid cotton cultivars in the country.

40 different cotton genotypes including commercial, imported and hybrid cultivars were cultivated and studied in the farm of Kashmar Agricultural Research Station in 2016-2017 in a randomized complete block design with three replications. The traits of number of open and closed bolls, crown diameter, first harvest yield, second harvest yield, total yield, and boll weight, number of bolls, number and length of vegetative and reproductive branches, plant height and early maturity of the crop were measured.

According to the results of descriptive statistics, the number of open and closed bolls, seedcotton yield, early maturity and boll weight had the highest range and coefficient of variation which showed the phenotypic variation of these traits in the studied genotypes. Cluster analysis in terms of the studied traits divided the genotypes into three main groups. In order to check the accuracy of cluster analysis grouping, the detection function was used. The results of the detection function also showed that the genotypes were correctly grouped and the success rate of the detection function in identifying the groups was high that 89.3, 100 and 71.4 percent of the genotypes were properly grouped in their groups, respectively. Also, based on the results of the canonical detection function, the most important traits affecting the seedcotton yield of cotton genotypes were early maturity, number of closed bolls and boll weight. Both cluster analysis and detection function methods were divided the studied genotypes into three separate groups. In a way the results of the detection function showed that the genotypes were correctly grouped in the cluster analysis method. The genotypes of group 1 that included 28 genotypes, had the lowest average of plant height and along with group 2, it also had the lowest average number of closed bolls. Also, the genotypes of the first group and the second group had the highest mean of seedcotton yield and early maturity. On the other hand, the second group, which included 5 genotypes, had the lowest mean of the traits boll weight and percentage of fibers.

Based on the total results, the selection of the first group of genotypes for breeding programs to increase its seedcotton yield through boll weight, early maturity and fibre percentage traits can help us to achieve this goal.