Selection of Superior Cotton Cultivars (Gossypiume hirsutum L.) using GTBiplot Model

Cotton has special economic and agricultural importance and it is considered the most important fiber used in the world's textile industry. Identification of germplasms based on important quantitative and qualitative characteristics is necessary for the transfer of traits in crossbreeding programs and the improvement of superior cultivars. This research was carried out to evaluate cotton several genotypes of cotton based on measured quantitative and qualitative characteristics.

To evaluate genotypes of cotton using GTBiplot graphical analysis and selection of the best genotypes, an experiment including nine genotypes along with two commercial cultivars as reference checks (Bakhtegan and Golestan) carried out in the form of a randomized complete block design with 4 replications at the Darab Agricultural Research Station in 2017-2018. In this experiment, the traits of plant height, sympodial length, sympodial number, number of bolls per plant, boll weight, earliness percentage, yield, fiber length, uniformity percentage, fiber micronaire, fiber strength, fiber elongation, and lint percentage were investigated.

The results of principal components analysis showed that the three PCAs explained 80.4% of the total agronomical variability residing in tested cotton genotypes. The first two PCAs accounted for 44.6% and 22.3% of the total variation, respectively. In the first component, respectively, the traits of the yield and the number of bolls had the largest contribution in justifying the variance between the data. In the second component, earliness percentage and fiber length in the positive direction and sympodial length in the negative direction had the largest contribution in justifying the variance between the data.
In GTbiplot analysis, the polygonal diagram obtained from the analysis showed that the genotypes GTbiplot arising Bakhtegan, A-NB414, A-NBK, VA-1, VA-2, and 96-A3, which were located at the vertices of the polygon, were the superior genotypes. The results showed that A-NB414 and A-NBK genotypes were superior to other genotypes in terms of yield, plant height, boll number, uniformity, lint percentage, and earliness. The highest diversity was justified by from A-NB414, A-NBK, Bakhtegan, and Golestan genotypes. In this research, the A-NB414 and A-NBK genotypes were identified as superior in terms of measured quantitative and qualitative traits and compared with VA-1, VA-2, A3-96, 48-92, 90-92 10481, A-SKG, and 34-92 had a negative correlation.

In conclusion, the genotypes A-NB414 and A-BNK were superior to other genotypes in many quantitative and qualitative traits and they were not correlated with Bakhtegan variety which had good micronaire and boll weight. These genotypes can be used in breeding programs to achieve maximum diversity and obtain hybrids with favorable yield, early variety, with high boll weight and number, high uniformity percentage, high lint percentage, and suitable micronaire of fibers for use in the textile industry.