Investigation of Genetic Diversity and Identification of Superior Cotton Cultivars (Gossypium Hirsutum L.) using SIIG Index

Accurate knowledge of germplasms for the transfer of traits in hybridization programs is one of the requirements for the improvement of superior cultivars. The purpose of this research was to investigate the genetic diversity and selection of superior cotton genotypes with favorable yield, earliness and quality characteristics.

In order to evaluate cotton genotypes using SIIG index, an experiment consisting of 9 genotypes with 2 commercial cultivars of Fars province (Bakhtegan and Golestan) as a control, in a randomized complete block design with 4 replications, in Hassan Abad, Darab Agricultural Research Station was implemented during the cropping years of 2018 and 2019.

The results of combined data analysis showed a significant difference among genotypes in terms of quantitative traits studied, which indicated the existence of genetic diversity among genotypes. Phenotypic diversity coefficient was higher in yield and earliness percentage than genotypic diversity coefficient. Yield had high heritability (0.73) which indicates the greater role of gene effect in trait expression and selection efficiency in trait improvement in successive generations. The results of SIIG index showed that cultivars A-NB414 and A-NBK with the highest amount of SIIG were among the best cultivars and cultivars Va-1 and 96-A3 with the lowest amount of SIIG were among the weakest cultivars in this study. in order to evaluate the efficiency of SIIG index in selecting the best cultivar in terms of yield, earliness, fiber micronaire, uniformity, fiber elongation, strength and fiber lint, the cultivars were grouped according to SIIG index in 3 categories. The overall grouping results showed that with increasing the value of SIIG index, the amount of wash yield, fiber uniformity, fiber lint and earliness percentage also increased. Earliness percentage and yield were also high in cultivars A-NB414 and A-NBK, which had higher SIIG index.

The present study showed that the SIIG index was able to classify the genotypes well. In this research, A-NB414 and A-NBK genotypes along with Golestan variety with higher yield than the overall average and high SIIG index were identified as the superior genotypes that can be included in the cultivation introduction and development program. Based on the results of cluster analysis, cotton genotypes were classified into two distinct groups, which facilitates their selection and use in different breeding programs and purposes.