GENETIC DIVERSITY OF DIPLOID AND TETRAPLOID COTTONS DETERMINED BY SSR AND ISSR MARKERS

Abstract

Cotton as an annual crop is mainly grown for its fiber and oil in the seed. Determining genetic diversity in the germplasm is the first step of plant breeding. This study aimed to determine genetic diversity for diploid and tetraploid cotton genotypes grown in different parts of the world. SSR (Simple Sequence Repeats) and ISSR (Inter Simple Sequence Repeats) markers were used to determine genetic relationships among Gossypium species and genotypes. Using 39 SSR and 5 ISSR markers, 173 alleles (averaging 3.93 alleles per locus) were produced from 25 cotton genotypes. Out of 173 alleles, 155 (89.60%) were polymorphic among the genotypes and polymorphic information content (PIC) values were between 0.0040 and 0.9993 averaging 0.4396. Genetic diversity ranged from 0.04 to 0.58 among all the genotypes inspected. This ratio was 0.04-0.23 within G. hirsutum L. and 0.07-0.26 within G. barbadense L. species. Out of these two species, genetic diversity ranged from 0.23 to 0.57 among other diploid and tetraploid species. Genetic diversity was low within commercial cultivars that are also frequently used in breeding programs (0.08-0.20). It is advisable to use wild type cottons to increase present genetic diversity in germplasm pools to have a better chance for the selection of the desired traits.