Tetraploid Induction and Identification of <i>Gossypium arboreum</i>

Abstract

Gossypium arboreum (2n = 26, A2) is a diploid species with limited production in acreage com-pared with G. hirsutum and G. barbadense. However, its unique traits such as insect and disease resistance contribute an important germplasm to cotton breeding. So polyploid manipulation for G. arboreum is an effective approach of germplasm development. This research focused on tetraploid induction of G. arboreum by colchicine. Morphology and cytology identifications for obtained mutants were also conducted. The seedling growth and development of all mutants was more stunted than controls. According to preliminary morphological characteristics, mutant rates in different treatment were statistically estimated and the highest mutant rate was 42.31% under the treatment of 0.1% colchicine for 24 hours. The chromosome number of most mutants was 2n = 4x = 52, while the chromosome number of diploid controls was 2n = 2x = 26 by cytology observation of root tip cells. By microscope observation of low leaf epidermis, there were significant differences for stoma area between tetraploids and diploids. The meiosis behavior of the induced tetraploid was much more complex than that of the diploid. At diakinesis, some univalent, trivalent and polyvalent were also observed besides bivalent and quadrivalent. There were different kinds of polyad in tetraspore period of mutants. The dissociate chromosomes existed during metaphase I and II, the unbalance separation of chromosomes existed during anaphase I and II. As a result, tetraploid mutants of G. arboreum were identified and their desirable traits would be further evaluated to incorporate into next breeding program.