The using of gibberellic acid hormone on cotton mature embryo resulted by crossing between wild and commercial species on artificial medium

Abstract

The wild species of cotton have important role in cotton breeding due to their favorable traits, which include pest and disease resistance, drought tolerance, fiber quality and male cytoplasmic sterility. Transferring these favorable genes from wild species to commercial cultivars of cotton by the traditional methods or classical plant breeding procedure will be very difficult and impossible. This is due to the following: Confronting disordering in flower structure, the problems involved in cotton flower pollens germination in stigma level and destruction of embryo and endosperm in different stages of evolution. The first sign of these problems is the falling of ovary. Therefore, the first and important barrier in crossing between diploid and tetraploid cotton species is the inability of hybrid seeds to produce. Solving of these problems can be the first step in hybridizations programs. The artificial control of fertilization by the gibberellic acid (GA3) after crossing and hybrid embryo culture in the media will increase probability of hybrid plants production. In this study, three species named Sahel (tetraploid), Hashemabad (diploid) and Kashmar (diploid) were used. The parental species were planted on six plots and crosses were made between them. It must be noticed that we used Sahel species as paternal and the two diploid species as maternal species. As the study continues, two investigations were separately done on hybrids. Firstly, it consisted of using different amount of Gibberellic acid after pollination for the maintenance of bolls and secondly, 45 days embryos of all the crosses combined were cultured on liquid and solid M.S media. The results show that when hormone was not used, the amount of bolls that fell was 100%, but when Gibberellic acid was applied at 100ppm concentration, there was considerable differentiation in maintenance of bolls. The Hashemabad cultivar created bolls more than Kashmar but the percentage of seeds inside the bolls was so lower than Kashmar cultivar. In comparison between parents used and their hybrids, the latter's response was better. Also among the different media culture, it is seen that the growth of mature embryo in the liquid media was better than solid.

Key word: Cotton, diploid species, tetraploid species, hybrid, media culture.