Morphological, physiological, cytological characteristics and agricultural potential of colchicine induced autotetraploid plants in safflower

Abstract

Safflower (Carthamus tinctorius L.) is one of the important oilseed and bio-energy crops. All of the safflower cultivars in the world have diploid genomes (2n= 2x= 24). In this research, autotetraploidy induction in safflower was performed by colchicine treatments to the emerging shoot tips at the cotyledonary stage. As a result of flow cytometric analyses performed in the C2 progenies, autotetraploids (4x= 48) had DNA content of 4.88 pg 2C-1, while diploids (2x= 24) had 2.29 pg 2C-1. The autotetraploids in C2 generation exhibited bigger stomata size (33.40 μm to 46.90 μm in length) and a higher chloroplast number (9.5 to 17.2 in the guard cells), but less stomatal density (17.98% to 16.67% in index) compared to their diploid counterparts. However, autotetraploidy reduced the pollen viability from 80.24% to 16.20%, and seed set rate from 35.06% to 7.01% per capitula. As a result, autotetraploid plants were able to produce very few seeds despite the high unit seed size and weight in their heads. While oil content of the large-seeded autotetraploids was significantly lower, by two-fold, (26.37% to 13.23% in the whole seeds) than the small-seeded diploids, fatty acid composition was not significantly influenced by autopolyploidization.