Induction of new tetraploid genotypes and heat tolerance assessment in Asparagus officinalis L

Abstract Tetraploid induction is an effective way to generate new genotypes. In this study, tetraploid inductions of asparagus (Asparagus officinalis L.) were obtained by applying several treatments with colchicine. Optimal results (31 %) were obtained by applying 0.15 % colchicine plus 2 % dimethyl sulphoxide (DMSO) to recently germinated seeds (5 days old) for 16 h. Sixty-five tetraploid plants were recovered from this treatment and diploid and tetraploid plants showed significant differences in morphology. The stomatal density of tetraploid asparagus was approximately half than that of diploid plants, whereas the chloroplast number of tetraploid plants was twice that of diploid plants; moreover, the stomatal length and breadth were slightly larger in tetraploid plants than in diploid plants. Furthermore, in tetraploid genotypes the chlorophyl A content was double than that of diploid plants, whereas chlorophyl B and total chlorophyl contents were three times higher than in diploid plants. The tetraploid plants showed better growth, more flowering flourish, deeper color, and bulkier leaves in comparison to the diploid plants. Moreover, tetraploid plants had lower malonaldehyde (MDA) and higher activity of superoxide dismutase (SOD), peroxidase (POD) and free proline (Pro), the differences were all significant, indicating that tetraploid plants had increased heat resistance however there was no significant difference in the heat tolerance between plants of the same ploidy. Tetraploid plants with strong heat resistance broaden the asparagus gene pool and could aid future breeding work in asparagus.