Autotetraploid synthetic seeds of Ficus carica L. exhibit a superior cold acclimation system than their corresponding diploids

The current study compares the cold acclimation of microshoots of two cytotypes of Ficus carica (fig) encapsulated in 3% sodium alginate. The biometrical and some important physiochemical parameters were evaluated to determine the cold acclimation responses of both cytotypes’ synseeds. Results revealed 37.5% survival of autotetraploid synseeds in the 9th month of cold acclimation as compared to the death of all diploid synseeds. The survival rate of autotetraploid synseeds (87.5%) in the 6th month of conservation was significantly higher than that of their corresponding diploids (54.16%). Autotetraploid synseeds produced significantly lower amounts of stress indices such as H₂O₂ and MDA (53.7% and 31.7%, respectively) during the cold conservation period, particularly in the 6th month of conservation, than their corresponding diploids; which were accompanied by a lower ion leakage (49.75%) and a higher water content (8.34%) compared to their corresponding diploids. Furthermore, autotetraploid synseeds exhibited superior capability of accumulating cell osmolytes in the 6th month of conservation than their corresponding diploids, including higher contents up to 34.62% TSS, 73.78% proline, and 43.96% glycine betaine. The activity of two key antioxidant enzymes of CAT and APX was also significantly higher in autotetraploid synseeds up to 48.14% and 30.29% in the 6th month of conservation, respectively, than in their corresponding diploids. According to the findings, it could be concluded that the autotetraploid cytotype has significantly more tolerance to cold stress due to its superior cold acclimation strategies, mainly including the osmolytes accumulation and cell detoxification dependent on antioxidant enzymes, than their corresponding diploid cytotype.