In vitro selection and identification of a cold-tolerant variant in pineapple (Ananas comosus)

Cold stress is an important factor limiting the growth and distribution of pineapple. Breeding cold-resistant germplasm is an effective way to cope with this problem. In vitro selection for the somaclonal variation using different selection agents has been used for crop improvement in stress tolerance. In this study, the pineapple cold-tolerant variant was developed through in vitro cold selection of somaclonal variations. Low temperature was used as the selected agent, and the extreme lethal condition for the in vitro pineapple cultures was determined to be 0 degrees C for 72 h. The morphology changes of the in vitro cultures during the cold selection were observed and analyzed. The cold-tolerant variant line was finally obtained through three consecutive selections with cold shock treatments, based on the established high-efficiency culture system for pineapple embryogenic calli. The genetic variations at the molecular level in the cold-tolerant variant were verified by ISSR analysis. The significantly improved cold tolerance in our selected variant was mainly reflected by the higher survival rate, increased proline content, and elevated SOD activity under cold stress compared to these qualities in the control plants. This study demonstrated the feasibility of in vitro selection for cold tolerance in pineapple. The cold-tolerant variant could be valuable for future pineapple breeding programs and for cold tolerance research.