Seed cryopreservation as an alternative for the conservation of H. sabdariffa L. (Malvaceae) germplasm

Hibiscus sabdariffa L. (Malvaceae) is a species widely exploited for cooking, ornamental and medicinal purposes, which justifies the efforts for its maintenance and conservation. The objective of this study was to establish a cryopreservation protocol for the conservation of H. sabdariffa seeds. The success of cryopreservation was investigated by the evaluation of seed moisture content (MC%) and, subsequently, germination percentage (G%), germination speed index (GSI), formation of normal seedlings (NS%) with histological comparison and survival at the end of acclimatization. The responses of the explants to in vitro multiplication were verified by the quantification of shoots, rooting percentage and seedling survival at the end of acclimatization. The experimental design was completely randomized, evaluating the effect of mechanical scarification, desiccation in silica gel for different periods (0, 1, 2, 4 and 8 h) and cryopreservation. Seed MC% was 11.1%. The lowest MC% was found in the treatment with seeds scarified and desiccated for 8 h with 6.9%. All treatments showed more than 70% G% and there was no significant difference for GSI, which suggests a positive effect for the cryopreservation process. However, desiccation significantly reduced NS%. By the histological comparison of normal and abnormal seedling stalks, it was possible to verify tissue disorganization, when it was submitted to desiccation. There was 94% survival of normal seedlings from cryopreserved seeds. In addition, each explant yielded 3.1 shoots, with 93% rooting and 100% seedling survival of H. sabdariffa after acclimatization. Therefore, seed cryopreservation can be considered an efficient alternative for the conservation of H. sabdariffa germplasm for long periods, without the use of cryoprotectants, scarification or desiccation.