Evaluation of cryopreservation strategies in sugarcane true seeds using Kaplan-Meier survival analysis

BACKGROUND: Cryopreservation offers a robust approach for the long-term conservation of sugarcane ( Saccharum spp .) germplasm, particularly for maintaining the viability of true seeds used in hybridization programs. According to conservation biology, any plant part capable of regenerating a whole plant can be conserved. However, the effectiveness of cryogenic treatments in preserving sugarcane true seeds requires systematic evaluation. OBJECTIVE: To evaluate the survival dynamics of five sugarcane genotypes under different cryogenic treatments and to determine the efficacy of silica gel dehydration combined with liquid nitrogen exposure in enhancing cryo-tolerance. MATERIALS AND METHODS: Five sugarcane genotypes (Co 1148, 1148-13-11-2-255, CoSe 92423, CoM 9217, and LG 07590) were subjected to four storage treatments: (i) silica gel dehydration followed by liquid nitrogen (Si+LN+), (ii) direct liquid nitrogen storage without dehydration (Si−LN+), (iii) low-temperature storage at −23 °C, and (iv) non-cryogenic control. Survival probabilities over 21 days were analyzed using the Kaplan–Meier method with NCSS software. Survival functions were compared across treatments using logrank tests. RESULTS: Across genotypes, Si+LN+ consistently showed the highest survival probabilities over a short-term poststorage assessment duration. Survival curves under Si+LN+ significantly differed from controls and low-temperature treatments (p < 0.001). Among the genotypes, Co 1148 and 1148-13-11-2-255 exhibited the greatest cryo-tolerance, maintaining survival >40% after 21 days, whereas CoM 9217 was the most sensitive. Incorporation of silica gel dehydration effectively mitigated cryo-injury during liquid nitrogen exposure. CONCLUSION: Kaplan–Meier survival analysis provided detailed temporal insights into treatment–genotype interactions, offering more robust statistical evaluation than endpoint germination alone. The findings emphasize the utility of silica gel dehydration in enhancing cryogenic survival and highlight the Si+LN+ protocol as optimal for conserving sugarcane reproductive viability in germplasm conservation programs. The controls maintained higher survival only over the short experimental timeframe, whereas cryopreserved seeds are intended for indefinite storage without genetic or physiological deterioration.