Abstract:

To clarify the mechanism of fruit hardness difference among different papaya lines, and provide new ideas for quality control, storage and preservation of postharvest papaya, two superior papaya lines‘Huanghy’ (‘HHY’) and ‘Jinchui’ (‘JC’) with the same genetic background were used as materials. The quality, storage characteristics, and the transcriptome sequencing data of the two lines during storage were observed, counted, and analyzed. The results showed that the water loss rate of ‘HHY’ was higher than that of ‘JC’, and the time of peel shrinkage and pulp cell expansion of ‘HHY’ were earlier than that of ‘JC’. During 12 days of postharvest storage, the fruit hardness of ‘JC’ was significantly higher than that of ‘HHY’. The soluble solids of ‘HHY’ and ‘JC’ reached the peak value on 7^th day and 10-12^th day of storage, respectively, and both of them had better fruit quality. Transcriptome analysis showed that the differentially expressed genes of ‘HHY’ and ‘JC’ during postharvest storage were obviously enriched in the ethylene pathway, and the ethylene synthesis and signal activation of ‘HHY’ were earlier than ‘JC’. The results of quantitative real-time PCR (qRT-PCR) were consistent with the transcriptome results. The detection result of ethylene content was also consistent with the results of differential gene expression, fruit hardness change and edible time. The ‘JC’ fruit could be softened normally by ethephon treatment. Both ‘HHY’ and ‘JC’ superior papaya lines have better fruit quality. The difference in fruit hardness between the two superior lines is closely related to ethylene signaling pathway. ‘HHY’ is suitable for sale within a week of storage, while ‘JC’ fruit has high hardness, is suitable for long-distance transportation, and has better application potential.

Key words: Carica papaya, fruit hardness, storage, transcriptome analysis, ethylene