Postharvest tomato fruits are cold-sensitive, and easy to develop chilling injury (CI) at cold storage. Information on physiological and genetic characteristics closely related to CI is necessary because it is significant to realize CI development regular and find sensitive indicators reflecting cultivar cold tolerance, which are the basics to prevent CI. In this study, we used 2 tomato cultivars (Lichun and Santiam) differing in cold tolerance to analyze ion leakage, malondialdehyde (MDA), proline, catalase (CAT), and peroxidase (POD) in postharvest fruits chilled at cold storage. Expression of cold-response gene LeCBF1, a key regulator in cold-response, was also detected. Results showed that ion leakage, with a high correlation coefficient (0.9661) to CI index, exactly reflected injury development phase and degree; sharp increase of MDA and proline content appeared at and before the time of main development phase of CI (10 d); however, fluctuant CAT and POD activities could not sensitively reflect CI development, since their regular changes didn't appear until the main development phase ended. Thus, ion leakage, MDA, and proline content were effective indicators for CI analysis in postharvest tomato fruits. Although physiological analysis was effective in CI analysis, it was complex to be used in judging cold tolerance. Expression of LeCBF1 gene swiftly responded to low temperature within 1 h. In accordance with those physiological parameters, LeCBF1 expression level was positively correlated with cold tolerance and showed a high correlation to CI index (-0.9176). These suggested that LeCBF1 analysis could be effectively used in fast testing the cold tolerance of tomato.

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Edited by Ulf-Ingo FlüggeKeywords: Tomato Postharvest fruit Cold tolerance Cold storage Lycopersicon esculentum putative transcriptional activator CBF1 a b s t r a c t C-Repeat/dehydration-responsive element binding factor (CBF) is a transcription factor regulating cold response in plants, of which little is known in fruits. We showed a double-peak expression pattern of Lycopersicon esculentum putative transcriptional activator CBF1 (LeCBF1) in mature green fruit. The peaks appeared at 2 and 16 h after subjection to cold storage (2°C). The second peak was coincident with, and thus caused by a peak in endogenous ethylene production. We showed that LeCBF1 expression was regulated by exogenous ethylene and 1-methylcyclopropene, and was not expressed without cold induction. LeCBF1 expression was different in the five maturation stages of fruits, but expression peaked at 2 h at all stages.

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