Evaluation of freezing tolerance in Actinidia germplasm based on relative electrolyte leakage

Abstract

Cold stress in winter can have a disastrous effect on kiwifruit yield and affect geographical distribution. However, freezing tolerance in Actinidia genotypes remains largely unknown. Here, we report changes in metabolite content and enzyme activity in the shoots of Actinidia genotypes exposed to low-temperature stress (− 5 °C, − 10 °C, − 15 °C, − 20 °C, − 25 °C and − 30 °C). Moreover, the relative electrolyte leakage method was used to evaluate the freezing tolerance of kiwifruit germplasm; 51 genotypes from 16 species of Actinidia were evaluated in total. The data revealed that relative electrolyte leakage, proline (Pro), soluble protein, and catalase (CAT) activity changed with different low temperatures. Results showed that among 16 species, A. kolomikta, A. polygama, and A. arguta had lower LT50 than other species. A. arguta, originating from the northeast of China, exhibited stronger freezing resistance than the ones from other places. There was little difference in freezing tolerance between A. chinensis and A. deliciosa. These findings provide new insights into the freezing tolerance ability and mechanisms of kiwifruit and further contribute to our understanding of the relationship between freezing tolerance and geographic distribution.