Identification of cold resistance and resistance physiological response of eggplant germplasms for rootstock

【Objective】The purpose of this study is to explore the effects of low temperature on the physiology of eggplant seedlings for rootstock, select the germplasms with strong cold resistance, and to provide a reference for the breeding of cold tolerant rootstocks suitable for grafting cultivation of autumn and winter tomato in South China.【Method】Sixteen eggplant germplasms for rootstock were used as materials, and the low temperature treatment temperatures of 10, 15 and 20℃were set.The cold tolerance of eggplant germplasms for rootstock was evaluated according to germination index, chilling injury index and physiological index in the germonation and old temperature stress experiment.【Result】The low temperature of 10℃ significantly inhibited the germination of eggplant seeds for rootstock, and the germination rates were all less than 10.00% except that germination rate of J61 was 18.33%.There was no significant correlation among seed germination rate, germination index, germination potential and seedling chilling injury index(P> 0.05).The seedling chilling injury indexes of germplasm BC05 and J13 were 0.16, 0.20 respectively, showing high resistance(HR) to low temperature.The seedling chilling injury indexes of germplasm BC06, J60, AQ and A were 0.27-0.40, which showed moderate resistance(MR) to low temperature.The chilling injury index of 8 germplasms such as BC01, BC02 and BC03 ranged from 0.40-0.56, which showed resistance(R) to low temperature.Under low temperature stress at 10℃, the chlorophyll content of the tested germplasm seedlings decreased, while the conductivity, malondialdehyde(MDA) and proline(Pro) contents increased, and the activities of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) increased, but the response degree of different germplasms were different.The chilling injury index of seedlings was extremely significantly(P< 0.01, the same below) or significantly(P< 0.05, the same below) positively correlated with the change rate of chlorophyll content and MDA content.It was significantly or extremely significantly negatively correlated with the change rate of Pro content, activities of SOD, POD and CAT, respectively.The subordinate function value of the low temperature resistance of the tested germplasms were analyzed.The above six germplasm with HR and MR were ranked in the top six for their comprehensive low temperature resistance.And the above six germplasms were classified as high resistance to low temperature or resistance to low temperature by cluster analysis.【Conclusion】The index of seed germination should not be used as the identification index of cold tolerance of eggplant for rootstock.The seedlings chilling injury index, chlorophyll, MDA and Pro contents, SOD, POD and CAT activities can be used as the identification indexes of cold tolerance.The results of comprehensive evaluation show that BC05, J13, BC06, J60, AQ and A have high resistance to low temperature.And above six gemplasms can be used as backbone germplasm materials for breeding new varieties of cold-tolerant rootstocks.