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 °C 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 °C 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 °C, 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. 摘要 【目的】 探讨低温对砧用茄子幼苗生理的影响, 筛选出耐冷性强的种质, 为选育适合华南地区秋冬番茄嫁 接栽培的耐冷砧木提供参考依据。 【方法】 以16份砧用茄子种质为材料, 设置10、15和20 °C不同低温处理, 通过种子发 芽及幼苗低温胁迫试验, 根据发芽指标、冷害指数和生理指标鉴定评价砧用茄子种质的耐冷性。 【结果】10 °C低温明 显抑制砧用茄子种子萌发, 除J61的发芽率为18.33%外其余种质的发芽率均在10.00%以下, 种子发芽率、发芽指数、发芽势与幼苗冷害指数均无显著相关性 ( P>0.05)。种质BC05和J13的幼苗冷害指数分别为0.16和0.20,表现强耐低 温, 种质BC06、J60、AQ和A的幼苗冷害指数为0.27~0.40,表现中耐低温, BC01、BC02和BC03等8份种质的冷害指数为 0.40~0.56,表现耐低温。10 °C低温胁迫下, 幼苗叶绿素含量降低, 电导率、内'二醛(MDA)和脯氨酸(Pro)含量增高, 超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性增加, 不同种质的响应程度不同。幼苗冷害指 数分别与叶绿素含量、MDA含量的变化率呈极显著 ( P<0.01, 下同) 和显著 ( P<0.05,下同) 正相关, 与Pro含量及SOD、POD、CAT活性的变化率呈显著或极显著负相关。对供试种质的耐冷性进行隶属函数综合分析, 以上表现强耐低温、中耐低温的6份种质的综合耐冷性排序前6, 聚类分析将这6份种质归类为强耐低温类、耐低温类。 【结论】 种子发芽指 标不应作为砧用茄子耐冷性的鉴定指标, 幼苗冷害指数及叶绿素、MDA、Pro含量和SOD、POD、CAT活性6项生理指 标可作为耐冷性的鉴定指标。综合评价结果, BC05, J13, BC06, J60, AQ和A等6份种质耐冷性强, 可作为选育耐冷砧 木新品种的骨十种质材料加以利用。