柑桔不同晚熟品种（系）的抗寒性测试分析

晚熟品种需要挂果通过冬季低温时段，抗耐寒性是其重要特性之一。对经过前期低温锻炼的一年生春梢叶片在5个不同低温条件下的相对电导率进行测试，建立Logistic回归方程，本研究对目前生产上大量推广和新选育的不同晚熟品种（系）及少量中熟对照品种的抗耐寒性进行了分析。结果发现参试品种的相对电导率一般随着温度的降低而增加，但变化的幅度在品种间存在明显差异，表明不同品种（系）对低温有不同反应；全部样品的平均半致死温度为-6.55℃，沙田柚和晚白柚的半致死温度最高，分别为-4.4℃和-5.2℃，可能最不耐寒，江安无核夏橙的半致死温度最低，为-8.5℃，在测试样品中最耐寒。

Characterization of cold-resistance of late-season citrus varieties or lines

The late-season citrus varieties need to pass through the low temperature period during winter time with fruits on. Cold resistance is an important trait of these varieties. Late-season citrus varieties or lines with a few midseason varieties as controls were tested for their cold resistance. Leaves of one year old spring shoots were treated at 5 low temperature gradients and the relative electric conductivity was tested. Semi-lethal low temperature was then estimated with Logistic equation. The relative electric conductivity increased with the decrease of temperature and the values were different in different varieties under same low temperature stress. Judged by the Semi-lethal low temperature, Shatianyou pummelo and Bampeiyu are very sensitive and Jiangan seedless valencia sweet orange is the most tolerant variety to low temperature stress among the tested genotypes.