大豆食心虫越冬幼虫过冷却点及其体内小分子内含物分析
Analysis of supercooling point and low-molecular weight compounds in overwintering soybean pod borer Leguminivora glycinivorella larvae

为研究大豆食心虫Leguminivora glycinivorella越冬幼虫的过冷却能力和耐寒机制，采用模拟自然埋土法调查越冬幼虫的存活率，用热电偶法测定越冬前后不同深度土层的幼虫过冷却点，并通过气相色谱-质谱联用仪检测虫体小分子内含物含量。结果表明，大豆食心虫越冬幼虫自然种群存活率随所处土层深度加深而显著升高，地表、地表下3 cm和8 cm土层的越冬幼虫存活率分别为5.00%、51.14%和91.50%，土层对越冬幼虫起保护作用；按体重分组的越冬幼虫，在相同深度土层中其存活率随体重降低而升高，且大、小幼虫间存活率差异显著。越冬前结茧滞育的大、中、小幼虫过冷却点分别为-14.22、-16.30、-17.64℃，越冬后过冷却点降低，降低幅度随所处土层深度加深而减少。在越冬幼虫体内检测到海藻糖、葡萄糖和L-异亮氨酸等10种化合物，海藻糖平均相对含量最高，为60.55%，其次是葡萄糖，为1.68%。幼虫过冷却点与海藻糖相对含量呈极显著负相关，海藻糖对大豆食心虫越冬具有抗冻保护作用；除甘氨酸外其它7种氨基酸类化合物相对含量与幼虫过冷却点呈显著正相关，相关系数均超过0.6797。表明上述这些化合物含量的变化能够调节大豆食心虫的抗寒能力。
To study the supercooling capacity and the cold tolerant mechanisms of overwintering soybean pod borer Leguminivora glycinivorella larvae, methods of simulation of natural burying soil and thermo-couple were used respectively to investigate the survival rate (SR) of overwintering larvae and to detect supercooling point (SCP) of larvae in the different depths of soil before and after overwintering. Then gas chromatography and mass spectrometry was used to examine the amount of small molecular compounds in the larvae. The results showed that survival rate of the natural overwintering larva population increased significantly with soil depth, and the survival rates of the earth's surface, 3 cm and 8 cm soil layer were 5.00%, 51.14% and 91.50% respectively, which inferred that soil played the protective role for the overwintering larvae. In the same depth of soil layer, the survival rate of larvae grouped by weight increased significantly with the weight decreasing and the survival rate of heavy larvae was significant different with that of the light larvae. Before overwintering, SCPs of heavy, medium and light diapausing larvae with cocoons were -14.22, -16.30 and -16.30℃, respectively, while after overwintering, the SCPs decreased and the decreasing amplitude reduced with the increasing of soil depth, in which the overwintering larvae were located. Ten compounds including trehalose, glucose and L-leucine were detected in the body of overwintering larvae. Among them, relative amount of trehalose was the highest with 60.55%, and the second was glucose with 1.68%. Very significant negative correlation was observed between larvae SCP and the content of trehalose which inferred that trehalose had the cryoprotective effect on overwintering larvae. The significant positive correlations were found between larvae SCP and the relative amount of other seven kinds of amino acids except for glycine with the correlative coefficient over 0.6797. In a word, the relative amounts of the above mentioned small molecular compounds exhibited the regulation