关键词: 亚洲小车蝗, 小分子糖醇, 氨基酸, 抗寒性, 低温驯化

Abstract: 【Objective】 The band-winged grasshopper, Oedaleus asiaticus Bei-Bienko, is one of the most dominant and economically important grasshopper species in the steppe grasslands and farming-pastoral ecotone in northern China. This grasshopper is an univoltine species and overwinters as eggs in soil. The supercooling points and the contents of low molecular sugars and polyols, and amino acids in its eggs were examined at different developmental stages for understanding of the physiological and biochemical mechanisms on its cold hardiness.【Method】Adult grasshoppers were collected from the Gegentala grassland, Siziwang Flag, and put into the oviposition cages and reared on fresh corn leaves. Egg pods were collected daily and put into plastic cups filled with soil, which were incubated at 25℃ to obtain the eggs in different developmental durations. Meanwhile, some egg pods were put into an incubator after oviposition and acclimated at 0℃ to get the eggs with different acclimation times. The supercooling points were measured by thermocouple method. Low molecular sugars and polyols, and amino acids were quantified by using high performance liquid chromatograph (HPLC) and automatic amino acid analyzer, respectively.【Result】 The supercooling points decreased gradually and the total contents of amino acids did not change significantly whereas the contents of low molecular sugars and polyols changed significantly along with the egg development at 25℃ from the first day to 120 d after oviposition. Seventeen amino acids were found, among which glutamate content was the highest (7.20-8.35 mg?100 mg^-1), followed by aspartic acid, leucine, praline, tyrosine, valine and alanine, cystine and methionine was the least (0.51-0.88 mg?100 mg^-1). The supercooling points had negative correlations with the contents of praline, alanine and glycine, whereas positive correlations with those of aspartic acid, cystine and leucine. All six kinds of low molecular sugars and polyols were detected and their contents were significantly different among different developmental stages. Glycerol was the most (56.14-160.00 μg·g^-1), secondly trehalose (13.60-51.13 μg·g^-1) and sorbitol (3.14-72.30 μg·g^-1), thirdly myo-inositol (3.19-22.15 μg·g^-1) and glucose (3.59-25.40 μg·g^-1), and fructose was the least (1.28-11.33 μg·g^-1). With the egg development, the contents of trehalose, glycerol, myo-inositol and sorbitol increased whereas glucose content decreased, and fructose content rose from oviposition to 90 d after oviposition and declined sharply 120 d after oviposition. There were significant negative correlations between the supercooling points and the contents of trehalose, glycerol, myo-inositol and sorbitol whereas a positive correlation with glucose content except fructose. The supercooling points of acclimated eggs after exposure to 0℃ for 30 d were not significantly different from those of non-acclimated eggs but significantly decreased 1.28℃ after exposure to 0℃ for 60 d, and glycerol content increased by 43.01% while glucose content declined by 73.54%. After exposure to 0℃ for 90 d, the supercooling points of acclimated eggs declined by 2.15℃, and the contents of glycerol and myo-inositol were significantly more than the control, increased by 43.39% and 36.18%, respectively, and glucose content decreased by 87.98%. Cold acclimation did not affect significantly the contents of trehalose, sorbitol and fructose.【Conclusion】With the egg development, the contents of four low molecular sugars and polyols (trehalose, glycerol, myo-inositol and sorbitol) and three amino acids (praline, alanine and glycine) rose, and the supercooling capacity increased. Cold acclimation induced the contents of glycerol and myo-inositol in eggs to increase significantly, and promoted their supercooling capacity.

Key words: Oedaleus asiaticus, low molecular sugar and polyol, amino acid, cold hardiness, cold acclimation