Hatching Characteristics And Diapause Mechanism Of Heterodera Glycines

In this paper, distribution and dynamics of soybean cyst nematode (SCN, Heterodera glycines, race 4) in the root of soybean during the period of 7~37 d after seedling emergence in 2006 and 2007; effect of temperature on diapause termination and induction, hatch rate and metabolites of Heterodera glycines in one year; comparation of hatch and metabolic substance on white and brown cysts were studied systematically. The results were as follows:1. Distribution and dynamics of soybean cyst nematodeDistribution of SCN population was closely related to growth of root. Nematode density and nematode population increased with the growth of soybean root, the fluctuation of nematodes per cm root showed a sigmoid curve, J2 was a dominant group in whole root or roots in different soil layer, J3 and J4 were the second. The nematodes per cm root in taproot and lateral root changes showed inverse trend with the age of seedling, and density of nematodes in taproot had a declining trend, while nematodes density of lateral root increased to a stable value. Difference of nematodes density between taproot and lateral root decreased with the soil layer deepening, most of the nematodes distributed in root of 5~15 cm soil depths during the soybean seedling stage, especially distributed in lateral root.2. Hatching dynamics of Heterodera glycines during one yearInfluencing factor of hatch from eggs included cysts of different stages, temperature and soybean phenophase. In March, hatch rate enhanced with the increase of temperature. Hatch rate of new formed cysts was high during the primary and middle growth stage of soybean, the hatch rate was very low at late growth stage of soybean.3. Effects of temperature on diapause terminationLow temperature could break diapause effectively, and some time was necessary. Hatch preference temperature could also break diapause, however, diapause status recovered when the cysts were transmitted at low temperature (4℃) for a period.4 Effects of temperature on diapause inductionDiapause of Heterodera glycines was induced by 35℃and thermoperiod of CT12:12 (14℃:35℃) treatment; a small portion of eggs enter diapause by 14℃treatment. Thermoperiod of CT12:12(14℃:28℃) treatment could break diapause.5 Comparation of hatching and metabolic substance between white and brown cystsThere were J2 hatching from both white and brown cysts, the hatch rate of white cysts was higher than that of brown cysts. The glycogen and protein content and esterase activity in brown cyst were lower than that of white cyst, while content of total carbohydrate and trehalose and trehalase activity in brown cyst was higher. Therefore, diapause rate of brown cysts was higher than that of white cysts, and active mutual transformation between trehalose and glycogen existed in brown cysts. SDS-PAGE pattern showed that there were 15 and 10 protein bands in white and brown cysts respectively, and molecular weight 116.6,79.1,68.2,64.3 and 60.5 KDa proteins existed in white cysts, and without in brown cysts. There were 3 and 6 bands in patterns of esterase isoenzyme in white and brown cysts respectively, EST0.63, EST0.75 and EST0.81 of esterase isoenzyme occurred in brown cysts, and not in white cysts. The result suggested that content of protein declined, and activity of esterase was increased when the white cyst turned into the brown cyst. And it could speculate that low hatch rate of eggs in brown cysts might be related to those metabolites.6. The relationship between metabolites and diapauseTotal carbohydrate content was influenced by nematode diapause and temperature. Both of trehalose and glycerol content were influenced by nematode diapause and environmental temperature. The change of trehalose, glycerol content and diapause rate showed similar trend, however, the content increased with temperature decreasing. The content of glycerol changed with seasonal variation, which was low in spring and early summer relatively, absolute content of glycerol could not reflect nematode diapause rate.Content of soluble Protein and glycogen were influenced by temperature, soybean pheophase and diapause rate. The diapause rate was high at the absent of the host, soluble protein and glycogen content were high. The diapause rate was low during growth stage, soluble protein and glycogen content were low. The diapause termination experiment showed that low temperature played an important role in increasing of soluble protein content. Diapause induction experiment indicated that glycogen accumulated with temperature increase, while glycogen content decreased for glycogen transformation, and trehalose increased with temperature decreasing.The changes of diapause rate and esterase activity displayed contrary. Trehalase activity was affected by trehalose concentration and diapause rate, change of esterase activity in one year displayed a pattern of high-low-high-low-high.There was great difference in esterase activity and isoenzyme patterns in different month and development stages. In order to identify physiological race accurately and correctly, isoenzyme bank was needed; so did selection of the same time and development stage.