Study On Population Dynamics Of Aleurocanthus Spiniferus Quaintance And Effects Of Citrus Varieties On A. Spiniferus

Chongqing is one of main production bases of citrus fruit in China. In recent years, with the increasing development of the citrus fruit production, the damage of pest insects and diseases become more and more serious, especially of Aleurocanthus spiniferus Quaintance with its growing resistance and unique biological characteristics. In this study, the annual population dynamics of A. spiniferus in citrus yard was investigated firstly, and the effects of citrus varieties on activities of carboxylesterase (CarE), acetylcholineesterase (AChE) and Glutathione S-transferases (GSTs) in A. spiniferus were comparatively studied via the method of microplate reader. Besides, the nutrients difference of citrus leaf among different citrus varieties was also compared. The study would provide a useful reference for the integrated management on citrus. The main results were as follows:1 Natural population dynamics of Aleurocanthus spiniferus in citrus yardThe natural population dynamics of A. spiniferus through a whole year of field investigation was conducted. The result indicated that the population quantity of the insect amounted to peak in early July. Among different indices of aggregation, lga>0, b>1, k<1, I>0, and C_A>0. This indicated that the spatial distribution pattern of A. spiniferus in citrus yard belonged to aggregate distribution and the situation was the outcome of interaction effects between the insect and external environmental factors. Applying Taylor's power law model, the optimal number of theoretical sampling was obtained:n= (1/D) 2^*17.4984^*M^-0.2649; however, when with Iwao theoretical sampling method, the optimal number of theoretical sampling model was n= (1/D)2^*(2.9469/M+15.9969).2 The Effects of citrus varieties on activities of AChE, CarE and GSTs in A. spiniferus2.1 The Effects of citrus varieties on activities of AChE in A. spiniferusAChE is a key enzyme that terminates nerve impulses by catalysing the hydrolysis of the neurotransmitter acetylcholine in the nervous system. In order to clarify the role of AChE of A. spiniferus to pesticide susceptibility, the activities of AChE in A. spiniferus fed with different citrus varieties were determined via the microplate reader method. The results showed that the activity sequence of AChE from lowest to highest was Yanxiwanlu ponkan< Nankou< Katsuyama lyo kan< Miyawuchi lyo kan< Summer gold< Ponkan varieties nucellar line 3< Washington Sanguine< Shinanui< Tarocco blood orange. Significant difference of AChE activity existed among A. spiniferus on various citrus varieties. Among the nine tested citrus varieties, the AChE activity of A. spiniferus fed on Tarocco blood orange was highest,12.84 fold of that on Yanxiwanlu ponkan (p< 0.05).2.2 The Effects of citrus varieties on activities of CarE in A. spiniferus CarE is one of important detoxifying enzymes in arthropods and plays an essential role in resistance development of arthropods. In order to clarify the roles of CarE of A. spiniferus to pesticide susceptibility, the activities of CarE in A. spiniferus fed with different citrus varieties were determined via the microplate reader method. The results showed that the activity sequence of CarE in A. spiniferus from lowest to highest was Summer gold< Katsuyama lyo kan< Ponkan varieties nucellar line 3< Nankou< Miyawuchi lyo kan< Yanxiwanlu ponkan< Shinanui< Washington Sanguine< Tarocco blood orange. Significant difference of CarE activity existed among A. spiniferus on various citrus varieties. Among the nine tested citrus varieties, the CarE activity of A. spiniferus fed on Tarocco blood orange was highest,4.58 fold of that on Summer gold (p< 0.05).2.3 The Effects of citrus varieties on activities of GSTs in A. spiniferusGSTs, widely distributed in insects, can metabolize foreign compounds by facilitating their reductive dehydrochlorination or by conjugation reactions with reduced glutathione, to produce water-soluble metabolites that are more readily excreted. In order to clarify the role of GSTs of A. spiniferus to pesticide susceptibility, the activities of GSTs in A. spiniferus fed with different citrus varieties were determined via the microplate reader method. The results showed that the activities of GSTs in A. spiniferus from lowest to highest were:Nankou< Yanxiwanlu ponkan< Miyawuchi lyo kan< Shinanui< Washington Sanguine< Summer gold< Katsuyama lyo kan< Tarocco blood orange< Ponkan varieties nucellar line 3. Significant difference of GSTs activity existed among A. spiniferus on various citrus varieties. Among the nine tested citrus varieties, the GSTs activities of A. spiniferus fed on Ponkan varieties nucellar line 3 were highest,5.56 fold of that on Nankou (p< 0.05).3 Nutrients comparison of plant leaf from different citrus varieties3.1 Water content comparison of plant leaf from different citrus varietiesThe water content of host plants leaf was very important to insect. In order to clarify the roles of water content to A. spiniferus, the content of water in different citrus varieties were determined via the sample drying method. The results showed that the water content in different citrus varieties from lowest to highest was Yanxiwanlu ponkan< Katsuyama lyo kan< Summer gold< Miyawuchi lyo kan< Washington Sanguine< Nankou< Ponkan varieties nucellar line 3< Tarocco blood orange< Shinanui. Among the nine tested citrus varieties, the water content of Shinanui leaf was highest,1.35 fold of that in Yanxiwanlu ponkan (p< 0.05).3.2 Soluble sugar content comparison of plant leaf from different citrus varietiesIn order to clarify the role of soluble sugar content to A. spiniferus, the content of soluble sugar in different citrus varieties were determined. The results showed that the soluble sugar content in different citrus varieties from lowest to highest was Summer gold< Washington Sanguine< Yanxiwanlu ponkan< Tarocco blood orange< Nankou< Katsuyama lyo kan< Ponkan varieties nucellar line 3< Miyawuchi lyo kan< Shinanui. Among the nine citrus varieties tested, the soluble sugar content of leaves of Shinanui was highest,3.36 fold of that from Summer gold (p< 0.05).3.3 Reducing sugar content comparison of plant leaf from different citrus varietiesIn order to clarify the role of reducing sugar content to A. spiniferus, the content of reducing sugar in different citrus varieties were determined. The results showed that the reducing sugar content in different citrus varieties from lowest to highest was Nankou< Katsuyama lyo kan< Tarocco blood orange< Shinanui< Miyawuchi lyo kan< Washington Sanguine< Summer gold< Ponkan varieties nucellar line 3< Yanxiwanlu ponkan. Among the nine tested citrus varieties, the reducing sugar content of leaves of Yanxiwanlu ponkan was highest,12.72 fold of that in Nankou (p< 0.05).3.4 Protein content comparison of plant leaf from different citrus varietiesIn order to clarify the role of protein content to A. spiniferus, the content of protein in different citrus varieties were determined. The results showed that the protein content in different citrus varieties from lowest to highest was Katsuyama lyo kan< Ponkan varieties nucellar line 3< Shinanui< Yanxiwanlu ponkan< Washington Sanguine< Summer gold< Nankou< Tarocco blood orange< Miyawuchi lyo kan. The results showed that significant difference of protein content existed on various citrus varieties. Among the nine tested citrus varieties, the protein content of leaves of Miyawuchi lyo kan was highest,1.74 fold of that in Katsuyama lyo kan (p< 0.05).3.5 Glutathione content comparison of plant leaf from different citrus varietiesIn order to clarify the role of glutathione content to A. spiniferus, the content of glutathione in different citrus varieties were determined. The results showed that the glutathione content in different citrus varieties from lowest to highest was:Washington Sanguine< Summer gold< Tarocco blood orange< Shinanui< Ponkan varieties nucellar line 3< Miyawuchi lyo kan< Katsuyama lyo kan< Yanxiwanlu ponkan< Nankou. The results showed that significant difference of glutathione content existed on various citrus varieties. Among the nine tested citrus varieties, the glutathione content of leaves of Nankou was highest,5.13 fold of that in Washington Sanguine (p< 0.05).