Optimization Of Artificial Diets And Their Effect On Expression Of TOR Gene In Bactrocera Dorsalis

The oriental fruit fly, Bactrocera dorsalis, which causes great damage tofruits and vegetables, is an important invasive insect pest with a wide host range.Adult females insert their eggs beneath the skin of the hosts and the larvae damagethem through feeding and tunneling. The distribution of this insect will be broadenedin China due to the global climate warming. As the premise of biological control,artificial diet for rearing oriental fruit fly can not only obtain them with high qualitybut also meet the need for controlled operation and low cost. Rearing of fruit flies andits industrialization have been achieved outside China. Based on this background, thecurrent study employed the mixture design to determine the optimal proportions bothin larval diet and adult diet for oriental fruit fly. The larval diet with a starter phase forrearing this insect has also been studied. Furthermore, this study proved themechanism of nutrient regulation by studying TOR （target of rapamycin）, animportant gene involved in insect growth regulation. The results are summarized asfollows:1. Studies on optimizing larval diet for oriental fruit fly: The result showed thatthe three diet ingredients （sugar, yeast and wheat bran） can fit six modelssignificanctly including pupation rate, larval duration, pupal weight, sex ratio, numberof eggs per female and egg hatchability. Interactions among the ingredients werefound except for the model with number of eggs per female. The P value for lack offit is more than0.1and the value for Adeq Precision is more than4. Based on theparameters of R2, R2_adj, and R2_pred, the order of the correlations from high to low in sixmodels was determined to be: pupal weight, larval duration, pupation rate, number ofeggs per female, egg hatchability and sex ratio. The difference in the value among R2,R2_adj, R2_predis less than0.2in addition to sex ratio and egg hatchability. Five dietformulas were obtained through optimization procedures using software and two werechosen as good formulas considering the cost and performance. These formulascontain11.0%sugar,3.3%yeast and25.7%wheat bran; and12.1%sugar,3.0%yeast and24.9%wheat bran. The tests showed good results.2. A preliminary study in the larval diet with a starter phase for oriental fruit fly:The starter diet of carbohydrate, protein and lipid rich prolonged larval duration,which showed a positive effect on pupal weight. The result showed that L-Ⅲ was thebest larval diet for pupal production for medical applications. The starter phase means4days of rearing in a lipid rich diet before moved to a standard diet. Furthermore,those diets play different roles in sex ratio and fecundity. For number of eggs perfemale, the rich nutrient increased this parameter as the time prolonged and P-Ⅲ waschosen as an optimal way for production expansion with overall consideration of thenumber of eggs per female and egg hatchability, which means4days of rearing in aprotein rich diet before moved to a standard diet. Also, L-Ⅲ was regarded as a goodway for SIT use with overall consideration of sex ratio and fertilized eggs per female.3. Studies on optimizing adult diet for oriental fruit fly: The result showed thatthree diet ingredients （sugar, yeast and soybean protein） can well fit four modelsincluding the number of eggs per female, fertilized eggs per female, survival rate ofmale, and survival rate of female. Interactions among those ingredients were foundexcept for the model for survival rate of female. The P value for lack of fit is morethan0.1and the value for Adeq Precision is more than4. Based on the R2, R2_adj, andR2_predvalues the order of the correlations from high to low in four models wasdetermined to benumber of fertilized eggs per female, number of eggs per female,survival rate of female, and survival rate of male. The difference in the value amongR2, R2_adj, and R2_predis less than0.2in addition to survival rate of female and survivalrate of male. Two diet formulas were obtained through software optimizing measuresand two were regarded as optimal formulas considering the cost and performance.The optimal proportions include53.6%sugar,12.6%yeast and33.8%soybeanprotein wheat bran; and50%sugar,15.7%yeast and34.5%soybean protein. Thetests showed good results.4. Effect of diets on expression of TOR for oriental fruit fly: It showed that therelative expression of TOR for larvae, pupae and adults of oriental fruit fly reared onartificial diet was higher than that when the insects were reared on banana diet. Alldata have reached significant level （P=0.05） expect for that of pupae. However, the expression of TOR for the pupae of oriental fruit fly reared on the same diet wassignificantly higher than the expression for other stages. Furthermore, the relativeexpression of TOR for the abdomen of female reared on protein rich diet wasssignificantly higher than that when the insects were reared on carbohydrate rich dietbut this have not found in the abdomen of male.