Study On The Constitutive Resistance And Evaluation Model Of Tea Plant To Two Sap-sucking Pests

Camellia sinensis(L.)O.Kuntze belongs to the genus Camellia in Theaceae,which is a leafy cash crop.During the growth of tea plant,it is susceptible to the main piercing-sucking pests,such as Matsumurasca onukii(Hemiptera,Cicadellidae)and Dendrothrips minowai Priesner(Thysanoptera,Thripidae).The insects feed on the sap of young shoots,causing stunted growth and thus affecting the quality and yield of tea leaves.During the long-term synergistic evolution of insects and plants,the resistance of pests has gradually increased,making it difficult for chemical control to be effective.The selection of insect-resistant varieties is one of the most effective and economical strategies to combat insect pests by exploiting genetic traits fundamentally.In this study,different tea cultivars in the same habitat were used as materials for field experiments and indoor validation experiments to initially investigate the composition of the resistance of tea cultivars to two sap-sucking pests,and to construct a comprehensive evaluation model for resistance of tea cultivars and develop a grading standard for resistance of tea cultivars,with a view to providing a theoretical basis for tea tree cultivation and breeding and pest control.The main results are as follows:1.Identification of resistance levels of different tea tree varieties to two sap-sucking pestsThe results of field population density surveys for two consecutive years were used to identify the resistance levels of different tea cultivars.Indoor hatching tests on field branches and indoor determination of vital parameters supported the reliability of using field population density as a resistance grading standard for two sap-sucking pests,which can effectively reflect the degree of resistance.Eventually,the resistance of tea cultivars to M.onukii was divided into four classes,Class I: ZJ,susceptible(S);Class II: MZ,moderately susceptible(MS);Class III: FJSX,HD,BYQL,BMD,DHP,RX,moderately resistant(MR);and Class IV: HGY,HMG,BJG,resistant(R).The resistance levels of tea cultivars to D.minowai Priesner were also divided into four categories,category I: HMG,susceptible(S);category II:BJG,RX,moderately susceptible(MS);category III: BYQL,HGY,moderately resistant(MR);and category IV: BMD,HD,DHO,ZJ,MZ,FJSX,resistant(R).The temporal ecological niches of the two pests were also analysed,and it was found that the temporal ecological niches of the two sap-sucking pests overlapped highly in the same habitat,with D.minowai Priesner having a greater population advantage than M.onukii.2.Host locus selection resistance of tea trees to two sap-sucking pestsA solid phase microextraction(SPME-GC-MS)method was used to identify the volatiles of 11 new shoots and leaves of tea trees with different levels of resistance to the insect.The results showed that tea cultivars with higher relative content of volatiles were less resistant to M.onukii.Alcohol and alkane volatiles,mainly involved in influencing the selection of tea tree hosts by the two sap-sucking pests,were followed by aldehydes.The lower the linalool content,the higher the nonanal and dodecane content,the more resistant the tea cultivars to M.onukii,and the lower the dodecane and phenylethanol content,the more resistant D.minowai Priesner.It is assumed that linalool has a luring activity for D.minowai Priesner,while nonanal and dodecane have a tending or poisoning effect on M.onukii.Dodecane and phenylethanol have a luring effect on D.minowai Priesner;"dodecane" has the opposite effect on M.onukii and D.minowai Priesner.3.Physical resistance of tea trees to two sap-sucking pestsThe botanical traits,leaf colour difference,leaf flesh tissue structure and waxy layer per unit leaf area of different insect-resistant tea tree species were investigated and measured.The results showed that the thicker the upper epidermal thickness,the greater the ratio of upper epidermal thickness/leaf thickness,the smaller the ratio of upper cuticle thickness/leaf thickness and lower cuticle thickness/leaf thickness,the more resistant the tea cultivars were to M.onukii,the lower the values of colour difference brightness(L*),yellow-blueness(b*),colour dispatch(Cab),colour saturation(Sab)and the longer the leaves,the larger the leaf area and the more velvety the leaves.The longer the leaf blade,The longer the leaf blade and the larger the leaf area,the more resistant to D.minowai Priesner.And D.minowai Priesner is more concerned with the colour of the back of the leaf.4.Chemical resistance of tea trees to two sap-sucking pestsThe content of three chemical substances,namely primary metabolites,secondary metabolites and enzyme activities,was measured in different resistant tea cultivars,and the preliminary screening showed that the GCG in the catechin fraction,anthocyanin in the pigment fraction and MDA in the enzyme activities were significantly and positively correlated with the population density of M.onukii.It was found that the survival rate and life span of M.onukii decreased as the GCG content increased in the artificial diet,while anthocyanins had no significant effect on the growth and development of M.onukii.It is suggested that anthocyanins may not be directly involved as chemical substances in the resistance of tea trees to M.onukii,but rather as leaf colour synthesis substances that influence the selection of M.onukii as a host for tea cultivars.The insect stress induction test showed that the lower the change in MDA content in leaf tissue after24 h of leafhopper damage,the less damaged the tea tree was and the more resistant it was to the insect.There was a significant negative correlation between caffeine and the population density of D.minowai Priesner,with the higher the caffeine content of the tea cultivar,the more resistant it was to D.minowai Priesner.5.Development of a comprehensive resistance evaluation model and grading criteria for insect resistanceThe above resistance-related factors were combined to construct a comprehensive resistance evaluation model.Using the affiliation function method to calculate and validate the model,the comprehensive evaluation results were significantly and positively correlated with the population density,indicating that the evaluation data results were highly accurate and the model was reliable and of reference value.The model evaluation results were analysed together with the population density grading results,and the results showed that the three tea cultivars,Fujian Narcissus(FJSX),Dahongpao(DHP)and White Peony(BMD),all had strong resistance evaluations to the two sap-sucking pests and were worthy of being widely promoted for cultivation.This experiment also developed a preliminary grading standard for tea tree resistance to two sap-sucking pests,which will provide some reference value for tea cultivation and breeding.