Differences In Adaptability Of B And Q Biotypes Bemisia Tabaci To Peppers

Plants have formed an array of effective defense systems against phytophagous insects in the long-term process of co-evolution with phytophagous insects.Induced defense,as an important part of pest resistance mechanism of plants,plays an important role in resisting pest insect.Wounds and elicitors secreted by pests during feeding can activate plant defense system.Induced resistance is usually characterized by a series of changes in the content of secondary metabolites in plants,which changes the physiological and biochemical characteristics of host plants and affects the feeding behavior of pests.Some studies have shown that plant-induced defense can not only resist the further damage of pests,but also produce asymmetric effects on subsequent feeding pests,thus realizing the interaction between different insect species mediated by plant-induced defense.Infecting a wide range of host plants,Bemisia tabaci Gennadius is an important complex species,which includes 36 cryptic species worldwide pest.It harms most agricultural and horticultural crops by directly feeding and indirectly spreading virus.Among the 36 cryptic species,the two highly invasive alien cryptic species,B and Q,have been increasingly taken seriously.Q biotype B.tabaci in China is gradually replacing the B biotype and becomes the dominant biotype in field.Bemisia tabaci is also one of the main pests of pepper plant in China,which can cause large-scale yield reduction or even stop production when the damage is serious.In the present study,four pepper varieties(Qianhong,Zhongjiao4,Hangjiao and Zhonghuahong)and two invasive biotypes(B and Q)B.tabaci were used as experimental materials to determine the contents of two main insect-resistant secondary metabolites(total phenols,flavonoids)and seven nutrients(total amino acid,free protein,total nitrogen,phosphorus,potassium,reducing sugar,total sugar)in pepper plants.Secondly,the host preferences of B and Q biotypes of B.tabaci for feeding and oviposition on four pepper varieties were studied.Finally,the effects of pre-infested peppers by B and Q biotypes on hostchoice and performance of subsequent of B.tabaci were studied.The main results are showed as following:1.According to the determination results of insect-resistant compounds and nutrient content in four varieties peppers,it was found that total phenols and flavonoids content were markedly higher for Zhonghuahong than for other three varieties peppers.The nutrient content in Zhonghuahong is relatively lower than other three varieties peppers.Total phenols contents was markedly lower for Zhongjiao4 than for other three varieties peppers.Free protein,total amino acid and phosphorus were markedly higher than other three varieties peppers.In the experiment of preference for feeding and oviposition of B and Q biotypes of Bemisia tabaci among four varieties peppers,it was found that B preferred the low-quality Zhonghuahong,but Q showed no preference among the four varieties.2.Comparing the changes of main defensive substances and nutrient contents in the peppers caused by the infection of B and Q B.tabaci,it was found that there are significant differences in total phenol content among three treatments peppers.The infection of B significantly increased the total phenolics content of the pepper,but not in the pepper infested by Q.3.B preferred to feed and lay eggs on peppers which previously infected by Q,but avoided feeding and laying eggs on peppers which previously infected by B.Q tended to feed on intact peppers,but avoided laying eggs on peppers which previously infected by B.4.The survival rate of B on Hangjiao which previously infected by Q was highest.The survival rate of Q on Hangjiao which previously infected by Q was significantly higher than that Hangjiao which previously infected by B and the intact peppers.However,there was no significant difference between B and Q biotypes in the average eggs and the ratio of development from eggs to adults on three different treatments of Hangjiao.In conclusion,B biotype B.tabaci is more sensitive to pepper varieties and plant-induced defense.At the same time,the feeding of B biotype B.tabaci deteriorated host quality,which was detrimental to the growth and reproduction of subsequent intraspecific individuals.However,the Q biotype B.tabaci is insensitive to pepper varieties,it has stronger adaptability and is not susceptible to plant-induced defense.In addition,feeding by Q B.tabaci can improve the performance of subsequent intraspecific individuals to feed on host plant.In the present study,the effects of biotic stress caused by of B and Q biotypes of B.tabaci on the physiological and biochemical characteristics of four varieties pepper were studied.The role of induced defense in the defense response of pepper to B.tabaci was determined.The differences of physiological adaptability of B and Q biotypes of B.tabaci to pepper pre-infected by homologous or interspecific B.tabaci were studied,too.From these studies,we can clarify the induced defense system of pepper in response to whitefly infestation and explore the resistance mechanism of pepper varieties to whitefly.These studies shown that Q B.tabaci may have more advantages in interaction with B B.tabaci in natural environment.It has offered theoretical support for plant-mediated interaction between phytophagous pests.These results provide theoretical basis for integrated pest management strategies,especially for utilization of plant-resistance crop breeding as main control tactic,so as to target different biotypes of B.tabaci on different host plants.