The Factors Affecting Competitiveness Between B And Q Biotypes Of Bemisia Tabaci

Bemisia tabaci(Gennadius)is a piercing-sucking insect pest worldwide with a wide range of host plants and strong adaptability.The insect pest could transmit more than 200 plant viruses and causes damage to more than 1000 host plants.B.tabaci has at least 39 morphologically indistinguishable biotypes(cryptic species).Among the biotypes,B and Q biotypes are the most important invasive pests in China.A better understanding of the factors that affect the dynamics of B.tabaci populations may lead to more accurate prediction,and thus more effective control of B.tabaci.In addition to their own intrinsic genetic competitiveness,the population status and trends of B.tabaci B and Q biotypes are affected by many factors.Therefore,we have analyzed the environmental factors that affect the competitiveness of B.tabaci B and Q biotypes by monitoring B.tabaci biotypes in the field,and ecological and electrical penetration graph(EPG)techniques were used to compare the change of B.tabaci B and Q biotypes feeding behaviors on B.tabaci pre-infected plants and CCYV?infected plants in order to better understand the population dynamic and the factors involved in the competitiveness of B.tabaci B and Q biotypes,and provide new ideas for study the outbreak mechanism of B.tabaci and effective control methds.The results of this study are summarized as follows:(1)Population monitoring of B.tabaci B and Q bioytpes in Henan Province in 6 yearsWe have collected a total of 250 population samples of B.tabaci in different locations of Henan Province during 2012-2017.Among them,215 were pure Q biotype,2 were pure B biotype,and 33 were mixtures of B and Q biotypes.Among the populations with mixed B and Q biotypes,30 were Q biotype dominated(>50%),1 was B biotype dominated(>50%),and 2 were with equal abundance of both biotypes 50%).Through the dynamic monitoring of B.tabaci biotypes,we found that Q biotype was dominant in most locations of Henan Province,and B biotype only existed in the areas with less interference of external factors.(2)The effect of host plants on competitiveness between B and Q biotypesB.tabaci B and Q biotypes were introduced onto cotton or cucumber plants at1:1 ratio.B biotype showed the tendency to displace Q biotype on cotton and cucumber plants.The proportion increase of B biotype in a mixed population was mainly contributed by females,while the proportion decrease of Q biotype in a mixed population was mainly caused by declining in males on cotton plants.In comparison,the proportion increase of B biotype was contributed by both males and females in a mixed population,and similarly the proportion decreased of Q biotype was caused by reduction in both males and females on cucunber plants.(3)The effect of insecticides on the competitiveness between B and Q biotypesB.tabaci B and Q biotypes were introduced onto cotton and cucumber plants at the ratio of 1:1,respectively.The proportion of B and Q biotypes in the mixed population gradually differentiated after generations under insecticide of spirotetramat treatment.Q biotype has the tendency to displace B biotype on both cotton and cucumber plants.The proportion of Q biotype females increased in the mixed population after generations.On the other hand,the proportion of B biotype males and females decreased in the mixed population significantly on cotton plants.The proportion of Q biotype females reached 60.74%at the third generation in the mixed population.The increase of Q biotype was mainly contributed by increase in females on cucumber plants.(4)The effect of pre-infected host plants on the feeding behaviors of B and Q biotypesBased on the results of B and Q biotypes feeding behaviors on control and B.tabaci pre-infected plants recorded by EPG,we found that B.tabaci pre-infected plants caused changes in the feeding behavior of subsequent B.tabaci populations on cotton and cucumber plants.B biotype exhibited stronger feeding adaptability than Q biotype on pre-infected cotton plants.Both biotypes females exhibited stronger feeding adaptability than males on pre-infected cotton plants.B biotype exhibited less non-phloem probing on pre-infected cotton plants,whereas Q biotype had more non-phloem probing and phloem salivation on pre-infected cotton plants.B biotype males and females were more likely to probing and feeding on pre-infected cotton plants.However,Q biotype had more phloem salivation and sap ingestion on pre-infection cotton plants,and Q biotype females had more phloem sap ingestion than Q biotype males on B biotype pre-infection cotton plants.Both biotypes exhibited better feeding performance on pre-infected cucumber plants by themselves.Females exhibited better feeding adaptability than males on pre-infected cucumber plants.Specificallyr B and Q biotypes spent shorter time for non-probing and phloem salivation,and spent longer time for phloem sap ingestion.Males of both biotypes encountered more obstacles in probing and feeding on B biotype pre-inrected cucumber plants.Females of both biotypes exhibited the opposite feeding behaviors.B biotype females encountered fewer feeding obstacles,whereas Q biotype females encountered more feeding obstacles.Both males of both biotypes exhibited more non-phloem probing than females on pre-infected cucumber plants.Cucumber plants pre-infected by either one B.tabaci biotype produced disadvantageous effects on the feeding of a different biotype,such as increasing salivation time.(5)Effects of CC YV-infected plants on feeding behavior of B and Q biotypesCucurbit chlorotic yellows virus(CCYV)is a plant virus transmitted semipersistently by B.tabaci B and Q biotypes.CCYV'infected cucumber plants caused changes in feeding efficiency of both biotypes and both sexes of the same biotype to various degrees.The feeding suitability of CCYV.infected cucumber plants for B and Q biotypes was weakened.B biotype had stronger feeding ability than Q biotype,but Q biotype had stronger CCYV transmission ability.CCYV-infected cucumber plants were less suitable for feeding to females than males,and females had stronger CCYV transmission ability than males.CCYV-infected cucumber plants were less suitable for feeding to Q biotype than B biotypt,and less suitable for feeding to both biotypes females than males.In conclusion,Q biotype had stronger insecticide adaptability than B biotype.On the other hand,B biotype had stronger host plants adaptability and feeding capacity than biotype Q.These factors may contribute to the competitiveness between B and Q biotypes under different conditions.