Comparative Analysis of Population Genetic Structure in Bemisia tabaci(Gennadius) Biotypes B and Q Based on ISSR Marker

Bemisia tabaci （Gennadius） biotypes B and Q are two invasive biotypes in the species complex. The comparison of the population genetic structure of the two biotypes is of significance to show their invasive mechanism and to their control. The intersimple sequence repeats （ISSR） marker was used to analyze the 16 B-biotype populations and 4 Q-biotype populations worldwide with a Trialeurodes vaporariorum population in Shanxi Province, China, and a B. tabaci non-B/Qbiotype population in Zhejiang Province, China, was used as control populations. The analysis of genetic diversity showed that the diversity indexes of biotype Q including Nei＇s gene diversity index, Shannon informative index, and the percentage of polymorphic loci were higher than those of biotype B. The high genetic diversity of biotype Q might provide the genetic basis for the excellent ecological adaptation. Cluster analysis suggested that the ISSR could not be used in the phylogenetic analysis though it could easily distinguish the biotypes of B. tabaci. The difference of the population genetic structure between the biotype B and the biotype Q exists based on the ISSR marker. Meanwhile, the results suggested that the molecular marker has its limitation in the phylogenetic analysis among the biotypes of B. tabaci.

Comparative Morphology and Morphometry of Six Biotypes of Bemisia tabaci (Hemiptera: Aleyrodidae) from China

Morphology and morphometry of six biotypes （B, Q, Cv, ZHJ-1, ZHJ-2 and ZHJ-3） of Bemisia tabaci （Gennadius） from China on cotton plants were studied by using microscopes. Nymphal body sizes and characters were measured and observed, especially on the 4th instar （pupal case）, including the vasiform orifice, operculum, lingula, length and thickness of anterior and posterior wax margins, width of thoracic tracheal combs. Adult characters of both sexes were investigated including the body size, compound eyes, antennal segments, vasiform orifice, hind tarsi and genitals. The results indicated that differences of some morphological characters or morphometrics were significant among the six biotypes of B. tabaci in China： （1） Pupal sizes of the exotic biotypes （B and Q） were significantly larger than the indigenous biotypes with the following order as B〉Q〉ZHJ-I〉Cv〉ZHJ-3〉ZHJ-2; （2） for both male and female adults, sizes of all characters investigated in the invading biotypes （B and Q）, especially B, were much larger than those of the indigenous ones.

Bemisia tabaci Biotype Dynamics and Resistance to Insecticides in Israel During the Years 2008-2010

The sweetpotato whitefly Bemisia tabaci（Hemiptera：Aleyrodidae）is an extremely polyphagous insect pest that causes significant crop losses in Israel and worldwide.B.tabaci is a species complex of which the B and Q biotypes are the most widespread and damaging worldwide.The change in biotype composition and resistance to insecticide in Israel was monitored during the years 2008-2010 to identify patterns in population dynamics that can be correlated with resistance outbreaks.The results show that B biotype populations dominate crops grown in open fields,while Q biotype populations gradually dominate crops grown in protected conditions such as greenhouses and nethouses,where resistance outbreaks usually develop after several insecticide applications.While in previous years,Q biotype populations were widely detected in many regions in Israel,significant domination of the B biotype across populations collected was observed during the year 2010,indicating the instability of the B.tabaci population from one year to another.Reasons for the changing dynamics and the shift in the relative abundance of B.tabaci biotype,and their resistance status,are discussed.

寄主植物对B型烟粉虱(Bemisia tabaci)几种主要解毒酶活性的影响

研究测定了棉花、一品红、茄子和番茄4个B型烟粉虱(Bemisia tabaci)种群α-NA羧酸酯酶、β-NA羧酸酯酶、乙酰胆碱酯酶和谷胱甘肽S-转移酶活性。结果表明:α-NA羧酸酯酶活性与β-NA羧酸酯酶活性比值均大于1,说明B型烟粉虱水解α-NA的能力高于对β-NA的水解能力;B型烟粉虱不同寄主种群α-NA羧酸酯酶、β-NA羧酸酯酶活性个体分布频率均存在一定差异。B型烟粉虱番茄种群羧酸酯酶活性最高(93.06 mOD/(mg protein.min)),是棉花种群的1.49倍。B型烟粉虱茄子种群乙酰胆碱酯酶活性明显高于其他寄主种群,达极显著差异水平(p<0.01);茄子种群乙酰胆碱酯酶活性分布频率在>4U/mgprotein区间段的分布高达85%,与其他3个寄主种群分布明显不同。B型烟粉虱茄子种群谷胱甘肽S-转移酶活性最高,与其他3个寄主种群间的差异达极显著水平(p<0.01)。上述结果表明,B型烟粉虱主要解毒酶活性在不同的寄主植物上具有一定的生理可塑性。研究有利于揭示该害虫寄主范围广和寄主适应性强的生理生态学基础。

Responses of Detoxifying, Antioxidant and Digestive Enzyme Activities to Host Shift of Bemisia tabaci (Hemiptera: Aleyrodidae)

The polyphagous B-biotype of Bemisia tabaci （Gennadius） has demonstrated a high capacity to adapt to numerous hosts from diverse plant families. To illustrate induced responses by the host plant, biochemical research on eight plant-insect interaction correlative enzymes, representing detoxifying, antioxidant and digestive pathways, were investigated. Transferring whitefly adults to Zhongmian 23 from the pre-adapted host Zhongmian 41 induced activities of carboxylesterase （by 1.80-fold）, glutathione S-transferase （by 3.79-fold）, proteinase （by 1.62-fold） and amylase （by 2.41-fold） activities, hut decreased polyphenol oxidase （by 1.89-fold） and peroxidase （by 1.88-fold）. However, transferring whitefly adults to the favorite host abutilon from Zhongmian 41 was associated with increased activities of cytochrome P450 monooxygenase （by 1.61-fold） and amylase （by 1.42-fold）, and decreased activities of polyphenol oxidase （by 2.96-fold） and peroxidase （by 2.07-fold）. Our results, together with previous studies, proved that multiple pathways are involved in coping with host shifts by polyphagous herbivores, and the taxonomic status and preference of the host transferred would affect which pathway would be induced. These results would represent a key challenge in developing long-term sustainable insect control strategies.

Sequence Analysis of mtDNA CO/Gene and Molecular Phylogeny of Different Geographical Populations of Bemisia tabaci (Gennadius)

Bemisia tabaci(Gennadius) is a serious pest in many cropping systems worldwide and occurs in different biotypes. ThemtDNA COI gene of the 12 Bemisia tabaci (Gennadius) populations from different regions and countries were analyzed.Based on mtDNA COI sequences, their biotypes were characterized and phylogenetic relationships among thesepopulations were established with the method of UPGMA. The results indicated the genetic similarity between thosepopulations from Beijing, Zhengzhou, Zaozhuang, Nanjing, Shanghai, Haikou, and the B-biotype populations fromCalifornia, Texas, Arizona reached 99.8-100%, which meant the nation-wide infested populations of B.tabaci in China inrecent years were B-biotypes. Another population collected from Kunming of Yunnan Province showed very high similaritywith Q-biotype B.tabaci from Spain and Morocco, which meant the Kunming population was Q-biotype. This is the firstreport on the invasion of Q-biotype into China.

cDNA Cloning of Heat Shock Protein Genes and Their Expression in an Indigenous Cryptic Species of the Whitefly Bemisia tabaci Complex from China

Thermal adaptation plays a fundamental role in shaping the distribution and abundance of insects,and heat shock proteins（Hsps）play important roles in the temperature adaptation of various organisms.To better understand the temperature tolerance of the indigenous ZHJ2-biotype of whitefly Bemisia tabaci species complex,we obtained complete cDNA sequences for hsp90,hsp70,and hsp20 and analyzed their expression profiles under different high temperature treatments by real-time quantitative polymerase chain reaction.The high temperature tolerance of B.tabaci ZHJ2-biotype was determined by survival rate after exposure to different high temperatures for 1 h.The results showed that after 41°C heat-shock treatment for 1 h,the survival rates of ZHJ2 adults declined significantly and the estimated temperature required to cause 50% mortality（LT50）is 42.85°C for 1 h.Temperatures for onset（Ton）or maximal（Tmax）induction of hsps expression in B.tabaci ZHJ2-biotype were 35 and 39°C（or 41°C）.Compared with previous studies,indigenous ZHJ2-biotype exhibits lower heat temperature stress tolerance and Ton（or Tmax）than the invasive B-biotype.

Effect of Different Temperature and Humidity on Bemisia tabaci

Bemisia tabaci has many biotypes,and has become one of the main pests on vegetables,flowers,cotton and other crops,seriously influencing the safe production of crops.Temperature has a great influence on the survival,development,reproduction and behavior of Bemisia tabaci,which can affect the change of body temperature and metabolism of B.tabaci.It needs certain water to maintain normal life activities,such as digestion,nutrition transportation,and temperature regulation.There is a suitable humidity range for the growth and development of B.tabaci in different development stages.High humidity or drought have a great impact on the growth and development of B.tabaci,especially on its survival or reproduction.At the same time,the environmental temperature and humidity are the important factors that influence the geographical distribution and population change of B.tabaci.

Overview of the Occurrence and Prevention of Bemisia tabaci Invasion in China

Biological invasion refers to the process of invading into another new environment through natural or man-made means from the original place of existence,which includes several stages of introduction,colonization,incubation,diffusion and outbreak.Bemisia tabaci is a worldwide important agricultural pest composed of multiple biotypes.Studies have confirmed that the B biotype Bemisia tabaci that invaded China has been genetically differentiated,and the Q biotype Bemisia tabaci has replaced the B biotype in most areas of China.Bemisia tabaci has become the dominant biotype in the field.

USING RAPD\|PCR TO DISTINGUISH BIOTYPES OF BEMISIA TABACI (HOMOPTERA:ALEYRODIDAE) IN CHINA

Ten populations of the whitefly Bemisia tabaci (Gennadius) collected from eight fieed and ornamental crops from seven provinces/cities in China were determined using RAPD PCR. Results showed that the 10 populations of B.tabaci could be classified into three distinct groups: a Biotype B group, a Guangxi group, and a Fujian group. The whiteflies in the Biotype B group were collected from sweetpotato and cotton in Beijing, tomato in Shandong, poinsettia in Shanghai and Guangdong, cabbage in Fujian, and hemp and eggplant in Xinjiang. The Guangxi group were collected from pumpkin in Nanning, Guangxi, and the Fujian group, from sweetpotato in Fujian. It was notable that B.tabaci specimens collected on cabbage in Fujian belonged to the Biotype B group. It is clear that Biotype B does now occur in China, in Beijing, Shandong, Xinjiang, Shanghai, Fujian and Guangdong. It is likely that the Guangxi and Fujian groups are native to China.

Invasive mechanism and management strategy of Bemisia tabaci(Gennadius) biotype B:Progress report of 973 Program on invasive alien species in China

Bemisia tabaci(Gennadius) biotype B,called a "superbug",is one of the most harmful biotypes of this species complex worldwide.In this report,the invasive mechanism and management of B.tabaci biotype B,based on our 5-year studies,are presented.Six B.tabaci biotypes,B,Q,ZHJ1,ZHJ2,ZHJ3 and FJ1,have been identified in China.Biotype B dominates the other biotypes in many regions of the country.Genetic diversity in biotype B might be induced by host plant,geographical conditions,and/or insecticidal application.The activities of CarE(carboxylesterase) and GSTs(glutathione-S-transferase) in biotype B reared on cucumber and squash were greater than on other host plants,which might have increased its resistance to insecticides.The higher activities of detoxification enzymes in biotype B might be induced by the secondary metabolites in host plants.Higher adaptive ability of biotype B adults to adverse conditions might be linked to the expression of heat shock protein genes.The indigenous B.tabaci biotypes were displaced by the biotype B within 225 d.The asymmetric mating interactions and mutualism between biotype B and begomoviruses via its host plants speed up widespread invasion and displacement of other biotypes.B.tabaci biotype B displaced Trialeurodes vaporariorum(Westwood) after 4-7 generations under glasshouse conditions.Greater adaptive ability of the biotype B to adverse conditions and its rapid population increase might be the reasons of its successful displacement of T.vaporariorum.Greater ability of the biotype B to switch to different host plants may enrich its host plants,which might enable it to better compete with T.vaporariorum.Native predatory natural enemies possess greater ability to suppress B.tabaci under field conditions.The kairomones in the 3rd and 4th instars of biotype B may provide an important stimulus in host searching and location by its parasitoids.The present results provide useful information in explaining the mechanisms of genetic diversity,evolution and molecular eco-adaptation of biotype B.Furthermore,it provides a base for sustainable management of B.tabaci using biological and ecological measures.

Viral infection of tobacco plants improves performance of Bemisia tabaci but more so for an invasive than for an indigenous biotype of the whitefly

The ecological effects of plant-virus-vector interactions on invasion of alien plant viral vectors have been rarely investigated. We examined the transmission of Tomato yellow leaf cur/China virus （TYLCCNV） by the invasive Q biotype and the indigenous ZHJ2 biotype of the whitefly Bemisia tabaci, a plant viral vector, as well as the influence of TYLCCNV-infection of plants on the performance of the two whitefly biotypes. Both whitefly biotypes were able to acquire viruses from infected plants and retained them in their bodies, but were unable to transmit them to either tobacco or tomato plants. However, when the Q biotype fed on tobacco plants infected with TYLCCNV, its fecundity and longevity were increased by 7- and 1-fold, respectively, compared to those of the Q biotype fed on uninfected tobacco plants. When the ZHJ2 biotype fed on virus-infected plants, its fecundity and longevity were increased by only 2- and 0.5-fold, respectively. These data show that the Q biotype acquired higher beneficial effects from TYLCCNV-infection of tobacco plants than the ZHJ2 biotype. Thus, the Q biotype whitefly may have advantages in its invasion and displacement of the indigenous ZHJ2 biotype.

Effects of host, temperature and relative humidity on competitive displacement of two invasive Bemisia tabaci biotypes [Q and B]

Bemisia tabaci shifted unexpectedly in China from a predominance of B biotype to Q biotype during 2005-2008. This observation stimulated an interest in inves- tigating whether environmental factors, including host, temperature and relative humidity （RH） could possibly explain the observed shift in biotypes distribution. Results indicated that all three parameters examined influenced biotype survivability. The percentage of B biotype, when reared together on pepper plants with the Q biotype, decreased significantly from 66.7% in the founder population, to 13.6% and 3.7% in the first and second genera- tions, respectively. When the B （founder at 66.7%） and Q （founder at 33.3%） biotypes were reared together on eggplant alone, or on pepper-plus-eggplant combination, the population size of the B biotype either remained constant, or increased somewhat in the first and sec- ond generations. On eggplant, the effects of RH and temperature on the competitiveness between the Q and B biotypes （3 pairs of Q and 6 pairs of B） were not significant.

Impacts of transgenic Bt cotton on the stylet penetration behaviors of Bemisia tabaci biotype B Evidence from laboratory experiments

Stylet penetration behaviors of Bemisia tabaci biotype B on two transgenic cotton lines ＂GK12＂ and ＂GK19＂ expressing Bt toxic protein CrylA （Bt cotton） and a non-Bt conventional cotton line ＂Simian-3＂ （CK cotton） were recorded with the direct current electrical penetration graph （DC-EPG） technique. Our results suggested that EPG waveform patterns, types and characteristics [non-probe （NP）, pathway （C）, potential drops （pd） and phloem phase （E（pd））] ofBemisia tabaci biotype B were very similar on the three cotton lines. There were no obvious differences of pathway variables among whiteflies on the three cotton lines. Some phloem variables related to E（pd）l differed. Duration of 1st E（pd）l and mean duration of E（pd）l on both GK12 and GK19 were significantly shorter than that on CK cotton （P 〈 0.05）. Fewer whiteflies on GK have long E（pd）l. Other phloem variables including total duration of E（pd） summed, mean E（pd） duration and percentage of whiteflies reaching the phloem phase were similar among the three cotton lines.

Genetic differentiation of Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） biotype Q based on mitochondrial DNA markers

In the present study, genetic differentiation of Bemisia tabaci （Gennadius） biotype Q was analyzed based on mitochondrial cytochrome oxidase I （mt CO1） gene sequence. The results showed that B. tabaci biotype Q could be separated into two subclades, which were labeled as subclades Q1 and Q2. Subclade Q1 was probably indigenous to the regions around the Mediterranean area and subclade Q2 to Israel or Cyprus. It was because B. tabaci was composed of several genetically distinct groups with a strong geographical association between more closely related biotypes. Not all of the B. tabaci biotype Q in the non-Mediterranean countries come from the same regions. Until now, all B. tabaci biotype Q in China were grouped into subclade Q 1. The B. tabaci biotype Q introduced into the US included both subclades Q 1 and Q2. The genetic structure analysis showed higher genetic variation of subclade Q 1 than that of subclade Q2.

Multiple generation effects of high temperature on the development and fecundity of Bemisia tabaci （Gennadius） （Hemiptera Aleyrodidae） biotype B

Insects are ectotherms and their ability to resist temperature stress is limited. The immediate effects of sub-lethal heat stress on insects are well documented, but longer- term effects of such stresses are rarely reported. In this study, survival, development and reproduction of the whitefly, Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） biotype B, were compared over five consecutive generations at 27, 31 and 35℃ and for one generation at 37 ℃. Both temperature and generation significantly affected the fitness of the whitefly. These impacts were more dramatic with increasing generations and temperatures. Among the experimental temperatures, the most favorable for development and reproduction were 27 ℃ and 31 ℃. At 27 ℃, survival, development and fecundity were all stable over these five generations. At 31 ℃, immature survival rate was the highest in the fifth generation, but female fecundities decreased in the fourth and fifth generations. At 35 ℃, egg hatching rate, immature survival rate and female fecundity decreased significantly in the fourth and fifth generations. At 37 ℃, survival ofB. tabaci was not adversely affected, but female fecundity at 37 ℃ was less than 10% of that at 27 ℃ or 31 ℃. These results demonstrate that the lethal high temperature for B. tabaci is over 37 ℃, and the whitefly population continued expanding in the five generations at 35 ℃. The ability orB. tabaci biotype B to survive high temperature stress will play an important role in its population extension under global warming.

Utility of MtCOI polymerase chain reaction-restriction fragment length polymorphism in differentiating between Q and B whitefly Bemisia tabaci biotypes

The invasive, insecticide-resistant, Q whitefly biotype, has gradually spread to other countries including the US via human-mediated movement of plant materials. We assessed the utility of the VspI-based mtCOI （mitochondrion cytochrome oxidase I） polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） technique as a rapid, cost-effective, and reliable alternative for differentiating the Q from the dominant B biotype in Arizona. Using the standard mtCOI gene sequencing and mtCOI PCR-RFLP techniques, we biotyped eight whitefly strains of five individuals each collected from poinsettia and cotton at different locations in Arizona. Complete concordance was observed between the two methods, with three strains being identified as the Q biotype and five samples as the B biotype. We also scanned the mtCOI gene sequences for VspI polymorphisms in the B and Q biotype whiteflies currently available in the GenBank database. This global screening revealed the existence of three and four VspI polymorphic types for the Q and B biotypes, respectively. Nevertheless, all three VspI polymorphic Q biotype whiteflies shared a common and unique VspI site that can be used to differentiate Q biotype from the four VspI polymorphic B biotype whiteflies identified. These results demonstrate that the VspI-based mtCOI gene PCR-RFLP provides a reliable diagnostic tool for differentiating the Q and B biotype whiteflies in the US and elsewhere.

Development and reproduction of ‘B＇ biotype Bemisia tabaci （Gennadius） （Homoptera： Aleyrodidae） on four ornamentals

Effects of four commercial ornamentals on the development, survivorship and reproduction of the whitefly B biotype Bemisia tabaci (Gennadius) were studied in the laboratory (temperature 26 ±1℃; relative humidity 75%-90%; L: D 14:10). The total survivorship from egg to adult on hibiscus (Hibiscus rosa-sinensis L.), poinsettia (Euphorbia pulcherrima Will), cottonrose hibiscus (Hibiscus mutabilis L.) and variegated leafcroton (Codiaeum variegatum ‘Aucubaefolium') were 33.69%, 40.55%, 79.11%, and 29.39%,respectively. The developmental periods from egg to adult varied from 23.12 days on cottonrose hibiscus to 32.13 days on hibiscus. The average longevity of adult females ranged from 6.87 days on variegated leafcroton to 21.07 days on poinsettia. The average numbers of eggs laid per female were 9.20, 25.13, 54.45, and 26.79 on the above respective hosts. The intrinsic rates of natural increase (rm) for B biotype B. tabaci on cottonrose hibiscus was the highest. Based on life table analyses of whitefly populations, cottonrose hibiscus was the most suitable host for B biotype B. tabaci in this study.

B型烟粉虱与浙江非B型烟粉虱的竞争

为了了解近年来入侵中国的B型烟粉虱(Bemisiatabaci)取代本地非B型烟粉虱的潜能,在室内将一个B型与一个浙江非B型烟粉虱种群混合饲养在不同寄主植物上,跟踪观察混合种群中两个生物型个体数量相对比例的变化。结果表明,当两种生物型在棉花(Gossypiumhirsutum)上以相同初始数量共存竞争时,经过6代,非B型完全被B型替代;而在西葫芦(Cucurbitapepo)上以相同初始数量共存竞争时,只经过2代,非B型即完全被B型替代。在棉花上,即使以非B型占87%、B型占13%开始共存竞争,经过225d后,非B型也完全被B型替代。这说明B型烟粉虱具有在短期内竞争取代浙江非B型烟粉虱的能力。经分析,B型除了寄主范围比非B型的宽这一点对其竞争有利外,较强的内在竞争潜能也是其能成功入侵并替代本地非B型烟粉虱的一个重要原因。

B型烟粉虱对三种寄主植物及其挥发物的行为反应

利用Y型嗅觉仪,测定了B型烟粉虱Bemisia tabaci(Gennadius)雌虫对3种寄主植物、挥发物提取液、挥发物标样以及寄主植物挥发物模拟样的行为反应,并比较鉴定寄主植物挥发物的组分和含量,以期明确植物挥发物在B型烟粉虱寄主定向行为中的作用。结果表明:1)番茄植株和甘蓝植株及其相应的挥发物提取物对烟粉虱雌成虫均具有显著的引诱作用,而辣椒植株和挥发物提取物的引诱作用不明显;3种寄主植物和挥发物提取物分别两两之间比较时,烟粉虱的选择行为均极显著地表现为番茄>甘蓝>辣椒。2)番茄、甘蓝和辣椒具有不同的挥发物化学图谱,且挥发物组分的相对百分含量差异很大;番茄挥发物总量远远大于甘蓝和辣椒;从组分来看,番茄挥发物中主要为萜烯类(89.8%),甘蓝挥发物中主要为烷烃类(53.0%)。3)8种寄主植物挥发物标样(10-1～10-6μL/μL)中,除1,8-桉树脑始终对烟粉虱具有引诱作用外,丁子香酚、苎烯、里那醇和月桂烯则是分别在10-4～10-6,10-1～10-4,10-1～10-4和10-1～10-4μL/μL时,才具有引诱作用;α-蒎烯、顺-3-已烯-1-醇则在高浓度下(10-1和10-2μL/μL)对烟粉虱具有排斥作用,低浓度下对烟粉虱没有任何影响;正十二烷在任何浓度下对烟粉虱均没有任何作用。4)在辣椒上分别喷施番茄挥发物模拟样和甘蓝挥发物模拟样,均显著增加对烟粉虱的引诱作用,而在番茄上喷施辣椒挥发物模拟样则无明显增效作用。综合分析认为,挥发性物质在B型烟粉虱对不同寄主植物的选择偏好时具有重要的行为导向作用。