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.

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.

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.

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.