Genetic diversity of cryptic species of Bemisia tabaci in Asia.

Bemisia tabaci is a species complex consisting of various genetically different cryptic species worldwide. To understand the genetic characteristics and geographic distribution of cryptic species of B. tabaci in Asia, we conducted an extensive collection of B. tabaci samples in ten Asian countries (Bangladesh, Indonesia, Japan, Korea, Myanmar, Nepal, Philippines, Singapore, Taiwan, and Vietnam) from 2013 to 2020 and determined 56 different partial sequences of mitochondrial cytochrome oxidase subunit I (COI) DNA. In addition, information on 129 COI sequences of B. tabaci identified from 16 Asian countries was downloaded from the GenBank database. Among the total 185 COI sequences of B. tabaci, the sequence variation reached to 19.68%. In addition, there were 31 cryptic species updated from 16 countries in Asia, that is, Asia I, Asia I India, Asia II (1-13), Asia III, Asia IV, Asia V, China 1-6, MEAM (1, 2, K), MED, Australia/Indonesia, Japan (1 and 2). Further, MED cryptic species consisted of 2 clades, Q1 and Q2. This study provides updated information to understand the genetic variation and geographic diversity of B. tabaci in Asia.

Upregulation of probing- and feeding-related behavioural frequencies in Bemisia tabaci upon acquisition of Tomato yellow leaf curl virus.

BACKGROUND: The behaviour of insect vectors can be altered by the acquisition of plant viruses. Bemisia tabaci, which is the vector of Tomato yellow leaf curl virus (TYLCV), causes damage to susceptible tomato cultivars. Here, the frequencies of several behavioural characteristics related to probing and feeding that are exhibited by non-viruliferous (NV) and TYLCV-viruliferous (V) adult B. tabaci were compared using a sandwich-type parafilm cage. RESULTS: The frequencies of behaviours such as wing flapping, leg movement, body shaking and body position change while settling and feeding on plant leaves were higher in V than in NV whiteflies. Evaluation of probing frequencies by measuring the number and size of holes punctured in parafilm by whiteflies revealed that most holes had a diameter of 7.5-26.7 µm, which is within the range of proboscis diameters of whiteflies. There were more small-sized holes than medium- and large-sized holes. Male whiteflies produced more small-sized holes, but females more mid-sized holes. V whiteflies showed increased hole numbers but decreased feeding duration relative to NV whiteflies. CONCLUSION: Adult B. tabaci showed higher frequencies of probing and feeding behaviours when infected with TYLCV. These manipulations of feeding behaviours of insect vectors may result in increased transmission of plant virus.