Abstract: 【Aim】 The whitefly Bemisia tabaci is the only vector of Tomato yellow leaf curl virus (TYLCV) in the field. In addition to direct acquisition of the virus through feeding, the whitefly can acquire the virus via mating. Although previous studies have shown that both cryptic species Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) of the whitefly complex can achieve horizontal transmission of TYLCV via mating, the results on the efficiency of virus transmission via this means by the two species were not consistent. Moreover, experimental evidence is yet lacking to show whether this type of horizontal transmission of TYLCV may facilitate the spread of the virus in the field. 【Methods】 We first collected the field populations of cryptic species MEAM1 and MED of B. tabaci from four provinces in China, including Zhejiang, Guangdong, Yunnan and Henan, and following molecular identification ofthe species status of each of the populations we established seven pure cultures for experiments. Then, we observed the capacity of TYLCV transmission between viruliferous and non-viruliferous adults in each of the populations. And finally, we used the MEAM1 culture from Guangdong Province to simulate a scenario of group mating and examined the capacity of the adults, which acquired TYLCV via mating, in transmitting the virus to tomato plants. 【Results】 Both MEAM1 and MED populations of B. tabaci collected from the four provinces were able to achieve horizontal transmission of TYLCV via mating, although the efficiency of transmission was in general low, mostly below 10%. No significant differences were detected in the efficiency of transmission between the MED populations from the four provinces, between MEAM1 populations from three of the four provinces, and between the two cryptic species within each of the provinces. In each of the two cryptic species, both viruliferous male and female adults were able to transmit viral DNA to individuals of the opposite sex, and no significant differences in the efficiency of virus transmission between the two sexes were found. The data of the group mating test indicated that the originally nonviruliferous individuals were unable to transmit TYLCV to tomato plants following their acquisition of the virus via mating. 【Conclusion】 These results demonstrate that for the virus TYLCV and whiteflies of the cryptic species MEAM1 and MED of B. tabaci tested here low efficiency of horizontal transmission of TYLCV can be expected. However, the data obtained with the Guangdong MEAM1 population suggest that the low horizontal transmission does not increase the number of individuals capable of transmitting the virus to infect new tomato plants. Consequently, the horizontal mode of transmission is unlikely to have much epidemiological relevance in the field.

Key words: Bemisia tabaci , cryptic species, virus transmission, Tomato yellow leaf curl virus (TYLCV), mating, horizontal transmission