Abstract:

【Aim】 This study focuses on two important tomato viruses, tomato chlorosis virus (ToCV) and tomato yellow leaf curl virus (TYLCV). It aims to explore the effects of ToCV single infection and TYLCV&ToCV co-infection on the host adaptability of Bemisia tabaci MED, and to reveal the physiological mechanism from the perspective of host plant nutrient contents and defense responses. 【Methods】 After ToCV single infection andTYLCV&ToCV co-infection, the survival rates and number of eggs laid of B. tabaci MED adults on the infected tomato plants, and the contents of amino acids and total sugar in the infected tomato plants were detected. Additionally, the expression profiles of key genes related to jasmonic acid (JA) (FAD7 and PI II) and salicylic acid (SA) (NPR1 and PR1) signal pathways in tomato plants in response to ToCV single infection and TYLCV&ToCV co-infection were analyzed by RT-qPCR. 【Results】 The survival rate and number of eggs laid of B. tabaci MED adults feeding on the tomato plants infected by tomato viruses decreased significantly compared to those feeding on the healthy tomato plants. Feeding onthe TYLCV&ToCV coinfected tomato plants could reduce the survival rate and number of eggs laid of B. tabaci MED adults to the lowest level. The contents of total amino acids, fourteen types of hydrolyzed amino acids and total sugar in the TYLCV&ToCV co-infected tomato plants were significantly lower than those in the ToCV-singly infected tomato plants. The expression levels of FAD7 and PI II were significantly downregulated in tomato plants infected by ToCV and TYLCV&ToCV, and the expression levels of these two genes were the lowest in the TYLCV&ToCV co-infected tomato plants. However, the expression levels of NPR1 and PR1 were upregulated in tomato plants infected by ToCV and TYLCV&ToCV. The expression levels of NPR1 in the TYLCV&ToCV co-infected tomato plants and PR1 in the ToCV-singly infected tomato plants were all significantly higher than those in the healthy tomato plants. 【Conclusion】 Both ToCV single infection and TYLCV&ToCV co-infection could decrease the host adaptability of B. tabaci MED on tomato plants, and TYLCV&ToCV co-infection brought a more adverse effect on the survival of B. tabaci MED. Compared with the healthy tomato plants, the nutritional condition and defense system in ToCV-singly infected and TYLCV&ToCV co-infected tomato plants have obviously altered and are different between both. The results provide a basis for revealing the interaction between B. tabaci and plant viruses.

Key words: Bemisia tabaci; Tomato chlorosis virus, co-infection, host adaptability, nutritional condition, defense response