Abstract
In China, Tomato chlorosis virus (ToCV) and Tomato yellow leaf curl virus (TYLCV) are widely present in tomato plants. The epidemiology of these viruses is intimately associated with their vector, the whitefly (Bemisia tabaci MED). However, how a ToCV+TYLCV mixed infection affects viral acquisition by their vector remains unknown. In this study, we examined the growth parameters of tomato seedlings, including disease symptoms and the heights and weights of non-infected, singly infected and mixed infected tomato plants. Additionally, the spatio-temporal dynamics of the viruses in tomato plants, and the viral acquisition and transmission by B. tabaci MED, were determined. The results demonstrated that: (i) ToCV+TYLCV mixed infections induced tomato disease synergism, resulting in a high disease severity index and decreased stem heights and weights; (ii) as the disease progressed, TYLCV accumulated more in upper leaves of TYLCV-infected tomato plants than in lower leaves, whereas ToCV accumulated less in upper leaves of ToCV-infected tomato plants than in lower leaves; (iii) viral accumulation in ToCV+TYLCV mixed infected plants was greater than in singly infected plants; and (iv) B. tabaci MED appeared to have a greater TYLCV, but a lower ToCV, acquisition rate from mixed infected plants compared with singly infected plants. However, mixed infections did not affect transmission by whiteflies. Thus, ToCV+TYLCV mixed infections may induce synergistic disease effects in tomato plants.
Highlights
Tomato (Solanum lycopersicum Mill.) is an economically important and widely cultivated crop worldwide
Efforts to elucidate the relationships among Tomato chlorosis virus (ToCV), Tomato yellow leaf curl virus (TYLCV), their host plants and their vector B. tabaci MED are important for understanding virus epidemiology and developing effective viruscontrol management strategies
ToCV and TYLCV accumulations in mixed infected tomato plants were greater than those in ToCV or TYLCV singly infected tomato plants, suggesting that a pattern of synergism between ToCV and TYLCV promotes their replication and these viruses overcome the resistance of host plant
Summary
Tomato (Solanum lycopersicum Mill.) is an economically important and widely cultivated crop worldwide. Diseases caused by whitefly-transmitted plant viruses have become a devastating factor in tomato production. The diseases caused by Tomato yellow leaf curl virus (TYLCV) and Tomato chlorosis virus (ToCV) are noteworthy (Mabvakure et al, 2016; Fiallo-Olivé and NavasCastillo, 2019). A single-stranded DNA Begomovirus, TYLCV seriously impacts tomato production throughout tropical and subtropical regions (Fauquet et al, 2005; Mabvakure et al, 2016). It was Synergistic Interactions Between ToCV and TYLCV first described in 1964 (Cohen and Harpaz, 1964) and has since rapidly spread into new regions near the Indian and Pacific oceans, including Australia, New Caledonia, and Mauritius (Lefeuvre et al, 2010; Mabvakure et al, 2016). ToCV and TYLCV can be efficiently transmitted in a semipersistent and persistent circulative manner by the same whitefly, Bemisia tabaci (Gennadius) MED, under natural conditions (Wintermantel and Wisler, 2006; Polston et al, 2014), and the continuous influxes of viruliferous whiteflies is a major factor responsible for the spread of these two viruses (Orfanidou et al, 2016; Shi et al, 2018; Macedo et al, 2019)
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