Abstract
Plant viruses are threatening many valuable crops, and Citrus tristeza virus (CTV) is considered one of the most economically important plant viruses. CTV has destroyed millions of citrus trees in many regions of the world. Consequently, understanding of the transmission mechanism of CTV by its main vector, the brown citrus aphid, Aphis (Toxoptera) citricidus (Kirkaldy), may lead to better control strategies for CTV. The objective of this study was to understand the CTV–vector relationship by exploring the influence of viral genetic diversity on virus transmission. We built several infectious clones with different 5′-proximal ends from different CTV strains and assessed their transmission by the brown citrus aphid. Replacement of the 5′- end of the T36 isolate with that of the T30 strain (poorly transmitted) did not increase the transmission rate of T36, whereas replacement with that of the T68-1 isolate (highly transmitted) increased the transmission rate of T36 from 1.5 to 23%. Finally, substitution of p33 gene of the T36 strain with that of T68 increased the transmission rate from 1.5% to 17.8%. Although the underlying mechanisms that regulate the CTV transmission process by aphids have been explored in many ways, the roles of specific viral proteins are still not explicit. Our findings will improve our understanding of the transmission mechanisms of CTV by its aphid vector and may lead to the development of control strategies that interfere with its transmission by vector.
Highlights
Hundreds of plant pathogens are transmitted by insect vectors
Citrus tristeza virus (CTV) is a member of the Closteroviridae family, and it is transmitted by several aphid species, including the cotton or melon aphid (Aphis gossypii Glover), the spirea aphid (Aphis spiraecola (Patch)), the black citrus aphid (Toxoptera aurantii), and the brown citrus aphid (Aphis (Toxoptera)
Donor plants used for aphid transmission experiments (5 plants/treatment) were tested for CTV by Enzyme-Linked Immunosorbent Assay (ELISA)
Summary
Hundreds of plant pathogens are transmitted by insect vectors. The order Hemiptera contains the most common insect vectors (aphids, leafhoppers, psyllids, and whiteflies), which are responsible for the transmission of many destructive plant diseases [1]. CTV is one of the most ubiquitous viruses infecting citrus, and it has destroyed more than 100 million citrus trees that were grafted on sour orange (Citrus aurantium) in the United States, Brazil, Argentina, Venezuela, and Spain [4]. The symptoms of the disease caused by CTV depend on the citrus variety, CTV strain, and the selected rootstock [5]. Stem pitting is observed in infected sweet orange, mandarin, and grapefruit, whereas lemon and sour orange show stunting and yellowing [5]. Plants grafted on sour orange are very sensitive to CTV and show quick decline and dieback
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