Emergence of Asian endemic begomoviruses as a pandemic threat

Abstract

Plant viruses are responsible for the most devastating and commercially significant plant diseases, especially in tropical and subtropical regions. The genus begomovirus is the largest one in the family Geminiviridae, with a single-stranded DNA genome, either monopartite or bipartite. Begomoviruses are transmitted by insect vectors, such as Bemisia tabaci. Begomoviruses are the major causative agents of diseases in agriculture globally. Because of their diversity and mode of evolution, they are thought to be geographic specific. The emerging begomoviruses are of serious concern due to their increasing host range and geographical expansion. Several begomoviruses of Asiatic origin have been reported in Europe, causing massive economic losses; insect-borne transmission of viruses is a critical factor in virus outbreaks in new geographical regions. This review highlights crucial information regarding Asia's four emerging and highly destructive begomoviruses. We also provided information regarding several less common but still potentially important pathogens of different crops. This information will aid possible direction of future studies in adopting preventive measures to combat these emerging viruses.

Keywords: Asia; Papaya leaf curl virus; Tomato leaf curl New Delhi virus; Tomato yellow leaf curl virus; begomoviruses; geminiviruses; geographical distribution.

Figure 1

Species distribution of geminivirus. Number of species in each genus. It can be clearly seen that the genus Begomovirus has the highest number of species among the family Geminiviridae.

Figure 2

Begomovirus genome: (A) DNA-A segment of begomovirus. (B) DNA-B segment found in bipartite begomovirus along with DNA-A. (C) Alphasatellite, (D) betasatellite and (E) deltasatellite associated with monopartite begomoviruses.

Figure 3

Expansion of TYLCV on the world map. Possible infected countries are highlighted in two different ways. Green dots indicate the infected countries till 2010, while red triangles indicate the expansion of this virus into new countries.

Figure 4

The emergence of ToLCNDV in Europe and Africa. Green dots indicate that infection was dominant in Southeast Asia until 2010. Blue triangles indicate the invasion of ToLCNDV in Europe and North Africa after 2010.

Figure 5

Geographical location: The map shows the distribution of some important begomoviruses in Asia.

Figure 6

Symptoms of begomoviruses: (A) Tomato plant depicts the symptoms of Tomato yellow leaf curl Kanchanaburi virus; (B) symptoms of Pepper yellow leaf curl Indonesia virus; (C) papaya plants exhibit symptoms like yellowing, downward or upward curling, and vein thickening caused by Papaya leaf curl virus; (D) symptomatic eggplant showing leaf curling caused by Tomato leaf curl Joydebpur virus; (E) plant showing symptoms of Tomato yellow leaf curl Thailand virus; and (F) Tomato yellow leaf curl virus causes symptoms like leaf yellowing, upward and downward leaf curling, and reduction in leaf size.

Figure 7

Phylogeny of DNA-A: The DNA-A sequences of different endemic begomoviruses were downloaded and assembled by Muscle Alignment module in MEGA-11. The phylogeny was constructed by maximum likelihood method with 500 bootstrap replications. The resulting tree was exported and visualized in iTOL (Letunic and Bork, 2021).