Epidemiological Study of Begomoviruses of East Asian Region

Abstract

Begomoviruses (family Geminiviridae) are group of plant viruses that have circular single stranded (ss) DNA genome(s). They are transmitted through a single species of whitefly (Bemisia tabaci G.) Wide range of economically significant crops are affected by Begomoviruses. They reside in weeds and ornamental plants when there is off season for major crop hosts. That is why weeds and ornamental plants serve as alternate hosts, source of inoculum and recombination sites for economically important Begomoviruses. After the revision of criteria for classification of Begomoviruses, the naming of some isolates has become ambiguous. This study analyzes species demarcation, geographic distribution, host range and year of collection of Begomoviruses present in east Asia. Begomovirus sequences were retrieved from publicly available database National Center for Biotechnology Information. FASTA files were uploaded for nucleotide sequences to Sequence Demarcation Tool Version 1.2. MUSCLE alignment and species demarcation was done for evaluating isolates of various species. Phylogenetic tree was developed using maximum likelihood method of Mega X. MS Excel was used to generate maps and graphs. The diversity of east Asian Begomoviruses resides in about 91 plant species. Maximum number of virus isolates were extracted from Solanum lycopersicum (272) followed by Ipomoea batatas(141). Other affected crops were Piper nigrum (20), Passiflora edulis (35) and Cucurbita maxima (29). In weeds Ageratum conzoides is the major reservoir of Begomoviruses followed by Malvastrum coromandelianum. A single virus species has capability to infect members of multiple plant families. Maximum number of plants have been affected by Ageratum yellow vein virus. It has been analyzed to infect 22 plant species which include important crops like Solanum lycopersicum, Piper nigrum, Manihot esculenta, Phaseolus vulgaris, Carica papaya, Glycine max and Capsicum annuum. Selected Begomoviruses were abundant in East Asia. 597 have been reported from China, 81 from South Korea, 72 from Taiwan and 29 from Japan. Other major infected countries were India (31), Brazil (31) Thailand (28), Vietnam (25) and Pakistan (13) Extensive analysis of Begomoviruses showed that these Begomoviruses are spread to a total of 31 countries. Sweet potato leaf curl virushas been reported from 17 countries. Geographic distribution analysis of begomoviruses has resulted in the revelation that a number of them have now crossed national boundaries