Tomato leaf curl Patna virus causing tomato leaf curl disease in Bangladesh

Tomato leaf curl virus (ToLCV) has appeared as a potential threat to the tomato production in the world. ToLCV, a member of the family Geminiviridae may contain either bipartite or monopartite genome. The genetic nature of a monopartite ToLCV isolate characterized from the tomato leaf curl diseased samples of Jamalpur district, Bangladesh (ToLCV-JB) has been reported. The products of rolling circle amplification (RCA) were digested, cloned and sequenced. Sequence analysis revealed the features of begomovirus genome organization in the ToLCV-JB isolate, containing six open reading frames. BLAST analysis showed 100% sequence similarity with tomato leaf curl Patna virus (EU862323.1) and more than 80% similarity with other reported monopartite begomoviruses. Hence, the virus isolate was registered as Tomato leaf Curl Patna virus-[Bangladesh:Jamalpur:2014] isolate ToLCV-JB (Genebank Accession: KU933675.1) according to the suggestion of NCBI. Recombination analysis also did not show any genetic exchange between ToLCV-JB and ToLCV-Patna virus. Moreover, they belong to the same cluster as observed in phylogenetic analysis. The present work suggests the possibility of cross-border spread of ToLCV-Patna viruses without mutation and this could pose a threat to tomato production in Bangladesh as well as in the Asian continent. Introduction Geminiviruses are usually transmitted by insects and cause significant economic and yield losses to many crops (Moffat 1999, Varma and Malathi 2003). Members of the family geminiviridae are divided into nine genera, i.e. Becurtovirus, Begomovirus, Capulavirus, Curtovirus, Eragrovirus, Grablovirus, Mastrevirus, Topocuvirus and Turncurtovirus based on viral vector, genome organization and host range (Zerbini et al. 2017). These viruses possess either monopartite (DNA-A) or bipartite (DNA-A and DNA-B) genome, which is single stranded of approximately 2.7 kb size and contains ~220 bp common region (CR) (Ahmed 1991, Navot 1991). DNA-A is required for viral replication, encapsidation, transmission and spread in its host (Ahmed 1991). Studies have confirmed that when monopartite genome only was inoculated into a susceptible host, it gave rise to disease symptoms like those of the field (Dry et al. 1993). Tomato leaf curl virus (ToLCV) belongs to the genus Begomovirus, transmitted by whitefly (Bemisia tabaci) and is commonly found in tropical and subtropical climates (Chakraborty et al. 2003, Fazeli et al. 2009). ToLCV is a major causative agent for the serious reduction of tomato production if transmitted at a very early stage of plant development. The infected plants become severely stunted, leaflets curls upward, become distorted and have yellow margins. The discovery of ToLCV in Bangladesh together with its spread has provoked the need to manage ToLCV situations (Kamal et al. 2015). Both monopartite (Green et al. 2001) and bipartite (Maruthi et al. 2005, 2006) ToLCV isolates have been reported earlier in Bangladesh with limited information. Therefore, the study of the identity, distribution, molecular variability, and the threat that these arising geminiviruses pose to tomato production in Bangladesh has become very important. In this report, molecular identification of a novel monopartite virus causing tomato leaf curl disease in Bangladesh showing 100% sequence similarity with tomato leaf curl Patna virus was described. *Author for correspondence: . Department of Genetic Engineering and Biotechnology, Jessore University of Science and Technology, Jessore-7408, Bangladesh.