Characterization of cucumber mosaic virus infecting coleus (Plectranthus barbatus) in Karnataka

Abstract

Plectranthus barbatus also known by the synonym Coleus forskohlii it is called as forskohlii and Indian coleus. It is a tropical perennial herb belongs to the family Lamiaceae widely cultivated in India used as traditional medicinal crop. Its tuberous roots produce forskolin, an extract useful for pharmaceutical preparations and research in cell biology. The incidence of mosaic with dark and light green patches, mottling, leaf distortion and reduction growth was noticed in commercial cultivation of coleus. For identification of the virus, the infected leaf sample extract was mechanically inoculated to different hosts such as chilli, tobacco, tomato, cucumber, cowpea and Chenopodium amaranticolor. Host range studies revealed that the virus showed severe mosaic symptoms on Nicotiana spp. and Cucumis spp. The virus produced systemic and local lesion symptoms in a different host. The Leaf dip preparation of virus infected leaf extract was observed under an electron microscope showed the presence of isometric particles of 28 nm in size. The healthy and infected samples were tested using DAC-ELISA against antibodies of CMV, GBNV and TSV the infected samples showed strong positive reaction with 1.85 optical density to CMV antibodies indicated the presence of CMV. For molecular identification, total RNA was isolated and used for RT-PCR amplification using CMV specific primers. RT-PCR resulted in the positive amplification in virus infected samples but not from a healthy control. The complete genome of CMV RNA-1 consists of 3360 nucleotides (nt) encoding replicase gene of 807 amino acids (aa). The CMV RNA-2 was 2983 nt in length containing 2a (859 aa) encoding RNA dependent RNA polymerase protein and 2b encoding viral silencing suppressor (112 aa), while RNA-3 encoding 3a movement protein (280 aa) and coat protein (219 aa) was 2223 nt in length. Phylogenetic analyses of nucleotide sequences of coleus CMV isolate is closely related to subgroup IB than to subgroup IA or II with other CMV isolates. In recombination analysis, the recombination event occurs between the subgroups of I, II as well as IA and IB in RNA 1, RNA2 and RNA3 of coleus isolate with other CMV isolates. To best of our knowledge, this is the first report of CMV infection in coleus.

Genetic Structure of Cucumber Mosaic Virus From Natural Hosts in Nigeria Reveals High Diversity and Occurrence of Putative Novel Recombinant Strains

“…However, this study established high diversity within the subgroup IB populations in Nigeria. Similar diversity patterns within the RNA1 and CP gene segments of subgroup IB populations have also been previously reported ( Revathy and Bhat, 2017 ; Giakountis et al, 2018 ; Pavithra et al, 2019 ). Intriguingly, diversity was high across both evaluated genes even when compared with existing Nigerian CMV sequences in the database.…”

Co-existence of chlorosis inducing strain of Cucumber mosaic virus with tospoviruses on hot pepper (Capsicum annuum) in India

“…In general, frequent reassortment and recombination occurs in segmented viruses over monopartite viruses 40 . Amicably, CMV undergoes prompt of genetic changes through reasssortment and recombination 27 , 41 , 42 . Thus, evolutionary mechanism is a characteristic attribution of multipartite viruses which plays significant role in emergence and interspecies transmission of viruses 43 .…”

Characterization of cucumber mosaic virus (CMV) subgroup IB infecting chilli in Tamil Nadu, India

“…Recombination analysis illustrates TN chilli 3 isolate have evolutionary ties with Indian black pepper isolate as a major parent and Egyptian tomato isolate as a minor parent. Apparently, the evolution of CMV presumably occurs due to the genetic exchange of recombination and reassortment (Pavithra et al 2019;Bonnet et al 2005;Roossink 2002). Comparatively, TN isolate 3 exhibited more variation in amino acids rather than other isolates.…”

“…Furthermore, subgroup I strains of CMV certainly produce symptom and disease development on Nicotiana (Zhang et al 1994). Similarly, sap transmission of CMV coleus isolates induced systemic mosaic mottling and leaf deformation on Capsicum annuum, Cucumis sativus and Cucurbita pepo plants (Pavithra et al 2019). However, accumulating evidences suggest that, severe mosaic and stunting symptom developed by most of the subgroup I strains, in contrary most of subgroup II strains shows mild symptom or asymptomatic (Roossinck 2001;Mochizuki and Ohki 2012;Pavithra et al 2019).…”

“…Understanding about genetic structure, diversity and evolutionary history of the viral population is an important aspect for developing management strategies. Moreover, CMV undergoes rapid genetic changes by genetic recombination and reassortment (Nouri et al 2014;Pavithra et al 2019). Hence, complete genome analysis is vital for the better conception about genetic structure and evolution of CMV.…”