Biological and Molecular Characterization of Tomato Leaf Curl Virus (ToLCV) in South Gujarat
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Date
2016-04
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PLANT PATHOLOGY DEPT.,N.M.COLLEGE OF AGRICULTURE, NAVSARI AGRICULTURAL UNIVERSITY, NAVSARI
Abstract
Incidence of Tomato Leaf Curl Disease (ToLCD) in the protected as well open field condition was observed during the present investigation to the tune of 10-50 per cent. The typical symptom includes upward/downward curling along with the vein clearing of leaves. Fruit, if produced at all, were small, dry and unmarketable. Initially the newly emerging plant leaflet started showing mild vein clearing and leaf curling symptoms. Symptoms gradually become severe showing characteristic moderate to severe leaf curling (upward or downward) and shrinking of the leaves. Leaves were often stiff, thicker and of leathery texture rather than flaccid. Affected plants grew slowly and became stunted or dwarfed. The flowers appear normal. No chlorotic or yellowing of the leaf lamina could be seen. The virus was transmitted by approach as well as side veneer grafting. In PCR a part DNA-A molecule of ~1200 bp was amplified by the Begomovirus specific primers confirming it to be Begomovirus. A 1125 bp nucleotide sequence (Accession number KU921251) was obtained on sequencing. Amplified fragment had two genes viz., virus coat protein (V1) gene and pre coat protein (V2) gene. The sequenced virus showed highest identity (94%) with Tomato leaf curl Gujarat virus [Nepal] segment
DNA A, [AY234383.1] followed by 93% sequence identity with thirteen different tomato Begomoviruses which were the strains/isolates of Tomato leaf curl Gujarat virus or Tomato leaf curl New Delhi virus [DQ629101.2]. The virus was named as Tomato leaf curl Gujarat virus [Nepal] [India:Nvs: Tom:2016] and was abbreviated as ToLCGV [Nepal] [India:Nvs:Tom:2016]. Alignment of the sequenced virus with the other Begomoviruses of the different crops from the different location indicated that the virus was typically a leaf curl virus. Virus which produced yellow leaf curl symptoms and yellow mottle symptoms were entirely different from the virus characterized during the present investigation. Two distinct categories of virus producing different types of symptoms viz., Leaf Curl (LC) and Yellow Mottle (YM) are included in the ToLCD. It is very difficult to recognize the symptoms of the viral disease by the virus name as found in other viruses. Both the categories of the virus have been reported from the area in the past, however, the study concluded that the ToLCD is predominantly caused by the Tomato Leaf Curl Virus belonging to Leaf Curl category in the area surveyed. All the morphological, biological and molecular results were found supporting, that the virus studied was leaf curl type only.
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