First Report of the Satellite DNA Beta Associated with Tomato Yellow Leaf Curl Virus – Mild on Tomato in Iraq

Abstract

In November 2021, severe symptoms of TYLCV disease were observed in tomato fields in Karbala Province, Iraq. Symptomatic tomato samples were observed on 20 to 30% of plants. Samples of symptomatic plants were collected randomly. TYLCV-specific PCR primers were employed to confirm the presence of the virus. Total DNA was extracted and used as templates for next-generation sequencing. The unmapped reads were subjected to de novo assembly. The contigs assembled were compared with GenBank data of plant viruses. A BLASTn analysis revealed 99.34% similarity with tomato yellow leaf curl virus-mild (MT583814.1). This finding was confirmed by a PCR test using specific primers. Additionally, there was 94.66% pairwise identity with cotton leaf curl Gezira betasatellite (CLCuGB) isolate Al-Ain (KM279620.1). The universal primer pair for detection of betasatellites was applied, followed by Sanger sequencing of the amplicons, which confirmed the infection of all the tested plants with CLCuGB. The DNA sequence of CLCuGB has accession number ON206651. To verify the presence of TYLCV-mild and betasatellite, a field survey was conducted in the main regions of tomato cultivation in Karbala Province, Iraq, in November 2021. Symptomatic leaf samples were collected randomly from 40 fields and analyzed for virus infections. This analysis revealed that the virus and its satellite are distributed throughout the province. To our knowledge, this is the first record of occurrence and complete genome sequence of CLCuGB, associated with TYLCV-mild, in tomato fields in Iraq.