ABSTRACT

Sunflower (Helianthus annuus L.) belongs to Asteraceae family. It suffers from sunflower necrosis disease (SND) along with other diseases. During the years 2022 and 2023, survey was conducted to know the status of SND in the selected regions of major sunflower growing areas of northern parts of Karnataka. The incidence of SND in late kharif (Aug-Sep) and rabi (Dec-Jan) exhibited a range of 2 to 81.15 per cent and 0 to 53.33 per cent, respectively. Among the surveyed districts, Bagalkot district recorded the highest mean per cent disease incidence (PDI) of 22.82 in late kharif season and Dharwad district recorded the highest mean PDI of 19.98 in rabi season. The total RNA extracted from SND-infected sunflower leaf samples subjected to RT-PCR using Coat Protein (CP) gene specific primers. This shows the amplification of the expected size of 929bp from the infected sunflower sample. Subsequently, the amplicons were cloned and sequenced. The obtained CP gene sequences subjected to BLAST analysis on NCBI. The results revealed that the CP gene exhibited a nucleotide similarity of 98-99 per cent with various isolates from within Karnataka and also with isolates of other regions. To investigate the transmission of TSV, a study involving mechanical sap inoculation and Thrips transmission was conducted on sunflower plants. Out of these two methods, mechanical transmission was the efficient method when compared to vector transmission. To assess the host range of TSV, various plant species from distinct families tested for TSV infection via mechanical sap inoculation. Symptoms observed on different crops such as cowpea, cotton and soybean encompass local lesions showed variations from chlorotic to necrotic spots.