First report of Impatiens necrotic spot virus (INSV) infecting basil (Ocimum basilicum) in the United States.
During the summer of 2011 and 2012, potted plants of basil in a commercial greenhouse in the Richland-Kennewick area of Washington State, USA, showed foliar symptoms consisting of chlorotic spots, ring spots, leaf distortion, and stem necrosis. In initial tests, extracts of symptomatic leaves were positive for Impatiens necrotic spot virus (INSV). To confirm the presence of INSV, the total RNA extracted from symptomatic leaves of basil was used for reverse transcription (RT)-PCR amplification of the nucleocapsid (N) gene using forward (5′-AGCTTAAATCAATAGTAGCA-3′) and reverse (5′-AGCTTCCTCAAGAATAGGCA-3′) primers. Sequence analyses of these clones (GenBank accession no. KC218475) showed 100% nucleotide sequence identity among themselves and 99% nucleotide sequence identity with INSV isolates from the United States (DQ523598, JX138531 and D00914) and a basil isolate (JQ724132) from Austria. This is thought to be the first report of the virus in basil in the United States.