Invasive Species Compendium

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Abstract

First report of Prunus necrotic ringspot virus infecting red mulberry (Morus rubra) in the U.S.A.

Abstract

In August 2019, twelve individual leaf samples of 12 red mulberries (Morus rubra) from a nursery in Alachua County (Florida, USA), were brought to Florida Department of Agriculture and Consumer Services, Division of Plant Industry, in Gainesville for pathogen identification. Approximately 30 mulberry plants out of 35 were affected with a chlorotic line pattern on the fully expanded leaves. Because of the symptom resemblance in the foliage to that of Prunus necrotic ringspot virus (PNRSV) infection and its recent detection in Morus alba, a test for PNRSV was carried out with enzyme-linked immunosorbent assay (ELISA). Leaves from two M. alba plants from the same nursery that showed no symptoms were used as a healthy control along with Nicotiana tabacum. ELISA testing yielded positive results for PNRSV infection on all symptomatic plants and negative for the asymptomatic plants. To further confirm infection by PNRSV, total RNA was extracted from two symptomatic samples, and reverse transcription polymerase chain reaction (PCR) was performed. An amplicon of the expected size (~700 bp) was observed. The PCR product was sequenced in both directions, and a BLASTN search against the GenBank database indicated that the sequences had 97% identity with PNRSV (GenBank accession MH282500). The isolate was designated as PNRSV-FL, Florida isolate. This finding corroborates previous findings that the virus could only be found in symptomatic plants. There had been only one report of this virus in mulberry from the UK.