First report of Moroccan pepper virus in association with yellows on escarole in the US and world

Authors: Wintermantel, William - Bill; BACHINSKY, DAVID - Crop Production Services, Inc

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2014
Publication Date: 5/30/2014
Citation: Wintermantel, W.M., Bachinsky, D. 2014. First report of Moroccan pepper virus in association with yellows on escarole in the US and world. Plant Disease. DOI: 10.1094/PDIS-04-14-0394-PDN.

Interpretive Summary: During the fall of 2013 endive (Cichorium endivia L.) and escarole (C. endivia L., var latifolia) fields within a 15-mile radius of Vineland, New Jersey were found with severe disease symptoms. The cores of the heads were necrotic and rotted, while outer leaves were chlorotic and had pronounced yellow veins. Similar symptoms have been observed annually in the area, and were on plants grown in sandy loam soils following a period of extended soil moisture and heavy rains. Most escarole and endive in the ground at that time developed symptoms, whereas plants seeded or transplanted after these rain events did not develop symptoms. Total RNA was extracted from all plant samples, and RT-PCR was performed using specific primer sets designed to amplify a portion of the coat protein gene of either Tomato bushy stunt virus (TBSV) or Moroccan pepper virus (MPV), another member of the tombusvirus genus including isolates formerly known as Lettuce necrotic stunt virus. All samples tested negative for TBSV, but one sample of escarole was positive for MPV. Direct sequencing confirmed 97% identity to MPV isolates from both California and Morocco. Secondary confirmation was obtained with an additional primer set designed to amplify a region encoding the smaller of two virus replication proteins. Direct sequencing confirmed 98 and 99% identity to MPV isolates from California and Morocco, respectively. Following confirmation, eight samples of escarole from three additional farms in the same area of New Jersey were tested, with two confirmed positive for MPV using the same protocols described above. This is the first report of MPV in escarole, and the first report of MPV in the U.S. outside of California and Arizona. MPV and TBSV are known to cause the disease, lettuce dieback, in the western U.S., but that disease has not been observed in other lettuce growing regions to date. Like the core collapse on escarole, lettuce dieback is also associated with saturated soils and other stress factors. The lack of complete correlation between MPV incidence and the necrosis symptoms suggests that MPV is not the sole cause of core collapse in escarole and endive; however, the identification of MPV in this important leafy greens production region and its association with core collapse symptoms in escarole warrant further study of the association of MPV and potentially other tombusviruses with core collapse.

Technical Abstract: During the fall of 2013 endive (Cichorium endivia L.) and escarole (C. endivia L., var latifolia) fields within a 15-mile radius of Vineland, New Jersey were found with severe disease symptoms. The cores of the heads were necrotic and rotted, while outer leaves were chlorotic and had pronounced yellow veins. Similar symptoms have been observed annually in the area, and were on plants grown in sandy loam soils following a period of extended soil moisture and heavy rains. Most escarole and endive in the ground at that time developed symptoms, whereas plants seeded or transplanted after these rain events did not develop symptoms. Total RNA was extracted from all plant samples, and RT-PCR was performed using specific primer sets designed to amplify a portion of the coat protein gene of either Tomato bushy stunt virus (TBSV) or Moroccan pepper virus (MPV), another member of the tombusvirus genus including isolates formerly known as Lettuce necrotic stunt virus. All samples tested negative for TBSV, but one sample of escarole was positive for MPV. Direct sequencing confirmed 97% identity to MPV isolates from California (JN700748) and Morocco (JX197071). Secondary confirmation was obtained with an additional primer set designed to amplify a 372 nt region of ORF1 of select tombusviruses. Direct sequencing confirmed 98 and 99% identity to MPV isolates from California (JN700748) and Morocco (JX197071), respectively. Following confirmation, eight samples of escarole from three additional farms in the same area of New Jersey were tested, with two confirmed positive for MPV using the same protocols described above. This is the first report of MPV in escarole, and the first report of MPV in the U.S. outside of California and Arizona. MPV and TBSV are known to cause the disease, lettuce dieback, in the western U.S., but that disease has not been observed in other lettuce growing regions to date. Like the core collapse on escarole, lettuce dieback is also associated with saturated soils and other stress factors. The lack of complete correlation between MPV incidence and the necrosis symptoms suggests that MPV is not the sole cause of core collapse in escarole and endive; however, the identification of MPV in this important leafy greens production region and its association with core collapse symptoms in escarole warrant further study of the association of MPV and potentially other tombusviruses with core collapse.