Grapevine necrotic union, a newly recognized disease in grapevines on 110 Richter rootstock in California

• Published in: Phytopathology Vol. 100; no. 6; p. S3
• Main Authors: Al Rwahnih, M, Rowhani, A, Smith, R J, Uyemoto, J K, Sudarshana, M R
• Format: Journal Article
• Language: English
• Published: 01-06-2010
• Subjects: Riparia; Vitaceae; Vitis vinifera
• ISSN: 0031-949X

In early fall of Yr 2004, inspection of a 7-year old vineyard of Pinot noir (PN) clone 02A (Vitis vinifera L.) grafted on rootstock 110 Richter (11OR; V. berlandieri x V. rupestris) in Sonoma County, CA, revealed 6 2.1% of the grapevines with symptoms of solid red leaf blades, weak shoot growth and grape clusters with reduced set. Examination of trunk specimens indicated a necrotic line at the scion-rootstock junction and hence named "grapevine necrotic union" (GNU). Yearly surveys indicated that GNU incidence gradually increased to 22% in Yr 2009. This disease was also observed in PN clones 02A (PN02A), 04, 667, and 777, in Napa County, and Pinot gris 152 on 11OR in Monterey County, and the incidence ranged from 2.0% to 45%. RT-PCR assays did not indicate any known grapevine viruses that could be considered associated with diseased vines. Repeated chip bud grafts of diseased vines onto test plants of Cabernet Sauvignon 08 on 11OR rootstock failed to demonstrate a graft-transmissible agent. However, bench grafts of several PN clones and Chardonnay-04 (Ch-04) produced GNU on 11OR but not on rootstock 3309 Couderc (V. riparia x V. rupestris). Ultradeep sequencing analysis of cDNA made from dsRNA obtained from bark scrapings indicated the association of Grapevine redglobe virus and Grapevine rupestris vein-feathering virus in Ch-04 and PN02A vines. These two viruses were also found associated with GNU affected vines in Napa County.