Virus Status of the Texas Grape Industry

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1 Virus Status of the Texas Grape Industry 2017 Advanced GRAPE GROWER Workshop Hill Country University Center, Fredericksburg June Sheila McBride Program Extension Specialist Texas Plant Disease Diagnostic Lab

2 Virus Biology o Obligate parasites - must have living host to replicate, cannot be cultured/grown in the classic way such as on growth media, o Reproduce only inside infected cells, o Depend on the aid of vectors (insects, nematodes, humans), propagation or the environment for their dissemination (spread).

3 Viruses infecting Grapevine o Grapes are hosts to >70 infectious agents globally o 15 families, 26 genera, several unassigned species

4 Major Virus Diseases Leafroll Rugose Wood Fanleaf Photo: Debra Golino

5 Major Virus Diseases o Redblotch disease is becoming an emerging threat to the sustainability of the US grape industry

6 Grapevine Leafroll Disease (GLD) o Most widespread o Associated with several distinct closteroviruses o Most GLRaVs belong to genus Ampelovirus o Grapevine leafroll-associated virus 3 (GLRaV-3) is predominant Photo: Rayapati Lab PRO p5 p20 p4 p6 p55 5 MET HEL CPm RdRp Hsp70 h 3 CP p21 GLRaV-3 (18,498 nt) p7 p20 PRO p5 p21 p24 5 MET HEL Hsp70 h RdRp p55 CP 3 CPm CPm GLRaV-1 (17,647 nt) PRO PRO p6 p19 p24 5 MET HEL Hsp70 h p63 CPm CP 3 RdRp GLRaV-2 (16,494 nt)

7 GLD Symptoms: Discoloration Cabernet Franc Photo: Rayapati Lab Chardonnay Photo: Rayapati Lab

8 GLD Symptoms: Leaf Rolling Merlot Photo: Rayapati Lab Chardonnay Photo: Rayapati Lab

9 Leafroll-like Symptoms P deficiency GLD Photo: Rayapati Lab Mechanical Injury Photo: Rayapati Lab Photo: Rayapati Lab

10 Transmission of GLRaVs Mealybug Photo: B. Bahder Vegetative cuttings Soft scale Photo: B. Bahder o And understanding of virus vector life cycle useful for disease management

11 Detection of GLRaVs Serological assays (ELISA) M Samples (+) (-) Molecular assays (RT-PCR)

12 GLD Spread Within Vineyard GLD incidence = 20% Photo: M. Al Rwahnih

13 GLD Spread Within Vineyard GLD incidence 5 years later = >60% Photo: M. Al Rwahnih

14 Chardonnay Cabernet Sauvignon

15 Negative Impacts of GLD o Reduced fruit load Grape cv. White Emperor o Delayed and uneven ripening o Reduced sugar o Increased acidity o Dependent on variety, GLD+ clone, rootstock, site, season, leafroll type and strain Healthy o Mixed infections of multiple viruses often results in enhanced negative impacts Photo: M. Al Rwahnih

16 Fanleaf (GVFL) o Caused by several nepoviruses o Possess RNA genomes o Vegetatively transmitted o Field spread mainly by vectors: longidorid (needle) nematodes o Associated with fruit yield losses and vine decline

17 Grapevine Redblotch Disease

18 GRBaV is widespread in the US Source: M. Al Rwahnih

19 Grapevine redblotch-associated virus o Posses a circular ssdna genome o Three-cornered Alfalfa Hopper, Spissistilus festinus, identified recently as a vector Other vectors currently being investigated

20 GLD-like Impacts of Redblotch Source: Poojari et al., 2013

21 Virus Survey in Texas Vineyards o Sample collection Growers and Viticulture Specialists o Sample preparation, ELISA and/or RT-PCR o Gel electrophoresis

22 Blanc du Bois (GLRaV-3+ ) Photo credit: Fran Pontasch

23 Photo credit: Fran Pontasch Redblotch Symptoms

24 Viruses detected 2016 o Based on analysis of 115 samples

25 Predominance of Mixed Infections Single virus (27.8%) 4 viruses 5 viruses 2 viruses 3 viruses Negative (14.8%) Not tested (1.7%)

26 GLRaV-3 Austin Hildalgo Gillespie Terry McClennan Hockley Walker Austin, Hildalgo, Gillespie, Terry, Harris, Victoria, Lynn, Walker GRBaV

27 Additional Findings o First Report of Tobacco ringspot virus Infecting an American Hybrid Grape Cultivar in Texas June 2017, Volume 101, Number 6 Page o Nepovirus- Transmitted by a nematode Xiphinema americanus ( Dagger )

28 Update on 2017 Findings o Soil samples collected from the TRSV positive vines Xiphinema sp. detected, PCR pending for detection of virus from nematodes collected. o 50 Samples submitted ELISA results for GVLRa-3 and GVFL GVLRa-3 7 positives found in 3 Blanc du Bois, 1 Victoria Red, 1 Black Spanish, 1 Sangiovese, and 1 wild mustang. GVFL All samples negative. PCR results pending for Grapevine leafroll-associated virus 1, Grapevine leafroll-associated virus 2, 3, 4, Tobacco ringspot virus, Grapevine fanleaf virus, Grapevine virus A and B, Grapevine rupestris stem pittingassociated virus, Grapevine red blotch-associated virus.

29 Managing Grape Virus Diseases o Propagate clean nursery stocks Buy only from certified nurseries o Practice area-wide vector management Use IPM tactics: insecticides, parasitoids, mating disruption o Manage virus alternative hosts Free-living grapes in riparian habitats o Overall goal is to Start Clean and Stay Clean

30 R&D Needs for a Growing Industry Disease & Virus Monitoring Disease Impact Assessments Clean Nursery Stocks Productive Vineyard Vector Identification Study Vector Biology Education & Outreach Vector Management o Virus disease management will be critical to maintaining a productive vineyard

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32 Sending samples to TPDDL

33 Proper sampling can ensure a proper diagnosis o Representation of transition area between symptoms being observed. o Entire plant if possible, if not foliar symptoms and subsample of root tissue. Fresh and kept fresh. o Complete information (completed form) Note dates/times (when did symptoms begin to appear?). Description of chemical management practices in the past 4 weeks. o Photographs helpful when putting the pieces of the puzzle together.

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36 Thanks to the Senate Bill 881 Questions?