Potato virus Y. Positive sense RNA virus Potyviridae. Transmitted by several aphid species in a non-persistent, non-circulative manner

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1 Effects of Biotic Factors on Stored Potato Quality Hancock Agricultural Experiment Station Field Day Russell L. Groves Department of Entomology University of Wisconsin 1630 Linden Drive Madison, WI July 27, 2010

2 Potato virus Y Positive sense RNA virus Potyviridae Transmitted by several aphid species in a non-persistent, non-circulative manner Sequence of both transient and colonizing aphid species Marketable yield loss in potato seed production

3 PVY N PVY N Potato virus Y Complex PVY O PVY NTN PVY O PVY N PVY O PVY O

4 Research Objectives Investigate how the timing of PVY infection within the growing season and PVY strain (PVY O, and PVY N:O ) can affect the efficiency of tuber infection and the resulting long-term storability of harvested tubers. Characterize and qualify the extent of storage quality losses associated with current-season infestations of key insect pests of potato (biotic factors) including the potato leafhopper (and Colorado potato beetle).

5 PVY Field Study & Storage Trial, Hancock AES, * RCBD (4 varieties, 2 inoculation times, and 2 PVY strains) 1.) Russet Burbank, Atlantic, Silverton Russet, Russet Norkotah 2.) Inoculation Time (pre-, & post-flower) 3.) PVY strains (PVY O & PVY N:O 4.) Villetta Rose guard rows 5.) DAS-ELISA N:O ) * Storage: Processing (47 o F, 95% RH) Fresh Market (42 o F, 95% RH) * Quality Parameters (Harvest, 3, 6, 12, 18, 24, & 36 wks) 1.) Tuber weights 2.) Specific gravity 3.) Sprouting 4.) Internal defect (s) Experimental Replicate

6 PVY Impact(s) on Tuber Yield, 2008 Potato Variety PVY Strain Tuber Size (oz) Tubers Hill -1 Proportion Unclassified US (culls) Cwt ac -1 Atlantic O 5.2 ab 10.6 a 0.75 a 0.08 a 453 a N:O UTC Mean Yield Estimates by Cultivar / Virus Strain b 9.5 a 0.79 a 0.07 a 472 a 5.6 a 10.5 a 0.81 a 0.07 a 501 a Silverton O 4.8 a 9.4 a 0.79 a 0.1 a 425 a Russet N:O UTC 5.1 a 9.8 a 0.81 a 0.09 a 418 a 5.1 a 9.9 a 0.80 a 0.11 a 439 a Russet O 5.1 a 9.8 a 0.85 a 0.07 a 476 a Norkotah N:O UTC 5.1 a 9.9 a 0.86 a 0.05 a 467 a 5.3 a 10.2 a 0.86 a 0.06 a 479 a Russet O 3.5 ab 13.8 a 0.72 a 0.13 a 408 b Burbank N:O UTC 3.2 b 13.4 a 0.72 a 0.14 a 406 b 3.7 a 14.3 a 0.73 a 0.14 a 489 a 1 Means followed by the same letter in columns are not significantly different (P > 0.05; Fisher s Protected LSD; n = 4)

7 Mean Specific Gravity PVY Impact on Storage Quality: Specific Gravity / Percent Solids Silverton Russet Non-inoculated PVY O PVY N:O P= Aug 14-Nov 22-Feb 1-Jun 9-Sep Sample Date

8 Mean Specific Gravity PVY Impact on Storage Quality: Specific Gravity / Percent Solids Russet Burbank 1.06 P= Non-inoculated PVY O PVY N:O Aug 14-Nov 22-Feb 1-Jun 9-Sep Sample Date

9 17-Jun 6-Aug 25-Sep 14-Nov 3-Jan 22-Feb 12-Apr 1-Jun 21-Jul 9-Sep Mean Proportion Weight Loss PVY Impact on Storage Quality: Weight Loss / Shrinkage Non-inoculated PVY O Silverton Russet PVY N:O P< Sample Date

10 6-Aug 25-Sep 14-Nov 3-Jan 22-Feb 12-Apr 1-Jun 21-Jul 9-Sep Mean Proportion Weight Loss PVY Impact on Storage Quality: Weight Loss / Shrinkage Russet Burbank Phellem 0.4 Non-inoculated 0.3 PVY O PVY N:O Cortical cells P= Sample Date

11 Mean Sugars (mg/g FW) 25-Aug 14-Oct 3-Dec 22-Jan 13-Mar 2-May Sample Date PVY Impact on Storage Quality: Chemical Maturity sucrose glucose Russet Burbank P= P= Non-inoculated PVY

12 Mean Sugars (mg/g FW) 25-Aug 14-Oct 3-Dec 22-Jan 13-Mar 2-May Sample Date PVY Impact on Storage Quality: Chemical Maturity sucrose glucose Atlantic P= P= Non-inoculated PVY

13 Research Objectives Investigate how the timing of PVY infection within the growing season and PVY strain (PVY O, and PVY N:O ) can affect the efficiency of tuber infection and the resulting long-term storability of harvested tubers. Characterize and qualify the extent of storage quality losses associated with current-season infestations of key insect pests of potato (biotic factors) including the potato leafhopper (and Colorado potato beetle).

14 Insect Feeding Potato Storage General threshold rules for potato leafhopper: If adult count per sweep is: then. < 0.5 treat only if > 0.1 nymphs/leaf treat if nymphs present and adults present for > 2 weeks treat immediately if nymphs present, or within 1 week if not present > 1.5 treat immediately

15 PLH Feeding Damage, Impacts in Storage PLH Damage in Potato Document the impact of PLH feeding at different thresholds among selected cultivars in long-term storage: (A) Exclusion (row cover) (B) At-threshold (>1.0 adult / sweep) (C) Above threshold (>2.5 adult / sweep) ** Quality Parameters: 1.) Tuber weights / weight loss 2.) Specific gravity 3.) Percent sugars 4.) Internal defect (s)

16 Mean Specific Gravity PLH Impact on Storage Quality: Specific Gravity / Percent Solids Un-infested Russet Burbank At-thresholdthreshold Above threshold P= Jul 25-Au 14-Oc 3-Dec 22-Jan 13-Ma 2-May 21-Jun Sample Date

17 Mean Specific Gravity PLH Impact on Storage Quality: Specific Gravity / Percent Solids Atlantic 1.08 P= Un-infested At-thresholdthreshold 1.06 Above threshold 6-Jul 25-Aug 14-Oct 3-Dec 22-Jan 13-Ma 2-May 21-Jun Sample Date

18 Mean Sugars (mg/g FW) 25-Aug 14-Oct 3-Dec 22-Jan 13-Mar 2-May Sample Date PLH Impact on Storage Quality: Chemical Maturity sucrose glucose Russet Burbank P= P= Uninfested At-thresholdthreshold Above threshold

19 PVY & PLH Impact on Storage Quality: Summary In , 09, significant quality losses in storage (percent solids & shrinkage) associated with current season infection of Potato virus Y. Storage results in , continued to reveal PVY quality losses (shrinkage), although no significant impacts on sugars were observed. Trend towards storage impacts - PLH infestation - Low population densities challenge to achieve lasting infestation levels above established thresholds (2009). Include both CPB and PLH in storage studies

20 Co-authors & Acknowledgements Alex Crockford 1 Amy Charkowski 2 AJ Bussan 3 Andy Witherell 2 Bob Coltman 4 Rick Hafner 4 and Kevin Bula 4 Cooperative Extension 1, Langlade County Agricultural Agent, Antigo, WI Departments of Plant Pathology 2 and Horticulture 3 Madison, WI Wisconsin Seed Potato Certification 4, Antigo, WI