b'A Different Post Harvest TestBy Kent Sather, North Dakota State Seed Department, Potato Program DirectorSeedpotatocertificationprograms utilize a number of mechanisms to ensurequalityseedisproduced withintheguidelinesandregula-tionsestablishedbythecertifying authority.Oneimportantcompo-nentisapost-harvesttest(PHT). The primary focus of this test is to detect and estimate any current sea-son spread of virus, primarily Potato Virus Y (PVY or Mosaic) and Potato LeafRollVirus(PLRV)thatmay haveoccurredduringthesummer growing season.Staff from cooperating grower Alger Farm LLC, Homestead, Florida, attempt Post-harvesttestingmaybeper- to trench and drain standing water in North Dakota winter test plots just days after planting. formedinacombinationofways. Sample lots can be grown in green- forrecertificationthefollowingregulationshaveadefaultclause. housesorfieldforinspectionandsummer.They state: In the event ofserious leaf testing. Sprouts from tuber sam- malfunctionsofthepostharvest plescanbelaboratorytestedforPlanting of the North Dakota 2021grow out test, eligibility of a seed lot viruses.ResearchisbeingdoneforCrop winter grow out proceeded onwillbebasedonthecurrentfield testing of dormant tubers.schedule in November. Immediatelyreadings, meaning if the lot passed afterplanting,however,mothersummer inspection, they would be NorthDakotahasutilizedaPHTnaturetookaturnfortheworst.eligibleforrecertificationthefol-winter grow out for over 60 years.Nearly four inches of rain fell on ourlowingsummer.Also,inlieuofa Ourplotshavebeenlocatednearplots. Weather remained cloudy andgrowout,theseeddepartmentis Homestead,Florida.Seedlotsam- cool. King tides on the ocean causedcurrentlyserologicallylaboratory plesarecollectedbyourNorthdrainageditchestobeatcapacity.testingsproutsfromprioritylot Dakotagrowersduringharvest.Thewatertablewasjust1.2footsamples. We are testing for only PVY They are delivered to North Dakotabelow the soil surface. More rain felland PLRV. This process will not be StateSeedDepartmentstaffwhoin subsequent days. The plot nevercomplete until March.record, process and eventually plantdried out. The tubers rotted in the inmid-November.Experiencedsaturated soil. We had a 100% loss.The loss of our PHT grow out plots inspectorsreturntotheplotsinhas created a challenge for our grow-early January to potato plant growthI know of one other time, roughlyersandourcertificationprogram. of about 12 to 14 inches. Every plant25yearsago,whentherewasnoHowever, we are taking measures to in each sample in the plot is inspect- North Dakota grow out. And I haveensure the continuing production of ed and counted. Any virus, varietyavaguememoryaboutaNorthqualityofseedinthefuture.One mix, or abnormality is recorded, andDakotaplotdrownoutinthelategrowers statement about the situa-apercentageofthevirusisdeter- 1980s. tionwasWemanagedthroughit mined. This is matched against cer- whenithappenedbefore.Wewill tification tolerances to determine ifBecauseofthisinfrequentoccur- get through it again. the seed lot is eligible for replantingrence,ourcertificationrulesand 22 POTATO GROWER MARCH 2022'