Seed Potato Certification, Disease and Pest Control

Willem SchrageNorth Dakota State Seed Department (USA)

Potatoes in the Middle East

30,0002,500Syria105,00023,000Egypt90,00023,000Algeria60,00015,000Morocco

Ha's in 2000

Ha's in 1950's

Potatoes in the Middle East

�Over the last 50 years seed potato imports remained similar: i.e.

�Local seed potatoes have increased

Planting Times in the Middle East and North Africa

� Early Imports: October-December

� Main Season : January-March

� Local Seed : Late August-October

Seed Potato Certification

Three legs:

1.Industry

2.Science

3.Enforcement

Purposes of Seed Certification

� Indication of minimum quality requirements of seed potatoes

� Marketing

� Disease Control: Legal instrument to have only seed planted of required quality (i.e. within disease tolerance)

Minimum quality requirements

� Seed potatoes shall be substantially free from injurious diseases and pests and from any defects likely to impair their quality as seed. They shall be substantially dry outside and, in general, of normal shape for the variety

Certification

�Marketing

�In many markets seed potatoes have to be certified and labelled according to a Certification Standard to be accepted by customers and authorities

Certification Standards help to:

�Facilitate Trade,

�Encourage High(er)-Quality Production,

�Improve Profitability and

�Protect Customers’ (i.e. Potato Producer’s) Interests.

Certification Components

� Regulations

� Documentation: e.g. Planting approved seed stock

� Field Inspection (for seed transmitted)

� Quality Assurance� Lot Inspections for diseases and defects

� Post Harvest Test

� Disease Testing

� Follow Up

Certification Requirements cover

Varietal identity and purity

Genealogy and traceability

Diseases and pests

Tuber quality and physiology

Sizing and labelling.

Genealogy and traceability

�An application for certification includes source and inspection reports.

�A database includes genealogy,

�Enabling to trace back seed lots from the same farm or the same source.

Varietal identity and purity

�Variety Description is available in an official list of registered varieties either for a variety to be imported or to be accepted in a seed potato program.

Diseases and pests

Tolerances are established to control introduction or spread of prescribed diseases and pests which are injurious to crops.

Including zero tolerances

Disease Control

� Reduction of inoculum by using clean seed, i.e. seed lots within the required tolerances

Two Aspects of Disease Control in Plants

� Plant Quarantine: Regulated Diseases and Pests

� Seed Certification: Regulated Non Quarantine Diseases and Pests.

Regulated Diseases and Pests(Plant Quarantine)

� International Plant Protection Convention

� North American Plant Protection Organization

� European and Mediterranean Plant Protection Organization

Regulated non-quarantine pest

� A non-quarantine pest whose presence in plants for planting affects the intended use of these plants with an economically unacceptable impact and which is therefore regulated within (an area within) a country

Zero Tolerance (“Quarantine”)

� Globodera rostochiensis

� Globodera pallida

� Synchytrium endobioticum

� Clavibacter michiganensis

� Ralstonia solanacearum

� Potato spindle tuber viroid

� Tomato stolbur

� Meloidogyne chitwoodi and fallax

� Ditylenchus destructor

Viruses

�Severe virus diseases manifest themselves by deformations of the foliage with or without discolouration. Symptoms can be rugosity, crinkle, rolling and brittleness of the leaves or dwarfing of the plant, as with the severe mosaic or/and the potato leaf roll disease..

Leaf Roll and Mosaic Viruses

PLRV,

PVY, PVA, PVM,PVY + PVX, PVA + PVX PVX + PVS.

PLRV

PVY

PVY

Virus tolerance in the field

� 0

� 0.1

� 0.4(0.2 severe)

� 0.8(0.4 severe)

� 2(1 severe)

� 10(2 severe)

� TC

� PB

� B1

� B2

� C1

� C2

Mosaic Tolerances in US in appr. B.

0.20%AK

0.25%MI, WI, USA export

0.30%MN, NE, WY, ND

0.50%WA

0.75%ID

1%CA, NY, OR

2%CO, ME

Other viruses

� Some other viruses are more or less self eliminating, which reduces the usefulness of incorporating strict tolerances for them

� However a zero tolerance for PSTVdultimately resulted in surveys where it was not found anymore in seed potatoes in North America

Field Inspections

�The number of field inspections (at least 2) is targeted towards virus, early in the season, leaf roll later

and bacterial diseases last.

Virus in Direct Progeny(%)

� 0

� 0.5

� 2 (1 severe)

� 4 (2 severe)

� 10 (5 severe)

� 10

� TC

� PB

� B1

� B2

� C1

� C2

Post Harvest Test

�Post Harvest Test may be dependent on vine kill date.

� In general when long storage season.

Field Grown Post Harvest test, Hawaii

Florida

Plants from Seed Pieces under Growth Lights

PVY under growth lights

COMPARATIVE TRIALS

� Planting should be done in plots of 100 plants. The plots should be grouped by variety so as to facilitate comparison.

� Fertilization must be moderate, especially N, to facilitate virus expression.

Visual examination

� To be accurate, the visual examination shall in general be carried out in two stages, with an interval of 10-15 days between them. Laboratory testing may support visual examination. Primary viral infections shall not be taken into consideration

Diseases and Pests

� Soil test.

� Inspection of foliar symptoms of black leg, late blight etc.

� Tuber symptoms have tolerances.

Tuber (Lot) Inspection at Shipping Point

Tuber Symptoms, i.e.Lot Tolerances

�Dry & wet rot

� (%)External defects:

�Shrivelled tubers:

�Scab (common and netted)

�Powdery scab

�Rhizoctonia

�Total tolerances(%)

� 0 - 0.2 – 1%

� 3%

� 0 – 0.5- 1%

� 0 – 5 - (33.3)%

� 0 -1 (10)- 3(10)%

� 0 - 1 (1) -5 (10)%

� 3 – 5 – 6%

Late Blight

Verticillium WiltBlack Dot

Gudmestad,NDSU

Soft Rot

�Black Leg

Pink Rot

Rhizoctonia and Powdery Scab

Common Scab

Disease Control

� Reduction of inoculum by using clean seed, i.e. seed lots within the required tolerances.

� Consideration for what is economically feasible.

Seed Cutting

� Cutting seed potatoes allows an entry point to disease organisms, and allows contamination from tuber to tuber.

� A well suberized seed piece can withstand unfavorable conditions.

Tuber Quality and Physiology

�Different growing seasons may make physiological age more important than diseases

�Physiological age (too young or too old) may have a greater influence on yield than diseases.

Sizing and labelling

�Content: "Seed potatoes"

�Certifying Agency

�Country and/or Region of Production

�Seed Lot Identification Number,

�Month and Year of Closing

�Variety

� (Category and) Class (field generation)

�Size

�Declared net weight

Declaration of meeting requirements

� Information about the quality of the load accompanying the load indicates that requirements are met by indicating class (and generation).

QUESTIONS?