9Th Triennial Conference of APA, Kenya, June30 - July 4, 2013

Can mineral oil protect seeds against aphid transmission of Potato virus Y?

Boukhris-Bouhachem S., Sellami H., Souissi R. & El Fahem M.

GIL

Potato Seed Problem

• PVY is the most important virus on potato

• 12% of refused production

• Decrease of the yield (40%)

• PVY is transmitted by more than 70 aphidspecies with non-persistent manner

• Emergence of virus strain decreasing thequality of potato seeds PVYNTN , PVYNW

POTATO VIRUS Y (PVY)

• Famille : Potyviridae• Genre : Potyvirus• More than 30 plant hosts

• Variability of PVY

Potato isolates

PVYO PVYC PVYN

PVYNTN

PVYNW

95% PVYNTN

PVYO

PVYNTNrec + PVYO

PVYNTNrec

PVYNTN

PVY diversity in seed potato production in Tunisia

95% PVYNTN

in the laboratory

Efficiency of transmission of 14 Vectors of PVY in Tunisia 

To evaluate the efficiency of the mineral oil with insecticides as preventive treatment to control Aphids and PVY infection of potato

OBJECTIVES

High quality of seeds

STEPS OF STUDY

1.Trapping of aphids

2.Treatments of potato (field)

3. Aphid acquisition and transmission of PVY with

oil coat plants (in laboratory)

1. Aphid sampling

• Aerial sampling:– Suction trap

• Foliage sampling :– 30 leaves every

week during the growing season

Suction trap

Cap Bon

KorbaINRATSoliman

Aerial sampling by suction trap, daily catches

- Population dynamic

- Frequency

- Risk of contamination

- Treatment decision

FOLLOWED APPROACHES

Aphid flight data

0

100

200

300

400

500

600

1/3 8/3 15/3

22/3

29/3 5/4 12/4

19/4

26/4 3/5 10/5

17/5

24/5

31/5

Dates

Aph

ids/

day

ThiamethoxamImidacloprid

Pymethrozine

Haulm destruction

2. EXPERIMENT1

treatment 1: insecticides only

treatment 2: insecticides + oil

• Experimental design: 4 repetitions, 3 treatments (T,I, P)

• Elementary plots: 625 m2 (5mx1000m) separated by1m to avoid interactions

Experimental station (Korba)

Detection of PVY on 200 tubers (may)

CT

TC

Evaluation of the weight of 100 tubers

Control of phytotoxicity

Treatment results on aphid populations and PVY infection

Mean numbers of aphid coloniesPVY infections/

200tubersInsecticides Thiamethoxam Imidacloprid Pymetrozine

Dates 7/4 14/4 21/4 12/5 28/4 5/5 12/10

Treatment 1a 9 6 25 27 13 31 9,5%

Control 1 b 35 43 215 50 102 103 12%

Treatment 2 a 21 9 12 26 15 34 2.5%

Control 2 b 66 52 193 79 89 158 4%

Treatments with different letter are significantly different (p=0.05, ANOVA)(+): positive samples by DAS-ELISA

Treatment reduction of aphids

0%

20%

40%

60%

80%

100%

Treatment 1 Treatment 2

Means followed by common letters are not significantly different at 5% level

Aphids

aa

Comparison of potato yield in the two treatments 1,2

33,2529,75 30,13

26

0

5

10

15

20

25

30

35

Control Treatment1 Control Treatment 2

Potato yield (kg)

a

a aa

to explore the possibility of acquisition and transmission of PVY by the most efficient vector Myzus persicae after the oil application on potato plants.

EXPERIMENT 2

1- Aphids : • Myzus persicae populations

2 - PVY isolates : PVYNTN on tobacco

3 – Potatoes :• TransmissionN. tabacum Xanthi -> Potatoes

Aphid transmission in the laboratory

Method of transmission

2 hours to starve 3 mn acquisition of PVYNTN

Inoculation on potato Plants tests 3 hours

Treatment DAS-ELISA après 15 jours

15 days

ELISA

Aphid feeding on infected potato and then moved on healthy plants

coated with oil

No acquisition,no transmission

Acquisition,transmission

Acquisition, notransmission

coated with oil

PVY infection

ELISA results after 15 days inoculation of healthy potato by M. persicae

Aphids that feed on infected potato treated with oil then sucking on healthy plants

Infected aphids

feeding on healthy plants treated with mineral oil

infected aphids

feeding on potato

healthy plants without oil treatment

Infected potato plants

0 (+)/40 0(+)/40 38 (+)/40

Conclusion

• Mineral oil is efficient to reduce PVY transmission when well coated

• No phytotoxicity observed on plqnt sprqyed with oil

• Application of oil have no negative effect on the yield

Future Investigations

• use of crop border

• further evaluation of the use ofbiopesticides in combination with oils

• selection of resistant plant to aphids and PVY

Thank you