2. METHODS AND RESULTS

1. Aploneura lentisci (Hemiptera: Aphididae) a new vector of PVYNTN in Tunisia Boukhris-Bouhachem S., Souissi R. National Institute of Agricultural Research of Tunisia, Plant Protection Laboratory, Rue Hédi Karray, 2049 Ariana. soribou@yahoo.fr 1. INTRODUCTION Aphids are the most important pests on potato seed production. They are phloem-feeders and responsible of the transmission of plant virus particularly the Potyvirus Y (PVY) in a non-persistent manner. Tunisian potato seeds cultivated from certified Elite seeds ‘Spunta’ (2% infection) imported from Europe, are faced to PVYNTN contamination which could downgrade the quality of these seeds (fig.1). In fact, 12% of the seed potato areas were refused because the infected plants exceeds 5% infection level, tolerated by the legislation (GIL, 2003). Among 170 taxons caught in Tunisia, fifteen aphid species were abundant in yellow pan traps and suction trap: Aphis gossypii, A. fabae, Myzus persicae, Macrosiphum euphorbiae,Aphis spiraecola, Acyrthosiphon pisum, Aphis craccivora, Aploneura lentisci, Lipaphis erysimi, Hyalopterus pruni, Rhopalosiphum padi, R. maidis, Sitobion avenae, Brachycaudus helichrysi, and B. cardui. A previous work revealed fourteen aphid species as vectors of PVYNTN, considered as the most prevalent and dangerous PVY strain (Boukhris-Bouhachem et al., 2011). All aphids previously cited, were investigated except for A. lentisci species. The objective of this research was to assess PVYNTN transmission efficiency of Aploneura aphids. The composition of suction trap catches is different markedly from yellow water trap (fig.3a), others species as Hyalopteroides humilis, Schizaphis graminum, Chromaphis sp., romelan sp. appear also abundant. The details of the A. lentisci flights began in March follow in April, and showed a maximum on May (fig. 3b). Aphid transmission experiment. Aptera of A. lentisci were collected from colonies living on Pistacia lentiscus tree (fig.4a-d) and maintained in growth chamber (23°C,16:8). The transmission test was done according to Gray (2008). Aphids were placed into Petri dishes for 120 min to starve. Afterwards, they were transferred to tobacco plants (15-20 days old) infected by PVYNTN isolate and kept for 2 minutes acquisition access period. Five aphids per plant observed to be feeding were transferred with fine-tip paint brush on 4 leaf-stage healthy tobacco N. tabacum var. Xanthi (fig.4e-f). Inoculated plants (fig.4g) were placed on hermetic cages during the inoculation access period over night. After 24 h, the aphids were killed with an insecticide. Ten days after inoculation, all plants were checked for symptoms (fig.4h) and the presence of the virus were confirmed by DAS-ELISA (Clark and Adams, 1977). a b c a b c d e f g h Figure 1. a, PVY Symptoms on ‘Spunta’; b, PVYNTN symptoms on ‘Nicola’ tuber; c, plant emergence from infected ’Nicola’ tuber. 2. METHODS AND RESULTS Alatae aphids were trapped by 12.2m suction trap and yellow water trap both placed at Soliman (36°40’40”N, 10°28’20”E) in Cap Bon region and operated since 2003. Daily catches were identified by using stereomicroscopic microscope. A. lentisci is the fourth abundant aphid species (fig.2) moving in potato field from early of April to late of May when potato is still sensitive to PVY inoculations. ENTOMOLOGY 2012, ESA 60Th Annual Meeting, November 11-14, Knoxville, Tennessee ENTOMOLOGY 2012, ESA 60Th Annual Meeting, November 11-14, Knoxville, Tennessee Fig.4. a-d, Aploneura lentisci on Pistacia lentiscus; e-h, steps of transmission experiment • lentisci was confirmed as a vector of PVYNTN (3 out of 10 plants were infected) and is reported for the first time as vector of this virus. A. lentisci have a moderate transmission rate estimated at 30% compared to 3% of M. euphorbiae a poor vector and 95% of M. persicae the most efficient vector in Tunisia (Boukhris-Bouhachem et al., 2011). Regarding to A. lentisci abundance in yellow water trap and suction trap, the PVY vector pressure is estimated at 52.2% and 51.9% respectively. A. lentisci form large colonies in Pistacia lentiscus trees and alternate with Graminea. Thus if potatoes are grown next to lentiscus forest, it may form a reservoir of vectors. Given its transmission efficiency and their abundance in potato field traps, this species seems to represent a real risk of PVYNTN spread. This should be considered when deciding the installation of seed fields. 3. CONCLUSION This work is ongoing and further data about transmission efficiency of other abundant aphids as H. humilis, S. graminum, Chromaphis sp., Uromelan sp. and Aphis sp.will help to refine the relative importance of different aphid species as PVY vectors in Tunisia to improve seed potato production. Fig.2. Most abundant aphids in yellow water trap during potato growing period in 2010 a b 4. REFERENCES Boukhris-Bouhachem S., Rouze-Jouan J., Souissi R., Glais L. and Hullé M., 2011. Transmission Efficiency of the Strain PVYNTN by Commonly Captured Aphids in Tunisian Potato Fields. Plant Pathology Journal, 10: 22-28. Clark, M.F. and Adams, A.N., 1977. Characteristics of the microplate method of enzyme-linked immunosorbent assay for the detection of plant viruses. J. Gen. Virol., 34: 475-483. GIL (Interprofessionnal Vegetable Group), 2003. Annual reports of the Gil activity including seed potato production project. Ministry of Agriculture, Tunis, Tunisia pp. 42. Gray, S. M. 2008. Aphid Transmission of Plant Viruses. Current Protocols in Microbiology. 10:16B.1.1–16B.1.10. A. lentisci abundance in suction trap Number of the most abundant aphids Phenology of seed potato production March April May Aphid species Dates Fig. 3. Daily catches in Soliman suction trap, 2010. a, Composition of the most abundant aphids; b, Number of Aploneura lentisci alatae during potato growing season