Accepted Manuscript. Impact of UV-A radiation on the performance of aphids and whiteflies and on the leaf chemistry of their host plants

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1 Accepted Mnuscript Impct of UV-A rdition on the performnce of phids nd whiteflies nd on the lef chemistry of their host plnts Betriz Dáder, Dyln Gwynn-Jones, Aránzzu Moreno, An Winters, Alberto Fereres PII: S (14) DOI: Reference: JPB 9774 To pper in: Journl of Photochemistry nd Photobiology B: Biology Received Dte: 18 Februry 2014 Revised Dte: 22 My 2014 Accepted Dte: 10 June 2014 Plese cite this rticle s: B. Dáder, D. Gwynn-Jones, A. Moreno, A. Winters, A. Fereres, Impct of UV-A rdition on the performnce of phids nd whiteflies nd on the lef chemistry of their host plnts, Journl of Photochemistry nd Photobiology B: Biology (2014), doi: This is PDF file of n unedited mnuscript tht hs been ccepted for publiction. As service to our customers we re providing this erly version of the mnuscript. The mnuscript will undergo copyediting, typesetting, nd review of the resulting proof before it is published in its finl form. Plese note tht during the production process errors my be discovered which could ffect the content, nd ll legl disclimers tht pply to the journl pertin.

2 1 2 Impct of UV-A rdition on the performnce of phids nd whiteflies nd on the lef chemistry of their host plnts Betriz Dáder, Dyln Gwynn-Jones b, Aránzzu Moreno, An Winters b, Alberto Fereres,* Instituto de Ciencis Agrris, Consejo Superior de Investigciones Científics. ICA-CSIC. Clle Serrno 115 dpdo., 28006, Mdrid, Spin b Institute of Biologicl, Environmentl nd Rurl Sciences, Aberystwyth University. Ceredigion, SY23 3DA, Aberystwyth, United Kingdom * Corresponding uthor. Tel.: ; fx: ; E-mil ddress:.fereres@csic.es. E-mil ddresses: betrizdder@ic.csic.es (B. Dáder), dyj@ber.c.uk (D. Gwynn-Jones), moreno@ic.csic.es (A. Moreno), lg@ber.c.uk (A. Winters),.fereres@csic.es (A. Fereres). 1

3 ABSTRACT Ultrviolet (UV) rdition directly regultes multitude of herbivore life processes, in ddition to indirectly ffecting insect success vi chnges in plnt chemistry nd morphogenesis. Here we looked t plnt nd insect (phid nd whitefly) exposure to supplementl UV-A rdition in the glsshouse environment nd investigted effects on insect popultion growth. Glsshouse grown peppers nd eggplnts were grown from seed inside cges covered by novel plstic filters, one trnsprent nd the other opque to UV-A rdition. At 10-true lef stge for peppers (53 dys) nd 4-true lef stge for eggplnts (34 dys), plnts were hrvested for chemicl nlysis nd infested by phids nd whiteflies, respectively. Clip-cges were used to introduce nd monitor the insect fitness nd popultions of the pests studied. Insect pre-reproductive period, fecundity, fertility nd intrinsic rte of nturl increse were ssessed. Crop growth ws monitored weekly for 7 nd 12 weeks throughout the crop cycle of peppers nd eggplnts, respectively. At the end of the insect fitness experiment, plnts were hrvested (68 dys nd 18-true lef stge for peppers, nd 104 dys nd 12-true lef stge for eggplnts) nd leves nlysed for secondry metbolites, soluble crbohydrtes, mino cids, totl proteins nd photosynthetic pigments. Our results demonstrte for the first time, tht UV-A modultes plnt chemistry with implictions for insect pests. Both plnt species responded directly to UV-A by producing shorter stems but this effect ws only significnt in pepper whilst UV-A did not ffect the lef re of either species. Importntly, in pepper, the UV-A treted plnts contined higher contents of secondry metbolites, lef soluble crbohydrtes, free mino cids nd totl content of protein. Such chnges in tissue chemistry my hve indirectly promoted phid performnce. For eggplnts, chlorophylls nd b, nd crotenoid levels decresed with supplementl UV- A over the entire crop cycle but UV-A exposure did not ffect lef secondry metbolites. However, exposure to supplementl UV-A hd detrimentl effect on whitefly development, fecundity nd fertility presumbly not medited by plnt cues s compounds implied in pest nutrition -proteins nd sugrs- were unltered Keywords: Plnt-insect interctions; UV-blocking covers; Insect pests; Pepper; Eggplnt Highlights: Supplementl UV-A cuses reduction in pepper stem height Aphids benefit from chnges in pepper metbolites under supplementl UV-A There is detrimentl effect of UV-A rdition on whitefly performnce UV-medited chnges pper to be highly dependent on ech plnt-insect complex 2

4 Introduction Aphids nd whiteflies re two of the most importnt pests worldwide, not only becuse of the direct dmge they cuse, but lso becuse their limentry hbits involve trnsmission of plnt viruses (Hull, 2002). Ultrviolet (UV) rdition plys mjor role in herbivores, including insect pests, by modifying their orienttion towrd potentil hosts, flight ctivity, lighting, rrestment, feeding behvior nd interction between sexes (Rviv nd Antignus, 2004; Johnsen et l., 2011). Aphids (Hemipter: Aphidide) nd whiteflies (Hemipter: Aleyrodide) re mong the most studied insects concerning their flight behviour. Aphids hve been reported to reduce their flight ctivity nd bility to disperse in UV-deficient environments (Díz nd Fereres, 2007; Döring nd Chittk, 2007). Moreover, decrese in fecundity nd popultion density hs been lso demonstrted (Antignus et l., 1996; Chyzik et l., 2003; Díz et l., 2006; Kuhlmnn nd Müller, 2009; Pul et l., 2011; Legrre et l., 2012). Conversely, UV rdition stimultes whitefly migrtion (Mound, 1962; Coombe, 1982). Among new integrted pest mngement strtegies, UV-bsorbent photoselective nets hve been successfully tested in field situtions by reducing the impct of insect vectors nd plnt pthogens on protected crops (Díz nd Fereres, 2007; Weintrub, 2009; Legrre et l., 2012). Knowledge on the effects of UV-B on plnt growth nd chemistry (nutritionl chrcteristics relevnt to insects) hs been developed due to pst concerns bout ozone depletion (Bllré et l., 1996; Hunt nd McNeil, 1999; Mckerness, 2000; Jnsen, 2002; Comont et l., 2012; Mewis et l., 2012). In contrst, understnding of the effects of the UV-A frction of the solr spectrum on plnts nd insect pests is very limited. Whilst UV-A rdition is unffected by ozone depletion, it is significnt component of the solr spectrum ffected by ltitude, ltitude nd cloud cover. It is lso often bsent from the glsshouse/horticulturl environment. New environmentl concerns suggest tht understnding UV-A impcts on plnts could be importnt given tht predictions by the United Ntions Environment Progrmme suggest tht there will be higher incidence of cloud free periods, prticulrly in southern Europe nd the Mediterrnen Bsin. This will result in higher exposure of crops to mbient UV-A rdition (WMO, 2010). Only few uthors hve considered UV-A impcts on plnt growth (Tezuk et l., 1994; Jykumr et l., 2003, 2004; Verdguer et l., 2012). The ltter work shows tht rdition in the UV-A rnge produces ltertions in lef morphology nd ntomy of severl plnts, with the most chrcteristic response minly observed in the dxil epiderml cells, which were thicker nd longer thn those grown without UV-A. There re no known studies tht hve focused on how UV-A influences the reltionship between phytophgous insects nd their plnt hosts but there is lrge body of mteril published on UV-A plnt pollintor interctions (Stephnou et l., 2000; Petropoulou et l., 2001; Dyer nd Chittk, 2004). Furthermore, reserch on spider mites by Ski nd Oskbe (2010) concluded tht Tetrnychus urtice Koch (Acri: Tetrnychide) exploits UV-A informtion to void mbient UV-B rdition. At the sme time other work on Pnonychus citri McGregor (Acri: Tetrnychide) suggested tht eggs were tolernt to UV-B rdition 3

5 nd femles successfully oviposited on the upper side of leves exposed to UV-B vi rtificil lmps (Fuky et l., 2013). Our knowledge on the effects of UV-B on plnt-insect interctions would suggest tht typicl plnt responses would include the ccumultion of UV-screening metbolites, incresed lef thickness nd trichome density or reduction in cell elongtion (Smith et l., 2000; Pul nd Gwynn-Jones, 2003; Liu et l., 2005; González et l., 2009; Kulhmnn nd Müller, 2009). These impcts hve implictions for host success becuse such physicl nd biochemicl trits ffect host cceptnce nd success of future insect progeny (Vänninen et l., 2010; Pul et l., 2011) Understnding of the indirect effects of UV-A on insects vi plnts remins limited to wht we know bout current prctices in horticulture. On one hnd, the horticulture industry trditionlly grows crop species under glss or plstic with opque or lowered UV rdition environments. However, evidence suggests tht supplementl UV-A my improve plnt growth, yield nd qulity. For exmple, combintion of visible rdition nd UV-A t prticulr rtio my be highly suitble for enhnced growth of soyben seedlings (Middleton nd Termur, 1993). Similr findings hve been observed on the yield of Phseolus mungo L., which ws improved with UV-A exposure (Jykumr et l., 2003). UV cldding mterils hve been shown to lso hve positive effects on crop growth by incresing stem length, lef toughness or trichome density (Hunt nd McNeil, 1999; Kitts et l., 2006; Kuhlmnn nd Müller, 2009, 2010; Pul et l., 2011). There is lso evidence tht UV trnsmitting environments could produce food plnts commercilly with incresed humn helth benefits (Tsormptsidis et l., 2011). In this study, we hypothesise tht UV-A is centrl to the trophic reltionships between these two globl pests -phids nd whiteflies- nd their plnt hosts. We grew the horticulturl hosts Cpsicum nnuum L. (pepper) nd Solnum melongen L. (eggplnt) nd their respective insect pests, the green pech phid Myzus persice Sulzer (Hemipter: Aphidide) nd the whitefly Bemisi tbci Genndius (Hemipter: Aleyrodide) in the presence nd bsence of UV-A rdition. We trgeted how UV-A impcts the success of insects vi popultion growth. In tndem with direct effect of UV-A, we lso ssessed how UV-A exposure indirectly ffects insects vi chnges in plnt chemistry. Correltions between the different responses found in lef chemicls nlysed nd plnt sensitivity to UV-A re considered Methods nd mterils 2.1. Plnt propgtion Experiments were undertken in glsshouse fcility t the Institute of Agriculturl Sciences of CSIC (Mdrid, Spin) ( N, W) t temperture of 23:20±2 C (dy:night), photoperiod of 14:10 (light:drk) nd 70-80% RH. C. nnuum cv Cliforni Wonder (Rmiro Arnedo S.A., L Rioj, Spin) nd S. melongen cv Blck beuty (Btlle, S.A., Brcelon, Spin) seeds were germinted in pots with mixture of soil:vermiculite 4

6 (1:1). For both species, three seeds were plced in ech pot nd thinned to one post germintion. Plnts were wtered three times week using (N:P:K) Nutrichem 60 fertiliser (Miller Chemicl & Fertilizer Corp., Pennsylvni, USA) t dose of 0.25 g L UV-A tretments UV-A rdition ws supplied by two Osrm Ultr-Vitlux UV lmps (Osrm GmbH, Munich, Germny). Lmps were switched on nd off with no grdul trnsition for photoperiod of 14 hours every dy throughout the entire length of experiments. The lmps emitted no UV-C rdition nd produced rdition levels representtive of typicl sunny summer dy conditions in the centre of the Iberin Peninsul (Gutiérrez-Mrco et l., 2007; Häder et l., 2007). However, it should be emphsised tht our im here ws to expose plnts nd insects to UV-A under glsshouse conditions rther tht simulte UV-A outdoors. The lmps used were hevily weighted for UV-A emission so throughout the text we will refer to the tretment s UVA+ (supplementl UV-A). A set of two 1 x 1 x 1m (L x H x W) cges were covered by filters. As positive control tht llowed UV-A rdition trnsmission but blocked UV-B rdition (Tble 1), the upper side of one cge ws covered with 200 µm thickness film (Solplst S.A., Murci, Spin). The four lterl sides were covered to 50 cm height with UV-trnsprent net T 50 mesh (Polysck Plstic Industries Ltd., Nir Yitzhk, Isrel) to permit irflow inside the cge. The remining upper 50 cm were covered with plstic film. For the suppressed UV-A rdition tretment, 200 µm thickness Antivirus UVblocking film (Solplst S.A., Spin) nd UV-bsorbing Optinet 50 mesh (Polysck Plstic Industries Ltd., Nir Yitzhk, Isrel) were used. Opticl properties (trnsmitted rdition) of the UV-opque nd UV-trnsprent films were nlysed t the CSIC Torres Quevedo Institute (Mdrid, Spin) using double monochromtor Lmbd 900 UV/Visible/NIR spectrophotometer (PerkinElmer Life nd Anlyticl Sciences Ltd., Connecticut, USA). The min difference between both filters ws tht the UV-opque film blocked UV-A trnsmission ( nm) nd the UV-trnsprent film llowed UV-A trnsmission, s seen in Figure 1. Lmps were hung t distnce of 1 m bove the plnt cnopy. Irrdince per second ws mesured dily bove cge nd t cnopy level s well s on the bxil side of the leves nd through the leves with clip-cges where insects were monitored with n ALMEMO 25904S rdiometer (Ahlborn GmbH, Holzkirchen, Germny). The rdition received by the plnts (irrdince) under both tretments is shown in Tble 1. The UV dily doses were KJ m -2 d -1 UV-A nd 0.55 KJ m -2 d -1 UV-B for tretment UVA+, nd 1.76 KJ m -2 d -1 UV-A nd 0.10 KJ m -2 d -1 UV-B for tretment UVA-. Dily UV-A rdition inside the cge covered by the blocking film ws very low (1.76 KJ m -2 d -1 ) hence this tretment ws clled UVA- (ner zero UV-A). A fourty-fold increse in UV-A trnsmittnce t the plnt cnopy level inside the regulr cge ws mesured when compred to the cge covered by the UV-bsorbing brrier (1.422 vs W m -2 ) (Tble 1). Low levels of UV-B rdition inside both experimentl tretments were detected lthough represented less thn 1% of the light received by our plnts (0.011 W m -2 in tretment UVA+ nd W m -2 in tretment UVA-) (Tble 1). It should gin be noted tht the experimentl set up ws used to evlute how supplementl UV-A ffects plnt-insect interctions nd performnce in the glsshouse environment. The 5

7 focus ws on crop production nd this study ws not designed to simulte outdoor environmentl conditions, hence ny extrpoltion of findings to field conditions should be done with cution. 179 Tble 1. Rdition conditions t cnopy level outside nd inside the experimentl cges 180 (UVA+ nd UVA- tretments), on the bxil side of the leves nd through the leves with 181 clip-cges where insects were monitored. Trnsmission percentges represent rdition 182 trnsmitted inside both cges in reltion to the sme level outside cges. 183 Tretment UVA+ Tretment UVA- PAR UV-A b UV-B b PAR UV-A UV-B Cnopy level outside cge (112.8) (110.6) Cnopy level inside cge (96.8) (73.3) Abxil side of leves w/ clipcge 25.3 (5.5) (4.8) Through the leves w/ clipcge Trnsmission inside cge (%) µmol m -2 s -1 (W m -2 ), b W m Figure 1. Totl trnsmittnce from 250 to 750 nm of the UV-trnsprent (UVA+) nd UVopque (UVA-) plstic films mesured by double monochromtor spectrophotometer Insect exposure nd mintennce M. persice ws continuously rered on pepper plnts in climte chmber t 23:18 C (dy:night), 60-80% RH, nd photoperiod of 16 h nd B. tbci Q biotype ws rered on eggplnts in greenhouse fcilities t n verge temperture of 23:20 C (dy:night), 70-80% 6

8 RH nd photoperiod of 16 h. Both species were synchronised prior to ssys to ensure tht individuls were the sme ge Aphid introduction Pepper plnts were infested by M. persice t the 10-true lef stge. One single wingless phid dult ws plced in clip-cge on the bxil side of the youngest fully developed lef of ech pepper plnt nd llowed to produce nymphs for 24 hours. Surplus nymphs were removed leving three nymphs per plnt, which were monitored until dulthood stge. When the first nymph reched the dult stge, the other two were removed. Offspring from the remining insect ws monitored by removing nymphs dily for n equl number of dys to the pre-reproductive period. The prmeters pre-reproductive period (d), effective fecundity (Md), intrinsic rte of nturl increse (r m =0.738*(log e Md)/d), men reltive growth rte (RGR=r m /0.86) nd men genertion time (Td=d/0.738) were clculted (n=19) Whitefly introduction Eggplnts were infested by whiteflies t the 4-true lef stge. Ten pirs of dult whiteflies were left to produce eggs inside clipcges on the bxil side of the youngest fully developed lef of ech plnt for 24 hours nd 10 eggs were monitored until dult emergence. A newborn femle nd mle were plced on new lef nd their offspring monitored for 30 dys. Prereproductive period, lrve vibility, femle fecundity nd fertility were studied (n=16) Experimentl design Pots with seeds were plced inside cges nd plnts were grown from seeds under two different rdition regimes, either with supplementl (UVA+) or ner zero UV-A rdition (UVA-). At 10-true lef stge (53 dys) for peppers nd 4-true lef stge (34 dys) for eggplnts, hlf of the plnts of ech cge were moved from the UVA+ to the UVA- tretment nd vice vers. Some of the plnts were infested by phids (n=19) or whiteflies (n=16) to study the performnce of insects. In this wy, we hd four UV-A tretments: positive control UVA+/UVA+, plnts grown under supplementl UV-A rdition for the entire growth cycle; negtive control UVA-/UVA-, plnts grown t ner zero UV-A rdition for the entire growth cycle; UVA+/UVA-, plnts grown under supplementl UV-A rdition before insect introduction nd t ner zero UV-A fter insect introduction; nd UVA-/UVA+, plnts grown t ner zero UV-A rdition before insect introduction nd under supplementl UV-A fter insect introduction. Figure 2 represents timeline digrm of the experimentl procedure. Stem height, nd lef length nd width were monitored weekly using ruler (n=6). The reltionship between our mesurements nd ctul lef re (cm 2 ) ws clculted by scnning 10 leves of different stges of ech plnt species nd contouring them with Adobe Acrobt softwre (Pepper: 0.66±0.01. Eggplnt: 0.73±0.01). Experiments were repeted twice over one yer. Lef mteril hrvested throughout the experiment ws either snp-frozen nd mintined t -80 C or ir-dried 70 C s relevnt for further nlyses. Figure 2. Timeline digrm of the experimentl design, showing the four different UV-A tretments (T1: UVA+/UVA+, plnts grown under supplementl UV-A rdition for the 7

9 entire growth cycle; T2: UVA+/UVA-, plnts grown under supplementl UV-A rdition before insect introduction nd ner zero UV-A fter insect introduction; T3: UVA-/UVA+, plnts grown ner zero UV-A rdition before insect introduction nd under supplementl UV-A fter insect introduction nd T4: UVA-/UVA-, plnts grown ner zero UV-A rdition for the entire growth cycle), dtes of insect infesttion to study the performnce of phids nd whiteflies nd plnt hrvests for peppers nd eggplnts. The rrows refer to the moment when hlf of the plnts of ech tretment were moved from tretment UVA+ to UVA- nd vice vers. 241 UVA+ (pepper: n=56, eggplnt: n=50) UVA- (pepper: n=56, eggplnt: n=50) UVA+ (pepper: n=25, eggplnt: n=22) UVA- (pepper: n=25, eggplnt: n=22) UVA+ (pepper: n=25, eggplnt: n=22) UVA- (pepper: n=25, eggplnt: n=22) T1 T2 T3 T4 242 Time (dys) Sowing 0 0 First hrvest (n=6) Insect introduction Second hrvest (n=6) Pepper 68 Eggplnt Plnt hrvesting Plnts from the two species were hrvested t two different growth stges for determining biomss nd content of chemicl compounds (Figure 2). Plnts were hrvested from ech of the tretment cges t the 10-true lef stge (53 dys fter sowing) for peppers plnts nd 4- true lef stge (34 dys fter sowing) for eggplnts (n=6). All leves from ech plnt were collected for subsequent chemicl nlyses. Further plnts from the tretments were hrvested t 18-true lef stge for peppers (68 dys fter sowing) nd t 12-true lef stge for eggplnts (104 dys fter sowing). This involved plnts from ech tretment including those infested with insects nd those not (s bove, n=6) Plnt biochemicl nlysis Secondry metbolites Frozen smples were subsequently freeze-dried for 48 hours nd lef mteril homogenised with pestle nd mortr. Smples were nlysed for secondry metbolites by extrction in 70% methnol of freeze-dried smples (100 mg), s described by Comont et l. (2012). Superntnts were dried using Svnt SpeedVc SPD121P vcuum centrifuge (Thermo Scientific, Msschusetts, USA) before re-suspension in 500 µl 70% methnol. The solidphse extrction ws performed using Sep-Pk Vc 500 mg C18 column (Wters Ltd., Elstree, UK) before vcuum centrifugtion of the smple to complete dryness. Dried pellets 8

10 were suspended in 500 µl 100% methnol nd nlysed vi high pressure liquid chromtogrphy (HPLC) with system comprising Wters 515 pump, Wters 717plus utosmpler, Wters 996 photodiode rry detector nd Wters C 18 Nov-Pk rdil compression column (C µm, 8.0x100mm crtridge) (Wters Ltd., Elstree, UK) with n injection volume of 30 µl nd flow rte of 2 ml min -1. The mobile phse consisted of 5% cetic cid (solvent A) nd 100% methnol (solvent B) with liner grdient from 5 to 75%, B in A, over 35 min. Pek integrtion ws performed using the Empower softwre. Liquid chromtogrphy-mss spectrometry (LC-MS) ws performed to identify the mjor compounds. A Thermo Finnign LC-MS system (Finnign Surveyor LC pump plus, PDA plus detector, Finnign LTQ liner ion trp) (Thermo Scientific, Msschusetts, USA) nd Wters Nov-Pk C µm, 3.9x100 mm column ws used with n injection volume of 10 µl nd flow rte of 1 ml min -1. The mobile phse consisted of purified wter-0.1% formic cid (solvent A) nd MeOH-0.1% formic cid (solvent B) with liner grdient from 5 to 65%, B in A, over 60 min. Phenolics were chrcterised by UV bsorption spectr, MS frgmenttion ptterns in negtive ion mode nd comprison with stndrds nd previously reported dt in the literture (Clifford et l., 2003; Stommel et l., 2003; Mrín et l., 2004; Prk et l., 2012) Soluble sugrs Air dried smples (100 mg) were extrcted in 3 ml of distilled wter t 80 C three times. Extrcts were centrifuged for 10 min t 10,000 rpm. Superntnts were retined, combined nd frozen until the nlysis. Then 50 µl of smple were dded to 950 µl of buffer comprising 5 mm H 2 SO 4 with 5 mm crotonic cid internl stndrd. Smples were nlysed vi HPLC comprising Jsco LG ternry grdient unit, Jsco PU-1580 pump, Jsco AS-1555 smpler nd Jsco RI-2031 detector (Jsco Ltd., Essex, UK). Injection volume ws 25 µl. Sugrs were identified by comprison with n internl librry of stndrd compounds (Comont et l., 2012) Free mino cid nd proteins Freeze-dried plnt mteril (100 mg) ws extrcted in 4 ml of boiling distilled wter for 25 minutes. Extrcts were llowed to cool nd 1.5 ml liquot ws centrifuged to clrify the solution, following the methodology described by Winters et l. (2002). Amino cid bsorbnce ws mesured t 570 nm using n Ultrospec 4000 UV/Vis spectrophotometer (GE Helthcre, Buckinghmshire, Englnd). Histidine ws used for the clibrtion curve s most mino cids hve the sme response. Totl proteins were extrcted from 100 mg of freezedried smple by grinding in 1.8 ml Mclivine buffer ph 7 contining 50 mm scorbic cid, nd 0.2 ml 20% lithium dodecyl sulphte. Protein content ws nlysed by the Lowry protein ssy (Lowry et l., 1951) following precipittion of protein in extrcts with 20% trichlorocetic cid, 0.4% phosphotunstic cid nd resuspension in 0.1 M NOH. Absorbnce ws mesured t 700 nm with µqunt microtitre plte reder spectrophotometer (Bio-Tek Instruments Inc., Winooski, USA). Protein contents were determined ginst bovine serum lbumin clibrtion curve Photosynthetic pigments 9

11 Chlorophyll, chlorophyll b, chlorophylls +b nd crotenoid contents were nlysed in freeze-dried smple extrcts. Lef mteril (50 mg) ws extrcted in 80% cetone nd superntnts were diluted 1:15 in 80% cetone with bsorbnce mesured t 470, 646.6, nd 750 nm using n Ultrospec 4000 UV/Vis spectrophotometer (GE Helthcre, Buckinghmshire, Englnd). Pigment contents were determined using equtions by Lichtenthler (1987) nd Porr et l. (1989) Dt nlysis nd sttistics Dt were trnsformed when necessry with either (x + 0.5), x 2, Ln (x + 1) or 2*rcsin x in the cse of percentge dt to decrese heteroscedsticity nd improve norml distribution. All the prmeters were then nlysed using IBM Sttistics SPSS 21.0 softwre (SPSS, 2013) with one-wy ANOVA followed by t-test (p 0.05) to ssess differences prior to exchnge of plnts or pirwise comprison for lest significnt differences (LSD) (p 0.05) to test differences fter the exchnge of plnts. If dt did not follow norml distribution, nonprmetric Kruskl-Wllis H or Mnn-Whitney U test (p 0.05) ws performed. Stem height nd lef re over the crop cycle (repeted mesures over time) were ssessed with ANOVA univrite repeted mesures nlysis (p 0.05) using SuperANOVA v softwre for Mcintosh (Abcus Concepts, 1989). 3. Results 3.1. Plnt height nd lef re Addition of UV-A to pepper plnts over the entire plnt growth cycle (UVA+/UVA+) cused significnt reduction in plnt height (Tretment: F=15.399, 3 df, p< Time: F= , 6 df, p< Time x Tretment: F=7.311, 8 df, p<0.001). By 68 dys, plnts grown with supplementl UV-A were 57% shorter compred to plnts grown t ner zero UV-A (23.9 cm vs cm) (Supplementry Figure 1). Pepper lef re ppered lower with UV-A but not significntly different (Tretment: F=2.618, 3 df, p= Time: F= , 6 df, p< Time x Tretment: F=1.271, 8 df, p=0.267) when compred to the ner zero UV-A tretment (Supplementry Figure 1). Eggplnts exposed to UV-A were shorter from 84 dys onwrds lthough not significntly (Tretment: F=0.018, 3 df, p= Time: F= , 11 df, p< Time x Tretment: F=1.575, 29 df, p=0.042). By the end of the experiment, plnts exposed to supplementl UV- A during their entire cycle were 23% shorter thn plnts tht hd been grown t ner zero UV-A (50.5 cm vs cm) (Supplementry Figure 1). For lef re no significnt effects were observed with UV-A (Tretment: F=0.191, 3 df, p= Time: F= , 11 df, p< Time x Tretment: F=1.528, 29 df, p=0.054) (Supplementry Figure 1). Lter ddition of UV-A when insects were introduced to plnts (53-68 dys for phids nd dys for whiteflies) did not lter the height or lef re responses observed bove. 10

12 Insect responses For phids, the pre-reproductive period (d) from birth to dult stge ws similr in ll tretments (H=2.656, 3 df, p=0.448) (Tble 2). However, effective fecundity (Md) ws significntly higher (F=2.888, 70(3) df, p=0.042) in erly supplementl UV-A tretment scenrio compred to the ner zero UV-A tretment (UVA-/UVA-) (Tble 2 nd Figure 3). This ltter tretment lowered intrinsic rte of nturl increse (r m : F=2.974, 70(3) df, p=0.037) s well s men reltive growth rte (RGR: F=2.974, 70(3) df, p=0.037) when compred to pepper plnts exposed to UV-A during erly growth (UVA+/UVA-, Tble 2). UV-A tretment fter insect infesttion hd no effects on phid fecundity nd development (Figure 3). The response of whiteflies to UV-A exposure ws different to tht of phids. The prereproductive period (d) from birth to dult stge ws significntly shortened by two dys (H=10.409, 3 df, p=0.015) t ner zero UV-A during insect development on plnts (UVA- /UVA- nd UVA+/UVA-) (Tble 2). Direct exposure of whiteflies to supplementl UV-A on plnts rised t ner zero UV-A (UVA-/UVA+) significntly lowered fecundity -egg numbers- compred to ll other tretments (F=13.256, 60(3) df, p<0.001) (Tble 2 nd Figure 3). Moreover, egg numbers were significntly lower in tretments UVA+/UVA+ nd UVA- /UVA+, 47% nd 123% respectively, when compred to insects mintined on plnts rised t ner zero UV-A over the entire experiment (UVA-/UVA-). Supplementl UV-A exposure lso lowered egg fertility (F=6.254, 60(3) df, p=0.001) (Tble 2). This resulted in significntly lower (F=14.380, 60(3) df, p<0.001) number of lrve in the tretments where insects were exposed to UV-A, regrdless of the previous conditions in which eggplnts were rised (tretments UVA+/UVA+ nd UVA-/UVA+, Tble 2). UV-A tretment fter insect infesttion hd negtive impct on whitefly fecundity, fertility nd development (Figure 3). Tble 2. Life prmeters of Myzus persice nd Bemisi tbci rised under four different UV-A rdition regimes. Different letters stnd for sttisticl differences (p 0.05). Insect Prmeters UVA+/UVA+ UVA-/UVA- UVA+/UVA- UVA-/UVA+ M. d 8.89± ± ± ±0.15 perscie Md b 37.53±2.57 b 29.71±2.41 c 39.32± ±3.18 bc Td c 12.05± ± ± ±0.20 d r m 0.298±0.006 b 0.284±0.007 b 0.310± ±0.010 b RGR e 0.346±0.007 b 0.330±0.008 b 0.361± ±0.011 b B. Vibility f 72.43± ± ± ±6.61 tbci d 26.99± ±0.48 b 24.66±0.46 b 26.94±0.84 No. eggs 78.69±8.12 b ± ±8.72 b 51.88±5.58 c No. lrve 50.69±7.22 b 87.44± ± ±3.25 c Fertility f 60.30±4.91 b 73.48± ± ±4.23 b dys, b effective fecundity, c men genertion time, d intrinsic rte of nturl increse, e men reltive growth rte, f % Figure 3. Comprison between M. persice nd B. tbci fecundity, showing the number of 11

13 nymphs nd eggs per femle on peppers nd eggplnts, respectively, under four different UV- A rdition regimes. Brs refer to stndrd errors nd different letters stnd for sttisticl differences (p 0.05). Fecundity (no. nymphs or eggs femle -1 ) b UVA+/UVA+ UVA-/UVA- UVA+/UVA- UVA-/UVA+ c bc M. persice B. tbci 3.3. Biochemicl responses to plnt nd insect UV-A exposure Secondry metbolites HPLC nd LC-MS nlysis reveled tht there were two hydroxycinnmic cids nd four flvonoids identifible in pepper leves. Anlysis of eggplnts reveled phenolics belonging to three clsses (chlorogenic cid isomers, hydroxycinnmic cid mide conjugtes nd isochlorogenic cid isomers), s well s 3-O-feruloylquinic cid, which were determined bsed on HPLC elution times, UV spectr nd LC-MS frgmenttion dt (Supplementry Tble 1). Two kempferol-hexosides with UV bsorption mxim t 265 nd 349 nm were lso identified on the bsis of their MS 2, however signls were too low to permit effective quntifiction of these compounds. Secondry metbolites were incresed in peppers by longer term UV-A exposure (68 dys) but this depended on time of hrvest nd whether plnts were simultneously exposed to insects. Totl content ws similr under both UV-A regimes t 53 dys (t=0.947, 10 df, p=0.366) (Figure 4). However, when plnts were hrvested t 68 dys, the four min flvonoid contents of pepper plnts previously exposed to UV-A nd lter moved to ner zero UV-A regime (UVA+/UVA-) were comprble to levels found in those tht hd been grown entirely without UV-A rdition (UVA-/UVA-). This implies tht phenolic expression declined when UV-A rdition ws withdrwn. Pepper plnts grown initilly without UV-A nd subsequently trnsferred to UV-A (UVA-/UVA+) lso showed phenolic levels tht were significntly higher thn plnts continuously grown under supplementl UV-A (UVA+/UVA+) (Compound 2: F=3.987, 20(3) df, p= Compound 3: F=5.229, 20(3) df, p= Compound 4: F=11.145, 20(3) df, p< Compound 5: F=20.618, 20(3) df, p< Compound 6: F=35.214, 20(3) df, p< Totl: F=29.945, 20(3) df, p<0.001) (Figure 4). Results for pepper suggest rpid cclimtion to UV-A with phid introduction b b c 12

14 nd dmge influencing flvonoid profiles, s significntly higher levels were found in plnts exposed to supplementl UV-A erly but withdrwn from this tretment (UVA+/UVA-) (Compound 4: F=4.632, 20(3) df, p= Compound 5: F=7.755, 20(3) df, p= Compound 6: F=7.884, 20(3) df, p= Totl: F=10.546, 20(3) df, p<0.001) (Figure 4). N-cffeoylputrescine content in both uninfested nd infested plnts did not differ significntly. Addition of UV-A rdition did not ffect eggplnt phenolic expression fter the first hrvest (34 dys) prior to whitefly infesttion (t=0.697, 10 df, p=0.502) (Figure 4). In contrst to pepper plnts, eggplnt phenolic compounds were unffected by tretment over the durtion of the experiment (F=0.306, 20(3) df, p=0.821) (Figure 4). As seen in Figure 4, whitefly infesttion did not pper to influence these ptterns (F=0.193, 20(3) df, p=0.900). Figure 4. Totl phenolic () nd soluble crbohydrte content (b) of pepper nd eggplnt leves grown under four different UV-A rdition nd two herbivore regimes, nd hrvested t two dtes. Brs refer to stndrd errors nd different letters stnd for sttisticl differences (p 0.05). µg phenolics g -1 dry weight Pepper b c Aphid- b Aphid+ µg phenolics g -1 dry weight Eggplnt Whitefly- Whitefly+ b Age (dys) Age (dys) 426 mg crbohydrtes g -1 dry weight b b Aphid Age (dys) b b b Aphid+ mg crbohydrtes g -1 dry weight UVA+/UVA+ UVA-/UVA- UVA+/UVA- UVA-/UVA+ Whitefly Age (dys) Whitefly+ 13

15 Soluble crbohydrtes Dt showed different crbohydrte profiles with species nd tretments. Polymer content ws similr under ll tretments t ny hrvest time for both species. Polymer content ws very high in eggplnt leves. Significntly lower levels of totl non-structurl sugrs (rffinose, sucrose, glucose nd fructose) were observed in uninfested pepper plnts grown under tretment UVA+/UVA+ t 68 dys (F=3.484, 20(3) df, p=0.035). Rffinose nd glucose in prticulr were significntly higher following tretment UVA-/UVA+ (Rffinose: F=3.440, 20(3) df, p= Glucose: F=5.365, 20(3) df, p=0.007). For infested plnts, totl non-structurl levels were similr (F=1.205, 20(3) df, p=0.334) lthough sucrose content ws significntly higher in tretments where phids were grown under supplementl UV-A (F=3.227, 20(3) df, p=0.044). No differences were found t ny dte in eggplnt nonstructurl sugrs. When totl sugr content ws nlysed, UVA+/UVA+ level ws lowest in uninfested peppers (F=4.622, 20(3) df, p=0.013) but highest in infested plnts (F=3.402, 20(3) df, p=0.038) (Figure 4b). Crbohydrte levels under herbivory were lower thn those observed in uninfested peppers possibly due to phid feeding (Figure 4b). Conversely, no differences were found mong tretments on eggplnts smples both uninfested nd infested by whiteflies (Figure 4b) Free mino cid nd proteins At 53 dys, pepper plnts exposed to supplementl UV-A hd significntly higher levels of free mino cids (t=2.755, 10 df, p=0.020). However, this trend ws not significnt t 68 dys in uninfested peppers (F=1.871, 20(3) df, p=0.167) (Figure 5). Infested plnts hd lower level compred to uninfested plnts possibly due to in situ phid feeding ctivity but no differences could be found between different rdition regimes (F=0.609, 20(3) df, p=0.617) (Figure 5). A similr pttern ws observed for totl protein content with significntly higher mount in plnts continuously grown under supplementl UV-A t 68 dys (F=15.062, 20(3) df, p<0.001) (Figure 5b). No differences were observed between tretments in eggplnts for free mino cids (34 dys: t=0.291, 10 df, p= dys uninfested: F=0.255, 20(3) df, p= dys infested: F=0.217, 20(3) df, p=0.883) nd totl proteins (34 dys: t=0.245, 10 df, p= dys uninfested: F=0.783, 20(3) df, p= dys infested: F=1.634, 20(3) df, p=0.213) when exposed to UV-A nd/or feeding by whiteflies (Figure 5 nd b). Figure 5. Free mino cids expressed s histidine () nd totl protein (b) content of pepper nd eggplnt leves grown under four different UV-A rdition nd two herbivore regimes, nd hrvested t two dtes. Brs refer to stndrd errors nd sterisks stnd for sttisticl differences (p 0.05). 14

16 Photosynthetic pigments There ws no significnt effect of UV-A exposure on pepper plnt photosynthetic pigments either t ny hrvest time or under phid herbivory (Supplementl Tble 2). In contrst, eggplnt leves exposed to supplementl UV-A hd lower chlorophyll content rdition t 34 dys (Chlorophyll : t=-2.531, 10 df, p= Chlorophylls +b: t=-2.426, 10df, p=0.036) nd under whitefly infesttion t 104 dys (Chlorophyll : F=4.613, 20(3) df, p= Chlorophyll b: F=3.887, 20(3) df, p= Chlorophylls +b: F=4.994, 20(3) df, p=0.010) (Supplementl Tble 2). Crotenoids lso showed significnt ccumultion t ner zero UV- A (34 dys: t=-2.630, 10 df, p= dys uninfested: F=3.803, 20(3) df, p= dys infested: F=4.467, 20(3) df, p=0.015). Contents were highest for tretment UVA-/UVAnd mixed tretments where plnts received both rdition regimes hd intermedite contents (Supplementl Tble 2). Chl /b rtio ws sttisticlly equl in ll tretments, rnging from 2.3 to 2.5 in peppers nd from 2.7 to 2.9 in eggplnts. 4. Discussion In the present work we investigted the effects of UV-A rdition on two key globl pests, the phid M. persice nd whitefly B. tbci nd their host plnts, pepper nd eggplnt. Our im ws to determine how UV-A in the glsshouse environment influences plnt growth nd chemistry, nd insect performnce. This work ws undertken in cges plced in glsshouse 15

17 fcility where plnts received UV-A rdition vi rtificil lmp sources. Although the glss of the fcility nd filter-covered cges bsorbed considerble mount of rdition we cnnot neglect t lest some nturl UV reching the plnts. In prticulr higher UV:PAR rtio my hve occurred t the strt nd end of ech dy becuse lmps were lredy switched on erly in the morning nd fter sunset. These diurnl chnges in the UV:PAR rtio might hve influenced plnt chemistry nd insect response. However, UV irrdince reching the plnt cnopy ws predominntly originting from the lmps (70 %) becuse sunlight ws prtilly filtered by greenhouse glss. Most (99%) of the UV rdition received by plnts nd insects in the UVA+ tretment ws UV-A. However, we must cknowledge the possibility of smll mount of UV-B irrdince, well below mbient UV-B levels, present during our experiments (Tble 1). Considering our 14h photoperiod, our plnts received KJ m -2 d -1 of UV-A while only 0.55 KJ m -2 d -1 of UV-B, which is 0.76% of the totl UV irrdince. Therefore, we ssume tht ny chnges observed in plnts nd insects under the UVA+ tretment were predominntly elicited by UV-A. To our knowledge, this is the first study tht hs looked t supplementl UV-A effects on plnt-insect interctions in the glsshouse environment, s opposed to previous reserch minly focused on UV-B impcts (Hunt nd McNeil, 1999; Kitts et l., 2006; Kuhlmnn nd Müller, 2009, 2010; Pul et l., 2011). For both plnts species studied, the supplementl UV-A tretment ppered to lter the size nd morphology over the entire crop cycle. Although plnts hd similr numbers of leves, pepper internodes were significntly shorter, similrly s previously reported in other plnt species (Kuhlmnn nd Müller, 2010; Comont et l., 2012). For eggplnts, plnt height ppered shortened but there were no significnt effects on height or lef re. This contrsts with previous work focussing on enhnced UV-B impcts on reduced lef re (Kitts et l. 2006). In the current study, chlorophyll nd crotenoid contents were lowered in eggplnt with UV-A tretment t both hrvest dtes nd under whitefly infesttion, s found on buckwhet or quino with supplementl UV-B (Gberšcik et l., 2002; González et l., 2009). A reduction in chlorophyll hs been proposed s n indictor of UV sensitivity (Smith et l., 2000). The relevnce of components of lef chemistry ws mesured in order to try to interpret the insect responses observed. Phenolic ptterns in peppers chnged in response to UV-A nd under herbivory. No secondry metbolite differences were observed during the erlier hrvest t 53 dys prior to insect introduction but were pprent t 68 dys. As expected, 5- O-cffeoylquinic cid nd flvonoid contents were significntly induced with enhnced UV- A (Gberšcik et l., 2002, Izguirre et l., 2007; Mhdvin et l., 2008; Kulhmnn nd Müller, 2009, 2009b, 2010). In the bsence of phids t 68 dys, evidence showed how plnts grown t ner zero UV-A but lter moved to UV-A regime (tretment UVA-/UVA+) hd higher level of lef secondry metbolites, which even exceeded the levels found in UV- A treted plnts over the entire crop cycle (UVA+/UVA+). This rediness of peppers to induce sunscreen compounds might be correlted with UV tolernce (Middleton nd Termur, 1993; Hrborne nd Willims, 2000). Menwhile, the flvonoid contents of plnts grown with supplemented UV-A but subsequently moved to ner zero UVA- declined rpidly to levels comprble to the control tretment UVA-/UVA- fter stress recovery. Hence the 16

18 effect of UV-A ws not cumultive over time (cf. Comont et l., 2012). Besides UV-shielding metbolites, elevted contents of phenolics hve been proposed s ntifeednts or digestibility reducers (Bllré et l., 1996; Pul nd Gwynn-Jones, 2003). Flvonoid levels re thought to be n importnt fctor in herbivore nutrition nd they my be prtilly induced by the sme signling pthwy s UV protection, in which the jsmonic cid plys key role (Mckerness, 2000; Strtmnn, 2003; Demukr et l., 2010; Mewis et l., 2012). Pepper phenolics were ffected by phid feeding s seen previously in tobcco (Izguirre et l., 2007). Whether the flvonoids detected cted lso s defense ginst M. persice needs further investigtion but results suggest phid dmge influencing their ccumultion compred to uninfested peppers. Indeed one of the flvonoids present in our smples, luteolin-7-o-(2-piosyl)glucoside, hs been previously proposed s deterrent compound ginst the lefminer fly species Liriomyz trifolii Burgess (Dipter: Agromyzide) in sweet pepper leves (Kshiwgi et l., 2005). Phenolics found in eggplnts were minly hydroxycinnmic cids, with 5-trnscffeoylquiniccid s the mjor compound (Stommel et l., 2003). As opposed to peppers, no significnt increses in secondry metbolites were observed with UV-A or whitefly infesttion in eggplnts. However, induction of severl flvonoids hs been stted to protect tissues from UV dmge in this species (Toguri et l., 1993). Pst reserch hs shown tht eggplnts lredy hve high constitutive defences. Exposure to high UV-B irrdinces did not influence phenolic ccumultion, lef re nd Chl /Chl b rtio (Smith et l., 2000; González et l., 2009). These results ltogether my indicte high tolernce to UV irrdince in this species possibly relted to its ncestrl origin from tropicl regions. Totl non-structurl crbohydrtes were lowest in uninfested peppers grown under UV-A during the complete durtion of the experiment (68 dys) compred to ll other tretments. Comont et l. (2012) lso reported reductions in sucrose, glucose nd fructose contents on Arbidopsis thlin L. following UV-B tretment lthough contrsting results hve been obtined on mize leves (Brsig nd Mlz, 2000). However when insects were introduced, sucrose content ws significntly higher in tretments where M. persice ws grown under UV-A. This might gree with previous reserch done under UV-B stress where higher soluble sugr content, minly sucrose, ws observed under ddition of UV-B (González et l., 2009). Crbohydrte ccumultion my hve ffected phid fitness becuse sucrose is strong feeding stimulnt nd the mjor component of the phloem sp of plnts (Mittler et l., 1970; Srivstv nd Auclir, 1971). Indeed when UV-A ws withdrwn, dults produced less progeny with lower growth rtes. By contrst, eggplnt soluble sugrs were unffected by UV-A nd totl levels were similr t every hrvest time nd under whitefly herbivory, displying nother relible indictor to UV tolernce (González et l., 2009). Amino cids re the mjor nitrogen source for phids. In our work, we observed significntly higher free mino cids in pepper leves exposed to UV-A rdition, suggesting tht such plnts could be preferred by insects. Amino cids re n essentil dietry component for M. persice growth (Ddd nd Krieger, 1968) tht hs minly nutritive role in phid feeding (Srivstv nd Auclir, 1975; Weibull, 1987). Nitrogen content is thought to ct s feeding stimulnt for insects (Schoonhoven et l., 2006), being higher when high rdition intensities 17

19 re present in the environment (Roberts nd Pul, 2006). It is likely tht phloem qulity under supplemented UV-A conditions hd richer composition tht my hve triggered positive plnt-medited effect on M. persice development nd fecundity. Moreover, free mino cids levels were unsurprisingly lower under herbivore ttck due to phid feeding. It should be emphsized tht here we focussed on the chemicl composition of entire pepper leves nd this my not necessry reflect tht in the phloem sp (Kehr, 2006). Further studies should be conducted to find out if the observed chnges in lef chemistry due to supplementl UV-A rdition re reflective of the chemicl chnges in the phloem sp, extrcted by stylectomy (Kennedy nd Mittler, 1953) or vi lef incisions (Milburn, 1970). There were no differences ccording to UV-A in protein nd free mino cid content in eggplnts. Very little is known bout the impct of UV rdition on the composition of free mino cids in phloem sp, but the sme trend hs been observed in other species of the fmily Brssiccee such s broccoli, where uthors reported similr contents except for incresed proline under low UV-B compred to high levels of UV-B (Kulhmnn nd Müller, 2009, 2010). The ddition of UV-A to the environment hd complex effects on phids. Minly, n indirect plnt-medited impct on M. persice effective fecundity ws observed. The effective fecundity mesured ws higher in erly UV-A tretment scenrios compred to the ner zero UV-A tretment (UVA-/UVA-). This ltter tretment lso resulted in lowered intrinsic rte of nturl increse nd men reltive growth rte when compred to the scenrio where plnts hd only been exposed to UV-A during erly growth (UVA+/UVA-). This my indicte tht ltertions in tissue chemistry occurred prior to phid infesttion nd contributed to its performnce. The reduction in the popultion growth without UV-A exposure is in greement with findings previously reported for severl phid species (Antignus et l., 1996; Chyzik et l., 2003; Díz et l., 2006; Kuhlmnn nd Müller, 2009; Pul et l., 2011; Legrre et l., 2012). The pre-reproductive period from birth to dult stge ws similr for ll tretments. In contrst, results provided evidence tht supplementl UV-A exposure hd n impct on the fitness of whiteflies, this contrsted with phids. The pre-reproductive period ws significntly incresed by two dys with supplementl UV-A during insect growth on plnts regrdless of the rdition regime before insect introduction (tretments UVA+/UVA+ nd UVA-/UVA+). Exposure of whiteflies to UV-A on plnts rised t ner zero UV-A (UVA- /UVA+) significntly lowered the number of eggs compred to ner zero UV-A for the entire crop cycle (UVA-/UVA-). There ws no sttisticlly significnt difference in the number of eggs between tretments UVA-/UVA- nd UVA+/UVA-, which supports the hypothesis tht this effect ws not medited by host cues s it did not depend on the UV-A regime the plnts hd been grown under before whitefly infesttion. This resulted in significntly lower fertility in the tretments where UV-A ws supplemented during insect growth (Tble 2). When whiteflies were subjected to supplementl UV-A tretments, eggplnts received rdition t the sme time lthough the chemicl compounds involved in whitefly nutrition tht we nlysed (free mino cids nd sugrs) were unffected by supplementl UV-A. UV- A rdition inside the clip-cges where insects were monitored ws 0.00 W m -2 in the 18

20 tretment UVA- vs W m -2 in the tretment UVA+, difference tht my not be sufficient to conclude tht UV-A hd direct impct on whitefly performnce. However, the floor of the cges ws luminium nd reflected prt of the UV rdition into the clip-cges in the supplementl UV-A tretment. Rdition trnsmitted through the leves could rech the ventrl prt of the whitefly nymphs nd the rdition reflected by the floor reching the bxil side of the leves could irrdite the dorsum of whiteflies (Tble 1). While results indicte possible negtive effect of UV-A which cnnot be explined by chnges in plnt chemicls mesured, we cnnot dismiss the possibility of n effect triggered by spects of host plnt chemistry tht were not mesured. Further work to isolte direct from plntmedited effects of UV-A rdition on whitefly performnce should be conducted in the future by irrdition of insects under free-plnt environment. The effect of UV on the life processes of whiteflies hs been little studied. Trditionlly reserch hs focused on flight behvior in host choice ssys, with more whiteflies being trpped under environments with UV rdition (Antignus et l., 1996; Cost nd Robb, 1999; Kuhlmnn nd Müller, 2009), but to the best of knowledge, for the first time its performnce hs been tested under different UV-A regimes. In pst studies, it is likely tht whiteflies were driven by the rdition spectrum rther thn by the plnt chemistry s they tested orienttion nd lighting (Kuhlmnn nd Müller, 2009b), wheres in our work insects were cged nd forced to feed on ech plnt. Whiteflies showed n explicit tendency to grow slower under the UV-A source fter insect infesttion. This might be explined by the mechnism by which UV rdition triggers migrtory behviour (Mound, 1962; Coombe, 1982). However, the bsence of UV might hve extended the mting period so whiteflies fed nd lid eggs over greter period t ner zero UV-A rdition. Alloction of UV-A-shielding compounds responsible for physicochemicl defense involved some constrins on peppers, s plnt growth decresed under high UV-A conditions. The UV-induced phenolic pttern in pepper contrsted with lck of chnges observed in eggplnts. In ddition, this ltter species lso showed other chrcteristics present in plnts tolernt to high UV irrdinces, such s no chnges in lef re nd content of soluble crbohydrtes irrespective of UV-A exposure. We hypothesise tht these findings might be relted to high tolernce to UV-A. UV-A rdition ltered the chemicl composition of pepper plnts, with consequences to pest fitness. It is cler tht UV-A enriched pepper nutritionl qulity for phids. In contrst for whiteflies, there ws direct negtive effect of UV-A rther thn vi tissue qulity. As whole, results reported in the two complexes suggest tht UV-medited chnges re highly dependent on the plnt nd insect studied. Nevertheless, we believe tht UV-bsorbing nets might be useful tool ginst phids without detrimentl effects on crops. Further knowledge is needed to unrvel the complete role of UV-A rdition in plnt-insect interctions, nd to elucidte whether these responses present interctions with effects occurring s consequence of other frctions of the solr spectrum. Acknowledgements 19

21 The uthors cknowledge the support by funds from the Spnish Ministry of Science nd Technology (Reserch grnts AGL C02-01, BES nd EEBB-I ) nd COST-Action FA0906 Short Term Scientific Missions Progrmme. 20

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28 Fecundity (no. nymphs or eggs femle - 1 ) UVA+/UVA+ b UVA- /UVA- UVA+/UVA- b UVA- /UVA+ b c bc M. persice B. tbci c