S. GUIDONI ~, F. MANNIN1.2, A. FERRANDINO 3, N. ARGAMANTE 4, and R. DI STEFANO ~

The Effect f Grapevine Leafrll and Rugse Wd Sanitatin n Agrnmic Perfrmance and Berry and Leaf Phenlic Cntent f a Nebbil Clne (Vitis vinifera L.) S. GUIDONI ~, F. MANNIN1.2, A. FERRANDINO 3, N. ARGAMANTE 4, and R. DI STEFANO ~ Phenlic cncentratins in leaves and berries cllected frm bth heat-treated and grapevine leafrll assciated virus type 3 (GLRaV-3) and grapevine virus A (GVA) infected vines f the Nebbil clne 415 were analyzed thrughut the grwing seasn. Anthcyanins, hydrxycinnamyltartaric acids, flavnls, and catechins were analyzed by HPLC and ttal anthcyanins by spectrphtmetry. The results shwed that virus eliminatin induced an earlier and higher accumulatin f anthcyanins in berries, while a higher quantity f flavanls was fund in leaf blades f infected plants whse phtsynthetic activity was previusly demnstrated t be reduced. Sanitatin als induced an increase f vine vegetative vigr and juice sluble slids whereas yield and acidity were nt affected. KEY WORDS: clne, virus, heat therapy, phenlic cmpsitin Grapevine leafrll (GLR) and rugse wd cmplex (cmprehensive f fur syndrmes: rupestris stem pitting, Kber stem grving, LN33 stem grving, and crky bark) are harmful and widespread viral diseases. They are cnsidered t be the cause f delayed fruit maturity and f ther detrimental effects (20). Grapevine leafrll is assciated with different clsterviruses transmitted by graft r by mealybugs (3). At present, tw f them are cnsidered the mst significant in grapevine: GLRaV-1 and GLRaV-3 (grapevine leafrll assciated virus type 1 and 3) (2). The grapevine virus A (GVA), ften fund in GLR and rugse wd cmplex infected vines, is a trichvirus assciated with the etilgy f Kber stem grving (4). Althugh ur knwledge f the virlgical agents f the diseases has advanced, we d nt have precise infrmatin n the effects exerted by these viruses, r their assciatins, n the agrnmical and enlgical perfrmance f vines. Delayed maturity, reduced vegetative grwth, and reduced berry pigmentatin in sme red-fruited cultivars are lng knwn GLR effects (8,9,10,19,21). The reductin in vigr, yield, nursery take, and smetimes, the death f vines is reprted in assciatin with rugse wd (7,17). Hwever, nly recently have these effects been specifically examined by studying the behavir f the same grape gentype (i.e., clne) with r withut the presence f the disease r, better still, f specific viruses by means f artificial sanitatin r inculatin. 1Research Scientist and 3,4Graduate Students, Universit& di Trin, Dipartiment Clture Arbree, Via Lenard da Vinci 44, 10095 Grugliasc (T), Italy; 2Research Scientist, Centr Miglirament Genetic e Bilgia Vite, CNR. Via Lenard da Vinci 44, 10095 Grugliasc (T), Italy; and ~Research Scientist, Istitut Sperimentale Enlgia MIRAAF, Via P. Micca 35, 14100 Asti, Italy. *Crrespnding authr: E-mail mannini@cvt.t.cnr.it; Fax: +39-11-670-8658. Cntributin n. 361 Centr Miglirament Genetic e Bilgia Vite, CNR. Aknwledgements. Authrs wish t thank Dr. R. Credi, Istitut di Patlgia Vegetale, Universit& di Blgna, Italy, fr perfrming heat-treatments and ELISA tests. Manuscript submitted fr publicatin 1 July 1996. Cpyright 1997 by the American Sciety fr Enlgy and Viticulture. All rights reserved. 438 In Australia, leafrll eliminatin induced greater yield and vegetative grwth n a Muscadelle clne (15). The inculatin f tw attenuated strains f GLR caused a decrease in vigr, yield and sluble slids in a clne f Cabernet franc (22) but had n effect n a clne f Sultana (23). In France, Walter and Martelli (20) fund a decrease in yield and sluble slids in GLR-inculated Pint nir and Chardnnay clnes in cmparisn with the riginal healthy nes, but nly an increase f yield in a clne f Savignin rs~ after GLR eliminatin by heat treatment. The GLR eliminatin by heat therapy in a French Gewfirztraminer clne still infected by rupestris stem pitting resulted in an increased yield, but als in the decrease f sluble slids in the juice (1). Recent studies in Italy indicated that the effects varied depending n the different GLRaV islates present in the vine. It was reprted that in the early stage f vineyard life the presence f GLRaV-1 did nt affect the grwth and yield f Dlcett clnes (12). GLRaV-1, GLRaV-3, and GVA tgether had n effect n the yield, but induced a reductin in vine vigr, sluble slids, and berry skin phenlic cntents in Nebbil clnes (11,13,14). Mdificatins in skin phenlic cntent, in particular, may have a great influence n the final quality f red, full-bdied wines such as thse made frm Nebbil grapes in Piedmnt (Nrthwest Italy). The purpse f this paper was t examine the mdificatins in quality and quantity in grapevine leaf and berry skin phenlic cmpsitin caused by GLRaVs and GVA and t lk fr pssible physilgical explanatins. Materials and Methds The experiment was carried ut in a vineyard established in Barbaresc (Nrthwest Italy) in 1988 with infected and heat-treated healthy prgeny (30 vines each treatment) f the Nebbil clne 415 grafted n certified Kber 5BB rtstck. The clne was heattreated in a thermtherapy chamber with artificial

LEAFROLL/RUGOSE WOOD COMPLEX m 439 lighting at abut 37 C fr 140 days fllwed by in vitr culturing f 0.5 cm terminal sht tip explants. Established daughter vines f riginal and heat-treated clnes were repeatedly tested by ELISA fr GFLV (grape fanleaf virus), GFkV (grape fleck virus), GVA, GLRaV-1 and GLRaV-3 using cmmercial cating and cnjugate antibdy preparatins (Sanfi Phyt-Diagnstics, Marnes-La-Cquette, France; Agritest, Valenzan, Italy). The riginal clne mther plant and its prgeny (MP) were infected by GLRaV-3 and GVA whereas in the heat-treated prgeny (HT) these viruses were absent. The vineyard was n a hillside and the vines were single cane pruned and vertical trained with a spacing f 3.00 0.80 m. The sil was lamy with a ph f 7.8. The main agrnmical parameters (yield, average cluster weight, and pruning weight), juice cmpsitin (sluble slids, titratable acidity, ph, tartaric and malic acids), and the berry skin phenlic cntents were evaluated ver a perid between 1992-1994. Tartaric and malic acids were measured by HPLC. The skin cntents were determined by spectrphtmetry n 300 randm berry samples (5). In 1994 the leaf phtsynthetic rate was measured by means f a ADC-LCA3 gas-analyzer equipped with a Parkinsn leaf chamber. The measurements were cnducted n basal leaves ppsite t the cluster and n the upper leaves sampled between the 10 th and the 14 th nde frm the sht base at fur different dates during the vegetative seasn (23 June, 14 July, 3 and 24 August). Each measurement f 10 leaves was repeated three times during the mrning. Evaluatins f phenlic cmpunds were carried ut in 1994 bth n leaves and berries accrding t Di Stefan and Maggirtt (6). Samples f five leaves were cllected weekly frm sht ndes ppsite t the cluster, frm 26 July until harvest (28 September). Petile and leaf veins were analyzed separately frm the blade. Samples f 10 berries (2 replicates) were cllected weekly frm 10 August until the skin f all berries became unifrmly clred. Berry samples were nt picked at randm but favred, whenever pssible, the tw mst intense levels f clr accrding t the fficial clr cde (18). Leaf and berry samples were treated as described (6). The extracts were analyzed fr anthcyanins, hydrxycinnamyltartaric acids, flavnls and catechins by HPLC and ttal anthcyanin index by spectrphtmetry (5). Single anthcyanin cncentratin was btained by multiplying the ttal anthcyanin index times single anthcyanin percentages determined by HPLC. Hwever, when the ttal anthcyanins were present in traces, nly the percentage f single anthcyanins was reprted. Results The agrnmical and chemical data gathered ver a fur-year perid (Table 1) shwed an increase in vegetative vigr induced by sanitatin. Yield was nt affected r was slightly in favr f MP vines. Virus eliminatin seemed t slightly elevate sluble slids, al- Table 1. Agrnmical and enlgical parameters f riginal GLRaV-3 and GVA infected (MP) and heat-treated (HT) vines f Nebbil clne 415 (average 1992-1994). Signif. Data M P HT f F1 Yield (kg/vine) 1.96 1.80 ns Pruning weight (g/vine) 904 1058 * Average cluster weight (g) 216 230 ns Sluble slids ( Brix) 20.6 21.1 ns Titratable acidity (g/l) 8.34 8.11 ns ph 3.06 3.06 ns Tartaric acid (g/l) 6.91 7.08 ns Malic acid (g/l) 3.55 3.30 ns Ttal flavnids as (+)-catechin (mg/kg f berries) 968 1270 * Ttal anthcyanins as malvidin 3-gl (mg/kg f berries) 660 769 * Veraisn 1994 (% at 19 August) 49 100 ** I ns = nt significant; * p < 0.05" ** p < 0.01. thugh the effect was nt statistically significant and was likely a result f a smewhat lwer yield, n effect was bserved n the acid cntent. Sanitatin, n the ther hand, psitively and significantly influenced the berry skin phenlic cmpunds; the amunt f ttal flavnids and anthcyanins was statistically higher in HT vines. Phtsynthetic measurements (Fig. 1) shwed a reductin in basal leaf phtsynthetic rate in the infected vines cmpared t the healthy nes, measurable at the time f fruit set, and again befre the appearance f leaf reddening and rlling, typical leafrll symptms. The efficiency f MP vine leaves decreased dramati- 17 ~11-15- 13- E 9-..,,,, E 7- m.. % _. I I I I 23 June 14July 3Aug 24 Aug fruit set Date Fig. 1. Net phtsynthesis trend in the upper (O) and the basal (V) leaves f virus-infected (MP... ) and heat-treated (HT--) vines f the Nebbil clne 415.

440 -- GUIDONI et al Table 2. Leaf blade phenlic cmpsitin (mg/100 blades). Numbers in the rectangle are expressed in % f ttal anthcyanins 1. Date a) mther plants 3 Aug 11.4 10 Aug tr. 17 Aug 17.0 24 Aug 20.0 31 Aug 40.8 6 Sept 66.0 13 Sept 20.0 22 Sept 65.2 28 Sept 42.0 b) heat treated plants 3 Aug tr 10 Aug tr 17 Aug tr 24 Aug tr 31 Aug tr 6 Sept tr 13 Sept 10.8 22 Sept 5.0 28 Sept 7.2 Tt. Dp Cy Pt Pn Mv acyl C y CT pot My Q Q C ant. 3-gl 3-gl 3-gl 3-gl 3-gl tt Pn c+tr c+tr 3-gl glu 3-gl 0.58 9.5 0.09 0.98 0.05 0.22 9.7 358 24 3.6 186 74 80 15.10 ~ 83.2 0.80 8.60 0.40 1.90 19.7 242 18 3.1 76 52 63 I 080,~0 003 0~ 00~ 0~ ~8 ~8 ~0 30 88 47 69 0~ ~7~ 008 ~0 004 03~ ~, ~0 ~ ~8 ~3~ ~3 ~8 0~7 ~ 0,6 ~6, 008 ~,,34,66 ~7 ~ ~3 33 68 ~06 ~3 0~0 396 0~3 6~0 ~37 ~60 ~8 30 ~7~ 6~ 8~ ~0 ~6~ 0~ ~80 008 06~ ~0 334 38 38,,3 67 ~0 0~ ~7 0~ 66~ 0~3 ~,~ 78 ~46 ~4,4 73 ~4 3~,~3 3~6 0~3 3~7 0,3 ~8 ~00,0~,0 ~0,3 ~ 3~ 0.0 88.9 0.0 11.1 0.0 2.5 66.3 2.8 8.3 2.3 2.5 47.2 1.8 28.7 4.8 1.9 75.5 3.1 4.4 4.4 1.8 75.5 2.8 9.9 2.0 1.5 75.3 2.9 10.4 1.6 0.08 8.64 0.20 1.32 0.08 0.05 4.20 0.10 0.44 0.04 0.04 5.40 0.40 0.74 0.00 0.0 8.0 17.8 8.0 15.0 1.6 10.7 17.2 7.9 9.5 8.3 7.2 0.52 6.5 0.19 9.5 0.65 7.3 73 18 40 41 48 54 33 34 21 264 12 1.5 64 27 15 9 322 18 3.4 191 41 15 17 56 28 O.4 8 6 7 3 229 14 2.7 57 42 17 12 236 14 2.8 91 52 15 8 285 22 3.3 107 55 30 24 136 8 1.6 73 31 11 10 160 12 1.3 44 26 15 13 114 6 1.1 36 18 10 6 l tr = traces; Tt.ant. = ttal anthcyanins; Dp = delphinidin; Cy = cyanidin; Pt = petunidin; Pn =penidin; Mv = malvidin; gl = 3-glucside; acyl = acylated frm f anthcyanins; My = myricetine; Q = quercetine; glu = glucurnide; CT = caffeyltartaric acid; pct = p-cumaryltartaric acid; C = (+)-catechin; E = (-)-epicatechin. cally ver the seasn alng with the appearance f symptms. On the ther hand, n differences were detected in the upper leaves until a few days befre veraisn, when a reddening and dwnward rlling f margins f the basal leaves in the infected plants were bvius. Leaf blade anthcyanins were mainly represented by cyanidin 3-glucside (an average f 80% f the ttal). Other cmpunds, including acylated frms, were slightly represented. The leaf blade anthcyanin cmpsitin in MP and HT vines did nt shw any qualitative differences, whereas quantitative differences were evident (Table 2). In infected vines, anthcyanin cntents were measurable at the beginning f August and Table 3. Berry phenlic cmpsitin (mg/100 berries). Tt. Df Cy Pt Pn Mv acil _C_y C_y CT pct My Q Q C E Date ant. 3-gl 3-gl 3-gl 3-gl 3-gl tt Pn Mv c+tr c+tr 3-gl glu 3-gl a) mther plants 10 Aug 2.8 0.1 0.6 0.1 1.2 0.4 0.3 0.5 1.5 2.2 4.0 0.2 1.6 2.1 1.3 1.0 17 Aug 8.2 0.4 2.1 0.4 3.6 1.1 0.7 0.6 2.0 2.1 3.5 0.2 1.3 1.6 1.2 1.2 17 Aug 27.2 1.1 5.7 1.2 11.8 4.3 2.9 0.5 1.3 2.1 3.8 0.2 1.3 2.1 1.7 1.2 24 Aug 21.2 0.7 2.9 0.9 9.7 4.3 2.6 0.3 0.7 2.1 3.6 0.2 1.2 1.6 1.5 1.0 31 Aug 63.2 3.8 9.7 3.4 27.4 13.2 5.8 0.4 0.7 2.7 4.0 0.4 1.3 2.9 1.7 1.3 6 Sept 68.9 4.7 11.8 3.4 28.9 13.1 6.9 0.4 0.9 2.0 4.0 0.7 2.5 9.2 1.4 1.4 b) heat treated plants 10 Aug 3.8 0.1 0.8 0.2 1.6 0.7 0.3 0.5 1.1 5.6 7.5 0.1 1.3 2.5 1.5 2.0 10 Aug 15.8 1.0 3.3 0.9 6.4 2.8 1.3 0.5 1.2 3.6 4.9 0.1 1.0 1.1 1.4 0.9 17 Aug 22.5 1.2 5.1 1.2 9.8 3.5 1.8 0.5 1.5 1.8 3.7 0.2 1.5 2.2 1.4 1.0 17 Aug 57.0 2.8 9.2 3.2 24.9 11.5 5.3 0.4 0.8 2.3 4.5 0.3 1.3 2.3 1.5 1.1 24 Aug 68.9 2.0 8.8 3.0 32.7 14.4 8.0 0.3 0.6 2.5 4.4 0.5 2.0 5.1 1.3 1.2 31 Aug 89.8 4.3 11.8 4.6 40.5 18.8 9.9 0.3 0.6 2.7 4.6 0.7 2.4 7.6 1.5 1.3 l tr = traces; Tt.ant. = ttal anthcyanins; Dp = delphinidin; Cy = cyanidin; Pt = petunidin; Pn =penidin; Mv = malvidin; gl = 3-glucside; acyl = acylated frm f anthcyanins; My = myricetine; Q = quercetine; glu = glucurnide; CT = caffeyltartaric acid; pct = p-cumaryltartaric acid; C = (+)-catechin; E = (-)-epicatechin.

LEAFROLL/RUGOSE WOOD COMPLEX- 441 their amunt reached a rather high level later in the seasn. In healthy vines, n anthcyanins were detectable in leaf blades until mid-september and als at harvest time their quantity was still very lw. The cyanidin 3-glucside/penidin 3-glucside rati was higher in MP vines. This difference culd be indicative f a faster transfrmatin f cyanidin 3-glucside int penidin 3-glucside by means f a methylating enzyme (-dihydrxyphenl O-methyltransferase) (16). Flavnls, hydrxycinnamyltartaric acids and catechins did nt vary between MP and HT vines frm a qualitative pint f view. Hwever their quantities, measured in the infected plants, were higher than thse measured in the HT vines. The higher cntents f (+)-catechin and (-)-epicatechin in infected vines might be a plant's reactin t a viral infectin. The amunt f ttal anthcyanins in leaf petiles and main veins was rather lw in bth MP and HT vines and n remarkable quantitative and qualitative differences were detected between them (data nt shwn). Accumulatin f berry skin anthcyanins depended n the virlgical status. Veraisn in HT prgeny was cmpleted ne week earlier (19 August) than in infected MP vines (26 August) (Table 1). Anthcyanin accumulatin in the skin went up cnstantly ver the ripening seasn and in the last reading their amunt was cnsiderably higher in HT vines than in infected plants (Table 3). Penidin 3-glucside dminated the ther anthcyanins, especially malvidin 3-glucside and cyanidin 3-glucside. The cyanidin 3-glucside/ malvidin 3-glucside rati, hwever, was variable ver the seasn. Until mid-august it was in favr f cyanidin 3-glucside in bth MP and HT plants, afterwards it turned t malvidin 3-glucside. The cyanidin/penidin 3-glucside rati als had a similar tendency, althugh penidin 3-glucside always remained higher. This might be a result f a higher activity f - dihydrxyphenl O-methyltransferase later in the seasn. The accumulatin f anthcyanins in the berry skin was faster in healthy vines. In the infected vines, the amunt f these cmpunds never reached the quantity registered in the healthy nes, despite the fact that the last berry sample was cllected frm infected vines ne week later than the last healthy ne. Anthcyanins in berry skins remained cnsistently higher in healthy vines because f a higher accumulatin f penidin, malvidin, and petunidin 3-glucsides, but nt f cyanidin and delfinidin 3-glucsides. Penidin, malvidin, and petunidin 3-glucsides prbably need the methylating enzyme fr synthesis. Enzyme activity mdificatin due t the presence f the virus might be a pssible explanatin fr these changes. In fact, n the last sampling date, nly delfinidin 3-glucside, (its synthesis des nt depend n the enzyme mentined abve), was still high in MP vines and shwing a regular increase. Malvidin 3-glucside and penidin 3-glucside accumulatin in MP vines seemed t have slwed cmpared t the HT vines. Fr all ther cmpunds, n imprtant differences were measured between the tw treatments. It shuld be nted that, as ppsed t the situatin in leaves, quercetin 3-glucside was the predminant flavnl and the p-cumaryltartaric acid the prevailing hydrxycinnamic acid. The berry skins f bth infected and healthy vines had lw levels f (+)-catechin and (-)- epicatechin. Discussin Eliminatin by heat treatment f GLRaV-3 and GVA frm the infected clne 415 f Nebbil cv. yielded healthy vine prgeny with a wider and greener canpy able t achieve better phtsynthetic activity than that f the infected mther plant. The verall result was early grape maturity in healthy vines. In additin t slightly higher sluble slid and lwer malic acid cntents in the juices, berry skin anthcyanins accumulated at a faster rate in healthy vines. This was already detectable at veraisn and cnfirmed by their higher amunt at harvest. Anthcyanin accumulatin in leaf blades shwed an ppsite trend; levels in healthy leaves were always lwer than in infected vines. Anthcyanin accumulatin in infected vine leaves was measurable early in the seasn and befre the appearance f GLR symptms. The anthcyanin accumulatin rate in leaves was ppsite t the leaf phtsynthetic trend; the higher and persevering phtsynthetic efficiency f HT leaves was related t a lwer and slwer anthcyanin accumulatin in healthy tissues and vice versa. In MP vines, the reductin in leaf phtsynthetic activity began early in the seasn and well befre the accumulatin f anthcyanins in the leaves and cnsequently the appearance f symptms. The lwer leaf efficiency, therefre, can nt simply be explained as a cnsequence f leaf reddening and rlling but it is attributable t a mre cmplex virus physilgical effect. The early and remarkable amunt f (+)-catechin and (-)-epicatechin fund in the leaves f MP, fr instance, might als indicate a rle f these cmpunds in the virus-vine relatinships. The differences in berry anthcyanin cntents between MP and HT vines were quantitative rather than qualitative and the differences may be a cnsequence f mdified enzyme activity related t anthcyanin bisynthesis in presence f these viruses. As in previus reprts (8,10,11,19) shwing the detrimental effects f GLR n berry clr, ur results cnfirmed the interference f the agents f GLR, i.e., the grapevine clsterviruses, in the metablism f phenls and particularly f anthcyanins in the vine. It is nt clear if the viruses slw dwn the mvement f anthcyanins frm leaves t berries, causing their accumulatin in fliar tissues, hence the symptms f leaf reddening and rlling, r if they interfere with the anthcyanin synthesis in the berry, mdifying the methylating enzyme activity. Althugh several technlgical factrs during vinificatin (such as skin maceratin and wd cntact) may mdify the phenlic cntributin t final wine

442 -- GUIDONI et al character, the higher cntents f anthcyanins and phenls in the berries f healthy vines shuld have a beneficial effects n the quality f red wines. Mre anthcyanins shuld enhance the clr f light-bdied reds increasing the vilet nuances, and a higher amunt f flavnids shuld imprve the structure f full-bdied red wines. The increase f vegetative vigr, frequently reprted with virus eliminatin (11,13,14,15,22), culd cause sme prblems in cl climate viticulture. Fr example, high vigr might result in a micrclimate inside the canpy favrable t Btrytis cinerea and/r a greater need fr cstly summer pruning. Nevertheless, the verall better vine perfrmances achieved by the eliminatin f severe GLR infectins, such as the nes present in the clne Nebbil 415, makes the use f sanitated vines which have had virus eliminated wrthwhile. Literature Cited 1. Balthazard, J. Valeur culturale du Gew0rztraminer clne n. 913 gu~ri du virus de I'enrulement par thermth~rapie. Prgres Agric. Vitic. 110:382-385 (1993). 2. Bscia, D., C. Greif, P. Gugerli, G. P. Martelli, B. Walter, and D. Gnsalves. Nmenclature f grapevine leafrll-assciated putative clsterviruses. Vitis 34(3):171-175 (1995). 3. Bvey, R., and G. P. Martelli. Directry f majr virus and virus-like diseases f grapevines. Prject PNUD-FAO. 111 pp. MFCIC-ICVG (Ed.) (1992). 4. Chevalier, S., C. Greif, J. M. Clauzel, B. Walter, and C. Fritsch. Use f an Immuncapture-Plymerase Chain Reactin Prcedure fr the Detectin f Grapevine Virus A in Kber Stem Grving-infected Grapevines. J. Phytpathl. 143:369-373 (1995). 5. Di Stefan, R., and M. C. Craver. Metdi per I studi dei plifenli dell'uva. Riv. Vitic. Enl. 2:34-75 (1991). 6. Di Stefan, R., and G. Maggirtt. Antciani, acidi idrssicinnamiltartarici e flavnli del frutt, delle fglie, dei raspi e dei tralci della vite. Riv. Vitic. Enl. 2:51-65 (1995). 7. Garau, R., M. Cugusi, M. Dre, and U. Prta. Investigatin n the yield f 'Mnica' and 'Italia' vines affected by legn ricci (stem pitting). Phytpath. Medit. 24:64-67 (1985). 8. Gheen, A.C. Grapevine leafrll. In: Virus diseases f small fruits and grapevines. Frazier, N.W. (Ed.). pp 209-219. Univ. f Califrnia, Div. f Agric. Sciences, Berkeley, Califrnia, USA (1970). 9. Kliewer, W. M., and L. A. Lider. Influence f leafrll virus n cmpsitin f Burger fruits. Am. J. Enl. Vitic. 27:118-124 (1976). 10. Krake, L. R. Characterizatin f grapevine leafrll disease by symptmatlgy. Australian and New Zealand Wine Industry Jurnal 8:40-44 (1993). 11. Mannini, F. Nuvi rientamenti nella selezine clnale e sanitaria. Vignevini 12:71-76 (1994). 12. Mannini, F., R. Credi, V. Gerbi, A. Lisa, J.L. Minati, and N. Argamante. Rul dell stat virlgic sul cmprtament in camp e sulle attitudini enlgiche di clni delle cultivar Ruch~ e Dlcett. Quad. Vitic. Enl. Univ. Trin 18:55-71 (1994). 13. Mannini, F., R. Credi, and N. Argamante. Changes in field perfrmance f clnes f the grapevine cv Nebbil after virus eliminatin by heat therapy. In: Prceeding f the 6 th Int. Symp. n Grape Breeding. OIV. (Ed.). pp 117-122. Yalta, Ukraine (1994). 14. Mannini, F., N. Argamante, and R. Credi. Imprvements in the quality f grapevine "Nebbil" clnes btained by sanitatin. Acta Hrtic. 427:319-324 (1996). 15. McCarthy, M. G., R. M. Cirami, and J. Van Velsen. Virus thermtherapy effects n the perfrmance f a Muscadelle selectin. Vitis 28:13-19 (1989). 16. Rgger, J. P., S. Cen, and B. Ragnnet. High perfrmance liquid chrmatgraphy survey n changes in pigment cntent in ripening grapes f Syrah. An apprach t anthcyanin metablism. Am. J. Enl. Vitic. 37:77-83 (1986). 17. Savin, V., D. Bscia, D. Musci, and G.P. Martelli. Effects f legn ricci (stem pitting) n 'Italia' vines grafted nt rtstcks f different rigin. Phytpathl. Medit. 24:68-72 (1985). 18. Seguy, E. XXX Cde Universel des Culeurs. Ed. Lechevalier, Paris (1936). 19. Uyemt, J. K., G. P. Martelli, R. C. Wdham, A. C. Gheen, and H. F. Dias. Grapevine (Vitis) virus and virus-like diseases. Set 1. In: Plant virus slide series. O. W. Barnett and S. A. Tlin (Eds.). Clemnsn Univ., Suth Carlina, USA. (1978). 20. Walter, B., and G. P. Martelli. Selectin clnale de la vigne: s~lectin sanitaire et s~lectin pmlgique. Influences des virses et quality, p 35. OIV, Paris (1996). 21. Wlpert, J. A., and E. P. Vilas. Effect f Mild Leafrll Disease n grwth, yield, and fruit maturity indices f Riesling and Zinfandel. Am.J.Enl.Vitic. 43:367-369 (1992). 22. Wdham, R. C., L. R. Krake, and K. M. Cellier. The effect f grapevine leafrll plus yellw speckle disease n annual grwth, yield and quality f grape frm Cabernet Franc under tw pruning systems. Vitis 22:324-330 (1983). 23. Wdham, R.C., R. W. Emmet, and G. C. Fletcher. Effects f thermtherapy and virus status n yield annual grwth and grape cmpsitin f Sultana. Vitis 23:268-273 (1984).