Previous - Next
Yellow
mottle
Line
pattern
Fleck
Ajinashika
disease
Grapevine
stunt
Roditis
leaf discoloration
G.P. Martelli
CAUSAL AGENTS
Rugose wood is now considered to be a virus disease although its causal agent(s) has not yet been identified. The closterovirus GVA was originally isolated in Italy from a vine with a pitted trunk (Conti et al., 1980). Later, inconsistent association of several serologically unrelated closteroviruses with wood pitting symptoms was reported from different countries. A tendentially more consistent association seems to exist between rugose wood sensu lato and GVA (Rosciglione and Gugerli, 1986; Zimmermann, 1990). However, some of these viruses, including GVA, are the same as those found in vines with leafroll disease. Thus, the assumption that the rugose wood complex is induced by one or more viruses is still largely based on its graft transmissibility and in part on its vector transmissibility. It should be noted, however, that a long closterovirus serologically differing from all those previously reported has recently been found in the original Californian source of corky bark (Namba et al., 1991). Moreover, a short closterovirus (particles approximately 800 nm long) named grapevine virus B (GVB) was isolated by mechanical inoculation from corky bark-affected vines in Europe and North America ( Boscia et al., 1992). These recent findings strongly support the likelihood of a closterovirus aetiology for some of the components of the rugose wood complex.
GEOGRAPHICAL DISTRIBUTION
Rugose wood is widely distributed in most viticultural areas of the world.
ALTERNATE HOSTS
No host is known besides Vitis species.
FIELD SYMPTOMS
As defined in this handbook, rugose wood is a complex disease characterized by modifications of the woody cylinder. As specified below, four possibly different disorders can be recognized by indexing: rupestris stem pitting; corky bark; Kober stem grooving; and LN 33 stem grooving. Individual diseases cannot readily be distinguished in the field because of the absence of differential specific symptoms. In general, however? affected vines may be dwarfed and less vigorous than normal and may have delayed bud opening in spring. Some vines decline and die within a few years after planting. Grafted vines often show swelling above the bud union and a marked difference between the diameters of scion and rootstock (Figure 65). With certain cultivars, the bark of the scion above the graft union is exceedingly thick and corky and has a spongy texture and a rough appearance (Figure 66). The woody cylinder is typically marked by pits and/or grooves (Figure 67), which correspond to peg- and ridge-like protrusions on the cambial face of the bark (Figure 68). These alterations may occur on the scion (Figure 69), rootstock (Figure 70) or both (Figure 71), according to the cultivar/stock combination and possibly individual susceptibility. In most cases no specific symptoms are seen on the foliage, but bunches may be smaller and fewer than normal. Certain cultivars show foliage alterations similar to those induced by leafroll, i.e. rolling, yellowing or reddening of the leaf blades. These symptoms, when they occur, are more severe than those induced by ordinary forms of leafroll.
The ridges of the cortex consist of hypertrophied rays extending from the bark into the functional xylem. Xylem strands are arranged irregularly, often being split into two or three smaller ones that run in diverging directions, thus conferring a fimbriate appearance to the woody cylinder. Parenchymatosis occurs in both xylem and Phloem. These anatomical abnormalities originate from the altered behaviour of the vascular cambium.
NATURAL SPREAD
There is little doubt that rugose wood spreads primarily through infected propagative material. No field spread has been observed in Europe. However, there is evidence that in Mexico and Israel corky bark spreads in vineyards (Figure 72). The pseudococcid mealybug Planococcus ficus was reported to transmit corky bark experimentally from naturally diseased sources to the indicator LN 33 (Tanne, Ben Dov and Raccah, 1989).
DETECTION
Most rootstock/scion combinations express xylem symptoms in the field. To see the symptoms the bark must be removed; therefore, the best time for observation is during active vegetation (May to August in the Mediterranean area). The graft union is the first place to look for wood alterations. Sometimes the presence of pitting is obvious on the outer surface of the hark ( Figure 73). If not. two parallel cuts 1 to 2 cm apart, and a third cut across the first two, are made with a budding knife, and a strip of cortex is lifted to uncover the xylem (Figure 74). If no pits are seen, since their distribution may be irregular, new windows can be opened in the bark at different heights and locations above and below the graft union and around the whole circumference of the trunk. Infected vines may show no symptoms. In this case, field detection is not possible and diagnosis must rely on graft transmission tests.
IDENTIFICATION
Indexing by graft transmission
Rugose wood is transmitted by grafting, although sometimes without symptoms. Determination of the diseases forming the complex can be done using three differential indicators, i.e. Vitis rupestris, LN 33 and Kober 5BB.
Rupestris stem pitting. In V. rupestris this disease induces a distinctive basipetal pitting limited to a strip extending downward from the point of inoculation (Figure 75). LN 33 and Kober 5BB remain symptomless. Because of the peculiar localization of symptoms in V. rupestris, chipbud grafting is recommended when indexing for rupestris stem pitting. In this case, the symptoms develop below the graft union toward the roots. Responses obtained by top grafting (Figure 76) are more difficult to detect. Wood symptoms appear two to three years after grafting.
Corky bark. This disease elicits grooving and pitting in all parts of the stem of V rupestris and LN 33, but not in Kober 5BB. Furthermore, it induces proliferation of secondary phloem tissues of LN 33, giving rise to highly typical internodal swellings with a cracked surface (Figure 77). infected LN 33 indicators are severely stunted and show early rolling and reddening of the leaves (Figure 78). Sometimes irregular yellow spots appear on the leaves of the spring flush (Figure 79). The canes ripen irregularly or not at all (Figure 80), and the vines may die within a year. Wood and cane symptoms may develop a few months after grafting, but usually they are fully expressed within two years. In greengrafted LN 33 indicators, symptoms on the canes may appear 20 to 40 days after inoculation.
Kober stem grooving. This disease induces a marked grooving on the stem of Kober 5BB (Figure 81) but no symptoms in V. rupestris and LN 33.
LN 33 stem grooving. Grooves of various lengths develop on the stem of LN 33 (Figure 82), much the same as with corky bark, but these are not accompanied by phloem proliferation leading to internodal swellings or by foliar discolorations. Vitis rupestris and Kober 5BB are symptomless.
Micropurification
Closteroviruses associated with rugose wood can be recovered by micropurification procedures as outlined in Part III. Petioles and main veins of old symptomatic leaves are good sources of virus, together with bark from dormant or green cuttings.
Serology
ELISA and ISEM can be applied using the procedure outlined for leafroll disease.
Polyacrylamide gel electrophoresis (PAGE)
Application of PAGE to RNA extracts from in vitro shoot-tip cultures of vines affected by rupestris stem pitting has led to the fairly consistent recovery of a small dsRNA (Monette, James and Godkin, 1989; Azzam, Gonsalves and Golino, l 991). The diagnostic value of these RNAs, however, requires further evaluation.
SANITATION
Visual sanitary selection carried out in established and aged (eight to ten year old) vineyards to a great extent helps eliminate rugose wood from selected clones. However, because of symptomless field infections, vines free of the complex are best obtained by heat treatment (more than 150 days at 38°C) and removal of shoot tips to be rooted or cultured in vitro.
REFERENCES
Azzam, O.I., Gonsalves, D. & Golino, D. 1991. Detection of dsRNA in grapevines showing symptoms of rupestris stem pitting disease and the variability encountered. Plant Dis., 75: 690694.
Beukman, E.F. & Goheen, A.C. 1966. Corky bark, a tumor-inducing virus of grapevines. Proc. Int. Conf. Virus Vectors Perennial Hosts and Vitis, 1965, p. 164-166. Div. Agric. Sci., Univ. Calif., Davis.
Boscia, D., Savino, V., Minafra, A., Namba, S., Elicio, V., Castellano, M.A., Gonsalves, D. & Martelli, G.P. 1992. Properties of a filamentous virus isolated from grapevines affected by corky bark. Arch. Virol., (in press).
Conti, M., Milne, R.G., Luisoni, E. & Boccardo, G. 1980. A closterovirus from a stem pitting diseased grapevine. Phytopathology, 70: 394399.
Goheen, A.C. 1988. Rupestris stem pitting. In R.G. Pearson and A.C. Goheen, eds. Compendium of grape diseases, p. 53. St Paul, MN, USA, Am. Phytopathol. Soc.
Graniti, A. & Martelli, G.P. 1966. Further observations on "legno riccio" (rugose wood), a graft transmissible stem pitting of grapevine. Proc. Int. Conf: Virus Vector Perennial Hosts and Vitis, 1965, p. 168-179. Div. Agric. Sci., Univ. Calif., Davis;.
Monette, P.L., James, D. & Godkin, S.E. 1989. Double stranded RNA from rupestris stem pittingaffected grapevines. Vitis, 28: 137- 144.
Namba, S., Boscia, D., Azzam, O., Maixner, M., Hu, J.S., Golino, D. & Gonsalves, D. 1991. Purification and properties of closterovirus-like particles associated with grapevine corky bark disease. Phytopathology, Xl: 964-970.
Rosciglione, B. & Gugerli, P. 1986. Maladies de l'enroulement et du bois strié de la vigne: analyse microscopique et sérologique. Rev. Suisse Vitic. Arboric. Hortic., 18: 207-211.
Savino, V., Boscia, D. & Martelli, G.P. 1989. Rugose wood complex of grapevine: can grafting to Vitis indicators discriminate between diseases? Proc. 9th Meet. ICVG, Kiryat Anavim, Israel, 1987, p. 91 94.
Tanne, E., Ben Dov, Y. & Raccah, B. 1989. Transmission of corky bark disease by the mealybug Planococcus ficus. Phytoparasitica, 17:55.
Zimmermann, D. 1990. La maladie de l'enroulement de la vigne: caractérisation de quatre particules virales de type closterovirus à l'aide d 'anticorps monoclonaux et polyclonaux. Ph.D. thesis. Univ. Louis Pastcur, Strasbourg. 256 pp.
Summary: rugose wood complex detection
GRAFT TRANSMISSION
Indicators
V. rupestris St George: rupestris stem pitting
LN 33: Corky bark
Kober 5BB: Kober stem grooving
LN 33: LN 33 stem grooving
No. plants/test
3-5 rooted cuttings
Inoculum
Wood chips or single buds (recommended for Rupestris stem
pitting), bud sticks
Temperature
22°C (green grafting)
Symptoms
Basipetal pitting below grafted bud (stem pitting);
internodal swellings and stem grooving in LN 33 (corky bark);
stem grooving in Kober 55B only (Kober stem grooving); stem
grooving in LN 33 only (LN 33 stem grooving)
OTHER TESTS
Serology (ELISA, ISEM) for the closterovirus associated with
corky bark and GVA
Electrophoresis (PAGE) for dsRNA pattern
Molecular hybridization (OVA, GVB)
FIGURE 66 Corky appearance of the bark above the graft union in a vine affected by rugose wood
FIGURE 69 Symptoms of rugose wood showing only on the scion of a diseased vine
FIGURE 70 Symptoms of rugose wood showing only on the rootstock of a diseased vine
FIGURE 71 Symptoms of rugose wood showing on both scion and rootstock of a diseased vine
FIGURE 73 Grooves can sometimes be seen on the outer surface of the cortex after removal of the bark
FIGURE 77 Typical internodal swelling and cracking induced by corky bark in LN 33
FIGURE 78 Stunting and leaf reddening of an LN 33 indicator affected by a severe form of corky bark
G.P. Martelli and J. Lehoczky
CAUSAL AGENT
The causal agent of yellow mottle is alfalfa mosaic virus (AMV), a mechanically transmissible virus with polymorphic particles (from quasi-isometric to bacilliform) measuring 28 to 58 x 18 nm and a tripartite genome.
GEOGRAPHICAL DISTRIBUTION
Yellow mottle has been reported only from central and eastern Europe (Germany, Switzerland, Czechoslovakia, Hungary and Bulgaria).
ALTERNATE HOSTS
AMV is a polyphagous virus infecting a great number of plant species in nature and artificially (Hull, 1969). The inoculum is widespread in temperate climates.
FIELD SYMPTOMS
Various patterns of yellow discolorations of the foliage characterize the disease. The spring growth shows in differing amounts yellowing of the leaf blades that does not extend to the veins, which remain green (Figure 83). Warm springs favour the development of symptoms. Faint yellow speckling, rings and lines (Figure 84) are typical summer responses of infected vines. Plant vigour and yield do not seem appreciably affected.
NATURAL SPREAD
AMV is transmitted in a non-persistent manner by aphids, which readily pass it from host to host. Although it is likely that grapevine infections originate from occasional inoculations by viruliferous aphids, there is no experimental evidence of this. The virus persists in propagative material and is perpetuated through it.
DETECTION
Field symptoms disclose the presence of diseased vines, especially in spring when symptom expression is at its peak.
IDENTIFICATION
Identification based on symptomatology is not possible because the symptons so closely resemble diseases induced by other viruses. It must be carried out with biological and laboratory procedures.
Indexing by graft transmission
AMV is readily transmitted by any of the graft inoculation procedures described in Part II. Chipbudding gives satisfactory results with several indicators: Vitis rupestris, Pinot noir, Siegfriedrebe, Mission, Chardonnay and Veltliner rouge précoce. The last two cultivars, because of their strong and consistent responses a few weeks after inoculation, are recommended as especially suitable indicators (Beczner and Lehoczky, 1981). The symptoms are much the same as those shown by naturally infected vines (Figure 85).
Transmission to herbaceous hosts
AMV is readily transmitted by inoculation of sap to an extremely wide range of herbaceous hosts.
Leaf tissues ground in 0.07 M phosphate buffer. pH 7.2, containing 3 percent polyethylene glycol 6 000 (PEG), or in 2.5 percent aqueous nicotine are an excellent source of inoculum.
Diagnostic hosts are many:
Serology
Immunodiffusion tests are easily performed with extracts from AMV-infected herbaceous hosts. ELISA was successfully used for the detection of AMV in naturally infected field-grown cv. Chardonnay vines in Hungary.
SANITATION
No information is available.
REFERENCES
Beczner, L. & Lehoczky, J. 1981. Grapevine disease in Hungary caused by alfalfa mosaic virus. Acta Phytopathol. Acad. Sci. Hung., 16: 119-128.
Bercks, R., Lesemann, D. & Querfurth, G. 1973. Über der Nachweis des alfalfa mosaic virus in einer Weinrebe. Phytopathol Z., 76: 166-171.
Hull, R. 1969. Alfalfa mosaic virus. Adv. Virus Res., 15: 365-433.
Summary: yellow mottle detection
GRAFT TRANSMISSION
Indicators
Vitis vinifera cv. Chardonnay and Veltliner rouge
précoce
No. plants/test
3-5 rooted cuttings
Inoculum
Wood chips, single buds, bud sticks
Temperature
Fieid conditions
Symptoms
Yellow spots, rings and fines from 3-4 months after
inoculation onward
TRANSMISSION TO HERBACEOUS HOSTS
Diagnostic hosts
Phaseolus vulgaris, Ocimum basilicum
Inoculum
Tissues from young symptomatic leaves
Extraction
Grind tissues in 0.07 M phosphate buffer, pH 7.2, containing
3 percent PEG or in 2.5 percent aqueous nicotine
Temperature
Below 25°C
Symptoms
In P. vulgaris, necrotic local lesions in 5-6 days and
systemic mottling in 10-12 days;
In O. basilicum, systemic yellow blotches in about 2 weeks
OTHER TESTS
Serology (ELISA)
FIGURE 83 Bright yellow mottling induced by AMV infections in spring
FIGURE 84 Yellow spots and line patterns in naturally infected cv. Chardonnay in summer
FIGURE 85 Yellow line pattern in graft-inoculated cv. Chardonnay indicator
FIGURE 86 Necrotic local lesions induced by AMV in P.vulgaris(Photo: B. Walker)
FIGURE 87 Systemic symptoms induced by AMV in C. quinoa (Photo: B. Waller)
FIGURE 88 Necrotic local lesions induced by AMV in Vigna unguiculata Photo: B. Walter)
G.P. Martelli and J. Lehoczky
CAUSAL AGENT
Line pattern is caused by grapevine line pattern virus (GLPV), a possible member of the ilarvirus group. GLPV has polymorphic particles (quasispherical to bacilliform) 24 to over 100 nm in length and a multipartite genome.
GEOGRAPHICAL DISTRIBUTION
The disease has been reported only from Hungary, where it occurs in a few cultivars (Jubileum 75, Limberger and Oliver Irsai). Its incidence rarely exceeds 0.2 percent.
ALTERNATE HOSTS
No alternate host is known.
FIELD SYMPTOMS
Symptoms include bright yellow discolorations of the leaves forming marginal rings of variable size, scattered spots or blotches or maple-leaf line pattern (Figure 89). The line pattern is typically confined to the petiolar area or develops on the upper part of the leaf blade, roughly following its contour (Figure 90). The above symptoms are typical of the acute infection phase (shock symptoms). Chronically infected vines only show small yellow spots or flecking of the leaves (Figure 91), but vigour and yield are progressively reduced.
NATURAL SPREAD
No vector is known. The disease does not spread through the soil; it is perpetuated and transmitted through budwood and seeds (Lehoczky, Martelli and Lazar, 1992).
DETECTION
Field symptoms are fairly obvious in newly infected vines. Chronic symptoms are more difficult to detect and require careful observation of the leaves in summer.
IDENTIFICATION
Shock symptoms of line pattern resemble those of AMV-induced yellow mottle. Chronic symptoms resemble those elicited by any of the several chromogenic virus strains that infect grapevines. Thus proper identification relies on biological and laboratory tests.
Indexing by graft transmission
Line pattern is transmissible by grafting to a number of European grape cultivars. The field syndrome is reproducible by graft inoculation (chip-budding, cleft- or whip-grafting) to Jubileum 75, but symptoms are slow to appear.
Transmission to herbaceous hosts
GLPV is readily transmitted by inoculation of sap to a moderately wide range of herbaceous hosts. Leaf tissues ground in 0.07 M phosphate buffer, pH 7.2, containing 3 percent polyethylene glycol 6 000 (PEG) are a satisfactory source of inoculum.
Diagnostic hosts are:
Serology
Immunodiffusion tests are readily performed with extracts from GLPV-infected herbaceous hosts. ELISA and ISEM are likely to tee applicable for virus detection in field samples, but they have not yet been tested.
SANITATION
No information is available.
REFERENCES
Lehoczky, J., Boscia, D., Burgyan, J., Castellano, M.A., Beczner, L. & Farkas, G. 1990. Line pattern, a novel virus disease of the grapevine in Hungary. Proc. 9th Meet. ICVG, Kiryat Anavim, Israel, 1987, p. 23-30.
Lehoczky, J., Martelli, G.P. & Lazar, J. 1992. Seed transmission of grapevine line pattern virus. Phytopathol. Mediterr., 31 : 1 15-1 16.
Summary: line pattern detection
GRAFT TRANSMISSION
Indicator
Vitis vinifera cv. Jubileum 75
No. plants/test
3-5 rooted cuttings
Inoculum
Wood chips, single buds, bud sticks
Temperature
Field conditions
Symptoms
Yellow rings and line patterns in the second year after
grafting
TRANSMISSION TO HERBACEOUS HOSTS
Diagnostic hosts
Chenopodium amaranticolor, C. quinoa, Nicotiana glutinosa
Inoculum
Tissue from young symptomatic leaves
Extraction
Grind in 0.07 M phosphate buffer, pH 7.2, with 3 percent
PEG or in 2.5 percent aqueous nicotine
Temperature
Below 25°C
Symptoms
In Chenopodium species, chlorotic local lesions in about a
week, systemic mottle and apical necrosis in 10-12 days;
In N. glutinosa, chlorotic local lesions in 5-7 days, systemic
mottling and necrosis in 10-12 days
FIGURE 89 Distribution of line pattern symptoms in a newly infected shoot of cv. Jubileum 75
FIGURE 90 Yellow rings and lines typically associated with grapevine line pattern disease
FIGURE 91 Scattered minute yellow spots associated with chronic line pattern infection
FIGURE 92 Distortion, mosaic and apical necrosis induced by GLPV in C. quinoa
FIGURE 93 Chlorotic local lesions in a N. glutinosa leaf inoculated with GLPV
FIGURE 94Young chlorotic lesions induced by GLPV in G. globosa
G.P. Martelli
CAUSAL AGENT
The causal agent of fleck is grapevine fleck virus (GFkV), a phloem-limited, non-mechanically transmissible isometric virus containing a single molecule of ssRNA (Boscia et al., 1991).
GEOGRAPHICAL DISTRIBUTION
Fleck was first identified as a disease in its own right in California by Hewitt and co-workers ( 1972). It has been recorded from a great many countries and is now thought to have a worldwide distribution.
ALTERNATE HOSTS
No alternate host is known.
FIELD SYMPTOMS
Field symptoms are absent in all European scions and in most American rootstock species and hybrids, in which the disease is latent. Symptoms are clearly shown by naturally infected, self-indexing Vitis rupestris St George. These consist of clearing of the veins of third and fourth order producing localized translucent spots, which are best seen by holding the leaves against the light (Figure 95). Leaves with intense flecking are wrinkled and twisted and may curl upward. Severe strains also induce varying degrees of stunting.
NATURAL SPREAD
No vector is known. Seed transmission does not occur. Although the disease can experimentally be transmitted through dodder (Cuscura spp.), (Woodham and Krake, 1983), spread is primarily through infected propagating material.
DETECTION
Detection in the field is only possible in infected, symptomatic V. rupestris.
IDENTIFICATION
Indexing by graft transmission
Grafting to V. rupestris St George produces the symptoms described above. In the field or greenhouse, symptoms appear five to six weeks after inoculation. They appear earlier (four weeks) when the indicators are grown at 22°C under continuous illumination in a growth chamber (Mink and Parsons, 1977). Mild strains may induce positive reactions in the year after grafting. The symptoms tend to fade away in summer, so readings should be made within eight to ten weeks after inoculation. Identification of fleck symptoms may be difficult if indexed vines also carry grapevine fanleaf. In this case, early readings as soon as foliar flecks appear may be useful for distinguishing between the two diseases.
Serology
ELISA and ISEM can be used to detect the causal virus in roots, leaves and cortex (bark scraping) of infected vines, even when these do not show symptoms, as is the case with all V. vinifera cultivars.
SANITATION
Heat treatment 38°C for not less than 60 days, removal and rooting under mist of shoot tips 5 to 8 mm long eliminates the disease from about 90 percent of the explants. Complete elimination of the causal agent is achieved by culturing 1 mm long explants in vitro at 30°C with a 15 hour photoperiod (Barlass et al., 1982).
REFERENCES
Barlass, M., Skene, K.G.M., Woodham, R.C. & Krake, L.R. 1982. Regeneration of virus-free grapevines using in vitro apical culture. Ann. Appl. Biol., 102: 291-295.
Boscia, D., Martelli, G.P., Savino, V. & Castellano, M.A. 1991. Identification of the agent of grapevine fleck disease. Vitis, 30: 97105.
Hewitt, W.B., Goheen, A.C., Cory, L. & Luhn, C. 1972. Grapevine fleck disease, latent in many varieties, is transmitted by graft inoculation. Ann. Phytopathol., hors ser., p. 43-47.
Mink, G.l. & Parsons, J.L. 1977. Procedures for rapid detection of virus and virus-like diseases of grapevine. Plant Dis. Rep., 61: 567-571.
Woodham, R.C. & Krake, L.R. 1983. Investigations on transmission of grapevine leafroll, yellow speckle and fleck diseases by dodder. Phytopathol. Z. 106: 193- 198.
Summary: fleck detection
GRAFT TRANSMISSION
Indicator
Vitis rupestris St George
No. plants/test
3-5 rooted cuttings
Inoculum
Wood chips, single buds, bud sticks, shoot tips
Temperature
22°C (green grafting or growth chamber)
Symptoms
Clearing of the veinlets in 4-6 weeks according to growing
conditions
OTHER TESTS
Serology (ELISA, ISEM)
FIGURE 95 Clearing of the veinlets of V. rupestris typical of fleck disease
S. Namba and G.P. Martelli
CAUSAL AGENT
This disease was reported to be caused by the concurrent infection of leafroll and fleck (Terse, 1990). However, an isometric, phloem-limited, non-mechanically transmissible RNA virus about 25 nm in diameter, consistently found in affected vines, is now suspected as the causal agent. This virus differs and is serologically distinct from the agent of fleck (Namba et al., 1991).
GEOGRAPHICAL DISTRIBUTION
This disease has been reported only from Japan.
ALTERNATE HOSTS
No alternate hosts are known. The disease is apparently restricted to Vitis vinifera cv. Koshu.
FIELD SYMPTOMS
Infected vines do not show appreciable symptoms on the foliage or apparent reduction of vigour and yield (Figure 96). The berries, however, are pale-coloured (Figure 97) and have a low sugar content, which makes the crop unmarketable. This condition gives the name to the disease, which is Japanese for "unpalatable fruit with low sugar content". American rootstock hybrids are infected without showing symptoms.
NATURAL SPREAD
No vector is known. Spread is primarily through infected propagating material.
DETECTION
Pale colouring and low sugar content of the berries disclose the presence of diseased vines. Symptoms are best seen at harvesting time.
IDENTIFICATION
Indexing by graft transmission
The disease is readily transmitted by grafting to healthy cv. Koshu vines. The symptomatology is reproduced two to three years after grafting.
Serology
ELISA and ISEM can be used to detect the suspected causal virus in various organs of infected vines. Green shoots and matured fruit cores are the best antigen sources.
SANITATION
Prolonged heat treatment as used for leafroll and fleck eliminates the disease.
REFERENCES
Namba, S., Boscia, D., Yamashita, S., Tsuchizaki, T. & Gonsalves, D. 1991. Purification and properties of spherical virus particles associated with grapevine ajinashika disease. Plant Dis., 75: 1 249- 1 253.
Namba, S., Iwanami, T., Yamashita, S., Doi, Y. & Hatamoto, M. 1986. Three phloem-limited viruses of grapevine: direct fluorescence detection. Food Fert. Technol. Cent. Taiwan Tech. Bull., 92: 1-17.
Terai, Y. 1990. Ajinashika disease: a combined effect of grapevine leafroll and grapevine fleck viruses on sugar content in the Japanese grape cultivar Koshu. Proc. 10th Meet. ICVG, Volos, Greece, 1990, p. 6770.
Summary: ajinashika disease detection
GRAFT TRANSMISSION
Indicator
Vitis vinifera cv. Koshu
No. plants/test
3-5 rooted cuttings
Inoculum
Wood chips, single buds, bud sticks
Temperature
Field conditions
Symptoms
Same as in the field in 2-3 years
OTHER TESTS
Serology (ELISA, ISEM)
S. Namba and G.P. Martelli
CAUSAL AGENT
An isometric, phloem-limited, non-mechanically transmissible virus about 25 nm in diameter, consistently associated with diseased vines, is regarded as the possible agent. This virus is serologically unrelated to the putative agent of ajinashika disease (Namba et al., 1986).
GEOGRAPHICAL DISTRIBUTION
The disease has been reported only from Japan.
ALTERNATE HOSTS
None are known. The disease is apparently restricted to Vitis vinifera cv. Campbell Early.
FIELD SYMPTOMS
Spring vegetation is delayed, internodes are short and leaves are small and curled and sometimes have scorched margins (Figure 98). Inflorescences are undersized, fruit-setting is impaired and bunches are few and shelled. Severely infected vines may be unfruitful. Summer recovery occurs so that the newly produced vegetation is apparently normal. Symptom expression is stronger in young (one to four year old) vines.
NATURAL SPREAD
The disease is transmitted in nature by the grapevine leafhopper Arboridia apicalis (Figure 99). Spread also occurs through infected propagating material.
DETECTION
Affected vines are readily identified in the field, especially in spring when symptom expression is at its peak.
IDENTIFICATION
Indexing by graft transmissionThe disease is readily transmitted by grafting to cv. Campbell Early, in which the field syndrome is reproduced in about a year.Transmission by vectorsAdults and larvae of A. apicalis transmit the disease agent to cv. Campbell Early vines with acquisition and inoculation periods of five and seven days, respectively. Symptoms appear about a year after feeding of viruliferous insects.SerologyAn antiserum for ELISA testing is being developed.
SANITATION
The virus was eliminated from up to 40 percent of grapevine explants after treatment for five months at two temperature regimes (30°C for 10 hours and 40°C for 14 hours).
REFERENCE
Namba, S., Iwanami, T., Yamashita, S., Doi, Y. & Hatamoto, M. 1986. Three phloem-limited viruses of grapevine: direct fluorescence detection. Food Fert. Technol. Cent. Taiwan Tech. Bull., 92: 1-17.
Summary: grapevine stunt detection
GRAFT TRANSMISSION
Indicator
Vitis vinifera cv. Campbell EarlyNo. plants/test3-5
rooted cuttings
Inoculum
Wood chips, single buds, bud sticks
Temperature
Field conditions
Symptoms
Same as in the field in about a year
OTHER TESTS
Serology (ELISA is being developed)
FIGURE 98 Stunt symptoms in spring. Note poor growth and curling of the leaves
FIGURE 99 Adult of Arboridia apicalis, the leafhopper vector of grapevine stunt
l.Ch. Rumbos, A.D. Avgelis and G.P. Martelli
CAUSAL AGENT
Diseased vines are doubly infected by GFLV and carnation mottle carmovirus (CarMV) (Avgelis and Rumbos, 1990). CarMV is a virus with isometric particles about 30 nm in diameter and a monopartite RNA genome.
GEOGRAPHICAL DISTRIBUTION
The disease has been reported only from Greece.
ALTERNATE HOSTS
CarMV has a fairly narrow range of natural hosts, but experimentally it infects a wide spectrum of botanical species (Hollings and Stone, 1970).
FIELD SYMPTOMS
Field symptoms include yellowish and/or reddish discolorations of tissues along the veins, interveinal areas or variously extended sectors of the leaf blade, especially near the petiole (Figures 100 and 101). Leaves are deformed, usually in correspondence to discoloured sectors. Bunches are reduced in number and size and have a low sugar content. The symptoms appear in spring and persist through the vegetative season.
NATURAL SPREAD
No vector is known. Spread is through infected propagating material.
DETECTION
Diseased vines are readily identified in the field because of their yellow foliage.
IDENTIFICATION
Indexing by graft transmission
The disease is readily transmitted by grafting to Vitis vinifera cv. Mission. Symptoms appear within the first year after grafting and are similar to those observed in the field.Transmission to herbaceous hostsCarMV and GFLV are both mechanically transmissible to a fairly wide range of herbaceous hosts. Diagnostic hosts for the grapevine isolate of CarMV are:
Serology
ELISA can be used for GFLV detection in naturally infected vines and may also be applicable for the detection of CarMV.
SANITATION
No information is available.
REFERENCES
Avgelts, A.D. & Rumbas, l.Ch. 1990. Carnation mottle virus isolated from vines affected by Roditis leaf discoloration. Proc. 10th Meet. 1 CVG, Volos, Greece, 199O, p. 437-443.
Hollings, M. & Stone, O.W. 1970. Carnation mottle virus. Descriptions of Plant Viruses, No. 7. Kew, UK, Commonw. Mycol. Inst./Assoc. Appl. Biol.
Rumbas, l.Ch. & Avgelis, A.D. 1989. Roditis leaf discoloration. A new disease of grapevine: symptomatology and transmission to indicator plants. J. Phytopathol., 125: 274-278.
Summary: Roditis leaf discoloration detection
GRAFT TRANSMISSION
Indicator
Vitis vinifera cv. MissionNo. plants/test3-5 rooted
cuttings
Inoculum
Wood chips, single buds, bud sticks
Temperature
Field conditions
Symptoms
Same as in the field in about a year
TRANSMISSION TO HERBACEOUS HOSTS
Diagnostic hosts
Chenopodium quinoa, Gomphrena globosa
Inoculum
Tissue from young symptomatic leaves or root tips
Extraction
Grind in 2.5 percent aqueous nicotine
Temperature
Below 25°C
Symptoms
(CarMV)
In C. quinoa, chlorotic local lesions, systemic mottling;
In G. globosa, reddish local lesions, systemic mottling, leaf
deformation
OTHER TESTS
Serology (ELISA) for GFLV and possibly also for CarMV
