Brown Streaking Research Articles

Occurrence of Grapevine Declines and First Report of Black Dead Arm Associated with Botryosphaeria obtusa in Lebanon.

Grapevine, cultivated mostly in the Bekaa Plain, is one of the most important fruit crops in Lebanon. During July 2004, a survey was made in 11 vineyards of local table or wine grapes to evaluate the sanitary status of the grapevine industry as far as wood declines are concerned. The most common grapevine decline was esca. The two forms of the disease (mild and severe) were observed. The mild form was characterized by leaf symptoms consisting of interveinal necrotic spots with yellow or red chlorotic blotches on white and red cultivars. The severe form was characterized by dieback of one or more shoots, leaf drop, shrivelling, and drying of fruit clusters. In west Bekaa, on cv. Cabernet Sauvignon, some vines showed symptoms identical to those of Eutypa dieback such as stunted chlorotic shoots with small, distorted leaves; moreover, symptoms corresponding to black dead arm (BDA) such as wine red spots on the margins of leaves and dry spots were seen as reported earlier (1). Diseased vines of various cultivars were collected: 10 Cabernet Sauvignon (7 esca, 3 BDA, and 1 Eutypa dieback), 4 Beitamouni, 3 Carignan, 2 Teifihi, 1 Zeitouni, 1 Mourverdre, 1 Caladoc, and 1 Merlot. In wood, cross sections through the trunk were made that showed mainly central necrosis, white heart rot, brown red wood, and black spotting. Wedge-shaped lesions were the least common. Particularly for BDA, peeling off the bark revealed a brown streaking of the external wood. Isolations were made on malt agar (MA) with wood chips cut from the different necroses described above. Fungal identifications were based on morphological characteristics in comparison with French isolates after subculturing at 20 to 22°C: Fomitiporia sp. (F85-1), Phaeomoniella chlamydospora (F85-2), Eutypa lata (BX1-10, 8D, and 8F), and Botryosphaeria obtusa (F99-1). The fungus most frequently isolated from central necrosis with white heart rot was the basidiomycete Fomitiporia sp. (35% of vines). Cultures of Fomitiporia sp. on MA reached 4 to 5 cm in diameter after 2 weeks and were yellowish to brownish without conidia. P. chlamydospora (associated with esca, black goo, or Petri disease) was isolated from only 9% of vines investigated. Cultures of P. chlamydospora on MA were slow growing and reached 7 to 8 mm in diameter in the dark after 8 days. Colonies were white but became light green and later became dark green. Sporulation was abundant. E. lata (causing Eutypa dieback) was isolated from the vine of cv. Cabernet Sauvignon showing typical symptoms and from two vines showing symptoms of esca only. Two strains produced characteristic pycniospores, and all strains were identified using polymerase chain reaction (Primer Scar 10A-10B) (2). Among the saprophytic fungi isolated from the different kinds of necroses, either central, wedge-shaped, or under the bark, B. obtusa associated with BDA was found most commonly (65% of vines). Cultures of B. obtusa were gray brown with dense aerial mycelium. Pycnidia started to form after 4 to 5 days and conidia (20 to 26 × 9 to 16 μm) were dark brown when mature. These results are consistent with previous descriptions. To our knowledge, this is the first report of black dead arm in Lebanon.

First Report of Fusarium oxysporum f. sp. canariensis Causing Fusarium Wilt on Phoenix canariensis in Sardinia, Italy.

During the summer of 2004, severe symptoms of wilt were observed on 25-year-old plants of Canary Island Date Palm (Phoenix canariensis Hort. ex Chabaud) located at the seafront of Poetto Beach in the metropolitan area of Cagliari, southern Sardinia, Italy. Symptoms consisted of one-sided leaflet dieback of fronds, necrotic and brown streaking on the lower rachis base of older leaves, and necrosis of vascular bundles. Of 300 palms, there were 90 plants that were symptomatic and at least 4 were dead. Fusarium oxysporum Schlecht. emend. Snyder & Hansen has been consistently isolated from surface-sterilized petioles of symptomatic leaves sampled from affected palms. The opportunistic pathogen Gliocladium vermoesenii (Biourge) Thom was frequently associated with F. oxysporum in diseased samples, confirming previous reports of a disease complex between these two fungi (1). Five F. oxysporum isolates collected from different symptomatic plants were analyzed with a polymerase chain reaction (PCR)-based assay with the F. oxysporum f. sp. canariensis-specific primers HK66 + HK67 (2). The thermocycling schedule was as follows: initial denaturation at 94°C for 5 min, 35 cycles each of 1 min at 94°C, 1 min at 62°C, 1 min and 30 s at 72°C, followed by a final extension at 72°C for 5 min. A 567-bp PCR product of the expected size was obtained from all tested F. oxysporum isolates, allowing their identification as F. oxysporum f. sp. canariensis. This disease was previously reported from other Italian regions (Sicily, Marche, and Liguria), but its presence in Sardinia should be considered carefully since it represents a serious threat to ornamental palms, which are abundant all over the island. The source of this outbreak may be related to the importation of seedlings from areas where F. oxysporum f. sp. canariensis is widely established.

Black Dead Arm and Basal Canker of Vitis vinifera cv. Red Globe Caused by Botryosphaeria obtusa in Chile

Several years ago, Vitis vinifera cv. Red Globe vines (over 6 years old), started to show disease symptoms approximately 10 weeks after bud break. Symptoms first appeared on the leaves at the base of the shoots and then spread to other leaves, continuing to appear throughout the growing season. Two forms of the disease (severe and mild) were observed, each case leading to premature leaf fall. The severe form was characterized by dieback of one or more shoots accompanied by leaf drop and shriveling and drying of fruit clusters. The mild form was characterized by wine-red spots on the leaf margins or the leaf blade, which coalesced to form large zones of necrosis between the veins and the margins of the leaf. Fruit clusters may wither. If the bark is scraped off, a brown streak, 1 to 2 cm wide, was often seen in the wood. The streaking began at the base of the affected shoot and extended upward to the ground level, eventually resulting in a basal canker. Botryosphaeria obtusa (Schwein.) Shoemaker (anamorph = Sphaeropsis malorum Berk.) was isolated from 86% of samples from vines that were 6 to 10 years old from 12 locations in IV, V, VI, and metropolitan regions of Chile. Isolations were made from brownstreaked wood. Isolates were identified on the basis of a previous description (1,2) and internal transcribed spacer (ITSI-5.8S-ITS2) rDNA sequences identical to those of B. obtusa (culture KJ9356, GenBank Accession No. AF027759). B. obtusa is established as one of the main fungi associated with black dead arm of grapevine (2,3). Pathogenicity tests were completed by inoculating approximately 20 μl of mycelial suspension via injection into the pith of 16 single-node, rooted cuttings of V. vinifera cv. Red Globe. Sixteen control cuttings were injected with an equal volume of sterile distilled water. Twenty weeks after inoculation, all B. obtusa-inoculated cuttings exhibited brown streaks in the wood extending 50 to 60 mm from the point of inoculation. The wood streaking observed in inoculated plants was identical to symptoms observed in naturally infected black dead arm vines in the vineyard. No symptoms were observed in the controls. B.obtusa was reisolated from the region of brown streaking in all the inoculated cuttings. B. obtusa was not isolated from the water-treated controls. To our knowledge, this is the first report of B. obtusa causing black dead arm and basal canker on Red Globe grapevine in Chile. The fungal isolates have been deposited in the plant pathology laboratory of the Sanidad Vegetal Department of Agronomy Faculty of the University of Chile under the name V. vinifera/B. obtusa from N 1 to 16.

DNA Phylogeny, Morphology and Pathogenicity of Botryosphaeria Species on Grapevines

Several species of Botr yosphaeria are known to occur on grapevines, causing a wide range of disorders including bud mortality, dieback, brown wood streaking and bunch rot. In this study the 11 Botryosphaeria spp. associated with grapevines growing in various parts of the world, but primarily in South Africa, are distinguished based on morphology, DNA sequences (ITS-1, 5.8S, ITS-2 and EF1-α) and pathological data. Botryosphaeria australis, B. lutea, B. obtusa, B. parva, B. rhodina and a Diplodia sp. are confirmed from grapevines in South Africa, while Diplodia porosum, Fusicoccum viticlavatum and F. vitifusiforme are described as new. Although isolates of B. dothidea and B. stevensii are confirmed from grapevines in Portugal, neither of these species occurred in South Africa, nor were any isolates of B. ribis confirmed from grapevines. All grapevine isolates from Portugal, formerly presumed to be B. ribis, are identified as B. parva based on their EF1-α equence data. From artificial inoculations on grapevine shoots, we conclude that B. australis, B. parva, B. ribis and B. stevensii are more virulent than the other species studied. The Diplodia sp. collected from grapevine canes is morphologically similar but phylogenetically distinct from D. sarmentorum. Diplodia sarmentorum is confirmed as anamorph of Otthia spiraeae, the type species of the genus Otthia (Botryosphaeriaceae). A culture identified as O. spiraeae clustered within Botryosphaeria and thus is regarded as probable synonym. These findings confirm earlier suggestions that the generic concept of Botryosphaeria should be expanded to include genera with septate ascospores and Diplodia anamorphs.

DNA phylogeny, morphology and pathogenicity of Botryosphaeria species on grapevines

Several species of Botr yosphaeria are known to occur on grapevines, causing a wide range of disorders including bud mortality, dieback, brown wood streaking and bunch rot. In this study the 11 Botryosphaeria spp. associated with grapevines growing in various parts of the world, but primarily in South Africa, are distinguished based on morphology, DNA sequences (ITS-1, 5.8S, ITS-2 and EF1-α) and pathological data. Botryosphaeria australis, B. lutea, B. obtusa, B. parva, B. rhodina and a Diplodia sp. are confirmed from grapevines in South Africa, while Diplodia porosum, Fusicoccum viticlavatum and F. vitifusiforme are described as new. Although isolates of B. dothidea and B. stevensii are confirmed from grapevines in Portugal, neither of these species occurred in South Africa, nor were any isolates of B. ribis confirmed from grapevines. All grapevine isolates from Portugal, formerly presumed to be B. ribis, are identified as B. parva based on their EF1-α equence data. From artificial inoculations on grapevine shoots, we conclude that B. australis, B. parva, B. ribis and B. stevensii are more virulent than the other species studied. The Diplodia sp. collected from grapevine canes is morphologically similar but phylogenetically distinct from D. sarmentorum. Diplodia sarmentorum is confirmed as anamorph of Otthia spiraeae, the type species of the genus Otthia (Botryosphaeriaceae). A culture identified as O. spiraeae clustered within Botryosphaeria and thus is regarded as probable synonym. These findings confirm earlier suggestions that the generic concept of Botryosphaeria should be expanded to include genera with septate ascospores and Diplodia anamorphs.

Botryosphaeria species associated with diseases of grapevines in Portugal

Although Botryosphaeria species are known to cause cankers and dieback in many different woody hosts, their importance in grapevines has been largely ignored. Indeed, they are more often regarded as saprophytes or weak pathogens. In the work presented here the species of Botryosphaeria associated with wood and trunk diseases of grapevines in Portugal were determined. Three species, namely, B. obtusa, B. parva, and B. lutea, were regularly associated with trunk dieback, wood necrosis, brown wood streaking, cane bleaching or incomplete grafts. Botryosphaeria parva was the most common and widely distributed species. Botryosphaeria dothidea and B. stevensii were less common; the former was found on bleached canes and on necrotic tissues at the graft union while the latter was isolated from necrotic buds, and occasionally from brown streaks in the wood. These data indicate that B. parva is associated with many of the symptoms normally linked with infection by other fungi in the grapevine decline syndrome. To stimulate further research on this genus, descriptions of the species associated with grapevines and an identification key are provided.

Three-Year Observation of Grapevines Cross-Inoculated with Esca-Associated Fungi

Cross-inoculation experiments were carried out in southern Italy (Apulia) on grapevines cv. Italia and Matilde in order to study interactions among the white rot fungus Fomitiporia punctata (Fop) and two tracheiphilous hyphomycetes, Phaeoacremonium aleophilum (Pal) and Phaeomoniella chlamydospora (Pch), commonly associated with esca and brown wood-streaking of grapevine. In January 1999 the three fungi were inoculated through wounds on the trunks and spurs of cv. Italia, and branches and spurs of cv. Matilde. Pch, Pal and Fop were inoculated singly or in groups of two or three in all possible combinations. From the results so far obtained, the following conclusions can be drawn: 1. all three fungi are pathogenic; 2. inoculation of the above fungi on standing grapevines produces symptoms on trunks, shoots, leaves and berries that are reminiscent of those shown by esca-affected vines in the vineyard. In particular, symptoms in the wood (brown streaking, gummosis or “black goo”, and wood decay or white rot), and on the leaves (various forms of chlorosis, reddening and necrosis, distortion of the lamina) and berries (black measles) were reproduced; 3. severity of internal symptoms, assessed as length of brown streaks and intensity of colour change of the infected wood, varied with the growth and interactions between the inoculated fungi; 4. the wood streaking which developed after inoculation with Pal or Pch on the spurs extended to the supporting shoot or branch, and even to the stem; 5. a non-synergistic, competitive association of the two hyphomycetes, and an inhibition of Fop growth by Pal was observed in planta. A similar marked antagonistic effect of Pal against Fop was previously shown to occur when examining interactions between the three fungi in vitro; 6. the wood discolouration caused by Fop was not hampered by Pch, but it is always limited by Pal; 7. on the basis of internal symptoms, grapevines cv. Italia were more susceptible to the esca fungi than grapevines cv. Matilde.

Rootstock susceptibility to Phaeomoniella chlamydospora and Phaeoacremonium spp.

Summary. Twenty healthy cuttings each were inoculated artificially with Phaeomoniella chlamydospora, Phaeoacremonium inflatipes and Phaeoacremonium aleophilum. After the formation of callus, they were planted in pots. Approximately one year after inoculation, disease occurrence was recorded as the length of brown vascular streaking from the base of plant toward the shoot tip. Discolored areas were cultured on potato dextrose agar amended with tetracycline hydrochloride (PDA-tet) and pathogens were re-isolated. Inoculation with Pa. chlamydospora showed that rootstocks 3309, 420A, 110R, 5C, Schwarzmann, St. George, and Salt Creek were least susceptible, while 99R, 39-16, Freedom, Riparia Gloire, 140Ru, 16-16 and 1103 were most susceptible. When inoculated with Pm. inflatipes, 16-16, 3309, AXR1, Salt Creek, 110R, 5C, Freedom and 140Ru were least susceptible, while 420A, St. George, 161-49, and Harmony were most susceptible. Inoculation with Pm. aleophilum showed that 1103, 420A, Harmony, and Salt Creek were least susceptible, while 110R, SO4, 39-16 and 161-49 were most susceptible. The susceptibility of the rootstocks and the occurrence of vine decline in the field in California did not appear to be well correlated because 3309, 101-14, 5C, and 110R were always most susceptible. But these rootstocks are the most widely planted, and hence the natural occurrence of the disease is probably skewed towards these rootstocks. However, since no resistance was detected in our study, even though there was a wide range of susceptibility, the degree of rootstock susceptibility may not be such an important factor in disease expression under natural conditions.

Esca of Grapevine : A Disease Complex or a Complex of Diseases

Over the last few years research on esca has led to considerable progress in our understanding of the aetiology, epidemiology and physiology of the disease and revealed its complexity. On the basis of the available information, esca can be considered: 1. a disease complex, in the sense that several interacting factors and microorganisms concur to produce the overall syndrome; 2. a complex of at least two distinct diseases: ‘white rot’ caused by Fomitiporia punctata or other wood-rotting fungi, and brown wood-streaking and gummosis, caused by one or more species of Phaeoacremonium infecting the woody tissue; 3. a real hadromycosis induced by one or more species of Phaeoacremonium or related genera, which in mature or old grapevines is further complicated by the white rot caused by F. punctata. Research has also shown that different syndromes are produced depending on the origin of the infections, the prevalence of the associated fungi and the order in which they become active, and environmental factors. Five syndromes can be distinguished: 1. “brown wood streaking” (Petri, 1912). This affects rooted cuttings, rootstocks, and grafted or mother plants and is caused by species of Phaeoacremonium or related genera, often without external symptoms; 2. “Petri grapevine decline”. This name has been proposed to designate a decline of young grapevines known under various local names (‘black goo’, ‘slow dieback’, ‘Phaeoacremonium grapevine decline’), which occurs when propagation material or young grapevines are infected, again by species of Phaeoacremonium or related genera; 3. “young esca”. This syndrome, which Petri thought would evolve in ‘esca proper’, is characterised by black or brown wood-streaking and xylem gummosis in actively growing grapevines, with or without external symptoms. It is also caused by species of Phaeoacremonium or related genera, like the brown wood-streaking of point 1 above; 4. “white rot”. When infection is through wounds and solely or mainly by F. punctata or other wood-rotting basidiomycetes, it is characterised by wood rot, which may or may not be accompanied by external (leaf and fruit) symptoms; 5. “esca proper”. This occurs when white rot develops in the trunks of mature or old vines together with, or after, the development of brown wood-streaking. This, the full-fledged esca syndrome, is caused by the combined or successive action of one or more species of Phaeoacremonium, occasionally accompanied by other fungi, and F. punctata.

Occurrence and Symptom Expression of American Wheat Striate Mosaic Virus in Wheat in Kansas

Extracts of winter wheat with viruslike symptoms from Comanche County, Kans., did not react with antisera to viruses previously found infecting wheat in the state, nor was the virus mechanically transmissible to wheat, maize, or sorghum. Leaves of infected wheat developed thin, chlorotic striations that were more severe on the abaxial than adaxial surface. The virus reacted with American wheat striate mosaic virus (AWSMV) antiserum and was vectored by the painted leafhopper (Endria inimica), confirming the virus as AWSMV. A protein of 59 kDa, consistently detected in extracts of infected leaves, reacted with antiserum to AWSMV in Western blots. This is the first report of AWSMV in the Southern Great Plains region. Experiments showed that, on some cultivars, AWSMV caused brown necrotic streaking of culms and glumes, a symptom not described previously for wheat infected by this virus. Hard red winter wheat cultivars Ike, Karl, and TAM 107 had positive enzyme-linked immunosorbent assay values, but exhibited few or no symptoms.

Influence of age and territory quality on the reproductive behaviour of male Yellow Warblers

Individual male Yellow Warblers (Dendroica petechia) exhibit differences in their level of parental investment, which correlate with the amount of brown streaking on the breast. We tested two alternative hypotheses to explain these patterns. The age effect hypothesis proposes that the variation in plumage and parental behaviour is an effect of differences in male age. This was tested by analyzing the nest visit rates and plumage scores of banded males present in the study in more than 1 year. The age effect hypothesis is rejected because there was no evidence of significant within-male variation due to increasing age, nor of any consistent directional change in either parental effort or plumage pattern between years. The territory quality hypothesis proposes that the quality of territory occupied has an important proximate influence on male parental effort. By observing the same territories over different years we were able to compare nest visit rates of different males with different plumage scores while holding the effect of territory quality constant. Analysis of variance revealed that male plumage rank had a highly significant effect on nest visit rate, while the effect of territory occupied was not significant. Rejection of these two alternative hypotheses provides further support for the hypothesis that phenotypically different males are using alternative and irreversible lifetime reproductive strategies.

Differential allocation of reproductive effort to territorial establishment and maintenance by male yellow warblers (Dendroica petechia)

We tested the hypothesis that the basis of the variation in reproductive strategy among male yellow warblers (Dendroica petechia) is a tradeoff in the allocation of reproductive effort to intrasexual competition (territorial effort) and to parental care (parental effort). Since a negative correlation between level of parental effort and amount of brown streaking on the breast (plumage score) has already been demonstrated in this species, this study looked for evidence of a positive correlation of territorial effort with plumage score and a negative correlation with parental effort. Analysis of the spatial and temporal use of territories, prior to egg-laying, by males with different plumage scores supported the prediction that brighter (higher plumage score) males allocate more effort to territorial establishment and maintenance (Fig. 1). Male plumage score was positively and highly significantly correlated with six different measures of the relative amount of time spent, rate of energy expended, and risk of injury assumed by each male during territorial activities. The level of territorial effort was also found to be negatively correlated with the level of parental effort expended by the same males later in the season, confirming that there is a tradeoff in allocation of reproductive effort to these two major components. Further analysis revealed that territory quality was positively correlated with male plumage score (Figs. 3 and 4), while average nestling growth rate and other indices of reproductive success were not (Fig. 6). These results suggest that increased territorial effort by brighter males enables them to occupy higher quality territories where high levels of parental effort are not necessary to maintain high levels of reproductive success. Since reproductive success was not correlated with plumage score, this study further supports the differential allocation hypothesis that different males are using alternative strategies for the allocation of reproductive effort.

Evidence for reliable badges of status in territorial yellow warblers ( Dendroica petechia)

We examined the continuous variation in the breeding plumage of male yellow warblers ( Dendroica petechia) to determine if the amount of brown streaking on the breast functions as a badge of relative status in territorial males. Conspecific mounts differing in the amount of breast streaking were presented as simulated intruders to a sample of territorial males. Individual males exhibited higher levels of total aggressive response toward brighter models, i.e. those with more brown streaking. This indicates that the streaking is used to assess prospective opponents prior to a response, and that bright intruding males are regarded as more of a threat to the resident than are duller males. The level of response was also correlated with the brightness of the resident males. Bright males responded more aggressively than duller residents to model presentations, and also allocated more time and effort to territory maintenance. We conclude from this that bright males are signalling social dominance, but suggest that the proximate source of high status is a costly increase in the level of aggressive motivation, and not simply an intrinsic superiority in fighting competence. Thus the amount of brown streaking would be a reliable signal of the level of aggressive effort a male is willing to expend in escalating contests and defending resources. We propose that the reliability of the signal is ultimately maintained by the use of different but, overall, equally successful reproductive strategies by males of different appearance. An important implication of this is that ‘cheating’ on signalled status may be neither possible nor necessary.

Sexual selection and variation in reproductive strategy in male yellow warblers (Dendroica petechia)

Male yellow warblers (Dendroica petechia) exhibit extensive variation in the amount and conspicuousness of the sexually distinctive brown streaking on the breast. We investigated this intraspecific variation in degree of sexual dichromatism to see if male plumage rank (essentially the amount of brown streaking) is correlated with the amount of reproductive effort allocated to parental investment, as sexual selection theory would predict. As predicted, the average rate of feeding visits to the nest by males was negatively correlated with the plumage rank of the male in 1982 (Fig. 1) and 1983 (Fig. 2), and varied little between years or among study areas. Within one study area, the higher nest visit rate of dull (low plumage rank) males was correlated with higher nestling growth rates. But in the other two study areas, where bright (high plumage rank) males predominated, nestlings of bright males tended to have the highest growth rates despite minimal nest visit rates. Thus, overall there was no correlation between male plumage rank and nestling growth rate, a potential index of relative reproductive success, in either year (Figs. 3 and 4). This overall equal nest success likely helps to maintain the behavioral and plumage polymorphism. Since we could find no evidence that the high nestling growth rates of bright males were due to an adjustment of female parental effort to compensate for low male parental effort, there must be some other benefit of being bright which contributes to nest success. To address this, we used the relationship between parental feeding rates and nestling growth rates for each nest as an index of relative territory quality. This analysis suggests that bright males generally occupy the best territories available, possibly because they are more aggressive in obtaining and defending them than dull males. Dull males appear to be relegated to poorer territories, where an increase in male parental contribution would be necessary to achieve high nestling growth rates. We propose that different males are using alternative but evolutionarily stable reproductive strategies, in a way that is consistent with the predictions of sexual selection theory. Allocation of limited reproductive effort to parental investment decreases as sexual dichromatism increases, which probably reflects an increased investment in intermale competition for the best territories.

Infestation pattern of foliar nematode,Aphelenchoides ritzemabosi(Nematoda: Aphelenchoididae), on boysenberry

Abstract Infestation behaviour of the foliar nematode, Aphelenchoides ritzemabosi on boysenberry (Rugus strigosus) plants was studied in 2 commercial gardens at Motueka, South Island, New Zealand. Nematodes overwintered in the pruned stubs of old fruited canes, then invaded primocanes (new growth produced before winter) in early spring when plants broke dormancy, causing a brown streaking and epidermal peeling on stems. The nematode feeding site was directly beneath the cane epidermis, and conductive tissue remained protected by tough cork cambium. In well managed gardens infestation was restricted to the lower 1 m of the plant regardless of population density. Despite infestation, yields were high and no plant death, cane die-back, or bud death was noted. One garden had a disease symptomatic of crown gall, and a close association was found between the distribution of cane galling and nematode infestation within plants. Gall tissue yielded very high numbers of A. ritzemabosi. The behaviour of the nematode in relation to crop husbandry practices is considered in this paper and the need for cultural control methods is discussed.