Soaking grapevine cuttings in water: a potential source of cross contamination by micro-organisms

Grapevine nurseries soak cuttings in water during propagation to compensate for dehydration and promote root initiation. However, trunk disease pathogens have been isolated from soaking water, indicating cross contamination. Cuttings of Vitis vinifera cv. Sunmuscat and V. berlandieri x V. rupestris rootstock cv. 140 Ruggeri were immersed in sterilized, deionised water for 1, 2, 4, 8 and 16 h. The soaking water was cultured (25°C for 3 days) on non-specific and specific media for fungi and bacteria. The base of each cutting was debarked and trimmed and three 3 mm thick, contiguous, transverse slices of wood cultured at 25°C for 3 days. The soaking water for both cultivars became contaminated with microorganisms within the first hour. Numbers of fungi iso-lated from the wood slices soaked for one hour were significantly greater than those from non-soaked cuttings. The number of bacterial colonies growing from the wood slices increased after soaking for 2‒4 h in Sunmuscat. In a second experiment Shiraz cuttings were soaked for 1, 2, 4, 8 and 24 h. The soaking water became contaminated within the first hour but only the bacterial count increased significantly over time. Microorganisms also established on the container surfaces within the first hour although there were no significant increases over 24 h. These results confirm that soaking cuttings is a potential cause of cross contamination and demonstrate contamination of cuttings occurs after relatively short periods of soaking. Avoiding exposing cuttings to water will reduce the transmission of trunk diseases in propagation

Soaking grapevine cuttings in water: A potential source of cross contamination by micro-organisms

Grapevine nurseries soak cuttings in water during propagation to compensate for dehydration and promote root initiation. However, trunk disease pathogens have been isolated from soaking water, indicating cross contamination. Cuttings of Vitis vinifera cv. Sunmuscat and V. berlandieri x V. rupestris rootstock cv. 140 Ruggeri were immersed in sterilized, deionised water for 1, 2, 4, 8 and 16 h. The soaking water was cultured (25°C for 3 days) on non-specific and specific media for fungi and bacteria. The base of each cutting was debarked and trimmed and three 3 mm thick, contiguous, transverse slices of wood cultured at 25°C for 3 days. The soaking water for both cultivars became contaminated with microorganisms within the first hour. Numbers of fungi isolated from the wood slices soaked for one hour were significantly greater than those from non-soaked cuttings. The number of bacterial colonies growing from the wood slices increased after soaking for 2-4 h in Sunmuscat. In a second experiment Shiraz cuttings were soaked for 1, 2, 4, 8 and 24 h. The soaking water became contaminated within the first hour but only the bacterial count increased significantly over time. Microorganisms also established on the container surfaces within the first hour although there were no significant increases over 24 h. These results confirm that soaking cuttings is a potential cause of cross contamination and demonstrate contamination of cuttings occurs after relatively short periods of soaking. Avoiding exposing cuttings to water will reduce the transmission of trunk diseases in propagation. © Firenze University Press.Financial support by the ‘Programa de apoyo a la Investigación y Desarrollo (PAID-00-10) de la Universidad Politécnica de Valencia’ for David Gramaje during his three months in Australia is gratefully acknowledged. Financial support by Charles Sturt University and the Grape and Wine research and development Corporation for Helen Waite is also gratefully acknowledged.Peer Reviewe

Botryosphaeria stevensii infection of Pinot Noir grapevines by soil-root transmission

Botryosphaeria grapevine die-back is usually caused by infection of wounds in aerial parts of the grapevine. However, this study shows that Botryosphaeria stevensii infection can also be initiated from soilborne inoculum. Six months after soil inoculation with B. stevensii, shoots from two of six potted Pinot Noir vines were found to be infected with the fungus. This is the first report of infection grapevines by B. stevensii through soil–root transmission. Infection from soilborne inoculum has serious implications for vineyard replanting after removal of diseased vines

Financial comparisons of under-vine management systems in four South Australian vineyard districts

Conventional viticultural practice in Australia and elsewhere involves removal of under-vine vegetation using herbicides or cultivation. Concerns over the long-term effects of herbicides on soil health, evolution of resistant weeds and possible impacts on human health motivate the search for alternative weed management options. Industry-supported trials on commercial vineyards in four South Australian regions investigated standard practices of straw mulch and bare earth created with herbicides, compared to under-vine cover crops, focusing on soil health attributes (soil carbon, soil microbiological processes, etc.) and grape yields in 2016 and 2017. Measured yields with the Control (herbicide) treatment were combined with published district grape prices and yields over the 12-year (2006–2017) period, defining multivariate distributions of gross revenues ($/ha). Assuming all treatments produce grapes of equal quality and price as the Control, our results showed median per-hectare gross margins greater than the Control in the Barossa district, lower than Control in Riverland, and mixed results in Langhorne Creek and Eden Valley. Multi-year risk profiles, based on decadal whole-farm (50 ha) cash flows for each treatment, were calculated using Monte Carlo analysis, based on historical yield and price distributions. These risk profiles showed the under-vine treatments may result in major differences in long-term vineyard financial viability

Financial comparisons of under-vine management systems in four South Australian vineyard districts

Conventional viticultural practice in Australia and elsewhere involves removal of under-vine vegetation using herbicides or cultivation. Concerns over the long-term effects of herbicides on soil health, evolution of resistant weeds and possible impacts on human health motivate the search for alternative weed management options. Industry-supported trials on commercial vineyards in four South Australian regions investigated standard practices of straw mulch and bare earth created with herbicides, compared to under-vine cover crops, focusing on soil health attributes (soil carbon, soil microbiological processes, etc.) and grape yields in 2016 and 2017. Measured yields with the Control (herbicide) treatment were combined with published district grape prices and yields over the 12-year (2006–2017) period, defining multivariate distributions of gross revenues ($/ha). Assuming all treatments produce grapes of equal quality and price as the Control, our results showed median per-hectare gross margins greater than the Control in the Barossa district, lower than Control in Riverland, and mixed results in Langhorne Creek and Eden Valley. Multi-year risk profiles, based on decadal whole-farm (50 ha) cash flows for each treatment, were calculated using Monte Carlo analysis, based on historical yield and price distributions. These risk profiles showed the under-vine treatments may result in major differences in long-term vineyard financial viability

Bacterial inflorescence rot of grapevine caused by Pseudomonas syringae pv. syringae

Molecular sequencing (rpoB) and standard pathological and microbiological methods identified Pseudomonas syringae pv. syringae (Pss) as the causal agent of bacterial inflorescence rot of grapevines (Vitis vinifera) in three vineyards in Tumbarumba, NSW, Australia in 2006 and 2007. Pss strains from shrivelled berries and necrotic inflorescences of diseased grapevines were used to inoculate leaves and inflorescences of potted cv. Semillon grapevines. Pss caused disease symptoms similar to those experienced in the field, including angular leaf lesions, longitudinal lesions in shoot tissues and rotting of inflorescences from before flowering until shortly after fruit set. High humidity promoted symptom severity. The necrotic bunch stem and leaf lesions were susceptible to the development of Botrytis cinerea infections. Cryo-scanning electron microscopy (cryoSEM) indicated that Pss entered leaves and inflorescence tissues via distorted, open, raised stomata surrounded by folds of tissue that appeared as 'star-shaped' callose-rich complexes when viewed by UV light microscopy. In necrotic tissues, cryoSEM revealed Pss within petiole parenchyma cells and air-filled rachis xylem vessels. This is the first report of inflorescence and hence fruit loss caused by Pss in grapevines. The disease is described as 'bacterial inflorescence rot' and regarded as one that expands the previously reported pathology of grapevines caused by P. syringae. This study also indicated that infection by Pss might promote destructive B. cinerea infections when the fungus is already present but latent, although further experimentation is needed to prove such an interaction

Root infection of Vitis vinifera by Cylindrocarpon Iiriodendri in Australia

Cylindrocarpon liriodendri was isolated from the roots of diseased own-rooted grapevines (Vitis vinifera cv. Pinot Noir) from the Hunter Valley, New South Wales, Australia. Sequencing of the β-tubulin 2 gene established the identity of the pathogen as C. liriodendri. Soil/root inoculation of potted V. vinifera cv. Chardonnay vines resulted in symptoms typical of black-foot disease. This study has established the pathogenicity of an Australian isolate of C. liriodendri on V. vinifera

Effects of spray adjuvants on grape (Vitis vinifera) berry microflora, epicuticular wax and susceptibility to infection by Botrytis cinerea

Spray adjuvants were tested for their effects on epicuticular wax morphology, grape berry microflora and susceptibility of berries to Botrytis cinerea on Chardonnay, Shiraz and Cabernet Sauvignon cultivars. The four adjuvants used in this trial altered epicuticular wax morphology. Disintegration of the wax platelets was least for the wetter-spreader recommended for sensitive crops, and greatest for the crop oil concentrate and the activator-penetrant. Waxes did not regenerate over the season after treatment with the adjuvants. A cyprodinil/fludioxonil fungicide was effective at controlling B. cinerea infection, but when combined with an adjuvant, was less effective in the three grape cultivars. Irrespective of whether a fungicide was used, adjuvant application resulted in lower yeast and fungal populations on Chardonnay berries. There were no effects of the adjuvants on the microflora of Shiraz and Cabernet Sauvignon berries, except for the crop oil concentrate which resulted in higher bacterial populations on Cabernet Sauvignon berries. We hypothesise that spray adjuvants increased the susceptibility of grape berries to B. cinerea through epicuticular wax alteration and, in some circumstances, through the reduction of the indigenous microflora on the berry surface