ARC Infruitec Nietvoorbij

Stellenbosch, South Africa

ARC Infruitec Nietvoorbij

Stellenbosch, South Africa
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Jolly N.P.,ARC Infruitec Nietvoorbij | Varela C.,Australian Wine Research Institute | Pretorius I.S.,Macquarie University
FEMS Yeast Research | Year: 2014

Saccharomyces cerevisiae and grape juice are 'natural companions' and make a happy wine marriage. However, this relationship can be enriched by allowing 'wild' non-Saccharomyces yeast to participate in a sequential manner in the early phases of grape must fermentation. However, such a triangular relationship is complex and can only be taken to 'the next level' if there are no spoilage yeast present and if the 'wine yeast' - S. cerevisiae - is able to exert its dominance in time to successfully complete the alcoholic fermentation. Winemakers apply various 'matchmaking' strategies (e.g. cellar hygiene, pH, SO2, temperature and nutrient management) to keep 'spoilers' (e.g. Dekkera bruxellensis) at bay, and allow 'compatible' wild yeast (e.g. Torulaspora delbrueckii, Pichia kluyveri, Lachancea thermotolerans and Candida/Metschnikowia pulcherrima) to harmonize with potent S. cerevisiae wine yeast and bring the best out in wine. Mismatching can lead to a 'two is company, three is a crowd' scenario. More than 40 of the 1500 known yeast species have been isolated from grape must. In this article, we review the specific flavour-active characteristics of those non-Saccharomyces species that might play a positive role in both spontaneous and inoculated wine ferments. We seek to present 'single-species' and 'multi-species' ferments in a new light and a new context, and we raise important questions about the direction of mixed-fermentation research to address market trends regarding so-called 'natural' wines. This review also highlights that, despite the fact that most frontier research and technological developments are often focussed primarily on S. cerevisiae, non-Saccharomyces research can benefit from the techniques and knowledge developed by research on the former. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.


Fourie J.C.,ARC Infruitec Nietvoorbij
South African Journal of Enology and Viticulture | Year: 2011

Eight cover crop treatments were applied for 12 consecutive years on a medium textured soil in a vineyard near Robertson (33°50'S, 19°54'E). A treatment with full surface straw mulch combined with full surface post-emergence chemical control applied from just before grapevine bud break to harvest (BB) and another with no cover crop combined with BB was also applied. The control consisted of mechanical control in the work row and post-emergence chemical control in the vine row applied from bud break to harvest. In the BB treatments, grapevine shoot growth was signifcantly higher than in the treatment where a perennial cover crop was established in the work row during both the second (1993/94) and third (1994/95) season after the grapevines were established. The grape yield in all the BB treatments, except the one in which a mixture of Secale cereale L. v. Henog and Vicia faba L. v. Fiord was sown, was signifcantly higher than that of the control and the treatment in which a perennial cover crop was sown in the work row during the 1995/96 season. During the 2001/02 season, the grape yield of the BB treatment with a full surface straw mulch was signifcantly higher than that of all the other treatments. The different soil management practices had a signifcant effect on the N status of the juice, but did not affect wine quality.


The impact of fve drip irrigation strategies on water status in Merlot/99R was compared to a non-irrigated control (T1) in the coastal wine grape region of the Western Cape province, South Africa. Relationships between predawn (ΨPD), leaf (ΨL), stem (ΨS) and total diurnal (ΨTot ) water potential made it possible to classify grapevine water status in terms of ΨL, ΨS, or ΨTot according to previous classifcations derived from ΨPD. Around véraison, T1 grapevines already experienced moderate to strong water constraints (ΨS < -1.0 MPa), followed by strong to severe water constraints (ΨS < -1.4 MPa) prior to harvest. Irrigations at pea size, véraison and post-harvest, either applied in grapevine rows (T2) or work rows (T4), did not reduce water constraints compared to T1. However, irrigations at pea size, midway between pea size and véraison, at véraison, midway between véraison and harvest, and post harvest, either applied in grapevine rows (T3) or work rows (T5), reduced grapevine water constraints compared to T1. Irrigation in work rows did not affect grapevine water status compared to irrigation in grapevine rows. A partial root zone drying (PRD) strategy, obtained by switching subsurface irrigation in work rows between alternating rows at approximately 14-day intervals (T6), also reduced water constraints compared to T1. The water status in PRD grapevines clearly responded to the low plant available water (PAW) depletion levels in the alternating work rows in which irrigations were applied. There was minimal lateral fow of irrigation water from subsurface irrigation lines in the work rows towards the grapevine rows.


The impact of fve drip irrigation strategies on vegetative growth, yield and quality of Merlot/99R was compared to a non-irrigated control (T1) in the coastal region of the Western Cape province. Irrigations at pea size, véraison and post-harvest, either applied in grapevine rows (T2) or work rows (T4), tended to increase berry mass and yield compared to T1. More frequent irrigation at pea size, midway between pea size and véraison, at véraison, midway between véraison and harvest, and post-harvest, applied either in the grapevine rows (T3) or work rows (T5), increased berry mass and yield. A partial root zone drying (PRD) strategy, obtained by switching subsurface irrigation in the work rows between alternating rows at approximately 14-day intervals (T6), induced a similar trend. Under the given conditions, yield only increased when irrigation plus rainfall from bud break in September until harvest in February/March increased from ca. 200 mm to 400 mm. More water did not cause any further yield increases. Although low frequency irrigation increased yields compared to T1, it did not affect sensorial wine quality characteristics negatively. Non-irrigated grapevines produced the smallest berries, but did not necessarily produce wine superior in quality. The PRD strategy reduced wine quality, particularly when irrigation was applied at a high frequency between switches. The latter strategy only improved irrigation water productivity when compared to conventionally irrigated grapevines that received unnecessary high volumes of water. Subsurface irrigation applied in the work rows did not affect grapevine responses compared to irrigation in the grapevine rows.


Myburgh P.A.,ARC Infruitec Nietvoorbij
South African Journal of Enology and Viticulture | Year: 2012

Drip and micro-sprinkler irrigation systems were compared in a Thompson Seedless/Ramsey table grape vineyard in a weathered granite-gneiss soil in the Lower Orange River region. For each system, two different irrigation strategies were investigated. Drip irrigation frequencies of two days or longer, induced more water constraints in grapevines compared to micro-sprinkler irrigation applied at the same frequencies in the 1996/97 and 1997/98 seasons. Higher water constraints imposed by drip irrigation had negative effects on vegetative growth, berry size and grape quality compared to micro-sprinkler irrigation. However, responses of drip irrigated grapevines were comparable to micro-sprinkler irrigated grapevines when drip irrigations were applied daily in the 1998/99 and 1999/2000 seasons. Daily, early morning drip irrigation increased evapotranspiration (ET) by 6% compared to drip during the warmest part of the day. Drip irrigation suppressed weed growth considerably compared to micro-sprinklers. Daily ET of the drip irrigated grapevines was substantially lower compared to micro-sprinkler irrigated grapevines that received either two or three irrigations per week. In the case of micro-sprinklers, the higher frequency increased ET by 8% compared to the lower irrigation frequency. Since micro-sprinkler irrigation invariably produced higher yields than drip irrigation during the four seasons, it should be the preferred system for irrigation of table grapes under the given atmospheric and soil conditions. If water resources are limited, or if high water cost reduces table grape profitabifity, drip irrigation merits consideration as an alternative. However, daily drip irrigation will be required during the growing season to maintain acceptable yields and grape quality.


Fourie J.C.,ARC Infruitec Nietvoorbij
South African Journal of Enology and Viticulture | Year: 2012

Eight cover crop treatments were applied for 12 consecutive years on a medium-textured soil (18% clay) in a vineyard near Robertson (33°50'S, 19°54'E). Full surface mulching combined with full surface chemical control from bud break to harvest (BB), i.e. T3, and no cover crop combined with BB (T2) were also applied. The control (T1) consisted of mechanical control in the work row and chemical control in the vine row from bud break to harvest. After 10 years, the %C in the 0 to 600 mm soil layer of the minimum cultivated treatments increased, except in the 0 to 300 mm soil layer, in which Festuca arundinacae was established (T11), and the 150 to 300 mm soil layer, in which Vicia dasycarpa (grazing vetch) was controlled in the vine row from bud break and in the work row from berry set (end of November) (T7). The %C in the 0 to 150 mm soil layer of the cover crop treatments also exceeded the 0.9% level above which the application of N is deemed unnecessary on these soils. During the first three years the total inorganic N in the 0 to 600 mm soil layer of the treatments in which an N-fixing cover crop was sown was higher (mostly significant) than that of T1, T2, T3 and T11 during full bloom, véraison and post-harvest. Over the medium term, grazing vetch controlled chemically on the full surface from bud break (T6) caused the total inorganic N in the 0 to 600 mm soil layer during full bloom to exceed the level at which the grapevines need additional N. During véraison, this was achieved with T7. Over the long term this was achieved during full bloom with T6 and T7. During véraison, T7 gave a similar result. T3 or the use of annuals as winter-growing cover crops may supply the fertiliser needs of the grapevines post-harvest. Although differences in the P concentration and exchangeable Ca and Mg concentrations occurred between some treatments, no significant trends were observed. The level of K in all the treatments was between two and six times higher than the optimal level for the clay loam soils in the Breede River Valley.


Allsopp E.,ARC Infruitec Nietvoorbij
South African Journal of Enology and Viticulture | Year: 2010

Western flower thrips (WFT), Frankliniella occidentalis (Pergande), on table grapes in the Hex River Valley was monitored and its seasonal occurrence was investigated over three seasons. At the start of the growing season, blue sticky traps suspended from the overhead trellising structure to hang outside and under the vine canopy yielded similar WFT numbers. However, as the season progressed and vine canopies became denser, more WFT were caught on traps hanging outside the canopy in full sunlight than on traps hanging under the vine canopy. Female WFT became active in the vineyards after bud break and their numbers increased rapidly during flowering, peaking between October and January and declining rapidly thereafter. WFT were present in pre-bloom inflorescences and shoot tips before flowering, which means that monitoring should commence as soon as the first inflorescences are formed. No consistent relationship was found between economic damage at harvest and WFT numbers on sticky traps during flowering and berry set. Sticky traps should therefore only be used to determine the presence or absence of WFT in vineyards. The trap results suggest that there could be a constant influx of thrips into vineyards from alternate host plants in the surrounding area during the growing season. In vineyards with a history of WFT damage, control measures should be considered as soon as WFT is detected in order to prevent halo spot damage.


Fourie J.C.,ARC Infruitec Nietvoorbij
South African Journal of Enology and Viticulture | Year: 2010

Eight cover crop treatments were applied for 12 consecutive years on a medium-textured soil in a vineyard near Robertson (33°50'S, 19°54'E). A treatment with full surface straw mulch and full surface post-emergence chemical control applied from just before grapevine bud break to harvest (BB), and one with no cover crop combined with BB, were also applied. The control consisted of mechanical control in the work row and post-emergence chemical control in the vine row applied from bud break to harvest. Rotating Triticale v. Usgen 18 (triticale) and Vicia dasycarpa Ten. (vetch) did not improve the dry matter production (DMP) of either species. Average DMP decreased as follows: triticale > Secale cereale L. v. Henog (rye)/Vicia faba L. v. Fiord (faba bean) mixture > triticale/vetch biennial rotation > triticale/vetch annual rotation > vetch. Triticale (BB) resulted in total winter weed suppression from 1995 to 1996 and from 2001 to 2004. Total weed control from bud break to the pea size berry stage of the grapevines was achieved with straw mulch (BB), triticale (BB), rye/faba bean mixture (BB) and triticale/vetch rotated biennially (BB) from 2001 to 2003. For triticale combined with full surface post-emergence chemical control applied from grapevine berry set (AB), and for triticale/vetch rotated annually (BB), this was restricted to 2001 and 2003. From the pea size berry stage to harvest, straw mulch (BB), triticale (BB), vetch (BB), rye/faba bean mixture (BB) and triticale (AB) reduced the weed stand significantly in comparison to the control.


Western flower thrips (WFT), Frankliniella occidentalis (Pergande), causes russetting, pansy spot and silvering damage on plums. Despite routine insecticide applications for thrips control, some plum producers report economic losses due to pansy spot damage, pits and holes that render fruit unfit for export. Six commercial plum orchards in two climatic regions in the Western Cape Province, South Africa, were monitored to determine (1) why current management practices based on monitoring and insecticide applications failed to prevent damage in some orchards, and (2) whether WFT is responsible for pitting damage. Western flower thrips was the dominant thrips species in all orchards, though low numbers of Frankliniella schultzei Trybom also occurred. Blue sticky traps were more efficient for monitoring WFT and F. schultzei than yellow traps. Insecticide applications early in bloom and unfavourable weather conditions for thrips flight contributed to very low numbers of WFT on sticky traps during the flowering and fruit set periods. Flower dissections, however, revealed varying levels of oviposition damage to ovaries and fruitlets. Dissections confirmed that WFT enter flowers to lay eggs in the ovaries and other flower parts before petals are fully open. No consistent significant relationship between sticky trap counts and WFT oviposition damage to plums were found, therefore no treatment threshold level could be recommended. Insecticide applications during bloom limited thrips feeding damage, but were too late to prevent oviposition damage. Some oviposition sites developed into typical pansy spots, whilst others formed holes or pits that increased in size as the fruit matured. After insecticide applications ended, and as air temperature increased, WFT populations increased. Weeds and wild vegetation in and around orchards provide a continuous source of potential infestation for as long as the fruit remains attractive and vulnerable to WFT. As oviposition damage by WFT can occur before flowers open, and because of the risk to pollinators when insecticides are applied during flowering, a purely chemical control strategy does not appear to be feasible. A new approach to WFT management is required. © 2010 Elsevier Ltd.


The application of GA3 (gibbereffic acid), in combination with CPPU (N-(2-chloro-4-pyridinyl)-N'-phenylurea), may result in larger berries, but also decreases total soluble solids (TSS), increases total titratable acidity (TTA) and reduces grape skin colour. The purpose of this study was to determine a CPPU dosage that would improve berry size, without negative effects on other quality attributes of Flame Seedless, Redglobe and Crimson Seedless. The trials, which were conducted in the 2008/2009 season, comprised five treatments: control (standard GA3 application), seaweed extract plus GA3, and three dosages of CPPU in combination with GA3. CPPU dosages were 1,2 and 3 ppm for Flame Seedless; 3,4 and 5 ppm for Redglobe; and 2, 3 and 4 ppm for Crimson Seedless. The seaweed product used on Flame Seedless and Redglobe was derived from Ascophyllum nodosum, while a derivative of Ecklonia maxima was used on Crimson Seedless. Berry diameter, TSS, TTA, anthocyanin concentration, grape colour as well as cold storage defects were determined. CPPU dosages of 2,5 and 3 ppm significantly increased berry diameter in Flame Seedless, Redglobe and Crimson Seedless respectively. Five ppm CPPU increased Redglobe TSS. Three ppm CPPU increased TTA and decreased anthocyanin concentration in Crimson Seedless. The seaweed extract treatment resulted in firmer Flame Seedless berries with a higher anthocyanin concentration than the controL Seaweed extract also improved the firmness of Crimson Seedless compared to the controL Four ppm CPPU increased the percentage of Crimson Seedless total cold storage defects compared to the control.

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