Size Of Pea Research Articles

Berry thinning to reduce bunch compactness improves fruit quality of Cabernet Sauvignon (Vitis vinifera L.)

The effects of berry thinning on bunch compactness, grape sugar accumulation and subsequent wine quality were studied in Vitis vinifera L. Cabernet Sauvignon. The experiment was carried out during two consecutive seasons in a commercial vineyard. Berries of pea size were evenly removed manually to reduce berry density in bunches. Based on the decreasing proportion of berries in one bunch, the treatment was designated as C0 (control), C¼ (a 25% decrease) and C½ (a 50% decrease). The results showed that the different berry thinning treatment lowered bunch compactness accordingly. And the content of sugar, anthocyanins, total phenols, and mass of mature berries were all significantly enhanced with decreasing compactness on the same harvested time. However, the content of titratable acidity showed an inverse change. Compared with control, the sugar and anthocyanins of berry accelerated accumulation in loose bunches during grape ripening. Furthermore, the cell wall invertase (CWI) and soluble acid invertase (SAI) of berries had higher activity during grape ripening under treatments, which was associated with upregulated transcription level of VvCWI and VvGIN2. In addition, wines obtained from treatments had a higher total phenolic index, greater anthocyanins, and lower titratable acidity than the control wine. These results suggested that berry thinning with reducing bunch compactness might control accumulation of berry sugar by upregulating activities of CWIs and SAIs in berry and change berry main chemical component influencing the wine composition.

Whole-Plant Water Use in Field Grown Grapevine: Seasonal and Environmental Effects on Water and Carbon Balance.

Water scarcity is a main challenge in vineyards sustainability in most of the grapevine areas now and even more in near future due to climatic change perspectives. In consequence, water use efficiency (WUE) measurements are of the highest interest to improve the sustainability of this crop. The vast majority of WUE measurements relays on measurements of leaf carbon and water fluxes at leaf-level. However, less data are available at the whole-plant level, and for the moment those data are not totally coincident with conclusions reached at leaf scale. In this study, we used whole-plant chambers able to enclose an entire plant of 12 years old to measure at the same time water and carbon fluxes under realistic field grown conditions. The main objectives were to identify the technical issues interfering the whole-plant measurements and track the environmental and other abiotic factors that can affect water and carbon balance, i.e., WUE at the whole-plant scale. To achieve those objectives, we measured whole-plant water and carbon fluxes in grapevine exposed to two different water regimes at three phenological stages [pea size (July), ripening (August), and harvest (September)]. In September, measurements were repeated under high CO2 to also check its effect at the whole-plant scale. The results indicate that water and carbon fluxes are well coordinated under both water availability treatments. Under drought conditions, both fluxes were drastically reduced, but surprisingly the estimated WUE resulted not improved but decreased, contrarily to what is shown at the leaf scale. The phenology (September) also strongly decreased both water and carbon fluxes when compared to measurements in July. We hypostatized that harvest load respiration rates could have an important weight on the whole-plant net carbon exchange (NCE). Finally, high CO2 measurements, after correction for leaks, indicated an increase of whole-plant NCE as well as increased whole-plant WUE, as expected. Several technical issues were identified, like 1/instability of [CO2] during the night period that prevent robust estimation of whole-plant respiration and 2/condensation during last night and sun-rise hours which may affect the estimation of daily plant transpiration.

Di-1-p-menthene reduces grape leaf and bunch transpiration

Background and Aims Di-1-p-menthene, a film-forming antitranspirant, is reported to impede transpiration by acting as a physical barrier to water vapour loss from plant tissues. We tested this assumption on grapevine leaves across a range of temperature as well as on the bunch rachis and berries at several developmental stages. Methods and Results Gas exchange of Shiraz leaves was monitored at 20, 25, 30 and 35°C under controlled conditions after treatment with 1 and 2% di-1-p-menthene. Transpiration, photosynthesis and stomatal conductance were reduced at each temperature, but instantaneous water use efficiency (CO2 fixation relative to water loss) was improved only at 25 and 30°C. There was no further reduction in water use or improved water use efficiency with the application of a 2% over 1% emulsion. The antitranspirant was most effective when applied to the underside of the leaves, forming a physical barrier over the stomatal cavity without reduction in stomatal aperture. Di-1-p-menthene also curtailed bunch water loss in Merlot by lowering transpiration of both the rachis and berries at the fruitset, peppercorn, pea size and veraison stages, and at 20 and 25°Brix. Increasing the concentration of the antitranspirant from 1% to 2 or 3% added some benefit; however, this was dependent on the developmental stage. Both leaf and berry temperature was elevated by the spray application. Di-1-p-menthene did not interfere with flowering or promote fruit abortion when applied prior to capfall. Conclusion Di-1-p-menthene maintains berry turgidity through effects on both the canopy and the bunches themselves. Significance of the Study The antitranspirant, di-1-p-menthene, may provide protection against desiccation under field conditions and this will have implications for yield and berry composition.

Effect of leaf removal on grape and wine composition in ‘Merlot’

The adaptation to climate change requires the adjustments of viticultural practices, particularly changing the fruit to leaf area ratio which could be an effective option to maintain and enhance fruit and wine quality. Fruiting capacity and berry composition of grapevine are dependent on canopy area, with grapevine carbohydrate reserves affected by the crop load. 'Merlot' grapevines grown in the experimental vineyard of the NWGIC (South Eastern Australia) received treatments that altered the leaf area/fruit ratio. These received severe summer pruning (SSP), upper (ULR) and lower leaf removal (LLR) implemented at pea size during two growing seasons. Generally, all treatments lowered total soluble sugars, but the total sugar yield was not altered, also the total anthocyanins and phenolics of the berries did not differ at harvest. The titratable acidity and alcohol concentration of the wine was influenced by the change of the canopy size as were sensory attributes. Particularly, wines made from grapes of the SSP treatment were different in most attributes compared to wines that were made from grapes of untreated vines. The overall response of partial defoliation and severe summer pruning conducted prior to veraison suggests that it can be used as a management practise to alter berry ripening speed and grape composition, consequentially influencing wine attributes. However, depending on position, intensity and time the impact of such treatments on carbohydrate reserves in the perennial structure may have long-term implications.

Prevalence of Botrytis cinerea at different phenological stages of table grapes grown in the northern region of South Africa

Abstract Botrytis cinerea, is one of the major causal agents of postharvest decay in table grapes, contributing to 20% losses world-wide. The aim of this study was to determine the prevalence of B. cinerea at different phenological growth stage (full bloom, pea size and fully mature berries) and the impact of agro-climatic sites on pathogen incidence. Droplet digital polymerase chain reaction (ddPCR) was used simultaneously with culture based methods to detect and quantify B. cinerea. Botrytis cinerea was detected at different phenological stages on asymptomatic grape samples. Prevalence and level of B. cinerea differed between phenological stages and sites. Full bloom stage of site B showed the highest prevalence of B. cinerea (82.9%) compared to site A (33.3%). For the latter phenological stages (pea size and mature stage), site A had the highest prevalence (100% for both), compared to 35.2% and 44.4% observed at site B, respectively. Furthermore, the B. cinerea concentration varied between stages within the two sites. The concentration of B. cinerea at site A showed a threefold increase from pea size (2.67 copies μL−1 of DNA) to mature berry stage (9.16 copies μL−1 of DNA), compared with the decline noted for similar growth stages at site B. Botrytis cinerea inoculum build up on asymptomatic grapes could be effectively monitored as the berry develops at critical phenological stages. Preharvest monitoring of the pathogen can help growers improve well-established cultural and management practices, hence limit the risk of postharvest decay.

Examination of biogenic amines in grapevine musts originating from vineyards treated with different viticultural practices

ABSTRACTViticultural practices as defoliation (DF) and cluster tipping (CT) (hereinafter referred to as the abbreviation) are often used for crop regulation to enhance quality. Reduced yield can be accompanied not only with more favourable sugar-acid composition but also with changes of other chemical compounds in the berries, for example, biogenic amines as well. The latter play a significant role in human health. The experiment has been carried out at three different growing sites of Hungary in 2014. DF was done at full bloom, CT occurred when the berry reached pea size. Berry sampling for biogenic amine analysis was carried out several times during the ripening period. In our trial, we examined the effect of the above-mentioned treatments, the sites and the sampling dates on the amount of berries’ biogenic amine content. We concluded that DF and CT changed the amount of each type of amines in the berries. According to our measurements the treatments and the site did affect the amount and composition of biogenic amines, but the sampling time not. The treatments were most effective in the case of histamine which is crucial for triggering allergic reactions.

Assessment of the Short-Term Effectiveness of Kinesiotaping and Trigger Points Release Used in Functional Disorders of the Masticatory Muscles.

Chronic face pain syndrome is a diagnostic and therapeutic problem for many specialists, and this proves the interdisciplinary and complex nature of this ailment. Physiotherapy is of particular importance in the treatment of pain syndrome in the course of temporomandibular joint functional disorders. In patients with long-term dysfunction of masticatory muscles, the palpation examination can localize trigger points, that is, thickening in the form of nodules in the size of rice grains or peas. Latent trigger points located in the muscles can interfere with muscular movement patterns, cause cramps, and reduce muscle strength. Because hidden trigger points can spontaneously activate, they should be found and released to prevent further escalation of the discomfort. Kinesiotaping (KT) is considered as an intervention that can be used to release latent myofascial trigger points. It is a method that involves applying specific tapes to the patient's skin in order to take advantage of the natural self-healing processes of the body. The aim of the study was to evaluate the effect of the kinesiotaping method and trigger points inactivation on the nonpharmacological elimination of pain in patients with temporomandibular disorders. The study was conducted in 60 patients (18 to 35 years old). The subjects were randomly divided into two subgroups of 30 people each. Group KT (15 women and 15 men) were subjected to active kinesiotaping application. Group TrP, composed of 16 women and 14 men, was subjected to physiotherapy with the release of trigger points by the ischemic compression method. The results show that the KT method and TrP inactivation brought significant therapeutic analgesic effects in the course of pain-related functional disorders of the muscles of mastication. The more beneficial outcomes of the therapy were observed after using the KT method, which increased the analgesic effect in dysfunctional patients.

Use of growth regulator CPPU in harmonising the growth and quality of apple cv. Red Delicious

Two different stages, full bloom flowers and pea size fruits of ‘Delicious’ apple (Malus x domestica Borkh.) were sprayed single and repeatedly after 15 days during fruit sets with 0, 2.5, 5.0, 7.5 and 10 ppm CPPU {N-(2-chloro-4-pyridinyl)N-phenyl urea} in temperate conditions. Maximum fruit set increased 1.74 times with Sitofex application as compared to control. At both application times, the fruit length and diameter of treated fruit linearly increased with increasing concentration. Fruit length: diameter (L/D) ratios generally increased with higher doses. Fruit weight and volume significantly influenced with all CPPU concentrations. The maximum fruit volume increased by 79% with CPPU application as compared to control. Maximum yield 37.26 kg tree−1 with 10 ppm Sitofex was superior to 2.5, 5.0, 7.5 ppm Sitofex application. The yield was minimum in control, 28.09 kg tree−1. These effects either in an increase or decrease were associated with increasing Sitofex concentrations. Thus, proper PGR use could play an important role in providing higher quality products to their customers at lower cost.

Characterization of fungal communities of developmental stages in table grape grown in the northern region of South Africa.

To determine fungal communities that characterize table grapes during berry development. Two agro-ecologically different table grape commercial farms (site A and B) were used in this study. Samples were collected at full bloom, pea size and mature stages, from three positions (inside centre, eastern and western peripheral ends) per site. Total DNA extraction, Illumina sequencing and analysis of 18 pooled samples for fungal diversity targeting ITS1-2 generated a total of 2035933 high-quality sequences. The phylum Ascomycota (77.0%) and Basidiomycota (23.0%) were the most dominant, while the genera, Alternaria (33.1%) and Cladosporium (24.2%) were the overall dominant postharvest decay causing fungi throughout the developmental stages. Inside centre of site A were more diverse at full bloom (3.82) than those at the peripheral ends (<3.8), while at site B, the peripheral ends showed better diversity, particularly the eastern part at both full bloom (3.3) and pea size (3.7). Fungal population diversity varies with different phenological table grape growth stages and is further influenced by site and vine position within a specific vineyard. The information on fungal diversity and succession in table grapes during preharvest growth stages is critical in the development of a more targeted control strategy, to improve postharvest quality of table grapes.

Bunch sizing of ‘BRS Nubia’ table grape by inflorescence management, shoot tipping and berry thinning

Abstract ‘BRS Nubia’ is a new seeded table grape with dark black color, high yield, neutral flavor, and crunchy large berries. However, this cultivar frequently presents very dense bunches, limiting its commercialization. The aim of this work was to obtain uniform and loose bunches of ‘BRS Nubia’ table grape by means of inflorescence and bearing shoot management associated to berry thinning. The trial was conducted during two consecutive seasons of 2015 and 2016, in a 2-year old commercial vineyard located in Marialva, Parana, Brazil. The vines were trained in an overhead trellis system and spaced at 2.5 × 9.0 m distance. The experimental design was randomized block with four replications in a 2-factor arrangement with two additional treatments (factorial 2 × 2 + 2). The following factors were evaluated: inflorescence management (with tipping before anthesis and without tipping), bearing shoot tipping (before or after anthesis), and two additional treatments consisted of two controls (with or without berry thinning). The berry thinning was performed in all treatments, except in control without berry thinning, by means of picking when berries were at pea size. Physico-chemical analysis of the berries as well as bunch compactness and yield were evaluated at harvest time. Means were subjected to analysis of variance and compared using Tukey’s test at 5% probability. Additionally, the Principal Components Analysis (PCA) was used to describe the relation of physico-chemical and productive characteristics of grapes with the inflorescence and shoot management. The inflorescence tipping before anthesis is a useful practice by facilitating and saving time to perform berry thinning of ‘BRS Nubia’ table grapes, while the bearing shoot tipping after the anthesis may accelerate the bunches ripening. Combined to these practices, berry thinning is a mandatory procedure in order to obtain medium loose bunches of ‘BRS Nubia’ table grape, with larger and uniform berries.

The grapevine VvCAX3 is a cation/H+ exchanger involved in vacuolar Ca2+ homeostasis.

The grapevine VvCAX3 mediates calcium transport in the vacuole and is mostly expressed in green grape berries and upregulated by Ca 2+ , Na + and methyl jasmonate. Calcium is an essential plant nutrient with important regulatory and structural roles in the berries of grapevine (Vitis vinifera L.). On the other hand, the proton-cation exchanger CAX proteins have been shown to impact Ca2+ homeostasis with important consequences for fruit integrity and resistance to biotic/abiotic stress. Here, the CAX gene found in transcriptomic databases as having one of the highest expressions in grapevine tissues, VvCAX3, was cloned and functionally characterized. Heterologous expression in yeast showed that a truncated version of VvCAX3 lacking its NNR autoinhibitory domain (sCAX3) restored the ability of the yeast strain to grow in 100-200mM Ca2+, demonstrating a role in Ca2+ transport. The truncated VvCAX3 was further shown to be involved in the transport of Na+, Li+, Mn2+ and Cu2+ in yeast cells. Subcellular localization studies using fluorescently tagged proteins confirmed VvCAX3 as a tonoplast transporter. VvCAX3 is expressed in grapevine stems, leaves, roots, and berries, especially at pea size, decreasing gradually throughout development, in parallel with the pattern of calcium accumulation in the fruit. The transcript abundance of VvCAX3 was shown to be regulated by methyl jasmonate (MeJA), Ca2+, and Na+ in grape cell suspensions, and the VvCAX3 promotor contains several predicted cis-acting elements related to developmental and stress response processes. As a whole, the results obtained add new insights on the mechanisms involved in calcium homeostasis and intracellular compartmentation in grapevine, and indicate that VvCAX3 may be an interesting target towards the development of strategies for enhancement of grape berry properties.

Responses of Vitis vinifera L. cv. Sultanina to Water Deficits During Various Pre- and Post-Harvest Phases Under Semi-Arid Conditions

Performance of Sultanina grapevines irrigated at 60% plant-available water depletion (Tl) were compared to situations where water deficits were induced at budbreak (T2), before flowering (T3), after flowering (T4), at pea size (TS) and during ripening (T6). The field trial was performed on a fine sandy soil at Upington in the Lower Orange River region in South Africa. Treatments Tl to T6 were irrigated at 60% plant-available water (PAW) depletion during the post-harvest period and winter. A further four treatments were irrigated at 60% PAW depletion from budbreak until irrigation was terminated three weeks (T7), seven weeks (TS), eleven weeks (T9) and fifteen weeks (TlO) after harvest, respectively. The periods of water stress induced during the various pre-harvest phenological phases were too short to have a significant effect on vegetative growth. Water deficits during the early season (T2, T3 and T4) tended to affect yield more negatively than deficits applied between pea size and harvest (TS and T6). Yield reduction was associated with tendencies toward reduced bunch differentiation, berry shed and smaller berries. Berry size was significantly reduced by water deficits induced after flowering (T4). Water deficits had no significant effect on juice sugar content or on total titratable acids. No choice-grade sun-dried raisins could be produced when grapevines were subjected to water deficits during ripening (T6). In comparison to continued irrigation at 60% PAW depletion and water deficits induced up to pea size, significant browning of dipped raisins produced from TS and T6 grapevines occurred during some seasons. In combination with low relative humidity, water deficits between pruning and budbreak (T7 to TlO) reduced yields significantly compared to continued irrigation at 60% PAW depletion throughout the post-harvest period. Low relative humidity and dry soil also induced delayed budbreak and stimulated excessive shoot growth after harvest to such an extent that cane mass was significantly higher compared to irrigation at 60% PAW depletion. Neither water deficits nor significant shoot regrowth during the post-harvest period had any effect on cane starch content at pruning.

The Effect of Partial Defoliation, Leaf Position and Developmental Stage of the Vine on Leaf Chlorophyll Concentration in Relation to the Photosynthetic Activity and Light Intensity in the Canopy of Vitis vinif era L. cv. Cabernet Sauvignon

The effect of partial defoliation and leaf position on leaf chlorophyll concentration in relation to the photosynthetic activity and light intensity in the canopy of Vitis vinifera L. cv. Cabernet Sauvignon was investigated at berry set, pea size, veraison and ripeness stages. The leaves of the severely defoliated vines appeared to contain the highest chlorophyll concentration. In general, chlorophyll a decreased as the leaves were situated progressively deeper into the canopy. No consistent relationship between chlorophyll concentration, light intensity and photosynthetic activity could be found for the different leaf positions. However, to obtain leaves that photosynthesize optimally, the amount and time of leaf removal in the grapevine canopy must be carefully planned.

Distribution of 14C-Photosynthetate in the Shoot of Vitis vinifera L. cv Cabernet Sauvignon II. The Effect of Partial Defoliation

The effect of partial defoliation of Vitis vinifera L. cv Cabernet Sauvignon on the distribution of photosynthetates, originating in leaves in different positions on the shoot at berry set, pea size, veraison and ripeness stages, was investigated. Partial defoliation (33% and 66%) resulted in a higher apparent photosynthetic effectivity for all the remaining leaves on the shoot. The pattern of distribution of photosynthetates would seem to stay the same between the defoliation treatments. The control vines were found to carry excess foliage. Optimal photosynthetic activity of all the leaves on the vine was therefore not reached.

The Effect of Partial Defoliation on Quality Characteristics of Vitis vinifera L. cv. Cabernet Sauvignon Grapes 1. Sugars, Acids and pH

The effect was studied of partial defoliation (33% and 66%) on the sugar and acid accumulation and pH in grapes of Vitis vinifera L. cv. Cabernet Sauvignon. Although the total soluble sugar (TSS) in grapes of partially defoliated vines was significantly higher than that of non-defoliated vines in some cases, no significant differences were generally found. No significant differences in total titratable acidity (TT A) were found between treatments. The timing of defoliation had no effect on TSS in grapes, whereas TT A tended to be higher the earlier partial defoliation was commenced. In general, 33 % and 66% defoliated vines respectively produced approximately 33 % and 200% more TSS and TT A in the fruit per cm2 leaf area than non-defoliated vines. No significant differences between defoliation treatments were found on a per gram dry berry mass or per berry basis for glucose and fructose or tartaric and malic acid. However, 66% defoliated vines had significantly less soluble solids in berries per shoot, which was probably caused by a lower total berry mass per shoot. Although no significant differences in sugar composition could be found between defoliation treatments, tartaric acid levels tended to be higher and malic acid levels lower as a result of partial defoliation. Partial defoliation had no effect on the accumulation patterns of sugars and acids. Glucose dominated in berries at veraison, with fructose dominating at ripeness. The highest total tartaric and malic acid concentrations occurred at pea size. Malic acid content decreased rapidly from veraison, whereas the decrease in tartaric acid was not pronounced. Must pH was not affected by partial defoliation. The results seem to suggest that the general metabolism of vines was favourably changed by partial defoliation, mainly in terms of a more favourable source: sink ratio, more efficient photosynthesis, and an improved canopy microclimate.

The Effect of Partial Defoliation on Growth Characteristics of Vitis vinif era L. cv. Cabernet Sauvignon IL Reproductive Growth

The effect of partial defoliation over the whole canopy on the reproductive growth of Vitis vinifera L. cv. Cabernet Sauvignon was investigated. The 33% defoliation treatment prior to pea size and the 66% defoliation treatment prior to veraison adversely affected fresh mass per berry and yield at harvest. The 33% defoliation treatment from veraison increased fresh berry mass. Partial defoliation had no effect on berry water content. Dry matter started to accumulate rapidly only from after pea size stage. The fresh berry mass:cane mass ratio increased with partial defoliation from veraison. Leaf area/g fresh mass results indicated that control vines carried excess foliage which prevented maximum photosynthetic activity. Partial defoliation of the canopy improved budding percentage, generally increasing with increasing defoliation, whereas bud fertility was improved only by 33% defoliation. In general, leaf removal from bud break and berry set was more effective in improving budding, whereas bud fertility was favoured by partial defoliation from bud break.

Distribution of 14C-Photosynthetate in the Shoot of Vitis vinifera L. cv Cabernet Sauvignon I. The Effect of Leaf Position and Developmental Stage of the Vine

The distribution of photosynthetates, originating in leaves of different parts of the shoot of Vi tis vinifera L. cv Cabernet Sauvignon at berry set, pea size, veraison and ripeness stages, was investigated. Specific photosynthetic activity of the CO,-treated leaves gradually decreased during the season. Photosynthetates were hoarded in the leaves at berry set, but were increasingly diverted to the bunches after that. The apical leaves displayed the Itlghes.t.photosynthesis. The leaves opposite and below the bunches accumulated very little photosynthetafes, especially from veraison to ripeness. Redistribution of photosynthetates among the basal, middle and apical leaves was generally very restricted at all stages. Multidirectional distribution from the site of application of 14CO, occurred at berry set stage, while from pea size to ripeness photosynthetates were mainly translocated basipetally. Highest accumulation in the bunches occurred at veraison, while the basal leaves were primarily used to nourish the bunch.

The Effect of Partial Defoliation on Growth Characteristics of Vitis vinifera L. cv. Cabernet Sauvignon I. Vegetative Growth

The effect of partial defoliation over the whole canopy on the reproductive growth of Vitis vinifera L. cv. Cabernet Sauvignon was investigated. The 33% defoliation treatment prior to pea size and the 66% defoliation treatment prior to veraison adversely affected fresh mass per berry and yield at harvest. The 33% defoliation treatment from veraison increased fresh berry mass. Partial defoliation had no effect on berry water content. Dry matter started to accumulate rapidly only from after pea size stage. The fresh berry mass:cane mass ratio increased with partial defoliation from veraison. Leaf area/g fresh mass results indicated that control vines carried excess foliage which prevented maximum photosynthetic activity. Partial defoliation of the canopy improved budding percentage, generally increasing with increasing defoliation, whereas bud fertility was improved only by 33% defoliation. In general, leaf removal from bud break and berry set was more effective in improving budding, whereas bud fertility was favoured by partial defoliation from bud break.

Application of Fungicides Against Postharvest Botrytis Bunch Rot of Table Grapes in the Western Cape

Fungicide programmes for the control of postharvest Botrytis bunch rot on table grapes were evaluated in six trials from 1984/85 to 1991/92 in the Western Cape. The study demonstrated the ineffectiveness of dicarboximide applications during bloom to early pea size in well managed vineyards. Dicarboximides were most effective when applied from bunch closure to ripening. lprodioue/sulphur treatments at veraison and before harvest reduced Botrytis bunch rot, but they were ineffective in inhibiting infection during storage. Control was only achieved when grapes were exposed to S02 during storage. Although bunch dip treatments reduced infection in the vineyard, this control was not commercially acceptable. Therefore no real advantage was found when bunches were dipped in fungicide at veraison to ensure better coverage. The fact that berries became infected primarily during harvest, package operations and storage, emphasised the necessity for reducing B. cinerea inoculum on harvested grapes. It is suggested that the results of this investigation may lay the foundation for incorporating biological control in Botrytis bunch rot control.

Water Status,Vegetative Growth and Yield Responses of Vitis vinifera L. cvs. Sauvignon blanc and Chenin blanc to Timing of Irrigation during Berry Ripening in the Coastal Region of South Africa

The effects of additional irrigation during berry ripening on water relations, growth and yield in Sauvignon blanc and Chenin blanc grapevines were investigated. In all treatments the grapevines were irrigated when berries reached pea size in December. One treatment received no further irrigation until after harvest. All of the remaining treatments received a second irrigation at veraison. Except for a single treatment, which was not irrigated during ripening, these treatments received a third irrigation at either 14, 21, 28 or 31 days after veraison. The six treatments were applied in a field trial carried out in the Stellenbosch district of the coastal winegrowing region of South Africa over consecutive seasons, between 1990 and 1993. Irrigation at pea size berries and at pea size berries plus veraison increased leaf water potential, but did not affect vegetative growth and yield in either cultivar. Relative to a single application at pea size berries, irrigation at pea size, at veraison and during ripening increased berry size in both cultivars, though not consistently, over the three seasons. However, this result must be viewed in terms of the fact that qualitative assessments of root development and distribution have revealed that effective soil preparation contributes to well-developed root systems. Results confirmed that these root systems could sustain vegetative growth and yield where a single irrigation was applied at pea size berries compared with additional irrigations applied at veraison and during ripening. Irrigation applied at, and after, veraison resulted in yield losses of both cultivars when rainfall favoured Botrytis cinerea infection.