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Background and aims: A better understanding of plant carbon assimilation, water status and photosystem performance responses to combined heat and drought stress would help to optimize grapevine management under such limiting conditions. Methods: Gas exchange and chlorophyll fluorescence parameters were measured in potted grapevines, cv Sauvignon Blanc, before, during and after simulated six-day heat (Tmax = 40 °C) wave using heated well-watered (HW), heated drought-stressed (HD), non-heated well-watered (CW) and non-heated dry (CD) vines. Results: Photosynthesis and stomatal conductance in HW vines increased during the morning and dropped in the afternoon with respect to CW vines. Daily plant transpiration in HW almost doubled that of CW vines. When grapevines were already exposed to drought, the effects of the heat wave were negligible, with HD plants showing similar leaf photosynthesis and transpiration to their CD counterparts. Heat, but not drought stress, decreased the maximum (Fv/Fm) and effective photochemical quantum yield of PSII (φPSII), and also affected the use of absorbed energy. HW plants dissipated more radiative energy as heat, a protective mechanism of the photosystem, while HD vines increased the energy dissipated by non-regulated non-photochemical pathways, which might lead to photoinhibition damages. The different behavior could be due to the enhanced transpiration rate and consequent decrease in leaf temperature in HW as compared to HD vines. After the heat wave, only HW vines recovered the afternoon values of photosynthesis, stomatal conductance and φPSII to similar levels as those in CW vines. Conclusion: Drought had a more significant effect than heat stress on photosynthesis, stomatal conductance and transpiration. The combined heat and drought stress, however, increased the proportion of energy lost by the leaves through harmful non-regulated dissipative pathways. With adequate soil water availability, grapevines withstood the heat wave period through an increase in leaf transpiration, which decreased leaf temperature and protected the PSII from heat damage. Highlights: Drought had a stronger impact on gas exchange parameters than elevated temperature during a simulated heatwave, while heat stress was the main driver of PSII functionality and absorbed energy partitioning. Well-watered grapevines were able to recover their physiological function after a six-day heatwave (Tmax 40 °C), while plants under heat and drought stress were unable to resume PSII performance after one day of recovery. [ABSTRACT FROM AUTHOR]

In this study, the cold hardiness degrees of the main grape cultivars grown in the temperate climatic conditions of Samsun province, Turkiye were determined using the tissue browning technique. Winter canes were prepared as single nodes cuttings in the coldest month of February. After an artificial freeze test, LT50 degrees of primary, secondary, tertiary buds, and phloem tissue were determined. In addition, after the freeze test, some growth and rooting parameters of single-bud cuttings were examined in a growing room condition. The highest LT50 values in primary, secondary, and tertiary buds were observed in 'Karaerik', 'Alphonse Lavallee', 'Çeliksu' and 'Merzifon Karası' cultivars. Highest primary bud LT50 values were obtained as – 24.3 °C in 'Karaerik', – 23.1 °C in 'Çeliksu', – 22.9 °C in 'Alphonse Lavallee', and – 22.1 °C in 'Merzifon Karası' cultivars. The lowest primary bud LT50 values were found in 'Narince', 'Çavuş', and 'Trakya İlkeren' cultivars (– 11.0 °C, – 12.1 °C, and – 16.1 °C, respectively). While phloem viability rate was 77.3% in 'Çeliksu', it was determined as 8.0% in the 'Çavuş' cultivar. The highest primary, secondary, and tertiary bud viability was determined in the 'Karaerik' cultivar (64.7%, 67.3%, and 68.0%, respectively). On the other hand, the least bud viability rates were obtained in 'Çavuş', 'Narince', and 'Trakya İlkeren' cultivars. In the growing room condition, the highest mean bud burst (60.7%), bud sprouting ratio (61.0%), and cluster number per shoot (0.42 cluster) were obtained in the 'Çeliksu' cultivar in growing room condition. The highest mean shoot length (4.8 cm), rooting ratio (59.3%), root length (4.10 cm), and root scale (1.19) were determined in the 'Karaerik' cultivar among freeze applied cuttings. [ABSTRACT FROM AUTHOR]

Phenolic compounds are plant secondary metabolites with strong antioxidant potential. They are involved in stress tolerance, plant defense mechanism, and protection against environmental factors. Due to their medicinal and antioxidant properties, they have been part of the human diet for centuries. They also affect the overall quality of the grapes for commercial use. Fruit color is one quality attribute that is directly influenced by the production of anthocyanins in the berry skin. The production of anthocyanins is, however, linked with the production of abscisic acid. This review is focused on the production of different phenolic compounds in grapes, the role of abscisic acid in the production of anthocyanin contents through the phenylpropanoid pathway, and its effect on color development and final quality. [ABSTRACT FROM AUTHOR]

The lack of winter cold is a severe limitation for the cultivation of grapevines (Vitis vinifera L) in areas with warm winter climates. This phenomenon is currently becoming quite important due to global warming, which will increase winter temperatures in many temperate regions of the planet where grapevines are cultivated. Although various physical and chemical stimuli have been used to address the lack of winter cold in grapevine cultivation, quantitative studies on its effects on different cultivars are limited. Here, the effects of (a) low temperatures during endodormancy (ED), (b) temperature increases during eco-dormancy (ECD) and (c) the effects of dormancy-breaking compounds such as hydrogen cyanamide (HC) and sodium azide (AZ) on the budburst of an early budbreak cultivar, Chardonnay, and an late budbreak cultivar, Thompson seedless, were assessed. The results were analysed by the Kaplan–Meier method, and the log-rank test was used to establish statistical significance between the control and treatments. In general, Chardonnay grapevines were more sensitive than Thompson seedless grapevines to all budbreak stimuli, and a temperature increase during ECD was the stimulus that had the greatest effect on the budbreak in both cultivars. Exposure to cold temperatures during ED increased the cold hardiness and improved the budbreak in both cultivars. Based on the results, a relationship between the degree of bud cold hardiness and budbreak potential is suggested, and it is proposed that the greater the cold hardiness achieved by the buds, the better their subsequent budbreak will be. [ABSTRACT FROM AUTHOR]

Organically produced conventional products have gained great attention in accordance with the increasing awareness on healthy foods as well as improvements in living standards. Environment friendly strategies to extend the quality of grapes after commercial maturity provide healthy and profitable sustainability in market chain. In the present study, possibilities to maintain the quality of grape clusters on grapevines without any chemical treatments have been studied under vineyard conditions in temperate climate characteristics of Konya Province in Central Anatolia. Grape clusters of 'Alphonse Lavallée' and 'Narince', one of the most popular conventional grape cultivar in Turkey, were kept on the vines trained with bilateral cordon system. The vines were drip irrigated during the hot summer and the vine canopy was covered with black nets after veraison to protect from the birds, hail and climatic extremities. After commercial maturity, twelve cluster samples per cultivar were collected with monthly intervals to investigate the changes in quality. Up to the 3rd sampling date (at the end of November 2019), little losses in quality features were determined in both cultivars. At the end of the study, at 4th moth (December), significant decay incidences were observed with similar patterns in cultivars. General findings demonstrated that the grape clusters could be maintained on grapevines under intact condition of the cool autumn season in temperate zone by protecting them from the external damages using convenient protective materials up to three or four months depending on the response of cultivars to environmental variables. [ABSTRACT FROM AUTHOR]

Key message: The structural differences of MYB14 promoter in two grapevine genotypes affect the expression of MYB14 and stilbene synthesis in response to Al3+ and UV-C radiation.Abstract: Grapevines provide an important fruit crop worldwide, but production is often limited by pathogen infection. Stilbenes, a class of secondary metabolite, represent phytoalexins that contribute to defence against pathogens in many plants, including grapevine. It is known that the transcription factors MYB14 and MYB15 are required for the activation of the promoters of resveratrol synthase to regulate stilbene biosynthesis. In the current study, we observed that stilbene levels were more highly induced by Al3+ and UV-C radiation treatments in the cultivar Vitis labrusca 'Concord' than in the cultivar V. vinifera 'Cabernet Sauvignon'. We investigated whether genetic/structural variations in the MYB14 and MYB15 promoters between these two representative genotypes are responsible for the differences in stilbene accumulation. Significant differences in the structure and activity of the promoter of MYB14, but not MYB15 were identified between the two genotypes, following heterologous expression in Nicotiana benthamiana system and treatments with Al3+ and UV-C. Hydrogen peroxide (H2O2) was detected in Concord soon after the stress treatments, but after diphenyleneiodonium chloride pre-treatment, the expressing level of VlMYB14, the promoter activity of VlMYB14 and the accumulation of stilbenes was significantly reduced. A model is presented where the induction of MYB14 contributes to stilbene accumulation in Concord following Al3+ and UV-C treatments involving reactive oxygen species (ROS) production as an early signal. [ABSTRACT FROM AUTHOR]

Botryosphaeria dieback caused by species of Botryosphaeriaceae is an economically significant disease of grapevine worldwide including in Australia and New Zealand. Symptoms such as dieback of the shoots and cordons, cankers, stunted shoots, bunch rot and bud necrosis are observed, eventually leading to yield loss and reduced grapevine longevity. The disease was first recognised as an important issue in vineyards in Australia and New Zealand in the early 2000s and since then, considerable research has been conducted for better understanding of the causal organisms and their management. However, there is also a need to better understand the role of nursery planting material as a potential source of infection in new or replanted vineyards. This review reports on the current knowledge of Botryosphaeriaceae in grapevines in Australia and New Zealand including their identification, distribution across various wine grape growing regions, symptomatology, pathogenicity, epidemiology and management strategies. Future strategies to increase our knowledge and to better manage these economically important pathogens are discussed. [ABSTRACT FROM AUTHOR]

Main conclusion: Bud-break assays under forced growth conditions suggest that a drop in ABA content and an increase in sugars are common features in the sprouting of paradormant (PD) and endodormant (ED) grapevine buds. However, increases in cell division and in respiration are unique characteristics of the ED budding.In tropical and subtropical regions where the variations in day length and temperatures are minor throughout the year, the rupture of grapevine buds can be achieved during the current growing season given rise to a double-cropping system annually. However, it is unknown whether the breaking buds are in the paradormancy (PD) or endodormancy (ED) stage. In this study, we compared the breakage of PD and ED buds under conditions of forced growth. To do this, the expression of genes related to the metabolism of phytohormones and sugars, and of relevant physiological functions such as respiration and cell division was analyzed temporally throughout the incubation period in both types of buds. An early fall in the expression of the ABA biosynthesis gene (VvNCED1) and increases in genes related to sugar metabolism and transports were observed during the incubation period in both types of buds. However, while in the PD buds, the genes related to respiration and the cell cycle did not undergo significant changes in their expression during the incubation period, in the ED buds, the expression of these genes together with those related to auxin and cytokinin biosynthesis experienced a large increase. The results suggest that a drop in ABA content and an increase in sugars are early signals for the onset of bud break in both PD and ED vines, while the increase in respiration and cell division are unique characteristics of the ED buds, which reflect its transition from a resting state to a state of active growth. [ABSTRACT FROM AUTHOR]

Practical use of plant growth-promoting rhizobacteria (PGPR) on plants under stress conditions remains elusive because most of the studies focused on merely evaluating the plant growth-promoting effects on non-stressed plants. This study focused on the effect of root inoculation of different PGPRs on the growth and physiology of grapevine rootstocks 41 B, 99 R and 140 Ru grown in soilless culture with elevated pH. The rootstocks in pots under glasshouse condition were inoculated with Agrobacterium rubi A18 and Bacillus subtilis OSU 142 bacteria in early spring. To increase the pH of growth medium, the plants were watered with 250 mL plant−1 bicarbonate solution (840 g L−1 NaHCO3) four times (beginning at 3-4 cm shoot growth) with one-month interval during the vegetation. Along with the bicarbonate supplementation to growth medium, root rhizosphere pH increased from an initial value 7.76 to the final values between 8.10 and 8.26. Although the bacteria population decreased progressively, they were able to alleviate the negative effects of high pH by improving vegetative growth, leaf physiology and nutrient acquisition in many cases. The bacteria strains employed in this study can be recommended to support grapevine growth and physiology under alkaline conditions for a sustainable and environment-friendly viticulture. [ABSTRACT FROM AUTHOR]

Grapevine downy mildew (Plasmopara viticola) is a serious economic disease for Australian viticulture. Using different detection techniques 51 new and revised microsatellite primers have been developed for P. viticola based on American and European isolates. Thus far, only a subset of the developed microsatellites have been tested for polymorphisms among Australian P. viticola populations. This study tests all 51 microsatellites, under the same PCR conditions, for polymorphism on Australian isolates from geographically distinct regions. Of the 51 microsatellites, 18 showed polymorphism between the isolates tested and or P. viticola GenBank sequences. A selection of these microsatellites will be used for a larger population analysis study on Australian isolates. [ABSTRACT FROM AUTHOR]

Arabis mosaic virus (ArMV) is one of several nepoviruses responsible for infectious degeneration disease of grapevines worldwide. To characterize ArMV isolates from grapevines in Iran, total RNA was extracted and the coat protein (CP) gene was amplified by RT-PCR using specific primers and sequenced. The completed CP gene nucleotide sequence of two Iranian isolates was 1518 nt long with 505 amino acids. A phylogenetic tree using CP gene sequences showed three groups, which were strongly supported by bootstrap analyses. Most of the isolates from Europe clustered in two main groups I and II and the two Iranian isolates clustered with a German isolate in group III. The pairwise nucleotide distances within ArMV isolates were 0.0–20.4% with the lowest diversity among isolates of group I followed by isolates of groups II and III. [ABSTRACT FROM AUTHOR]

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Main conclusion: In grapevines, the increased expression of VvFT , genes involved in the photoperiodic control of seasonal growth ( VvAP1, VvAIL2 ) and cell cycle genes ( VvCDKA, VvCDKB2, VvCYCA1, VvCYCB, VvCYCD3.2 ) in the shoot apex relative to the latent bud, suggests a high mitotic activity of the apex which could prevent them to enter into endodormancy. Additionally, the up-regulation of these genes by the dormancy-breaking compound hydrogen cyanamide (H CN ) strongly suggests that VvFT plays a key role in regulating transcriptionally cell cycle genes. At the end of the growing season, short-day (SD) photoperiod induces the transition of latent grapevine buds ( Vitis vinifera L) from paradormancy (PD) to endodormancy (ED), which allows them to survive the cold temperatures of winter. Meanwhile, the shoot apex gradually decreases its growth without entering into ED, and as a result of the fall of temperatures at the beginning of autumn, dies. To understand developmental differences and contrasting responses to environmental cues between both organs, the expression of cell cycle genes, and of genes involved in photoperiodic control of seasonal growth in trees, such as FLOWERING LOCUS T ( FT), APETALA1 ( AP1) and AINTEGUMENTA- like ( AIL) was analyzed at the shoot apex and latent buds of vines during the transition from PD to ED. After shift to SD photoperiod, increased expression of cell cycle genes in the shoot apex suggests a high mitotic activity in this organ which could prevent them from entering into ED. Additionally, the increased expression of VvFT, VvAP1and VvAIL2 in the shoot apex, and the up-regulation of VvFT, VvAP1and cell cycle genes VvCDKA, VvCDKB2, VvCYCA.1, by the dormancy-breaking compound hydrogen cyanamide (HCN), strongly suggests that VvFT plays a key role in regulating transcriptionally cell cycle genes, giving thus, more support to the model for photoperiodic control of seasonal growth in trees. Furthermore, downregulation of VvFT by the SD photoperiod detected in leaves and buds of grapevines highlights the importance of VvFT in the induction of growth cessation and in ED development, probably by regulating the expression of cell cycle genes. [ABSTRACT FROM AUTHOR]

This study investigated some factors that affect Neofusicoccum luteum infection and disease progression in grapevines, on which it causes cankers and die-back. Inoculation of green shoots with each of the conidial suspensions (20 μL of 10-10 conidia/mL) caused 100 % infection, but significant differences in lesion lengths among concentrations ( P < 0.001). Lesion lengths increased with conidial concentrations to a maximum of 41.7 mm, in tissue inoculated with 10/conidial. Lesions then decreased for 10 and 10 conidial/mL (28.6 and 27.8 mm, respectively). The different wetness durations (0-24 h) tested after inoculating trunks of 1-year old vines with conidia did not affect pathogen incidence or lesion lengths, however continued incubation at 95 % RH caused greater pathogen progression (maximum isolation distances from point of inoculation; P < 0.001; 100.6 mm) than at ambient 78 % RH (77.0 mm) within 3 months after inoculation. Inoculation of trunks, canes and green shoots caused different rates of pathogen colonisation ( P < 0.001); by 5 months after N. luteum inoculation mean maximum distances were 39.1, 31.6 and 23.2 mm, respectively. Wound age at the time of inoculation significantly affected ( P < 0.001) infection incidence by N. luteum, which decreased as wounds aged. Conidial inoculum caused 100-0 % incidence over 0-14 days and mycelial inoculum caused 100-40 % infection over 0-30 days. Soil moistures affected lesion development, with 15 and 100 % soil moisture causing greatest dieback and bud death during winter. This study has shown how some features of the natural infection environment can affect infection by Botryosphaeria spp. inoculum and symptom development, which could underpin improvements in vineyard management. [ABSTRACT FROM AUTHOR]

The role of exogenously applied Methyl jasmonate (MeJA) in morphological responses, photochemical efficiency, changes of malondialdehyde content, and the activities of some antioxidant enzymes were investigated in four Iranian grapevine cultivars. MeJA improved morphological traits containing dry and fresh weight, node number, and shoot length. MeJA induced an oxidative stress, as shown by an increase in lipid peroxidation. Activities of catalase, peroxidase, and ascorbate peroxidase were higher in MeJA-treated grapevines than in controls while the relative water content and leaf water loss of grapevine cultivars demonstrated a non-significant difference between the control and varying levels of MeJA. MeJA was positively affected in recovery of the leaf chlorophyll fluorescence (photochemical efficiency) of grapevine cultivars, although the mean proline content of MeJA-treated grapevines indicated a significant decrease when compared with those of the controls. These results suggest that MeJA could act as an intervener in grapevine responses by the enhancing the activity of antioxidants and recovery of photochemical efficiency, leading to enhanced grapevine performance. [ABSTRACT FROM AUTHOR]

Phenolic compounds are components responsible of the sensorial characteristics of red wine. Indeed, they present important properties for human health. In the present work, the effects of combined in field treatments (water-stress and exogenous ABA) on phenolic accumulation were evaluated for berries and wine. The responses were assessed by UV-Vis and CZE. A differential phenolic regulation was observed under the same conditions and good correlations were achieved for grape and wine. ABA appears to regulate the content of each phenols under study depending on plant water-status. Although the effects of water-stress and exogenous ABA were similar in magnitude, our results support evidence suggesting that both affect different metabolic pathways. ABA supply increased catechin and malvidin synthesis for both water statuses while the resveratrol was enhanced only for water-stress. Indeed, ABA reduced the quercetin content for both water statuses. In vitro assays were carried out to estimate the effects of combined treatments (temperature-exogenous ABA) on anthocyanin accumulation in berries and pulp. These tests demonstrated that the effect of ABA was dependent on the hormonal level (207% for 0.5 g L and 307% for 1 g L of ABA). Effect of temperature varied according to the phenological state. In pulps, we detected an increase of anthocyanin after ABA treatments. [ABSTRACT FROM AUTHOR]

The genetic structure of a Plasmopara viticola population was characterized on five single vines, one for each cultivar Regent, Merlot, Isabella, Müller-Thurgau and Solaris, using four neutral specific polymorphic microsatellite markers. Five-hundred and seventy samples were collected at four dates in the period between the 10th of July and the 23rd of August 2006. On average over all five cultivars, 67% of the genotypes present on the single selected vines derived from primary infections and caused 37% of the lesions genotyped. Fifty-three percent of these genotypes occurred only once on the vine throughout the survey period, while 14% were able to asexually reproduce on the selected single vine throughout the survey period, causing 23% of the lesions. Thirty-three percent of the genotypes on the single vine derived from other vines, 28% from vines of other cultivars in the other rows, and 5% from vines of the same cultivar in the same row. New primary infections appear all along the sampling dates. The overwhelmingly quantitative role of primary infections at vineyard scale was known, however here we observed the phenomenon also at the single vine scale and the reduced contribution of secondary lesions to the populations present on more resistant cultivars compared to the susceptible cultivars. As the sampling extended almost to defoliation, the results are judged to be representative of a typical P. viticola epidemic. [ABSTRACT FROM AUTHOR]

Recent community based actions to ensure the sustainability of irrigation and protection of associated ecosystems in the Murrumbidgee Irrigation Area (MIA) of Australia has seen the implementation of a regional Land and Water Management Plan. This aims to improve land and water management within the irrigation area and minimise downstream impacts associated with irrigation. One of the plan objectives is to decrease current salt loads generated from subsurface drainage in perennial horticulture within the area from 20 000 tonnes/year to 17 000 tonnes/year. In order to meet such objectives Controlled Water table Management (CWM) is being investigated as a possible ‘Best Management Practice’, to reduce drainage volumes and salt loads. During 2000–2002 a trial was conducted on a 15 ha subsurface drained vineyard. This compared a traditional unmanaged subsurface drainage system with a controlled drainage system utilizing weirs to maintain water tables and changes in irrigation scheduling to maximize the potential crop use of a shallow water table. Drainage volumes, salt loads and water table elevations throughout the field were monitored to investigate the effects of controlled drainage on drain flows and salt loads. Results from the experiment showed that controlled drainage significantly reduced drainage volumes and salt loads compared to unmanaged systems. However, there were marked increases in soil salinity which will need to be carefully monitored and managed. [ABSTRACT FROM AUTHOR]

The effect of the number of RAPD fragments on the estimation of genetic distances has been studied on 10 genotypes (Vitis vinifera) using 320 primers. A total number of 1683 scorable bands was obtained but only polymorphic bands (932) were considered in this work. The variation of the genetic distances, in relation to an increasing number of bands, was evaluated through a bootstrap sampling procedure. The mean coefficient of variation (CV) of the genetic distances decreased as the number of bands increased. A CV of 10% was obtained with about 100–150 bands while a CV of 5% with a large number of bands (400–500 and over). To reduce the cost and the time of the analyses, primers with different levels of polymorphism were compared. Genetic distance matrices, based on different numbers of bands and primer polymorphism, were highly correlated with the genetic distance matrix of the whole data set when they were determined with a large number of RAPD fragments, either from high or low polymorphic primers. The effect of the number of bands on the estimation of genetic distances was evaluated also through the variation of the pattern of aggregation among genotypes (cluster analysis). Stable clusterings were detected when a large number of polymorphic bands (400 and over) was used. Some rearrangements of the genotypes in the dendrograms was observed as the number of bands decreased; below 100–150 bands the clusterings were completely rearranged. [ABSTRACT FROM AUTHOR]

The nuclear DNA content was analyzed in Vitis species, hybrid cultivars, and genera of the Vitaceae using flow cytometry. Significant variation was found among Vitis species, hybrids, and other genera of the Vitaceae ( Ampelopsis and Parthenocissus). DNA content was estimated to range from 0.98 to 1.05 pg/2C within V. labrusca (ns) and 0.86 to 1.00 pg/2C within V. vinifera (ns). Genotypes from Vitis and Parthenocissus were similar in nuclear DNA content (approximately 1.00 pg/2C) whereas they differed significantly from Ampelopsis (1.39 pg/2C). No correlation between DNA content and the center of origin of genotypes of the Vitaceae was noted. Based on the present study, the Vitis genome size is 475 Mbp, 96% of which is non-coding. Knowledge of DNA content is useful in order to understand the complexity of the Vitis genome and to establish a relationship between the genetic and physical map for map-based cloning. [ABSTRACT FROM AUTHOR]

Studies on the origin and evolution of plasmids may provide valuable insights on the promiscuous nature of DNA. The first examples of the selfish nature of nucleic acids are exemplified by primordial oligoribonucleotides which evolved into primitive replicons. The propagation of these molecules were likely patterned after the current viral RNA ribozymes, which have been recently shown to possess RNA synthesizing and template mediated polymerizing capabilities in the absence of proteins. The parasitic nature of nucleic acids is depicted by satellite nucleic acid molecules associated with viruses. The satellites of adenovirus and tobacco ringspot virus serve as established examples: they contain no open reading frames. Comparative analysis of the replication origins of virions and plasmids show them to be conserved, originating from the simplest autocatalytic replicon to highly complex and evolved plasmids, replicating by a rolling circle mechanism. The eventual association of proteins with nucleic acids provided added efficiency and protective advantages for molecular perpetuation. The promiscuous and selfish nature of plasmids is demonstrated by their ability to genetically engineer their host so that the host cell is best able to cope and survive in hostile environments. Survival of the host ensures survival of the plasmid. Sequestering of genes by plasmids occurs when the environmental conditions negatively affect the host. The sequestering mechanism is fundamental and forms the outreach mechanisms to generate and propagate macromolecules of increasing size when necessary for survival. The level of sophistication of plasmids increases with the addition of new genes such as those that allow the host to occupy a specific environment normally inhospitable to the host cell. The vast range of plasmid types which have obtained genes interchangeably reflect the levels of sophistication achieved by these macromolecules. The Ti plasmid in Agrobacterium tumefaciens and the pSym and accessory plasmids in Rhizobium illustrate the level of complexity attained by replicons. [ABSTRACT FROM AUTHOR]

The biological activity of resveratrol, a stilbenic compound synthesized by grapevines in response to various stresses, was reevaluated against Botrytis cinerea using a novel in vitro system that enabled direct observation of the fungus with an inverted microscope. We determined that 90 μg resveratrol/ml reduced germination of B. cinerea conidia by ca. 50%. Moreover, resveratrol was shown to significantly reduce mycelial growth of B. cinerea at concentrations ranging from 60 to 140 μg/ml. Exposure to resveratrol at concentrations ranging from 60 to 140 μg/ml resulted in cytological changes in B. cinerea, such as production of secondary or tertiary germ tubes by conidia, cytoplasmic granulations, protoplasmic retractation in the hyphal tip cells, and formation of curved germ tubes. These data reinforce the role played by this compound in the B. cinerea–grapevine interaction. [ABSTRACT FROM AUTHOR]