Single Berries Research Articles

Vitis rotundifolia Genes Introgressed with RUN1 and RPV1: Poor Recombination and Impact on V. vinifera Berry Transcriptome.

Thanks to several Vitis vinifera backcrosses with an initial V. vinifera L. × V. rotundifolia (previously Muscadinia rotundifolia) interspecific cross, the MrRUN1/MrRPV1 locus (resistance to downy and powdery mildews) was introgressed in genotypes phenotypically close to V. vinifera varieties. To check the consequences of introgressing parts of the V. rotundifolia genome on gene expression during fruit development, we conducted a comparative RNA-seq study on single berries from different V. vinifera cultivars and V. vinifera × V. rotundifolia hybrids, including 'G5' and two derivative microvine lines, 'MV102' (resistant) and 'MV32' (susceptible) segregating for the MrRUN1/RPV1 locus. RNA-Seq profiles were analyzed on a comprehensive set of single berries from the end of the herbaceous plateau to the ripe stage. Pair-end reads were aligned both on V. vinifera PN40024.V4 reference genome, V. rotundifolia cv 'Trayshed' and cv 'Carlos', and to the few resistance genes from the original V. rotundifolia cv '52' parent available at NCBI. Weighted Gene Co-expression Network Analysis (WGCNA) led to classifying the differentially expressed genes into 15 modules either preferentially correlated with resistance or berry phenology and composition. Resistance positively correlated transcripts predominantly mapped on the 4-5 Mb distal region of V. rotundifolia chromosome 12 beginning with the MrRUN1/MrRPV1 locus, while the negatively correlated ones mapped on the orthologous V. vinifera region, showing this large extremity of LG12 remained recalcitrant to internal recombination during the successive backcrosses. Some constitutively expressed V. rotundifolia genes were also observed at lower densities outside this region. Genes overexpressed in developing berries from resistant accessions, either introgressed from V. rotundifolia or triggered by these in the vinifera genome, spanned various functional groups, encompassing calcium signal transduction, hormone signaling, transcription factors, plant-pathogen-associated interactions, disease resistance proteins, ROS and phenylpropanoid biosynthesis. This transcriptomic insight provides a foundation for understanding the disease resistance inherent in these hybrid cultivars and suggests a constitutive expression of NIR NBS LRR triggering calcium signaling. Moreover, these results illustrate the magnitude of transcriptomic changes caused by the introgressed V. rotundifolia background in backcrossed hybrids, on a large number of functions largely exceeding the ones constitutively expressed in single resistant gene transformants.

A novel ground truth multispectral image dataset with weight, anthocyanins, and Brix index measures of grape berries tested for its utility in machine learning pipelines.

BackgroundThe combination of computer vision devices such as multispectral cameras coupled with artificial intelligence has provided a major leap forward in image-based analysis of biological processes. Supervised artificial intelligence algorithms require large ground truth image datasets for model training, which allows to validate or refute research hypotheses and to carry out comparisons between models. However, public datasets of images are scarce and ground truth images are surprisingly few considering the numbers required for training algorithms.ResultsWe created a dataset of 1,283 multidimensional arrays, using berries from five different grape varieties. Each array has 37 images of wavelengths between 488.38 and 952.76 nm obtained from single berries. Coupled to each multispectral image, we added a dataset with measurements including, weight, anthocyanin content, and Brix index for each independent grape. Thus, the images have paired measures, creating a ground truth dataset. We tested the dataset with 2 neural network algorithms: multilayer perceptron (MLP) and 3-dimensional convolutional neural network (3D-CNN). A perfect (100% accuracy) classification model was fit with either the MLP or 3D-CNN algorithms.ConclusionsThis is the first public dataset of grape ground truth multispectral images. Associated with each multispectral image, there are measures of the weight, anthocyanins, and Brix index. The dataset should be useful to develop deep learning algorithms for classification, dimensionality reduction, regression, and prediction analysis.

Transcripts switched off at the stop of phloem unloading highlight the energy efficiency of sugar import in the ripening V. vinifera fruit

Transcriptomic changes at the cessation of sugar accumulation in the pericarp of Vitis vinifera were addressed on single berries re-synchronised according to their individual growth patterns. The net rates of water, sugars and K+ accumulation inferred from individual growth and solute concentration confirmed that these inflows stopped simultaneously in the ripe berry, while the small amount of malic acid remaining at this stage was still being oxidised at low rate. Re-synchronised individual berries displayed negligible variations in gene expression among triplicates. RNA-seq studies revealed sharp reprogramming of cell-wall enzymes and structural proteins at the stop of phloem unloading, associated with an 80% repression of multiple sugar transporters and aquaporins on the plasma or tonoplast membranes, with the noticeable exception of H+/sugar symporters, which were rather weakly and constitutively expressed. This was verified in three genotypes placed in contrasted thermo-hydric conditions. The prevalence of SWEET suggests that electrogenic transporters would play a minor role on the plasma membranes of SE/CC complex and the one of the flesh, while sucrose/H+ exchangers dominate on its tonoplast. Cis-regulatory elements present in their promoters allowed to sort these transporters in different groups, also including specific TIPs and PIPs paralogs, and cohorts of cell wall-related genes. Together with simple thermodynamic considerations, these results lead to propose that H+/sugar exchangers at the tonoplast, associated with a considerably acidic vacuolar pH, may exhaust cytosolic sugars in the flesh and alleviate the need for supplementary energisation of sugar transport at the plasma membrane.

Counting of grapevine berries in images via semantic segmentation using convolutional neural networks

The extraction of phenotypic traits is often very time and labour intensive. Especially the investigation in viticulture is restricted to an on-site analysis due to the perennial nature of grapevine. Traditionally skilled experts examine small samples and extrapolate the results to a whole plot. Thereby different grapevine varieties and training systems, e.g. vertical shoot positioning (VSP) and semi minimal pruned hedges (SMPH) pose different challenges.In this paper we present an objective framework based on automatic image analysis which works on two different training systems. The images are collected semi automatic by a camera system which is installed in a modified grape harvester. The system produces overlapping images from the sides of the plants. Our framework uses a convolutional neural network to detect single berries in images by performing a semantic segmentation. Each berry is then counted with a connected component algorithm. We compare our results with the Mask-RCNN, a state-of-the-art network for instance segmentation and with a regression approach for counting. The experiments presented in this paper show that we are able to detect green berries in images despite of different training systems. We achieve an accuracy for the berry detection of 94.0% in the VSP and 85.6% in the SMPH.

FT-NIR Analysis of Intact Table Grape Berries to Understand Consumer Preference Driving Factors.

Fourier-transform near infrared spectroscopy (FT-NIR) is a technique used in the compositional and sensory analysis of foodstuffs. In this work, we have measured the main maturity parameters for grape (sugars and acids) using hundreds of intact berry samples to build models for the prediction of these parameters from berries of two very different varieties: “Victoria” and “Autumn Royal”. Together with the chemical composition in terms of sugar and acidic content, we have carried out a sensory analysis on single berries. Employing the models built for sugars and acids it was possible to learn the sweetness and acidity of each berry before the destructive sensory analysis. The direct correlation of sensory data with FT-NIR spectra is difficult; therefore, spectral data were exported from the spectrometer built-in software and analyzed with R software using a statistical analysis technique (Spearman correlation) which allowed the correlation of berry appreciation data with specific wavelengths that were then related to sugar and acidic content. In this article, we show how it is possible to carry out the analysis of single berries to obtain data on chemical composition parameters and consumer appreciation with a fast, simple, and non-destructive technique with a clear advantage for producers and consumers.

The kinetics of grape ripening revisited through berry density sorting

Aim: In this study, ripening and heterogeneity in density-sorted berries were investigated, with the aim of more clearly understanding the kinetics of water uptake and sugar, acid and anthocyanin accumulation in the fruit of a new, disease-resistant hybrid.Methods and results: The 3184-1-9N hybrid, grown in a semi-arid climate in the South of France, was used. Its genotype is the result of several backcrosses of a Muscadinia ´ Vitis vinifera F1 hybrid with several V. vinifera varieties. From the end of the green plateau to the over-ripening stage, single berries were sampled weekly and sorted by density, to monitor the advancement of ripening and the heterogeneity of grapevine fruit development at population level. Fruit firmness, density, fresh weight, primary metabolite content (sugars and organic acids), secondary metabolite content (anthocyanins), potassium content and pH were measured in berries from each density class. The data showed that softening and hexose accumulation occurred before fruit pigmentation. Based on malic acid and anthocyanin concentration relative to sugar concentration in density-sorted grapes, malic acid breakdown or dilution was promoted and anthocyanin accumulation reduced in late- or slow-ripening berries. In the different population structures in two experimental plots, berries with similar sugar concentration showed considerable heterogeneity in terms of volume and anthocyanin content, whereas pH, potassium content and acid content showed much more homogeneous kinetics.Conclusions: During ripening, analysis of density-sorted berries provides useful information about sugar concentration heterogeneity and its relation with organic acid and anthocyanin content. The stage at which grapes can be considered ripe may be precisely determined through periodic determination of mean berry volume or weight, to detect the cessation of phloem unloading and the onset of berry shrivelling. However, ripening and shrivelling berries generally coexist in the harvested population. Asynchronous berry development and berry weight heterogeneity greatly complicate determination of the timing of developmental events that are regulated at the single-berry level. Therefore, analysis of individual berries would seem to be an indispensable component of investigations of berry growth and development.Significance and impact of the study: Plotting water uptake and solute accumulation relative to sugar accumulation (as an internal clock) provides an original way to display grapevine fruit development data. Analysis of density-sorted berries has identified the relatively invariant fruit features, such as the minimum concentration of tartaric acid, the stability of potassium accumulation and pH, and conversely, the huge variations in berry size.

Container Production of Southern Highbush Blueberries Using High Tunnels

Blueberry production in Mississippi (MS) is mainly rabbiteye blueberries (Vaccinium virgatum Ait.), which ripen in late May to June. Growing early-ripening southern highbush blueberries (SHBs) (Vaccinium corymbosum L.) presents an opportunity for early fruit production and increased market price for locally produced blueberries, yet faces the challenge of spring frost damage. One-year-old liners of 10 SHB cultivars were transplanted into 15-gallon plastic containers and placed in a high tunnel in Apr. 2015. Blueberry plants were fertilized with either a conventional or an organic fertilizer at comparable rates. Plants were evaluated for berry yield, timing of first berry harvest and peak harvest, single berry weight, and soluble solid content during the 2016 and 2017 growing seasons. The high tunnel increased monthly maximum temperature by 3.2 to 10.4 °C, monthly average temperature by 0.7 to 4.2 °C, and minimum monthly temperature for up to 3.0 °C compared with outdoor environment. Photosynthetically active radiation (PAR) at noon in the high tunnel ranged from 477 to 1411 µmol·m−2·s−1 and relative humidity ranged from 54.6% to 81.7% from Jan. 2016 to June 2017. SHBs in the high tunnel produced first berry harvest during the first week of April in both growing seasons. Total berry yield per plant ranged from 921 g to 2136 g in 2016 and from 1222 g to 2480 g in 2017. Compared with the organic fertilizer, conventional fertilizer increased berry yield in April and May, and total berry yield in 2016, but resulted in similar yield in 2017. Eight cultivars (Emerald, Farthing, Gupton, Meadowlark, Pearl, Rebel, Star, and Sweetcrisp) produced single berries that averaged more than 2 g per berry in 2016, compared with two cultivars (Gupton and Pearl) in 2017. Smaller berry size may have resulted from the generally increasing yield from 2016 to 2017. ‘Sweetcrisp’ produced berries with higher soluble solid content, 14.2% and 14.1% in 2016 and 2017, than the other nine cultivars. Container production of SHB cultivars in a high tunnel produced total berry yield equivalent to 6458 kg/ha in 2016 to 7500 kg/ha in 2017, advanced blueberry production by 4 to 5 weeks, and therefore may serve as a potential production system for early fruiting blueberries in Mississippi.

Yeast-like fungi and yeasts in withered grape carposphere: Characterization of Aureobasidium pullulans population and species diversity

Yeast-like fungi and yeasts residing on carposphere of withered grapes for Italian passito wine production have been scarcely investigated. In the present study, isolates from single berries, both sound and damaged, of Nosiola, Corvina and Garganega varieties were analyzed at the end of the withering process. Great variation of cell concentration among single berries was observed. In sound berries, yeast-like fungi were significantly more frequent than yeasts. Species identification of isolates was carried out by BLAST comparative analysis on gene databases and phylogenetic approach. All yeast-like fungi isolates belonged to Aureobasidium pullulans. They displayed different culture and physiological characteristics and inhibitory capacity against phytopathogenic fungi. Moreover, PCR profile analysis revealed high genotypic similarity among these strains. A total of 35 species were recognized among yeast isolates. Ascomycetes prevailed over basidiomycetes. To the best of our knowledge, Naganishia onofrii and Rhodosporidiobolus odoratus were identified for the first time among yeasts isolated from grapes, must or wine. Hanseniaspora uvarum and Starmerella bacillaris were the most frequent species. Most species were found only in one grape variety (nine in Nosiola, 10 in Corvina and five in Garganega). The sanitary state of withered grapes could have an important impact on the structure of these epiphytic populations.

Berry skin resistance explains oviposition preferences of Drosophila suzukii at the level of grape cultivars and single berries

Drosophila suzukii (Matsumura) is an invasive species, which is able to attack intact ripening fruit and has become a serious pest in the Americas and Europe. However, susceptibility toward D. suzukii varies strongly within and between grapevine cultivars. The aim of our study was to differentiate between berry parameters influencing oviposition of D. suzukii in grapevine with two complementary approaches. We investigated the influence of berry skin resistance, total soluble solids (a sugar related parameter), acidity and volatile acidity on grape susceptibility; in the first approach at the cultivar level in a field survey, and in the second approach at the single berry level in a laboratory choice experiment. Both approaches revealed that berry skin resistance explained oviposition decidedly better than chemical composition of the berries did: Soft skinned cultivars and berries received significantly more eggs than hard skinned cultivars and berries. These findings suggest a major role of berry skin resistance in the susceptibility of grapevine toward D. suzukii. The cultivar approach identified the cultivars Dornfelder, Trollinger (= Vernatsch, Schiava), Portugieser, Roter Elbling and Cabernet Dorsa to be susceptible, whereas Dakapo, Lemberger (= Blauer Limberger) and Riesling showed no oviposition by D. suzukii. Nevertheless, parameters like previous damage, climate, environment and plant protection may have an additional impact.

A pattern recognition strategy for visual grape bunch detection in vineyards

Automating grapevine growth monitoring, spraying, leaf thinning and harvesting tasks, as well as improving yield estimation and plant phenotyping, requires reliable methods for detecting grape bunches across different vineyard environmental and plant variety conditions, in which illumination, occlusions, colors and contrast are the main challenges to computer vision techniques. This work presents a method that employs visible spectrum cameras for robust grape berries recognition and grape bunch detection that does not require artificial illumination nor is limited to red or purple grape varieties. The proposed approach relies on shape and texture information together with a strategy to separate regions of clustered pixels into grape bunches. The approach employs histograms of oriented gradients (HOG) as shape descriptor and local binary patterns (LBP) to obtain texture information. A review of the existing methods and comparative analysis of different feature vectors (DAISY, DSIFT, HOG, LBP) and support vector classifiers (SVM-RBF, SVDD) is also presented. Datasets from four countries containing 163 images of different grapevine varieties acquired under different vineyard illumination and occlusion levels were employed to assess the approach. Grapes bunches are detected with an average precision of 88.61% and average recall of 80.34%. Single berries are detected with precision rates above 99% and recall rates between 84.0% and 92.5% on average. The proposed approach should facilitate the estimation of yield, crop thinning measurements and the computation of leaf removal indicators, as well as the implementation guidance strategies for precise robotic harvesters.

Filamentous fungi associated with natural infection of noble rot on withered grapes

The effects of noble rot infection of grapes on the characteristics of different types of wine, including Italian passito wine, are well known. Nevertheless, there is still little information on filamentous fungi associated with noble-rotten grapes. In this study, withered Garganega grapes for passito wine production, naturally infected by noble rot, were analyzed and compared to sound grapes. Skin morphology and fungal population on berry surfaces were analyzed. Scanning electron microscopy analysis revealed microcracks, germination conidia and branched hyphae on noble-rotten berries. Penicillium, Aureobasidium and Cladosporium were the most frequent genera present. Analysis of single berries displayed higher heterogeneity of epiphytic fungi in those infected by noble-rot than in sound berries. Penicillium adametzoides, Cladosporium cladospoirioides and Coniochaeta polymorpha were recovered. These, to the best of our knowledge, had never been previously isolated from withered grapes and, for C. polymorpha, from grapevine. This study provided novel data on noble rot mycobiota and suggests that fungi that co-habit with B. cinerea could have an important role on grape and wine quality.

Effects of exogenous 24‐epibrassinolide to control grey mould and maintain postharvest quality of table grapes

SummaryThe potential of various concentrations of 24‐epibrassinolide (EBR) treatments on the control of grey mould in artificial Botrytis cinerea inoculation test and on the maintenance of postharvest quality of table grapes without inoculation in cold storage were researched. In the cold storage, clusters of grapes with exogenous EBR application (EBR1, 0.1 mg L−1 EBR; EBR2, 0.4 mg L−1 EBR; EBR3, 0.8 mg L−1 EBR) were stored at 0 ± 1 °C. Fruits’ quality attributes including berry firmness, weight loss, berry drop, decay berry percentages, total sugar and titratable acidity were measured at 15, 30 and 60 days. The results showed that EBR treatments exhibited a higher berry firmness and a lower percentage of weight loss, berry drop and decay berry. In the artificial inoculation trial, single berries were immersed in EBR1, EBR2 and EBR3, then inoculated by spraying with a B. cinerea spore suspension and stored at 25 ± 2 °C and 95% relative humidity. Disease severity (DS), lipid peroxidation and defence‐related enzymes of these berries were analysed every 2 days. EBR‐treated berries resulted in an increase in activities of defence‐related enzymes including superoxide dismutase, peroxidase, catalase and phenylalanine ammonia‐lyase compared with control berries inoculated by B. cinerea. Simultaneously, significant decreases in DS and production of superoxide anion radical and malondialdehyde were observed. These results suggested that exogenous application of EBR could play a protective role in controlling the grey mould of postharvest grapes and maintaining the postharvest quality during cold storage.

Microcalorimetric monitoring of grape withering

This work aimed at monitoring the metabolic activity of grapes during withering by microcalorimetry. Samples of Corvina grapes, a cultivar used in the production of Amarone wine, were dehydrated for about 120 days at an industrial scale plants (fruttaia). Single berries, sampled in the course of the withering process, were closed in ampoules and maintained at constant temperature. As biochemical events (i.e. berry respiration, microbial growth, etc.) are always accompanied by the production of heat (q), the heat-flow (dq/dt) emitted by berries enclosed in the ampoules was used to monitor their metabolic activity during withering, i.e. respiration. For each sampling time, the heat rate production of the berries at 298K was monitored till a steady state signal was achieved (within 60h). Such heat flow value was used as marker during the entire withering process (120 days). Its trend allowed to characterize the changes in the metabolic activity of the grape berries along the withering process. To understand the origin of such changes, the emission of volatile organic compounds (VOCs) were also measured by proton transfer mass spectrometry (PTR-MS). The use of microcalorimetry associated with the analysis of specific VOCs fragments offered a valuable information to describe the withering process.

Screening of anthocyanins in single red grapes using a non-destructive method based on the near infrared hyperspectral technology and chemometrics.

Anthocyanins are the main compounds responsible for the colour of red wines and therefore it may be important to evaluate the content of the aforesaid secondary metabolites during grape ripening due to the crucial importance to determine wine colour. Nowadays, there is a growing demand of rapid and non-destructive analytical tools for analysing grapes, such as the emerging hyperspectral analysis. The hyperspectral images of intact grapes (Vitis vinifera L. cv. Tempranillo, Graciano, Garnacha and Mazuelo red grape from vineyards located in the D.O.Ca. Rioja at two different developmental stages) were recorded using a near infrared hyperspectral imaging device (900-1700 nm). Reference values of anthocyanins were obtained by HPLC-DAD. Calibrations were performed by modified partial least squares regression and present a good potential (coefficient of determination of 0.72 and standard error of cross-validation values of 0.78 and 0.70 mg per grape for total and non-acylated anthocyanins respectively). The procedure reported here presents a good potential for a fast and reasonably inexpensive screening of these compounds in intact single berries. Moreover, the heterogeneity of anthocyanins within the same ripeness stage could be evaluated using this non-detructive tool.

Optimization of sample preparation for determination of antioxidant parameters from one grape berry

Berry quality is an important issue in wineprocessing, however evaluating characteristics in a single berry level is very complex. The Phenolic compound analysis is more challenging because of the limited amount of material and a mixture of skin, pulp and seed. No clear protocol exists for evaluating these compounds from single berries. The aim of our investigation was to develop such a protocol. Single whole grape berries samples were homogenized in 20 replicates by 5 different methods. The most effective method was when berry was placed in a mortar and was crushed with a pestle under liquid nitrogen until seeds were clearly visible. Seeds were then taken from the mortar and crushed between two stainless steel plates with a hammer, and returned to the mortar without residues. Homogenization continued until the sample had a powdery appearance. The homogenized samples were taken for further analysis such as total polyphenols, total anthocyanin contents and total antioxidant capacity. Our results demonstrate that single berries could be processed and that the homogenates were suitable for taking chemically uniform subsamples.

Effect of Chitosan Dissolved in Different Acids on Its Ability to Control Postharvest Gray Mold of Table Grape

Chitosan is a natural biopolymer that must be dissolved in an acid solution to activate its antimicrobial and eliciting properties. Among 15 acids tested, chitosan dissolved in 1% solutions of acetic, L-ascorbic, formic, L-glutamic, hydrochloric, lactic, maleic, malic, phosphorous, and succinic acid. To control gray mold, table grape berries were immersed for 10 s in these chitosan solutions that had been adjusted to pH 5.6. The reduction in decay among single berries of several cultivars (Thompson Seedless, Autumn Seedless, and grape selection B36-55) inoculated with Botrytis cinerea at 1 x 10(5) conidia/ml before or after immersion in chitosan acetate or formate, followed by storage at 15 degrees C for 10 days, was approximately 70%. The acids alone at pH 5.6 did not control gray mold. Decay among clusters of two cultivars (Thompson Seedless and Crimson Seedless) inoculated before treatment was reduced approximately 60% after immersion in chitosan lactate or chitosan acetate followed by storage for 60 days at 0.5 degrees C. The viscosity of solutions was 1.9 centipoises (cp) (ascorbate) to 306.4 cp (maleicate) and the thickness of chitosan coating on berries was 4.4 microm (acetate) to 15.4 microm (ascorbate), neither of which was correlated with solution effectiveness. Chitosan acetate was the most effective treatment which effectively reduced gray mold at cold and ambient storage temperatures, decreased CO2 and O2 exchange, and did not injure the grape berries.

DEVELOPING INTEGRATED FRUITWORM CONTROL STRATEGIES FOR BLUEBERRY IN PREPARATION FOR PESTICIDE RESTRICTIONS

DEVELOPING INTEGRATED FRUITWORM CONTROL STRATEGIES FOR BLUEBERRY IN PREPARATION FOR PESTICIDE RESTRICTIONS

Assessment of chitosan for inhibition of Colletotrichum sp. on tomatoes and grapes

The objective of this study was to evaluate the antifungal properties of chitosan and to assess its role in the protection of tomato and grape plants against Colletotrichum sp. isolated from infected tissues of Dracaena sanderiana. The isolate was tested in vitro using PDA amended with five concentrations of chitosan (0, 1, 1.5, 2, 2.5%). Chitosan significantly ( P < 0.05) inhibited the radial growth of this fungus, with a marked effect at the three highest concentrations, after 7 d incubation. The effective concentration that reduced the radial growth to 50% (EC 50) was 2.28%. Tomato fruits and single berries treated with aqueous solutions of 1.0 and 2.5% (w/v) chitosan were artificially inoculated with Colletotrichum sp. and incubated at 4 and 24 °C. Lesion diameters were recorded 7 and 10 d after inoculation. After 10 d at 24 °C, chitosan significantly ( P < 0.05) reduced the lesion size of tomato fruits treated with 1.0 and 2.5%. Lesion diameter on pre-treated berries was also significantly reduced at 24 °C. However, no differences were observed between the chitosan concentrations and the corresponding controls at 4 °C; no lesions developed on berries at either 7 or 10 d after inoculation and although lesion size on tomato fruits was smaller for all treatments when stored at 4 °C, there were no treatment differences.

Combination of chitosan and ethanol to control postharvest gray mold of table grapes

Gray mold, caused by Botrytis cinerea, is the most important postharvest disease of table grapes. Chitosan, a natural biopolymer with antifungal and eliciting properties, and ethanol, a common food additive with antifungal properties, are both able to reduce postharvest decay of table grapes. The effectiveness of reduced doses of chitosan and ethanol, applied alone or in combination, to control gray mold of table grapes was evaluated. Artificially inoculated single berries or clusters were immersed in chitosan (0.1 and 0.5%), ethanol (10 and 20%), or their mixture. The combination of 0.5% chitosan with 10 or 20% ethanol improved decay control with respect to their single treatments, while combinations of 0.1% chitosan with 10 or 20% ethanol did not improve gray mold control compared to the treatments applied alone. On single berries stored 7 days at 15 ± 1 °C, the highest levels of decay control were observed on grapes treated with the combination of 0.5% chitosan and 10 or 20% ethanol (reductions of 94 and 97% on cv Autumn Seedless and 69 and 73% on Thompson Seedless, respectively, compared to controls). On small clusters stored 60 days at 0.5 ± 1 °C, the highest percent reduction was observed on grapes treated with the combination of 0.5% chitosan and 10 or 20% ethanol (reductions of 47 and 60% in Thompson Seedless, and 70 and 94% in Autumn Seedless, respectively, compared to controls). The tests with small clusters were carried out to simulate commercial prolonged cold storage of table grapes. The combination of reduced doses of chitosan and ethanol improved the control of gray mold of table grapes compared to their application alone, and the effect was at least additive and at times synergistic.

Influence of Temperature, Inoculation Interval, and Dosage on Biofumigation with Muscodor albus to Control Postharvest Gray Mold on Grapes.

Control of postharvest gray mold, caused by Botrytis cinerea, on Thompson Seedless grape by biofumigation with a rye grain formulation of Muscodor albus, a fungus that produces volatiles lethal to many microorganisms, was evaluated. The influences of temperature, biofumigant dosage, and interval between inoculation and treatment on disease incidence and severity on detached single berries were assessed. When biofumigation began within 24 h after inoculation, higher M. albus dosages (≥50 g of the M. albus grain formulation per kilogram of grapes at 20°C or 100 g/kg at 5°C) stopped infections and control persisted after M. albus removal. Biofumigation was more effective at 20 than 5°C. Among inoculated clusters inside clamshell boxes incubated for 7 days at 15°C, gray mold incidence was reduced from 20.2% among untreated grape fruit to less than 1%, when ≥5 g of the formulation per kilogram of grapes was added. Among grape berries commercially packaged in ventilated polyethylene cluster bags incubated for 7 days at 15°C, gray mold incidence was 40.5% among untreated fruit and 11.1 or 6.7% when the formulation at 5 or 20 g/kg, respectively, had been added. In the same packaging, among grape berries incubated for 28 days at 0.5°C, gray mold incidence was 42.8% among untreated fruit and 4.8 or 4.0% when the formulation at 5 or 10 g/kg, respectively, had been added. Lower dosages (≤20 g/kg) suppressed disease development while M. albus was present; however, after their removal, B. cinerea resumed growth and gray mold incidence increased. Placement of M. albus inside grape packages significantly controlled gray mold and may be a feasible approach to manage postharvest decay of table grape.