Harvesting and bedding practices in relation to grey mould of strawberries

Relationships of cultural and harvesting practices in strawberries to epidemics of grey mould, caused by Botrytis cinerea, were examined in field plots in 1983 - 84 and 1984 - 85. The strawberries were grown in matted rows or solid beds and harvested by hand or by machine. Foliage cut by the machine was removed by hand-raking. Potential sporulation of B. cinerea on dead strawberry leaves, the principal inoculum source, was estimated by quantifying sporulation on samples of the leaves incubated in humidity chambers. During May, the incidence and density of sporulation, and total spore production per unit area of strawberry bed, usually were lower in plots harvested by machine in the preceding year than in those harvested by hand. Machine harvesting in the preceding year also suppressed incidence of grey mould on the fruits in June. Potential sporulation on dead leaves was usually less in solid beds than in matted rows in 1984 but not in 1985. Bed type usually did not affect incidence of grey mould fruit rot. No relationship was found between dry weights of dead leaves from sampling quadrats and potential sporulation on the leaves. It was postulated that the long-term impact of machine harvesting on grey mould epidemics was related to removal of the majority of the foliage and berries from the plots during harvesting operations.     

Ability of the antagonistic yeast Cryptococcus albidus to control Botrytis cinerea in strawberry

The yeast Cryptococcus albidus, originally isolated from mature strawberry fruits, was tested for antagonistic activity against Botrytis cinerea, the causal agent of grey mould in strawberries. Conidial germination and germ tube growth of conidia of B. cinerea were inhibited by a cell suspension of the antagonist in aqueous strawberry fruit pulp suspension (1%) after 6 and 24 hours of incubation. Application of a cell suspension (1 × 10⁶ cells/ml) on detached strawberry leaf disks incubated at 10°C reduced incidence and conidiophore density of B. cinerea by 86 and 99%, respectively, but effectiveness was reduced at higher temperatures. Treatments with C. albidus during bloom of strawberries reduced incidence of grey mould on ripe strawberry fruits after harvest by 33, 28 and 21% in three years of field trials. The effectiveness of the yeast was increased when formulation substances (alginate, xanthan and cellulose) were added to the cell suspension.     

Biological control of grey mould in strawberry fruits by halophilic bacteria

Aims:  Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti- Botrytis metabolites and volatiles.
Methods and Results:  Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea . Thirty strains (20·2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20°C, from 50% to 91·66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui , B. subtilis , B. pumilus , B. licheniformis , Terribacillus halophilus , Halomonas elongata , Planococcus rifietoensis , Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites.
Conclusions:  Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries.
Significance and Impact of the study:  The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.     

Isolation of Microbial Antagonists for Biocontrol of Grey Mould Disease of Strawberries

A screening programme is described for the assessment of the potential of biocontrol agents to control grey mould of strawberries caused by Botrytis cinerea. Bacteria were isolated from strawberry fruits, leaves and flowers from a commercial field site and screened for antagonism towards B. cinerea using two in vitro and one in vivo screening techniques. From 559 microorganisms isolated, 108 inhibited pathogen growth on agar plates and 27 of these prevented spore germination on Cellophane membranes. The ability of these 27 isolates to inhibit infection of young strawberry leaves by B. cinerea on whole plants under glass was then tested. Seven isolates reduced grey mould development and were subsequently assessed in a field trial. Two isolates, one of Bacillus pumilus and one of Pseudomonas fluorescens, were as effective or more effective than standard dichlofluanid sprays and may therefore be of potential value as antagonists of B. cinerea.     

Antagonistic Properties of Two Bacterial Biocontrol Agents of Grey Mould Disease

Bacillus pumilus NCIMB 13374 and Pseudomonas fluorescens NCIMB 13373 inhibit the growth of Botrytis cinerea , the cause of grey mould of strawberries. Both antagonists increased the pH of the growth medium from pH 6 to pH 8-8.5 and both produced antifungal agents. The compound(s) produced by B. pumilus had a fungicidal effect during conidial germination, whereas the compound(s) produced by P. fluorescens had a fungistatic effect. There was no evidence for the production of inhibitory volatile compounds. Both isolates also showed the ability to inhibit other strawberry fungal pathogens, and have potential for a wider range of biocontrol of plant diseases.     

Seasonal population dynamics of the greenhouse whitefly Trialeurodes vaporariorum (Homoptera: Aleyrodidae) on strawberries in Southern California

The greenhouse whitefly, Trialeurodes vaporariorum (Westwood), has recently become a major insect pest of strawberries in Southern California. The population dynamics of this pest were monitored over 2 yr in six commercial strawberry fields near the coastal communities of Oxnard and Ventura under two crop-production regimes, summer- and fall-planted strawberries. Adult whitefly numbers generally peaked during the February through May period for fall-planted strawberries and during the October through November period for summer-planted strawberries. Population densities varied greatly among fields within each regime and the differences were likely caused by surrounding alternate host crops.     

Novel approach to the microbial decontamination of strawberries: chlorophyllin-based photosensitization

Aims: This study is focused on the possibility to control microbial contamination of strawberries by chlorophyllin (Na‐Chl)‐based photosensitization. Moreover, photosensitization‐induced effects on key quality attributes of treated strawberries was evaluated. Methods and Results: Strawberries were inoculated with Listeria monocytogenes ATC_L3C 7644, soaked in 1 mmol l^?1 Na‐Chl for 5 min and illuminated for 30 min with visible light (λ = 400 nm, energy density 12 mW cm^?2). Results indicated that the decontamination of strawberries using photosensitization was 98% compared to control sample. Naturally occurring yeasts/microfungi and mesophiles were inhibited by 86 and 97%, respectively. The shelf life of treated strawberries was extended by 2 days. The total antioxidant activity of treated strawberries increased by 19%. No impact on the amount of phenols, anthocyanins or surface colour was detected. Conclusions: Photosensitization may be an effective, nonthermal and environmentally friendly microbial decontamination technique which expands the shelf life of strawberries without any negative impact on antioxidant activity, and phenols, anthocyanins or colour formation. Significance and Impact of the Study: Experimental data support the idea that Na‐Chl‐based photosensitization can be a useful tool for the future development of nonthermal food preservation technology.     

Botrytis infection warnings in strawberry: reduced enhanced chemical control

The fungal pathogen Botrytis cinerea is the causal agent of grey mould, the most important fungal fruit rot disease in strawberry in Europe. Currently disease control for grey mould is based on preventive spraying every five to seven days during flowering and harvest. Replacing preventive spraying with applications based on infection warnings can optimize performance and reduce the amount of sprays needed. Success of this approach will depend on the accuracy of the model used to predict disease outbreak. For this reason three infection models (BOTEM, BoWaS, DSS-Italy) were evaluated during the growth seasons of 2003 and 2004. The experiments included June bearing, retarded June bearing and ever bearing strawberries. In all experiments the use of infection models leaded to a reduced number of fungicide applications. However the efficacy of the different models towards the control of B. cinerea also decreased compared to the efficacy obtained with a standard 7 day schedule. Best results were obtained with BOTEM, developed by HRI (Horticultural Research International, East-Malling, UK): 17-60% reduction in fungicide use and an efficacy between 66-93 depending on the growth season, culture practice and the fungicides used. Compared with routine preventive spraying, the Botrytis fruit rot percentage is slightly higher. A higher efficacy with Botrytis infection warnings can only be obtained if infection warnings change from curative to preventive. A retroactive evaluation of a preventive warning system was included. Making use of the 48h weather forecasts supplied by the Royal Meteorological Institute of Belgium (KMI) based on ALADIN for the region of Haspengouw, it was possible to replace 30 up to 100% of the curative application by preventive spraying depending on the experiment and the threshold set for the preventive model.     

Spectral filters for the control of Botrytis cinerea

Experiments performed in vitro examined the sporulation of Botrytis cinerea (grey mould) under different spectral distributions. Eighty‐three isolates, taken from plants of primula (Primula vulgaris) at different locations throughout the UK, were incubated in the dark, with visible light only and visible plus near‐ultraviolet (nUV) light. On average, compared to isolates not exposed to nUV, sporulation was increased 54‐fold following illumination with nUV light. No isolates showed complete insensitivity to near ultraviolet. New polyethylene materials with different optical properties were then tested on two typical isolates. A film which removed nUV up to 405 nm, compared to a film with nUV absorption up to 384 nm, resulted in the lowest production of conidia (by 5‐fold). The former film was used to clad horticultural polyethylene tunnels in which crops of P. vulgaris and strawberry were grown for two seasons and the incidence of B. cinerea assessed throughout the growth of the crops. The incidence of infection on the P. vulgaris and strawberries was reduced by c. 50% and c. 26% respectively with the nUV blocking film compared to a standard film. The results are discussed in terms of the potential of spectral filters as a novel means of grey mould control in greenhouse‐produced crops.     

Detection of human food-borne and zoonotic viruses on irrigated, field-grown strawberries

This study evaluated the presence of pathogenic human and zoonotic viruses on irrigated, field-grown strawberries. Norovirus genogroup I, rotavirus, and swine hepatitis E virus genogroup 3 were detected on strawberries, and irrigation water is suspected as the contamination origin.     

Health Hazard Assessment of Pyridaben Residues in Egyptian Strawberries

Dissipation behavior and hazard assessment of the insecticide/acaricide pyridaben applied to strawberries were investigated under the climatic conditions of Egypt. A validated gas chromatographic method (GC-μECD) was used to determine pyridaben residues when applied at the recommended rate and twice this rate. The average recoveries were in the range between 95.8% and 103% with associated relative standard deviation not exceeding 14.5%. The estimated limit of quantification for pyridaben was 0.005 mg/kg. The field results showed that pyridaben dissipated rapidly in strawberries and had a half-life of approximately 2.3 days. The hazard assessment was evaluated by using the hazard quotient (HQ). The results showed that the HQ value was significantly less than HQ = 1. This result implied that the hazard of pyridaben use in strawberries even at double the recommended dosage was negligible to human. This study could provide guidance for the safe and reasonable use of pyridaben in strawberries and to prevent health problems to consumers; however, further hazard assessment studies are needed to ascertain the hazard of pyridaben residues on strawberries to vulnerable groups, including children, pregnant women, and elderly consumers.     

The involvement of fungi in the breakdown of sulphited strawberries

Between 8000 and 9000 tons of strawberries are used annually for jam manufacture in the UK, c. 65 % of which are stored in sulphite liquor (6 % SO₂+lime, c. pH 3.0). Sporadic cases of disintegration of sulphited strawberries have been observed increasingly in recent years. In laboratory experiments breakdown of whole berries in sulphite liquor was achieved by including berries partly rotted with Mucor mucedo, Rhizopus sexualis or R. stolonifer, 1.5-2.5 % infected material causing complete breakdown of all of the berries. The inclusion of up to 25 % berries infected with Botrytis cinerea caused no softening of the berries. The addition of culture filtrates to whole fruit in sulphite liquor confirmed observations with the above fungi but also showed that pectolytic enzymes from Aureobasidium pullulans and Trichosporon pullulans could cause breakdown. The incidence of spoilage fungi on commercially harvested fruit indicated that M. mucedo and R. sexualis were the main cause of breakdown, but that A. pullulans increased tenfold on fruit stored at 15 °C overnight before sulphiting. Results from commercially harvested fruit (cv. Cambridge Favourite) in 1975 and 1976 showed that: (I) fruit should be sulphited as soon as possible after harvest, since the storage of harvested fruit prior to sulphiting may give a poorer quality product; (2) there is little difference in breakdown of fruit from plants treated with the pre-harvest fungicides, Elvaron, Mildothane, or Daconil, and (3) fruit grown in different areas of the UK shows varying amounts of breakdown. This may be due to differences in the infection level of Phycomycetes and contamination by other pectolytic fungi or inherent differences in the susceptibility of the fruit to enzyme attack.     

Existence commune,sur les fraises,d'ascospores de Byssochlamys nivea pouvant produire de la patuline

Tha auteurs have obtained a strain of Byssochlamys nivea from heat processed strawberries. The mold grown on synthetic media shows antibiotic properties. The metabolite responsible is patulin which has been purified and characterized. Several strains of B. nivea produced this mycotoxin. Patulin seems to be stable in strawberries juice.     

由废弃淡水龙虾壳制备的羧甲基壳聚糖在草莓保鲜过程中的生理作用

利用废弃淡水龙虾壳制备得到的羧甲基壳聚糖应用到草莓的保鲜,为如何有效地解决废弃淡水龙虾壳提供了解决途径.实验结果显示不同浓度的羧甲基壳聚糖处理的草莓腐烂率下降,同时延缓了维生素C水平的下降趋势,其中0.2%浓度的羧甲基壳聚糖的作用效果最为明显.在保鲜过程中,测定草莓果肉中超氧化物歧化酶 (SOD)、过氧化物酶 (POD)、过氧化氢酶(CAT)的活性和脂质过氧化物丙二醛(MDA)的含量的变化,发现经过处理的草莓在保鲜过程中,其SOD,POD,CAT酶活性明显提高,MDA的水平同时显著下降,结果说明羧甲基壳聚糖的保鲜作用可能通过提高抗氧化水平来实现.     

草莓对I-、IO3-的吸收特征及对其品质的影响

提高植物性食品中碘的含量对人体自然补碘具有重要作用。该文通过水培模拟实验, 揭示了草莓(Fragaria ananassa)对I^-和IO₃^-的吸收特征, 在分析不同外源碘浓度下草莓根系以上部分生物量的基础上, 通过对比吸收外源碘前后维生素C、可溶性糖、总酸度和硝酸盐含量的变化, 评价了草莓吸收I^-和IO₃^-对果实品质的影响。研究结果表明, 草莓对碘的吸收量随营养液中I^-和IO₃^-浓度的增加而增加, 相同浓度下草莓吸收的I^-明显多于IO₃^-, 草莓吸收适量的碘可以促进植株生长, 不仅使生物量提高, 而且会增加草莓果实维生素C和可溶性总糖的含量, 从而提高品质。在营养液浓度为0.5-5.0 mg∙kg^-1时, 草莓吸收IO₃^-后会增加果实总酸度和硝酸盐的含量, 降低草莓果实品质。在营养液浓度为0.25-2.5 mg∙kg^-1时, 草莓吸收I^-后会使果实中总酸度和硝酸盐的含量明显降低, 果实的品质有所提高。研究结果为科学培育含碘草莓提供了技术支撑。     

Effects of fungicide spray regimes on incidence of dicarboximide resistance in grey mould (Botrytis cinerea) on strawberry plants

In tunnel experiments, the efficacy of dicarboximide sprays in controlling grey mould of strawberries was greatly decreased by the presence of dicarboximide-resistant forms of Botrytis cinerea. The use of dichlofluanid, as a tank-mix or in an alternating programme, with a dicarboximide fungicide, procymidone, helped to maintain the efficacy of disease control but failed to prevent an increase in the proportion of dicarboximide-resistant forms of the pathogen. Alternative ‘partner’ fungicides (thiram, chlorothalonil) delayed build-up of resistance to dicarboximides. Build-up of resistance was absent or relatively small in unsprayed plots. Application of dichlofluanid alone was always associated with a substantial increase in dicarboximide resistance, although less than in procymidone-treated plots. Monitoring dicarboximide resistance in the tunnels during the winter, when no further sprays were applied, revealed a gradual decline in the proportion of dicarboximide-resistant forms in all previously treated plots. In laboratory studies on inoculated leaf debris, dichlofluanid treatment induced the build-up of dicarboximide-resistant forms of B. cinerea. Leaf-disc tests revealed cross-resistance of dicarboximide-resistant isolates towards dichlofluanid but not towards thiram or chlorothalonil. Dichlofluanid is widely used for control of B. cinerea and the implications of these results for the practical management of dicarboximide resistance in this pathogen are discussed.     

草莓离体无性繁殖的研究——Ⅱ.试管苗移栽和田间表现

本文报道了在普通塑判温室内进行试管苗移栽的试验结果,提出了用离体培养法结合常规栽培技术,及季节特点大规模无性繁殖草莓苗的生产程序。试管苗出现复叶(成年叶)是适合移栽的形态指标;硅石是试管苗良好的移栽基质。简要报道了试管苗的田间表现。     

Seasonal complementary in pollinators of soft-fruit crops

Understanding the relative contributions of wild and managed pollinators, and the functional contributions made by a diverse pollinator community, is essential to the maintenance of yields in the 75% of our crops that benefit from insect pollination. We describe a field study and pollinator exclusion experiments conducted on two soft-fruit crops in a system with both wild and managed pollinators. We test whether fruit quality and quantity is limited by pollination, and whether different pollinating insects respond differently to varying weather conditions. Both strawberries and raspberries produced fewer marketable fruits when insects were excluded, demonstrating dependence on insect pollinators. Raspberries had a short flowering season which coincided with peak abundance of bees, and attracted many bees per flower. In contrast, strawberries had a much longer flowering season and appeared to be much less attractive to pollinators, so that ensuring adequate pollination is likely to be more challenging. The proportion of high-quality strawberries was positively related to pollinator abundance, suggesting that yield was limited by inadequate pollination on some farms. The relative abundance of different pollinator taxa visiting strawberries changed markedly through the season, demonstrating seasonal complementarity. Insect visitors responded differently to changing weather conditions suggesting that diversity can reduce the risk of pollination service shortfalls. For example, flies visited the crop flowers in poor weather and at the end of the flowering season when other pollinators were scarce, and so may provide a unique functional contribution. Understanding how differences between pollinator groups can enhance pollination services to crops strengthens the case for multiple species management. We provide evidence for the link between increased diversity and function in real crop systems, highlighting the risks of replacing all pollinators with managed alternatives.