Biocontrol of Postharvest Grey Mould on Tomato by Yeasts

The fungal pathogen Botrytis cinerea causes severe rots on tomato fruit during storage and shelf life. Biological control of postharvest diseases of fruit may be an effective alternative to chemical control. Yeasts are particularly suitable for postharvest use, proving to be highly effective in reducing the incidence of fungal pathogens. Yeast fungi isolated from the surface of solanaceous plants were evaluated for their activity in reducing the postharvest decay of tomato caused by B. cinerea. Of 300 isolates, 14 strains of Rhodotorula rubra and Candida pelliculosa were found to be strongly antagonistic to the pathogen in vitro and were selected for further storage experiment. The antagonists were evaluated for their effect on the biological control of postharvest grey mould. Artificially wounded fruits were treated by means of a novel technique: small sterile discs of filter paper imbibed separately in suspensions of each yeast and the pathogen were superposed onto each wound. After 1‐week, 11 isolates were significantly effective in reducing the diameter of lesions by more than 60% compared to the control treated with B. cinerea alone. Total protection was obtained with the strain 231 of R. rubra on fruits challenged with pathogen spores. To our knowledge, R. rubra and C. pelliculosa have not been described as biocontrol agents against grey mould caused by B. cinerea. Our data demonstrate that the application of antagonistic yeasts represents a promising and environmentally friendly alternative to fungicide treatments to control postharvest grey mould of tomato.     

Grey mould of strawberry,a devastating disease caused by the ubiquitous necrotrophic fungal pathogen Botrytis cinerea

The fungal pathogen Botrytis cinerea causes grey mould, a commercially damaging disease of strawberry. This pathogen affects fruit in the field, storage, transport and market. The presence of grey mould is the most common reason for fruit rejection by growers, shippers and consumers, leading to significant economic losses. Here, we review the biology and epidemiology of the pathogen, mechanisms of infection and the genetics of host plant resistance. The development of grey mould is affected by environmental and genetic factors; however, little is known about how B. cinerea and strawberry interact at the molecular level. Despite intensive efforts, breeding strawberry for resistance to grey mould has not been successful, and the mechanisms underlying tolerance to B. cinerea are poorly understood and under-investigated. Current control strategies against grey mould include pre- and postharvest fungicides, yet they are generally ineffective and expensive. In this review, we examine available research on horticultural management, chemical and biological control of the pathogen in the field and postharvest storage, and discuss their relevance for integrative disease management. Additionally, we identify and propose approaches for increasing resistance to B. cinerea in strawberry by tapping into natural genetic variation and manipulating host factors via genetic engineering and genome editing.     

Isolation of bioactive antibiotic peptides from Bacillus brevis and Bacillus polymyxa against Botrytis grey mould in strawberry

Abstract

Grey mould caused by Botrytis cinerea is a devastating disease that results in extensive yield losses to strawberry. Bacillus brevis (Brevibacillus brevis) and Bacillus polymyxa (Paenibacillus polymyxa), which showed strong antifungal activity against B. cinerea, were isolated from the phyllosphere of strawberry plants. The advantage of using these bacteria is that the biochemistry and physiology of production of antibiotic peptides antimicrobial substances is well documented. A study was conducted to assess the activity of both Bacilli and their antibiotic peptides produced against B. cinerea in strawberry plants in vitro and in vivo. In vitro bioassay, both Bacilli have strongly inhibited pathogen germination, growth and extra-cellular enzyme production. Bacillus brevis was generally the most effective in reducing Botrytis growth. Gramicidin S and polymyxin B peptide antibiotics were extracted from culture filtrate of B. brevis and B. polymyxa, respectively, purified by silica thin chromatography and identified by high performance liquid chromatography. Germination, growth rate and production of extra-cellular enzymes were more sensitive to both antibiotics. Gramicidin S was the most active against B. cinerea with a minimal inhibitory concentration of 15 μmol/l. Polymyxin B also showed activity against B. cinerea at 25 μmol/l. Under controlled conditions (18 – 22°C, 90% relative humidity and 12 h photoperiod), strawberry plants were sprayed with pathogens (10⁵ spores/ml), antagonists (from 10⁵ to 10⁸ cells/ml) and antibiotic peptides (0 – 30 μmol/l) for reducing grey mould. Disease incidence was decreased in the presence of B. brevis. Both antibiotic peptides inhibited Botrytis growth that was observed by scanning electron microscopy. The plant leaves adsorbed significant amounts of antibiotics which reached from 46.1 to 67.5% of the original solution. Under natural field conditions, these biocontrol and antibiotic peptides at different concentrations were evaluated in 2003/2004 and 2004/2005 seasons against Botrytis grey mould. Treating plants with B. brevis exhibited a significant high activity against the development of Botrytis disease on strawberry. Gramicidin S showed a strong potential in reducing disease incidence, followed by polymyxin B, and acted as a fungicide to the pathogen growth. Inhibition of B. cinerea by both Bacilli was similar to equivalent levels of their antibiotics produced. In addition, these treatments significantly reduced the development of Botrytis and increased fruit yield. It can be suggested that B. brevis and B. polymyxa may be considered as potential biocontrol agents against Botrytis grey mould on strawberry based on the production of antifungal peptides. Therefore, gramicidin S and polymyxin B products are considered as biocontrol agents and may play a significant role in the future for practical applications in strawberry management systems.     

Host-induced gene silencing of BcTOR in Botrytis cinerea enhances plant resistance to grey mould

Botrytis cinerea is the causal agent of grey mould for more than 200 plant species, including economically important vegetables, fruits and crops, which leads to economic losses worldwide. Target of rapamycin (TOR) acts a master regulator to control cell growth and proliferation by integrating nutrient, energy and growth factors in eukaryotic species, but little is known about whether TOR can function as a practicable target in the control of plant fungal pathogens. Here, we characterize TOR signalling of B. cinerea in the regulation of growth and pathogenicity as well as its potential value in genetic engineering for crop protection by bioinformatics analysis, pharmacological assays, biochemistry and genetics approaches. The results show that conserved TOR signalling occurs, and a functional FK506-binding protein 12 kD (FKBP12) mediates the interaction between rapamycin and B. cinerea TOR (BcTOR). RNA sequencing (RNA-Seq) analysis revealed that BcTOR displayed conserved functions, particularly in controlling growth and metabolism. Furthermore, pathogenicity assay showed that BcTOR inhibition efficiently reduces the infection of B. cinerea in plant leaves of Arabidopsis and potato or tomato fruits. Additionally, transgenic plants expressing double-stranded RNA of BcTOR through the host-induced gene silencing method could produce abundant small RNAs targeting BcTOR, and significantly block the occurrence of grey mould in potato and tomato. Taken together, our results suggest that BcTOR is an efficient target for genetic engineering in control of grey mould, and also a potential and promising target applied in the biocontrol of plant fungal pathogens.     

Biocontrol of aerial plant diseases in agriculture and horticulture: current approaches and future prospects

Until recently, the majority of research on the biological control of aerial plant diseases was focused on control of bacterial pathogens. Such research led to the commercialization of the biocontrol agent Pseudomonas fluorescens A506, as BlightBan A506™, for control of fire blight of pear. In contrast, chemical fungicides typically have provided adequate control of most foliar fungal pathogens. However, fungicide resistance problems, concerns regarding pesticide residues and revocation of registration of certain widely used fungicides have led to increased activity in the development of biocontrol agents of foliar fungal pathogens. Much of this activity has centered around the use of Trichoderma spp and Gliocladium spp to control Botrytis cinerea on grape and strawberry. The biocontrol agent Trichoderma harzianum T39 is commercially available in Israel, as Trichodex ™, for control of grey mold in grapes and may soon be registered for use in the US. Also targeted primarily against a foliar disease of grapes, in this case powdery mildew caused by Uncinula necator, is the biocontrol agent Ampelomyces quisqualis AQ10, marketed as AQ^{10  TM} biofungicide. Another promising development in the area of foliar disease control, though one which is not yet commercialized, is the use of rhizobacteria as seed treatments to induce systemic resistance in the host plant, a strategy which can protect the plant against a range of bacterial and fungal pathogens. Received 06 February 1997/ Accepted in revised form 05 June 1997     

Biological control of Botrytis cinerea on tomato using naturally occurring fungal antagonists

Abstract

In order to evaluate the potential of naturally occurring filamentous fungi having potential as biocontrol agents effective against grey mould and post-harvest fruit rot caused by Botrytis cinerea on tomato, fungal saprophytes were isolated. They were obtained from leaves, fruits and flowers belonging to different species of cultivated and spontaneous Solanaceous plants collected at the horticultural area of La Plata, Argentina. Of 300 isolates screened for inhibition of B. cinerea using the dual culture technique on agar plate, 12 strains inhibited strongly mycelial growth of the pathogen. Among the antagonists one isolate of Epicoccun nigrum (126), four of Trichoderma harzianum (110, 118, 248 and 252) and four isolates of Fusarium spp. decreased the spore germination of B. cinerea between 30 and 70%. These isolates were probed on tomato fruits to evaluate their biocontrol activity against post-harvest grey mould. In growth chamber tests, E. nigrum (27), F. equiseti (22, 105) and T. harzianum (118, 252) reduced the diameter of fruit lesions by 50 – 90% and were selected for further biocontrol assays of tomato plants in the greenhouse. Although there were not significant differences between the treatments and the control, F. equiseti (105), E. nigrum (27) and T. harzianum (118) reduced by 20, 22 and 22 respectively the disease on whole plants. The targeted application of isolates of E. nigrum, T. harzianum and F. equiseti provides a promising alternative to the use of fungicide spray to control B. cinerea on tomatoes.     

Study of the efficacy of Aureobasidium strains belonging to three different species: A. pullulans,A. subglaciale and A. melanogenum against Botrytis cinerea of tomato

The difference in antagonistic activity against the causal agent of grey mould (Botrytis cinerea) of tomato between Aureobasidium strains belonging to three different species, namely A. pullulans, A. melanogenum and A. subglaciale, was evaluated by in vitro and in vivo assays. In the yeast–pathogen direct interaction experiment, all the strains significantly reduced B. cinerea growth, with A. melanogenum the least efficient species (17.8% of reduction) compared to A. pullulans and subglaciale (22 and 27.8%). The non-volatile metabolites produced by all three species reduced mycelial growth between 95 and 100%. These metabolites were characterised by FT-IR spectroscopy as polysaccharides, lytic enzymes, siderophores and antibiotics. The inhibitory effect of Aureobasidium strains on pathogenic enzymes such as xylanase, polygalacturonase and pectinase was measured showing A. pullulans strains as capable of strong inhibition of xylanase, an enzyme directly related to the virulence of necrotrophic pathogens such as B. cinerea. Our data demonstrate that the different species of Aureobasidium isolated from a range of non-conventional environments exerted variable efficacy against B. cinerea, with A. pullulans as the most active species followed by A. subglaciale and A. melanogenum as ineffective and not suitable for biocontrol applications.     

Isolation and characterization of Bacillus subtilis KS1 for the biocontrol of grapevine fungal diseases

Bacillus subtilis KS1 was isolated from grape berry skin as a biological control agent against grapevine fungal diseases. KS1 was identified as a new strain of B. subtilis according to morphological, biochemical, and genetic analyses. In vitro bioassay demonstrated that KS1 suppressed the growth of Botrytis cinerea (the casual agent of grape grey mold) and Colletotrichum gloeosporioides (the casual agent of grape ripe rot). The biocontrol activity of KS1 against grapevine fungal diseases in vineyards was evaluated over a 3-year span (from 2007 to 2009). Downy mildew, caused by Plasmopara viticola, was reduced on berry skins and leaves by treatment with KS1. The KS1 genome possesses ituD and lpa-14 genes, both of which play a role in iturin A production followed by iturin A production in the culture. In contrast, mutants lacking both genes lost the antagonistic activity against B. cinerea and C. gloeosporioides and the activity in iturin A production, suggesting that the antagonistic activity of KS1 against grapevine fungal pathogens may depend on iturin A production. As KS1 showed tolerance to various chemical pesticides, chemical pesticides could be applied before and/or after KS1 treatment in vineyards. Due to its potential as a biological control agent against grape downy mildew, KS1 is expected to contribute to the further improvement of integrated pest management systems and to potentially reduce the amount of chemical fungicides applied in vineyards.     

Biocontrol of strawberry fruit infected by Botrytis cinerea: Effects on the microbial communities on fruit assessed by next‐generation sequencing

Fruit grey mould, caused by the fungus Botrytis cinerea, is known to be a harmful disease of strawberry at postharvest stage. However, effects of an application of biological control agents (BCAs) on strawberry fruit in terms of shift in the microbial community are still unknown. The present research aimed to investigate the effects of an application of BCAs on postharvest microbial populations present on strawberry fruits. Strawberry plants were sprayed with three kinds of BCA, RhizoVital 42 fl. (Bacillus amyloliquefaciens FZB42), Trianum‐P (Trichoderma harzianum T22) and Naturalis (Beauveria bassiana ATCC 74040), targeting Botrytis cinerea fungus. Control plots were composed of water and fungicide treatments. Microbial communities (bacteria and fungi) were analysed via next‐generation sequencing on an Illumina MiSeq. Analysis of 16S RNA and ITS rRNA sequences indicated that the BCAs application modified both bacterial and fungal community compositions and diversity. An application of two BCAs together had more effects on microbial community composition than a single application. These results suggest that BCAs can modify bacterial and fungal community composition and diversity on strawberry fruits, which may consequently improve the efficiency and establishment of these products on control of postharvest diseases of fruits, such as grey mould.     

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.     

Bacillus subtilis subsp. spizizenii MB29 controls alfalfa root rot caused by Fusarium semitectum

Medicago sativa L. is the most important forage legume in China. Reducing production losses caused by disease is an essential aspect of maximising alfalfa production. In the current study a Fusarium semitectum isolate collected from alfalfa roots exhibiting symptoms of root rot was proven to infect alfalfa by fulfilling Koch's postulates. A bacterial strain, MB29, also collected from alfalfa roots, was evaluated as a potential biocontrol agent against F. semitectum and a range of other alfalfa pathogens using in vitro tests. It was found that MB29 reduced the mycelia growth of all the pathogens assessed, and in the case of F. semitectum by as much as 84.47%. Furthermore, in vivo test showed that MB29 reduced the severity of rot symptoms in alfalfa seedlings resulting from F. semitectum infection. Strain MB29 was subsequently classified as Bacillus subtilis subsp. spizizenii using the Biolog MicroLog microbial identification system and sequence analysis of its 16S rDNA gene. Taken together these results indicate that B. subtilis subsp. spizizenii MB29 has great potential for the control of root rot diseases in alfalfa.     

The polyphagous plant pathogenic fungus Botrytis cinerea encompasses host-specialized and generalist populations

The host plant is often the main variable explaining population structure in fungal plant pathogens, because specialization contributes to reduce gene flow between populations associated with different hosts. Previous population genetic analysis revealed that French populations of the grey mould pathogen Botrytis cinerea were structured by hosts tomato and grapevine, suggesting host specialization in this highly polyphagous pathogen. However, these findings raised questions about the magnitude of this specialization and the possibility of specialization to other hosts. Here we report specialization of B. cinerea populations to tomato and grapevine hosts but not to other tested plants. Population genetic analysis revealed two pathogen clusters associated with tomato and grapevine, while the other clusters co-occurred on hydrangea, strawberry and bramble. Measurements of quantitative pathogenicity were consistent with host specialization of populations found on tomato, and to a lesser extent, populations found on grapevine. Pathogen populations from hydrangea and strawberry appeared to be generalist, while populations from bramble may be weakly specialized. Our results suggest that the polyphagous B. cinerea is more accurately described as a collection of generalist and specialist individuals in populations. This work opens new perspectives for grey mould management, while suggesting spatial optimization of crop organization within agricultural landscapes.     

Screening tomato-associated bacteria for biological control of grey mold on tomato

Aiming at discovering effective biocontrol agents (BCAs) against grey mold on tomato caused by Botrytis cinerea Pers., we selected 819 bacterial isolates from the surface as well as the interior of the roots, stems, and leaves of tomato plants grown in B. cinerea-infested fields. In a dual-culture assay, 116 isolates (14.16%) showed antagonism against B. cinerea and fewer ones against five additional tomato-associated fungal pathogens – Pythium ultimum, Phytophthora capsici, Fusarium oxysporum f. sp. lycopersici, Sclerotinia sclerotiorum and Ralstonia solanacearum. Thirty-one isolates with antagonism to B. cinerea and at least one of the five additional pathogens were assessed for their efficacy in controlling grey mold on tomato in a greenhouse test. Thirteen of them attained the efficacy over 50% and were subjected to the second greenhouse test, in which 12 isolates consistently accomplished the biocontrol efficacy over 50%, with isolates ABc28 and ABc22 achieving the efficacy of 66.71% and 64.90%, respectively. Under greenhouse conditions, the above two as well as isolates ABc2, ABc11 and ABc17 increased tomato biomass by more than 20% in comparison with the control. The 12 antagonistic isolates accomplishing the biocontrol efficacy over 50% in both greenhouse tests were considered potential BCAs against grey mold, which were identified as Pseudomonas spp., Pantoea spp., Bacillus spp. and Chryseobacterium spp. Ten of them were found to produce at least one of the three hydrolytic enzymes (protease, cellulase and chitinase) and/or siderophore, which might be involved in their mechanisms of suppressing the disease. Based on the origin of these 12 strains, the leaf tissue, especially the leaf interior, of tomato plants grown in a B. cinerea-infested field appears to be a good source of potential BCAs against grey mold.     

Additional experiences to elucidate the microbial component of soil suppressiveness towards strawberry black root rot complex

Several studies were carried out to investigate the soil microbial components involved in suppressing strawberry black rot root which occurs throughout the Italian strawberry growing region. Quantitative and qualitative evaluation of fungi involved in black root rot were combined with several soil microbial parameters involved in soil suppressiveness towards black root rot agents. The first survey, carried out in an intensively cultivated area of northern Italy, identified Rhizoctonia spp. as the main root pathogen together with several typical weak pathogens belonging to the well‐known black rot root complex of strawberry crop: Cylindrocarpondestructans, Fusarium oxysporum, F. solani, Pestalotia longiseta and others. The root colonisation frequency of strawberry plants increased strongly from autumn to spring at harvesting stage. Rhizoctonia spp. were the only pathogens which followed the rising trend of root colonisation with relative frequency; all the weak pathogens of strawberry black root rot complex did not vary their frequency. Only non‐pathogenic fungi decreased from autumn to spring when at least 60% of colonising fungi were represented by Rhizoctonia. These data suggested that the late vegetative stage was the best time to record the soil inoculum of root rot agents in strawberry using root infection frequency as a parameter of soil health. A further study was performed in two fields, chosen for their common soil texture and pH, but with significant differences in previous soil management: one (ALSIA) had been subjected to strawberry monoculture without organic input for several years; the other (CIF) has been managed according to a 4‐year crop rotation and high organic input. In this study Pythium artificially inoculated was adopted as an indicator for the behaviour of saprophytically living pathogens in bulk soil. Pythium showed a sharp, different response after inoculation in bulk soil from the two soil systems evaluated. Pythium was suppressed only in the CIF field where the highest levels of total fungi and fluorescent bacteria and highest variability were observed. The suppressiveness conditions towards Pythium, observed in the CIF and absent in the ALSIA field, corresponded with the root infection frequency recorded at the late vegetative stage on strawberry plants grown in the two fields: strawberry plants from the CIF field showed lower root colonisation frequency and higher variability than that recorded on those coming from the ALSIA field.     

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.     

Response of three root rot fungi to strawberry phenolics and the relation of phenolics to disease resistance

Pythium irregulare, Rhizoctonia solani, and Alternaria alternata, usually associated with strawberry root rot diseases, were sensitive in vitro to several phenolics present in strawberry roots, fruits, and leaves, P. irregulare was the most sensitive. Eighteen strawberry cultivars were divided into two types, based on qualitative phenolic content. Five contained an unidentified xanthone and generally less kaempferol-7-glucoside than the remaining thirteen. Although these differences were not correlated with resistance to three strawberry diseases, quantitative difference of certain phenolics may be important in seasonal resistance to root rot pathogens.Cooperative Investigations, Agricultural Research Service, United States Department of Agriculture and Plant and Soil Science Department, School of Agriculture, Southern Illinois University, Carbondale, Illinois.Research Plant Pathologist, formerly located at Carbon dale, Illinois.     

In vitro and in vivo antimicrobial activity of Xenorhabdus bovienii YL002 against Phytophthora capsici and Botrytis cinerea

Aims: Developing new bio‐agents to control plant disease is desirable. Entomopathogenic bacteria Xenorhabdus spp. have potential antimicrobial activity in agriculture. This work was conducted to evaluate the antimicrobial activity of Xenorhabdus bovienii YL002 on plant pathogenic fungi and oomycete in vitro and the efficiency of this strain to reduce the in vivo incidence of grey mould rot on tomato plants caused by Botrytis cinerea and leaf scorch on pepper plants caused by Phytophthora capsici. Methods and Results: The antimicrobial activity of X. bovienii YL002 was firstly determined on in vitro plant pathogenic fungi and oomycete and then on tomato fruits and plants infected with B. cinerea and pepper plants infected with P. capsici. The cell‐free filtrate of X. bovienii YL002 exhibited highest inhibition effects (>98%) on mycelia growth of P. capsici and B. cinerea. The 50% inhibition concentration (EC₅₀) of the methanol‐extracted bioactive compounds (methanol extract) of the cell‐free filtrate against P. capsici and B. cinerea were 164·83 and 42·16 μg ml^?1. The methanol extract also had a strong effect on the spore germination of P. capsici and B. cinerea, with a EC₅₀ of 70·38 and 69·33 μg ml^?1, respectively. At 1000 μg ml^?1, the methanol extract showed a therapeutic effect of 70·82% and a protective effect of 77·4% against B. cinerea on tomato plants compared with the control. The methanol extract also showed potent effect against P. capsici, with a therapeutic effect of 68·14% and a protective effect of 65·46% on pepper plants compared with the control. Conclusions: Xenorhabdus bovienii YL002 produces antimicrobial compounds with strong activity on plant pathogenic fungi and oomycete and has the potential for controlling grey mould rot of tomato plants and leaf scorch of pepper and could be useful in integrated control against diverse plant pathogenic fungi and oomycete. Significance and Impact of the Study: This study showed the potential that X. bovienii YL002 can be used to control the grey mould rot caused by B. cinerea on tomato plants and leaf scorch caused by P. capsici on pepper plants with the objective to reduce treatments with chemical fungicides.     

The rising threat of fungicide resistance in plant pathogenic fungi: Botrytis as a case study

The introduction of site-specific fungicides almost 50 years ago has revolutionized chemical plant protection, providing highly efficient, low toxicity compounds for control of fungal diseases. However, it was soon discovered that plant pathogenic fungi can adapt to fungicide treatments by mutations leading to resistance and loss of fungicide efficacy. The grey mould fungus Botrytis cinerea, a major cause of pre- and post-harvest losses in fruit and vegetable production, is notorious as a ‘high risk’ organism for rapid resistance development. In this review, the mechanisms and the history of fungicide resistance in Botrytis are outlined. The introduction of new fungicide classes for grey mould control was always followed by the appearance of resistance in field populations. In addition to target site resistance, B. cinerea has also developed a resistance mechanism based on drug efflux transport. Excessive spraying programmes have resulted in the selection of multiresistant strains in several countries, in particular in strawberry fields. The rapid erosion of fungicide activity against these strains represents a major challenge for the future of fungicides against Botrytis. To maintain adequate protection of intensive cultures against grey mould, strict implementation of resistance management measures are required as well as alternative strategies with non-chemical products.     

The mixture of kresoxim‐methyl and boscalid,an excellent alternative controlling grey mould caused by Botrytis cinerea

Grey mould, caused by the fungus Botrytis cinerea, is one of the most destructive diseases in greenhouses for which serious fungicide resistance has developed. Between 2003 and 2005, 213 isolates of B. cinerea from two geographical regions were characterised for baseline sensitivity to kresoxim‐methyl. In the absence of salicylhydroxamic acid (SHAM), the mean 50% effective concentration (EC₅₀) values were 6.67 ± 0.61 (mean ± SD) and 0.37 ± 0.10 mg L^?1 during growth and germination, respectively. In the presence of 100 mg L^?1 SHAM, baseline sensitivities were distributed as unimodal curves with mean EC₅₀ values of 2.38 ± 0.21 and 0.28 ± 0.09 mg L^?1 for inhibiting growth and inhibiting germination, respectively. The mixture of kresoxim‐methyl and boscalid showed good control efficacy against strawberry grey mould disease. After the mixture was extensively used on strawberry for 2 years, 50 isolates were collected and determined for their sensitivity to kresoxim‐methyl and boscalid, respectively. The mean EC₅₀ of germination inhibition by boscalid was 0.39 ± 0.08 mg L^?1. The mean EC₅₀ of germination inhibition by kresoxim‐methyl was 0.26 ± 0.07 mg L^?1 in the presence of 100 mg L^?1 SHAM. Sensitivities of B. cinerea to both kresoxim‐methyl and boscalid did not show any significant decrease. These results suggest that their mixture is a satisfactory alternative candidate for management of grey mould disease in greenhouses.     

Vermicompost-based bioformulation for the management of sugarbeet root rot caused by Sclerotium rolfsii

Vermicompost-based bioformulations of bacterial and fungal biocontrol agents were examined against sugarbeet root rot caused by Sclerotium rolfsii. The result showed that the Pseudomonas fluorescens strain Pf1 in combination with either Trichoderma asperellum strain TTH1 or Bacillus subtilis strain EPCO-16 performed better in reducing disease next to the chemical difenoconazole. Similarly, enhanced yield was observed in the same combination treatments under both pot and field conditions.