Brown Rot Incidence Research Articles

The Crop Load Affects Brown Rot Progression in Fruit Orchards: High Fruit Densities Facilitate Fruit Exposure to Spores but Reduce the Infection Rate by Decreasing Fruit Growth and Cuticle Cracking

Brown rot, triggered by Monilinia spp., causes significant economic losses in fruit crop and it is mainly controlled by chemicals with inherent environmental costs. Controlling brown rot spreading by diminishing fruit susceptibility to the disease, via sustainable cultural practices, is a promising approach. In a two years experiment (2014-2015) on a peach (Prunus persica) orchard, we controlled fruit growth rates by varying the fruit load. Fruit thinning practices enhanced the fruit growth and laboratory analyses showed that, in both 2014 and 2015 samples, fast growing fruits were more susceptible to infection when in contact with conidia suspension of Monilinia laxa. In the field, brown rot infection took place in 2014 and not in 2015. In 2014, trees subject to moderate thinning intensities had the highest brown rot incidence. We argue that this is due to the fact that, for null thinning, slow growing fruits are less susceptible to the infection while, for intense thinning, even if faster growing fruits are more susceptible to infection, the lower fruits density reduces per-contact probability of infection. We compared meteorological data of 2014 and 2015 and we argue that brown rot did not spread in 2015 due to an absence of favorable conditions, summarized as the number of rainy days with mean temperature between 22 and 26 °C , in the period of fruit susceptibility.

Biological control of brown rot in stone fruit using Bacillus amyloliquefaciens CPA-8 under field conditions

Different treatments based on the biocontrol agent (BCA) Bacillus amyloliquefaciens CPA-8 to control brown rot under field conditions were evaluated as alternative to chemical applications. As part of a well-designed disease program that enables the integration of BCAs into cropping systems, testing of the sensitivity of Monilinia laxa and Monilinia fructicola at different doses of CPA-8 were conducted in stone fruit under laboratory conditions. CPA-8 dose of 107 CFU mL−1 reduced more than 60.0 and 75.5% of brown rot incidence and severity, respectively. Once in the orchard, different degree of biocontrol activity was obtained depending on the inoculum pressure, which was mainly associated with meteorological conditions. Under drastic disease pressure, neither CPA-8 treatment nor the chemicals controlled the disease at harvest and only the chemical treatment reduced postharvest brown rot incidence. However, when Monilinia spp. incidence was close to the standard levels recorded in the area, treatments based on CPA-8 formulations proved to be efficacious. At harvest, BA3, BA4 treatments (CPA-8 optimised products) and PF + BA3 treatment (Penicillium frequentans combined with CPA- 8) reduced Monilinia spp. incidence compared to the control (54.7–64.1%) and similar to the chemicals. At postharvest, almost all CPA-8-based treatments (except PF + BA3) controlled the pathogen with BA4 treatment being as much effective as the chemicals (50.3% of disease reduction). Finally, the population dynamics of CPA-8 on treated fruit surface remained after treatment application, at harvest and at postharvest shelf-life (>104 CFU cm−2). This study highlights the potential of B. amyloliquefaciens CPA-8 as alternative or complementary strategies to control Monilinia spp.

Researches on the reaction of apple varieties to Monilinia fructigena fungus attack

The antagonistic effects of Debaryomyces hansenii KI2a, D. hansenii MI1a and Wickerhamomyces anomalus BS91 were tested against Monilinia fructigena and Monilinia fructicola in in vitro and in vivo trials.All yeast strains demonstrated antifungal activity at different levels depending on species, strain and pathogen. D hansenii KI2a and W. anomalus BS91 showed the highest biocontrol activity in vitro; the production of hydrolytic enzymes, killer toxins and volatile organic compounds (VOCs) were hypothesized as their main mechanisms of action against pathogens. D hansenii KI2a and W. anomalus BS91 significantly reduced brown rot incidence and severity on peach and plum fruits artificially inoculated with M. fructigena and M. fructicola, especially when applied 24 h before pathogen inoculation. On the opposite, D. hansenii MI1a exhibited weak antagonistic activity towards M. fructigena on peach and plum fruits and was ineffective against M. fructicola. The noticeable ability of W. anomalus BS91 to control brown rot could be also correlated with its high capacity to colonize the wound tissue and to increase its population density.Accordingly, the antagonistic strains of D. hansenii and W. anomalus could be proposed as active ingredients for the development of biofungicides against Monilinia species that are responsible for considerable economic losses in stone fruit crops.

Competition is the mechanism of biocontrol of brown rot in stone fruit by Penicillium frequentans

The mechanism of biocontrol of brown rot in stone fruit by Penicillium frequentans Westling (Pf909) was investigated using in vitro and in vivo growth assays and a benomyl-resistant strain of Monilinia fructicola (G Winter) Honey (Mf3C). For the in vitro assays, Pf909 and Mf3C conidia were suspended in Czapek-Dox broth, which was amended or not amended with a skin extract of mature peaches. The growth and germination of Pf909 and Mf3C conidia were determined by counting the number of colony-forming units on potato dextrose agar plates, which were amended or not amended with 0.5 g ml−1 benomyl. In some of the assays, germinated Pf909 conidia were used before their exposure to Mf3C conidia. For the in vivo assays, healthy cherries were inoculated with Mf3C conidia before and after applying Pf909 conidia on the cherry surface and the incidence of brown rot was recorded for seven days. Since we found that Pf909 conidia compete with Mf3C conidia for space and nutrients in the different assays, we concluded that competition is the probable primary mechanism of biocontrol of Pf909.

Contribution of Mid-Season Cover Sprays to Management of Peach Brown Rot at Harvest.

Four protectant fungicides applied as midseason cover sprays were quantitatively assessed for their ability to reduce brown rot caused by Monilinia fructicola during the preharvest fruit ripening periods in the 2012 through 2015 growing seasons. No fungicides were applied during bloom or during the preharvest period. Treatment programs consisted of captan, sulfur, ziram, and thiram applications beginning at early shuck-split stage and ending with the final cover spray at 23 to 26 days before harvest. The incidence of brown rot at harvest was determined by examining 41 to 91 fruit for symptoms of rot on each of four replicate trees for each treatment. The incidence of sporulating blossom blight cankers was assessed during the preharvest period at 8, 15, and 22 days after the final cover spray. An in vivo bioassay was also conducted at 7, 14, and 21 days after the final cover spray to ascertain the level of fungicide residue during the preharvest period. The bioassay uses conidia germination as a quantitative indicator of effective residue. Results of the harvest assessment showed that captan cover sprays significantly reduced brown rot incidence in all years of the study. Furthermore, results of the bioassay demonstrated that fungicide residue was the mechanism by which this control occurred. None of the other fungicide cover spray programs contributed significantly to brown rot control at harvest in any year, and bioassay results showed insufficient residue to inhibit conidial germination. Antisporulant activity against blossom blight cankers was not observed for any fungicide program, indicating that reducing inoculum production from this source was not a mechanism for brown rot control. The captan and sulfur programs provided very good control of peach scab incidence and severity, caused by Fusicladium carpophilum, while the ziram and thiram programs failed to control this disease. These findings demonstrated that captan cover sprays can contribute significantly to control of brown rot at harvest, thereby augmenting the efficacy and consistency of management by preharvest fungicide programs. Furthermore, any reduction of the M. fructicola population by the captan cover sprays should reduce selection pressure against the site-specific fungicides commonly used during the preharvest period, thereby prolonging their useful life for brown rot control.

Effect of thyme oil vapour exposure on the brown rot infection, phenylalanine ammonia-lyase (PAL) activity, phenolic content and antioxidant activity in red and yellow skin peach cultivars

Influence of thyme oil vapour on the incidence of brown rot (Monilinia laxa) was investigated in the yellow-flesh peach cultivars consisting of red skin ‘Jim Dandy’, ‘Novadonna’, ‘Scarlet Rich’ and ‘Transvalia’, and yellow skin ‘Earli Gold’, ‘Kakamas’, ‘Kesie’ and ‘Summer Sun’. Fruit were exposed to thyme oil (96μLL−1) vapour for 24h, subsequently inoculated with the pathogen (105sporesmL−1), and stored for 14d at 0°C, followed by 6d shelf-life conditions at 15°C, 75% RH. Four varieties, i.e. ‘Scarlet Rich’, ‘Transvalia’, ‘Earli Gold’ and ‘Kesie’ were then selected to study the effect of thyme oil vapour on the phenylalanine ammonia-lyase (PAL) activity and hydroxycinnamic acids (chlorogenic and caffeic acids) content. The effect of thyme oil vapour on brown rot incidence, phenolic content and antioxidant activity was also investigated in naturally infected fruit. Thyme oil vapour reduced the incidence of brown rot by increasing the activity of PAL, the content of catechin, chlorogenic and caffeic acids, and via enhancing antioxidant scavenging capacity. However, the key finding from this study was that thyme oil vapour exposure is far more suitable for red skin peaches than their yellow skin counterparts.

Potential of a new strain of Bacillus amyloliquefaciens BUZ-14 as a biocontrol agent of postharvest fruit diseases

The biocontrol potential of the Bacillus amyloliquefaciens strain BUZ-14 was tested against the main postharvest diseases of orange, apple, grape and stone fruit. After characterizing the temperature and pH growth curves of strain BUZ-14, its in vitro antifungal activity was determined against Botrytis cinerea, Monilinia fructicola, M. laxa, Penicillium digitatum, P. expansum and P. italicum. Subsequently, in vivo activity was tested against these pathogens by treating fruit with cells, endospores and cell-free supernatants. The in vitro results showed that BUZ-14 inhibited the growth of all the pathogens tested corresponding to the least susceptible species, P. italicum, and the most susceptible, M. laxa. In vivo tests corroborated these results as most of the treatments decreased the incidence of brown rot in stone fruit from 100% to 0%, establishing 107 CFU mL−1 as the minimum inhibitory concentration. For the Penicillium species a preventive treatment inhibited P. digitatum and P. italicum growth in oranges and reduced P. expansum incidence in apples from 100% to 20%. Finally, it has been demonstrated that BUZ-14 was able to survive and to control brown rot in peaches stored at cool temperatures, making it a very suitable biocontrol agent for application during the post-harvest storage and marketing of horticultural products.

Fruit maturity and post-harvest environmental conditions influence the pre-penetration stages of Monilinia infections in peaches

Brown rot caused by the fungi Monilinia laxa (Aderhold and Ruhland) Honey, M. fructicola (Winter) Honey, or M. fructigena (Aderhold and Ruhland) is a serious fungal disease of peaches. The fungal infection process begins when fungal conidia germinate on the fruit surface to produce germ tubes and/or appressoria, and the incidence of brown rot increases as fruit approaches maturity. The interaction between the fungal infection process, peach maturity, and the environmental conditions is not well understood. Accordingly, the objectives of this investigation were to investigate germ tube and appressorial formation by M. laxa and M. fructicola when they were exposed to peach skin from mature and immature fruit at various temperatures and relative humidities (RHs). The greatest number of germ tubes was found when M. laxa or M. fructicola was incubated in culture medium which contained a skin extract of mature peaches. In contrast, the greatest number of appressoria was found when M. laxa or M. fructicola was incubated in culture medium which contained a skin extract of immature peaches. Although M. fructicola produced the same number of germ tubes and appressoria at 4°C, M. fructicola produced more germ tubes than appressoria at temperatures higher than 10°C. M. laxa produced more germ tubes than appressoria at any temperature, except when it was incubated for 48h on culture medium which contained a skin extract of immature peaches at 10°C at 80% or 100% RH, or at 25°C at 60% RH. M. laxa conidia germinated better than M. fructicola conidia at low temperatures. Germ tube and appressorial formation by Monilinia spp. were influenced by fruit postharvest handling. The number of germ tubes that were formed by M. laxa conidia was significantly greater than that for M. fructicola when the conidia were incubated at 100% RH, and this number increased after 3days of refrigeration. The number of appressoria that were formed by both Monilinia spp. also increased after 3 consecutive days of refrigeration. Negligible or no germination of M. fructicola and M. laxa conidia occurred when the RH was 60%. We concluded that the dissimilar abilities of M. laxa and M. fructicola to germinate and form appressoria at low temperatures conferred a competitive advantage to M. laxa to survive during fruit postharvest refrigeration and cold storage at 4°C.

Postharvest biocontrol ability of killer yeasts against Monilinia fructigena and Monilinia fructicola on stone fruit

The antagonistic effects of Debaryomyces hansenii KI2a, D. hansenii MI1a and Wickerhamomyces anomalus BS91 were tested against Monilinia fructigena and Monilinia fructicola in in vitro and in vivo trials.All yeast strains demonstrated antifungal activity at different levels depending on species, strain and pathogen. D hansenii KI2a and W. anomalus BS91 showed the highest biocontrol activity in vitro; the production of hydrolytic enzymes, killer toxins and volatile organic compounds (VOCs) were hypothesized as their main mechanisms of action against pathogens. D hansenii KI2a and W. anomalus BS91 significantly reduced brown rot incidence and severity on peach and plum fruits artificially inoculated with M. fructigena and M. fructicola, especially when applied 24 h before pathogen inoculation. On the opposite, D. hansenii MI1a exhibited weak antagonistic activity towards M. fructigena on peach and plum fruits and was ineffective against M. fructicola. The noticeable ability of W. anomalus BS91 to control brown rot could be also correlated with its high capacity to colonize the wound tissue and to increase its population density.Accordingly, the antagonistic strains of D. hansenii and W. anomalus could be proposed as active ingredients for the development of biofungicides against Monilinia species that are responsible for considerable economic losses in stone fruit crops.

Use of sodium metasilicate for management of peach brown rot

ABSTRACT Peach brown rot, caused by the Monilinia fructicola fungus, is the main disease affecting peach crops, and it is mainly controlled via frequent fungicide applications. This study aimed at searching for alternatives to the intensive use of chemicals, evaluating silicon doses to control pre and postharvest peach brown rot and their influence on maturation parameters and fruit quality. Treatments consisted of control (water) and sodium metasilicate doses (2 g L-1, 4 g L-1, 6 g L-1, 8 g L-1 and 10 g L-1 of water). The following assessments were made: spore germination and in vitro mycelial growth, brown rot incidence, soluble solids, titratable acidity, flesh firmness, total polyphenol content and fruit ethylene production and respiration rate. The 2 g L-1 dose reduced spore germination by 95 %. Doses of 6 g L-1 and 8 g L-1 satisfactorily reduced the disease incidence in the field, with 77 % and 89.2 % control, respectively. Sodium metasilicate resulted in the maintenance of great fruit firmness, reduced respiration and ethylene production and increased total polyphenol synthesis, but it did not influence the titratable acidity or soluble solids. Applying 6 g L-1 may potentially control pre and postharvest peach brown rot, besides increasing the total polyphenol synthesis and maintaining a higher flesh firmness.

Effects of irrigation deprivation and ground cover (Trifolium repens) in the tree row on brown rot incidence in peach

Brown rot can lead to considerable fruit losses in peach orchards and cultural practices likely to contend this major disease have to be promoted. In order to limit peach brown rot incidence in a three-year-old mid-season maturing peach orchard of the cultivar ’Ruby Bright’, four combinations of irrigation and soil management treatments were assessed: conventional (Conv) irrigation (I) and soil management (S) (ConvI+ConvS); modified (Mod) irrigation and soil management (ModI+ConvS); conventional irrigation and modified soil management (ConvI+ModS); and modified irrigation and soil management (ModI+ModS). Conventional irrigation and soil management in the tree row consisted of irrigation scheduling using tensiometer readings and herbicide use, respectively. Modified irrigation and soil management in the tree row consisted of water deprivation during stage III of fruit development and ground cover with white clover, respectively. For four consecutive years (2010–2013), in the conditions of the Middle Rhone Valley in France, the lowest and highest brown rot incidence were detected under (ModI+ModS) and (ConvI+ConvS), respectively, whereas brown rot incidence under (ModI+ConvS) and (ConvI+ModS) was intermediate. This lower brown rot incidence under the modified treatments occurred from one to two weeks before fruit maturity and was still observed for several days in post-harvest storage. Ground cover with white clover was shown to limit water availability in the soil after heavy rainfall compared to bare soil, probably limiting peach growth variations, well-known as a possible source of detrimental microcracks at the fruit surface. This suggests that under our conditions appropriate cultural practices, water deprivation and a clover crop cover in the tree row possibly decrease peach disease sensitivity, which might lead to the reduced use of pesticide sprays to control brown rot in the orchard.

Different defense responses and brown rot control in two Prunus persica cultivars to essential oil vapours after storage

The effectiveness of thyme and cinnamon oil vapours on the control of Monilinia laxa in peaches was compared by investigating the induction of defense-related and antioxidant enzymes, and the production of phenolic compounds after different storage times.In Experiment 1, ‘Spring Princes’ and ‘Sonnet’ peaches were exposed to thyme or cinnamon oil vapours when harvest at commercial maturity. Before or after the treatments fruit were inoculated with M. laxa and held for 3 and 5 d at 25°C. In Experiment 2, fruit were inoculated after thyme or cinnamon oil vapour treatment and stored at 0°C for 12 d, followed by 2 d shelf life at 15°C. In Experiment 3, naturally infected fruit were exposed to thyme or cinnamon oil vapour treatment and then stored as mentioned in Experiment 2 for 12 d at 0°C after which they were removed from cold storage held at 15°C for 5 d to simulate the retail shelf condition. Thyme oil vapour increased activities of defense-related enzymes, total phenolic content and significantly reduced the incidence and severity of brown rot in ‘Spring Princess’ and ‘Sonnet’. The other treatments, cinnamon oil vapour, and iprodione fungicide spray were less effective. However, the control of brown rot was more effective with thyme oil vapour than the cinnamon oil vapour in ‘Spring Princess’. Thyme oil vapour as botanical fungicide showed good potential for practical application for organic markets to reduce the brown rot decay at postharvest stage. However, its effectiveness and related host responses can vary with cultivar.

Fruit injury in organic fruit production and its relationship to brown rot caused by Monilinia spp.

In a two-year Hungarian study, the temporal progress of brown rot incidence and various injury types were studied in organic fruit orchards and the relationship between brown rot and injury types was determined. Results showed that brown rot reached an almost 20% incidence level in both years. Total injury incidence reached up to 5.3 and 19.8% in the two years. In all cases, insect injury incidence was the highest among injury types in most assessment dates. Incidence levels of other injury types (bird injury, mechanical injury and other injury) began to increase, but none of those reached levels >4%. Pearson’s correlation coefficients showed that brown rot incidence correlated significantly with the incidence of insect injury. In addition, brown rot incidence and the incidence levels of bird injuries was also significantly correlated. High injury and brown rot incidence levels suggest further improvements on organic fruit protection.

An innovative use of DA-meter for peach fruit postharvest management

The DA-meter is a hand-held instrument developed from vis/NIR spectroscopy that measures the index of absorbance difference (IAD) correlated with the flesh chlorophyll-α content of fruit. It was used to divide in two different ripening classes, class I (climacteric peak) and class II (onset of climacteric), harvested fruit belonging to three peach cultivars. At harvest and after 6 days of storage at 20°C, quality parameters such as flesh firmness (FF), soluble solid contents (SSC), ethylene emission and brown rot incidence were evaluated. Data on ethylene production reported a different emission of phytormone at harvest relating to peach variety and among the two IAD classes. In addition, the IAD values showed a high correlation with FF, while SSC being ethylene-independent did not show marked differences between ripening stages. With respect to brown rot, after 3 days of shelf-life, data from artificial infections, revealed a lesion diameter significantly larger on fruits of class I (10 and 13mm) than those on class II (8 and 9mm) for ‘Springbelle’ and ‘Redhaven’, respectively. Similarly, in all trials, the incidence of Monilinia rots in fruit natural infected was significantly higher within class I compare to class II. The present work showed the possibility of sorting asymptomatic fruit, harvested at a commercial maturity, by DA-meter, into two IAD classes that will show different brown rot incidence during storage.

Postharvest Strategies for Managing Phytophthora Brown Rot of Citrus using Potassium Phosphite in Combination with Heat Treatments.

Phytophthora brown rot, caused by several species of Phytophthora, is an economically important disease of citrus in areas with rainfall during the late stages of fruit development. Recent export restrictions of California orange fruit to China due to the presence of brown rot caused by the quarantine pathogen Phytophthora syringae have mandated more rigorous disease management. We evaluated postharvest applications with the phosphonate fungicide potassium phosphite in combination with heat treatments. In timing studies, potassium phosphite at 1,500 μg/ml was most effective when applied within 18 h after inoculation of orange fruit with P. citrophthora, reducing the incidence of decay by >96% as compared with the control. Potassium phosphite was also highly effective in inoculations with P. syringae. Heated water treatments at 60°C were consistently and highly effective in reducing the incidence of brown rot after inoculation with P. citrophthora, whereas treatments at 55 or 50°C were more variable and generally less effective. Two-stage treatments of fruit were conducted in the laboratory to simulate current packinghouse practices and to evaluate any interaction of the efficacy of potassium phosphite with treatments of two commonly used postharvest fungicides (i.e., imazalil and thiabendazole [TBZ]) or a postharvest carnauba-based fruit coating. In these studies, an aqueous imazalil-potassium phosphite (2,000 μg/ml) dip at ambient temperature that was followed by a spray treatment of imazalil and TBZ prepared in fruit coating significantly reduced the incidence of brown rot from the control. When the aqueous dip was applied at 54°C, brown rot developed in only 1% of the fruit as compared with 76% in the water control. The efficacy of potassium phosphite was also demonstrated in commercial packinghouse treatments. Based on our research, this fungicide was registered for postharvest use against brown rot of citrus and is exempt from tolerance in the United States and many other countries.

Limiting brown rot incidence in peach with tree training and pruning

Introduction. To limit peach brown rot incidence in a mid-season peach orchard cv. ‘Conquise’, three combinations of tree training and pruning treatments were assessed: open vase training with conventional pruning (Control); open vase with centrifugal pruning (CentP); vertical axis training with centrifugal pruning (Axis). Materials and methods. The test orchard was divided into four blocks, each with the three tree management treatments in a randomized complete block design. Brown rot incidence as well as fruit production and quality were assessed over five successive years. Results and discussion. The lowest brown rot incidence values were detected under Axis and the highest under Control, with values for CentP being intermediate. The reduced incidences under CentP and Axis training were observed around two weeks before fruit maturity and were maintained until post-harvest storage. Compared to the Control, CentP and Axis resulted in higher trunk cross sectional areas, yields and monetary returns. CentP and Axis also tended to enhance peach internal quality, i . e ., increase of total soluble solids, but work time devoted to pruning and thinning under CentP and Axis was greater than for the Control. Conclusion. Appropriate tree management, a vertical axis training system and centrifugal pruning, appears to decrease peach disease sensitivity. This could result in reduced use of pesticide sprays for brown rot control.

Gnomoniopsis castanea is the main agent of chestnut nut rot in Switzerland

Nuts of sweet chestnut have been an important food source for the alpine population in Switzerland since the Middle Ages and are still valued today for the preparation of traditional food commodities. Nut quality is reduced by insect damage and by various pathogenic fungi. In the last few years, producers and consumers perceived an increase of brown nut rot; while the nut rot agent Gnomoniopsis castanea was reported locally in southern Switzerland, its presence has not been investigated over large areas until now. This study assessed the incidence of brown nut rot and identified the causal agent present in Switzerland. Fully ripened nuts were collected from the main sweet chestnut growing areas of Switzerland. A filamentous fungus morphologically identified as G. castanea was isolated from 10 to 91% of the sampled nuts, despite only 3 to 21% of the sampled nuts showing brown rot symptoms. This fungus was isolated from symptomatic chestnuts as well as from apparently healthy chestnuts. Our results suggest a possible endophytic lifestyle in ripened nuts as well as in branches, leaves and unripe nuts as previously found. Species identity of 45 isolates was confirmed by EF-1alpha , beta-tubulin and ITS sequencing. Concatenation of β -tubulin and calmodulin sequences showed that several haplotypes were present at each sampling locality. No other nut rot pathogens could be isolated in this study, suggesting that G. castanea is the main causal agent of nut rot in Switzerland. The presence of this species is reported for the first time in a site in northern Switzerland. Further studies are needed to assess the influence of meteorological conditions and chestnut varieties on the incidence of G. castanea in order to provide prevention strategies for chestnut growers. Normal 0 21 false false false FR-CH X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Calibri,sans-serif;}

Harvest and postharvest brown rot of fruit in relation to early latent infection caused by Monilinia spp. in Hungary

In this study, the effect of early latent infection caused by Monilina spp. on harvest and postharvest brown rot of sour cherry and peach was investigated. Two field experiments were performed in commercial orchards located at Eperjeske on sour cherry and at Siófok on peach in 2013 and 2014 in order to study the possible relationship between the incidence of early latent infection caused by Monilinia spp. and the incidence of harvest and postharvest brown rot. No latent infection was recorded at popcorn phanological stage of the trees at both locations. The maximum incidence was detected during the pit hardening period. There was a positive correlation between the incidence of latent infection and harvest or postharvest brown rot. The average incidence of latent infection during the crop season explained approximatelly 20% of the total variation in the incidence of postharvest brown rot.

Chitosan boehmite-alumina nanocomposite films and thyme oil vapour control brown rot in peaches (Prunus persica L.) during postharvest storage

Brown rot (Monilinia spp.) affects the shelf life, fruit quality and marketability of peaches (Prunus persica L.). Increasing consumer concern regarding food safety makes it necessary to search for natural environmentally friendly alternative products for postharvest disease control. In this investigation, polyethylene terephthalate (PET) punnets containing thyme oil (TO sachets) and sealed with chitosan/boehmite nanocomposite lidding films significantly reduced the incidence and severity of brown rot caused by Monilinia laxa in artificially inoculated peach fruits (cv. Kakawa) held at 25 °C for 5 days. Furthermore, PET punnets containing TO sachets and sealed with chitosan/boehmite nanocomposite lidding films significantly reduced the brown rot incidence to 10% in naturally infected fruits stored at 0.5 °C, 90% RH for 7 days and at the simulated market shelf conditions for 3 days at 15 °C, 75% RH. The chitosan/boehmite nanocomposite lidding films maintained the active components of thyme oil, thymol (56.43% RA), caryophyllen (9.47% RA) and β-linalool (37.6% RA) within the (head space volatiles) punnet. Panellists preferred fruits packed from commercial punnet containing thyme oil (sachets) and sealed with chitosan/boehmite nanocomposite lidding films due to overall appearance, taste, and natural peach flavour.

Effect of hot water treatment on peach volatile emission and Monilinia fructicola development

The effect of hot water treatment (HWT) to control peach brown rot was investigated. Peaches were dipped in water at 60°C for 60 s and artificially inoculated with Monilinia fructicola conidia. HWT failed to control brown rot if applied before inoculation and microscopic observations revealed a stimulatory effect on germ tube elongation of M. fructicola conidia placed immediately after HWT on the fruit surface, compared to the control. The influence of fruit volatile emission due to HWT was performed on the pathogen conidia exposed to the headspace surrounding peaches. The results showed an increase of M. fructicola conidial germination ranging from 33 to 64% for cultivars Lucie Tardibelle and Red Haven heat‐treated peaches, respectively, compared to the control. The volatile blend emitted from heat‐treated fruit was analysed by solid‐phase microextraction/gas chromatography‐mass spectrometry (SPME/GC‐MS) and proton transfer reaction‐time of flight‐mass spectrometry (PTR‐ToF‐MS). Fifty compounds were detected by SPME/GC‐MS in volatile blends of cv. Lucie Tardibelle peaches and significant differences in volatile emission were observed among heated and control fruit. Using PTR‐ToF‐MS analysis, acetaldehyde and ethanol were detected at levels 15‐ and 28‐fold higher in heated fruit compared to unheated ones, respectively. In vitro assays confirmed the stimulatory effect (60 and 15%) of acetaldehyde (0·6 μL L−1) and ethanol (0·2 μL L−1) on M. fructicola conidial germination and mycelial growth, respectively. The results showed that volatile organic compounds (VOCs) emitted from heat‐treated peaches could stimulate M. fructicola conidial germination, increasing brown rot incidence in treated peaches when the inoculation occurs immediately after HWT.