Brown Rot Infection Research Articles

Genome-wide association analysis of Monilinia fructicola lesion in a collection of Spanish peach landraces

Brown rot, caused by the Monilinia spp., is the disease that causes the greatest losses in stone fruit worldwide. Currently, M. fructicola has become the dominant species in the main peach production area in Spain. The fruit cuticle is the first barrier of protection against external aggressions and may have a key role in the susceptibility to brown rot. However, information on the role of skin fruit on the resistance to brown rot in peach is scarce. Previous genetic analyses in peach have demonstrated that brown rot resistance is a complex and quantitative trait in which different fruit parts and resistance mechanisms are involved. To search for genomic areas involved in the control of the cultivar susceptibility to brown rot and to elucidate the role of fruit skin against this infection, we have studied, for two consecutive seasons (2019 and 2020), the fruit susceptibility to M. fructicola, together with fruit cuticle thickness (CT) and density (CD), in a collection of 80 Spanish and 5 foreign peach cultivars from the National Peach Collection at CITA (Zaragoza, Spain). Brown rot incidence, lesion diameter, and severity index were calculated after 5 days of inoculation on non-wounded fruit. The peach collection has also been genotyped using the new peach SNP chip (9 + 9K). Genotypic and phenotypic data have been used to perform a genome-wide association analysis (GWAS). Phenotyping has shown a wide variability on the brown rot susceptibility within the Spanish germplasm as well as on CD and CT. The GWAS results have identified several significant SNPs associated with disease severity index (DSI), CD, and CT, five of which were considered as reliable SNP-trait associations. A wide protein network analysis, using 127 genes within the regions of the reliable SNPs and previously identified candidate genes (169) associated with Monilinia spp. resistance, highlighted several genes involved in classical hypersensitive response (HR), genes related to wax layers as ceramidases and lignin precursors catalyzers, and a possible role of autophagy during brown rot infection. This work adds relevant information on the complexity resistance mechanisms to brown rot infection in peach fruits and the genetics behind them.

Synergy between pre-harvest practices and storage conditions to achieve good quality nectarines and prevent brown rot losses during storage: A modeling framework

Pre- and post-harvest stages are rarely considered together in modeling studies of fruit quality and disease development, despite evident connections between these two fruit life stages in terms of underlying processes.In order to fill this gap, a new modeling framework has been introduced to simulate the effects of pre-harvest practices (irrigation regime and fruit thinning intensity) and storage conditions (temperature and relative humidity) on the development of fruit quality traits during the growing season and storage, fruit yield, and the appearance of brown rot infections during storage. The model was specifically built and calibrated for nectarine (Prunus persica var. nucipersica). A set of performance criteria was defined based on model outputs describing fruit quality (fruit size and sweetness), yield and fruit loss during storage (caused by excessive mass loss or brown rot infections). A sensitivity analysis was then carried out to study the relationships between performance criteria and pre-harvest practices and storage conditions. Finally, the model was used in combination with an optimization algorithm to retrieve the pre- and post-harvest scenarios that maximized fruit quality and quantity, aggregated into a unique performance score. This was done for different storage times and the relative importance assigned to fruit quality criteria. The results revealed that irrigation regime and thinning intensity were significant in defining fruit quality traits, while storage conditions influenced fruit loss during storage. The interactions between pre- and post-harvest conditions were also found to be important when considering the fruit loss related to brown rot infections and the fruit yield at the end of storage. The importance assigned to quality criteria largely affected the optimization outcomes. Thus, the best scenario had moderate water deficit and a low-to-medium thinning intensity when the importance of the fruit sweetness index was high, and well-irrigated regimes and very low thinning intensity when it was lower. The results also indicated a trade-off between quality criteria and, in particular, sweetness and fruit yield. The proposed modeling framework highlighted the fact that the pre- and post-harvest conditions should be considered together because they can influence both fruit quality and quantity, including fruit loss due to brown rot. The model could therefore be used as a tool to enhance dialogue between fruit supply chain actors and to identify solutions to meet their expectations.

Dose-response relationship of Ralstonia solanacearum and potato in greenhouse and in vitro experiments.

Ralstonia solanacearum is the causative agent of bacterial wilt of potato and other vegetable crops. Contaminated irrigation water contributes to the dissemination of this pathogen but the exact concentration or biological threshold to cause an infection is unknown. In two greenhouse experiments, potted potato plants (Solanum tuberosum) were exposed to a single irrigation with 50mL water (non-invasive soil-soak inoculation) containing no or 102 - 108 CFU/mL R.solanacearum. The disease response of two cultivars, Kondor and HB, were compared. Disease development was monitored over a three-month period after which stems, roots and tubers of asymptomatic plants were analyzed for latent infections. First wilting symptoms were observed 15 days post inoculation in a plant inoculated with 5x109 CFU and a mean disease index was used to monitor disease development over time. An inoculum of 5x105 CFU per pot (1.3x102 CFU/g soil) was the minimum dose required to cause wilting symptoms, while one latent infection was detected at the lowest dose of 5x102 CFU per pot (0.13 CFU/g). In a second set of experiments, stem-inoculated potato plants grown in vitro were used to investigate the dose-response relationship under optimal conditions for pathogen growth and disease development. Plants were inoculated with doses between 0.5 and 5x105 CFU/plant which resulted in visible symptoms at all doses. The results led to a dose-response model describing the relationship between R.solanacearum exposure and probability of infection or illness of potato plants. Cultivar Kondor was more susceptible to brown-rot infections than HB in greenhouse experiments while there was no significant difference between the dose-response models of both cultivars in in vitro experiments. The ED50 for infection of cv Kondor was 1.1x107 CFU. Results can be used in management strategies aimed to reduce or eliminate the risk of bacterial wilt infection when using treated water in irrigation.

Salicylic Acid and Glycyrrhizic Acid Ammonium Salt in Colloidal and Nano Forms for Management of Potato Brown Rot Infection Caused by Ralstonia solanacearum

Salicylic Acid and Glycyrrhizic Acid Ammonium Salt in Colloidal and Nano Forms for Management of Potato Brown Rot Infection Caused by Ralstonia solanacearum

Trends in agrichemical use on stonefruit orchards in New Zealand from 2004–2019

ABSTRACT Annual spray diaries from orchardists in the two main stonefruit growing regions, Central Otago and Hawke’s Bay, were analysed. The analysis was restricted to products for disease and arthropod pest control. It included apricots, cherries, nectarines, peaches and plums grown as fresh fruit for export and domestic markets, and processing crops. Mean fungicide and bactericide applications declined from 13 to 9/block/year in Central Otago, but rose from 11 to 13 sprays in Hawke’s Bay. Central Otago is drier than Hawke’s Bay and the regional spray programmes now better match the respective climates. Despite large annual variations in rainfall and numbers of brown rot (Monilinia fructicola) infection periods in both regions, there was little correlation with the numbers of fungicides applied that had activity against brown rot. The products used against diseases changed substantially during the study period. Insecticide and miticide sprays averaged 5 applications per year in Central Otago at the start of the study and declined to 4-6/crop/year (overall mean of 4) by 2018–19. Hawke’s Bay growers used 1–3 insecticide sprays per crop (overall mean of 2) throughout the study. The proportion of selective insecticides applied grew in Central Otago, but fell in Hawke’s Bay.

Genetic variability in the susceptibility of immature peach fruit to Monilinia laxa is associated with surface conductance but not stomatal density

Monilinia laxa is a fungus that causes brown rot in stone fruit. Immature green fruits in the first stage of fruit development (stage I) are generally susceptible. To investigate the relationship between the physical characteristics of immature fruit and susceptibility to M. laxa, we characterized the progeny, derived from a clone of wild peach (Prunus davidiana) crossed with two commercial nectarines (Prunus persica) varieties, through laboratory infection, transpiration monitoring and stomata counting. Two types of fruit infections were observed - ‘classic’ brown rot and ‘clear spot’ symptoms - which have not previously been described in the literature. The number and density of stomata did not explain the observed variability of infection in the progeny. However, surface conductance was positively correlated with infection level. This study provides experimental evidence partially linking physical fruit characteristics to brown rot infection at the immature fruit stage. The role of delayed cuticle deposition in susceptibility to brown rot of immature fruit is discussed.

Epidemiological Studies of Brown Rot in Spanish Cherry Orchards in the Jerte Valley.

Cherry brown rot caused by Monilinia laxa was observed and estimated in organic cherry orchard located in the Jerte Valley between 2013 and 2018 (Cáceres, Spain). Climatic variables were collected from this orchard and also from a nearby weather station. The primary inoculum of the pathogen recorded in March was detected in overwintered mummified fruits, ground mummies, and necrotic twigs and was a function of the average temperature of the previous three months (December, January, and February). The first symptoms of brown rot could be observed on flowers until fruit set in April. The months of March and April were identified as the critical period for cherry brown-rot development. A significant positive correlation was identified between brown rot observed at harvest and the mean number of consecutive days in each fortnight of March and April when the percent relative humidity was above 80%. Brown-rot incidence observed over the 6 years ranged from 0 to 38%. More than 11 days with relative humidity >80% in each fortnight of critical period would mean 100% of cherry brown rot at harvest. A forecasting model could be used to predict brown rot infection in Jerte Valley cherries.

Genome-Wide Association Study of Brown Rot (Monilinia spp.) Tolerance in Peach.

Brown rot, caused by Monilinia spp., is one of the most important diseases on stone fruit worldwide. Severe yield loss can be caused by pre- and post-harvest fruit decay. Although some degree of tolerance has been reported in peach and almond, the genetic resistance in peach cultivars is still lacking. To date, only few genomic regions associated with brown rot response in fruit skin and flesh have been detected in peach. Previous studies suggested brown rot tolerance in peach being a polygenic quantitative trait. More information is needed to uncover the genetics behind brown rot tolerance in peach. To identify the genomic regions in peach associated with this trait, 26 cultivars and progeny from 9 crosses with ‘Bolinha’ sources of tolerance, were phenotyped across two seasons (2015 and 2016) for brown rot disease severity index in wounded and non-wounded fruits and genotyped using a newly developed 9+9K peach SNP array. Genome wide association study using single- and multi-locus methods by GAPIT version 3, mrMLM 4.0, GAPIT and G Model, revealed 14 reliable SNPs significantly associated with brown rot infection responses in peach skin (10) and flesh (4) across whole genome except for chromosome 3. Candidate gene analysis within the haplotype regions of the detected markers identified 25 predicted genes associated with pathogen infection response/resistance. Results presented here facilitate further understanding of genetics behind brown rot tolerance in peach and provide an important foundation for DNA-assisted breeding.

RESEARCHES ON MONITORING AND EARLY WARNING OF BROWN ROT MONILIA LAXA ATTACK ON SOME VARIETIES OF CHERRY AND PLUM

Brown rot caused by Monilia laxa (Aderh. & Ruhland, Honey) is one of the most damaging fungal disease for stone fruit species, in all European countries and in Romania as well. A great deal effort is done to study its biology and ecology, for disease monitoring and containment. This paper presents the result obtained at RIFG Pitesti Romania during 2018-2020 in monitoring and early warning of the disease attack, using two different weather stations and forecast modules made in Europe and USA. A correlation was found (R2=0.0146, r=0.1208, n=585), which proves that the microclimate was favorable for stone fruits brown rot infections, for varieties evaluation and classification and to supply data to develop new early warning tools as well. The results obtained with the two forecast systems makes possible the early warning on the attack risk of brown rot, both cherry and plum orchards. In the same period 26 cherry and 22 plum varieties were studied regarding their behavior to the pathogen natural infections. Among the Romanian varieties the ones with the lowest damages degree were: 'George', 'Clasic', 'Daria', 'Negre de Bistriţa', 'Roşii de Bistriţa', 'Rubin', 'Severin' and 'Uriaşe de Bistriţa' (DD%=0.13-0.14) on cherry and 'Pescaruş' 'Record', 'Gras ameliorat', 'Romanţa', 'Roman, 'Ialomiţa' and 'Dâmboviţa' (DD%=0.03-0.14) on plum. Under long term study, the most sensitives to brown rot attack were 'Lapins' cherry variety (DD%=3.93) as well as 'Stanley' Centenar and 'd’Agen' plum varieties (DD%=4.68-4.72), which can be used as 'indicators', in order to triggers the phytoprotection programs.

Efficacy of PCR-bassed techniqes and remote sensing technology for detecting potato brown rot infection caused by R. solanacearum

Bacterial wilt of potatoes (Solanum tuberosum) caused by Ralstonia solanacearum phylotype II sequevar I (race 3 biovar 2), is one of the most serious diseases of potatoes. This study aimed to detect such deteriorations through the remotely sensed data. In this regard, naturally infested potato fields at Abo Alkhawi, Al Tayareya and Om Saber villages at Behera governorate, Egypt, were used for selective isolation of R. solanacearum. On Semi Selective South Africa (SMSA) medium, 30 isolates were randomly screened and tested by immunofluorescence antibody staining (IFAS) and confirmed biologically by tomato plantlets (cv. Pinto) reaction. All isolates showed positive results with Real-time PCR. Based on the phylotype specific multiplex (Pmx) – PCR data, all isolates in concern were R. solanacearum and affiliated to phylotype II as 372- bp amplicon. Spectral indices were applied on the Landsat 8 and RapidEye satellite images acquired in January and April 2019 including Normalized Difference Moisture Index (NDMI), Normalized Difference Vegetation Index (NDVI), Normalized Difference Salinity Index (NDSI) and Modified Chlorophyll Absorption Ratio Index (MCARI). Results from the remote sensing analyses showed medium to relatively high salinity and moisture content of soils concerened. Moreover, plants chlorophyll levels are in medium levels which is not typical to condition associated with usual circumstances. Further investigation, in a greater academic depth, are needed for pathological field surveys.

Balance between resilient fruit surface microbial community and population of Monilinia spp. after biopesticide field applications of Penicillium frequentans

The microbial variability on the host plant surface must be maintained because population diversity and quantity are essential to avoid disease development. It would be necessary to examine the patterns and mechanisms associated with the massive and reiterative introduction of a microbial pest control agent. The effect of inundative releases of biopesticide formulations containing Penicillium frequentans for the control of Monilinia spp. populations, and the effect on fruit surface microbiota on 18 stone fruit field experiments located in four European countries for more than two crop seasons against brown rot were studied. P. frequentans was monitored after application in order to assess whether it was persistent or not in the environment. Hydrolysis of fluorescein diacetate and denaturing gradient gel electrophoresis were used to study the effects of P. frequentans on fungal and bacterial non-target populations on fruit surface. The effect of P. frequentans formulations on the populations of Monilinia spp. on fruit was also assessed in different orchards. P. frequentans population on stone fruit surfaces showed ranged from 100 to 10,000 CFU cm−2, and postharvest recovered populations were more than 10–100-fold higher than preharvest recovered populations. The population of P. frequentans varied among orchards and years, rather than by the type of formulation. P. frequentans formulation reduced Monilinia spp. population and brown rot and latent infections caused by this pathogen both before and at harvest, while stabilizing or increasing antagonist populations and avoiding non-target microorganisms. However, fungicides reduced significantly the microbial activity on nectarine surfaces.

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.

Detection of Latent Monilinia Infections in Nectarine Flowers and Fruit by qPCR.

Most stone fruit with a latent brown rot infection caused by Monilinia do not develop visible signs of disease until the arrival of fruit at the markets or the consumer's homes. The overnight freezing-incubation technique (ONFIT) is a well-established method for detecting latent brown rot infections, but it takes between 7 to 9 days. In this report, we inform on the advantages of applying a qPCR-based method to (i) detect a latent brown rot infection in the blossoms and fruit of nectarine trees (Prunus persica var. nucipersica) and (ii) distinguish between the Monilinia spp. in them. For applying this qPCR-based method, artificial latent infections were established in nectarine flowers and fruit using 10 Monilinia fructicola isolates, 8 M. fructigena isolates, and 10 M. laxa isolates. We detected greater amounts of M. fructicola DNA than M. laxa and M. fructigena DNA in latently infected flowers using qPCR. However, greater DNA amounts of M. laxa than M. fructicola were detected in the mesocarp of latently infected nectarines. We found that the qPCR-based method is more sensitive, reliable, and quicker than ONFIT for detecting a latent brown rot infection, and could be very useful in those countries where Monilinia spp. are classified as quarantine pathogens.

Application of a Bayesian ordinal animal model for the estimation of breeding values for the resistance to Monilinia fruticola (G.Winter) Honey in progenies of peach [Prunus persica (L.) Batsch

Fruit brown rot caused by Monilinia spp. is the most important fungal disease of stone fruits worldwide. Several phenotyping protocols to accurately characterize and evaluate brown rot infection have been proposed; however, the outcomes from those studies have not led to consistent advances in resistance breeding programs. Breeding for disease resistance is one of the most challenging objectives for crop improvement because disease expression is tetrahedral: it is simultaneously influenced by agent, host, environment, and human management. The present study presents a strategy based on Bayesian inference to analyze a peach breeding progeny for resistance to brown rot, evaluated using a polytomous ordinal scale. A pedigree containing two sources of resistance, one from peach and the other from almond, several commercial cultivars, and two segregating populations were analyzed to estimate the narrow-sense heritability (h2) and breeding values (EBVs) for brown rot resistance in progenies. Results show promise for genetic improvement of disease resistance and other traits characterized by strong environmental interactions.

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.

Comparative in vivo and in vitro study on Monilia fructicola causing brown rot of stone fruit in Brazil and California

Stone fruit production plays an important economical role in southern Brazil as well as in California, United States. In both countries, brown rot caused by Monilinia fructicola is the most important stone fruit disease, responsible for significant pre- and post-harvest fruit losses. The United States is among the main importers of stone fruit to Brazil. Imported fruit carrying the pathogen may introduce isolates with greater ability to infect stone fruit orchards in Brazil. In this study, 26 M. fructicola isolates from Brazil and California, recovered from commercial stone fruit orchards, were randomly selected and compared based on in vitro (optimum growth temperature, mycelial growth rate, germination, spore production and germ tube rate) and in vivo (sporulation, area under disease progress curve, incubation and latent period) studies on brown rot infection components. The isolates behaved similarly for most of the studied variables, except for germ tube length and sporulation on fruit, which were higher in isolates from California and Brazil, respectively. The negative correlation between these variables may be disadvantage for isolates from California to cause infections in the main peach cultivar grown in South Brazil. Significant differences in incubation and latent period and the area under disease progress curve were found among isolates from a same country. Such differences may be due to intraspecific diversity associated with the occurrence of the perfect stage in California, and by the broad sampling area from where isolates from Brazil were obtained. It is still difficult to determine the effect of isolates arising from imported California fruits in Brazilian stone fruit orchards. Further genetic variability studies and comparative epidemiology in the field may help to understant the real threat that foreign isolates represent.

Assessment of pathogenicity and infection requirements of Monilinia species causing brown rot of stone fruit in Australian orchards

This study investigated the effect of wetness duration on blossom blight development and the effects of Monilinia species, wetness duration, temperature and wounding on brown rot development in detached fresh market stone fruit. Both Monilinia fructicola and M. laxa infected ripe peach (cv. Autumn snow), nectarine (cv. Arctic snow) and apricot (cv. Robada), but M. laxa caused lower incidence of infection and no infection on plums (cv. Su Plum 11). Short wetness durations (2, 4 or 6 h at 15 and 20 °C) were sufficient for infection of ripe peach, plum, apricot and nectarine by M. fructicola, but on young fruit (5 weeks after full bloom) only peach and nectarine were infected at similar wetness durations at 5, 10, 15, 20 and 25 °C. Infection of young nectarine and ripe apricot and plum fruit was influenced by the wetness duration, and infection of ripe apricot by temperature. Under longer wetness durations (12 and 24 h at 15 and 20 °C), the susceptibility of the four fruits to M. fructicola was affected by fruit maturity. Nectarine and peach were more susceptible when ripe than as young fruit and least susceptible at pit hardening. Plum and apricot were also more susceptible when ripe than as young fruit. Infection of wounded fruits by both Monilinia species was 100 % in the four fruits tested at both immature and mature stages. In controlled field inoculations, M. fructicola infected peach flowers after 3 h wetness duration at 24 °C and thereafter blossom blight incidence increased with longer wetness duration (5, 8 and 20 h) at temperatures ranging from 16 to 24 °C. The results will be used to improve prediction of brown rot infection risk in stone fruit production in Australia.

Disease warning models for brown rot fungi of fruit crops

In this review, disease warning models for brown rot fungi, including Monilinia fructigena, M. laxa and M. fructicola, were summarized. Few studies have been made to relate epidemiology and disease warning in brown rot infection caused by M. fructicola and M. laxa in order to predict infections or develop decision support models for fungicide applications during the growing season. More recently a disease warning model and a decision support system were also performed for M. fructigena for organic apple orchards. This review gives an overview on some details of the above disease warning models and decision support system.

Influence of preharvest calcium applications, fruit injury, and storage atmospheres on postharvest brown rot of apple

In a three year study, the effect of preharvest calcium applications on postharvest losses of apple fruit (cultivar ‘Idared’) caused by Monilinia fructigena was evaluated in fruit under air storage, controlled atmosphere (CA), and ultra low oxygen (ULO) conditions. Injured and noninjured fruit were used and storage was at 1°C for all three storage conditions. In addition, temporal dynamics of postharvest brown rot development were assessed monthly over four months storage and the spread of brown rot infection amongst fruit was assessed at the final assessment date. For all years, disease development, final brown rot incidence and the area under curves of disease progress were lower amongst calcium-treated than in the nontreated controls (mean values of 3.6 and 11.1%, respectively). CA and ULO treatments reduced rot incidence (mean values of 12.4, 6.3, and 0.7%, for air, CA and ULO fruit respectively). In addition, with regard to injury–inoculation combinations, final brown rot incidence increased in the order noninjured–noninoculated, noninjured–inoculated, injured–noninoculated and injured–inoculated treatments (mean values of 3.6, 5.0, 7.3, and 11.4%, respectively). The number of infected fruit was generally higher in the first layer of neighbouring fruit in storage boxes than in the second one. Calcium treatment significantly reduced the number of infected fruit both in the first and second layers compared to the controls (mean values of 45.5 and 75, respectively). CA and ULO treatments also reduced the number of infected fruit both in the first and second layers of neighbouring fruit (mean values of 94, 69.5, and 10.5, for air, CA and ULO respectively). With regard to injury treatments, the number of infected fruit increased in both the first and second layers of neighbouring fruit in the order of noninjured–inoculated and injured–inoculated treatments (mean values of 51.5 and 75.5, respectively). This study suggests that integration of preharvest calcium applications and CA storage, along with minimization of fruit injury/infection, may reduce brown rot incidence during long term storage.

Postharvest biocontrol of Monilinia laxa, Monilinia fructicola and Monilinia fructigena on stone fruit by two Aureobasidium pullulans strains

The antagonistic effects of yeasts, L1 and L8, isolated from carposphere of ‘Redhaven’ peaches were tested for the first time in the same experiment against three Monilinia species (Monilinia laxa, Monilinia fructicola and Monilinia fructigena) in in vitro and in vivo trials. The two antagonists were selected after preliminary assays for their ability to reduce brown rot in peaches and nectarines, and both were identified by molecular and morphological tools as Aureobasidium pullulans. In in vivo trials, neither the autoclaved cells, nor the sterile culture filtrates of either antagonist showed any significant reduction of rot incidence produced by inocula of the three Monilinia species, while the washed cells of L1 and L8 completely inhibited M. laxa and M.fructicola rots and reduced M. fructigena infections by 70% and 90%, respectively. In other trials, nectarines treated with antagonist cells and inoculated with the pathogens were stored at 0°C for 21days, plus 7days at 20°C. The low temperature reduced brown rot development, since all fruit were free from disease symptoms on removal from cold storage. However after 7d at 20°C, untreated fruit were rotted over 45% depending on the Monilinia species but the antagonists completely inhibited M. laxa and M. fructicola, while M. fructigena infections were reduced by 89.8% and 91.2% by L1 and L8, respectively. For both strains, 108CFUml−1 was the most active concentration, although L1 showed good activity at a concentration of 107CFUml−1. Isolate L8 at the concentration of 107CFUml−1 was ineffective against M. fructicola and M. fructigena, showing no difference between treated fruit and the control, excepting the case of nectarines inoculated with M. laxa, where L8 at the concentration of 107CFUml−1 reduced the brown rot infections with respect to the control. The increase in population density of A. pullulans strains L1 and L8 in the wounds of nectarines stored at 0° or 20°C was low but sufficient to control brown rot. In conclusion, the present preliminary study identified two antagonistic strains of A. pullulans as active ingredients for the development of biofungicides for postharvest application against three Monilinia species that are responsible for high economic losses in stone fruit crops.