Peach Brown Rot Research Articles

Candida pruni sp. nov. is a new yeast species with antagonistic potential against brown rot of peaches.

Brown rot caused by Monilinia spp. is among the most important postharvest diseases of commercially grown stone fruits, and application of antagonistic yeasts to control brown rot is one promising strategy alternative to chemical fungicides. In this research, new yeast strains were isolated and tested for their activity against peach brown rot caused by Monilinia fructicola. Three yeast strains were originally isolated from the surface of plums (cv Chinese Angelino) collected in the north of China. In artificially wounded inoculation tests, the yeast reduced the brown rot incidence to 20 %. The population of the yeast within inoculated wounds on peaches significantly increased at 25 °C from an initial level of 5.0×10(6) to 4.45×10(7) CFU per wound after 1 day. The antagonistic strains were belonging to a new species of the genus Candida by sequence comparisons of 26 S rDNA D1/D2 domain and internal transcribed spacer region. The strains are most closely related to C. asparagi, C. musae and C. fructus on the basis of the phylogenetic trees based on the D1/D2 region of 26S rDNA. However, the strains are notably different from C. asparagi, C. musae and C. fructus, in morphological and physiological characteristics. Therefore, the name Candida pruni is proposed for the novel species, with sp-Quan (=CBS12814T=KCTC 27526T=GCMC 6582T) as the type strain. Our study showed that Candida pruni is a novel yeast species with potential biocontrol against brown rot caused by M. fructicola on peaches.

Influence of hot water treatment on brown rot of peach and rapid fruit response to heat stress

Recent results on hot water as an alternative treatment open a new perspective in disease incidence reduction. In the present work peach fruit were wounded, inoculated with conidia of Monilinia laxa and 15min, 3, 6, 12, 24 and 48h after inoculation treated by dipping in hot water (HT) at 60°C for 20s. The effect of heat treatment on some cell wall genes involved in ripening such as β-galactosidase (β-GAL), pectin lyase (PL), polygalacturonase (PG) and pectin methyl esterase (PME), was analyzed by qRT-PCR. The expression levels of defense related genes, phenylalanine ammonia lyase (PAL) and chitinase (CHI), heat stress-related genes such as heat shock proteins 70 and 90 (HSP70, HSP90), and reactive oxygen species (ROS) scavenging genes were also evaluated by qRT-PCR. A 100% disease incidence reduction, as compared to untreated fruit, was obtained by treating 6 and 12h after inoculation. Moreover, brown rot was inhibited by 85.7% when fruit were heat-treated 48h after inoculation. The expression levels of cell wall genes (β-GAL, PL, PG and PME) showed a general decrease in HT fruit as compared to the control, whereas PAL, CHI, HSP70 and ROS-scavenging genes increased their expression level in HT samples with respect to the untreated ones. Our results show a curative activity of heat on peach inoculated with M. laxa 48h before treatment. Each analyzed gene proved to be differentially expressed following heat treatment.

Vegetative compatibility groups and sexual reproduction among Spanish Monilinia fructicola isolates obtained from peach and nectarine orchards, but not Monilinia laxa

The frequency of occurrence of Monilinia fructicola in the Ebro Valley, Spain has increased since its first appearance in 2006, and M. fructicola has displaced Monilinia laxa, the native species which is the main cause of brown rot in peaches in this valley. In order to determine the characteristics that may be related to the displacement, we studied the capacity to generate new genotypic combinations of M. fructicola under laboratory conditions. The morphology and parasitic ability from ten field isolates of M. fructicola and M. laxa collected from three different orchards in the valley, and sampling from five different lesions were studied. Nitrate-non-utilising (nit) mutants were generated in order to test the isolates for vegetative compatibility which was done by assessing their colony growth when cultured singly or in pairs on media that contained different nitrogen sources. For the M. fructicola isolates, five vegetative compatibility groups (VCGs) were identified using the nit mutants and six VCGs were identified when they were grown on potato dextrose agar dishes. In all instances, the vegetatively compatible M. fructicola isolates came mainly from the same orchard. Only one VCG displays the same morphological and competition characteristics. No VCGs were identified among the M. laxa isolates. We did not find any apothecia of M. laxa and M. fructicola isolates in the soil of the three orchards, but we were able to produce apothecia of M. fructicola in the laboratory. Our finding of sexual reproduction and VCGs in the M. fructicola isolates suggests that the genetic variability of M. fructicola could be maintained by sexual and/or parasexual recombination.

Eradicant and curative treatments of hexanal against peach brown rot

Brown rot, caused by Monilinia spp. , is one of the most important peach (Prunuspersica (L.) Batsch) diseases and the main cause of postharvest losses. Currently, alternative methods for postharvest disease control, such as the use of volatiles, are under investigation. The objective of this study was to determine the effects of hexanal on the in vitro development of Monilinia fructicola and M. laxa and on monocyclic components of brown rot on peaches. To evaluate the effect on pathogen development in vitro, a single dose of 215 µL of liquid hexanal was placed on glass jars in closed plastic containers (4.3 L) at the moment of fungi transfer, 24 or 48 h after transferring to Petri dishes. After hexanal application, the Petri dishes were kept inside the containers that were closed for 24 h at 20 ºC. Mycelial growth was measured seven days after hexanal removal. For in vivo assays, inoculated fruits were kept in closed plastic containers, and hexanal was applied at the moment of fruit inoculation or 24 hours thereafter. The monocyclic components infection frequency, expressed as brown rot incidence, lesion diameter and lesion sporulation, were assessed daily for seven days. Overall, hexanal was more effective in inhibiting mycelial growth when applied at the moment of pathogen transfer. Hexanal did not prevent pathogen infection, but reduced lesion diameter and completely inhibited spore production on the fruit for both treatments. Hexanal provides a promising alternative for chemical control and can be used in postharvest handling systems.

Foliar Calcium Applications for Controlling Fruit Disorders and Storage Life in Deciduous Fruit Trees

Calcium is involved in several disorders and influences the storage life of different fruit species. Moreover, applying preharvest foliar Ca spray is a standard practice to control fruit Ca concentration in certain deciduous fruit trees. Conversely, the effects of foliar Ca spray on the Ca concentration in fruit and the incidence of disorder are sometimes inconsistent. This article provides an overview of recent works on foliar Ca application and discusses Ca application inconsistencies. Foliar Ca sprays reduced bitter pit, enhanced fruit firmness and storage time, and sometimes reduced the incidence of brown rot during storage in apples; reduced internal browning during storage and the incidence of brown rot in peaches; decreased postharvest decay and cork spot in pears; and increased shelf life in grapes. Experiments using 45 Ca or isolated cuticular revealed the effects of fruit growth stages, atmospheric conditions, and adjuvants on Ca penetration. Finally, three possible reasons for inconsistencies of foliar Ca application are discussed.

Occurrence of Monilinia laxa and M. fructigena after introduction of M. fructicola in peach orchards in Spain

Seventeen field surveys were done in four commercial orchards during six consecutive fruit-growing seasons from 2006 until 2011 in order to determine the current frequencies of occurrence of M. laxa, M. fructigena, and M. fructicola and their relative contributions to postharvest brown rot in peaches and nectarines in the Ebro Valley. The relative frequencies of occurrence of Monilinia spp. were determined on three sources of primary inoculum and on three sources of secondary inoculum. The major relative frequencies of Monilinia spp. were significantly recorded (P = 0.05) from mummified fruit on the trees (approx. 42 %) and 7-day-old harvested fruit with brown rot (32 %), followed by that recovered from mummified fruit on the orchard bed (14 %), pruned branches on the orchard bed (8 %) and latent infections of immature fruit (3 %). We found that: (a) the relative frequency of M. fructicola has increased over the years to coexist on the same level as at the time M. laxa, (b) M. fructigena is no longer a cause of brown rot in harvested peaches, (c), a progressive reduction in the time of the first appearance of Monilinia airborne conidia (r = −0.30, P = 0.003), and the time of the first latent infection (r = −0.44, P = 0.0001) was detected along years after correlation analysis, and (d) these displacements are not associated with an increased incidence of brown rot disease. The M. fructicola increase was due to its significantly increased presence in 7-day-old harvested fruit with brown rot (r = 0.73, P = 0.0009), in latent infections of immature fruit (r = 0.68, P = 0.002), on pruned branches on the orchard bed (r = 0.56, P = 0.018), and on mummified fruit sampled on the trees (r = 0.53, P = 0.03). This progressive increase was accompanied by a progressive reduction in the relative frequency of occurrence of M. laxa in 7-day-old harvested fruit with brown rot (r = −0.55, P = 0.021) and M. fructigena on mummified fruit sampled on the trees (r = −0.51, P = 0.03).

First Report of Peach Brown Rot Caused by Monilinia fructicola in Central and Western China.

Brown rot of peach (Prunus persica) in China has been reported to be caused by at least three Monilinia species (1). In the present study, peaches with symptoms resembling brown rot caused by Monilinia species were collected from commercial orchards in the northwestern province of Gansu in August 2010, the southwestern province of Yunnan in July 2011, and in the central province of Hubei in July 2012. Affected fruit showed the typical symptoms of brown rot with zones of sporulation. Fungal isolates were single-spored and cultured on potato dextrose agar (PDA). Colonies showed grayness with concentric rings of sporulation after incubation at 25°C in the dark. Mean mycelial growth of isolates YHC11-1a and YHC11-2a from Yunnan, GTC10-1a and GTC10-2a from Gansu, and HWC12-14a and HWC12-23a from Hubei, was 4.6 ± 0.4 and 7.5 ± 0.7 cm after 3 and 5 days incubation, respectively. Conidia were lemon shaped and formed in branched monilioid chains, and the mean size was 9.3 (6.7 to 11.5) × 12.5 (7.9 to 17.8) μm, which was consistent with the characteristics of Monilinia fructicola (1,2). The species identification was confirmed by sequencing of the ribosomal ITS sequences. The ribosomal ITS1-5.8S-ITS2 region was amplified from each of the six isolates using primers ITS1 and ITS4 (3). Results indicated that the ITS sequences of these isolates were identical and showed the highest similarity (100%) with M. fructicola ITS sequences from isolates collected in China (GenBank Accession Nos. HQ893748, FJ515894, and AM887528), Slovenia (GU967379), Italy (FJ411109), and Spain (EF207423). The pathogen was also confirmed to be M. fructicola based on the detection of an M. fructicola- specific band (534 bp) using a PCR-based molecular tool developed for distinguishing Chinese Monilinia species affecting peach (1). Pathogenicity was tested on surface-sterilized, mature peaches (Shui Mi Tao) with representative isolates. Fruits were holed at three equidistant positions to a depth of 5 mm using a sterile cork borer. Mycelial plugs (5 mm in diameter) from the periphery of a 4-day-old colony of each isolate were placed upside down into each hole, control fruits received water agar. After 3 days of incubation at 22°C in a moist chamber, inoculated fruits developed typical brown rot symptoms while control fruits remained healthy. Pathogens from the inoculated fruit were confirmed to be M. fructicola based on morphological characteristics. To our knowledge, this is the first report of occurrence of M. fructicola in Gansu, Yunnan, and Hubei provinces, thousands of kilometers away from eastern China where occurrence of peach brown rot caused by M. fructicola has been confirmed (2,4). The results indicated the further geographical spread of the M. fructicola in China.

Baseline sensitivity of Monilia yunnanensis to the DMI fungicides tebuconazole and triadimefon

Monilia yunnanensis was recently identified as a new species causing brown rot of peach in China. Sterol 14α-demethylase inhibitors (DMIs) continue to be important in the management of brown rot of Monilinia spp. worldwide. Tebuconazole and triadimefon are two kinds of DMI fungicides that may be used for brown rot control in China. To establish the baseline sensitivity of M. yunnanensis to these two DMI fungicides, 203 M. yunnanensis single spore isolates were collected. Measurements of sensitivity to the two fungicides were based on inhibition of mycelial growth. For both fungicides, the sensitivity distribution was a unimodal curve, with an EC50 range (the effective concentration to inhibit mycelial growth by 50 %) of 0.0001–0.0644 μg/ml for tebuconazole and 0.2311–1.7477 μg/ml for triadimefon. The M. yunnanensis isolates were obtained from orchards where DMI fungicides have not been used for peach brown rot control, thus the fungicide sensitivity distribution established in this study can be considered as the baseline for monitoring the resistance development in M. yunnanensis once the DMI fungicides are used to control peach brown rot.

Immersion of fruit in water to improve radio frequency treatment to control brown rot in stone fruit

Brown rot caused by Monilinia spp. is the most important postharvest disease of stone fruit. Currently, no chemical fungicides are allowed in the European Union to be applied to stone fruit after harvest, which has increased the need to develop alternative methods. Radio frequency (RF) treatment at 27.12MHz with fruit immersed in water was studied to control brown rot in peaches and nectarines artificially inoculated with M. fructicola. Additionally, RF treatment in air was also investigated to evaluate the benefit of water immersion to reduce the effect of fruit size on treatment efficacy. RF treatment with fruit immersed in water at 20°C applied for 9min significantly reduced brown rot incidence in both peaches and nectarines and no significant differences in RF efficacy were observed depending on fruit size. However, when RF treatment was applied in air for 18min, brown rot reduction was significantly higher in large fruit than in small fruit. Finally, the decrease in exposure time of radio frequency treatment with fruit immersed in water with increasing water temperature was also studied. Reduction of treatment time to 6 and 4.5min was achieved by increasing water temperature at 35 and 40°C, respectively, to control brown rot without adverse external and internal damage in both ‘Baby Gold 9’ peaches and ‘Autumn Free’ nectarines.

Potassium, calcium and copper phosphite to control peach rust and brown rot

The phosphites have been recommended as plant protectors and inducers of host resistance against diseases. Three phosphite formulations (copper, potassium and calcium) were evaluated to control peach rust (Tranzschelia discolor) and brown rot (Monilinia fructicola), in an orchard with two cultivars: 'Chimarrita' and 'BR-1'. The phosphite treatments were applied out every 30 days from September to December. The incidence and severity of leaf rust were evaluated from November to January. The fruits were harvest and assessed to brown rot incidence after three and five days. The copper phosphite reduced the rust severity in 34.8% for 'Chimarrita'. No phosphite formulation was efficient to control brown rot in the condition of the experiment. The cultivar 'Chimarrita' was more susceptible than 'BR1' in the evaluated diseases

Disease control during peach preservation with a berberine-chitosan composite membrane

Introduction. Peach brown rot caused by the fungus Monilinia fructicola is a major disease leading to considerable economic loss during storage. Our previous study unco- vered the striking inhibition of the natural alkaloid berberine against M. fructicola. Materials and methods. A berberine-chitosan composite membrane (BCCM) able to slowly release ber- berine was prepared and used for peach preservation. The examined fruits were stored at 4 °C and treated as follows: (I) control fruits without packaging; (ii) fruits that were transiently immer- sed in pre-solidified BCCM liquid and taken out; (iii) fruit coating either with a BCCM, or with amembranecontainingchitosanonly(withoutberberine),and(iv)fruitcoatingwithaPVCmem- brane. Results and discussion. The group immersed in BCCM showed a high infection rate due to the cytotoxicity of acetic acid, but the coating group showed only a 10% infection rate after 40 days of storage. Moreover, the BCCM-coating group showed a significantly lower infec- tion rate than that coated with chitosan membrane (without berberine), clearly indicating the antimicrobial activity of berberine therein. Consequently, packed in BCCM and stored at 4 °C, peach fruits could be well preserved over 40 days with very low infection. Conclusion. Consi- dering its safety and low cost, the berberine-containing chitosan composite membrane could be applicable in controlling diseases during peach storage. China / Prunus persica / peaches / storage / disease control / Monilinia fructicola / postharvest technology / coating / membranes

Formulation development of the biocontrol agent Bacillus subtilis strain CPA-8 by spray-drying

To prepare commercially acceptable formulations of Bacillus subtilis CPA-8 by spray-drying with long storage life and retained efficacy to control peach and nectarine brown rot caused by Monilinia spp. CPA-8 24-h- and 72-h-old cultures were spray dried using 10% skimmed milk, 10% skimmed milk plus 10% MgSO(4) , 10% MgSO(4) and 20% MgSO(4) as carriers/protectants. All carriers/protectants gave good percentages of powder recovery (28-38%) and moisture content (7-13%). CPA-8 survival varied considerably among spray-dried 24-h- and 72-h-old cultures. Seventy-two hours culture spray dried formulations showed the highest survival (28-32%) with final concentration products of 1·6-3·3 × 10(9) CFU g(-1) , while viability of 24-h-old formulations was lower than 1%. Spray-dried 72-h-old formulations were selected to subsequent evaluation. Rehydration of cells with water provided a good recovery of CPA-8 dried cells, similar to other complex rehydration media tested. Spray-dried formulations stored at 4 ± 1 and 20 ± 1°C showed good shelf life during 6 months, and viability was maintained or slightly decreased by 0·2-0·3-log. CPA-8 formulations after 4- and 6 months storage were effective in controlling brown rot caused by Monilinia spp. on nectarines and peaches resulting in a 90-100% reduction in disease incidence. Stable and effective formulations of biocontrol agent B. subtilis CPA-8 could be obtained by spray-drying. New shelf-stable and effective formulations of a biocontrol agent have been obtained by spray-drying to control brown rot on peach.

Secondary inoculum dynamics of Monilinia spp. and relationship to the incidence of postharvest brown rot in peaches and the weather conditions during the growing season

Eight field surveys over three growing seasons (April to October in 2006, 2007, and 2008) were done in three commercial peach and nectarine orchards in order to determine the secondary inoculum dynamics of Monilinia spp. and relationship to the weather conditions and incidence of postharvest brown rot in the Ebro Valley, which is the main peach fruit growing region in Spain. After regression analysis of the epidemiological data of postharvest brown rot and the climatic variables, a disease outbreak can be predicted from (i) the times of the first appearance of airborne conidia, the first appearance of conidia on the surface of flowers and fruits, and the first latent infection, all of which occur 2 months before harvest (ii) the number of conidia on the fruit surface, 2 weeks and 1 week before harvest, (iii) the preharvest incidence of brown rot, and (iv) the mean environmental temperature from popcorn to harvest. From these results, we confirmed the importance of the secondary inoculum dynamics of Monilinia spp. and the utility of these dynamics to predict an outbreak of brown rot in peaches on the day of their harvest and after their harvesting.

Optimization of parameters of the ‘Virtual Fruit’ model to design peach genotype for sustainable production systems

Designing sustainable production systems that are respectful of the environment and produce safe food of quality is a challenge for the future. A critical step is to find the best combinations of genetic resources and cultural practices adapted to target environments. The objective of this work is to illustrate how an ecophysiological process-based simulation model could be possibly used to design genotypes and to propose innovative production systems, by applying a methodology of optimization.As example, we studied the peach-brown rot system and used the ‘Virtual Fruit’, a process-based model that has been extensively tested, to perform virtual experiments. The challenge was to optimize the trade-off between antagonistic criteria of major importance for both fruit quality (increasing fruit mass and sweetness) and sensitivity to brown rot (decreasing skin density of cracks) in four different cultural scenarios. A multiobjective evolutionary algorithm, namely NSGA-II, was applied to solve this multiobjective optimization problem based on the ‘Virtual Fruit’. The optimized variables were six parameters of the ‘Virtual Fruit’, selected on the basis of a sensitivity analysis.This optimization method provided a large diversity of solutions among which the decision-maker can choose the best suited trade-off between criteria according to a particular objective. Most of the optimized solutions were distributed along Pareto fronts suggesting a good convergence of the algorithm. Moreover, it also provided some solutions located in non-crowded zones which constitute some original alternatives for the final decision-maker.The results confirmed the strong antagonism between the criteria considered. Large fruits had a weak sweetness and high crack density and for a given mass, those with improved sweetness had higher crack density. In a current breeding scheme, fruit mass would be the only criteria considered but alternative schemes could be considered for future, favouring organoleptic quality or environment friendly practices. In those cases, some interesting optimized solutions were identified.The work described in this paper supports that multiobjective evolutionary algorithms should be used to optimize parameters of process-based models and help identifying trade-off in complex systems. The use of the ‘Virtual Fruit’ to design sustainable production systems combining genotypes and innovative practices is further discussed.

Effect of heat treatment on inhibition of Monilinia fructicola and induction of disease resistance in peach fruit

Heat treatment (wet and dry) of fruit has been demonstrated as an effective approach for managing postharvest decay. Both direct antimicrobial effects on pathogen propagules as well as induction of host defense mechanisms have been suggested to play a role in the observed reduction of decay. In the present study, the effect of heat treatment (HT, hot water treatment at 40 °C for 5 and 10 min) on Monilinia fructicola and/or peach brown rot was investigated. HT inhibited spore germination and germ tube elongation of M. fructicola in vitro. HT also triggered the accumulation of reactive oxygen species (ROS), collapse of mitochondrial membrane potential and a decrease in intracellular ATP in M. fructicola. Results of the studies on peach fruit showed that HT induced the expression of defense-related genes including chitinase ( CHI), β-1, 3-glucanase ( GNS) and phenylalanine ammonia lyase ( PAL), as well as increased the activity of these enzymes in peach fruit. The HT used in this study did not appear to impair fruit quality. Our results indicate that both the direct inhibition of M. fructicola and the elicitation of defense responses in fruit by HT contribute to the observed reduction of decay in peach fruit.

Biological control of peach brown rot (Monilinia spp.) by Bacillus subtilis CPA-8 is based on production of fengycin-like lipopeptides

Bacillus subtilis CPA-8, a strain with demonstrated ability to control Monilinia spp. in peaches, was studied to elucidate its mechanisms of antifungal activity. Growth inhibition assays using cell-free supernatants and butanolic extracts showed strong antifungal activities against Monilinia laxa and Monilinia fructicola. By comparison with the reference B. subtilis strains UMAF6614 and UMAF6639, fengycin, iturin and surfactin lipopeptides were identified by thin layer chromatography in butanolic extracts from cell-free supernatants, indicating that antibiosis could be a major factor involved in the biological control ability of CPA-8. TLC-bioautography analysis confirmed the presence of fengycin, iturin and surfactin lipopeptides but strong antifungal activity could be associated only with fengycin lipopeptides. These results were definitively supported by mutagenesis analysis targeted to suppress fengycin biosynthesis by disruption of the B. subtilis fenB gene. By TLC-bioautography analysis it was possible to identify transformants from CPA-8 with reduced or suppressed antifungal activity, and this phenotype was associated with the lack of fengycin bands. Fruit trials confirmed that fengycin-defective mutants and their cell-free supernatants lost their ability to control peach brown rot disease in comparison with CPA-8 wild type strain or Serenade Max®, a commercial formulation based on B. subtilis. Furthermore, population dynamics studies determined that CPA-8 fengycin-deficient mutants survived in wounds in peach fruit equally well as the CPA-8 wild type. Taken together our data indicate that fengycin-like lipopeptides play a major role in the biological control potential of B. subtilis CPA-8 against peach brown rot.

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.

Monilinia species causing brown rot of peach in China.

In this study, 145 peaches and nectarines displaying typical brown rot symptoms were collected from multiple provinces in China. A subsample of 26 single-spore isolates were characterized phylogenetically and morphologically to ascertain species. Phylogenetic analysis of internal transcribed spacer (ITS) regions 1 and 2, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), β-tubulin (TUB2) revealed the presence of three distinct Monilinia species. These species included Monilinia fructicola, Monilia mumecola, and a previously undescribed species designated Monilia yunnanensis sp. nov. While M. fructicola is a well-documented pathogen of Prunus persica in China, M. mumecola had primarily only been isolated from mume fruit in Japan. Koch's postulates for M. mumecola and M. yunnanensis were fulfilled confirming pathogenicity of the two species on peach. Phylogenetic analysis of ITS, G3PDH, and TUB2 sequences indicated that M. yunnanensis is most closely related to M. fructigena, a species widely prevalent in Europe. Interestingly, there were considerable differences in the exon/intron structure of the cytochrome b (Cyt b) gene between the two species. Morphological characteristics, including spore size, colony morphology, lesion growth rate, and sporulation, support the phylogenetic evidence suggesting the designation of M. yunnanensis as a new species. A new multiplex PCR method was developed to facilitate the detection of M. yunnanensis and differentiation of Monilinia spp. causing brown rot of peach in China.

The combination of curing with either chitosan or Bacillus subtilis CPA-8 to control brown rot infections caused by Monilinia fructicola

Recently, it has been reported that brown rot in peaches and nectarines can be effectively controlled by exposing fruit to 50 °C for 2 h and 95–99% relative humidity (RH). This treatment was effective at reducing infections that had become established in the field. However, it did not provide protection for further Monilinia fructicola infections, indicating that fruit was susceptible to subsequent infections after the treatment process and before cool storage. Chitosan and Bacillus subtilis (strain CPA-8) were evaluated for their ability to prevent M. fructicola infections and for their ability to complement the heat treatment. Two chitosan concentrations (0.5% or 1%) were applied at three temperatures (20, 40 or 50 °C) for 1 min to wounded and unwounded fruit that were artificially inoculated with M. fructicola. One percent chitosan applied at 20 °C had a preventive effect against further M. fructicola infections on heat-treated fruit that had been previously inoculated: brown rot incidence was reduced to 10%, in comparison with the control (73%). However, chitosan applied to wounded fruit had a poor preventive effect. The antagonist, B. subtilis CPA-8, had a preventive effect in controlling M. fructicola infections: the incidence of brown rot was reduced to less than 15% for both varieties evaluated (‘Baby Gold 9’ and ‘Andros’ peaches), in comparison with the control fruit (higher than 98%). In contrast, when fruit were stored at 0 °C, this preventive effect was not detected. These findings indicate that heat-treated fruit can be protected from subsequent fruit infection after heat treatment by use of chitosan or B. subtillis CPA-8, thereby providing packinghouses with an effective biologically based, combined approach to the management of postharvest brown rot.

Peach brown rot incidence related to pathogen infection at different stages of fruit development in an organic peach production system

Brown rot, caused by Monilinia fructicola, is the most widespread disease for organic peach production systems in Brazil. The objective of this study was to determine the favorable periods for latent infection by M. fructicola in organic systems. The field experiment was carried out during 2006, 2007 and 2008 using the cultivar Aurora. After thinning fruits were bagged using white paraffin bags, and the treatments were performed by removing the bags and exposing the fruit for four days to the natural infection during each of seven fruit stages from pit hardening to harvest. Throughout the entire growing season, the conidial density and the weather variables were measured and related to the disease incidence using multiple regression analyses. At the fourth day after harvest in each season, the cumulative disease incidence was assessed, and it ranged from 40 to 98%. The incidence of brown rot on fruit that were exposed during the embryo growing stage was lower than that of unbagged fruit throughout the entire season in 2006 and 2008. The relative humidity and the conidia density were significantly correlated to disease incidence. Based on our results, M. fructicola can infect peaches during any stage of fruit development, and control of the disease must be revised to account for organic peach production systems.