Prestorage heat treatment reduces pathogenicity of Penicillium expansum in apple fruit

Penicillium expansum is one of the main postharvest pathogens of apples in Israel. Heating apple fruit inoculated with P. expansum for 96 h at 38°C completely inhibited decay development. Fruit held for 24 h at 42°C or 12 h at 46°C had significantly reduced decay after an additional 14 days incubation at 20°C, compared with unheated inoculated control fruit. Mycelial growth and percentage spore germination in vitro were inversely proportional to length of time of exposure to various temperatures. The ET₅₀ for spore germination was 42, 34 and 20 h at 38, 42 and 46°C, respectively, while the ET₅₀ for mycelial growth was 48, 44 and 36 h at those temperatures. When Penicillium spores were incubated on crude extract prepared from the peel of apple fruits held 4 days at 38°C, germ tube elongation was significantly reduced, while the walls of the tubes were thicker, compared with germ tubes from spores incubated on crude extract prepared from peel of non-heated fruit. The evidence presented here supports the hypothesis that the effect of heating on the decay of apples caused by P. expansum is not only the result of direct inhibition of fungal germination and growth by high temperature, but is also partly due to the formation of an inhibitory substance in the heated peel.     

Molecular characterization and a multiplex allele-specific PCR method for detection of thiabendazole resistance in Penicillium expansum from apple

Thiabendazole (TBZ) is commonly used as a postharvest treatment for control of blue mold in apples caused by Penicillium expansum. Different point mutations in the β-tubulin gene conferring benzimidazole resistance have been reported in plant pathogens, but molecular mechanisms of TBZ resistance in P. expansum from apple in Washington State are unknown. Determination of TBZ resistance level showed that all 102 TBZ-resistant (TBZ-R) isolates were highly resistant. Sequencing of the majority of the β-tubulin gene showed that 76 TBZ-R isolates harboured the E198V mutation and 26 harboured the F167Y mutation, and all the sensitive isolates did not possess any of the mutations, indicating that these two point mutations in the β-tubulin gene were correlated with TBZ resistance in P. expansum from apple in Washington State. There was no association between levels of TBZ resistance and types of point mutations (E198V or F167Y) in the β-tubulin gene. A multiplex allele-specific PCR assay was developed to detect these two mutations simultaneously. Microsatellite-primed PCR derived presence-absence matrix used to assess the genetic relationship among 56 isolates suggested that the resistance mutations originated several times independently and that there was no correlation between the types of point mutation and the genetic background of the isolates.     

Control of Penicillium expansum by plant volatile compounds

Nine plant volatiles were tested for their activity in vitro and in vivo against Penicillium expansum , the cause of blue mould of pear. In vitro spore germination and mycelial growth assay showed a consistent fungicidal activity by trans -2-hexenal, carvacrol, trans -cinnamaldehyde and citral, while hexanal (-)- carvone, p -anisaldehyde, eugenol and 2-nonanone exhibited a progressively lower inhibition. trans -2-Hexenal was the best inhibitor of conidial germination [MIC (minimum inhibitory concentration) = 24·6  µ L L⁻¹; ED₅₀ = 10·2  µ L L⁻¹], while carvacrol was the best inhibitor of mycelial growth (MIC = 24·6  µ L L⁻¹; ED₅₀ = 9  µ L L⁻¹). The four most active compounds in in vitro studies were tested in vivo as fumigants against blue mould on pear cv. Conference. Best control was achieved by trans -2-hexenal vapour treatments (12·5  µ L L⁻¹) when applied over a 24-h period, beginning 24 h after inoculation. In contrast, carvacrol (12·5–200  µ L L⁻¹), and trans -cinnamaldehyde (50–400  µ L L⁻¹) were ineffective and citral (200  µ L L⁻¹) showed only slight effect.     

Laboratory resistance to dicarboximides and ergosterol biosynthesis inhibitors in Penicillium expansum

Samenvatting Isolaten vanPenicillium expansum werden geselecteerd op moutagar met een dicarboximide (iprodion, procymidon, vinchlozolin) of een ergosterol biosynthese remmer (fenarimol, fenapanil, imazalil, prochloraz). De verkregen isolaten vertoonden alleen kruisresistentie tegen fungiciden behorende tot dezelfde groep van middelen. Deze kruisresistentie kon ook in dompelproeven met geïnoculeerde appels worden aangetoond. Alle getoetste isolaten bezaten in mengpopulaties van gevoelige en resistente isolaten op appels een relatief laag competitief vermogen.     

Antifungal vapour-phase activity of allyl-isothiocyanate against Penicillium expansum on pears

The fungitoxicity of allyl-isothiocyanate (AITC) vapour against Penicillium expansum , the causal agent of blue mould on pears (cvs Conference and Kaiser), was evaluated. The best control of blue mould was obtained by exposing fruits for 24 h in a 5 mg L⁻¹ AITC-enriched atmosphere, the extent of control depending on the inoculum density. Lesion diameter was inversely related to AITC concentration. In treated fruits the percentage of infected wounds increased with conidial concentration, with fewer than 20% affected at 1 × 10³ conidia mL⁻¹ to almost 80% at 1 × 10⁶ conidia mL⁻¹. In comparison, >98% of wounds were infected in untreated fruits irrespective of conidial concentration. AITC treatments were effective up to 24 h after inoculation for Conference and 48 h for Kaiser. AITC treatments also controlled a thiabendazole-resistant strain of P. expansum , reducing the incidence of blue mould by 90% in both cultivars. The use of AITC produced from pure sinigrin or from Brassica juncea defatted meal may be an economically viable alternative to synthetic fungicides against P. expansum .     

Changes in xyloglucan endotransglucosylase/hydrolase (XTHs) expression and XET activity during apple fruit infection by Penicillium expansum Link. A

Although the plant cell wall is an extremely effective physical barrier against attack by pathogens, most phytopathogenic microorganisms produce enzymes that are capable of degrading cell wall polymers such as pectin and hemicelluloses. In this work we investigate the possible implication of the cell wall enzyme XET in the host-pathogen interaction as well as the XTH gene regulation during apple fruit infection by Penicillium expansum Link. A. We characterized the time course of fungal infection in apple fruit, and the XET activity and the expression of eleven MdXTHs. The results showed an important decrease in XET specific activity in the fruits after 24, 48 and 72 h of fruit infection (42.9 %, 73.1 % and 95.1 % respectively as compared with the controls). The expression analysis of the MdXTHs showed an important decrease in expression, as the infection progressed, in MdXTH2 and MdXTH10, as well as in MdXTH3, MdXTH4 and MdXTH5, but mainly after 72 h of fruit infection; and in MdXTH1, and MdXTH9 after 24 and 48 h of infection. These results suggested that the decrease in XET activity during infection could be mainly attributed to the decrease in expression of MdXTH2 and MdXTH10, since those were the MdXTHs that showed the highest expression levels during ripening, particularly MdXTH10. These results support the suggestion that inhibition of MdXTHs expression, and consequently the decrease in XET specific activity, could represent a pathogenicity factor, since the potential reconstructing role of the enzyme also decreased and the infection could progress.     

微重力对扩展青霉孢子萌发、菌丝生长和致病力的影响

 After being onto 22nd recoverable satellite of China for 18-day spaceflight under microgravity condition,me growth and pathogenicity of PeniciUium expansum were investigated.Spore germination rate of the spaceflight pathogen was insignificantly lower than that of the ground control.After germination,germ tube elongation of spaceflight pathogen was slower,as well as mycelia growth.However,there was no significant difference according to independent-samples T-test.The consistent results were obtained in vivo.The space. flight pathogen exhibited a little weaker pathogenicity in peach fruit.These findings suggested that the microgravity reduced the growth and pathogenicity of P.expansum.but the effect Was not marked.     

10种杀菌剂对猕猴桃果实采后青霉病菌的室内毒力测定

[目的]扩展青霉是猕猴桃的重要病害之一,严重影响品质与产量.通过试验,测定10种杀菌剂对猕猴桃果实采后青霉病菌(Penicillium expansum)的毒力.[方法]利用牛津杯法测定不同种杀菌剂对P.expansum的毒力.[结果]所供10种杀菌剂对P.expansum均有一定的抑菌作用,250 g/L丙环唑、95...     

Studies on thiabendazole resistance of Penicillium expansum of pears: pathogenic fitness and genetic characterization

Isolates of Penicillium expansum recovered from stored pears were scored for resistance to the fungicide thiabendazole (TBZ) and for pathogenic fitness. Out of 50 isolates, nine were sensitive (S) and 41 resistant (R or RR). Seven of these resistant isolates (RR) germinated with a higher percentage on TBZ-amended medium than on unamended medium. Six S isolates and six RR isolates were chosen at random for further analysis. S and RR isolates had similar in vitro growth fitness, although RR isolates were characterized by higher infection severity on fruits. Laboratory-induced resistant isolates were generated by UV-irradiating S strains, and a similar correlation between the induced TBZ resistance and pathogenic fitness was observed. The β-tubulin gene of RR and S isolates was amplified and sequenced; mutations correlating with TBZ resistance were identified at residues Phe 167 and Glu 198. Analogous mutations were detected in the laboratory-induced resistant isolates.     

Stability and fitness of pyraclostrobin- and boscalid-resistant phenotypes in field isolates of Botrytis cinerea from apple

Phenotype stability, fitness, and competitive ability of pyraclostrobin- and boscalid-resistant isolates of Botrytis cinerea from apple were investigated. Stability of resistance was determined after consecutive transfers on potato dextrose agar (PDA) or being cycled on apple fruit. In vitro fitness components mycelial growth, osmotic sensitivity, conidial germination, and sporulation were evaluated on agar media. Pathogenicity, virulence and sporulation on apple fruit were evaluated at both 20 and 0°C. Competition between fungicide-resistant and -sensitive isolates on apple fruit also was evaluated. Resistance to the two fungicides was retained at levels similar to that of the initial generation after 20 and 10 transfers on PDA and five and three disease cycles on apple fruit at 20 and 0°C, respectively. Great variability in individual fitness components tested was observed among isolates within the same phenotype groups either sensitive or resistant to the fungicides but, when compared as phenotype groups, there were no significant differences in the mean values of these fitness components between resistant and sensitive phenotypes except that the phenotype resistant only to boscalid produced fewer conidia in vitro than sensitive isolates. Resistant isolates were as pathogenic and virulent on apple fruit as sensitive isolates. There was no significant correlation between the values of individual fitness components tested and the level of resistance to pyraclostrobin or boscalid, except that virulence at 20°C positively correlated with the level of resistance to the two fungicides. The final frequency of pyraclostrobin-resistant individuals in the populations was significantly decreased compared with the initial generation and no boscalid-resistant individuals were detected after four disease cycles on apple fruit inoculated with a pair mixture of a dual-sensitive isolate and one isolate each of the three phenotypes resistant to pyraclostrobin, boscalid, or both. The results suggest that resistance of B. cinerea to pyraclostrobin and boscalid was stable in the absence of the fungicides and that resistance to the two fungicides did not significantly impair individual fitness components tested. However, both pyraclostrobin- and boscalid-resistant isolates exhibited competitive disadvantage over the dual-sensitive isolate on apple fruit.     

Effects of certain herbicides on the fate of sporangiospores of Mucor piriformis and conidia of Botrytis cinerea and Penicillium expansum

The effects of several herbicides used in pome fruit orchards on the germination of spores and growth of mycelia of Botrytis cinerea, Mucor piriformis and Penicillium expansum in vitro and the survival of propagules of these fungi in soil were studied. Diuron in agar at 4–128 μg ml^?1 reduced germination of spores of B. cinerea and M. piriformis, and 2,4-D and paraquat at 32 μg ml^?1 similarly affected B. cinerea and P. expansum. Several herbicides at 128 μg ml^?1 in agar reduced growth of B. cinerea and M. piriformis but were ineffective against P. expansum. Propagule survival levels of the three fungi generally were lower in both autoclaved and non-autoclaved soil amended with herbicides than in non-amended soil. This effect was greatest in non-autoclaved soil, suggesting involvement of microbial antagonists. The most effective herbicides for reduction of fungal propagules in soil were 2,4-D, diuron, and paraquat.     

Nutritional Enhancement of Biocontrol Activity of Candida sake (CPA-1) against Penicillium expansum on Apples and Pears

Pome fruits are poor in nitrogenous compounds and the addition of nitrogen can improve colonisation of the fruits by antagonists. Twenty-two nitrogenous compounds were evaluated for their effect on Candida sake (CPA-1) growth in vitro. Ten compounds that induced greater growth were applied with the antagonist to wounded fruits to evaluate their effect on enhancing control of Penicillium expansum. Calcium chloride and 2-deoxy-D-glucose were also tested. L-serine and L-aspartic acid enhanced biocontrol by C. sake against P. expansum on apples. On apples and pears, ammonium molybdate, calcium chloride and 2-deoxy-D-glucose improved the capacity of the antagonist to control P. expansum. The addition of ammonium molybdate at 1 mM allowed C. sake to be used on apples and pears at a lower concentration without diminishing control. Similar results were observed with the addition of calcium chloride to the antagonist. 2-deoxy-D-glucose at 6 and 18 mM enhanced biocontrol on pears by over 81%, but on apples the improvement of biocontrol was observed only at 6 mM. In cold storage, the combination of ammonium molybdate and C. sake completely eliminated the incidence of blue mould on pears, and reduced its severity and incidence by more than 80% on apples.     

Antifungal Activity of 2-Deoxy-D-Glucose on Botrytis cinerea, Penicillium expansum, and Rhizopus stolonifer: Ultrastructural and Cytochemical Aspects

ABSTRACT The effect of 2-deoxy-D-glucose on major postharvest pathogens was investigated at the ultrastructural and cytochemical level. Hyphae of Botrytis cinerea, Penicillium expansum,, and Rhizopus stolonifer grown in the absence of 2-deoxy-D-glucose were normal and showed no apparent cytological alterations. In the presence of 2-deoxy-D-glucose, however, these fungi exhibited severe cellular injuries ranging from cell wall disruption to cytoplasm disintegration. Although 2-deoxy-D-glucose caused cytoplasmic degeneration in the three fungi tested, cell wall alterations were exhibited only by B. cinerea and R. stolonifer. In the latter, the retraction of degenerated cytoplasm was often accompanied by the deposition of amorphous material in paramural spaces. Cytochemical study of fungal cell wall components showed that 2-deoxy-D-glucose caused a marked increase of chitin- and beta-1,3-glucan-labeling in R. stolonifer and B. cinerea, indicating an interference of 2-deoxy-D-glucose with fungal wall biosynthesis. The observed cellular alterations indicate that 2-deoxy-D-glucose may also have affected other metabolic processes.     

河北省红富士苹果青霉病病菌种类鉴定

青霉病在苹果储藏期引起苹果腐烂,造成较大的经济损失.对采自河北省保定、沧州、石家庄等地冷库红富士苹果病果进行分析,共分离到42个青霉菌菌株.根据病原菌的形态特征,将42个菌株划分为4个类型.依据柯赫氏法则对分离到的菌株进行研究,4个类型青霉均为致病菌,分别为扩展青霉、冰岛青霉、壳青霉和圆弧青霉.根据分离频率和致病性数据分析,扩展青霉为优势菌株.     

Factors affecting the efficacy of post-harvest fungicide applications for the control of blue mould (Penicillium expansum) in stored apples

The effects of apple fruit maturity, temperature of fruit or dip solution, period of time in fungicidal dip, storage conditions, and spore inoculum concentration, on the efficacy of fungicides for control of blue mould ( Penicillium expansum ) were examined in various experiments.
Iprodione and imazalil were only effective when inoculum concentration was low, whilst prochloraz was highly effective in controlling rot on fruit inoculated with 3 × 10⁶ spores/ml. There was no consistent effect of dip temperature or fruit maturity on the efficacy of the fungicides. Iprodione was more effective on warm fruit (19°C) than cold fruit (6°C) whilst the reverse was true of imazalil. Extended periods of immersion in the fungicides slightly reduced the incidence of rotting but not to any useful degree.
The incidence of rotting in fruit treated with prochloraz and etaconazole was less in fruit stored under controlled-atmosphere cold storage conditions than in fruit stored in air cold-storage. Both fungicides were also effective for short-term storage at 20 C in air. Captan, benomyl, captan plus benomyl or vinclozolin were either ineffective or of poor efficacy under all storage conditions.     

苹果枝枯病病原菌鉴定及生物学特性

<正>苹果(Malus pumila Mill.)是世界上栽培最为广泛的水果之一,由于其生态适应性强、营养价值高、耐贮性好及供应周期长,相当多的国家都将其列为主要消费果品[1],而我国是世界上苹果种植面积最大、产量最高的国家[2]。我国苹果枝干病害以苹果轮纹病和腐烂病为主,近年来随着气候环境的改变,一些新的病害也逐渐产生。2017年7月对烟台市几个苹果果园调查时,发现一种新病害。该病害主要危害苹果枝条,产生褐色坏死病斑,严重时导致枝条枯死,发     

苹果枝枯病病原菌鉴定及生物学特性

In July 2017, a new shoot dieback disease, caused brown necrotic spots with black granules on the shoots in the late stage, was found in several apple orchards in Yantai, Shandong Province. The fungal pathogen was isolated on PDA plate from the infected shoots using the tissue isolation, which formed white to grey colonies bearing abundant fruiting bodies on Czapek solid media with lactose as carbon source. The purified fungal isolates La1-La3 were obtained from single spore isolation after spore tendrils exuding from pycnidia generated on the plates. This study was to identify and characterize the causal agent . Based on morphological characteristics and analysis of rDNA internal transcribed spacer (ITS), β-tubulin (TUB) and translation elongation factor 1-α (TEF1) nucleotide sequences, the fungal isolates were identified as Lasiodiplodia pseudotheobromae, a new pathogen on apple tree. The test of Koch's rule confirmed that L. pseudotheobromae was the pathogen of this disease. Effects of different temperature, pH value, carbon and nitrogen sources were tested against the growth of isolated fungus in vitro. The results showed that the optimal growth temperature and pH value were at 30℃ and pH 6-9, respectively, while the optimum carbon source was sucrose, and favourable nitrogen sources were sodium nitrate, ammonium nitrate and peptone.     

Control of blue mold (Penicillium expansum) by fludioxonil in apples (cv Empire) under controlled atmosphere and cold storage conditions

A reduced risk fungicide, fludioxonil, was tested for its efficacy against blue mold caused by thiabendazole-resistant and -sensitive Penicillium expansum (Link) Thom in apples under three storage conditions. In a co-treatment, fludioxonil and inoculum were applied together to test the protective activity of the fungicide on wounds that had been aged for 1 or 2 days. The fungicide was also tested for its curative activity in post-inoculation treatment on apples that had been inoculated for 1 or 2 days. Fludioxonil was very effective as co-treatment and as post-inoculation treatment. At a concentration of 300 mg litre(-1), fludioxonil gave complete control of post-harvest blue mold caused by the thiabendazole-resistant and -sensitive P expansum for 105 days in controlled atmosphere (CA) storage at 2 (+/-1) degrees C, for 42 days in common cold storage at 4 (+/-1) degrees C and also in a shelf-life study for 6 days at 20 (+/-1) degrees C. Comparison on the effect of fludioxonil in CA storage and common cold storage showed that higher concentrations of fungicide were needed in cold storage than in CA storage. Fludioxonil at a concentration of 450 mg litre(-1), gave 98 and 92% control of blue mold of apples in the simulated shelf-life studies after CA and common cold storages, respectively. Fludioxonil has a potential to be incorporated in the fungicide resistance management strategies for control of blue mold in apples stored for 105 days.     

Characterization of Venturia inaequalis pathogenicity on leaf discs of apple trees

Characterization of pathogenicity on whole plants is required to study host-pathogen interactions between Malus × domestica and Venturia inaequalis. We studied the reliability of an in vitro test of pathogenicity on leaf discs. Three strains of V. inaequalis (races 1, 6 and an English race) were inoculated in vitro onto a range of 16 Malus sp. clones including susceptible and resistant clones. The results were compared to those previously obtained in vivo. Resistant clones contained the main major known genes, i.e. Va, Vb, Vbj, Vf, Vg, Vm and Vr. Scab severity and the sporulation of the fungus were assessed 21 days after the inoculation date. The results indicated that it was possible to reproduce incompatible and compatible situations in vitro. A null severity corresponded to the avirulence of the strain for the clone considered. The resistance given by the Vb, Vbj, Vf, Vg, Vm and Vr genes were expressed in vitro. Only the clone carrying the Va gene and inoculated with the race 6 strain presented a compatible situation which was inconsistent with the observations on the whole plant. Improving this test will facilitate studies on the pathogenicity of V. inaequalis populations in relation to resistance genes of the host expressed in vitro as well as its genetic determinism.