Italicum Wehmer Research Articles

Morpho-molecular charactrization of endophytic fungi associated with aquilaria malaccensis lam.

A total of 26 fungal isolates were identified from Aquilaria malaccensis Lam. (Agarwood). Among them Aspergillus flavus Link type-1, Aspergillus flavus Link type-2, Aspergillus niger Tiegh. type. 1, Aspergillus niger Tiegh. type. 2, Aspergillus sp. 1, Aspergillus sp. 2, Alternaria alternata (Fr.) keissl., Curvularia lunata (Wakker) Boedijn, Penicillum digitatum (Pers.) Sacc., Penicillium commune Thom, Penicillum italicum Wehmer, Penicillium sp. 1, Penicillium sp. 2, Penicillium sp. 3, Penicillium sp. 4, Eupenicillium sp. 1, Eupenicillium sp. 2, Sphaeropsis sp. Sacc. and Harknessia sp. Cooke. were identified by morphological analysis and Alternaria tenuissima (Kunze) Wiltshire, Alternaria palandui Ayyangar, Fusarium sporotrichioides Sherb., Lasiodiplodia theobromae (Pat.) Griffon & Maubl., Lasiodiplodia pseudotheobromae A.J.L. Phillips, A. Alves & Cronus, Diaporthe hongkongensis R.R. Gomes, Glienke & Cronus and Diaporthe perseae (Zerova) R.R. Gomes, Glienke & Cronus were identifed upto genus level by morphological analysis, which were later on identified and confirmed at species level by molecular analysis. Among these isolated fungal species- Alternaria palandui, Diaporthe hongkongensis, Diaporthe perseae and Lasiodiplodia pseudotheobromae have been reported as newly recorded species and Harknessia sp. and Sphaeropsis sp. were reported as new generic records for Bangladesh. Bangladesh J. Plant Taxon. 31(1): 141-154, 2024 (June)

In vivo efficacy of natural essential oil of Syzygium aromaticum L. bud for protecting the Pisum sativum L. seeds

The mycological investigations on sixty samples of stored garden pea food seeds revealed presence of twelve and ten species of fungi by blotter and agar plate techniques respectively. The fungal species were associated with genera viz., Alternaria, Aspergillus, Botrytis, Chaetomium, Cladosporium, Curvularia, Fusarium, Penicillium and Rhizopus. The fungal species viz., Cladosporium herbarum (Pers.) Link and Penicillium italicum Wehmer did not show its appearance in agar plate method. It showed dominance of Aspergillus flavus, Aspergillus niger, Aspergillus ochraceous, Aspergillus terreus in blotter method in comparison to agar plating. Aspergillus tmarii, P. italicum and Rhizopus stolonifer did not grow on sterilized seeds in Blotter method. Pathogenicity tests of dominant fungi caused biodeterioration in garden pea seeds. The antifungal testing of essential oils revealed Syzygium aromaticum L. bud oil to be fungitoxic at 500 ppm (0.025 mL). The minimum inhibitory concentration of the S. aromaticum oil was found to be 300 ppm against four fungi viz., A. flavus, A. niger, A. ochraceous and A. terreus. At this concentration the oil was found to be fungicidal and thermostable. The oil activity was not affected by physical factors and showed broad spectrum. In vivo study depicted that clove oil was more effective in comparison to EDCT. It controlled a maximum of 4 fungi while the clove oil showed no growth of fungi even after 6 months storage.

A Review on the Role of Silicon Treatment in Biotic Stress Mitigation and Citrus Production

This paper reviews the threat of citrus pathogens during citrus production, with a focus on two pre-harvest diseases, citrus leaf spot, caused by Alternaria alternata (Fr.) Keissl. (1912) and brown rot, caused by Phytophthora citrophthora (R.E. Sm. and E.H. Sm.) Leonian, (1906) as well as green and blue mold post-harvest disease, caused by Penicillium digitatum (Pers.) Sacc. and P. italicum Wehmer, (1894), respectively. Furthermore, it reviews the role of soluble silicon, Si nutrition in biotic stress mitigation and potential mitigation mechanisms. Previous studies on the use of Si fertilizers have focused on high accumulator Si crops. These have demonstrated the potential of Si to reduce the occurrence of biotic stresses, which takes place through both physical and biochemical mechanisms. However, few studies have demonstrated the potential of Si to mitigate biotic stress in citrus, or the mechanisms involved. There is a clear need for studies on the impact of Si on various stress biochemical pathways in plants generally, and specifically for citrus due to the huge loss caused by pre- and post-harvest pathogens. This will assist in deepening our understanding of the pathophysiology which is essential to develop resistant cultivars.

First Report of Penicillium ulaiense Causing Postharvest Whisker Mold of Oranges (Citrus sinensis) in Spain

In a survey of postharvest losses in citrus packinghouses located in Valencia province (Spain) conducted during the 2017 to 2018 citrus season, mold symptoms distinctive from those of the most frequent and well-known citrus green and blue molds (caused by Penicillium digitatum [Pers.] Sacc. and Penicillium italicum Wehmer, respectively) were observed in about 1 to 2% of the sampled molded orange fruits (Citrus sinensis L.). Distinctive symptoms on sporulated soft lesions were the grayish blue color of the conidial masses and the presence of whisker-like coremia with tall whitish stalks. This whisker mold was often found in mixed infections with green and/or blue molds in the same fruit. The potential causal agent (isolate IVIA NAV-1) was transferred to potato dextrose agar (PDA) plates and purified by consecutive replating after 7 days of incubation at 25°C. At this time, colonies were mostly circular, compact, 30 to 40 mm in diameter, with dense velvety grayish mycelium and abundant bluish conidia. Conidiophores were sinoid, mostly terverticillate, and conidia were cylindrical to ellipsoidal, smooth, and thin walled, measuring 4.8 to 8.4 × 2.0 to 3.2 μm. Based on these morphological characteristics, the isolate IVIA NAV-1 was tentatively identified as Penicillium ulaiense H.M. Hsieh, H.J. Su & Tzean (Frisvad and Samson 2004). To confirm the identity, molecular identification was performed in a specialized laboratory. The rDNA internal transcribed spacer regions ITS 1 and ITS 2 and the β-tubulin gene were amplified, sequenced, and deposited in GenBank (accessions nos. MH477872 and MH477873, respectively). A BLAST search for ITS showed 100% identity and 100% query coverage with P. ulaiense strain CBS 210.92 (accession no. KC411695.1). A BLAST search for the β-tubulin gene showed 99% identity and 100% query coverage with P. ulaiense isolate 1399 (accession no. LT629297.1). Selected healthy oranges of cultivar Valencia were surface disinfected by dipping in 0.5% sodium hypochlorite for 2 min followed by thorough rinsing in deionized water. Pathogenicity was tested by pipetting 30 µl of a spore suspension (1 × 10⁶ conidia/ml), prepared from 7- to 10-day-old PDA cultures, onto fresh rind wounds, which were made on the equatorial area of disinfected fruit using a sterile, stainless steel rod with a probe tip of 1 mm in width × 2 mm in length (one wound per fruit, total of 20 oranges). Additionally, 10 disinfected, wounded, noninoculated oranges were used as controls. The same procedure was repeated 15 days later with another lot of Valencia oranges. In both tests, disease symptoms were observed on all inoculated fruit after 7 days of incubation at 25°C, and P. ulaiense was consistently reisolated, thereby fulfilling Koch’s postulates. No decay was observed on any of the control fruit. To our knowledge, this is the first report of P. ulaiense causing whisker mold of citrus fruit in Spain. The disease has been previously reported in important citrus-producing areas such as California (Holmes et al. 1993), Egypt (Youssef et al. 2010), Pakistan (Khan et al. 2017), and Korea (Park et al. 2018).

Plant diseases associated with olive bark midge in West-Bank Palestine

Olive tree is one of the most cultivated trees over the Palestinian territories, it is considered as the mainstay of rainfed agriculture in Palestine. Recently and due to the impact of the global warming, olive trees were infected with an outbreak of many pests and pathogens. In the last decades, both olive fruit fly, Bactrocera oleae (Diptera, Tephritidae) and peacock leaf spot, Spilocaea oleagina were reported with an unusual percentage of infections over the olive trees. During 2015–16, and throughout the field surveys to investigate any unusual diseased symptoms on olives; some trees exhibited pale yellowing on the newly formed branches, symptoms associated with viral infections such as OLYaV. Some other trees were noticed to get yellowing and later on developed branch dieback and stem canker and cracking syndromes. When the outer bark was removed, the affected tissue appeared dark brown, in contrast to the yellowish green of healthy inner bark. These symptoms were observed on both young and old trees in the northern part of Palestine. Field and laboratory investigation revealed a heavy infestation with larvae of Resseliella oleisuga Targ. (Diptera: Cecidomyiidae). The infestation rate reported ranged from 75 to 92 in some olive orchards. Pathogens were isolated and identified based on cultural morphology. Climate changes due to the global warming might be the cause of this outbreak; probably due to the changes in the environmental conditions favoured by the insects. To our knowledge, this is the first time this insect was reported to be widely spread of olive trees and causing damage in Palestine. In this study, several associated primary, secondary and saprophytic diseases were detected from the infected samples. Mainly Botryosphaeria spp., Alternaria solani Sor., Aspergillus niger v. Tieghem, Cladosporium herbarum Fr., Fusarium solani (Mart.) App., Penicillium digitatum Sacc., Penicillium italicum Wehmer, Rhizopus stolonifer (Her.) Vuill.

In Vitro Evaluation of Antioxidant and Antimicrobial Activities of Melaleuca alternifolia Essential Oil.

The in vitro antioxidant and antimicrobial activity of the essential oil from Melaleuca alternifolia (M. alternifolia) was evaluated in this report. The antioxidant potential of the essential oil from M. alternifolia was evaluated by the DPPH (2,2-diphenyl-1-picrylhydrazyl) method, thiobarbituric acid reactive species (TBARS) assay, and the hydroxyl radical scavenging activity method. The essential oil from M. alternifolia was able to reduce DPPH with an EC50 (concentration for 50% of maximal effect) of 48.35 μg/ml, inhibit the lipid peroxidation with an IC50 (50% inhibitory concentration) of 135.9 μg/ml, and eliminate hydroxyl radicals with an EC50 of 43.71 μg/ml. Antimicrobial screening, minimum inhibitory concentration, and minimum bactericidal concentration assays showed that the essential oil from M. alternifolia inhibited strongly the growth of different types of microorganisms, including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Penicillium italicum Wehmer, and Penicillium digitatum Sacc. Thus, the essential oil of M. alternifolia possesses antioxidant and antimicrobial activity and could be suitable for use as a natural preservative ingredient in food, agriculture, and pharmaceutical industries.

Screening and identification of antagonistic bacteria with potential for biological control of Penicillium italicum of citrus fruits

A total of 81 bacterial isolates from the surface of mandarines, apples, lemons and kumquats were screened for antagonism against Penicillium italicum wehmer and used to control postharvest blue mold. Bacterial YS-1 was isolated from the surface of kumquat fruit and identified as Paenibacillus brasilensis by the Biolog microbial identification system combined with 16S rDNA sequence analysis, biochemical and physiologic characteristics and rpoB sequence analysis. YS-1 showed obvious antifungal activity to four different fruit pathogens. Effect of different treatments with strain YS-1 against disease caused by P. italicum on inoculated Nanfeng oranges was also investigated. Results showed that citrus blue mold incidence of fruits treated by cell culture, cell-free filtrate and cell suspension of strain YS-1 were all less than 45% and the lesion diameter were all below 10mm. Also the treatment of cell suspension showed significant comparing with other two treatments. Lesion diameter and disease incidence treated at 5°C were higher than those at 25°C. In this article, strain YS-1 is reported for the first time as a biocontrol agent against blue mold of citrus. The research will provide a theoretical basis for research of postharvest antagonistic bacteria in citrus.

Effect of volatile compounds produced by Bacillus strains on postharvest decay in citrus

The antifungal effects of volatile compounds produced by Bacillus strains; Bacillus subtilis PPCB001 or Bacillus amyloliquefaciens PPCB004 and antagonist combination (PPCB001 + PPCB004) against Penicillium digitatum Sacc., Penicillium italicum Wehmer and Penicillium crustosum Thom isolates were investigated in vitro and in vivo. The antagonists alone or in combination inhibited the radial mycelial growth of Penicillium spp. in vitro. Among the three Penicillium isolates tested P. crustosum showed 73.3% of mycelial growth inhibition in presence of PPCB004. The antifungal effects of volatiles increased with increasing time (days), and PPCB004 showed the highest inhibition of radial mycelial growth in P. crustosum on the 10th day. The EC 50 was 2.5 × 10 5 CFU ml −1 for PPCB001; 9.45 × 10 6 CFU ml −1 for PPCB004 and 7.76 × 10 6 CFU ml −1 for PPCB001 + PPCB004. Antagonist PPCB004 incubated at 37 °C for 24 h showed higher inhibitory effect on spore germination and germ tube elongation in P. crustosum than all other treatments. Although, PPCB001 produced a higher number of volatile compounds (21 different types) than PPC004 (8 different types), 3-hydroxy-2-butanone (acetoin) was the predominant ketone produced by both PPCB001 (45.98%) and PPCB004 (97.52%). Antagonist PPCB004 showed significant inhibition on decay incidence and severity in Valencia, inoculated with P. crustosum and held at 25 °C for 12 days. The observations indicated that B. amyloliquefaciens PPCB004 to control P. crustosum in postharvest systems.

Seed-Borne Pathogens of Faba Bean in Egypt: Detection and Pathogencity

This study was undertaken to study the seed-borne fungi of faba bean that attack the plants and reduce their yield in Egypt. The results provide a database for further study to control the pathogens. Twenty-six seed samples representing six faba bean cultivars collected from different parts of Egypt were used in this investigation. The blotter and deep-freezing methods were used. Surface- and non-surface-sterilized faba bean seeds were tested to detect and isolate the associated seed-borne fungi. The following 20 fungal species belonging to 13 genera were observed and identified: Aspergillus flavus (Link ex. Gray), Aspergillus niger (Van Tieghem), Aspergillus ochraceus (Wilhelm), Penicillium digitatum (Pers.:Fr.) Sacc., Penicillium italicum (Wehmer), Alternaria alternata (Fr.) Keissler, Botrytis faba (Sardina), Cephalosporium sp., Cladosporium cladosporioides (Frensen. de Vries), Epicoccum nigrum (Link), Fusarium oxysporum (Schlechlendahl), Fusarium semitectum (Berkeley and Ravenel), Fusarium solani (Mart.) Sacc., Fusarium verticillioides (moniliforme) (Sheld), Rhizoctonia solani (Kuhn), Rhizopus stolonifer (Ehr. ex Fr.), Stemphylium globuliferum (Vestergr.) E.G. Simmons), Trichothecium roseum (Pers.) Link, Verticillium dahliae (Ehrenp) Vuill. The blotter method yielded a greater number of fungi than the deep-freezing method on both surface and non-surface sterilized seeds, but the deep-freezing method was better for slow-growing fungi. The pathogenicity test revealed that the most commonly isolated fungi from pre- and post-emergence damping-off and stunted seedlings were F. verticillioides, R. solani, Cephalosporium sp. and V. dahliae. These fungi significantly reduced the photosynthetic pigments in faba bean leaves. Fusarium verticillioides caused the greatest reduction in chlorophyll content (A, B and total chlorophyll). Fusarium oxysporum and V. dahliae significantly reduced carotenoid content. R. solani significantly reduced total phenols content when compared with the other tested fungi.

Biological control of Penicillium italicum, P. digitatum and P. expansum by the predacious yeast Saccharomycopsis schoenii on oranges.

In this study we evaluated the ability of Saccharomycopsis schoenii Nadson and Krassiln (UWO-PS 80-91) as biocontrol agent against plant pathogenic filamentous fungi P. expansum Link (UFMG 01-2002), P. italicum Wehmer (LCP 61.1199), and P. digitatum (Pers.: Fr.) (LCP 984263, LCP 68175 and LCP 4354). S. schoenii was able to reduce disease severity in oranges inoculated with all fungi. Among the phytopathogens, P. digitatum LCP4354 was the most virulent whereas P. digitatum LCP 68175 was the most susceptible to predation. The yeast was able to survive for 21 days on the fruit surface and did not produce lesions on oranges. Production of antagonistic substances by S. schoenii was not detected using standard techniques. Our results point to the potential use of S. schoenii to control postharvest phytopathogens in fruits.

In vitro effects of water activity, temperature and solutes on the growth rate of P. italicum Wehmer and P. digitatum Sacc.

To evaluate the effect of water activity (a(w) 0.98-0.89, adjusted with glycerol, sorbitol, glucose, or NaCl) and temperature (5-25 degrees C) on the lag phase and radial growth rate (mm day(-1)) of the important citrus spoilage fungi, such as Penicillium italicum and Penicillium digitatum grown in potato dextrose agar (PDA) medium. To select, among models based on the use of different solutes, a model fitting accurately the growth of these species in relation to a(w) and temperature. Extensive data analyses showed for both Penicillium species a highly significant effect of a(w), temperature, solutes and their interactions on radial growth rate (P < 0.0001). Radial growth rate was inhibited and the lag phase (i.e. the time required for growth) lengthened as the a(w) of the medium decreased. NaCl appeared to causes the greatest stress on growth when compared with other nonionic solutes. Penicillium italicum stopped growing at 0.96 a(w) and P. digitatum at 0.93 a(w). Under the dry conditions where growth was observed, P. italicum grew faster than P. digitatum at low temperature and P. digitatum remained more active at ambient temperature. Multiple regression analysis applied to the square roots of the growth rates observed in the presence of each solute showed that both the 'glycerol model' and the 'sorbitol model' yielded a good prediction of P. italicum growth and the 'sorbitol model' gave an accurate fit for P. digitatum growth, offering high-quality prediction within the experimental limits described. Mathematical models describing and predicting, as a function of a(w) and temperature, the square root of the radial growth rate of the agents responsible for blue and green decays are important tools for understanding the behaviour of these fungi under natural conditions and for predicting citrus fruit spoilage. Implementation of these results should contribute towards a more rational control strategy against citrus spoilage fungi.

Integration of pre- and postharvest treatments to minimize Penicillium decay of Satsuma mandarins

Abstract Green and blue mold, caused by Penicillium digitatum (Pers.) Sacc. and P. italicum Wehmer, respectively, cause significant losses of Satsuma mandarins (Citrus unshiu Marc.) after harvest. The effects of some pre- and postharvest treatments on development of these diseases and on the wound healing processes of Satsuma mandarin fruit were determined. Trees were treated with CaCl2 in combination with growth regulators (2,4-D and GA3) and benomyl before harvest. Fruit were harvested from each treatment and wounded at three sites. One group was inoculated with the pathogens immediately while another group was inoculated 3 days later. Of these, one group was held at 30 °C with high humidity (90–95%) for 72 h, which is a thermal curing regime, and another was exposed to UV-C light for 10 min. Green and blue mold incidence after harvest during storage was inhibited by preharvest treatments containing benomyl. UV light treatments also reduced green mold, but caused some injury to the fruit. The disease incidence was very low among fruit that were held at 30 °C with high humidity (90–95%) for 72 h compared to the other treatments. Combinations of these treatments were additive in efficacy.

The use of sodium carbonate to improve curing treatments against green and blue moulds on citrus fruits.

The effectiveness of curing oranges and lemons at 33 degrees C for 65h followed by storage under ambient and cold-storage conditions was investigated. This treatment effectively reduced the incidence of Penicillium digitatum (Pers) Sacc and P italicum Wehmer decay on inoculated and naturally infected oranges and lemons stored at 20 degrees C for 7 days. However, it failed to control green and blue mould infections on fruits placed in long-term cold storage, except green mould on oranges, which was effectively controlled. Dipping fruits in a sodium carbonate solution (20 g litre(-1)) for 2.5 min following a curing treatment at 33 degrees C for 65 h satisfactorily reduced green and blue mould incidence during subsequent long-term storage at 4 degrees C on oranges and at 10 degrees C on lemons. The efficacy was greater on injured fruits inoculated after the combination of treatments was applied, achieving a 60-80% reduction in decay in comparison with the curing treatment alone in all cases. A significant reduction of blue mould was also observed on fruits inoculated both before the treatments and on those re-inoculated after the treatments, demonstrating both protectant and eradicant activity. Thus, combining curing at 33 degrees C for 65 h with sodium carbonate treatment effectively controlled these post-harvest diseases on artificially inoculated citrus fruits and protected against re-infection. With naturally inoculated lemons, curing followed by sodium carbonate significantly reduced both green and blue mould incidence, but was not superior to curing alone. With naturally infected oranges, curing significantly reduced blue mould, but decay was not reduced further when followed by sodium carbonate treatment.

Nitrous Oxide Inhibits In Vitro Growth of Multiple Postharvest Fungi

Nitrous oxide (N2O) was tested as a potential fungicidal or fungistatic compound. Twelve postharvest fungi were exposed to 10 to 80 kPa with 20 kPa O2 in a static system at 20 °C. These fungi were divided into N2O high-, medium- and low-sensitive groups. Based on growth sensitivity, growth of high-sensitive fungi was completely inhibited, and that of medium-sensitive fungi up to 85%. With low-sensitive fungi, significant inhibition was achieved only when the fungi were exposed to N2O continuously for 6 days. Botrytis cinerea Pers.: Fr., Colletotrichum acutatum Simmonds, Monilinia fructicola (Winter) Honey, Penicillium expansum Link, Penicillium italicum Wehmer, Phytophthora citrophthora (R.E. Smith and E.H. Smith) Leonian and Rhizopus stolonifer (Ehrens.: Fr.) Vuillemin, were high-sensitive; Glomerella cingulata (Stoneman) Spaulding was medium-sensitive, and Alternaria alternata (Fr.) Keissler, Fusarium oxysporum Schlechtend1: Fr. f. sp. fragariae Winks and Williams, Fusarium oxysporum Schlechtend1: Fr. f. sp. lycopersici (Saccardo) Snyder and Hansen., and Geotrichum candidum Link., were low-sensitive fungi. Addition of up to 100 μL·L-l C2H4 did not reduce inhibition caused by N2O. The inhibitory effect of N2O was considered to be due to biophysical properties similar to CO2, the competitive inhibition on C2H4 action, or the biosynthesis of methionine. These results indicate the potential of N2O to control some postharvest decay fungi.

The Effect of Some Fungicide Treatments and Storage Regimes on the Postharvest Diseases of Citrus Fruits

Fruits of mandarin, orange, grapefruit and lemon, which received no fungicide treatment before harvest and at packing, stored at ambient temperature for 2 months, and kept at cold storage conditions for two and four months. During storage 16.8, 25.1 and 65.4 % crop losses were observed, respectively, due to development of total postharvest diseases. Citrus trees were sprayed with benomyl, fosetyl-Al, and CuSO4.5H2O+ZnSO4.6H2O+hydrated lime to control postharvest diseases 1-1.5 month before harvest time. Also, dipping of fosetyl-Al, benomyl, sodium o-phenylphenate, 2.4-D isopropyl-ester in water, and spraying of benomyl and imazalil in a water-wax were used to control for postharvest diseases of citrus fruits during packing processes. Some lemon fruits were stored in wrapped biphenyl emitted papers. Combination of preharvest fungicide treatments with treatments during packing, assumed to be the most effective control measure against postharvest diseases, resulted 2.4 % crop losses in 2 months ambient conditions, and 9.8-20.9 % in 2-4 months cold storage conditions. When compared with non treated control groups, the savings were 14.4 % in 2 months ambient conditions, and 15.3-44.5 % in 2-4 months cold storage conditions. The effect of combined treatments (some fungicide treatments in 1-1.5 month before harvest, and during packing period) on control of postharvest diseases was 89.9 aünd 60.1-72.1 % in ambient and cold storage conditions, respectively. Mandarin, orange, grapefruit and lemon fruits which were only treated during 1-1.5 month before the harvest were stored for 2 months in ambient conditions and for 4 months in cold storage rooms. In this case, total postharvest diseases were controlled at a rate of 57.5 and 40.0 %, respectively. However, in the case of fruits treated with fungicides alone in packinghouse, showed controlling levels of 68.8 and 55.1 %. The incidence of total postharvest diseases in the lemon fruits which were treated with the combined fungicide treatments and wrapped into biphenyl emitted papers stored 2 months in ambient and 2-4 months cold storage conditions were 2.5 and 0, 7.5 % and resulting disease control were 18.8 and 15.0, 33.8 %, respectively. In this study, then main postharvest diseases observed were Alternaria citri Ellis et Pierce stem end rot, Penicillium italicum Wehmer and Penicillium digitatum Sacc. blue and green molds, Colletotrichum gloeosporioides ( Penz.) Sacc. antrachnose, and Geotrichum candidum Link. ex Pers. sour rot on rotted mandarin, orange, grapefruit, and lemon fruits which were treated with the combined fungicide treatments. In combined fungicide treatments, A. citri

Fumigation of Fruit with Acetic Acid to Prevent Postharvest Decay

Acetic acid (AA) as a vapor at low concentrations was effective in preventing fruit decay by postharvest fungi. Fumigation with 2.7 or 5.4 mg AA/liter in air at 2 and 20C reduced germination of Botrytis cinerea Pers. and Penicillium expansum Link conidia to zero after they had been dried on 0.5-cm square pieces of dialysis tubing. Decay of `Golden Delicious', `Red Delicious', and `Spartan' apples (Malus domestica Borkh.) inoculated with 20 μl drops of conidia of B. cinerea (1.0 × 105 conidia/ml) or P. expansum (1.0 × 106 conidia/ml) was prevented by fumigating with 2.0 and 2.7 mg AA/liter, respectively. Tomatoes (Lycopersicon esculentum Mill.), grapes (Vitis vinifera L.), and kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et R. Ferguson var. deliciosa] inoculated with B. cinerea or navel oranges (Citrus sinensis L.) inoculated with P. italicum Wehmer did not decay when fumigated with 2.0 mg AA/liter at 5C. AA fumigation at low temperatures (1 and 5C) with 2.0 or 4.0 mg AA/liter prevented decay of `Spartan' and `Red Delicious' apples and `Anjou' pears (Pyrus communis L.) inoculated with B. cinerea and P. expansum, respectively. `Spartan' apples immersed in a suspension of P. expansum conidia (1.4 × 105 conidia/ml) and fumigated with 2.7 mg AA/liter at 5C had an average of 0.7 lesions per fruit compared to 6.1 for nontreated fruit. Increasing the relative humidity from 17% to 98% increased the effectiveness of AA fumigation at 5 and 20C. At the concentrations used in our trials, AA had no apparent phytotoxic effects on the fruit. The potential for commercial fumigation with AA to control postharvest decay of fruit and vegetables appears promising.

Inhibition of sterol biosynthesis in cell‐free extracts of Botrytis cinerea by prochloraz and prochloraz analogues

AbstractThe sensitivity of cytochrome‐P450‐dependent sterol 14α‐demethylase (P45014DM) to prochloraz and several prochloraz analogues was studied in a cell‐free assay of Botrytis cinerea Pers. ex Fr. The EC50 values (concentrations which inhibited radial growth of B. cinerea by 50%) of the compounds tested ranged from 3.3 × 10 −8 to 1.7 × 10 −5 M. The IV50 values (concentrations which inhibited cell‐free C4‐demethyl sterol synthesis by 50%) in cell‐free assays of B. cinerea ranged from 2.6 × 10 −9 to 4.4 × 10 −7 M. Ranking compounds in terms of their relative inhibitory potencies showed quite similar trends to the order of fungitoxicity, but the IC50 values did not quantitatively reflect the differences in toxicity. Therefore, the differential inhibition of cell‐free P45014DM activity by these compounds cannot fully account for their differences in activity towards B. cinerea. Additional mechanisms must be involved.The compounds tested were generally more potent in the B. cinerea assay than in similar assays developed for Penicillium italicum Wehmer and, in particular, Saccharomyces cerevisiae Meyen. This correlated with the relatively higher activity of most test compounds to B. cinerea. Results suggest that the cell‐free assay of B. cinerea is more useful to evaluate candidate fungicides as inhibitors of sterol 14α‐demethyiase activity than similar assays from model organisms.The present study confirms that the affinity of prochloraz analogues for P45014DM depends on the nature of the N‐1 substituent of the imidazole and the azole ring. It was also found that addition of an amino group at C‐2 of the imidazole moiety of prochloraz gave a compound (6) which inhibited 4, 4‐demethyl sterol biosynthesis in B. cinerea at a different site from the P45014DM. This was confirmed by the observation that laboratory‐generated triadimenol‐resistant isolates of B. cinerea showed reduced sensitivity to triadimenol and prochloraz, but not to compound 6.

ED50 levels of Penicillium digitatum and P. italicum with reduced sensitivity to thiabendazole, benomyl and imazalil

The ED50 values of 415 isolates of Penicillium digitatum Sacc. and P. italicum Wehmer with reduced sensitivity to thiabendazole (TBZ), benomyl (BEN) and/or imazalil (IM) were assessed. The isolates were collected from decayed grapefruit (Citrus paradisi Macf.), lemons (C. limon (L.) Burm. f.), mandarins (C. reticulata Blanco) and oranges (C. sinensis (L.) Osbeck) from 14 geographical origins. The isolates were cultured on potato dextrose agar containing yeast extract and amended with a series of fungicide concentrations. The mean ED50 values of P. digitatum were 15.8 mg/L for TBZ, 6.3 mg/L for BEN and 0.88 mg/L for IM. Double-resistant (that is, resistant to both IM and benzimidazole fungicides) isolates were significantly more sensitive to TBZ and/or BEN than isolates resistant to the benzimidazoles only. The mean ED50 values of P. italicum were 22.6 mg/L for TBZ and 4.7 mg/L for BEN. The resistance levels of green and blue mold to the benzimidazoles were related to their geographical origins.

Postharvest biological control of Penicillium rots of citrus with antagonistic yeasts and bacteria

Two yeasts, Debaryomyces hansenii (Zopf) Van Rij and Aureobasidium pullulans (De Bary) Arnaud, and two bacteria, Pseudomonas cepacia (Van Hall) Bergy et al. and P. syringae Burkholder, were the most effective antagonists from over 100 isolates tested against Penicillium digitatum Sacc. and Penicillium italicum Wehmer rots on citrus fruit. Overall, P. cepacia provided the best protection against both of these rots. P. cepacia produced antibiotic zones against the two Penicillia rot organisms in culture, whereas P. syringae, D. hansenii and A. pullulans did not. All four antagonists show promise as biocontrol agents.

Metabolites of Penicillium italicum Wehmer: Isolation and structures of new metabolites including naturally occurring 4-ylidene-acyltetronic acids, italicinic acid and italicic acid.

Four new metabolites, italicic acid, dihydro-italicic acid, methyl italicate and italicinic acid, were isolated from culture medium of Penicillium italicum WEHMER. The structures, possessing a 4-ylidene-acyltetronic acid unit, and their biosynthesis were elucidated. Two other new metabolites possessing a chromone skeleton were also isolated and their structures were established as 6, 7-dihydroxy-3-(1'-hydroxy-3'-butanoyl)chromone-5-carboxylic acid and its 1', 2'-dehydrate.