Antifungal activity of some plant extracts on some pathogenic fungi

The inhibitory activity of five plant extracts viz. Artemisia absinthium L., Rumex obtusifolius L., Taraxacum officinale Weber ex Wiggers, Plantago lanceolata L. and Malva sylvestris L. were evaluated against the mycelial growth of three fungi Alternaria alternata (Fr.) Keissler, Penicillium expansum Link ex Thom. and Mucor piriformis Fisher that cause rot diseases in fruits and vegetables resulting in low yield and quality of fruits and vegetables. Results revealed that all the concentrations of plant extracts brought about significant inhibition in the mycelial growth of these pathogenic fungi. However, the highest concentration caused maximum inhibition in the mycelial growth followed by lower concentrations of plant extracts. The extract of A. absinthium leaves at highest concentration (S) proved highly effective in inhibiting the mycelial growth of all these pathogenic fungi followed by other plant extracts. These plants thus may have potential as the new natural fungicide for management of fungal rot diseases.     

In vitro assessment of fungicidal activity of Ageratum conyzoides and Cybopogon flexuosus weed extracts against some phytopathogenic fungi associated with fruit rot of water melon (Citrullus lunatus (Thunb.))

The ethanolic extracts of Cybopogon flexuosus and Ageratum conyzoides were tested at concentrations of 20, 40, 60, 80, 100 and 120?mg/ml for their in vitro fungicidal activities against five phytopathogenic fungi isolated from diseased watermelon fruits. The pathogens were Fusarium verticillioides, Aspergillus flavus, Botryodiplodia theobromae, Curvularia lunata and Alternaria cucumeria – Amans as confirmed by pathogenicity tests. All isolated pathogenic fungi were significantly (p?≥?0.05) highly pathogenic with the exception of A. cucumeria which had the least significant (p?≥?0.05) pathogenicity. The inhibitory effects of the extracts increased significantly (p?≥?0.05) with increase in concentrations. Some of the concentrations reduced the mycelial growth of the pathogens to a significant (p?≥?0.05) level. Very strong fungicidal activity was produced by extracts of A. conyzoides at 100?mg/ml against all the fungi. The inhibitory effects of C. flexuosus extracts at 20, 40 and 60?mg/ml were greater than those of C. flexuosus on A. flavus, F. verticillioides and A. cucumeria. The results of the investigation indicated that plant extracts possess antifungal activity that can be exploited as an ideal treatment for future plant disease management in the control of rot of water melon.     

Impact of the dual defence system of Plantago lanceolata (Plantaginaceae) on performance,nutrient utilisation and feeding choice behaviour of Amata mogadorensis larvae (Lepidoptera,Erebidae)

Iridoid glycosides are plant defence compounds with potentially detrimental effects on non-adapted herbivores. Some plant species possess β-glucosidases that hydrolyse iridoid glycosides and thereby release protein-denaturing aglycones. To test the hypothesis that iridoid glycosides and plant β-glucosidases form a dual defence system, we used Plantago lanceolata and a polyphagous caterpillar species. To analyse the impact of leaf-age dependent differences in iridoid glycoside concentrations and β-glucosidase activities on insect performance, old or young leaves were freeze-dried and incorporated into artificial diets or were provided freshly to the larvae. We determined larval consumption rates and the amounts of assimilated nitrogen. Furthermore, we quantified β-glucosidase activities in artificial diets and fresh leaves and the amount of iridoid glycosides that larvae feeding on fresh leaves ingested and excreted. Compared to fresh leaves, caterpillars grew faster on artificial diets, on which larval weight gain correlated positively to the absorbed amount of nitrogen. When feeding fresh young leaves, larvae even lost weight and excreted only minute proportions of the ingested iridoid glycosides intact with the faeces, indicating that the hydrolysis of these compounds might have interfered with nitrogen assimilation and impaired larval growth. To disentangle physiological effects from deterrent effects of iridoid glycosides, we performed dual choice feeding assays. Young leaves, their methanolic extracts and pure catalpol reduced larval feeding in comparison to the respective controls, while aucubin had no effect on larval consumption. We conclude that the dual defence system of P. lanceolata consisting of iridoid glycosides and β-glucosidases interferes with the nutrient utilisation via the hydrolysis of iridoid glycosides and also mediates larval feeding behaviour in a concentration- and substance-specific manner.     

Studies on the fungi associated with tomato fruit rots and effects of environment on storage

Seven fungi associated with fruit rot of tomato were isolated includingFusarium equiseti, F. chlamydosporum, Alternaria solani, Geotrichum candidum, Acremonium recifei, Aspergillus flavus andA. niger. They were all pathogenic on tomato fruits, most pathogenic beingGeotrichum candidum followed byA. niger. Least rot was caused byAlternaria solani. The optimum temperature for maximum rotting caused byG. candidum, A. niger andA. flavus was 30°C. The relative humidity for maximum rot ranged from 70–90%. Tomato fruits stored well at 0–10°C and rather poorly at 20–30°C. Fruits stored at 35°C showed blemishes. The best RH for storage ranged between 60 and 90%.     

Determination and comparative analysis of major iridoids in different parts and cultivation sources of Morinda citrifolia

Introduction – Noni is a medicinal plant with a long history of use as a folk remedy in many tropical areas, and is attracting more attention worldwide. A comprehensive study on the major phytochemicals in different plant parts (fruit, leaf, seed, root and flower) and sources is of great value for fully understanding their diverse medicinal benefits. Objective – To quantitatively determine the major iridoid components in different parts of noni plants, and compare iridoids in noni fruits collected from different tropical areas worldwide. Methodology – The optimal chromatographic conditions were achieved on a C₁₈ column with gradient elution using 0.1% formic acid aqueous formic acid and acetonitrile at 235 nm. The selective HPLC method was validated for precision, linearity, limit of detection, limit of quantitation and accuracy. Results – Deacetylasperulosidic acid (DAA) was found to be the major iridoid in noni fruit. In order of predominance, DAA concentrations in different parts of the noni plant were dried noni fruit > fruit juice > seed > flower > leaf > root. The order of predominance for asperulosidic acid (AA) concentration was dried noni fruit > leaf > flower > root > fruit juice > seed. DAA and AA contents of methanolic extracts of noni fruits collected from different tropical regions were 13.8–42.9 and 0.7–8.9 mg/g, respectively, with French Polynesia containing the highest total iridoids and the Dominican Republic containing the lowest. Conclusion – Iridoids DAA and AA are found to be present in leaf, root, seed and flower of noni plants, and were identified as the major components in noni fruit. Given the great variation of iridoid contents in noni fruit grown in different tropical areas worldwide, geographical factors appear to have significant effects on fruit composition. The iridoids in noni fruit were stable at the temperatures used during pasteurisation and, therefore, may be useful marker compounds for identity and quality testing of commercial noni products. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Fungal Infection and Temperature on Physiological Changes in Banana Fruit

An attempt was made to investigate which factor temperature or fungal infection, has a greater effect in accelerating physiological processes such as respiration and ethylene evolution in fruit. For this study the effect of infection with Trichothecium roseum, Alternaria alternata and Diplodia natalensis on banana fruit, at 14°C and 20°C was examined. The results show that the development of rot caused by different fungi and the physiological changes in the infected fruit may depend not only on the effect of temperature on fungi (as in vitro) but also on fruit ripening, or on processes connected with fruit ripening, which may accelerate fungal development.     

The relationship between tomato fruit growth,incidence of blossom-end rot and phytohormone content as affected by sink/source ratio

Blossom-end rot is generally considered a calcium-related physiological disorder. The results of the previous studies show that several factors such as plant conditions can be effective on the blossom-end rot incidence. Therefore, the present study was undertaken to investigate the effect of the sink/source ratio on the incidence of the blossom-end rot of two greenhouse tomato (Solanum lycopersicum L.) cultivars: ‘Grandella’ and ‘Isabella’. To this end, four treatments were applied: saving one fruit per truss (1F), two fruits per truss (2F), three fruits per truss (3F), and no fruit pruning (control). The results showed that the tomato cultivar ‘Isabella’ was more susceptible to the blossom-end rot than ‘Grandella’. Decreasing the sink/source ratio increased the incidence of the blossom-end rot and the relative fruit growth rate. The correlation between the blossom-end rot incidence and the relative fruit growth rate showed that the fruit growth rate could be regarded as an important factor in the incidence of this disorder. Endogenous auxin and cytokinin concentrations acted as the regulators of the fruit growth rate and influenced it. Slowing down the relative growth rate by keeping proper sink/source ratio based on tomato cultivar is, therefore, an effective, cheap and healthy way to control the incidence of the blossom-end rot, especially in organic farming.     

Effect of storage conditions on virulence of Fusarium avenaceum and Alternaria alternata on apple fruits

To overcome difficulty in phytopathogenic fungi control during storage of apple fruits, the effect of different storage conditions on the occurrence and development of Fusarium avenaceum and Alternaria alternata infections on apple cultivar “Cripps Pink” was investigated during and after storage. Inhibitory effects of wild oregano essential oil on apple fruit rots caused by F. avenaceum and A. alternata were also tested as possible rot control measure. Artificially inoculated apple fruits were kept in cold storage with normal (NA) and controlled (CA) atmosphere for 95 days and at room temperature only. The obtained results indicated that different storage conditions significantly affect necrosis development on apple fruits caused by F. avenaceum and A. alternata after storage, as well as during shelf life.     

Potential benefits of iridoid glycoside sequestration in Longitarsus melanocephalus (Coleoptera,Chrysomelidae)

Whenever potentially noxious plant compounds are taken up and recycled by herbivorous insects, a protective function of these sequestered compounds is assumed. The flea beetle Longitarsus melanocephalus sequesters iridoid glycosides from its host plant up to a concentration of 2% DW, yet so far it remained unknown whether the insects gain protection from natural enemies by sequestering plant compounds at these comparatively low concentrations. Here we tested whether iridoid glycosides might deter or inhibit various soil and litter-dwelling potential enemies and pathogens. In choice experiments presenting L. melanocephalus pupae together with Tribolium castaneum pupae, the predator Lithobius forficatus was deterred by the iridoid glycoside containing pupae, while Forficula auricularia as well as the nematode Heterorhabditis bacteriophora were not deterred. L. forficatus also avoided artificial baits doted with 2% iridoid glycosides while F. auricularia showed no aversion to iridoid glycosides at these concentrations and H. bacteriophora did not suffer any toxic effect. Of the pathogens tested, the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae were not inhibited in their growth by iridoid glycosides ranging up to 2%. However, an inhibitory effect could be observed against the entomopathogenic bacterium Bacillus thuringiensis, even at the relatively small concentrations that are common in L. melanocephalus. The antibacterial effect might thus be another important selective value of iridoid glycoside sequestration in this species.     

Effect of fungal species involved in the olive fruit rot on the qualitative properties of olive oil

Olive oil is the most important product of olive fruits with worldwide consumption, particularly in Mediterranean countries. Olive oil is generally extracted mechanically from the olive fruits. Some biotic and abiotic factors may affect the quality of oil extracted from olive fruit. Contamination with fungi during growth period in the garden or during the conservation of the harvested crop under storage condition may leave negative effects on the quality of olive oil. However, there is no data available on the effects of fungal infections on qualitative properties of olive oil in Iran. In the present study effects of several fungal groups previously isolated from rotten olive fruit in olive orchards including Alternaria alternata, Fusarium nygamai, Aspergillus ochraceus, Arthrinium phaeospermum, Cladosporium cladosporioides, Aureobasidium pullulans, Epicoccum nigrum, Penicillium expansum, Truncatella angustata, Trichothecium roseum and Trichoderma harzianum were evaluated on some qualitative properties of olive oil, under laboratory condition on two olive cultivars (Zard & Roghani). For this purpose fresh and healthy fruits of olive, were surface sterilisation with 96% ethanol and rinsed with sterile water and then inoculated with each of the fungal groups separately using spore suspension (10^6?ml^?1). The experiment was carried out in two replicates for each treatment (fungal isolates). The results of this study revealed that fungal infection caused significant increase in the extracted oil acidity and peroxide values. However, there was no significant difference in the acidity and peroxide values among different treatments (fungal isolates).     

一株具有拮抗作用的解淀粉芽孢杆菌的筛选、鉴定及生物学特性研究

本研究以樱桃番茄成熟红果为样本,以极细链格孢菌为指示菌筛选得到一株对番茄采后病原菌有抑制作用的菌株KL-1。通过平板拮抗试验研究了菌株KL-1对番茄采后常见病原真菌极细链格孢菌、黑曲霉、青霉菌、尖侧多隔孢霉、拟康宁木霉、盐生枝孢霉、子囊菌、胶孢炭疽菌等八种病原菌的抑制作用,同时通过形态学、生理生化及16S rDNA分子生物学特征对菌株进行了鉴定,并对其基本生物学特性进行了研究。结果表明:菌株KL-1对于七种病原菌极细链格孢菌、黑曲霉、青霉菌、拟康宁木霉、盐生枝孢霉、子囊菌和胶孢炭疽菌均有明显的抑制作用,其中对黑曲霉的抑制率最大为81%,对其他六种病原菌抑制率也均高于70%,对尖侧多隔孢霉的抑制率为0,说明菌株KL-1可以抑制番茄多种常见病原真菌,具有开发为生防制剂的潜力。经鉴定KL-1为解淀粉芽孢杆菌(Bacillus amyloliquefaciens);该菌培养9 h内生长最旺盛,最适生长pH为7.0,最适生长温度为37℃。     

Patulin and aflatoxin in brown rot lesion of apple fruits and their regulation

Aspergillus flavus, A. niger, Penicillium expansum and Rhizopus stolonifer were the most frequently isolated fungi from healthy apple fruits. Alternaria alternata was the most common organism of rotten apple fruits, followed by A. niger, A. flavus, P. expansum and R. stolonifer. The prevalent type of decay, brown rot lesion, is caused by R. stolonifer followed by A. flavus, A. niger, A. alternata and P. expansum. Sodium hypochlorite had good curative properties against fruit rots. The main natural mycotoxins produced in rotten apple were patulin and aflatoxins. The optimum temperature for patulin production by P. expansum was 15 °C after 15 days. Complete inhibition of patulin formation was attained using 0.2% lemon oil and > 90% inhibition using 0.05% lemon and 0.2% orange oils. Also significant inhibition (> 90%) of aflatoxin production was observed with 0.2% lemon oil. This revised version was published online in July 2006 with corrections to the Cover Date.     

Plant chemical defense against herbivores and pathogens: generalized defense or trade-offs?

Plants are often attacked by multiple enemies, including pathogens and herbivores. While many plant secondary metabolites show specific effects toward either pathogens or herbivores, some can affect the performance of both these groups of natural enemies and are considered to be generalized defense compounds. We tested whether aucubin and catalpol, two iridoid glycosides present in ribwort plantain (Plantago lanceolata), confer in vivo resistance to both the generalist insect herbivore Spodoptera exigua and the biotrophic fungal pathogen Diaporthe adunca using plants from P. lanceolata lines that had been selected for high- and low-leaf iridoid glycoside concentrations for four generations. The lines differed approximately three-fold in the levels of these compounds. Plants from the high-selection line showed enhanced resistance to both S. exigua and D. adunca, as evidenced by a smaller lesion size and a lower fungal growth rate and spore production, and a lower larval growth rate and herbivory under both choice and no-choice conditions. Gravimetric analysis revealed that the iridoid glycosides acted as feeding deterrents to S. exigua, thereby reducing its food intake rate, rather than having post-ingestive toxic effects as predicted from in vitro effects of hydrolysis products. We suggest that the bitter taste of iridoid glycosides deters feeding by S. exigua, whereas the hydrolysis products formed after tissue damage following fungal infection mediate pathogen resistance. We conclude that iridoid glycosides in P. lanceolata can serve as broad-spectrum defenses and that selection for pathogen resistance could potentially result in increased resistance to generalist insect herbivores and vice versa, resulting in diffuse rather than pairwise coevolution.     

Studies on fungi associated with tomato fruits and effectiveness of some commercial fungicides against three pathogens

Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994,Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes,Alternaria alternata, Rhizopus stolonifer andA. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory againstA. alternata, A. niger andR. stolonifer. At 10 and 100 µg ml^–1, neither of the fungicide caused a noticeable inhibition ofAlternaria rot. At 1000 µg ml^–1 benlate, rovral and sumisclex completely preventedAlternaria andAspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused byA. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 µg ml^–1). Sodium hypochlorite has good curative properties against fruit rots especially those caused byA. alternata andA. niger.     

Fruit-specific overexpression of wound-induced tap1 under E8 promoter in tomato confers resistance to fungal pathogens at ripening stage

Based on high economic importance and nutritious value of tomato fruits and as previous studies employed E8 promoter in fruit ripening-specific gene expression, we have developed transgenic tomato plants overexpressing tomato anionic peroxidase cDNA (tap1) under E8 promoter. Stable transgene integration was confirmed by polymerase chain reaction (PCR) and Southern analysis for nptII. Northern blotting confirmed elevated tap1 levels in the breaker- and red-ripe stages of T(1) transgenic fruits, whereas wild-type (WT) plants did not show tap1 expression in these developmental stages. Further, tap1 expression levels were significantly enhanced in response to wounding in breaker- and red-ripe stages of transgenic fruits, whereas wound-induced expression of tap1 was not detected in WT fruits. Confocal microscopy revealed high accumulation of phenolic compounds at the wound site in transgenic fruits suggesting a role of tap1 in wound-induced phenolic polymerization. Total peroxidase activity has increased remarkably in transgenic pericarp tissues in response to wounding, while very less or minimal levels were recorded in WT pericarp tissues. Transgenic fruits also displayed reduced post-harvest decay and increased resistance toward Alternaria alternata and Fusarium solani infection with noticeable inhibition in lesion formation. Conidiospore germination and mycelial growth of F. solani were severely inhibited when treated with E8-tap1 fruit extracts compared to WT fruits. 3-(4,5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay showed reduced spore viability when incubated in E8-tap1 fruit extracts. Thus, fruit-specific expression of tap1 using E8 promoter is associated with enhanced total peroxidase activity and high phenolic accumulation in fruits with minimized post-harvest deterioration caused by wounding and fungal attack in tomato fruits.     

Studies on seed-borne fungi of wheat in seed health testing programme

Seed mycoflora associated with wheat was studied on different media with a particular reference to Blotter and potato dextrose agar (PDA) procedures of ISTA. Seed-borne fungi, viz. Fusarium moniliforme, Rhizopus spp., Mucor spp., Alternaria alternata, Aspergillus niger, Aspergillus flavus, Curvularia lunata, Drechslera spp, Alternaria spp. and Penicillium spp., were isolated from the variety HD264. Blotter method was found to be the best media for the isolation of mycoflora whether borne externally or internally. Total number and frequency of occurrence of fungi were recorded. The effect of seed treatment with different chemicals and eco-friendly botanicals was analysed on germination, and growth, better percentage of seed germination and reduction in fungal pathogen were due to biochemical seed treatment.     

Nonpathogenic, environmental fungi induce activation and degranulation of human eosinophils

Eosinophils and their products are probably important in the pathophysiology of allergic diseases, such as bronchial asthma, and in host immunity to certain organisms. An association between environmental fungal exposure and asthma has been long recognized clinically. Although products of microorganisms (e.g., lipopolysaccharides) directly activate certain inflammatory cells (e.g., macrophages), the mechanism(s) that triggers eosinophil degranulation is unknown. In this study we investigated whether human eosinophils have an innate immune response to certain fungal organisms. We incubated human eosinophils with extracts from seven environmental airborne fungi (Alternaria alternata, Aspergillus versicolor, Bipolaris sorokiniana, Candida albicans, Cladosporium herbarum, Curvularia spicifera, and Penicillium notatum). Alternaria and Penicillium induced calcium-dependent exocytosis (e.g., eosinophil-derived neurotoxin release) in eosinophils from normal individuals. Alternaria also strongly induced other activation events in eosinophils, including increases in intracellular calcium concentration, cell surface expression of CD63 and CD11b, and production of IL-8. Other fungi did not induce eosinophil degranulation, and Alternaria did not induce neutrophil activation, suggesting specificity for fungal species and cell type. The Alternaria-induced eosinophil degranulation was pertussis toxin sensitive and desensitized by preincubating cells with G protein-coupled receptor agonists, platelet-activating factor, or FMLP. The eosinophil-stimulating activity in Alternaria extract was highly heat labile and had an M(r) of approximately 60 kDa. Thus, eosinophils, but not neutrophils, possess G protein-dependent cellular activation machinery that directly responds to an Alternaria protein product(s). This innate response by eosinophils to certain environmental fungi may be important in host defense and in the exacerbation of inflammation in asthma and allergic diseases.     

珍珠柴粗提物对13种植物病原菌的抑制活性

以生长速率法测定了珍珠柴7种溶剂粗提物对棉花黄萎病菌V991、棉花黄萎病菌V43-1、棉花枯萎病菌、茄子黄萎病菌、稻曲病病菌、苹果黑星病菌、番茄枯萎病菌、番茄叶霉病菌、黄瓜黑星病菌、西瓜炭疽病菌、芦笋茎枯病菌、扩展青霉和梨黑斑病菌13种植物病原菌的抑制活性。结果表明,不同溶剂粗提物的抑菌活性差异很大,某些溶剂粗提物对个别病菌表现出较强的抑制作用,如水粗提物对棉花黄萎病菌V991,石油醚粗提物对苹果黑星病菌的抑制率分别达100%和91.89%;有的溶剂粗提物的病菌抑制作用较弱,如二氯甲烷粗提物对13种病菌的抑菌率均较低;有些还表现出一定的促进生长作用,如甲醇粗提物对梨黑斑病菌表现为明显的促进生长作用。     

Early Root Herbivory Impairs Arbuscular Mycorrhizal Fungal Colonization and Shifts Defence Allocation in Establishing Plantago lanceolata

Research into plant-mediated indirect interactions between arbuscular mycorrhizal (AM) fungi and insect herbivores has focussed on those between plant shoots and above-ground herbivores, despite the fact that only below-ground herbivores share the same part of the host plant as AM fungi. Using Plantago lanceolata L., we aimed to characterise how early root herbivory by the vine weevil (Otiorhynchus sulcatus F.) affected subsequent colonization by AM fungi (Glomus spp.) and determine how the two affected plant growth and defensive chemistry. We exposed four week old P. lanceolata to root herbivory and AM fungi using a 2×2 factorial design (and quantified subsequent effects on plant biomass and iridoid glycosides (IGs) concentrations. Otiorhynchus sulcatus reduced root growth by c. 64%, whereas plant growth was unaffected by AM fungi. Root herbivory reduced extent of AM fungal colonization (by c. 61%). O. sulcatus did not influence overall IG concentrations, but caused qualitative shifts in root and shoot IGs, specifically increasing the proportion of the more toxic catalpol. These changes may reflect defensive allocation in the plant against further attack. This study demonstrates that very early root herbivory during plant development can shape future patterns of AM fungal colonization and influence defensive allocation in the plant.     

Effect of postharvest salicylic acid treatment on fungal decay and some postharvest quality factors of kiwi fruit

The effect of salicylic acid (SA) treatment at different concentrations on fungal decay and some quality factors of kiwi fruit (Actinidia deliciosa var. Hayward) in postharvest conditions were studied. Results experiment showed that SA at all applied concentrations inhibited grey mould growth. The SA application significantly decreased weight loss percentage and increased life storage fruits. Also, SA positively affected on postharvest quality factors including total soluble solids (TSS), titratable acidity (TA), antioxidant, ascorbic acid and pH value. It was observed that treated fruits with SA at concentration 5?mM had the highest TSS, TA, ascorbic acid and antioxidant content and it had the lowest decay and acidity. Thus, these results showed that SA has strong impact on postharvest decay and fruit quality of kiwi fruit.