Efficacy of plant extracts against stored-products fungi

The fungistatic activity of six aqueous extracts of plants were tested against Aspergillus candidus, Aspergillus niger, Penicillium sp. and Fusarium culmorum. The plants were, chamomile (Anthemis nobilis L.), cinnamon (Cinnamomum verum J. Presl.), French lavender (Lavandula stoechas L.), garlic (Allium sativum L.), malva (Malva sylvestris L.) and peppermint (Mentha piperita L.). The more concentrated extracts of chamomile and malva inhibited totally the growth of the tested fungi with malva the most effective one.     

Efficacy of plant essential oils on post-harvest control of rot caused by Botrytis cinerea on kiwi fruits

Antifungal activity of the essential oils of Carum carvi and Pimpinella anisum against Botrytis cinerea fruit rot of key kiwi fruit was studied. In vitro experiments, antifungal activities of essential oils were tested on potato dextrose agar media. Results of an in vitro experiment showed that these essential oils, at all applied concentrations, inhibited grey mould growth. Black caraway essential oil at concentrations of 600 and 800?μL?L^?1 inhibited germination spores of grey mould. Then, the fruits were artificially inoculated with a suspension at 1?×?10⁵?conidia/ml and then treated with different concentrations of these essential oils. The results of in vivo conditions showed that black caraway and anise essential oils applied at all concentrations were increasing the shelf life and inhibited the grey mould growth on kiwi fruits completely in comparison to control. The result showed that black caraway and anise oils at a concentration of 800?μL?L^?1 had higher total soluble solids, ascorbic acid, titrable acidity and antioxidant content compared to untreated fruits.     

Efficacy of some plants as a post-harvest protectant against some major stored pests

The toxicity of vapours of the essential oil of Ferula gummosa, Elettaria cardamomum and Salvia officinalis on the adults and larvae of some stored product pests was investigated. The bioassays were carried out in 70 mL vials containing 10 individuals of each insect. The LC₅₀ values of fumigant bioassay after 24 h were calculated. Results indicated that the effect of the essential oil of F.gummosa was stronger than E. cardamomum, S. officinalis on stored pests. Also fumigant toxicity of S. officinalis on Sitophilus oryzae was similar to that of Sitophilus granarius adults. On the other hand, R. officinalis had a good effect on adults of Tribolium castaneum and larvae of Ephestia kuehniella. According to our results and good effect of these compounds, they will be a safe replace for chemical compounds in the future.     

Nematicidal activity of powder and extracts of Melia azedarach fruits against Meloidogyne incognita

Pulverised lyophilised (dehydrated) Melia azedarach (Meliaceae) fruits (PMF) were tested in a dose–response pot experiment against juveniles (J2) of the root-knot nematode Meloidogyne incognita. Successively, with different extraction procedures, a polar (melia methanol extract, MME) and a non-polar (melia oil, MO) fragments were obtained and their effects were tested on nematode motility and development, in dose and time response bioassays and pot experiments. An EC₅₀ value was calculated for all experiments. A dose–response effect was found in pot bioassays using PMF and, after an incubation period of 24 and 48 h, the EC₅₀ values were calculated at 0.41% and 0.34% w/w, respectively. Motility bioassays revealed a dose and time dependent response effect, after exposure to MME, but not to MO. Doses of MME higher than 0.08% were nematicidal, whereas lower ones were nematostatic (the loss of motility as a result of the presence of the substance was reversible). In a pot experiment, MME doses higher than 2.5% w/w caused 100% nematode control with EC₅₀ value of 0.916% w/w.     

Storage diseases of carrots in East Anglia 1978 – 82, and the effects of some pre- and post-harvest factors

In a survey of nine carrot crops stored during four seasons 1978 – 82, the major causes of wastage were spreading soft rots caused by Botrytis cinerea and Rhizoctonia carotae; rots caused by Sclerotinia sclerotiorum, Mycocentrospora acerina and Stemphylium radicinum were only of secondary importance. Storage weight losses were lower and roots remained turgid for up to 40 wk in an ice-bank-cooled store at 0·5 °C, 97 – 98% r.h., whereas carrots in conventionally-cooled stores at 2 – 2.5 °C, 90 – 95% r.h. became flaccid after a few months. In some crops, losses due to fungal spoilage were also lower in the ice-bank store. In two seasons' losses, mostly due to B. cinerea, were similar in hand- and machine-harvested roots; pre-storage washing of carrots grown on mineral soils increased the incidence of Botrytis rots, and reduced rotting by R. carotae, but had no effect on spoilage of roots from peat soils. Post-harvest fungicide treatment with benomyl or iprodione (0·5 g/litre a.i.) effectively reduced rotting by B. cinerea and S. sclerotiorum, but not by R. carotae. The recoveries of sound carrots after 23 – 29 wk storage were consistently highest (mostly > 80%) from fungicide-dipped roots stored under ice-bank conditions, but recoveries from all treatments were lower and more erratic after 35 – 40 wk because of increased fungal spoilage. The practical applications of long-term ice-bank storage of UK-grown carrots are discussed.     

Fungal contamination and selected mycotoxins in pre- and post-harvest maize in Honduras

Sixty nine samples of maize were collected from pre-harvest standing crops and on-farm storage facilities from 52 smallholder farms located within 4 regions of Honduras during October 1992 and November 1993. Samples were visually assessed for insect damage and fungal spoilage, and the mycoflora quantified on artificial media. The major components of the ear rot complex were:Fusarium moniliforme, F. moniliforme var.subglutinans, Penicillium species,Stenocarpella maydis, S. macrospora andAcremonium spp. Representative samples were also assayed for mycotoxin content. Fumonisin B₁ was detected in all 24 samples tested at levels of between 68–6,555 (µg/kg), and aflatoxin was detected in 2 samples heavily contaminated withAspergillus flavus. Moniliformin and tenuazonic acid were not detected in the samples tested. The implications of these findings for human and livestock health risk are discussed, together with possible strategies for controlling these pathogens.     

Development of a biological control method against postharvest diseases of citrus fruits

Candida oleophila strain O was previously selected for its high and reliable antagonistic activity against Botrytis cinerea and Penicillium expansum, two important wound pathogens on post-harvest apples. The application of these antagonistic strains on wound pathogens of Citrus was more recently undertaken. The efficacy of yeast (applied at several concentrations from 10(5) to 10(8) CFU/ml) was assessed against P. digitatum and P. italicum inoculated after one hours (at a concentration of 10(5), 106 and 10(7) spores/ml) on 'Clementine' and 'Valencia late' varieties. The protective levels were positively correlated with high concentration of antagonist and low concentration of pathogen. The antagonistic activity of this strain was also dependent on the incubation time before pathogen inoculation. The protective level increased with time between application of the antagonist and inoculation of fungal spores. Finally, the efficacy of biomass of C. oleophila strain O (produced at an industrial scale), and two different formulations of that biomass was assessed in comparison with fungicidal treatment (Thiabendazole) under semi-practical conditions against P. digitatum. This efficacy of strain O (whatever its formulation) was statistically comparable to that for TBZ at commercial dose, indicating that both formulations could be used as an alternative for conventional fungicide in postharvest treatments.     

Potency of plant extracts against Penicillium species isolated from different seeds and fruits in Saudi Arabia

Antifungal activity of extracts of cinnamon (Cinnamomum zeylanicum), Cloves (Syzygium aromaticum), ginger (Zingiber officinale) and turmeric (Curcuma longa) were evaluated in vitro against 17 Penicillium spp. Seed disease and rotten fruit caused by these species cause considerable loss of quality for different agricultural products. Isolates of Penicillium spp. were screened for production of patulin an important serious mycotoxin. About 70.59% of Penicillium spp. produced this toxin in concentrations ranging from 4 to 31 ppb. The response of Penicillium spp.to plant extracts differed according to the plant extract and concentration. Cinnamon extract showed the greatest effect on P. asperosporum, P. aurintogriseum and P. brevicompactum, and cloves extract produced the greatest effect on P. chermesinum and P. duclauxii. Turmeric extract had less effect on P. duclauxii. Cloves extract was the most effective in reducing the growth of Penicillium spp. On the other hand, ginger extract with all concentrations used had less effect against most Penicillium spp in the laboratory. Plant extracts are promising as natural sources of environmentally friendly compounds in laboratory studies.     

Efficacy of extracts of Melia azedarach L. callus, leaves and fruits against adults of the sweetpotato whitefly Bemisia tabaci (Hom., Aleyrodidae)

Bioassays with extracts of callus, fruit and leaves of the Chinaberry tree, Melia azedarach L., were performed against adults of Bemisia tabaci (Gennadius). Tissue culture of M. azedarach was carried out in Murashige and Skoog (MS) medium supplemented with indole butyric acid and benzyl adenine. Fresh and frozen leaves or fruits and the callus product were extracted in water or methanol at a ratio of 1 : 5 (w/v) for 48 h. The aqueous and methanol extracts were applied on tomato plants to determine their effect on B. tabaci adults and their corresponding oviposition and consequent adult emergence in comparison with the control, distilled water. Results have shown that extracts of callus and different age classes of M. azedarach leaves and fruits have shown significant repellent activity of 58.9–67.7% and have significantly decreased the oviposition rate of the insect without affecting the adult whitefly emergence in comparison with the control. Aqueous and methanol extracts have shown comparable effects against adult whiteflies indicating a similar efficacy of the two solvents in extracting the bioactive components of Melia . Extracts of frozen samples were found to be as effective against the pest as fresh samples, thus allowing storage of Melia parts to be used in case of shortage. This is the first report of the use of M. azedarach callus against B. tabaci; the M. azedarach callus, leaf and fruit extracts seem to present a potential source for management of B. tabaci .     

Fungitoxicity of acetaldehyde vapour to some major post-harvest pathogens of citrus and subtropical fruits

In laboratory trials, fumigation with acetaldehyde vapour at 0–75 to 20 % concentration (v/v) for 0–5 to 120 min at 21 ^oC killed six species of post-harvest citrus pathogens grown on agar media. The fungicidal effect of acetaldehyde vapour at this temperature was a function of concentration and exposure. Penicillium digitatum and P. italicum were not as susceptible to inhibition of spore germination as Alternaria citri, A. tenuis, Colletotrichum gloeosporioides and Glomerella cingulata. A concentration of 10 % acetaldehyde vapour at 21 ^oC for 10 min was fungitoxic to all the pathogens tested.     

Management of post-harvest fruit spoilage fungi by some potential spice extracts

The experiment was carried out to evaluate the antifungal potential of aqueous and ethanolic extracts of four spices (Allium sativum, Zingiber officinale, Cinnamomum zeylanicum and Capsicum annuum) against the important post-harvest spoilage fungi isolated from diseased fruits. In total, 276 isolates of post-harvest spoilage fungi were isolated from four different fruit types (Persea americana, Musa acuminata, Citrus sinensis and Lycopersicon esculentum), out of which 183 isolates were identified while 93 isolates were remain unidentified. The most dominant post-harvest spoilage fungus was Rhizopus sp. (26.45%), followed by Penicillium sp. (19.93%), Aspergillus sp. (10.86%) and Fusarium sp. (9.06%). Results of disc diffusion assay showed that ethanolic extract of C. zeylanicum was found to be most effective against Penicillium sp., followed by aqueous extracts of A. sativum. The ethanolic extract of C. zeylanicum in agar amended assay and minimal inhibitory concentrations were found to be very efficient (100% inhibition) against all the tested fungi. Results of in vivo study showed that pre-inoculated C. zeylanicum ethanolic extract and A. sativum aqueous extract were found effective in reducing the disease severity (6.24–13.67%) and (7.91–13.15%) against the Penicillium, Rhizopus, Aspergillus and Fusarium sp.     

Achieving improved control of foliar diseases of sesame (Sesamum indicum L.) intercropped with maize (Zea mays L.) through foliar spray of plant extracts

Field trials were conducted to evaluate the effect of foliar spray of aqueous extracts of Tithonia diversifolia or Ocimum gratissimum on Cercospora leaf spot (CLS) and Alternaria leaf blight (ALB) diseases of sesame intercropped with maize. Spraying regime was at 2 weeks interval from 3 weeks after planting (WAP) until 12 WAP. Extracts of T. diversifolia or O. gratissimum reduced the incidence and severity of both diseases. CLS incidence and severity as well as defoliation was significantly (p < 0.05) reduced below what obtained in the unsprayed intercrop. ALB lesion size was significantly (p < 0.05) reduced by T. diversifolia extract at 8.0% (w/v) from 154.7 mm² (sole crop) or 13.4 mm² (unsprayed intercrop) to 4.9 mm² (sprayed intercrop). T. diversifolia extract at 8.0% (w/v) enhanced higher values of grain yield/plant and incidence of normal seeds, and lower incidence of fungal infection of seeds than in the unsprayed intercrop.     

Efficacy assessment of Candida oleophila (strain O) and Pichia anomala (strain K) against major postharvest diseases of citrus fruits in Morocco

Two yeasts, Candida oleophila (strain O) and Pichia anomala (strain K), were previously selected for their antagonistic activity against postharvest diseases on apples and pears. The objective of the study was to determine the efficacy of both antagonistic yeast's against wound postharvest pathogens of citrus fruits. The efficacy of both strains (applied at 10(5), 10(6) and 10(8) CFU/ml) was assessed against Penicillium digitatum and P. italicum inoculated after one hour (at a concentration of 10(5), 10(6) and 10(7) spores/ml) on citrus varieties 'clementine' and 'valencia-late'. Fruits were incubated for one week at 24 degrees C before measurement of lesion diameter. The protective levels were positively correlated with high concentration of antagonist and low concentration of pathogen. Highest protective levels (from 73 to 100%) were detected with the application of strain O or strain K at 10(8) CFU/ml whatever the pathogen (applied at 10(5) spores/ml) and the citrus variety. The antagonistic activity of both strains was also dependent on the incubation period before pathogen Inoculation. The protective level increased with time between application of the antagonist and inoculation of fungal spores. Whatever the yeast strain (10(8) CFU/ml). the protective level exceed 70% when wounded oranges were inoculated with P. digitatum or P. italicum (both at 10(6) spores/ml) 12 hours after yeast treatment. These protective levels reached 100% when the incubation period separating the antagonist application and the pathogenic inoculation was 24 hours. On the other hand, high protective levels (< 80%) were also observed against the sour rot decay on citrus variety 'clementine' caused by Geotrichum candidum inoculated at concentration of 10(6) spores/ml when strain O or strain K were applied at 10(8) CFU/ml 24 hours before pathogen. All these results support the potential practical application of both strains against major postharvest pathogens on citrus.     

Non-conventional methods for the control of post-harvest pear diseases

Pears are highly perishable products, especially during the post-harvest phase, when considerable losses can occur. Among the fungal diseases, blue mold caused by Penicillium expansum, grey mould caused by Botrytis cinerea, Mucor rot caused by Mucor piriformis are common on pear fruits. Other (weak) pathogens like Phialophora malorum, Alternaria spp., and Cladosporium herbarum tend to infect wounds and senescent fruits. A post-harvest fungicide treatment can reduce decay but effectiveness decreases with the appearance of resistant strains. There is a clear need to develop new and alternative methods of controlling post-harvest diseases. The emerging technologies for the control of post-harvest fungal diseases are essentially threefold: application of antagonistic microorganisms, application of natural antimicrobial substances and application of sanitizing products. Two biological control products, Aspire (Candida oleophila I-182) (Ecogen, Langhorne, PA, USA) and Bio-Save 110 (Pseudomonas syringae) (EcoScience, Worcester, MA, USA; formerly Bio-Save 11) are currently registered in the USA for post-harvest application to pears. Other potential biocontrol agents have been isolated from fruit and shown to suppress post-harvest decay in pear. It is important that evaluation of these microorganisms be carried out in a product formulation because the formulation may improve or diminish antagonistic efficacy depending on the concentration of chemical product and the duration of exposure to the treatment. Plants produce a large number of secondary metabolites with antimicrobial effects on post-harvest pathogens. Detailed studies have been conducted on aromatic compounds, essential oils, volatile substances and isothiocyanates, with encouraging results. In particular, allyl-isothiocyanate used as a volatile substance, controls blue mould in 'Conference' and 'Kaiser' pear inoculated with a thiabendazole-resistant strain. Sanitizing products such as chlorine dioxide, peracetic acid and ozone have considerable fungicidal activity against P. expansum and M. piriformis, depending on the concentration of chemical product and the duration of exposure to the treatment. Sanitizing solutions can be integrated easily with current handling and storage practices; however, further research is required to define the effective procedures better.     

Efficacy of leaf extracts of some medicinal plants against disease development in banana

Treatment of infested banana fruits by aqueous leaf extracts of some medicinal plants, viz. Calotropis procera (Ait) R.Br., Vitex negundo Linn., Lantana camara Linn., Azadirachta indica Linn., Ficus religiosa Linn., Ocimum sanctum Lin., Thuja orientalis Linn., Argemone mexicana Linn., Achyranthes aspera Linn., Datura fastuosa Linn. and Ricinus communis Linn. exhibited considerable control of disease development. Of 11 leaf extracts, those of A. indica and O. sanctum were most effective, and showed minimum per cent loss in fruit weight. The appearance of the first disease symptom was also delayed in treated fruits as compared with untreated ones.     

Market diseases of fresh fruits and vegetables

Bruising, crushing, and other mechanical injuries cause very serious losses during the handling, transportation, storage, and marketing of fresh fruits and vegetables. Spoilage caused by molds and bacteria exacts a heavy toll. Freezing, chilling injury, and various physiological disorders add to the consumer cost of living. Careful handling, proper refrigeration, good marketing practices, and the use of safe, approved chemical treatments can reduce marketing losses.     

Antimicrobial activity of some plant extracts against bacterial strains causing food poisoning diseases

Prevention of food spoilage and food poisoning pathogens is usually achieved by use of chemical preservatives which have negative impacts including: human health hazards of the chemical applications, chemical residues in food & feed chains and acquisition of microbial resistance to the used chemicals. Because of such concerns, the necessity to find a potentially effective, healthy safer and natural alternative preservatives is increased. Within these texts, Plant extracts have been used to control food poisoning diseases and preserve foodstuff. Antimicrobial activity of five plant extracts were investigated against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi using agar disc diffusion technique. Ethanolic extracts of Punica granatum, Syzygium aromaticum, Zingiber officinales and Thymus vulgaris were potentially effective with variable efficiency against the tested bacterial strains at concentration of 10 mg/ml while extract of Cuminum cyminum was only effective against S. aureus respectively. P. granatum and S. aromaticum ethanolic extracts were the most effective plant extracts and showed bacteriostatic and bactericidal activities against the highly susceptible strains of food borne pathogenic bacteria (S. aureus and P. aeruginosa) with MIC's ranged from 2.5 to 5.0 mg/ml and MBC of 5.0 and 10 mg/ml except P. aeruginosa which was less sensitive and its MBC reached to 12.5 mg/ml of S. aromaticum respectively. These plant extracts which proved to be potentially effective can be used as natural alternative preventives to control food poisoning diseases and preserve food stuff avoiding healthy hazards of chemically antimicrobial agent applications.     

Under-expression of the Auxin Response Factor Sl-ARF4 improves post-harvest behavior of tomato fruits

Auxin is one of the most prominent phytohormones regulating many aspects of fleshy fruit development including fruit set, fruit size through the control of cell division and cell expansion, and fruit ripening. To shed light on the role of auxin fruit ripening, we have previously shown that Sl-ARF4 is a major player in mediating the auxin control of sugar metabolism in tomato fruit (cv MicroTom). Further extending this study, we show here that down-regulation of Sl-ARF4 in tomato alters some ripening-related fruit quality traits including enhanced fruit density at mature stage, increased firmness, prolonged shelf-life and reduced water (weight) loss at red ripe stage. These findings suggest that Sl-ARF4 plays a role in determining fruit cell wall architecture and thus providing a potential genetic marker for improving post-harvest handling and shelf life of tomato fruits.     

Light environment in pre- and post-dehiscent fruits affects seed germination in Calotropis procera

Fruits in Calotropis procera can be distinguished into five discrete but contiguous stages on the basis of diameter and seed color. Seeds from dehisced fruits at stage V germinated >80% on moist substratum in darkness. This was rather unexpected because the seeds developed and matured in an FR-enriched microenvironment (R:FR ratio ～0.3) of the chlorophyll-containing maternal tissue and displayed low-fluence response (LFR) mode of phytochrome action. In contrast to >80% dark-germinating seeds from dehisced fruits at stage V, about 50% seeds from undehisced fruits at that stage were dark germinating, whereas another 30% seeds required light for germination. The light-requiring fraction of the seed population did not only respond to a very low-fluence R and to a short FR pulse, but also lacked R–FR reversibility thereby indicating to a very low-fluence response (VLFR) mode of phytochrome action. The present study reporting VLFR to non-dormant seed state transition in C. procera suggested that the state of phytochrome and the subsequent seed germination response in dry-seeded species, besides being determined by the light environment immediately before maturation drying, might also be regulated by a post-dehiscence light signal.