Muscodor albus, a potential biocontrol agent against plant-parasitic nematodes of economically important vegetable crops in Washington State, USA

The fungus, Muscodor albus, was tested for nematicidal and nematostatic potential against four plant-parasitic nematode species with three different feeding modes on economically important vegetable crops in the Pacific Northwest. Meloidogyne chitwoodi, Meloidogyne hapla, Paratrichodorus allius, and Pratylenchus penetrans were exposed for 72 h to volatiles generated by M. albus cultured on rye grain in sealed chambers at 24 °C in the laboratory. In addition, the nematodes were inoculated into soil fumigated with M. albus, and incubated for 7 days prior to the introduction of host plants under greenhouse conditions. The mean percent mortality of nematodes exposed to M. albus in the chamber was 82.7% for P. allius, 82.1% for P. penetrans, and 95% for M. chitwoodi; mortality in the nontreated controls was 5.8%, 7%, and 3.9%, respectively. Only 21.6% of M. hapla juveniles died in comparison to 8.9% in controls. However, 69.5% of the treated juveniles displayed reduced motility and lower response to physical stimulus by probing, in comparison to the control juveniles. This is evidence of nematostasis due to M. albus exposure. The greenhouse study showed that M. albus caused significant reduction to all nematode species in host roots and in rhizosphere soil. The percent mortality caused by M. albus applied at 0.5% and 1.0% w/w in comparison to the controls was as follows: 91% and 100% for P. allius in the soil; 100% for P. penetrans in bean roots and soil; 85% and 95% for M. chitwoodi in potato roots, and 56% and 100% in the soil; 100% for M. hapla both in pepper roots and soil. In this study, M. albus has shown both nematostatic and nematicidal properties.     

荧光假单胞菌ZX对采后锦橙绿霉病的防治及其抑菌机制

【目的】采后柑橘极易受指状青霉(Penicillium digitatum)侵染而发生严重的绿霉病腐烂,生物防治因具有安全、有效、环保等特点近年来备受关注。论文旨在研究荧光假单胞菌(Pseudomonas fluorescens)ZX对采后柑橘绿霉病的防治效果,揭示P.fluorescensZX对P.digitatum可能存在的作用机制。【方法】以"北碚447"锦橙果实为试材,先分别接种20μL拮抗菌培养液、滤液(培养液离心后,上清经0.22μm滤膜过滤)、菌悬液(培养液离心后,菌体用无菌水反复洗涤并用无菌水重悬)和热杀死液(培养液高温高压灭菌),2 h后接种20μL P. digitatum孢子悬浮液(1×10~4spores/m L),所有果实于20oC、90%相对湿度环境下恒温恒湿培养8 d后,测定果实的发病率和病斑直径;制备柑橘皮培养基,进行平板抑菌试验,探索P. fluorescens ZX对P. digitatum孢子发芽情况的影响;采用两板对扣法和生物熏蒸法研究P.fluorescensZX挥发性次级代谢产物的抑菌作用;利用插入式细胞培养皿等分析P.fluorescensZX和P.digitatum之间竞争的营养物质;同时,测定P.fluorescensZX的生长曲线,利用结晶紫染色法评估P. fluorescens ZX的生物膜形成能力。【结果】P. fluorescens ZX不同处理液之间对采后锦橙绿霉病的作用效果差异显著,菌悬液抑菌效果最好,经菌悬液处理的果实,发病率和病斑直径分别仅为40.83%和1.78 cm;不论是在柑橘皮固体培养基上对峙培养还是在液体培养基中混合培养,菌悬液和原液的作用效果较好,固体平板上,相对抑制率达到了35%–45%,液体培养基中,P. digitatum孢子12 h后的发芽率不超过27%;P. fluorescens ZX产生的挥发性物质具有抑菌作用,经P. fluorescensZX熏蒸处理的锦橙果实,发病率和病斑直径都显著降低;营养竞争试验结果表明,P. fluorescens ZX能更快速有效地消耗柑橘皮培养基中的营养,并和P. digitatum竞争葡萄糖、果糖、蔗糖、天冬氨酸、苏氨酸、丝氨酸、亮氨酸、精氨酸和脯氨酸等营养物质;同时,P. fluorescens ZX生命力强,培养4 h后即进入对数生长期,约24 h后形成成熟的生物膜。【结论】P. fluorescens ZX可能通过抑制P. digitatum孢子发芽、营养与空间竞争、形成生物膜、产生抑菌物质等方式抑制P.digitatum的生长繁殖,有效防治采后锦橙绿霉病。     

A transcriptomic approach highlights induction of secondary metabolism in citrus fruit in response to <Emphasis Type="Italic">Penicillium digitatum</Emphasis>infection

Background  

Postharvest losses of citrus fruit due to green mold decay, caused by the fungus Penicillium digitaum, have a considerable economic impact. However, little is known about the molecular processes underlying the response of citrus fruit to P. digitatum.     

Biocontrol of Botrytis cinerea in apple fruit by Cryptococcus laurentii and indole-3-acetic acid

This study evaluated the effect of a yeast antagonist Cryptococcus laurentii and a plant regulator indole-3-acetic acid (IAA) on inhibition of Botrytis cinerea infection in harvested apple fruit. The results showed that the combined treatment with C. laurentii and IAA at 20 μg/ml was a more effective approach to reduce the gray mold rot in apple wounds than the C. laurentii alone. After 4 days of incubation, gray mold incidence in the combined treatment with C. laurentii and IAA was about 18%, which was a 50% reduction in incidence compared to the treatment with C. laurentii alone. Although IAA had no direct antifungal activity against B. cinerea infection when the time interval between IAA treatment and pathogen inoculation was within 2 h, application of IAA strongly reduced gray mold infection when IAA was applied 24 h prior to inoculation with B. cinerea in apple fruit wounds. Moreover, combination of IAA and C. laurentii stimulated the activities of superoxide dismutase, catalase and peroxidase with above 1.5-fold higher than that treatment with C. laurentii alone at 48 h. Therefore, combination of C. laurentii with IAA, which integrated the dual biological activity from the antagonistic yeast and plant regulator, might be developed to be a useful approach to control gray mold in harvested apple fruit.     

Effect of some essential oils on mycelial growth of <Emphasis Type="Italic">Penicillium digitatum</Emphasis> Sacc.

The antifungal action of four essential oils of Foeniculum vulgare (fennel), Thymus vulgaris (thyme), Eugenia caryophyllata (Clove) and Salvia officinalis (sage) was tested in vitro against Penicillium digitatum Sacc. Direct contact and vapour phase were used to test the antifungal activity of these essential oils against P. digitatum that is responsible for green mould rot of citrus fruits. The vapour phase and direct contact of clove and thyme essential oils exhibited the strongest toxicity and totally inhibited the mycelial growth of the test fungus. Thyme and clove essential oils completely inhibited P. digitatum growth either when added into the medium 600 μl l⁻¹ or by their volatiles with 24 μl per 8 cm diameter Petri dish. In in vitro mycelial growth assay showed fungistatic and fungicidal activity by clove and thyme essential oils. Sage and fennel oils did not show any inhibitory activity on this fungus. Scanning electron microscopy (SEM) was done to study the mode of action of clove oil in P. digitatum and it was observed that treatment with the oil leads to large alterations in hyphal morphology.     

Differential Induction of Proteins in Orange Flavedo by Biologically Based Elicitors and Challenged byPenicillium digitatumSacc.

The effects of biologically based inducing agents (elicitors) applied singly or in combination to harvested oranges were investigated for enhancing host resistance to green mold. Oranges (Citrus sinensiscv. ‘Valencia’) treated with inducing agents and challenged by the green mold pathogen (Penicillium digitatum) showed a delay in the onset and progression of disease symptoms compared with inoculated fruits not treated with the elicitors. Chitosan (a preparation of ground crab shells), Margosan-O (an oil-based plant-derived product from neem seed) + Aspire (a water dispersible granule containing an antagonistic yeast), Aspire, and chitosan + Aspire reduced fruit decay 38, 41, 42, and 44%, respectively. The inducing agents reduced disease incidence but not disease severity. Application of elicitors followed by inoculation withP. digitatumandP. digitatuminfection alone increased total soluble proteins in the flavedo (the tissue that forms the outer colored rind) twofold relative to the untreated control. The flavedo is an important tissue that is vulnerable to postharvest diseases especially at storage and transport of the harvested crop. No apparent qualitative differences were visualized in protein patterns analyzed by SDS–PAGE of all treatments across all days of incubation. A temporal differential induction of chitinase, β-1,3-glucanase, and peroxidase was demonstrated as a result of elicitor application followed by challenge inoculation withP. digitatum.Induction of these enzymes was corroborated by immunodetection. Lysozyme and a polygalacturonase-inhibiting protein were detected at low activity levels. However, the defensive proteins appeared to be constitutive and slightly induced but did not involve thede novosynthesis of novel proteins.     

Interactions among the entomopathogenic fungus, Beauveria bassiana (Ascomycota: Hypocreales), the parasitoid, Aphidius matricariae (Hymenoptera: Braconidae), and its host, Myzus persicae (Homoptera: Aphididae)

The effect of the entomopathogenic fungus Beauveria bassiana on the biological characteristics and life table of Aphidius matricariae, a parasitoid of the green peach aphid, Myzus persicae, was studied under laboratory conditions. Aphids were first infected with twice the LC₉₅ of B. bassiana for third-instar M. persicae (2 × 10⁸ conidia/ml). Subsequently, at different intervals they were exposed to 1-day-old mated parasitoid females for 24 h. The number of mummies produced per female and the percentage emergence of the F1 generation differed significantly as a function of the time interval between application of the fungus and exposure to the parasitoid. The interference of B. bassiana on parasitoid development was also studied by first exposing the aphid hosts to the parasitoid for 24 h and subsequently applying B. bassiana. The number of mummies produced by a female A. matricariae varied from 11.8 to 24.8 and was significantly different when the aphids were first exposed to the parasitoids and then treated with B. bassiana 24, 48, 72, and 96 h after exposure. There were no significantly different effects of B. bassiana on net reproductive rate (R₀), mean generation time (T), intrinsic rate (r_m) and the finite rate of increase (λ) of A. matricariae as a result of development in hosts exposed to low or high conidial concentrations (1 × 10², 2 × 10⁸ conidia/ml). The parasitoids developed in infected hosts had lower r_m, λ, T and DT (doubling time) values compared with those that developed in uninfected hosts but no differences were observed in R₀ values. With proper timing, A. matricariae and B. bassiana can be used in combination in the successful biological control of M. persicae.     

Supplementary Antimold Activity of Phosethyl AL, A New Brown Rot Fungicide for Citrus Fruits

Phosethyl Al (= Aliette) is a new and promising postharvest fungicide against brown rot of citrus fruits. Its effectiveness in controlling green mold (Penicillium digitaum), the major citrus fruit pathogen, was studied on artificially inoculated fruit and compared with that of sodium o-phenylphenate (SOPP) and thiabendazole (TBZ). In vitro and in vivo experiments have shown that phosethyl Al is capable — although to a lesser extent than SOPP and TBZ — of inhibiting growth of P. digitatum and reducing the incidence of decay of citrus fruits, caused by a wild-type, and apparently also by a benzimidazole-resistant strain of this fungus. The influence of times of treatment and modes of application (including temperature and duration of treatment, rinsing of the fruit) on the effectiveness of phosethyl Al, SOPP and TBZ in controlling green mold was studied and discussed. It is concluded that, under conditions of natural infection, phosethyl Al can be used for the postharvest control of Phytophthora-caused brown rot without any apparent increase in the incidence of green mold in the treated fruits.     

Biological control of crown rot of bananas with Pichia anomala strain K and Candida oleophila strain O

The antagonistic activity of two yeast strains (Pichia anomala (E.C. Hansen) Kurtzman, strain K and Candida oleophila Montrocher, strain O) against the parasitic complex responsible for banana crown rot was evaluated. The strains were applied at three different concentrations (10⁶, 10⁷, 10⁸ cfu/ml) and their efficacy tested in vivo on three separate fungi (Colletotrichum musae (Berk. & Curt.) Arx, Fusarium moniliforme Sheldon, and Cephalosporium sp.) and on a parasitic complex formed by association of these three fungi. At the concentrations used C. musae appeared to be the most pathogenic. The complex showed intermediate aggressiveness between C. musae and both other fungi.Statistically significant antagonistic effects were observed on C. musae, F. moniliforme, and the fungal complex. The highest protection level (54.4%) was observed with strain O added at 10⁸ cfu/ml on crowns previously inoculated with the fungal complex. The level was lower when the fungi were inoculated separately.Furthermore, the antagonistic effect was strongly reinforced when strain O at 10⁸ cfu/ml was applied 24 h before fungal complex inoculation (59.9%), as compared to its application 15 min (24.3%) or 3 h (27.3%) after fungal complex inoculation. Bananas showed increased susceptibility to the fungal complex from March to June, and this influenced the level of protection by yeast, which decreased over the same period. A strict negative correlation (R² = 0.83) was highlighted between susceptibility of banana to crown rot and protection provided by yeast.     

Change in susceptibility of satsuma mandarin fruit to sour rot pathogen (Geotrichum candidum citrus race) with relation to biochemical changes during maturation and storage

Change in susceptibility of satsuma mandarin fruit (Citrus unshiu) cultivar “Miyagawawase” to sour rot pathogen was studied with relation to biochemical changes during maturation and storage. The susceptibility of the fruit decreased with the advancement of maturity and was relatively constant during storage at 25°C for 4 wk. The young, green fruit that contained less total soluble solid, sugars and polyphenol, but more citric acid and water contents than mature, yellow fruit was more susceptible to sour rot pathogen. The susceptibility was correlated with total soluble solid, citric acid, sugars and water contents, but not with polyphenol. The results suggested that the difference in susceptibility during maturation was influenced to some extent by several constituents of fruit, although they may not be the only factors involved in susceptibility.     

Control of green mould of citrus by using Trichoderma harzianum,humic acid or garlic

Penicillium digitatum, an aggressive fungus causes post-harvest decay of mandarin sweet orange and Washington navel. In vitro Trichoderma harzianum or humic acid (HA) or powdered cloves of garlic caused inhibition of fungal growth of isolates P₁ and P₂. Under storage conditions, the fruit citrus is protected by using T. harzianum with standard volume 2.0?ml (9.6?×?10⁶?conidia/ml) and application 24?h before inoculation reduces disease incidence and disease severity after seven?days from inoculation with P. digitatum spore suspension (1.0?×?10⁶?spores/ml) compared to control. Spraying the fruit citrus by standard volume of 2.0?ml of either HA or powder cloves of garlic 1% on each fruit 24?h before inoculation reduces disease incidence and disease severity after seven?days from inoculation with P. digitatum (1.0?×?10⁶ spores/ml) compared to control. The lowest percentage of disease incidence and disease severity were associated with powder of cloves garlic and followed by HA and T. harzianum during two growing seasons compared with the untreated and control.     

Morphology and phylogeny of <Emphasis Type="Italic">Botryosphaeria dothidea</Emphasis> causing fruit rot of olives

The taxonomic position of the causal agent of fruit rot of olives was determined from fresh collections of the fungus from central Greece. In culture it formed two types of conidia, namely fusiform, hyaline, aseptate conidia typical of the genus Fusicoccum, and dark-walled, ovoid, ellipsoid or fusiform, 1–2 septate conidia that are not typically observed in Fusicoccum. A phylogenetic analysis based on ITS and EF1- sequences placed the fungus within the same clade as Fusicoccum aesculi, which is the anamorph of Botryosphaeria dothidea, and the type of the genus Fusicoccum.     

Biological control of brown rot (Moniliana laxa Ehr.) on apricot (Prunus armeniaca L. cv. Hacıhaliloğlu) by Bacillus, Burkholdria, and Pseudomonas application under in vitro and in vivo conditions

In 2002 and 2003, a study was conducted to determine the effect of bacterial strains, Burkholdria OSU 7, Bacillus OSU 142, and Pseudomonas BA 8, on biological control of brown rot disease (Monilinia laxa Ehr.) on apricot cv. Hacıhaliloğlu in Malatya province of Turkey. Apricot orchard at full blooming stage was inoculated with conidial suspension (1 × 10⁶ spores/ml) of M. laxa Ehr. After inoculation, two apricot trees for each application were treated with each of the three biological control agents (Burkholdria gladii OSU 7, Bacillus subtilis OSU 142, and Pseudomonas putida BA 8) by spraying (1 × 10⁹ cfu/ml) on inoculated branches. Disease incidence was evaluated for untreated (control 1) and four different treatment groups including commercial disease management (control 2, positive control: 3% Bourdox in fall, 50% Cupper at pink flower, 30 g/100 l Corus at first blooming, and 300 g/100 l Captan at last blooming stage) and treatments including each of the three bacterial strains (OSU 7, OSU 142, and BA 8). The results showed that disease incidence for negative control (control 1) was 9.94, which was significantly higher than disease incidence for commercial application (2.57%) or bacterial treatments (2.82–5.00%) in the first year. In 2003, the lowest disease incidence observed in OSU 7 treatment (6.80%), while disease incidence rate for positive control and negative control were 9.45% and 28.46%, respectively. This result may suggest that OSU 7 has potential to be used as biopesticide for effective management of brown rot disease on apricot.     

Use of organic acids and salts to control postharvest diseases of lemon fruits in Egypt

Abstract

Postharvest diseases caused by Geotricum candidum (sour rot), Penicillium digitatum (green mould), and P. italicum (blue mould) are the most important negative factors affecting handling and marketing of citrus fruits in Egypt. The effect of organic acids (ascorbic, benzoic, citric and sorbic) as well as organic salts (potassium sorbate and sodium benzoate) were evaluated on the growth of causal agents and their disease incidence under in vitro and in vivo conditions. Complete inhibition was observed in the linear growth of all tested fungi when exposed to benzoic, citric and sorbic organic acids at concentrations of 4% and 2% of either sodium benzoate or potassium sorbate, respectively. Minimizing the tested concentration of organic acid down to 2%, the tested fungi fluctuated in their response such that only benzoic and sorbic acids could completely inhibit the growth of either P. digitatum or P. italicum only. Different organic acids and salts showed various levels of either protective or therapeutic effect for coated lemon fruits against mould infection whatever the time of their artificial inoculation under in vivo conditions. All treated fruits showed reduction in sour rot and green and blue mould diseases when compared with untreated fruits. Complete inhibition of mould incidence was obtained in coated lemon fruits with 4% of water or wax mixtures of sodium benzoate and potassium sorbate 24 hours before inoculation. Also, high reduction in mould incidence was observed in lemon fruits coated with the same concentration at 48 hours after inoculation under the same conditions. On the other hand, the tested organic acids showed a lesser effect on mould incidence. Moreover, they were more effective against mould incidence when dissolved in water than wax, that only 4% of water mixture of sorbic and benzoic acids showed 100% protection against mould incidence. Furthermore, the severity of infection records followed the same trend. The present findings demonstrate that potassium sorbate and sodium benzoate have potential as environmentally friendly products, nontoxic postharvest fungicides against sour rot, green and blue mould incidence of stored citrus fruits and could be suggested for commercial use in packing-houses in consideration to their wide consumption as safely food preservatives.     

A <Emphasis Type="Italic">Colletotrichum gloeosporioides</Emphasis>-induced esterase gene of nonclimacteric pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis>) fruit during ripening plays a role in resistance against fungal infection

Ripe fruits of pepper (Capsicum annuum) are resistant to the anthracnose fungus, Colletotrichum gloeosporioides, whereas unripe-mature fruits are susceptible. A pepper esterase gene (PepEST) that is highly expressed during an incompatible interaction between the ripe fruit of pepper and C. gloeosporioides was previously cloned. Deduced amino acid sequence of PepEST cDNA showed homology to both esterases and lipases, and contained -HGGGF- and -GXSXG- motifs and a catalytic triad. Inhibition of PepEST activity by a specific inhibitor of serine hydrolase demonstrated that a serine residue is critical for the enzyme activity. Expression of PepEST gene was fruit-specific in response to C. gloeosporioides inoculation, and up-regulated by wounding or jasmonic acid treatment during ripening. PepEST mRNA and protein was differentially accumulated in ripe vs. unripe fruit from 24 h after inoculation when C. gloeosporioides isinvading into fruits. Immunochemical examination revealed that PepEST accumulation was localized inepidermal and cortical cell layers in infected ripe fruit, but rarely even in epidermal cells in infected unripe one. Over-expression of PepEST in transgenic Arabidopsis plants caused restriction of Alternaria brassicicola colonization by inhibition of spore production, resulting in enhanced resistance against A.brassicicola. These results suggest that PepEST is involved in the resistance of ripe fruit against C.gloeosporioides infection.^†These authors contributed equally to the work     

Biocontrol of a root rot of kale by <Emphasis Type="Italic">Muscodor albus</Emphasis> strain MFC2

Pythium ultimum is an oomycetous root rot pathogen that causes significant crop production losses on many crops including kale (Brassica oleracea), an economically important vegetable in Thailand. An endophytic fungus from Thailand designated Muscodor albus MFC2 controlled P. ultimum both in vitro and on kale seedlings grown under outdoor conditions via the production of volatile antibiotics. Ten-day old M. albus MFC2 PDA cultures killed P. ultimum in vitro. Thoroughly mixing three PDA plates of 10-day old M. albus MFC2 into a 500 g mixture of commercial soil and field soil did not adversely affect kale seed germination. The same amount of M. albus MFC2 could restore seedling emergence in P. ultimum inoculated soil to a level close to that of a non-infested control. In addition, M. albus MFC2 did not cause any disease symptoms, but rather seemed to promote the growth of kale in the presence or absence of P. ultimum for up to eight weeks after planting.     

Effectiveness of honey bees in delivering the biocontrol agent Bacillus subtilis to blueberry flowers to suppress mummy berry disease

Honey bees are important pollinators of commercial blueberries in the southeastern United States, and blueberry producers often use supplemental bees to achieve adequate fruit set. However, honey bees also vector the plant pathogenic fungus Monilinia vaccinii-corymbosi which infects open blueberry flowers through the gynoecial pathway causing mummy berry disease. Here, we report the results of a 3-year field study to test the hypothesis that using bee hives equipped with dispensers containing the biocontrol product Serenade, a commercial formulation of the bacterium Bacillus subtilis which has shown activity against flower infection by M. vaccinii-corymbosi in laboratory experiments, can reduce mummy berry disease incidence when honey bees are used as pollinators in blueberries. Individual honey bees carried 5.1–6.4 × 10⁵ colony-forming units (CFU) of B. subtilis when exiting hive-mounted dispensers with Serenade. On caged rabbiteye blueberry bushes in the field, population densities of B. subtilis vectored by honey bees reached a carrying capacity of <10³ CFU per flower stigma within 2 days of exposure, and there was a highly significant non-linear relationship between B. subtilis populations per stigma and bee activity, expressed as number of legitimate flower visits per time interval per cage (R = 0.6928, P < 0.0001, n = 32). Honey bee density (1600 or 6400 individuals per 5.8-m³ cage) and Serenade treatment (presence or absence of the product in hive-mounted dispensers) significantly (P < 0.05) affected the incidence of fruit mummification on caged bushes, whereby increasing bee density increased disease incidence and application of Serenade reduced disease levels. Taken together, results of this study suggest that use of a hive-dispersed biocontrol product such as Serenade as a supplement during pollination can reduce the risk of mummy berry disease. This may be a prudent practice that optimizes the benefits to pollination of high bee densities while reducing the associated disease-vectoring risk.     

Effect of cultural methods on leaf spot (<Emphasis Type="Italic">Mycosphaerella fragariae</Emphasis>) and gray mold (<Emphasis Type="Italic">Botrytis cinerea</Emphasis>) damage in strawberries

Damage of leaf spot, caused by Mycosphaerella fragariae and gray mold also called Botrytis fruit rot, caused by Botrytis cinerea, average fruit weight and yield were evaluated with regard to cultural methods over 2years. Leaf spot damage decreased significantly by around 90% due to leaf sanitation (removal of dead and leaf spot infected leaves in early spring) and by 50% due to plantation in a one-row-system instead of a two-row-system. When all leaves including the healthy green ones were removed in early spring, average fruit weight decreased significantly by 10%. Fruit sanitation – the third treatment – did not influence any of the measured parameters. Neither leaf sanitation nor fruit sanitation (removal of damaged fruits during harvest) reduced B. cinerea damage significant. Only the combination of a one-row-system, leaf sanitation and fruit sanitation almost halved (not significantly) B. cinerea damage in the first crop year compared to a two-row-system without leaf and fruit sanitation. B. cinerea damage correlated significantly and positively with the biomass of plants by R²= 0.47. According to this study and the cited literature it is suggested for humid Central European conditions to apply a one-row-system combined with leaf sanitation in early spring and fruit sanitation during harvest if fruit density is high, to reduce the risk of damages in larger dimension caused by M. fragariae and B. cinerea.     

Chitosan and hot water treatments reduce postharvest green mould in ‘Murcott’ tangor

This study aims to evaluate the efficacy of hot water and chitosan treatments to control green mould caused by Penicillium digitatum in 'Murcott' tangor. P. digitatum conidial germination and mycelial growth were evaluated in assays in vitro to verify whether chitosan (0.5, 1 and 2%) or hot water (45, 50, and 55°C, for 30 s, 1, 2, and 5 min) acts directly on fungus development. In vivo assays consisted of inoculating the fruit with P. digitatum (10⁵ conidia ml⁻¹) 4 hr before the chitosan and hot water treatments. Subsequently, green mould incidence and severity were evaluated in fruits stored at 25°C/80% RH for 4 days. Also, treatments combining chitosan and hot water were investigated for controlling green mould and the effect on postharvest quality of fruit stored at 5°C/90% RH. The results showed that P. digitatum conidia germination and mycelial growth were significantly reduced by the hot water treatments especially at 50°C/5 min and 55°C/2 or 5 min in the first case and 50 and 55°C/5 min in the second. These two treatments, when applied alone, 1 min dipping in 2% chitosan or hot water at 50°C/5 min, significantly reduced green mould development in fruit kept at 25°C/80% RH or refrigerated. However, the hot water dip combined with chitosan did not improve green mould control on ‘Murcott’ tangor at room temperature or under refrigeration. Besides, chitosan and hot water did not impair fruit quality. Thus, chitosan and hot water could be an alternative to synthetic fungicides to control green mould in citrus while also contributing to a decrease in the postharvest losses of ‘Murcott’ tangor.     

Trichoderma theobromicola and T. paucisporum: two new species isolated from cacao in South America

Trichoderma theobromicola and T. paucisporum spp. nov. are described. Trichoderma theobromicola was isolated as an endophyte from the trunk of a healthy cacao tree (Theobroma cacao, Malvaceae) in Amazonian Peru; it sporulates profusely on common mycological media. Trichoderma paucisporum is represented by two cultures that were obtained in Ecuador from cacao pods partially infected with frosty pod rot, Moniliophthora roreri; it sporulates sporadically and most cultures remain sterile on common media and autoclaved rice. It sporulates more reliably on synthetic low-nutrient agar (SNA) but produces few conidia. Trichoderma theobromicola was reintroduced into cacao seedlings through shoot inoculation and was recovered from stems but not from leaves, indicating that it is an endophytic species. Both produced a volatile/diffusable antibiotic that inhibited development of M. roreri in vitro and on-pod trials. Neither species demonstrated significant direct in vitro mycoparasitic activity against M. roreri.