STUDIES ON GLOEOSPORIUM MUSARUM CKE. AND MASSEE CAUSING STORAGE ROTS OF JAMAICAN BANANAS

Experimental inoculations indicate that several factors may influence the extent to which anthracnose, caused by Gloeosporium musarum , develops on bananas following wound-infection. Severity of disease increases with increasing 'grade' of maturity, 'full' fruit being more seriously affected than 'thin' fruit. The evidence suggests that Gros Michel fruit is less susceptible to this form of rot than fruit of the Lacatan or Robusta varieties. The amount of Gloeosporium -rot on fruit imported into the United Kingdom undergoes marked seasonal variation, being greatest during autumn and winter.
The presence of perforated 'Polythene' bags during cold storage (55° F.) appears to favour slightly the development of disease. Bagging had no significant effect on rotting during the subsequent ripening period. After wound-inoculation, disease incidence and severity decreased appreciably with increasing periods of storage at tropical temperatures (76–87° F.). Such a decrease was evident even when the humidity at the surface of the fruit was maintained at a high level (92–100%).
In several shipping trials, a post-harvest fruit-dip treatment with nystatin (200–400 p.p.m.) effected 40–70% control of anthracnose.     

STUDIES ON GLOEOSPORIUM MUSARUM CKE. & MASSEE CAUSING STORAGE ROTS OF JAMAICAN BANANAS

Gloeosporium musarum Cke. & Massee is the most important fungus associated with finger-stalk rot of Jamaican Lacatan bananas, Fusarium spp. being of minor importance. Sodium salicylanilide (Shirlan WS), at concentrations of 0.5, 1.0 and 1.5%, provided approximately 30, 50 and 65% control, respectively, when inoculated fruit was dipped for 1 min. in the compound: severe phytotoxic effects were caused by all concentrations. When Shirlan WS treatment was followed by rinsing in water, there were no phytotoxic effects and approximately 15, 35 and 40% control of finger-stalk rot, respectively, was obtained. 1.0 and 1.5% Shirlan WS also effected good control of anthracnose ( G. musarum ), both with and without post-treatment washing.
Moderate to poor control of Gloeosporium rot was obtained when Shirlan WS/washing treatment was delayed for more than 24 hr. after inoculation. A 2 min. immersion period in Shirlan WS was more effective than shorter periods: a momentary dip was ineffective.
The antibiotic nystatin (200 and 400 p.p.m.) had no significant effect on the incidence of finger-stalk rot: also, the severity of main-stalk rot was not reduced appreciably.
Practical considerations arising from the possibility of commercial-scale treatment with Shirlan WS are discussed.     

The antagonistic effect and mechanisms of Bacillus amyloliquefaciens DGA14 against anthracnose in mango cv. ‘Carabao’

Bacillus amyloliquefaciens strain DGA14 was tested for in vitro antagonism towards Colletotrichum gloeosporioides, a causal pathogen of anthracnose in mango cv. ‘Carabao’. DGA14 produced extracellular metabolites in solid and liquid media that suppressed the growth of C. gloeosporioides. The cells of DGA14 were often observed adjacent to the pathogen so affecting its spore germination and mycelium development. DGA14 colonised mango fruit 48 h after artificial inoculation and persisted 14 days after storage at 18–20°C. On fruit surfaces, DGA14 attached and produced dents to spores of C. gloeosporioides. Dipping mangoes in aqueous cell suspension (10⁸ mL L^?1) of DGA14 significantly decreased the incidence of anthracnose as compared to untreated fruit.     

Freckle disease of banana in Hawaii caused by Phyllostictina musarum (Cke.) Petr

‘Freckle’ (‘black-spot’ disease) of bananas is common on leaves and fruit of Dwarf Cavendish and other varieties in Hawaii, especially after rainy periods. On fruit, symptoms may appear 2–4 weeks after the bunch has opened, and become more severe as maturity is approached. The disease is usually confined to older leaves on affected plants. Freckled tissue contains numerous pycnidia of Phyllostictina musarum and disease was experimentally induced by inoculating leaves and fruit with conidia of this fungus. This appears to be the first record of successful inoculation with P. musarum. Conidia of P. musarum germinate after 3–6 h in a film of water on banana peel, appressoria being formed after 18–30 h. Penetration of the epidermis occurs 24–96 h after inoculation, and is brought about by an infection hypha which grows from the appressorium. The progressive increase in severity of freckle as fruit matures is due to repeated infection by further conidia of P. musarum, rather than to enlargement of original infections. Some banana clones, including Gros Michel, appear to be resistant to the fungus Dispersal of P. musarum conidia immediately after discharge from the pycnidium is chiefly by rainwater and dew. Secondary infections contribute greatly to the total number of infections. Conidium dispersal by water often results in the development of characteristic patterns of spotting, chiefly in the form of streaks or circular areas, coinciding with the directions of movement of rainwater and dew. Large numbers of conidia of P. musarum are washed on to fruit in rainwater and dew running from diseased, overhead leaves.     

Changes during low-oxygen storage in the effects of ethylene on induction of ethylene synthesis and stimulation of respiration of 'Gloster 69' apples

The ability of ethylene to stimulate respiration and advance the onset of rapid ethylene production was investigated at different times during storage of 'Gloster 69' apples in 2 kPa O₂ at 1.5–3.5°C. Ethylene stimulated respiration in apples at 15°C immediately after harvest; maximal rates were recorded at 10–1000 μl I⁻¹ but attainment of these rates was delayed after low O₂ storage until day 3 of treatment at 15°C. The onset of rapid ethylene production at 15°C occurred later in non-ethylene-treated apples after storage than after harvest. Ethylene production was induced in some apples during ethylene treatment for 3 or 6 days; in others it was induced about 20 days after treatment, but a proportion of the fruit showed no induction in the 45-day duration of experiments. An ethylene treatment at 10 μl I⁻¹ led to a near maximal increase in the frequency of induction of ethylene production at all times. After storage apples were mainly induced during treatment or not induced, whereas after harvest induction after treatment was more frequent. The presence of 2000 μl l⁻¹ norbornadiene during ethylene treatment inhibited the stimulation of respiration and the induction of ethylene production; this inhibition was only partly reversed by ethylene at 1000 μl l⁻¹ the experiments suggest that receptors for ethylene were present at all stages but that response capacity changed during storage.     

The Establishment and Structure of Latent Infections with Monilinia fructicola on Apricots

Latent infections of apricot fruit with Monilinia fructicola were initiated by inoculation at shuck fall and 43 and 63 days after shuck fall. The fungus entered via the stomata and penetrated a guard cell through the thin walled region at the stomatal pore. The fruit tissue responded by death of cells around the point of infection, suberization of walls of surrounding living cells and accumulation o phenolic compounds in cells up to 20 distant. Periderm developed around lesions formed at shuck fall but was absent from those formed 65 days later. When the fruit ripened, approximately 100 days after shuck fall, viable hyphae in latent infections escaped from the lesions by growing out between the cuticle and epidermis or just below the epidermal cells. Outbreak was more efficient from later inoculations and only a small proportion of latents initiated at shuck fall became invasive.     

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.     

The use of the bacteriocin, nisin, as a preservative in ricotta-type cheeses to control the food-borne pathogen Listeria monocytogenes

The efficacy of nisin to control the food-borne pathogen Listeria monocytogenes in ricotta-type cheeses over long storage (70 d) at 6–8°C was determined. Cheeses were prepared from unpasteurized milk by direct acidification with acetic acid (final pH 5·9) and/or calcium chloride addition during heat treatment. Nisin was added in the commercial form of Nisaplin^® pre-production to the milk. Each batch of cheese was inoculated with 10²–10³ cfu g⁻¹ of a five-strain cocktail of L. monocytogenes before storage. Shelf-life analysis demonstrated that incorporation of nisin at a level of 2·5 mg l⁻¹ could effectively inhibit the growth of L. monocytogenes for a period of 8 weeks or more (dependent on cheese type). Cheese made without the addition of nisin contained unsafe levels of the organism within 1–2 weeks of incubation. Measurement of initial and residual nisin indicated a high level of retention over the 10-week incubation period at 6–8°C, with only 10–32% nisin loss.     

The infection of apples by Phytophthora syringae

Contamination with infected soil has led to high wastage of apples in storage due to rotting by Phytophthora syringae. At 3-3 ^oC lesions formed 3–4 wk after inoculation with zoospores; the percentage infection fell if the suspensions dried after 48 h at this temperature and after 22 h at 15 ^oC. Infected soil rotted fruit only if kept moist; at 3-3 ^oC a 3-day period of wetness resulted in 37-5% rotting after 8 wk. Fruit dipped in soil slurry remained wet in some parts of a 4361(12 bushel) bin for at least 3 wk. There was a 10-fold increase in rotting by contact between sound and rotting fruit after 11 wk at 3-3 ^oC. Captan gave effective protection against rotting derived from zoospores or infected soil; it had no eradicant action.     

Induction of Enzymes and Phenolic Compounds Related to the Natural Defence Response of Netted Melon Fruit by a Bio-elicitor

Fungal disease in netted melon fruit is an important factor affecting their postharvest quality and therefore an important cause of large economic losses around the world. Among the alternatives to control fungal diseases, the induction of the natural defence response (NDR) in fruits is promising. The objective of this study was to induce the NDR in netted melon treated with a bio-elicitor formulated from Fusarium oxysporum growth in a potato dextrose agar enriched with netted melon skin. Netted melon fruits (cv 'Primo') were not treated (C), untreated and inoculated with F. oxysporum (IN), treated with a bio-elicitor (FES), or treated with the bio-elicitor and inoculated (FES + IN). After treatments, fruits were stored for 8 days at 20°C with 90–92% relative humidity. Melon was sampled every 2 days at 20°C to evaluate the development of Fusarium rot symptoms as disease index percentage (DI), changes in phenolic compounds, changes in phenylalanine ammonia-lyase (PAL) activity, chitinase activity (ChA) and β-1,3-glucanase activity (GA). It was found that DI in netted melon fruit was significantly reduced in the FES + IN as compared with the IN treatment. FES + IN and FES treatments showed the highest increase of phenolic acids. Higher levels of PAL activity were observed in the treatments IN, FES, and FES + IN with respect to C, after 4 days of storage. A large increase in ChA activity was observed in the treatments IN, FES and FES + IN after 6 days of storage. No differences in GA activity were found among FES, FES + IN and C treatments throughout storage. IN treatment showed the highest increase in GA activity after 4 days of storage. It is concluded that the bio-elicitor activates the NDR as measured by the increase in phenolic acids synthesis, PAL and ChA enzymes activity, in a similar way as the infection by the living pathogen.     

Cell-mediated immunity to Friend virus-induced leukemia. II. Characteristics of primary cell-mediated cytotoxic response.

The primary cell-mediated cytotoxic response to a Friend virus-induced leukemia, FBL-3, in C57BL/6 mice was measured by the 125IUdR release assay. Intraperitoneal (i.p.) inoculation of 1 x 10(1) FBL-3 cells produced progressive tumor growth (progressors); subcutaneous (s.c.) inoculation of as many as 5 x 10(6) FBL-3 cells produced only transient tumor growth (regressors), and these mice would subsequently resist i.p. challenge of FBL-3 cells at 3 days after s.c. inoculation. The kinetics of the primary cell-mediated cytotoxic response of regressors was biphasic. Significant cytotoxicity could be detected at 3 to 5 days after s.c. inoculation of 5 x 10(6) FBL-3 cells peaked at days 10 to 14, declined to a very low level or became undetectable around days 20 to 30; then the reactivity reappeared and persisted at least up to 60 days. In progressors, the kinetics of the cell-mediated cytotoxic response was similar to the regressors, but the reactivity was much lower. The cytotoxic response was found to be T cell dependent, during both the first peak (days 10 to 14) and the second peak (days 40 to 60). In adoptive transfer experiments, lymphocytes from regressors gave 90% protection against i.p. challenge of FBL-3; lymphocytes from progressors only gave 40% protection.     

Increased Uric Acid in the Developing Brain and Spinal Cord Following Cytomegalovirus Infection

Abstract: Tissue concentrations of uric acid were determined in the spinal cord, cerebellum, caudate-putamen, and cerebral cortex of developing mice following intraventricular inoculation with murine cytomegalovirus (MCMV) on postnatal day 10. Transient signs of neurological impairment were observed in MCMV-infected animals beginning on days 13–16 and continuing until days 19–21. At the onset of neurological impairment, uric acid concentrations in tissues from infected animals were 17–60-fold greater than in control animals. On postnatal day 70, 60 days after inoculation and 40 days after resolution of neurological signs, uric acid levels were still two- to threefold greater in infected animals. Histological examination revealed signs of focal ischemia in the cerebral and cerebellar cortices of MCMV-infected mice only at the onset of neurological impairment, with ischemic cell changes in some pyramidal neurons of the cerebral cortex. These results indicate that uric acid may be a sensitive marker of persistent vascular pathology resulting from cytomegalovirus infection of the developing nervous system     

Chilling Injury,Physicochemical Properties,and Antioxidant Enzyme Activities of Red Pitahaya (<i>Hylocereus polyrhizus</i>) Fruits under Cold Storage Stress

Low-temperature storage is extensively used to optimize the postharvest life of various fresh fruits. However, red pitahaya (Hylocereus polyrhizus) fruits are sensitive to chilling injury (CI), which leads to the limitation of low-temperature storage. In this study, red pitahaya fruits were stored at 2, 4, 6, 8, and 10°C, respectively, for 27 days to determine the appropriate storage temperature. During the storage of red pitahaya fruits, storage at 8°C was more effective in suppressing decay and maintaining quality than other low temperatures. Low-temperature (2, 4, and 6°C) storage decreased weight loss (WL) and maintained higher content of titratable acidity (TA), soluble sugars (SS), and total phenolics (TP) but different degrees of CI were detected. No CI was observed at 8°C and 10°C. Red pitahay as stored at 8 and 10°C were associated with better color evaluation, lower electrolyte leakage (EL), respiration rate, and lipoxygenase (LOX) activity, and higher fruit firmness, superoxide dismutase (SOD) activity, and catalase (CAT) activity. However, higher storage temperature (10°C) resulted in higher metabolic activity leading to lower quality and antioxidant capacities compared with 8°C. Therefore, our results demonstrated that red pitahaya stored at 8°C exhibited a protective effect on fruit quality and resisted CI development during storage.     

Surface Survival and Internalization of Salmonella through Natural Cracks on Developing Cantaloupe Fruits,Alone or in the Presence of the Melon Wilt Pathogen Erwinia tracheiphila

Outbreaks of foodborne illness attributed to the consumption of Salmonella-tainted cantaloupe have occurred repeatedly, but understanding of the ecology of Salmonella on cantaloupe fruit surfaces is limited. We investigated the interactions between Salmonella enterica Poona, the plant pathogenic bacterium Erwinia tracheiphila, and cantaloupe fruit. Fruit surfaces were inoculated at the natural cracking stage by spreading S. enterica and E. tracheiphila, 20 µl at 10⁷ cfu/ml, independently or together, over a 2×2 cm rind area containing a crack. Microbial and microscopic analyses were performed at 0, 9 and 24 days post inoculation (DPI). Even at 24 DPI (fruit maturity) S. enterica was detected on 14% and 40% of the fruit inoculated with S. enterica alone and the two-pathogen mixture, respectively. However, the population of S. enterica declined gradually after initial inoculation. E. tracheiphila, inoculated alone or together with Salmonella, caused watersoaked lesions on cantaloupe fruit; but we could not conclude in this study that S. enterica survival on the fruit surface was enhanced by the presence of those lesions. Of fruit inoculated with E. tracheiphila alone and sampled at 24 DPI, 61% had watersoaked lesions on the surface. In nearly half of those symptomatic fruits the watersoaking extended into the sub-rind mesocarp, and E. tracheiphila was recovered from that tissue in 50% of the symptomatic fruit. In this work, E. tracheiphila internalized through natural cracks on developing fruits. S. enterica was never detected in the fruit interior (ca. 2–3 mm below rind surface) under the limited conditions of our experiments, but the possibility that it, or other human pathogens that contaminate fresh produce, might also do so should be investigated under a wider range of conditions and produce types.     

Activity of trans-2-hexenal against Penicillium expansum in 'Conference' pears

AIMS: To investigate the effects of trans-2-hexenal on blue mould disease, patulin content and fruit quality in 'Conference' pears. METHODS AND RESULTS: Fruits, wounded and inoculated with Penicillium expansum or non-inoculated, were exposed to trans-2-hexenal vapour treatment (12.5 microl l(-1)) at 20 degrees C. A greater reduction of decay was obtained by treatment application 24 or 48 h after inoculation, in contrast trans-2-hexenal application 2 h after inoculation was ineffective. Fruit storage temperature (-1 degrees C) after treatment did not affect the antifungal activity. Although 2-h exposure to trans-2-hexenal was effective in reducing blue mould, an exposure of at least 8 h was required to reduce fruit patulin content. Treatments did not affect fruit physical-chemical characteristics. After 6 days at 20 degrees C following exposure, trans-2-hexenal residue in treated fruits was less than the natural content of the compound in unripe fruits. CONCLUSIONS: trans-2-Hexenal treatment is effective in the reduction of blue mould infections and patulin content in Conference pears when applied 24-48 h after pathogen inoculation. SIGNIFICANCE AND IMPACT OF THE STUDY: trans-2-Hexenal could be a natural alternative to fungicides in the control of P. expansum infections. Further work is needed to study the methods and conditions avoiding the persistence of off-odours and off-flavours in pears after their exposure to trans-2-hexenal vapours.     

Enhanced tolerance to bacterial pathogens caused by the transgenic expression of barley lipid transfer protein LTP2

Purified lipid transfer protein LTP2 from barley applied on tobacco leaves eliminated symptoms caused by infiltration of Pseudomonas syringae pv. tabaci 153. Growth of the pathogen in leaves of transgenic tobacco plants was retarded when compared with non-transformed controls. The percentage of inoculation points that showed necrotic lesions was greatly reduced in transgenic tobacco 17–38% versus 78%) and the average size of these lesions was 61–81% that of control. The average total lesion area (necrosis and chlorosis) in the transgenic plants was also reduced (38% of control). Arabidopsis thaliana transgenic plants inoculated with P. syringae pv. tomato DC3000 also had lower percentages of necrotic lesions (22–38% versus 76%), a reduced average area for each lesion (53–67% of control), and a smaller total lesion area per inoculation (43% of control). These results further support the assignment of a defense role for LTPs and highlight their biotechnological potential.     

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Remobilization of fructans in Phippsia algida during rapid inflorescence development

Plants of Phippsia algida (Sol.) R. Br. were cultivated in short days (SD; 8 h summer daylight) and in long days (LD; 8 h summer daylight + 16 h low irradiance extension of 5 μmol m⁻² s⁻¹) at 9, 15, and 21°C. In this plant, inflorescence primordia are initiated in both LD and SD, but LD are required for heading and inflorescence development (Heide, O.M.; Physiol. Plant. 85: 606–610. 1992). Total dry matter production was slightly increased by LD over SD at 9°C, while it was little affected by daylength at 15 and 21°C. Phippsia algida contained mainly fructans with a low degree of polymerization, largely of the kestose series. After 29 to 42 days (depending on the temperatature) of photoperiodic treatment, fructans constituted 15–20 percent of dry mass of SD-grown plants compared with only 2–3 percent of dry mass for LD-grown flowering plants. There was no difference due to photoperiod in levels of mono- and disaccharides. Shifting the SD-grown plants to LD conditions resulted in rapid inflorescence development, accompanied by a parallel rapid decrease in the fructan level, while the level of mono- and disaccharides remained constant. The results show that fructans are important as storage carbohydrates in the late snow-bed species P. algida that normally requires several growing seasons for completing its life cycle. Exhaustion of this storage pool during the extremely fast flower and fruit development constitutes an essential part of the plants adaption to a very short growing season.