Fruit Rot Fungi Research Articles

Morphological and Molecular Characterization of Pomegranate Fruit Rot Pathogen, Chaetomella raphigera, and its Virulence Factors.

A new fungal pathogen was isolated from rotten pomegranates collected from the orchards of different parts of Maharashtra. The pathogen was morphologically identified as Chaetomella raphigera followed by sequencing of ITS and D1/D2 hypervariable region of LSU (28S) of rRNA gene. The pathogen produced pectinase, cellulase, xylanase and protease in liquid medium at a concentration of 71, 13.8, 54.3 and 7 U/ml respectively. Enzyme activity was also determined during pathogenesis in the tissues artificially infected by C. raphigera. Xylanase activity was maximum (25.1U/g) followed by pectinase (19.2U/g) and cellulase (1.5U/g), whereas, protease activity was unnoticed. There was significant correlation (P<0.05) between disease rating scale and pectinase, xylanase and cellulase activity in infected tissues. This indicates the simultaneous production of hydrolytic enzymes that aids in necrosis of fruit tissues. The elevated levels of these enzymes in infected tissues as compared with control suggest their possible role in pathogenesis. Thus, pectinase, cellulase and xylanase produced by C. raphigera acts as major virulence factors in the development of fruit rot in pomegranates. This is a first report of fungal fruit rot caused by C. raphigera in pomegranate.

Interactions between cranberries and fungi: the proposed function of organic acids in virulence suppression of fruit rot fungi.

Cranberry fruit are a rich source of bioactive compounds that may function as constitutive or inducible barriers against rot-inducing fungi. The content and composition of these compounds change as the season progresses. Several necrotrophic fungi cause cranberry fruit rot disease complex. These fungi remain mostly asymptomatic until the fruit begins to mature in late August. Temporal fluctuations and quantitative differences in selected organic acid profiles between fruit of six cranberry genotypes during the growing season were observed. The concentration of benzoic acid in fruit increased while quinic acid decreased throughout fruit development. In general, more rot-resistant genotypes (RR) showed higher levels of benzoic acid early in fruit development and more gradual decline in quinic acid levels than that observed in the more rot-susceptible genotypes. We evaluated antifungal activities of selected cranberry constituents and found that most bioactive compounds either had no effects or stimulated growth or reactive oxygen species (ROS) secretion of four tested cranberry fruit rot fungi, while benzoic acid and quinic acid reduced growth and suppressed secretion of ROS by these fungi. We propose that variation in the levels of ROS suppressive compounds, such as benzoic and quinic acids, may influence virulence by the fruit rot fungi. Selection for crops that maintain high levels of virulence suppressive compounds could yield new disease resistant varieties. This could represent a new strategy for control of disease caused by necrotrophic pathogens that exhibit a latent or endophytic phase.

Biological control of toxigenic citrus and papaya-rotting fungi by Streptomyces violascens MT7 and its extracellular metabolites.

An Indian indigenous, Loktak Lake soil isolate Streptomyces violascens MT7 was assessed for its biocontrol potential both in vitro and in vivo against toxigenic fruit-rotting fungi. Strain MT7 exhibited broad-spectrum antifungal activity against various pathogenic postharvest fungi of citrus and papaya. In shake-flask fermentation, antagonist S. violascens MT7 highly produced extracellular antifungal metabolites in early stationary growth phase in glucose-yeast extract-malt extract (M93) broth. Both extracellular culture fluid (ECF) and its n-butanol extract showed significant broad-spectrum fungal mycelial inhibition of several tested fruit-rotting fungi. Antifungal metabolite was found to be heat stable, nonpeptidic, and polyene type antibiotic. The lowest minimum inhibitory concentration (MIC) of n-butanol extract against Colletotrichum gloeosporioides MTCC 9664 and Aspergillus niger MTCC 281 was 0.0312 and 0.0625 mg/ml, respectively. Purification of n-butanol extract through silica gel chromatography resulted in partial purification of bioactive metabolite and the TLC autobiography revealed the presence of single antifungal metabolite with Rf value of 0.755. In vivo bioassays demonstrated the biocontrol potential of tested biocontrol agents on fruit-rotting fungi. Use of cell suspension of S. violascens MT7, extracellular metabolite(s), and n-butanol extract significantly (p < 0.05) reduced sour-rot development on Citrus reticulata Blanco (oranges) and soft-rot development on papaya fruits. Therefore, these results strongly suggest a high potential for application of S. violascens MT7 and its extracellular metabolites as an effective eco-friendly alternative to synthetic fungicides for controlling toxigenic citrus and papaya-rotting fungi.

Growth Inhibition Potentials of Leaf Extracts from Four Selected Euphorbiaceae against Fruit Rot Fungi of African Star Apple (Chrysophyllum albidum G. Don)

The efficacy of ethanolic leaf extracts from Phyllanthus amarus, Euphorbia hirta, Euphorbia heterophylla and Acalypha fimbriata in inhibiting the growth of post-harvest fruit rot fungi of Chrysophyllum albidum was investigated at the concentrations of 100, 80, 60 40 and 20 mg/ml in-vitro. The fungi isolated from rotted fruits and their frequency of occurrence includes Aspergillus niger (69.6%) and Fusarium solani (30.4%). These fungal isolates were cultured on different leaf extracts agar and their radial mycelia growth was observed. The antifungal activities increased with increase in concentrations of the plant extracts with E. heterophylla extract most effective in inhibiting the growth of A. niger while A. fimbriata extract was more effective in the inhibition of F. solani than other extracts. Phytochemical screening of the plant extracts revealed the presence of saponins, alkaloids, glycosides, terpenes, steroids, flavonoids, tannins and phenols. Gas Chromatography Mass Spectrometry (GC-MS) analysis revealed the presence a complex mixture of constituents ranging from 7 compounds in E. hirta, 10 compounds in A. fimbriata, 11 compounds in E. heterophylla and 14 compounds in P. amarus. The result of this study is an indication that these Euphorbiaceae could be a potential source of antifungal agents.

Fungal cell-wall lytic enzymes, antifungal metabolite(s) production, and characterization from Streptomyces exfoliatus MT9 for controlling fruit-rotting fungi.

An antifungal actinomycete strain MT9 was isolated from Loktak Lake, Manipur, India and its cultural characteristics, fatty acid methyl ester, 16S rRNA gene analysis suggests that strain MT9 is identical to Streptomyces exfoliatus. Strain MT9 displayed strong and broad-spectrum antagonism towards several fruit-rotting fungi by mycelial growth suppression. Crude fungal cell-wall lytic enzymes, i.e., chitinase, β-1,3-glucanase, and protease produced by S. exfoliatus MT9 were optimally active at pH 8.0 and 50 °C, pH 5.0 and 60 °C, pH 9.0 and 70 °C, respectively. All three mycolytic enzymes had good stability over a wide pH range of 5.0-10.0, with protease being more thermostable than both chitinase and β-1,3-glucanase. Interestingly zymogram analysis revealed that S. exfoliatus MT9 secretes six distinct chitinase isoenzymes with approximate molecular weights of 9.42, 13.93, 27.87, 36.43, 54.95, 103.27 kDa, six active protease isoenzymes with apparent molecular weights of 12.45, 30.20, 37.45, 46.32, 52.46, 131.46 kDa, and an active band of 119.39 kDa as β-1,3-glucanase enzyme. Extracellular fluid and its organic solvent extracts also exhibited inhibitory activity to various fruit-rotting fungi. The MIC value of n-butanol extract was 2-25 µg/ml against tested fruit-rotting fungi. Antifungal secondary metabolite(s) was found to be polyene in nature. To the best of our knowledge, this is the first report on extracellular production of fungal cell-wall lytic enzymes and antifungal metabolites by bioactive S. exfoliatus MT9 under submerged fermentation.

Postharvest physiology and technology of Spondias purpurea L. and S. mombin L

Spondias purpurea and S. mombin (Anacardiaceae) are tropical species native to Mexico with a distribution that spans all of tropical America, Central America, Peru and Brazil. The fruits are consumed fresh or processed and enjoy good consumer acceptance because of their taste, which ranges from sour to sour-sweet, and in the case of S. purpurea because of the diversity of colouration of its epicarp. All of these characteristics suggest a high commercial potential for Spondias in Mexico and other regions of tropical America, as well as in export markets. Despite this, the marketing of fruits is mainly local due to their high perishability. The most common postharvest pests and diseases are fruit flies and fruit-rot fungi; however a limited number of conservation methods are used because of the scarce knowledge concerning the postharvest physiological behaviour of Spondias fruit. This document therefore, aims to provide relevant information about the biology and postharvest technology of S. purpurea and S. mombin published by other authors over the last 50 years, as well as experimental data obtained by our research group that will provide a useful reference for future work on the postharvest handling of these genetic resources.

Assessment of Cymbopogon citratus (DC.) Stapf Essential Oil as Herbal Preservatives Based on Antifungal, Antiaflatoxin, and Antiochratoxin Activities and In Vivo Efficacy during Storage

Thirty-five randomly collected samples of stored table grapes (Vitis vinifera L.) from different markets of Gorakhpur city, Uttar Pradesh, India, revealed occurrence of 11 types of fungi. Of which, Aspergillus flavus, Aspergillus niger, and Aspergillus ochraceus were dominant causing severe decay of grapes with 58%, 52%, and 67% incidence, respectively. On screening of 15 essential oils at 0.33 μL/mL, Cymbopogon citratus oil caused 100% mycelial inhibition against aforesaid dominant fungi. Oil was fungistatic at 0.29 μL/mL and exhibited broad fungitoxicity against other fruit rotting fungi associated with collected samples. C. citratus oil completely inhibited the growth and mycotoxin (AFB1 and OTA) secretion of the aflatoxigenic and ochratoxigenic strains of A. flavus, A. niger, and A. ochraceus at 0.8 μL/mL. E-Citral (52.9%) and Z-Citral (39.38%) were the major components of C. citratus oil during gas chromatography and gas chromatography-mass spectrometry analysis. Application of 200 and 300 μL of C. citratus oil on 1 kg of stored grapes showed enhancement of shelf life up to 10 d. The oil did not exhibit any phytotoxic effect on fruits. These results confirm that C. citratus oil could be a natural alternative to commercial fungicide for control of fruit rotting fungi of stored grapes.

Identification of three fruit-rot fungi of banana by 28s ribosomal DNA sequencing

The aim of present investigation was to identify three fruit-rot fungi- Macrophomina phaseolina (Tassi) Goid, Fusarium oxysporum (Schlechtend) and Nigrospora oryzae (Berk and Br.) Petch isolated from banana fruits [Rasthali (Silk AAB) and Cavendish (AAA) varieties]. Out of different fungal genera isolated, the above fungi were responsible for maximum loss of banana fruits as they spread rapidly into the fruit pulp and deteriorated the fruits. The amplification studies of fragment of D2 region of LSU (Large subunit 28S rDNA gene of three fungi understudy was carried out using PCR technique. Based on the nucleotide homology and phylogenetic analysis, the fungus M. phaseolina was identified as M. phaseolina strain R-4242 sp. (Genbank accession number: FJ415068.1), F. oxysporum as Fusarium sp.QJC-1403 5.8S ribosomal RNA gene sp. (Genbank accession number: EU193176.1) and N. oryzae as N. oryzae NRRL: 54030 sp. (Genbank accession number: GQ328855.1). Nucleic acid sequencing provides more objective separation of genera and species than that provided by the conventional techniques. This technique can best be used for the identification of organisms that could not be identified satisfactorily by their microscopic morphological features. Genetic characterization of plant pathogens prevalent in an area is necessary for efficient management and increased crop productivity. The data presented may help researchers to understand the host-pathogen interactions indetail in banana, to design effective strategies for deployment of resistant genes in banana ( Musa paradisiaca L.) growing regions in the country and worldwide.

In vitro control of post-harvest fruit rot fungi by some plant essential oil components.

Eight substances that are main components of the essential oils from three Mediterranean aromatic plants (Verbena officinalis, Thymus vulgaris and Origanum vulgare), previously found active against some phytopathogenic Fungi and Stramenopila, have been tested in vitro against five etiological agents of post-harvest fruit decay, Botrytis cinerea, Penicillium italicum, P. expansum, Phytophthora citrophthora and Rhizopus stolonifer. The tested compounds were β-fellandrene, β-pinene, camphene, carvacrol, citral, o-cymene, γ-terpinene and thymol. Citral exhibited a fungicidal action against P. citrophthora; carvacrol and thymol showed a fungistatic activity against P. citrophthora and R. stolonifer. Citral and carvacrol at 250 ppm, and thymol at 150 and 250 ppm stopped the growth of B. cinerea. Moreover, thymol showed fungistatic and fungicidal action against P. italicum. Finally, the mycelium growth of P. expansum was inhibited in the presence of 250 ppm of thymol and carvacrol. These results represent an important step toward the goal to use some essential oils or their components as natural preservatives for fruits and foodstuffs, due to their safety for consumer healthy and positive effect on shelf life extension of agricultural fresh products.

BREEDING FOR FRUIT ROT RESISTANCE IN VACCINIUM MACROCARPON

The cranberry (V. macrocarpon) fruit rot complex can cause severe crop loss and requires multiple fungicide applications each year. To identify sources of fruit rot resistance, fungicides were withheld from our germplasm collection in 2003 and 2004 and the collection was rated for fruit rot. In September 2003, approximately 70% of the 562 plots had severe rot, while 6% showed some level of resistance. Visual ratings correlated with quantitative assessments. In 2004, several accessions continued to show resistance, and there was significant correlation between the 2003 and 2004 ratings (r=0.80) and counts (r=0.75). Three of the resistant accessions had previously been used in crosses and their progeny had been planted in a large progeny evaluation trial. Fungicides were withheld in 2005-07 and the trial was rated each year for fruit rot. In 2007, disease pressure was so severe that of the 1644 progeny evaluated from 30 crosses (four of these crosses had a resistant parent), 1085 progeny exhibited approximately 100% rot, while only 13 plots had a rating of '2' (<40% fruit rot). Families from resistant parents had a higher frequency of resistant progeny, indicating additive genetic effects, and the potential for improving resistance through breeding. However, a few resistant progeny originated from susceptible parents suggesting non-additive variance for field fruit rot resistance also exists. Fruit cultured from susceptible and resistant plots had the same species of fruit rot fungi present (primarily Phyllosticta vaccinii, Physalospora vaccinii and Colletotrichum gloeosporioides [Glomerella cingulata]), suggesting broad-based resistance. DNA fingerprinting of resistant accessions identified several distinct types, offering potentially different sources of genetic resistance. These fruit rot-resistant plants have now been used in 60 crosses. Molecular markers for resistance are being developed, which will allow for more efficient progeny screening.

Control of Fruit Rots of Processing Tomato Using Cover Crop Mulch and Tom-Cast

The effects of three bed systems [conventional (bare soil), chemically killed, or mechanically killed winter rye (Secale cereale) + hairy vetch (Vicia villosa) cover crop mulch] and five fungicide programs (no fungicide, 7-day fungicide application program, and Tom-Cast-timed fungicide applications at 15, 18, or 25 disease severity values) on marketable yield and soil-borne fungal fruit rot development in processing tomato (Solanum lycopersicum) production were studied. In 1997, marketable yield was higher in both cover crop systems compared with the conventional bed system. In 1997, percentage of anthracnose- (Colletotrichum coccodes) and ground rot-infected fruit (caused by Pythium spp. or Phytophthora spp.) were lower in both cover crop mulch systems compared with the conventional bed system. In 1998, marketable fruit yields were lower in both cover crop mulch systems compared with the conventional bed system. Percentage of anthracnose-infected fruit was lower in 1998 in the chemically killed cover crop mulch system compared with mechanically killed bed system. There were no differences in ground rot-infected fruit between bed systems in 1998. In 1998, percentage of total molded fruit in the chemically killed cover crop mulch system was reduced compared with the mechanically killed cover crop mulch system.

Control of Fruit Rots of Processing Tomato Using Cover Crop Mulch and Tom-Cast

The effects of three bed systems [conventional (bare soil), chemically killed, or mechanically killed winter rye (Secale cereale) + hairy vetch (Vicia villosa) cover crop mulch] and five fungicide programs (no fungicide, 7-day fungicide application program, and Tom-Cast-timed fungicide applications at 15, 18, or 25 disease severity values) on marketable yield and soil-borne fungal fruit rot development in processing tomato (Solanum lycopersicum) production were studied. In 1997, marketable yield was higher in both cover crop systems compared with the conventional bed system. In 1997, percentage of anthracnose- (Colletotrichum coccodes) and ground rot-infected fruit (caused by Pythium spp. or Phytophthora spp.) were lower in both cover crop mulch systems compared with the conventional bed system. In 1998, marketable fruit yields were lower in both cover crop mulch systems compared with the conventional bed system. Percentage of anthracnose-infected fruit was lower in 1998 in the chemically killed cover crop mulch system compared with mechanically killed bed system. There were no differences in ground rot-infected fruit between bed systems in 1998. In 1998, percentage of total molded fruit in the chemically killed cover crop mulch system was reduced compared with the mechanically killed cover crop mulch system.

Anthocyanins Reduce Fungal Growth in Fruits

As the most visible role of anthocyanins is to impart colors, the adaptive significance of anthocyanins in plant reproductive organs is invariably attributed to the attraction of seed dispersers and pollinators. However, few studies suggested that anthocyanins in vegetative tissue might also function in plant defence, although the evidence for such a function is not particularly strong. Here, we investigated whether anthocyanins contribute to fruit defence against fruit-rot fungi. We found that the risk of fruit-rot in grape varieties infected with Botrytis cinerea decreased with increasing anthocyanin contents. Moreover, anthocyanin contents directly inhibited growth rates of nine fruit-rot fungi on agar plates. Anthocyanins reduced fungal growth by 50% in the concentrations that typically characterise unripe blackberries and by 95% in the concentrations that typify ripe blackberries. We conclude that anthocyanins in fruits not only function to attract animal vectors, but that they also contribute to fruit defence. The antifungal activity of anthocyanins might more widely explain their occurrence in various plant organs such as vegetative tissue and roots.

Occurrence of fruit rot fungi (Aspergillus section Nigri) on some drying varieties of irrigated grapes

The occurrence of Aspergillus section Nigri on certain varieties of grapes used for dried vine fruit (and especially on Sultana), was surveyed extensively during three harvest seasons (1998, 1999 and 2000). Members of Aspergillus section Nigri were enumerated and identified in a total of 806 samples comprising both fresh fruit as well as partially-dried and fully-dried grapes. Aspergillus aculeatus, A. carbonarius and A. niger were commonly isolated. Of those three species, A. niger showed the highest optimum temperature for growth, as well as highest thermal tolerance. That combination of properties probably accounts for the occurrence of A. niger in over 80% of fruit samples in all three seasons. A. carbonarius was also prevalent on fruit surveyed for fungal rots. Severity of infection with this group of fungi was highest in the seasons when grape berries were rain-damaged. Typically, the Aspergillus count increased during the initial stages of drying. Growth of these moulds while grapes are either still on the vine or during drying carries important implications for human consumption due to the potential for certain strains of these fungi to produce ochratoxin A. Fungal cultures on coconut cream agar plates were screened for production of ochratoxin A via fluorescence emission under UV light. Such fluorescence was observed in all isolates of A. carbonarius, but was not observed in any isolates of either A. aculeatus or A. niger.

Yield loss caused by fruit rot fungi on sweet cherry in Kyustendil region, Bulgaria

The aim of the study was to determine the incidence of fruit rot caused by several fungal pathogens from 1999 to 2003. The study was conducted in three sweet cherry orchards at the Institute of Agriculture (Kyustendil, Bulgaria). One copper containing fungicide was applied in late autumn and early spring. During the growing seasons, 2-5 sprays were applied against fungal diseases. Trees were not sprayed specifically against fruit rot during the growing season, with the exception of 1999, when a spray of myclobutanil was applied after a long rainy period during the maturity of fruits. In one orchard, two nitrogen fertilization treatments were also prepared. In treatment 1, trees were fertilized with ammonium-nitrate 10 g/m2 and in the other treatments trees were not. Incidence of the five most important fruit rot pathogens, Monilinia fructigena, M. laxa, Botritys cinerea, Alternaria alternata and Rhizopus stolonifer was assessed in all orchards. The most severe yield loss (14.80 %) was measured in 1999, when weather conditions were the most favourable for fruit rot development. In this year, brown rots (M. fructigena and M. laxa) caused the highest damage (9.22 and 4.04 %, respectively) out of all assessed fruit rot pathogens. In all other years, yield loss was significantly lower than in 1999. In 2002, A. alternata caused the main fruit rot (4.46%) and all other fungi were less important, while in 2003, B. cinerea caused considerable yield loss (2.28 %) compared to all other fruit rot pathogens. Experiments on fertilization showed that nitrogen significantly increased fruit rot damage in 1999, 2001, 2002 and 2003. The effect of nitrogen fertilization was higher in years with rainy periods around harvest (1999 and 2002) compared to more dry years (2000 and 2001). Results were compared with similar studies and biological interpretations of the results are discussed.

Evaluation of Sampling Strategies for Determining Incidence of Cranberry Fruit Rot and Fruit Rot Fungi.

Two sampling strategies were compared and sources of variability in the sampling protocols analyzed to optimize sampling methods for studies of cranberry fruit rot that occurs in the field (i.e., field rot). For the first method, fruit were dry picked by hand from randomly assigned quadrats; for the second method, fruit were scooped from harvest floodwaters. Rot incidence, which ranged from 1.8 to 9.7%, did not differ significantly between upland and lowland sites or, in general, between dry-picked and wet-harvested samples. There were no consistent differences between upland and lowland sites in the frequency of isolation of any fungus from either rotten or sound fruit. The incidence of certain saprophytic and soilborne fungi was greater in wet-harvested compared with dry-picked fruit. In general, rot incidence and incidence of various fungal taxa isolated from fruit varied more among samples within sites than among sites. Site type (i.e., upland or lowland) was never a major source of variability. These findings suggest that if the goal were to assess the occurrence of cranberry fruit rot within a region, intensive within-site sampling would be necessary, but site type would not be an important consideration, at least in Wisconsin, where this study was conducted.

Distribution of Cranberry Fruit-Rotting Fungi in New Jersey and Evidence for Nonspecific Host Resistance

ABSTRACT A survey was conducted over a 3-year period to determine the frequencies and distributions of fruit-rotting fungi in New Jersey cranberry beds. In the first 2 years of the study, Physalospora vaccinii and Glomerella cingulata were the most prevalent and widespread field-rotting fungi. In the third year, the frequency of G. cingulata declined markedly. Other species such as Coleophoma empetri, Phyllosticta vaccinii, and Phomopsis vaccinii were isolated at high frequencies from a limited number of locations. Storage-rotting fungi including Allantophomopsis cytisporea and A. lycopodina were isolated at low frequencies, but were widely distributed within the growing region. On sound fruit, a somewhat different profile emerged. Fungi such as Phyllosticta elongata, Alternaria spp., and Physalospora vaccinii were commonly isolated. In comparisons among different cranberry cultivars, no differences in the fungal profiles were seen. This was interpreted to indicate that if differences in fruit-rot resistance exist, they are likely to be general forms of resistance rather than fungal species-specific mechanisms.

Phototoxicity ofCitrus jambhiri to fungi under enhanced UV-B radiation: Role of furanocoumarins

Extracts ofCitrus jambhiri foliage exposed to and shielded from UV-B radiation were assayed for phytochemical changes and phototoxicity against four fungal pathogens, two of which (Fusarium solani andF. oxysporum) are causative agents of root rots and two of which (Penicillium italicum andP. digitatum) are associated with fruit rots. Conidial pigment mutants of these four fungal species were assayed to determine whether pigments play a role in protecting fungi against plant photosensitizers. Exposure to 10.2 kJ/ day UV-B radiation for 95 days significantly reduced phototoxicity of leaf extracts to fungi. Although furanocoumarin levels were reduced by UV-B, analysis of covariance revealed that variation in phototoxicity of the extracts cannot be attributed entirely to variation in furanocoumarin content; thus, the possibility exists that nonfuranocoumarin phototoxic constituents, as yet unidentified, respond to UV-B exposure and contribute to overall phototoxic defense ofC. jambhiri against pathogens. Root rot fungi were substantially more sensitive to furanocoumarin phototoxicity than were fruit rot fungi, a pattern consistent with the amount of light exposure normally experienced by these fungi when associated with phototoxic plants. Although pigmented strains of all four species displayed greater resistance to phototoxicity of pure furanocoumarins, no strain differences were detected in assays of foliar extracts; this finding also suggests that nonfuranocoumarin constituents may be involved in the phototoxic defense ofC. jambhiri against pathogens.

Fruit Rot, Antifungal Defense, and Palatability of Fleshy Fruits for Frugivorous Birds

We tested several predictions concerning fungal rot and antifungal defense of vertebrate—dispersed fruit. (1) Fungal fruit to should be generally deterrent to frugivores. But because fungi may vary in their negative effects, antifungal defenses should be allocated in relationship to net effects of particular species on dispersal. (2) Defenses of fruits under selection for high palatability should be directed primarily toward microbes ("microbespecific" defenses). Lower quality fruits, for which high palatability is not crucial to dispersal, may be defended by more general defenses. (3) Preferred fruits should be defended to a lower degree than less preferred fruits, as a result of consistently high dispersal rates (Removal Rate model). We tested our hypotheses using real fruits and artificial—pulp media of six temperate ericaceous plants in feeding trials with captive birds and in fungal growth trials. Plants had been assigned to two temperature fruiting classes (Summer Small—seeded, SS, Fall—Low—quality, FL), and differed in ripening phenology, persistence times, and fungal resistance in the field. We compared feeding rates on fruits rotted by members of a suite of fruit rot fungi. We also determined feeding rates on artifical—pulp media that either contained ripe fruit extracts or did not, and we determined fungal growth rates on identical media. We found that: (1) fungal species depressed feeding rates in general accordance with their reported vertebrate toxicity. Relative to nontoxic fungi, toxic fungi were inhibited more strongly by secondary fruit pulp extracts. (2) Artificial—pulp media of SS fruits were preferred in feeding trials, due both to basic nutritional composition and nondeterrent (microbe—specific) secondary defense. (3) In accordance with the Removal—Rate model, artificial—pulp media of the preferred SS fruits showed significant antifungal activity, but at a much lower level than that of FL fruits. Our results suggest that a primary function of secondary chemicals in ripe fruits may be to defend against destructive fungi that compete with seed dispersers for the pulp. Our results generally support the hypothesis that selective pressures may result in ripe fruit defenses that are directed primarily against organisms having strong negative effects upon dispersal. As such, factors influencing risk of pulp consumption by nondispersers may be useful predictors of fruit defense patterns.

Fungal and Physiological Breakdown in Six Cranberry Cultivars Following Water Harvesting and Cold Storage

Abstract Six cranberry (Vaccinium macrocarpon Ait.) cultivars, (water harvested under New Jersey growing conditions) were evaluated for their suitability for fresh market sale. Fruit were hand-picked and water-reel picked, held in the bog flood water for 0-, 4-, 8-, 12-, and 24-hr periods, and then stored for 12 weeks at 3°C. After an additional 4 days at 21° storage the fruit were evaluated for fungal fruit rot and physiological breakdown (PB). ‘Franklin’, ‘Pilgrim’, and ‘Stevens’ were superior to ‘Early Black’ and ‘Wilcox’ as measured by occurrence of rot and PB. Water immersion time had a greater influence on PB than on rot. As time in the water increased, the percentage of fruit manifesting PB increased, with ‘Ben Lear’ developing the least and ‘Early Black’ and ‘Wilcox’ the most PB.