Gray Mycelium Research Articles

First Report of Botrytis cinerea Causing Gray Mold of Pomegranate (Punica granatum) in Greece.

Pomegranate is rapidly increasing in production in Greece. During August of 2008 in the region of Larisa (central Greece), preharvest fruit rot was observed on pomegranate (cv. Kapmaditika) that caused losses estimated at 10%. Symptoms first appeared as small spots on the fruits that later increased in size and developed into expanded, dark brown lesions. Internally, tissues were soft and brown with gray mycelia and conidiophores observed. Affected fruits decayed completely during 2 months of storage (5 to 6°C), causing yield losses of up to 20%. To isolate the casual agent, conidia and conidiophores were scraped aseptically from the internal tissues, suspended in sterile water, and streaked onto the surface of potato dextrose agar (PDA). Single hyphal tips were transferred to PDA, and the isolated fungus was identified as Botrytis cinerea Pers.:Fr. on the basis of morphological characteristics (2). B. cinerea was consistently isolated from symptomatic tissues. Colonies of B. cinerea on PDA were at first colorless and became gray to brown with the development of lemon-shaped conidia (average 7.5 × 9 μm). Sclerotia were black and varied in size (1.4 to 4.5 × 1.5 to 2.7 mm) and shape (2). Pathogenicity of the isolated fungus was tested by wound inoculating five mature pomegranate fruits (cv. Kampaditika) after surface sterilization with 5% sodium hypochlorite. Plugs of the fungus (5 mm in diameter) obtained from the colony margins were transferred onto a 3- × 3-mm wound on the surface of sterilized fruit. Sterile PDA plugs were used to inoculate five control pomegranate fruits. Fruit were incubated at 22°C and 80% relative humidity in the dark. Extensive decay, similar to that observed on diseased fruits in the field, was observed on inoculated fruits 7 days after inoculation, whereas control fruits showed no decay. The pathogen was reisolated from internal rotten tissues of inoculated fruit, but not from the noninoculated control fruits. Fruit rot of pomegranate caused by B. cinerea has been reported previously in the United States (1) and China (3). However, to our knowledge, this is the first report of B. cinerea causing gray mold of pomegranate in Greece.

First Report of Botrytis Blight Caused by Botrytis cinerea on Chamelaucium uncinatum in Italy.

Chamelaucium uncinatum (wax flower), an evergreen shrub belonging to the Myrtaceae family, is suitable for growing in containers. In the Albenga area (northern Italy), this species is grown as a potted plant. In April 2009, symptoms of a previously unknown blight were observed in a commercial glasshouse in the Savona Province (northern Italy) on 80% of 500 potted plants of cv. Snow Flake. Glasshouse temperatures ranged between 16 and 22°C and plants were drip irrigated. Initially, leaves and calyces appeared chlorotic. Subsequently, necrotic lesions developed on flower stalks and occasionally the corollas. After 10 days, soft, gray mycelium became apparent on symptomatic tissue, especially on the foliage. Severely infected leaves and flowers eventually became completely necrotic and abscised. Tissues were excised from diseased leaves, immersed in a solution containing 1% sodium hypochlorite for 10 s, and then cultured on potato dextrose agar (PDA) medium. A fungus developed abundant mycelium when incubated under constant fluorescent light at 23 ± 1°C. Numerous, small sclerotia also developed on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark, spheroid, and measured 0.5 to 1.8 × 0.5 to 1.5 (average 1.2 × 1.0) mm. Conidia were smooth, gray, unicellular, ovoid, measured 8.5 to 11.1 × 7.1 to 8.6 (average 9.7 × 7.8) μm, and similar to those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 495-bp segment showed 100% similarity with the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned the GenBank Accession No. GQ149477. Pathogenicity tests were performed by spraying leaves of healthy potted C. uncinatum with a spore suspension (2 × 104 conidia/ml) obtained from PDA cultures of the pathogen. Each plant received 30 ml of the inoculum. Plants sprayed with water only served as controls. Three plants per treatment were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a growth chamber at 20 ± 1°C. The first foliar lesions developed on leaves 7 days after inoculation and were similar to those observed in the commercial glasshouse, whereas control plants remained healthy. B. cinerea was consistently reisolated from these lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on C. uncinatum in Italy as well as in Europe. The disease has been reported in California (3) and more recently in South Africa (4). In Italy, the economic importance of the disease is currently still limited.

First Report of Botrytis Blight Caused by Botrytis cinerea on Platycodon grandiflorum in Italy.

Platycodon grandiflorum (balloon flower), a perennial plant belonging to the Campanulaceae family, is widely grown as a bedding plant in temperate gardens. This species is characterized by the ability to bloom profusely throughout the summer into early fall and for its white to blue and pink flowers. In September 2008, symptoms of a previously unknown blight were observed in six gardens located in the Biella Province of northern Italy. When the disease developed, temperatures ranged between 15 and 22°C with frequent rains (149.8 mm of rainfall registered in September 2008 by the meteorological station of Oropa, located in the same area in which the disease appeared). Initially, leaves and petioles appeared chlorotic. Subsequently, lesions developed on the stems and flowers were sometimes affected. In each garden examined, approximately 50% of the plants were affected by the disease. A soft, gray mycelium was observed on symptomatic tissues, especially the stems. Severely infected leaves and stems eventually became completely rotted and later desiccated. Diseased tissue was excised from affected leaves, immersed in a solution containing 1% sodium hypochlorite for 10 s, and then cultured on potato dextrose agar (PDA) medium. A fungus developed that produced abundant mycelium on PDA medium when incubated under constant fluorescent light at 22 ± 1°C. Numerous sclerotia were produced on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark, irregular, and measured 1 to 3.5 × 0.9 to 2.5 (average 2.1 × 1.5) mm. Conidia were smooth, ash colored, unicellular, ovoid, and measured 11 to 19 × 7 to 13 (average 15 × 11) μm. These morphological features were typical of those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 539-bp segment showed 100% similarity with the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned the GenBank Accession No. GQ149480. Pathogenicity tests were performed by placing 1-cm2 fragments removed from PDA cultures of B. cinerea isolated from balloon flower on leaves of healthy potted P. grandiflorum plants (4-month-old). Five fragments were placed on each plant. Plants inoculated with PDA alone served as controls. Ten plants per treatment were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a greenhouse at temperatures between 18 and 23°C. The first foliar lesions developed on leaves 3 days after inoculation, and after 5 days, 80% of the leaves were severely infected. As the infection progressed after the inoculation, the stems also became infected. Control plants remained healthy. B. cinerea was consistently reisolated from leaf and stem lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on P. grandiflorum in Italy, as well as in Europe. Blight on balloon flower attributed to Botrytis spp. was previously reported in the United States (3).

First Report of Botrytis Blight Caused by Botrytis cinerea on Periwinkle (Catharanthus roseus) in Italy.

Catharanthus roseus (periwinkle), a perennial plant belonging to the Apocynaceae family, is grown as a warm-season bedding plant in temperate gardens. This species is characterized by a long flowering period and prized for its white-to-dark pink flowers. In October of 2008, 15% of C. roseus plants in a public garden located in Torino (northern Italy) showed symptoms of a previously unknown blight. When the disease developed, temperatures ranged between 10 and 24°C (average 17.3°C) and plants were being watered through sprinkle irrigation. Necrosis developed on the stems first, eventually spreading to leaf stalks, and the the entire leaf. Subsequently, the pathogen developed a scant, delicate, gray mycelium on affected tissues, particularly diffused on the stems. Severely infected leaves and stems eventually became completely rotted and desiccated. Tissues were excised from diseased leaves, immersed in a solution containing 1% sodium hypochlorite for 10 s, and cultured on potato dextrose agar (PDA) medium. The fungus produced abundant mycelium on PDA medium when incubated under constant fluorescent light at 22 ± 1°C. Numerous sclerotia were produced on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark and irregular, measuring 0.5 to 2.8 × 0.5 to 2.2 (average 1.4 × 1.1) mm. Conidia were smooth, ash colored, ovoid, measuring 8 to 16 × 6 to 10 (average 10 × 7) μm, and similar to those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 780-bp segment showed a 100% homology with the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned GenBank Accession No. FJ486271. Pathogenicity tests were performed by placing numerous fragments of PDA cultures on leaves of healthy, potted, 8-month-old C. roseus plants. Plants inoculated with PDA alone served as controls. Three plants per treatment were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a greenhouse at temperatures ranging between 18 and 25°C. The first foliar lesions developed on leaves 5 days after inoculation, whereas control plants remained healthy. B. cinerea was consistently reisolated from these lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on C. roseus in Italy. The same disease was previously reported in many countries including the United States (3) and Taiwan (4).

First Report of Botrytis cinerea Causing Leaf Spot of Aquilegia vulgaris in Japan.

European columbine, Aquilegia vulgaris L., Ranunculaceae, is an herbaceous flower widely used in gardens, parterres, and courtyards and is a traditional herbal plant. During the summer of 2008, leaf spots were observed on a plant cultivated along a roadside area in Nasushiobara, Tochigi, Japan. In some courtyards, the leaf spot affected more than 60% of the plants. Early symptoms appeared as small, round or elliptic, brown lesions on the leaves. Lesions expanded to 5 to 15 × 4 to 10 mm, irregular spots that were dark brown to black in the middle, with pale yellow-brown or purple-brown margins. In continuously wet or humid conditions, thick, gray mycelium and conidia appeared on the surface of leaf spots. Conidiophores were melanized at the base and hyaline near the apex, branched, and septated (approximately 3 mm × 16 to 18 μm). Conidia were hyaline, aseptate, ellipsoidal to obovoid, with a slightly protuberant hilum, and ranged from 9 to 14.5 × 5.5 to 6.5 μm. The pathogen was identified as Botrytis cinerea Pers.:Fr on the basis of morphology and sequence of ITS1-5.8s-ITS2 region of rDNA. The sequence (GenBank Accession No. FJ424510) exactly matched the sequences of two Botryotinia fuckeliana (anamorph Botrytis cinerea), (e.g., GenBank Accession Nos. AY686865 and FJ169666) (2). The fungus was isolated on potato dextrose agar (PDA) from a single conidium found on the symptomatic leaf tissue. Colonies of B. cinerea were first hyaline and later turned gray to black when the spores differentiated. Koch's postulates were performed with three whole plants of potted aquilegia. Leaves were inoculated with mycelia plugs harvested from the periphery of a 7-day-old colony; an equal number of plants were inoculated with the plugs of PDA medium only and served as controls. All plants were covered with plastic bags for 24 h to maintain high relative humidity and incubated at 25°C. After 8 days, all mycelium-inoculated plants showed symptoms identical to those observed on leaves from A. vulgaris infected in the field, whereas controls remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was B. cinerea. B. cinerea has been previously reported on A. vulgaris in the United States and China (1,3). To our knowledge, this is the first report of leaf spots caused by B. cinerea on A. vulgaris in Japan.

First Report of Gray Mold Caused by Botrytis cinerea on Stevia rebaudiana in Italy.

Stevia rebaudiana (sweetleaf) is a perennial shrub belonging to the Asteraceae family and is widely grown for its sweet leaves. With its extracts having as much as 300 times the sweetness of sugar, this species is used in many countries for the production of sugar substitutes. However, in Italy, as well as in other countries, this species cannot be grown for the use of its leaf extracts. This plant is grown in a few nurseries in the Albenga Region (northern Italy) as potted plants. In February of 2008, 3-month-old plants grown in plastic pots (14-cm diameter) under glasshouse on heated benches started showing symptoms of a previously unknown blight. The temperature in the glasshouse ranged between 16 and 20°C and plants were watered by sprinkle irrigation. Leaves, starting from the basal ones, showed small, brown spots that spread across the entire leaf surface. Subsequently, the crown and stem were infected, and the pathogen developed abundant, soft, gray mycelium on leaves and stems and in the middle of the heads of S. rebaudiana. Flowers were not present when the symptoms appeared. Severely infected leaves dried out and became necrotic. The disease was observed in one nursery in which 5% of the plants were affected. The margins of the lesions were excised from leaves, immersed in a solution containing 1% sodium hypochlorite, and then cultured on potato dextrose agar (PDA) medium. A fungus produced abundant mycelium when incubated under constant fluorescent light at 22 ± 1°C after 10 days. The conidia were smooth, hyaline, ovoid, measuring 15.5 to 8.3 × 11.1 to 7.3 (average 11.6 × 8.6) μm, and were similar to those described for Botrytis cinerea. Conidiophores were slender and branched with enlarged apical cells bearing conidia on short sterigmata. The identity of the fungus was also confirmed by the production of numerous, small, black sclerotia on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark and irregular with a diameter ranging from 1 to 2 mm. These morphological characters identified the fungus as B. cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 780-bp segment showed a 100% homology with the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned GenBank Accession No. FJ486270. Pathogenicity tests were performed by spraying leaves of six healthy 6-month-old potted S. rebaudiana plants with a 105 conidia/ml suspension. Six plants sprayed with water only served as controls. Plants were covered with plastic bags for 3 days after inoculation to maintain high relative humidity and were placed in a growth chamber at 20 ± 1°C. The first foliar lesions developed on leaves 4 days after inoculation, whereas control plants remained healthy. B. cinerea was consistently reisolated from these lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on S. rebaudiana in Italy. The disease has been reported in Ukraine (3) and more recently in Japan (4). The economic importance of this disease is at the moment limited.

First Report of Botrytis Blight Caused by Botrytis cinerea on Gaura lindheimeri in Italy

Gaura lindheimeri (wand flower) is a perennial plant belonging to the Onagraceae family that is used for perennial borders in xeric and mesic landscapes. It produces flowers floating above the plant like small, dancing butterflies. This plant is becoming popular in the Albenga Region (northern Italy) where white and rose varieties are grown as potted plants. In January of 2008, 5-month-old 'Whirling Butterflies' plants grown in plastic pots (14 cm in diameter) in the open field started showing symptoms of a previously unknown blight. When the disease developed, temperatures ranged between 3 and 17°C (average 9°C) and average relative humidity was 64%. Small, brown spots appeared on the basal portion of leaves first, eventually spreading to cover entire leaves. Subsequently, the pathogen developed abundant, soft gray mycelium on affected leaf tissue. Severely infected leaves eventually became completely rotten and desiccated. Sixty percent of plants were affected by the disease. Tissues were excised from diseased leaves, immersed in a solution containing 1% sodium hypochlorite for 10 s, and then cultured on potato dextrose agar (PDA) medium. The fungus produced abundant mycelium on PDA medium when incubated under constant fluorescent light at 22 ± 1°C. The conidia were smooth, hyaline, globoid, measuring 11.8 to 9.4 × 8.3 to 6.6 (average 10.7 × 7.4) μm, and are similar to those described for Botrytis cinerea. The identity of the pathogen was also confirmed by the production of numerous sclerotia on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark, irregular, and measured 3 to 4 × 2 to 3 mm. The fungus was identified as B. cinerea on the basis of these characters (1). Pathogenicity tests were performed by spraying leaves of healthy, potted 8-month-old G. lindheimeri 'Whirling Butterflies' plants with a 105 conidia/ml suspension. Plants sprayed with water only served as controls. Five plants per treatment were used. Plants were covered with plastic bags for 6 days after inoculation and maintained in a growth chamber at 20 ± 1°C. The first foliar lesions developed on leaves 5 days after inoculation, whereas control plants remained healthy. B. cinerea was consistently reisolated from these lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on G. lindheimeri in Italy. The economic importance of this disease will increase with the increased cultivation of this species. Reference: (1) H. L. Barnett and B. B. Hunter. Illustrated Genera of Imperfect Fungi. Burgess Publishing Company, Minneapolis, MN, 1972.

First Report of Blueberry Botrytis Blight in Buenos Aires, Entre Ríos, and Córdoba, Argentina.

Since 2003, a new field disease has been observed on several cultivars of highbush blueberry (Vaccinium corymbosum L.) in Buenos Aires (Baradero, Colonia Urquiza, Lima, Mercedes, and San Pedro), Entre Ríos (Concordia, Gualeguaychú, and Larroque), and Córdoba (Capilla del Monte and La Cumbre). Infected flowers turned brown to tan with a water-soaked appearance and shriveled up. Blighted flowers typically did not produce fruits; even an entire cluster of berries could be aborted. A chlorotic area, that later became necrotic and turned light brown, developed when leaves were in contact with blighted flowers. A watery rot developed on fruit occasionally before harvest but more generally after harvest. Infected tender green twigs also became blighted, with leaf tissue becoming brown to black. Older twigs and stems were also blighted. Abundant, gray mycelium with conidial masses developed on all affected tissues under moist conditions. Sections of infected leaves, twigs, stems, flowers, and fruits were surfaced sterilized with 0.2% NaOCl, plated on 2% potato dextrose agar (pH 7), and incubated at 22°C. Pure cultures formed a whitish dense mycelial mat and turned gray after 72 h. Conidia were ellipsoid, hyaline, nonseptate, and formed on botryose heads. They ranged from 5.8 to 9 × 8.1 to 13.7 μm (average 8.6 × 10.2 μm). Black, round, and irregular microsclerotia developed on 7-day-old cultures with an average size of 1.1 × 1.7 mm. Morphological characteristics agree with those described for Botrytis cinerea Pers.:Fr (1). Pathogenicity was tested on 10 12-month-old potted blueberry plants cv. O'Neal by spraying a suspension of 1 × 106 conidia per ml of sterile distilled water. Ten plants used as controls were sprayed with sterile distilled water. Each plant was covered with a transparent polyethylene bag for 48 h and incubated at 20 ± 2°C in humid chambers for 15 days. Lesions similar to those observed in the fields developed after 4 days and asexual fructifications developed after 5 days. The same pathogen was reisolated from the lesions, thus completing Koch's postulates. Water-treated plants remained symptomless. To our knowledge, this is the first report of a disease caused by B. cinerea on blueberry in Buenos Aires, Córdoba, and Entre Ríos provinces of Argentina.

Two New Primers Highly Specific for the Detection of "Botrytis cinerea" Pers. Fr.

Of thirty-nine Botrytis cinerea isolates originating in different host-plants and grown in pure cultures, twenty-six produced abundant grey aerial mycelium and sporulated intensely, whilst thirteen produced a thin mycelial layer, abundant sclerotia and secreted an unidentified yellow pigment in PDA culture media. The commonly used C729 +/– primers (5’-AGCTCGAGAGAGATCTCTGA-3’; 5’-CTGCAATGTTCTGCGTGGAA-3’) designed to detect B. cinerea did not amplify the DNA fragment of 0.73 kb in this smaller group of strains under standard conditions, whereas a shorter DNA fragment (0.60 kb) was amplified at a lower annealing temperature (50°C). This fragment was sequenced and two new internal primers were designed, BC108 + (5’-ACCCGCACCTAATTCGTCAAC-3’) and BC563 – (5’-GGGTCTTCGATACGGGAGAA-3’). These new primers were used to amplify a DNA fragment of 0.48 kb for the main group of 26 B. cinerea strains and a shorter fragment (0.36 kb) for the smaller group of 13 strains due to a deletion of 0.12 kb, which was not detected with the primers C729 +/–. All the strains were amplified to detect the presence or absence of Boty and Flipper transposable elements. No correlation was found between strains possessing the deletion and those belonging to either the vacuma or the transposa sibling species. Other closely related Botrytis species such as B. allii and B. fabae were not amplified with these primers, confirming their specificity for B. cinerea and enhancing the sensitivity of the molecular tools available to detect this fungus in host-plants.

Cucurbits under protected cultivation

Cucurbits under protected cultivation

Occurrence of Nigrospora Lint Rot Caused by Nigrospora oryzae on Cotton in Alabama.

During 2000 and 2001, a lint rot of cotton bolls (Gossypium hirsutum L.) was reported in the coastal region of Alabama when precipitation was 55% lower than the 5-year average. Bolls at an early stage of opening contained gray mycelium within the locules. At maturity, the lint within the infected locules was discolored, and the fibers were compact resulting in the characteristic "gray lock" sign and symptom attributed to Nigrospora oryzae (Berk. & Broome) Petch. Roots, petioles, leaves, and bolls when present were sampled at the seedling, first bloom, full bloom, and maturity stages of cotton development. A total of 640 sections of tissue (approximately 5 mm2) were surface sterilized for 20 s in 95% ethanol followed by 60 s in 0.525% NaOCl and aseptically plated on potato dextrose agar. Plates were incubated in the dark at 25°C for 3 to 10 days. N. oryzae was isolated at low frequencies from all plant tissues beginning at first bloom. Developing bolls at full bloom were colonized at a frequency of 48%. N. oryzae conidiophores were branched, flexuous, and pallid to brown with smooth walls 4 to 7 (5) μm thick. Conidiogenous cells were monoblastic, single, and 6 to 9 (7.5) μm in diameter. Conidia were single, smooth, broadly ellipsoidal, dark brown to black, single-celled, and 11 to 16 (14) μm in diameter (2). Principal component analysis was used to examine the relationship between disease incidence and weather parameters. Weather data was obtained from Auburn University Mesonet located in fields where the samples were collected. Principal components from weather data were ambient and soil maximum, minimum, and average temperature, maximum, minimum, and average relative humidity and precipitation. The first principal component, which is temperature, accounted for 61% of total joint variation among original observations. The second principal component, which was related to the moisture variables, accounted for 19% of the variation. The abundance of N. oryzae was correlated with the principal component factor moisture (r = -0.78**). The dry conditions experienced in this region were conducive to N. oryzae lint rot of cotton. This disease has been reported on cotton primarily in arid climates typical of the southwestern United States (1). To our knowledge, this is the first report of N. oryzae lint rot in the southeastern United States.

First Report of Botrytis Blight on Medinilla magnifica and Various Species of Mandevilla and Allamanda in Italy.

Medinilla magnifica Lindl., Mandevilla splendens (Hook.) Woodson, the hybrid Mandevilla × amoena 'Alice du Pont' (pink allamanda), and various species of Allamanda, such as A. cathartica L. and A. blanchetii A. DC. (purple allamanda), are grown in Sicily as ornamentals. After a frost in early December 2001, a sudden wilt of container-grown cuttings of these tropical species was observed in a plastic-covered production greenhouse, with ≈30% of M. magnifica plants and 70% of Mandevilla and Allamanda plants affected. Medinilla plants (≈35 cm high) had been rooted in trays and transplanted individually in 30-cm-diameter pots. Allamanda (recently rooted cuttings) and Mandevilla (well-established) plants showed symptoms ranging from a dark brown rot at the base of stems to a tan-to-brown rot of stem midsection, respectively. Tissues surrounding lesions were water-soaked and covered by gray mycelium. On Allamanda and Mandevilla plants, lesions extended rapidly to lateral branches, and to the petiole and midrib of leaves that became chlorotic and wilted. As stems were girdled, infected plants collapsed, although the roots appeared healthy. Botrytis cinerea Pers.:Fr. was consistently isolated from infected stem pieces surface-disinfested with 1% NaOCl for 1 min and placed on potato dextrose agar (PDA, Oxoid). Morphology and size (6 to 8 × 8 to 12 μm, modal values 7 × 10 μm) of conidia produced on PDA matched those reported for B. cinerea (1). Dark, spherical, and irregularly shaped sclerotia (1 to 6 mm diameter, mean size 3.3 × 2.3 mm) were produced on PDA. Pathogenicity of a single-conidium isolate isolated from M. magnifica was confirmed using two inoculation methods. Twenty 3-month-old cuttings of M. magnifica and pink and purple allamanda were sprayed with a conidial suspension (106 conidia per ml in a 2% glucose solution). A 2% glucose solution was sprayed on 20 control plants. Plants were sealed in transparent plastic bags for 7 days at 15 to 24°C. Typical symptoms developed only on stems of inoculated pink and purple allamanda cuttings 7 days after inoculation. B. cinerea was reisolated from affected tissues. In a separate test, stems of 10 6-month-old plants of M. magnifica and pink allamanda were inoculated by inserting a 3-mm plug taken from 10-day-old sporulating colonies growing on PDA on a superficial cut made with a sterile scalpel. The inoculated wounds were sealed with Parafilm. Ten wounded but noninoculated plants were used as controls. Plants were kept in high humidity at 10 to 20°C. After 10 days, stem necrosis, leaf chlorosis, and wilt were observed on inoculated pink allamanda plants. On inoculated M. magnifica plants, necrotic lesions were observed on stems (45 to 70 mm long and 10 to 18 mm wide) covered by gray mycelium, but the stem was not girdled. B. cinerea was reisolated from infected tissues of inoculated plants to complete Koch's postulates. No lesions developed on noninoculated control plants. To our knowledge, this is the first report from Italy of Botrytis blight on these species. The occurrence of frost may have predisposed these tropical species to infection by B. cinerea. Reference: (1) M. B. Ellis and J. M. Waller. No 431 in: Descriptions of Pathogenic Fungi and Bacteria, CMI, Kew, Surrey, UK, 1974.

First Record of Leaf Spots on Prunus laurocerasus in Belgium Caused by Phytophthora cactorum and Peronospora sparsa.

In fall 2000 and 2001, large leaf spots were observed on Prunus laurocerasus. Two different plant pathogens proved to be the cause. Based on morphological characteristics they were identified as Peronospora sparsa (downy mildew) and Phytophthora cactorum. The P. cactorum isolate (CBS 110121) was identified at the Centraalbureau voor Schimmelcultures (Utrecht, the Netherlands). Sporangia were papillate, ovoid, and deciduous, with a short pedicel. The isolate was homothallic. Chlamydospores were present and approximately 40 μm in diameter. Oogonia were 25 to 31 μm in diameter, and the antheridia were paragynous. Peronospora sparsa had been reported to infect Prunus laurocerasus in the United Kingdom (1). In Belgium, cv. Etna was very susceptible, but cvs. Rotundifolia and Marbled White were also infected. Rotundifolia was susceptible to P. cactorum. At first inspection, the two pathogens caused similar leaf symptoms: large, irregular, brown, necrotic spots on the tips, margins, and center of leaves. However, the undersides of leaves infected with Peronospora sparsa were covered with typical gray mycelium, which was absent on leaves infected with P. cactorum. P. cactorum caused concentric circles in the brown spots. Leaf spots caused by P. cactorum developed quickly in a moist chamber. Spots caused by Peronospora sparsa did not enlarge significantly on detached leaves, but in the field it caused serious losses within a few days. To prove the pathogenicity of P. cactorum, Koch's postulates were satisified on five Prunus laurocerasus Etna plants. The fungus was grown on corn meal agar for 1 week until sporangia formed. An agar plug was placed on five wounded leaves per plant and sealed with Parafilm. Inoculated plants were kept under a plastic cover for 1 day at 22°C, then the cover was removed, and the plants were kept at 20°C. Symptom development was visible after 3 days, and P. cactorum was successfully reisolated. This is the first record of P. cactorum and Peronospora sparsa leaf infection on Prunus laurocerasus in Belgium. Reference: (1) G. Hall et al. Plant Pathol. 41:224, 1992.

Studies on humic acids decomposing streptomycetes: I. Types prevailing in Egyptian soils

The study comprises the enumeration and identification of humic acids decomposing actinomycetes in soils of Egypt. Counts of total actinomycetes (0.5 – 4.0 × 10 6 /g) were not correlated with either soil texture of the organic matter content and the C/N ratio of the soil. Humic acids decomposers represented 2.0 – 25.5% of total actinomycetes counts. Lower densities (17 to 25 × 10 3 /g) were encountered in sand, but clay soils harboured somewhat higher population (18–27 × 10 4 /g). A total of 201 representative isolates of humic acids decomposers were obtained from different soils. All of these isolates were found to belong to the genus Streptomyces , and most of them are characterized by grey mycelium. Twenty-eight different species of true humic acids decomposing Streptomyces were recognized. Huminsäure-zersetzende Aktinomyzeten ägyptischer Böden wurden zahlenmäßig erfaßt und identifiziert. Die Gesamtzahl der Aktinomyzeten (0,5 – 4,0 × 10 6 /g) stand weder mit der Bodentextur noch mit dem Gehalt an organischer Substanz und dem C: N-Verhältnis des Bodens in Beziehung. 2,0 – 25,5% der Aktinomyzeten waren Huminsäurezersetzer. Niedrigere Dichten wurden in Sand ermittelt (17–25 × 10 3 /g), höhere in Lehmböden (18–27 × 10 4 /g). Insgesamt wurden 201 repräsentative Isolate von Huminsäurezersetzern aus den verschiedenen Böden gewonnen. Sie gehören sämtlich der Gattung Streptomyces an. Für die meisten ist graues Myzel charakteristisch. Es wurden 28 verschiedene Spezies an echten Huminsäure-zersetzenden Streptomyzeten festgestellt.

Pseudocercosporella herpotrichoides . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Pseudocercosporella herpotrichoides . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Wheat, barley, oats, rye. Also occurs on many wild and cultivated grasses, including Aegilops, Agropogon, Agrostis, Alopecurus, Bromus, Dactylis, Festuca, Koeleria, Lolium and Poa spp. DISEASE: Causes eyespot of cereals. Typically the disease is characterized by a pale oval spot with a brown margin on the basal leaf sheaths and culm of cereal tillers at or just above ground level, but such symptoms maybe obscure on some cereals, e.g. oats. Black, stromatic pustules are often present within the centre of the lesion and stems may be ridged, kinked, frayed or otherwise distorted at the diseased zone. The grey mycelium of P. herpotrichoides can often be seen in the internal cavity of straws when they are split open. Random lodging ('straggling') of diseased crops occurs as diseased straws topple over before harvest; storm lodging is also more severe. Eyespot symptoms also include a culm or foot rot which can result in post emergence death of young seedlings or tillers; shrivelled grain and partially empty ears (whiteheads) can also occur on maturing crops. GEOGRAPHICAL DISTRIBUTION: Widespread throughout Europe; also occurs in some areas of N. America, Africa and Australia and in New Zealand (CMI Map 74, ed. 3, 1969). TRANSMISSION: Survival of the fungus between crops occurs on infected plant debris, particularly old stubble. Conidia are produced abundantly on this in wet autumn and spring weather and infect the leaf sheaths of young winter cereals. Direct mycelial infection can also occur. The fungus can survive long periods in the soil in infected crop debris and can infect susceptible crops planted at intervals of several years. Secondary weed hosts also act as a source of the fungus but are not as important as old stubble (49, 2426). During moist, cool springs secondary infection within a crop can occur by conidia dispersed from diseased plants.

Taxonomic characteristic of the strain ETH 7437 producing granaticin.

The streptomycete strain ETH 7437, producing granaticin, was characterized according to present taxonomic standards and compared with the strainsStreptomyces olivaceus (Waksman) Waksman and Henrici,Streptomyces coelicolor (Muller) andStreptomyces violaceruber (Waksman & Curtis). The strain ETH 7437 formed gray aerial mycelium, straight and flexuos sporophores, even single hooks and open spirals. Normally the amount of spores in chains was over 50, the surface of spores being smooth. The strain utilizedd-glucose,d-arabinose,d-xylose andd-fructose. The strain was capable of forming antibiotic pigment stably. For the strain ETH 7437 the termStreptomyces granaticolor was proposed.

A New Monoblepharella from Mexico

Among other aquatic Phycomycetes recovered by the author from soil samples collected for him in Mexico during the summer of 1941, by William C. Leavenworth and Martha M. Leavenworth of the Fourth Hoogstraal Biological Expedition to Mexico, there appeared a species of Monoblepharella heretofore unreported. These soil samples were collected in July and allowed to dry thoroughly at that time, then were carefully packed in separate containers. They were brought to the Botanical Laboratories of the University of Illinois in September where they were placed in jars in sterilized distilled water to which several types of substrata suitable for aquatic Phycomycetes had been added. These bits of substrata were examined at regular intervals and the fungi recovered were isolated and identified each time. Hemp seed in the three jars containing soil samples from stations on the north side of Mt. Tancitaro, State of Michoacan, when examined on November 3, were luxuriantly covered with the pearly gray mycelium of a very delicate fungus. An examination of these hyphae showed that they resembled those of Monoblepharella Taylori Sparrow. After cultures had stood on the laboratory table for over ten days and only sporangia appeared on the hyphae, they were placed in a constant temperature oven held at 30° C., a procedure recommended by Sparrow (1940), in an attempt to induce the formation of sexual organs. After three days at this temperature, cultures were found to be producing antherida and o6gonia in abundance. The position of the gametangia on the hyphae and their sequence of formation readily distinguish this plant from Monoblepharella Taylori and warrant its description as new.