bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of Black Dot of Potato Caused by Colletotrichum coccodes in Central Italy
Authors: Buonaurio R. , Natalini G. , Covarelli L. , Cappelli C.
Published: May 2007

Between 1997 and 2000, black dot of potato (Solanum tuberosum L.), caused by the polyphagous soilborne fungus Colletotrichum coccodes (Wallr.) Hughes, was observed each summer in fields located in Umbria (central Italy). Disease incidence ranged from 50 to 100%, and early potato cultivars were generally more susceptible than late-maturing ones. Disease symptoms were first observed during August as a yellowing and wilting of foliage in the tops of plants, followed by rotting of the roots and stems, which led to the premature death of 50 to 70% of plants. Setose1 sclerotia (300 to 500 mm in diameter) and acervuli of the fungus were found on roots and stems of infected plants. Acervuli produced hyaline, aseptate, cylindrical conidia (16 to 22 × 2.5 to 4.5 μm) formed on unicellular cylindrical phialidic conidiophores. The fungus was isolated from diseased stems and roots on potato dextrose agar (PDA) at pH 6.5. Pathogenicity of the fungus was confirmed by fulfilling Koch's postulates using 3- to 4-week-old potato plants of a local cultivar. A superficial 5-mm vertical cut was made with a scalpel into the base of potato stems (2 cm beneath the soil surface), and 5-mm-diameter plugs of PDA alone (control plants) or PDA plus fungal growth were placed over the cuts. The wounds were sealed with wet cotton swabs that were held in place with Parafilm. Symptoms that resembled those in the field were observed on inoculated plants 6 to 8 weeks postinoculation. Symptoms did not appear on the control plants. The same fungus was reisolated from the diseased plants. Based on morphological characteristics of sclerotia, acervuli, and conidia, as well as pathogenicity tests, the fungus was identified as C. coccodes. To our knowledge, this is the first report of C. coccodes as the causal agent of black dot of potato in central Italy. We did not observe foliar outbreaks of the disease, which were reported from the United States (2). In both 1921 (1) and 1951 (3), the fungus was reported to cause severe outbreaks of the disease in northern Italy. Since then, its presence in Italy has been rarely recorded in potato (4). The occurrence of extremely dry and hot weather conditions during the summers of 1997 to 2000, which are favorable for disease development, made the disease particularly severe. We cannot exclude the possibility that the disease may have been present in central Italy before our observations, as it can be misdiagnosed and its symptoms can be masked by the symptoms of other diseases. The significance of black dot in central Italy needs to be reappraised in terms of both yield loss and tuber quality.

References: (1) C. Arnaudi. Atti Ist. Bot. Univ. Pavia. Ser. 3, 1:71, 1924. (2) A. W. Barkdoll and J. R. Davis. Plant Dis. 76:131, 1992. (3) G. Goidanich. Inf. Fitopatol. 1:5, 1951. (4) S. Vitale et al. J. Plant Pathol. 80:265, 1998.
Activity of Benomyl for Control of Postbloom Fruit Drop of Citrus Caused by Colletotrichum acutatum
Authors: Peres N. A. R. , Souza N. L. , Zitko S. E. , Timmer L. W.
Published: May 2007

Postbloom fruit drop (PFD) of citrus caused by Colletotrichum acutatum produces orange-brown lesions on petals and induces the abscission of young fruitlets and the retention of the calyces. Despite the fact that C. acutatum is not highly sensitive to benomyl in culture, this fungicide provides good control of the disease under field conditions. This study was undertaken to determine the effect of benomyl on various stages of disease development to understand the basis for its effectiveness in the field. We found that benomyl at 1.0 μg/ml reduced colony area of C. acutatum by about 75% and completely inhibited growth of C. gloeosporioides. Benomyl did not prevent conidial germination even at 100 μg/ml, but reduced germ tube elongation at 10 and 100 μg/ml. When benomyl was applied to flower clusters on screenhouse-grown plants before inoculation, disease severity was greatly reduced. Applications at 24 and 48 h, but not at 72 h, after inoculation reduced PFD severity. Application of benomyl to symptomatic petals not bearing conidia did not prevent or reduce production of inoculum. Application to petals bearing conidia reduced viability of these fungal propagules by only about 50%. The viability of appressoria on mature leaves was not affected by benomyl application. Even when appressoria on mature leaves were stimulated to germinate by treatment with flower extracts, subsequent application of benomyl did not reduce propagule numbers below original levels. Benomyl appears to act by preventing infection and early development of the fungus in petals. However, once symptoms have developed, this fungicide has only minimal effects on further disease development and spread.
Gaeumannomyces graminisvars.avenae, graminis, andtriticiIdentified Using PCR Amplification of Avenacinase-like Genes
Authors: Rachdawong Sansanalak , Cramer Carole L. , Grabau Elizabeth A. , Stromberg Verlyn K. , Lacy George H. , Stromberg Erik L.
Published: May 2007

Identifying take-all pathogens, Gaeumannomyces graminis varieties avenae (Gga), graminis (Ggg), and tritici (Ggt), is difficult. Rapid identification is important for development of disease thresholds. We developed a single-tube, polymerase chain reaction (PCR) method differentiating among Gga, Ggg, and Ggt. Nucleotide base sequence analyses of avenacinase-like genes from Gga, Ggg, and Ggt isolates provided the basis for designing variety-specific primers. Sequences from Ggg and Ggt were highly related (99% identity), but Gga sequences were <95% identical to Ggg and Ggt sequences. Three 5′ primers specific for Gga, Ggt, and Ggg and a single 3′ common primer allowed amplification of variety-specific fragments of 617, 870, and 1,086 bp, respectively. Each 5′ primer was specific in mixed populations of primers and templates. No PCR products were amplified from related fungi including Gaeumannomyces cylindrosporus and Phialophora spp. We surveyed 16 putative Ggt isolates using our assay; nine produced Ggt-specific fragments and seven produced Ggg-specific fragments. Five Gga isolates produced Gga-specific fragments. However, Gga- and Ggt-specific fragments were observed from a sixth Gga isolate, RB-W, which indicates a mixed culture or a heterokaryon. Our single-tube, PCR method rapidly differentiates among the important take-all pathogens commonly encountered together in cereal fields.
Influence of Temperature and Wetting Period on Inoculum Production by Monilinia fructicola in Peach Twig Cankers
Authors: Watson W. A. , Zehr E. I. , Grimes L. W.
Published: May 2007

Overwintering cankers in peach twigs caused by the brown rot fungus, Monilinia fructicola, were studied to identify the relationships of wetting period and temperature on sporulation. Sporulation was observed on blighted blossoms, peduncles, abscission scars, and cankers resulting from contact with infected fruits. The frequency of sporulation on overwintered infected tissues was greater at 15 and 23°C than at 4 or 11°C. Twelve hours of wetting was sufficient at all temperatures studied (5 to 23°C) for sporulation to occur, but the number of twig cankers supporting sporulation increased with time of wetting up to 72 h. Given the additional moisture requirements for spore germination, ingress, and infection, 17 to 30 h of wetting or high humidity during bloom may be needed for blossom blight to occur unless viable conidia are already present as a result of previous wetting periods.
Comparative Ability of Six Fungicides to Inhibit Development of Phytophthora Gummosis on Citrus
Authors: Matheron M. E. , Porchas M.
Published: May 2007

The activity of the registered fungicides fosetyl-Al and metalaxyl (subsequently replaced with mefenoxam by the manufacturer) was compared with other potentially useful compounds, azoxystrobin, dimethomorph, fluazinam, and zoxamide, for suppression of canker development on citrus bark after inoculation with Phytophthora citrophthora or P. nicotianae. The number of sweet orange trees on which cankers developed after inoculation with P. citrophthora and the average size of cankers when present were lower on plants treated with dimethomorph, fosetyl-Al, or metalaxyl compared with nontreated trees and those treated with azoxystrobin or fluazinam. When bark removed from treated trees was inoculated with P. citrophthora on the cambium surface at 5, 30, or 60 days after treatment (DAT), inhibition of lesion development on bark strips treated with dimethomorph, fosetyl-Al, or metalaxyl was significantly greater than that detected on bark treated with azoxystrobin, fluazinam, or zoxamide. When inoculated with P. nicotianae at 5 or 30 DAT, reduction of lesion size on bark strips treated with dimethomorph, fosetyl-Al, or metalaxyl was significantly greater than that detected on bark treated with azoxystrobin or fluazinam. Inhibition of lesion development by zoxamide was significantly less than that observed with metalaxyl at 5 DAT on bark inoculated with P. nicotianae; however, at 30, 60, and 90 DAT there was no significant difference in the performance of either fungicide. Reduction of lesion growth on the cambium surface compared with outer bark surface, when inoculated with P. citrophthora, did not differ significantly from 5 to 30 DAT for bark tissue treated with azoxystrobin, dimethomorph, fosetyl-Al, or metalaxyl. Among the nonregistered fungicides tested, dimethomorph provided the best level of Phytophthora gummosis control on citrus.
First Report of Stolbur Phytoplasma in Avocado in Spain
Authors: Laviña A. , Batlle A. , Faraco J. Garcia , Herrera C. J. López
Published: May 2007

Since its introduction to southern Spain in the late 1970s, avocado (Persea americana Mill.) has become an alternative irrigation crop to more traditional and less productive dry land crops such as olive, almond, and grapevine. Avocado orchards in this region currently cover an area of 7,500 ha, producing 58,000 tons of fruit in 2000, with 42,000 tons exported annually to the European Union. In summer 1999, symptoms similar to those caused by phytoplasmas were observed in a plot of avocado cv. Hass. Symptoms of leaf roll, leaf veinal chlorosis with the leaves becoming small and abnormally red, and dwarfing were irregularly distributed on affected trees. Host species of phytoplasmas, such as Lavandula officinalis and Thymus officinalis, are found (1) in orchards surrounded by Mediterranean forests. Leaves from eight symptomatic plants taken from affected plots and leaves from two symptomless plants taken from a healthy plot were collected in May, July, and October 2000, and analyzed for phytoplasma infection by polymerase chain reaction (PCR) assays. DNA for PCR was prepared from leaf petioles, midribs, or trunk phloem by phytoplasma-enrichment fraction according to Daire et al. (2). The stolbur phytoplasma was detected in trees by PCR using stolbur-specific nonribosomal primer pair stol 4 f/r (3) or by nested PCR with 16S rDNA primers pairs P1/P7 and fU5/rU3. Phytoplasmas were detected only in samples collected in July. Phytoplasmas were detected by universal primers in all symptomatic samples analyzed in July, whereas stolbur-specific primers gave positive results in only 75% of the symptomatic samples. Restriction fragment length polymorphism (RFLP) analysis with enzymes AluI and Tru9I confirmed the phytoplasma belonged to the stolbur group. To our knowledge, this is the first description of a phytoplasma disease of avocado trees in Spain. Stolbur is the most important vector-borne disease caused by phytoplasma in several crops. In Spain, it has been identified in various crops and weeds such as grapevine, pear, tomato, carrot, pepper, chicory, and strawberry, and appears to be ubiquitous in herbaceous plant host in several families. Rigorous control of stolbur in avocado should be implemented as soon as possible to avoid further disease development and subsequent economic damage to this industry.

References: (1) A. Batlle et al. Eur. J. Plant Pathol. 106:811, 2000. (2) X. Daire et al. Ann. Appl. Biol. 121:95, 1992. (3) X. Daire et al. Eur. J. Plant Pathol. 103:507, 1997.
First Report of Cylindrocarpon destructans as a Root Pathogen of Mediterranean Quercus Species in Spain
Authors: Sánchez M. E. , Lora F. , Trapero A.
Published: May 2007

Cylindrocarpon spp. have been described as producing root rot in Quercus spp. in forest nurseries, mostly when the host plants were weakened (1). To our knowledge, this is the first description of root rot of Mediterranean Quercus (Q. ilex, Q. suber, and Q. faginea) seedlings caused by C. destructans. In spring 2000, heavy mortality of Quercus seedlings was recorded in a nursery in southeastern Spain. The affected plants were 9 months old and growing in the open air in fertilized peat. Symptoms consisted of browning and wilting of leaves, with extensive necrosis of feeder roots. C. destructans (macroconidia averaging 36 × 6 μm, 1 to 3 septate; microconidia 10 × 3 μm; chlamydospores rough, single, or in chains, averaging 9 μm in diameter) was consistently isolated from the necrotic rootlets. Pathogenicity of one isolate from Q. faginea and of a mixture of isolates from the three affected Quercus spp. was determined. Fungal isolates were grown on potato dextrose agar plates for 1 month to allow chlamydospore production, and the inocula were prepared by mixing the contents of three colonized plates with 125 ml of sterile water. Six replicates of 12-month-old Q. ilex and Q. suber seedlings were inoculated by mixing the inoculum from the three plates with the potting medium prior to planting the seedling. All inoculated and control plants (only water added) were grown in a sand-lime-peat soil mixture under greenhouse conditions and watered as needed. After 5 weeks, all the inoculated plants showed extensive root necrosis accompanied by crown symptoms and rapid plant death. No symptoms were evident in control plants, and they produced new rootlets. No significant difference in pathogenicity was noted between the single isolate compared with the mixture of isolates, and the Quercus species did not significantly differ in susceptibility to root rot. C. destructans was easily recovered from necrotic roots.

Reference: (1) D. Brayford. Cylindrocarpon. Pages 103–106 In: Methods for Research on Soilborne Phytopathogenic Fungi. American Phytopathological Society, St. Paul, MN, 1992.
Occurrence of Severe Outbreaks of Leaf Mold Caused by Fulvia fulva in Greenhouse Tomatoes in Chile
Authors: Latorre B. A. , Besoain X.
Published: May 2007

Severe outbreaks of leaf mold, affecting as much as 100% of the plants, have occurred in greenhouse tomatoes (Lycopersicon esculentum Mill.) in the V Region in the central zone of Chile (32°50′ to 33°10′ latitude south) during the past 2 years. Symptoms consisted of yellow spherical to elongated leaf spots, first noticeable on the upper surface of older leaves, followed by leaf necrosis and defoliation. Invariably, an olive green-to-gray leaf mold developed on the under surface of the spots. No symptoms were observed on fruits and rarely occurred on petioles and stems. Isolation on acidified potato dextrose agar (APDA) consistently yielded dark green colonies of a very slow growing fungus that was identified as Fulvia fulva (Cooke) Cif. (=Cladosporium fulvum Cooke) (1). Identification was based on the presence of a dark septate mycelium, ovoid to ellipsoid conidia, usually one or two cells, pale or slightly yellow, 11 × 40 μm long, and the presence of mostly unbranched conidiophores that were broader at the tip. Conidia were produced in short chains, and a very distinctive hilum was always observed (1,3). Thin sections of leaf lesions revealed the presence of inter- and intracellular mycelia that protruded through the stomata forming a small stroma in the stomatal cavity from which the conidiophores were produced. Leaf inoculations of tomato cvs. Fortaleza and Cal-Ace with a mixture of mycelia and conidia from isolates Fv1 and Fv2 on APDA (approximately 106 propagules per ml) and with three different samples of conidia (106 conidia per ml) obtained directly from actively growing lesions resulted in the development of pale to dark yellow spots after 12 to 15 days of incubation under greenhouse conditions (temperatures ranging from 9 to 30°C). Leaf spots developed mainly on inoculated leaflets, but occasionally symptoms were obtained on other leaflets on the same leaf. Reisolations made from samples of artificially inoculated leaves always yielded F. fulvia on APDA. Therefore, it was concluded that F. fulvia was the cause of the severe outbreaks of tomato leaf mold found in central Chile. Previously, it has been reported in northern Chile (I Region approximately 2,000 km away) (2). To our knowledge, this is the first confirmed report of leaf mold on greenhouse tomato in central Chile.

References: (1) P. Holliday and J. L. Mulder. Fulvia fulva. No. 487 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1976. (2) F. Mujica and C. Vergara. Flora Fungosa Chilena. 2nd ed. Universidad de Chile, Facultad de Agronomía, Santiago, Chile, 1980. (3) A. F. Sherf and A. A. Macnab. Vegetable Diseases and Their Control, 2nd ed. John Wiley and Sons, New York, 1986.
First Report of Basal Stem Rot Caused by Pythium Group G on Kenaf in South Africa
Authors: Swart W. J. , Tesfaendrias M. T. , Botha W.
Published: May 2007

Kenaf (Hibiscus cannabinus L. Malvaceae) presents a source of high-quality cellulose fibers and is being investigated in South Africa for commercial production. In March 2001, 12 5-month-old kenaf plants grown from seed in experimental plots near Bloemfontein, South Africa, displayed large, black, sunken lesions (10 to 20 cm long) at the base of the stem, and severe root rot. A study was undertaken to characterize the pathogen, and to determine the relative susceptibilities of five kenaf genotypes being considered for commercial cultivation. Isolations from diseased tissue on malt extract agar consistently yielded a fungus identified as Pythium group G (1). Four-month-old kenaf plants were artificially inoculated in the field by inserting wooden toothpick tips colonized by the pathogen approximately 25 cm above soil level into the stems of 10 plants of each of five genotypes. Inoculation points were wrapped using Parafilm. The fungus was highly virulent to all five kenaf genotypes in two experiments, with mean cambial lesion lengths of 117, 119, 120, 122, and 139 mm at 7 days after inoculation for Tainung-2, Cuba 108, SF-459, El Salvador, and Everglades 41, respectively. Lesions ranged from 44 to 164 mm, with an overall mean of 124 mm for all five genotypes. No lesions developed in control plants. Although Everglades had the longest lesions, there were no significant differences (P < 0.05) among genotypes. Koch's postulates were completed by reisolating the fungus from all inoculated plants. To our knowledge, there are no published reports of Pythium group G causing stem or root rot of kenaf.

References: (1) M. W. Dick. Keys to Pythium. University of Reading Press, Reading, UK, 1990.
Pathogenic Characterization of Genotypes A and B of Phialophora gregata f. sp. sojae
Authors: Hughes T. J. , Chen W. , Grau C. R.
Published: May 2007

Genetic studies of Phialophora gregata f. sp. sojae, the causal agent of brown stem rot (BSR) of soybean, have led to the development of species-specific primers capable of separating isolates into two distinct genotypes, A and B. To determine whether genotypic characterization could be related to differences in BSR symptom expression, five soybean cultivars, Pioneer 9234, Corsoy 79 (both BSR susceptible), Williams, BSR 101, and Jack and plant introduction (PI) 437970 (all BSR resistant), were inoculated with a total of 27 isolates of each genotype in four greenhouse experiments conducted from February to November 2000. BSR severity was calculated as the percentage of symptomatic foliar, internal stem, and internal root tissue. Genotype A isolates caused significantly more severe (P < 0.0001) BSR foliar symptoms than genotype B isolates on Pioneer 9234, Corsoy 79, Williams, and BSR 101, while Jack and PI 437970 expressed minimal foliar symptoms regardless of isolate genotype. Overall, internal stem symptoms caused by genotype A isolates were more severe than those caused by genotype B isolates on Pioneer 9234, Corsoy 79, Williams, and BSR 101. Conversely, Jack and PI 437970 did not differ significantly in severity of stem symptoms when inoculated with isolates of genotype A or B. Internal root symptoms for genotype A isolates were generally more severe than for genotype B isolates on all soybean genotypes tested. Our data strongly suggest that A and B genotypes of P. gregata f. sp. sojae differ in the severity of symptoms they cause, and that these genotypes correspond to the Type I (defoliating) and Type II (nondefoliating), respectively, pathotypes previously proposed for this vascular pathogen of soybean.
Effects of Calcium Salts on the Cranberry Fruit Rot Disease Complex
Authors: Blodgett A. B. , Caldwell R. W. , McManus P. S.
Published: May 2007

Calcium salts were applied during the growing season to fresh-fruit cranberry beds to test their effects on cranberry fruit rot incidence and the incidence of specific fungi isolated from rotten and sound cranberry fruit at the time of harvest and after storage. Calcium salts did not affect fruit rot incidence, nor did they affect the recovery of specific fungi from berries. The field treatments did not result in higher calcium content in mature berries, nor did they affect the force required to penetrate the berry epidermis. Calcium propionate inhibited growth in vitro of Allantophomopsis cytisporea, A. lycopodina, Coleophoma empetri, Fusicoccum putrefaciens, and Physalospora vaccinii. Calcium chloride and calcium nitrate inhibited growth of Coleophoma empetri and Fusicoccum putrefaciens, but these salts enhanced growth of Physalospora vaccinii. P. vaccinii was the fungus most frequently isolated from rotten berries at the time of harvest. The fungi most frequently isolated from rotten berries after several weeks in storage varied among sites. P. vaccinii, which was common in sound fruit at harvest, persisted in sound fruit in storage but was also isolated frequently from rotten berries after storage. A. lycopodina and F. putrefaciens, which were isolated infrequently from sound berries at the time of harvest, were isolated frequently from rotten berries after storage. In two of four trials, no fungi were isolated from a large proportion of fruit that decayed in storage.
Relationship of Host Genotype to Bipolaris Leaf Blight Severities and Yield Components of Adlay
Authors: Chang Seog Won , Hwang Byung Kook
Published: May 2007

Leaf blight, caused by Bipolaris coicis, is one of the most destructive and major yield-limiting diseases of adlay (Coix lacryma-jobi var. ma-yuen). Adlay is used as an ornamental, and as a medicinal and cereal food in many countries. Field studies performed from 1997 to 1999 in Korea evaluated the resistance of 30 adlay genotypes to Bipolaris coicis and determined the relationship of cultivar resistance to leaf blight development and yield. Adlay response to leaf blight was quantitative rather than qualitative, varying greatly among cultivars or lines tested. Disease severity was lowest in Tsukuba B7, Tsukuba B15, and Muzu, and highest in Huksuk 1, Limgae, and Huksuk 2. Leaf position significantly affected disease severity, with lower leaves being more severely infected than upper leaves. Yield reductions of up to 52.4% for line Huksuk 2 were observed and were primarily associated with reductions in kernel numbers per plant, thousand kernel weight, and percent kernel ripeness. Loss of yield and yield components by leaf blight were less in resistant line Tsukuba B15 than in susceptible line Huksuk 2.
Effect of Treating Apple Trees with Acibenzolar-S-Methyl on Fire Blight and Expression of Pathogenesis-Related Protein Genes
Authors: Maxson-Stein Kimberly , He Sheng-Yang , Hammerschmidt Raymond , Jones Alan L.
Published: May 2007

Acibenzolar-S-methyl (ASM, Actigard 50 WG), a synthetic inducer of systemic acquired resistance (SAR) and pathogenesis-related (PR) proteins, was evaluated for the control of fire blight on apple trees in the field and for PR protein gene expression in apple seedlings in the greenhouse. Expression of putative genes related to SAR induction was elevated in ASM-treated apple seedlings 2 to 7 days after treatment; levels of PR-1 and PR-8 RNA were increased 10-fold and PR-2 RNA was increased 100-fold in ASM-treated seedlings over levels in untreated seedlings. Spurs and shoots on Jonathan trees sprayed with ASM at 75 mg a.i./liter at pink and at weekly intervals thereafter had significantly less fire blight than untreated trees, both from natural infection and following artificial inoculation with the pathogen. Less fire blight was observed on trees sprayed weekly with ASM than on trees sprayed biweekly. The severity of fire blight on inoculated shoots of Fuji apple decreased with increasing rates of ASM (0 to 300 mg a.i./liter), and ASM combined with streptomycin showed enhanced activity over ASM at 75 mg a.i./liter alone. In general, ASM was not superior to streptomycin for fire blight control, but integrating a weekly schedule of ASM, preferably at 150 mg a.i./liter, with a schedule of streptomycin designed for blossom blight control appears promising for overall improvement in fire blight control.
Fungi Associated with the Stalk Rot Complex of Pearl Millet
Authors: Wilson J. P.
Published: May 2007

Stalk rot is frequently observed in maturing, rust-infected pearl millet (Pennisetum glaucum). Fungi were isolated from internal stalk tissue, and their association with node discoloration and rust infection at different stages of plant maturity was determined to gain a greater understanding of stalk rot etiology. In 1995, stalk rot was observed in a breeding population of pearl millet. Stalks of 10 rust-infected plants were collected on each of three dates during grain fill. Frequency of symptomatic, discolored nodes was higher in the later sampling dates. Stalk sections from 119 discolored nodes were surface sterilized and plated onto agar media. Fungi most frequently isolated from symptomatic nodes were Bipolaris setariae (isolated from 47% of discolored nodes), Fusarium semitectum (28.6%), and F. moniliforme sensu lato (23.5%). Isolation frequency of these fungi differed (P < 0.05) with sampling date. In 1996 and 1997, the hybrid HGM 100 was evaluated at two dates of planting in each year. Ten stalks were sampled at each of four growth stages: panicle emergence, stigma emergence, milk, and hard dough. A total of 140 stalks was assessed for rust severity and for internal stalk discoloration at the nodes. The frequency of discolored nodes increased with plant maturation and was correlated (P < 0.01) with severity of rust infection. All nodes were plated on an agar medium, and a total of 1,512 isolates from 30 fungal genera or species were isolated from the 1,540 nodes of the sampled stalks. F. moniliforme was isolated most frequently (isolated from 23.5% of all nodes). Frequency of isolation of F. moniliforme from nodes within stalks increased with advancing maturity in the earlier dates of planting, but was not correlated with rust infection. B. setariae (isolated from 9.2% of all nodes) was more frequently isolated from plants at the dough stage in three plantings, and was correlated (P < 0.01) with rust severity. Trends in the frequency of isolation of other fungi were inconsistent between planting dates or among growth stages. Frequency of isolation of F. semitectum (isolated from 11.0% of all nodes) and Alternaria spp. (6.9% of all nodes) was correlated (P < 0.05) with rust severity. Frequency of isolation of Curvularia spp. (isolated from 7.0% of all nodes) was negatively correlated (P < 0.05) with rust severity. Isolation of Alternaria spp. and B. setariae was more frequently associated with node discoloration than was isolation of the other fungi. Stalk rot of pearl millet is the result of a complex of several fungi whose incidence was influenced by rust infection, plant maturation, and environmental factors associated with differences among years and dates of planting.
Biocontrol Efficacy of Antagonist Yeasts to Gray Mold and Blue Mold on Apples and Pears in Controlled Atmospheres
Authors: Tian Shiping , Fan Qing , Xu Yong , Liu Haibo
Published: May 2007

Biocontrol capability of the yeasts Trichosporon sp. and Cryptococcus albidus against Botrytis cinerea and Penicillium expansum was evaluated in apple (cv. Golden Delicious) and pear (cv. Jingbai) fruits at 1°C in air and under controlled atmospheres (CA) with 3% O2 + 3% CO2 or 3% O2 + 8% CO2. Trichosporon sp. controlled gray mold and blue mold of apple fruits more effectively than C. albidus (P < 0.05). Apple fruits treated with Trichosporon sp. and C. albidus had a lower incidence of gray mold rot than blue mold rot in the same storage conditions. Biocontrol efficacy of the yeasts for controlling gray mold and blue mold was better in apples than in pears. Populations of the yeasts in drop-inoculated wounds in fruits increased rapidly after 20 days at 1°C both in air and in CA conditions. There was no significant difference in colony diameters of the two pathogens cultured in 0 to 15% CO2 concentrations after 7 days at 20°C, but the colony diameter of both B. cinerea and P. expansum at 20% CO2 was significantly less than in other treatments (P < 0.05). CA with 3% O2 + 8% CO2 inhibited the pathogenic fungi more than CA with 3% O2 + 3% CO2.
Development of a Rapid Technique for the Evaluation of the Response of Brassica napus to Verticillium wilt
Authors: Steventon L. A. , Happstadius I. , Okori P. , Dixelius C.
Published: May 2007

Extensive efforts are being made to develop oilseed rape cultivars with resistance to Verticillium wilt. Evaluation of these cultivars involves either dipping roots of young plants in a conidial suspension followed by replanting in soil, or sowing the seed directly in artificially infested soil. These methods for screening for resistance take a long time and are expensive. The objective of this research was to develop a rapid and reliable method of screening cultivars for resistance to Verticillium wilt. A box test method in which 4-day-old seedlings were inoculated and grown under sterile conditions in double magenta boxes was developed. The Brassica napus cultivars Accord, Express, Hanna, and Libraska were inoculated with isolates of Verticillium longisporum or V. dahliae. The results from the box test method were compared with root-dip inoculation of seedlings grown in a soil mixture under greenhouse conditions. In addition, plants from the box test were randomly selected and transferred to pots containing sterile soil to permit comparison of plants from the box test at similar developmental stage with plants in the root-dip method. Disease evaluation was based on the number of days after transferring seedlings into the boxes that root browning, root and shoot blackening, and wilting of cotyledons developed. Additional disease evaluation was based on a 0 to 5 disease severity scale based on the percentage of wilted leaves (number) and/or the percentage of stunting (mm) of inoculated plants compared with noninoculated plants. Disease severity was higher on Hanna than on Express, and isolates of V. longisporum were more virulent than isolates of V. dahliae. There was a significant correlation (r = 0.93) of disease rating between the traditional root-dip method and the new box test method. Analysis of variance revealed that the interaction between cultivars and isolates was highly significant (P ≤ 0.01), whereas method of inoculation did not affect the results. In the box test, plants were rated after 25 days, which is at least 3.5 times more rapid than the root-dip method.
Differentiation of Pathogenic Groups of Xylella fastidiosa Strains with Whole-Cell Protein Profiles
Authors: Wichman R. L. , Hopkins D. L.
Published: May 2007

Whole-cell protein analyses of 75 Xylella fastidiosa strains by sodium dodecyl sulfatepolyacrylamide gel electrophoresis were compared, and variations in the protein banding patterns among the strains were observed. Based on the presence, absence, or difference in intensity of 10 protein bands within the 21.5 to 45.0 kDa molecular mass range, the strains could be subdivided into four distinct pathogenic groups and two miscellaneous groups whose members were pathogenic to various different hosts. Group 1 was the Pierce's disease of grapevine pathogenic group. Although 4 of these 45 strains had hosts of origin other than grapevine, they all produced Pierce's disease symptoms. Uniform, distinct protein profiles also occurred with group 2 (elderberry leaf scorch strains), group 3 (oak leaf scorch strains), and group 4 (oleander leaf scorch strains). Groups 5 and 6 were made up of strains pathogenic to almond, blackberry, lupine, mulberry, periwinkle, elm, and plum. Thus, whole-cell protein analysis was shown to be a rapid and consistent method for identifying four pathogenic groups of X. fastidiosa strains.
Interactions Between Myxobacteria, Plant Pathogenic Fungi, and Biocontrol Agents
Authors: Bull C. T. , Shetty K. G. , Subbarao K. V.
Published: May 2007

Myxobacteria are soil dwelling gram-negative gliding bacteria that form fruiting bodies containing myxospores. Although myxobacteria produce a wide range of antibiotics and lytic enzymes that assist in their ability to prey on other microorganisms, their role in agriculture has received little attention. Myxococcus spp. were isolated from soils in organic and conventionally managed strawberry production and transplant fields in the absence of soil fumigation. Fumigation with methyl bromide and chloropicrin virtually eliminated these organisms from soil. However, soil fumigation had no effect on the frequency of isolation of Myxococcus spp. from strawberry roots. Six Myxococcus spp. were tested in vitro against eight soilborne plant pathogenic fungi (Cylindrocarpon spp., Fusarium oxysporum f. sp. apii, Phytophthora capsici, Pythium ultimum, Rhizoctonia spp., Sclerotinia minor, Verticillium albo-atrum, and V. dahliae) and against two fungal biological control agents (Gliocladium virens and Trichoderma viride). Phytophthora capsici, Pythium ultimum, Rhizoctonia spp., S. minor, and T. viride were completely inhibited by all of the Myxococcus spp. tested. F. oxysporum f. sp. apii was the least sensitive to the myxobacteria, and no inhibition occurred with some Myxococcus spp. Inhibition of the other fungi tested was variable. Myxococcus coralloides inhibited nearly all the fungi tested. The ability of bacterial biological control agents to produce antibiotics and other secondary metabolites determined whether or not they were lysed by myxobacteria. Secondary metabolite production regulated by gacS protected Pseudomonas fluorescens strain CHA0 from lysis by myxobacteria. More specifically, phenazine antibiotics produced by Pseudomonas aureofaciens strain 30–84 protected it from lysis.
First Report of the Root-Knot Nematode Meloidogyne kralli in Switzerland
Authors: Karssen G. , Grunder J.
Published: May 2007

The root-knot nematode Meloidogyne kralli Jepson was originally described from Carex acuta L. near the Elva River in Estonia (3). This species, which was rarely detected in Russia, Poland, and the UK, was observed on Cyperaceae hosts in very wet, sandy, peat, and silt soils (1). Although marked as a rare and unusual root-knot nematode, a wider European distribution was hypothesized, particularly for natural habitats where Cyperaceae are common (4). In October 2001, we finished the first root-knot nematode survey in Switzerland, which included a protected peat-moss area named Hüttensee near Wädenswil at 660 m altitude. Small smooth galls were observed on the roots of different Carex species. These galls contained several hatched second-stage juveniles, partly swollen juveniles, and a few swollen adult females with small egg masses. No protruding egg masses were observed outside the galls and no males were observed inside. Second-stage juveniles together with males also were isolated from adhering soil. The identification of these nematodes as M. kralli was based on female and second-stage juvenile morphology, and female malate dehydrogenase and esterase isozyme phenotypes (2,4). M. kralli is the only root-knot nematode known to parasitize Cyperaceae hosts, although this nematode has other monocotyledonous hosts, such as Hordeum vulgare L. (1). To our knowledge this is the first published report of M. kralli from the Alps.

References: (1) M. W. Brzeski. Nematodes of Tylenchina in Poland and Temperate Europe. Page 242 in: Muzeum i Instytut Zoologii PAN, Warszawa, Poland, 1998. (2) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6, 1985. (3) S. Jepson. Rev. Nematol. 6:239, 1983. (4) G. Karssen and T. van Hoenselaar. Nematologica 44:713, 1998.
First Report of Powdery Mildew on Euryops pectinatus in Italy
Authors: Garibaldi A. , Minuto A. , Bertetti D. , Gullino M. L.
Published: May 2007

Euryops pectinatus is grown in Italy for landscape use in parks and gardens. In 2001, severe outbreaks of a previously unknown powdery mildew were observed in commercial farms located in Albenga (northern Italy). All green parts (leaves, stems, and petioles) became covered with a white mycelium. Infections were particularly severe on the upper leaf surface. With progress of the disease, infected leaves turned yellow and died. The presence of powdery mildew infections on leaves and stems only rarely was linked to growth reduction. Conidia were hyaline, cylindric to slightly doliform, did not show fibrosin bodies, borne in chains, and measured 24 to 41 × 12 to 20 μm. Cleistothecia were not observed. The pathogen was identified as Oidium sp. subgen. Fibroidium (1). Pathogenicity was confirmed by gently pressing diseased leaves on leaves of healthy E. pectinatus plants. Inoculated plants were maintained in a growth chamber at 20 to 24°C. After 12 to 14 days, powdery mildew symptoms developed. A similar disease of E. pectinatus was observed in 1999 in California and identified as being caused by Podosphaera (Sphaerotheca) fusca (2). It is possible that the powdery mildew observed in Italy belongs to the same species, also considering that recently the two genera, Podosphaera and Sphaerotheca, have been unified in the genus Podosphaera (1).

References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) G. S. Saenz et al. Plant Dis. 84:1048, 2000.
First Report of Phoma exigua on Centaurea solstitialis (Asteraceae) in Russia
Authors: Widmer T. , Castlebury L. , Rossman A.
Published: May 2007

Phoma exigua Desm. (teleomorph Didymella exigua (Niessl) Sacc.) was isolated from wilted Centaurea solstitialis L. (yellow starthistle) plants displaying necrosis of the crown that were found near Krasnodar, Russia. The fungus was identified using morphological and cultural characteristics (1,2) and confirmed by sequencing the complete internal transcribed spacer region of the nuclear rDNA (GenBank Accession No. AY089978). P. exigua is a relatively common soilborne fungus that is weakly pathogenic on a diverse range of primarily dicotyledonous plants throughout the world (1). To our knowledge, it has never been reported previously on members of the genus Centaurea. Yellow starthistle is native to eastern Europe and the Mediterranean Region, and is now a noxious weed in North America for which P. exigua is being investigated as a potential biological control agent. Repeated pathogenicity studies (N = 30) resulted in a mortality of 80 and 93% within 7 days when 1-week-old seedlings were transplanted in soil infested with P. exigua-colonized wheat seed at rates of 6.7 and 10% (vol/vol), respectively. Symptoms of the seedlings included necrosis of the stem and wilting of the seedling. Pycnidia were observed in the roots of dead seedlings. The isolate of P. exigua has been deposited as a dried specimen at the U.S. National Fungus Collections, Beltsville, MD (BPI 841766) and as a living culture at the CBS collection in Utrecht, Netherlands (CBS 110211).

References: (1) G. Morgan-Jones and K. B. Burch. Mycotaxon 32:477, 1988. (2) H. A. Van Der Aa et al. Persoonia 17:435, 2000.
First Report of Strawberry Anthracnose (Colletotrichum acutatum) in Strawberry Fields in New York
Authors: Turechek W. W. , Heidenreich C. , Pritts M. P.
Published: May 2007

Strawberry plants with red to black, sunken, fusoid lesions on runners and leaf petioles were found in several first-year plantings in grower's fields in western New York in 2000. Affected cultivars included Honeoye, Jewel, and Primetime. Sections of petiole were excised from lesion margins and plated on potato dextrose agar (PDA) amended with chloramphenicol, streptomycin sulfate, and tetracycline hydrochloride at 100 μg/ml. The fungus, Colletotrichum acutatum (J.H. Simmonds), was consistently isolated and identified based on conidia morphology and its growth rate in culture relative to reference cultures of C. acutatum, C. gloeosporoides, and C. fragariae (1,2). The average size of conidia produced on PDA was 15.2 × 5 μm. For each of six isolates, three plants each of six-week-old Honeoye and Kent were spray inoculated with a conidial suspension (106 conidia per ml), and petioles, leaves, and crowns were stabbed with a sterile pin following inoculation. After 14 days at 20 to 25°C, petioles and leaves on all inoculated plants developed lesions consistent with those seen in the field. The fungus was readily reisolated from leaf and petiole lesions. Subsequent inoculations on detached fruit under the same conditions yielded circular, sunken, dry lesions that produced a salmon-colored, slimy, spore mass typical of C. acutatum. This is the second report of strawberry anthracnose in the northeastern United States (3) and to our knowledge, the first report in New York.

References: (1) J. A. García Muñoz et al. Mycologia 92:288, 2000. (2) P. S. Gunnel and W. D. Gubler. Mycologia 84:157, 1992. (3) J. A. LaMondia. Plant Dis. 75:1286, 1991.
Yield Loss Assessment in Canola: Effects of Brown Girdling Root Rot and Maggot Damage on Single Plant Yield
Authors: Klein-Gebbinck H. W. , Woods D. L.
Published: May 2007

Single plant yield loss due to brown girdling root rot (Rhizoctonia solani) and cabbage root maggot (Delia spp.) damage was assessed in canola (Brassica rapa cvs. Reward and Tobin) to quantify the effects of root rot on yield and determine whether yield losses due to root rot are compounded by maggot damage. At crop ripening during 1998 and 1999, 2,000 plants from six growers' fields were scored for both root rot and maggot injury. The assessed roots were separated into eight categories constructed by crossing four classes of root rot severity based on degree of girdling and two classes of maggot damage based on percentage of the root surface with maggot tunnels. A ninth category was defined for partially to completely decayed roots for which it was not possible to determine maggot damage. There was no root rot by maggot injury interaction on any of the yield parameters measured. Furthermore, maggots had no adverse effects on yield at the observed damage levels. In contrast, plant weight, seed yield, harvest index, seed size, but not oil content were reduced on plants with completely decayed roots. On average, seed yield was not reduced on plants with roots with nongirdling lesions and superficial nonsinking girdling lesions, but was reduced by 17% on plants with roots with girdling and sinking lesions, and by 65% on plants with decayed taproots. Over 2 years, yield losses in growers' fields ranged from 1 to 5%.
Molecular Characterization of Tobacco leaf rugose virus, a New Begomovirus Infecting Tobacco in Cuba
Authors: Domínguez M. , Ramos P. L. , Echemendía A. L. , Peral R. , Crespo J. , Andino V. , Pujol M. , Borroto C.
Published: May 2007

Tobacco (Nicotiana tabacum L.) is the main raw material for the cigar industry and one of the most important crops in Cuba comprising 49,654 ha. During the past 20 years, foliar rugosity and stunting symptoms have been observed in several tobacco producing areas. These symptoms were correlated with the presence of typical geminivirus nuclear inclusions and the transmission of the causal agent by whiteflies (Bemisia tabaci Genn) (1). To identify the suspect geminivirus, diseased leaf samples were collected in Havana province in 2000 and 2001. Sap extracts or leaf pieces were used to inoculate healthy tomato and tobacco plants by mechanical and graft inoculation procedures. Characteristic symptoms were reproduced in tobacco plants only by grafting (8 to 10 plants). DNA extracts from symptomatic plants were analyzed by Southern blot and polymerase chain reaction. The presence of a bipartite begomovirus was supported by the observation of hybridization signals (1.6 kb to 3 kb) at low stringency to probes derived from DNA-A and DNA-B of Taino tomato mottle virus. Furthermore, typical begomovirus amplicons of approximately 1.4 kb and 1.2 kb were amplified using the primer sets PAL1v1978-PAR1c715 and PAL1c1960-PAR1v722 (2), respectively. Amplicons were cloned, and their nucleotide sequences (nt) obtained from two clones each. Sequence for component A was assembled, and some fragments were compared with those for other begomoviruses using CLUSTAL W. For the CP gene (756 nt) (GenBank Accession No. AJ488768), the comparison revealed the highest percentages of nt identity with Sida golden mosaic virus from Florida (SiGMV-F, GenBank Accession No. AF049336) (86%), Tomato mottle virus (GenBank Accession No. L14460) (83.5%), and the yellow vein strain of Sida golden mosaic virus from Honduras (GenBank Accession No. Y11099) (83.3%). In addition, the percentages of nt identity obtained using the core region (a 540-nt fragment located between positions 147 and 687) of the CP gene from the tobacco virus were calculated. The best scores were as follows: SiGMV-F, 87.8%; Jatropha mosaic virus (JMV) from Puerto Rico (GenBank Accession No. AF058025), 86.9%; and Tomato rugose mosaic virus (GenBank Accession No. AF291705), 86.3%. Finally, comparisons of the common region (CR, 144 nt) revealed the highest values with JMV from Jamaica (JMV-JM) DNA-A and DNA-B (GenBank Accession Nos. AF324410 and AF324411; 89% and 91.1%, respectively). Interestingly, the CR analysis revealed the presence of the Ori-associated iterative motif GGGGT, which is the same in the CR of JMV-JM. Although the data suggest that the tobacco begomovirus is related to the JMV-JM isolate, it is a new species, and the name of Tobacco leaf rugose virus (TbLRV) is proposed.

References: (1) S. Quintero and J. Santiesteban, Agrotec. Cuba 11(1), 1979. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.