bluuebunny/crossref_metadata_2025 huggingface dataset:
Symptomatology of Barley Yellow Dwarf Virus-RMV Infection in Sweet Corn
Authors: Itnyre R. L. C. , D'Arcy Cleora J. , Pataky J. K. , Pedersen W. L.
Published: May 2007

Infection of sweet corn (Zea mays L.) by barley yellow dwarf viruses (BYDVs) caused different symptoms on hybrids with shrunken-2 (sh-2) when compared with hybrids with sugary-1 (su-1) endosperm mutations. Sweet corn hybrids inoculated with BYDV-RMV in Urbana, IL, developed either yellow or red-purple leaf symptoms similar to those caused by phosphorus and/or potash deficiency (1). In a field trial near Rochelle, IL, 329 of 339 sweet corn hybrids naturally infected by BYDV exhibited one or the other of these symptoms. Eighteen of the hybrids with severe symptoms were tested for two strains of BYDVs in enzyme-linked immunosorbent assays (1). All of the hybrids tested were positive for BYDV-RMV; none were positive for BYDV-PAV. Symptoms on su-1 hybrids were typically characterized by dark red to purple coloration of leaf margins from the tip down to the mid-leaf. Leaves of sh-2 hybrids exhibited chlorosis in a similar pattern. A single sh-2 hybrid exhibited red-purple leaf symptoms, probably as a result of a crossover between the anthocyanin production (a1) and sh-2 genes, which are linked about 0.25 map units apart on chromosome 3 (2). Infection of sh-2 sweet corn hybrids by BYDV-RMV is most likely to induce chlorosis, whereas infection of su-1 sweet corn hybrids can result in either chlorosis or red-purple discoloration of leaves. Sweet corn hybrids with these symptoms should be tested for BYDVs, particularly the RMV strain.

References: (1) R. L. C. Itnyre et al. Plant Dis. 83:566, 1999. (2) E. B. Mains. J. Hered. 40:21, 1948.
First Report of Verticillium dahliae Causing Artichoke Wilt in California
Authors: Bhat R. G. , Subbarao K. V. , Bari M. A.
Published: May 2007

In mid-August 1998, artichoke (Cynara scolymus L.) plants of cultivar Imperial Star in a field in the Salinas area of the central coast of California developed wilt symptoms. The plants were stunted with chlorotic, drooping, and dried leaves near the bottom and middle of the plants as previously described in Italy (1). Diseased plants produced smaller edible buds and, in severe cases, buds were discolored with dried outer bracts. Roots exhibited the characteristic vascular discoloration of Verticillium infection. In one part of the infested field, artichoke was near harvest with 85% of plants showing wilt symptoms with vascular discoloration whereas the other part had a 60-day-old crop with 98% of plants infected. Yield in the field was reduced by as much as 50%. Verticillium dahliae was isolated from infected plant samples on NP-10 medium (2), and isolates were single spored before storing on potato dextrose agar at 4°C. Identity of the pathogen was confirmed based on colony morphology and formation of microsclerotia. In root-dip inoculation tests in the greenhouse, two V. dahliae isolates from artichoke infected 1-month-old artichoke seedlings that wilted within 6 weeks of inoculation. V. dahliae was reisolated from plants showing vascular discoloration. Cross-inoculation studies revealed that artichoke isolates caused a moderate level of disease in lettuce, but only a trace of vascular discoloration in cauliflower. Lettuce isolates caused a severe wilt in artichoke. Cauliflower isolates did not cause wilt in lettuce and caused only slight vascular discoloration in artichoke. This is the first report of a Verticillium wilt of artichoke in California.

References: (1) M. Cirulli et al. Plant Dis. 78:680, 1994. (2) L. H. Sorensen et al. Phytopathology 81:1347, 1991.
Genetic Analysis of Meloidogyne arenaria Race 1 Resistance in Tobacco
Authors: Ng'ambi Tenson B. S. , Rufty Rebeca C. , Barker Kenneth R.
Published: May 2007

Inheritance of resistance to the peanut root-knot nematode (Meloidogyne arenaria (Neal) Chitwood race 1) was investigated in the flue-cured tobacco cv. Speight G 28 and the breeding lines 81-RL-2K and SA 1214. The genetic relationship of this resistance in Speight G 28 to the resistance of the same cultivar to races 1 and 3 of M. incognita was also studied. Crosses were made between the root-knot nematode-susceptible flue-cured tobacco cv. NC 2326 and the three resistant genotypes. Parental, F1, F2 and backcross generations (BC1P1, BC1P2) were grown for each cross in randomized complete block designs with five replications in the greenhouse. Data indicated that resistance to M. arenaria race 1 in the three resistance sources is conditioned by a single dominant gene, but this resistance is partial compared to that for M. incognita races 1 and 3. Further, resistance to races 1 and 3 of M. incognita and resistance to M. arenaria race 1 in cv. Speight G 28 appear to be controlled by the same gene. These results, combined with the absence of segregation in the F2 populations of the crosses between resistant parents 81-RL-2K × SA 1214, 81-RL-2K × Speight G 28, and SA 1214 × Speight G 28, suggest allelism of resistance among these genotypes.
Association of Phialophora gregata with Fusarium solani f. sp. pisi in Garbanzo Beans in California
Authors: Smith S. N.
Published: May 2007

In 1992, a vascular disease was found in two fields of cultivar UC-15 garbanzo beans (Cicer arietinum). The fields were located on the central coast of California and Phialophora gregata was consistently isolated from the aboveground tissue in the host UC-15 plants. Diseased patches in the fields mimicked the more common Fusarium wilt with its discolored vascular tissue in the stems, but in these instances P. gregata was the sole fungus that grew out of the tissue after 5 to 8 days of incubation on isolation agar. Greenhouse pathogenicity tests yielded only minor symptoms whether a dip technique or stem puncture inoculations were used. In subsequent years it was noted that this disease was observed only in garbanzo fields where a pea crop (Pisum sativum) had been previously grown. Further isolation from small foot and root lesions of diseased field plants revealed that they were infected with Fusarium solani f. sp. pisi (Fsp) in addition to P. gregata. In greenhouse experiments with a combination of soilborne Fsp and/or stem inoculations with P. gregata, both pathogens infected the host. The symptoms from both pathogens, the strongest including occasional plant death, were similar to those observed in the fields. The effect was more than additive. Neither pathogen alone caused severe damage. In these tests Fsp was reisolated from root and foot cortical tissue along with P. gregata from stem vascular tissue near the top of the plants. Peas were an important crop along the central coast long before garbanzo beans were grown there. Fsp, a pathogen of both pea and garbanzo bean (1), has been known to attack garbanzos there since 1973 (2). The presence of yet another vascular disease of significance in this coastal area, besides those caused by Fusarium oxysporum f. sp. ciceri and Verticillium dahliae, has not been previously noted. Help in identification of P. gregata came from Diane Fogle, California Department of Food and Agriculture, Sacramento.

References: (1) J. M. Kraft. Plant Dis. Rep. 53:110, 1969. (2) F. V. Westerlund Jr., et al. Phytopathology 64:432, 1974.
First Report of Sudden Death Syndrome Caused by Fusarium solani f. sp. glycines on Soybean in Pennsylvania
Authors: Pennypacker B. W.
Published: May 2007

A small, circular patch of soybean (Glycine max) showing symptoms consistent with sudden death syndrome (SDS) (2) was noted on July 25, 1998, in a producer's field in Jersey Shore, PA. Foliar symptoms included interveinal chlorosis and necrosis, leaf cupping, and leaf abscission. The vascular cylinder of roots and stems had areas of reddish-brown discoloration. A slow-growing Fusarium sp., which produced a bluish-purple color on potato dextrose agar, was isolated from the roots of several symptomatic plants. The fungus was identified as Fusarium solani by The Fusarium Research Center, The Pennsylvania State University. Koch's postulates were tested on soybean cultivars A2506, Stine 3171, Pioneer 9305 and 9306, and Jack. Five plants per cultivar were inoculated at growth stage V1 by pouring 35 ml of a 4 × 107 spores per ml suspension on the growth mix in each pot. Five plants per cultivar were treated similarly with sterile water. Foliar symptoms of SDS began to appear 3 weeks after inoculation. Seven weeks after inoculation, symptoms of interveinal chlorosis and/or necrosis, leaf cupping, and occasional leaf abscission were apparent on the inoculated plants and on several noninoculated plants. The percentage of the plant showing symptoms was recorded and converted to the 0 to 5 scale (in which 0 = 0%, 1 = 1–10%, 2 = 11–30%, 3 = 31–40%, 4 = 41–90%, and 5= 91–100% of the leaf area affected) used by Rupe (3). Regardless of the rating method, there was a significant difference (P = 0.0001) between inoculated and noninoculated plants. There were no significant differences among cultivars. Roots of the inoculated plants were frequently discolored, in contrast to those of the noninoculated plants. F. solani was isolated from the roots of 97% of the inoculated plants and 23% of the noninoculated plants. Fungus gnats were suspected of spreading the pathogen to the noninoculated plants (1). F. solani f. sp. glycines causes SDS in soybean and its identity is confirmed by the symptoms produced on soybean (2). The symptoms produced when soybean plants were inoculated in the greenhouse were consistent with those of SDS (2) and indicate that the F. solani isolate recovered from symptomatic plants in the field was F. solani f. sp. glycines. This is the first documented occurrence of SDS on soybean in Pennsylvania.

References: (1) D. W. Kalb and R. L. Millar. Plant Dis. 70:752, 1986. (2) K. W. Roy et al. Plant Dis. 81:1100, 1997. (3) J. C. Rupe. Plant Dis. 73:581, 1989.
First Report of Colletotrichum truncatum on Alfalfa in Turkey
Authors: Eken C. , Demirci E.
Published: May 2007

During the summer of 1997 and 1998, a pathogen identified as Colletotrichum truncatum (Schwein.) Andrus & W.D. Moore was isolated from lesions on stems of alfalfa (Medicago sativa L.) plants in Erzurum, Turkey. Typical symptoms on stems of mature plants were large, sunken, irregularly shaped black lesions. Twenty-eight cultures of C. truncatum were isolated from stem lesions. Acervuli containing spores and dark setae were observed within lesions. Conidia were hyaline, one-celled, falcate to nearly straight with a prominent clear area in the center of highly granular cytoplasm, and measured 16.3 to 20.6 × 3.1 to 4.5 μm. These morphological characteristics were consistent with the description of C. truncatum (1). The pathogenicity of two isolates was determined on alfalfa cv. Bilensoy. Alfalfa seedlings (6-week-old) were inoculated with a conidial suspension of the fungus (1.4 × 107 conidia per ml), incubated in a moist chamber for 3 days, and subsequently transferred to growth chambers maintained at 25°C with a 12-h photoperiod. Ten plants were inoculated with each isolate. Symptoms first appeared on stems 12 days after inoculation. Sunken, irregularly shaped black lesions occasionally girdled stems of plants inoculated with C. truncatum. Symptoms did not appear on stems of control plants inoculated with sterile distilled water. C. truncatum was reisolated from symptomatic tissue. This is the first report of C. truncatum on alfalfa from Turkey.

Reference: (1) B. C. Sutton. 1992. Pages 1–27 in: Colletotrichum Biology, Pathology and Control. J. A. Bailey and M. J. Jeger, eds. CAB International, Wallingford, U.K.
First Report of Azalea Petal Blight Caused by Pestalotiopsis guepini in Argentina
Authors: Rivera M. C. , Wright E. R.
Published: May 2007

The most important azalea (Rhododendron spp.) growing area in Argentina is located in the outskirts of Buenos Aires. A disease of the azalea flower was detected during surveys conducted during September 1998. Irregular brown spots were uniformly distributed on petals and resulted in a flower blight that did not lead to abscission of petals. Pieces of infected petals were surface-sterilized for 1 min in 2% NaOCl, plated on potato dextrose agar, and incubated at 24 ± 2°C. Pure cultures were identified as Pestalotiopsis guepini (Desmaz.) Steyaert (synamorph P. guepini Desmaz.) based on morphological characteristics (1,2). Inoculation for pathogenicity testing was carried out by spraying a conidial suspension (1 × 106 conidia per ml) on plants with previously punctured petals. Inoculated plants with unwounded flowers, as well as noninoculated controls, were included. Plants were incubated in moist chambers at 24°C. Symptoms appeared on all punctured flowers within 4 to 5 days. Petals were blighted by 9 days after inoculation and were covered with black acervuli by 12 days after inoculation. Unwounded and noninoculated controls remained symptomless. The pathogen was reisolated from inoculated flowers, completing Koch's postulates. Pathogenicity of P. guepini on azalea leaves in Argentina was reported in 1991. This is the first report of P. guepini causing disease on azalea flowers in Argentina.

References: (1) J. E. M. Mordue. CMI Descr. Pathog. Fungi Bact. No. 320, 1971. (2) B. C. Sutton. 1980. The Coelomycetes. Commonwealth Mycological Institute, Kew, England.
First Report of Stem Canker Caused by Alternaria alternata on Cotton
Authors: Laidou I. A. , Koulakiotu E. K. , Thanassoulopoulos C. C.
Published: May 2007

A stem blight of cotton (Gossypium hirsutum L.) was observed on plants of cv. 132 in the district of Ammoudia near Serres in northern Greece. Symptoms of the disease include cankers on the stem, leaf spots, and boll rots. Affected plants show early defoliation and maturing, as well as total or partial necrosis. Symptoms on stems include dark brown, circular spots that enlarge rapidly. The center of the lesions sink to form a canker. Gradually the spots become elliptical, and the tissues split the stem longitudinally, resulting in the total or partial death of the plant. The fungus isolated from infected stem tissues was identified as typical Alternaria alternata (Nees:Fr.) Keissler, based on morphological characteristics of conidia, which are produced in a loose three-dimensional tuft of branching chains (2). Pathogenicity tests were conducted by inoculating 50 cotton stems with 5-mm disks from 9-day-old cultures on potato dextrose agar at 25°C. Each stem was inoculated with three disks, and plants were placed at room temperature for 10 days for disease development. Inoculated plants exhibited more than 95% disease incidence, and frequency of reisolation was more than 70%. A. alternata is commonly known as a leaf spot, boll rot, and seedling blight pathogen of cotton. The only reported stem blight pathogen of cotton is A. macrospora (1). This is the first report of typical A. alternata as the cause of stem blight on cotton.

References: (1) L. Ling and F. Y. Yang. Phytopathology 31:664, 1941. (2) E. G. Simmons. Mycotaxon 48:109, 1993.
Soybean Cyst Nematode Reproduction in the North Central United States
Authors: Wang J. , Donald P. A. , Niblack T. L. , Bird G. W. , Faghihi J. , Ferris J. M. , Grau C. , Jardine D. J. , Lipps P. E. , MacGuidwin A. E. , Melakeberhan H. , Noel G. R. , Pierson P. , Riedel R. M. , Sellers P. R. , Stienstra W. C. , Todd T. C. , Tylka G. L. , Wheeler T. A. , Wysong D. S.
Published: May 2007

An experiment was conducted in Heterodera glycines-infested fields in 40 north central U.S. environments (21 sites in 1994 and 19 sites in 1995) to assess reproduction of this nematode. Two resistant and two susceptible soybean cultivars from each of the maturity groups (MG) I through IV were grown at each site in 6.1 m by 4 row plots. Soil samples were collected from each plot at planting and harvest and processed at Iowa State University to determine H. glycines initial (Pi) and final (Pf) population densities as eggs per 100 cm3 of soil. Overall, reproduction (Pf/Pi) of H. glycines on susceptible cultivars in all MG was similar. Reproduction was higher on MG III and IV susceptible cultivars than on those in MG I and II. Resistant MG I and II cultivars reduced nematode population densities more consistently than those in MG III and IV. Reproduction of the nematode was similar among sites within the same maturity zone (MZ), defined as the areas of best adaptation of the corresponding MG. Nonetheless, careful monitoring of nematode population densities is necessary to assess changes that occur over time in individual fields.
Molecular Identification of Fungi Associated with Vascular Discoloration of Soybean in the North Central United States
Authors: Harrington T. C. , Steimel J. , Workneh F. , Yang X. B.
Published: May 2007

Brown stem rot is a common but poorly understood vascular wilt disease of soybean. In order to more clearly delimit the causal agent (Phialophora gregata) and distinguish it from other morphologically similar fungi from discolored soybean stems, fungi were isolated on a semi-selective medium from discolored and non-discolored soybean stems collected at random across Iowa, Illinois, Minnesota, Missouri, and Ohio. A total of 11 fungi were commonly isolated and characterized based on colony morphology and DNA sequences of the internal transcribed spacer region of the rDNA operon. Phomopsis longicolla was the most frequently isolated fungus, but it was isolated more commonly from lightly discolored or non-discolored stems than from discolored stems. Phialophora gregata was the next most frequently isolated fungus and was isolated more commonly from discolored stems and more commonly in 1996 than in 1995, which had a warm growing season and relatively little brown stem rot. In inoculation experiments, only P. gregata was capable of causing the vascular discoloration and leaf symptoms typical of brown stem rot; none of the seven isolates could be considered non-defoliating. Two other fungi, Plectosphaerella cucumerina and Gliocladium roseum, were similar in colony morphology to Phialophora gregata but were not pathogenic to soybean, and these may be the same species as those referred to by earlier workers as Acremonium spp. or the non-defoliating form of P. gregata.
Pathogenicity of Pythium Populations from Corn-Soybean Rotation Fields
Authors: Zhang B. Q. , Yang X. B.
Published: May 2007

Corn and soybean have been rotated for decades in the north central regions of the United States, but it is unknown how the use of long-term rotation affects the population of soilborne fungi pathogenic to both crops. Pythium populations were obtained from 73 commercial corn-soybean rotation fields in Iowa from 1993 to 1995. A total of 163 Pythium isolates were obtained from soil, diseased soybean seedlings, or diseased corn seedlings, and these isolates were pooled into six populations according to the source of samples. The isolates were evaluated for their aggressiveness on corn and soybean for each population. Regardless of the source of sampling, each population had many Pythium isolates that were highly aggressive on both crops. Seventy-one percent of the isolates from soil were pathogenic, and 29% were highly aggressive on both crops. Three populations of Pythium isolates were obtained from diseased soybean seedlings. Eighty-five percent of those isolates were pathogenic, and 49 to 64% were highly aggressive on corn and soybean. Of the isolates obtained from diseased corn seedlings, 87% were pathogenic and 43% were highly aggressive on corn and soybean. For each Pythium population, aggressiveness on soybean and corn (measured by disease index) were highly correlated. Further, 23 P. ultimum isolates were identified from diseased soybean seedlings and tested for pathogenicity on corn and soybean. Disease index of the isolates varied, but the correlation between disease indices on the two crops was significant (r = 0.75, P < 0.001). The study suggests that long-term corn-soybean rotation fields contain many Pythium isolates that are highly aggressive on seedlings of both crops.
Postinfection Activity of Selected Late Blight Fungicides
Authors: Johnson Dennis A. , Cummings Tom F. , Geary Brad
Published: May 2007

Two sets of experiments were done in the greenhouse with ‘Russet Burbank’ potatoes infected with Phytophthora infestans. The first determined the effectiveness of selected late blight fungicides in restricting lesion length and spore production when applied after stem lesions had occurred on potted plants. The second quantified the curative activity of selected fungicides applied 12 to 48 h after inoculation of excised leaves with P. infestans. Such information may be beneficial in selecting an effective fungicide for late blight management when symptoms of the disease are present in a field. Expansion of established stem lesions was consistently restricted by one application of either dimethomorph plus mancozeb or metiram plus triphenyltin hydroxide. Sporulation on established stem lesions was consistently inhibited by either one application of dimethomorph plus mancozeb or cymoxanil plus mancozeb. Two applications of propamocarb hydrochloride plus chlorothalonil were required to restrict lesion expansion and inhibit sporulation. Size and number of lesions and sporulation on leaflets were reduced when propamocarb hydrochloride plus chlorothalonil was applied up to 48 h after inoculation.
Differentiation of Tilletia Species by rep-PCR Genomic Fingerprinting
Authors: McDonald J. G. , Wong E. , White G. P.
Published: May 2007

The potential of repetitive-sequence-based polymerase chain reaction (rep-PCR) fingerprinting of fungal genomic DNA as a rapid and simple alternative to random amplified polymorphic DNA (RAPD) analysis in the study of phylogenetic relationships, and also as a diagnostic method, was investigated with species of Tilletia. DNA primers (BOX, ERIC, and REP) corresponding to conserved repetitive element motifs, originally described in prokaryotes, were used to generate genomic fingerprints of T. indica, T. walkeri, T. controversa, T. laevis, T. tritici, T. goloskokovii, T. barclayana, and members of the T. fusca complex. Computer-assisted analysis of the database of combined fingerprints clearly distinguished each taxon and indicated phylo-genetic relationships consistent with previously reported RAPD analyses. There were three main clusters with isolates showing 35 to 40% similarity. Group 1 included T. indica and T. walkeri; group 2 included members of the T. fusca complex, as well as T. controversa, T. laevis, T. tritici, and T. goloskokovii; and group 3 included only T. barclayana. If, as is likely, the conserved repetitive element motifs on which this technique is based are widespread or universal in fungal species, rep-PCR shows strong potential, not only as a simple generic taxonomic tool, but also as a diagnostic method.
Influence of Moisture and Temperature on Infection of Canada Thistle by Alternaria cirsinoxia
Authors: Green S. , Bailey K. L.
Published: May 2007

Relative humidity (RH), temperature, continuous leaf wetness, and intermittent leaf wetness were evaluated for their influence on conidial germination, appressoria formation, and infection of Canada thistle by Alternaria cirsinoxia. Conidia germinated and formed appressoria at 98% RH, but required at least 100% RH, and preferably free water, to penetrate leaves. In free water, conidia germinated equally well at 10, 15, 20, 25, or 30°C. Appressoria formation and leaf penetration also occurred at all temperatures evaluated from 10 to 30°C, with the highest values at 20 to 25°C and 20°C, respectively. Conidia required 8 h of continuous leaf wetness to establish visible symptoms of infection on Canada thistle. Exposure of conidia of A. cirsinoxia to up to five intermittent leaf wetness cycles (30 min wet/30 min dry) reduced germination, appressoria formation, and leaf penetration, but conidia remained infective after all cycles. Exposure to cycles of 4 h dew/20 h dry was most detrimental to infection, compared with a 72 h dry period or cycles of 1 h dew/23 h wet or 2 h dew/22 h wet, indicating greater sensitivity of more fully germinated conidia to drying. Such nonspecific temperature requirements and survival during repeated intermittent leaf wetness periods are beneficial characteristics for a bioherbicide. However, high moisture requirements for infection may limit the potential of using A. cirsinoxia to control Canada thistle in the semi-arid prairie provinces of Canada.
First Report of Occurrence of Eggplant Wilt Caused by Verticillium dahliae in Korea
Authors: Kim S. K. , Hong S. S. , Kim K. W. , Park E. W.
Published: May 2007

A wilt disease occurred on greenhouse-grown eggplants (Solanum melongena L.) at Hanam and Yeojoo, Korea, in 1997. Lower leaves on the 2-month-old wilted eggplants exhibited gradual yellowing, interveinal necrosis, and marginal crinkling and dropped prematurely. Vascular tissues of diseased stems were discolored and turned black. Vertical sections of the stems revealed that the pith had been colonized by the fungus. The disease progressed from lower parts of the plants upward. Incidence of diseased eggplants in greenhouses was 5% on 23 May 1997. Although the incidence increased to 10% on 13 June, it remained constant through early July. Fungal isolates from discolored vascular tissues were initially whitish to cream color on potato-dextrose agar, which turned black due to the formation of microsclerotia. The fungus also produced abundant verticillate conidiophores with phialides and conidia. Based on these cultural and morphological characteristics, the fungus was identified as Verticillium dahliae Klebahn. Pathogenicity tests by root cutting, root dipping, or soil drenching resulted in similar symptoms observed in the naturally infected eggplants. Symptoms were first observed on lower leaves of each eggplant 3 weeks after inoculation. Isolation from symptomatic leaves of the inoculated eggplants yielded V. dahliae. This is the first report of occurrence of Verticillium wilt of eggplant in Korea.
First Report of Tomato spotted wilt virus Infection of Tomatillo in Georgia
Authors: Díaz-Pérez J. C. , Pappu H. R.
Published: May 2007

During the 2000 spring season, tomatillo (Physalis ixocarpa) plants showing chlorotic streaks on leaves were observed in an experimental plot of the University of Georgia's Coastal Plain Experiment Station in Tift County, GA. Leaf samples from 192 plants were collected. These included plants that had chlorotic streaks and those without obvious symptoms. Samples were tested by ELISA using a commercially available Tomato spotted wilt virus (TSWV) detection kit (Agdia Inc., Elkhart, IN). TSWV was found in 10 samples that had chlorotic streaks on leaves, and the remaining plants with no obvious symptoms were negative for TSWV. Infected plants were found in both cultivars, Verde Puebla and Toma Verde. The presence of the virus had no apparent effect on plant size or fruit appearance. TSWV infection of the ELISA-positive samples was further verified by immunocapture reverse transcription-polymerase chain reaction (IC-RT-PCR) (1). The primer pair (5′-ATGTCTAAGGTTAAGCTC-3′ and 5′ TTAAGCAAGTTCTGTGAG-3′) represented the first and last 18 bases of the coding region of the nucleocapsid gene of TSWV, respectively, and produced approximately 800-bp PCR product (1). IC-RT-PCR gave a single DNA band of expected size and no amplification was found in the uninfected control. This is the first report of TSWV on tomatillo in Georgia.

Reference: (1) R. K. Jain et al. Plant Dis. 82:900, 1998.
Postharvest Biological Control of Rhizopus Rot of Nectarine Fruits by Pichia membranefaciens
Authors: Qing Fan , Shiping Tian
Published: May 2007

A new yeast antagonist, Pichia membranefaciens, isolated from wounds of peach fruit, was evaluated for its biocontrol capability against Rhizopus stolonifer on nectarine fruits at different temperatures and with other treatments. P. membranefaciens at 5 × 108 CFU/ml of washed-cell suspension completely inhibited Rhizopus rot in nectarine wounds artificially inoculated with 5 × 104 spores per ml at 25, 15, and 3°C. A culture filtrate of the yeast antagonist failed to provide any protection against Rhizopus rot in nectarine fruits. The yeast mixed with iprodione at 100 μg a.i./ml gave better control of R. stolonifer than either yeast or iprodione alone. A solution of 20 g CaCl2 per liter enhanced the efficacy of P. membranefaciens (107 to 108 CFU/ml) as an aqueous suspension. Rapid colonization of the yeast in wounds was observed during the first 48 h at 25 and 15°C. P. membranefaciens at 5 × 108 CFU/ml was effective when applied 0 to 72 h before the pathogen, while at 1 × 108 CFU/ml, its efficacy was best when applied 24 to 48 h prior to inoculation with R. stolonifer. However, its efficacy was significantly reduced when the yeast was applied simultaneously with the pathogen, with disease incidence of 60% and lesion diameter of 37 mm.
Field Evaluation of Phomopsis amaranthicola, A Biological Control Agent of Amaranthus spp.
Authors: Rosskopf E. N. , Charudattan R. , DeValerio J. T. , Stall W. M.
Published: May 2007

There are approximately 60 species in the genus Amaranthus, of which seven are used as grains, leafy vegetables, or ornamentals. The majority of the remaining species are considered important weeds. A new fungal species, Phomopsis amaranthicola, isolated from stem and leaf lesions on an Amaranthus sp. plant, was found to be pathogenic to 22 species of Amaranthus tested. The efficacy of this fungus was tested in field trials using one or two postemergent applications of the fungus consisting of two concentrations of conidia or mycelial suspensions. Species tested for susceptibility in the field included Amaranthus hybridus, A. lividus, A. viridus, A. spinosus, and a triazine-resistant A. hybridus. The cumulative disease incidence data for each treatment within each species were plotted versus time using regression for lifetime data. Plant mortality was recorded 2, 4, and 6 weeks after inoculation. There were significant differences between the treatment effects in the control plots versus the plots treated with P. amaranthicola. The highest level of control was obtained in the first trial when the fungus was applied at 6 × 107 conidia per ml. Final mortality of all species, except A. hybridus, reached 100% in inoculated plots 25 days earlier than in noninoculated control plots. Conidial suspensions were more effective in controlling the species in the second trial than were mycelial suspensions. Spread of the pathogen to noninoculated control plots was faster in the second year than in other years. High levels of plant mortality were achieved in plots of A. spinosus, A. lividus, and A. viridis. A. hybridus and the triazine-resistant A. hybridus were not effectively controlled in the second year due to the advanced stage of plant growth (8 to 10 true leaves) at the time of pathogen application. Results confirmed that P. amaranthicola is an effective biocontrol agent of some of the Amaranthus spp. tested.
Evaluation of Postinfection Control of Citrus Scab and Melanose with Benomyl, Fenbuconazole, and Azoxystrobin
Authors: Bushong P. M. , Timmer L. W.
Published: May 2007

Citrus scab, caused by Elsinoe fawcettii, and melanose, caused by Diaporthe citri, are serious diseases of citrus in Florida that reduce the exterior quality of fruits produced for the fresh market. The availability of fungicides with postinfection activity could increase the flexibility of growers in managing these diseases. The effectiveness of benomyl at 0.96 g a.i./liter, fen-buconazole at 120 mg a.i./liter, and azoxystrobin at 235 mg a.i./liter was evaluated on rough lemon seedlings for scab and on grapefruit for melanose. Potted seedlings in the greenhouse were pruned to stimulate formation of uniform susceptible shoots, which were inoculated and kept moist for 16 h. Fungicides were applied prior to inoculation and at various intervals from 16- to 96-h postinoculation and subsequently evaluated for disease intensity. All three fungicides were effective as preinoculation sprays for scab control. Benomyl was effective if applied up to 72 h after inoculation, and fenbuconazole and azoxystrobin were effective if applied within 16 to 48 h after inoculation. For melanose, azoxystrobin was highly effective as a preventive spray but benomyl and fenbuconazole were not. None of the fungicides was very effective for melanose control as postinfection treatments. Use of postinfection sprays under field conditions appears to be promising for scab control but not for melanose control.
First Report of Stem and Crown Rot of Garbanzo Caused by Sclerotinia minor in the United States and by Sclerotinia sclerotiorum in Arizona
Authors: Matheron M. E. , Porchas M.
Published: May 2007

In March 2000, plants began to die within two garbanzo (Cicer arietinum L.) fields about 48 km apart in southwestern Arizona. Initial symptoms included wilting of leaves and stem necrosis on individual branches, followed by entire plant necrosis and death. White mycelium was present on plant stems near the soil surface. In one field, small black irregularly shaped sclerotia (1 mm in diameter) were present on the infected stem surface along with the white mycelia, whereas in the other field the associated sclerotia were of similar shape but larger (5 to 6 mm in diameter). Isolation from diseased garbanzo stem tissue from the respective fields yielded Sclerotinia minor, which produced small sclerotia when cultured on potato-dextrose agar and S. sclerotiorum, which produced the typical larger sclerotia of this species. To fulfill Koch's postulates, healthy plants and associated soil from a garbanzo field with no evidence of infection by Sclerotinia were removed with a shovel and transferred into a series of 8-liter plastic pots. After transporting back to the laboratory, some of the plants were inoculated by wounding stems with a 5-mm-diameter cork borer, placing an agar disk containing either S. minor or S. sclerotiorum onto each wound, securing the agar disk to the stem with plastic tape, then incubating the plants at 25°C for 7 days. Control plants were treated similarly except that agar disks did not contain Sclerotinia. Stems inoculated with S. minor or S. sclerotiorum developed symptoms of wilt and necrosis, including the appearance of white mycelium and sclerotia on the stem surface, whereas control plants remained healthy. S. minor or S. sclerotiorum were recovered from garbanzo stems inoculated with the respective species of the pathogen. Sclerotinia leaf drop, which can be caused by S. minor or S. sclerotiorum on lettuce in Arizona, had been observed in both fields previously. Garbanzo fields in Arizona usually are watered by furrow irrigation. Disease was most severe in areas of the garbanzo fields that were heavily irrigated with resultant wetting of tops of plant beds. Proper management of irrigation water and avoidance of establishing a garbanzo planting in fields following lettuce could help reduce future losses from these pathogens. S. minor previously had been reported as a pathogen on Cicer arietinum from the island of Sardinia (2); however, this is apparently the first report of the pathogen on garbanzo other than in Sardinia. S. sclerotiorum has been reported as a pathogen on this host in several countries including the United States (California) (1) but not previously in the state of Arizona.

References: (1) I. W. Buddenhagen, F. Workneh, and N. A. Bosque-Perez. Int. Chickpea Newsl. 19:9–10, 1988. (2) F. Marras. Rev. Appl. Mycol. 43:112, 1964.
Whitefly Transmission of Sweetpotato chlorotic stunt virus
Authors: Sim J. , Valverde R. A. , Clark C. A.
Published: May 2007

The genus Crinivirus of the plant virus family Closteroviridae include members that are bipartite and whitefly-transmitted (2). The Crinivirus, Sweetpotato chlorotic stunt virus (SPCSV), was described from sweetpotato (Ipomoea batatas) in Nigeria (1). Vector transmission studies of SPCSV were conducted using two whitefly species, the sweetpotato whitefly (Bemisia tabaci biotype B) and the bandedwinged whitefly (Trialeurodes abutilonea). Whitefly colonies were reared in the laboratory on cotton plants in plexiglass cages. To evaluate transmission efficiency, single whiteflies were used in all experiments. Whiteflies were given 2-day acquisition access periods on I. batatas cv. White Bunch co-infected with SPCSV and Sweetpotato feathery mottle virus (SPFMV). Single whiteflies were then placed on individual healthy I. nil cv. Scarlet O'Hara seedlings for 2-day inoculation access periods. Plants then were sprayed with imidacloprid insecticide and placed in the greenhouse. Four independent tests were performed with each whitefly species. Seven to 10 days after exposing test plants to B. tabaci, 6 of 35, 4 of 28, 5 of 30, and 3 of 25 I. nil plants showed symptoms that consisted of leaf distortion and yellowing. In similar experiments conducted with T. abutilonea, 1 of 33, 0 of 32, 1 of 30, and 2 of 28 I. nil plants showed symptoms. Two weeks after inoculations, reverse transcription- polymerase chain reaction assays were performed with all 22 symptomatic and five randomly selected symptomless plants using primers that amplify the SPCSV heat shock protein 70 (HSP70) homolog gene fragment (446 bp). All 22 symptomatic plants were positive while the five symptomless plants tested were negative. Lower transmission rates were obtained with T. abutilonea (3.2%) when compared with B. tabaci (15.2%). These two whiteflies are present in sweetpotato fields in Louisiana and may play an important role in the spread of SPCSV. This represents the first report of transmission of SPCSV by the bandedwinged whitefly

References: (1) S. Winter et al. Phytopathology 82:869–875, 1992. (2) G. C. Wisler et al. Plant Dis. 82:270–280, 1998.
Pythium spp. Associated with Bell Pepper Production in Florida
Authors: Chellemi D. O. , Mitchell D. J. , Kannwischer-Mitchell M. E. , Rayside P. A. , Rosskopf E. N.
Published: May 2007

Ten species of Pythium and a group of isolates that produced filamentous sporangia but did not form sexual structures (Pythium ‘group F’) were recovered from the root systems of fresh market bell pepper plants grown on polyethylene-mulched production systems in Florida. Pathogenicity tests using pasteurized field soil inoculated with infested wheat seed demonstrated that P. aphanidermatum, P. myriotylum, P. helicoides, and P. splendens can cause significant root rot and reductions in root growth of pepper. P. aphanidermatum and P. myriotylum caused the most severe root rot, the greatest reductions in plant weight, and 42 and 62% plant mortality, respectively. In pathogenicity tests with tomato plants, these four species produced similar plant weight losses and disease ratings to those observed in pepper, but little or no plant mortality. Low incidences of root tip necrosis in pepper plants were observed with P. arrhenomanes, P. catenulatum, P. graminicola, and P. irregulare, but none of these species caused losses in root weight and only P. irregulare reduced shoot weight. P. periplocum, P. spinosum, and Pythium sp. F colonized root tissue of pepper but caused no significant root rot and did not adversely affect growth. Similar trends were observed with tomato, except that P. arrhenomanes caused limited root tip necrosis without affecting plant growth and P. catenulatum, P. graminicola, P. irregulare, P. spinosum, and Pythium sp. F colonized at least some of the plants but did not cause root disease. A significant interaction between temperature and P. aphanidermatum or P. myriotylum was observed on pepper transplants. The greatest reductions in growth occurred at 28°C, whereas plant mortality only occurred at 34°C.
First Report of Anthurium Blight Caused by Xanthomonas axonopodis pv. dieffenbachiae in Reunion Island
Authors: Soustrade I. , Gagnevin L. , Roumagnac P. , Gambin O. , Guillaumin D. , Jeuffrault E.
Published: May 2007

Xanthomonas axonopodis pv. dieffenbachiae is the causal agent of Anthurium blight, a severe systemic disease of Anthurium. Bacterial blight has been reported in most of the areas where Anthurium is cultivated, especially in Hawaii, California, Guadeloupe, Martinique, Jamaica, and Venezuela. This pathogen is also described on many genera of the Araceae family, e.g., Dieffenbachia, Syngonium, Philodendron, Caladium, Aglaonema, and Colocasia. In Reunion Island, Anthurium blight was first observed in 1997 during routine inspections in two nurseries on Anthurium andreanum plants imported from the Netherlands. Lesions consisted of water-soaked spots at the leaf margins surrounded by chlorotic or necrotic zones. Several necrotic lesions had coalesced to form large, dark patches that covered a large portion of the leaf. Some plants showed symptoms of systemic decay. The disease rapidly spread to other Anthurium plants in the nurseries, causing severe damage. Bacteria, which were consistently isolated from infected plants, were gram negative, yellow-pigmented, and mucoid. Carbon source utilization patterns (Biolog, Hayward, CA) were consistent with Xanthomonas sp. and the bacteria responded positively to monoclonal antibodies raised against X. axonopodis pv. dieffenbachiae (Agdia) in an enzyme-linked immunosorbent assay. Between 1997 and 1999, 114 isolates were collected from three main locations: the two primary infected nurseries and another one found contaminated later. Pathogenicity tests were performed on 8-month-old plants of A. andreanum cv. Carré by infiltrating the leaves with a suspension of bacteria (105 CFU/ml) using a syringe. Each strain was inoculated onto three young leaves (four inoculation points per leaf) on two plants. Control plants received sterile Tris solution. Plants were maintained in a growth chamber at 28°C (±1°C) with 95% (±5%) relative humidity and a photoperiod of 12 h. All 114 strains caused typical symptoms on Anthurium with the development of water-soaked spots near the inoculation point after 9 days, evolving into chlorotic and then necrotic areas after 20 to 24 days. No symptoms developed on control plants. Koch's postulates were completed by reisolating, from all the inoculated plants, bacteria that were again serologically identified as X. axonopodis pv. dieffenbachiae. Since 1997, control measures were adopted, consisting of the destruction of the infected plants and quarantining the contaminated nurseries, as well as surveillance intensification at the ports of entry to prevent new introductions.
Genotypic Diversity of Sphaeropsis sapinea from South Africa and Northern Sumatra
Authors: Smith H. , Wingfield M. J. , de Wet J. , Coutinho T. A.
Published: May 2007

Sphaeropsis sapinea is the most important pathogen of Pinus spp. in South Africa. The fungus, which reproduces only asexually, occurs on exotic Pinus spp. In this study, the diversity of the S. sapinea population in South Africa was compared with a population from Northern Sumatra. The populations for both countries were obtained from exotic Pinus patula plantations. The phenotypic diversity of these populations was assessed using vegetative compatibility tests. The percent maximum genotypic diversity, based on Stoddart and Taylor's index, for the South African population was 30.5% compared with 1.5% for the Northern Sumatran population. Based on the number of phenotypes, the South African S. sapinea population was significantly more diverse (P = 0.05) than that of the Northern Sumatran population. The results indicate that the population of S. sapinea in South Africa has, in all likelihood, arisen as a result of introductions of the fungus on pine seeds imported from various parts of the world during the last century.
Phytophthora Brown Rot of Citrus: Temperature and Moisture Effects on Infection, Sporangium Production, and Dispersal
Authors: Timmer L. W. , Zitko S. E. , Gottwald T. R. , Graham J. H.
Published: May 2007

Sporadic epidemics of Phytophthora brown rot occur in citrus orchards in Florida and are caused primarily by Phytophthora palmivora and secondarily by P. nicotianae. With P. palmivora, fruit wetness durations of 3 h or more resulted in maximum infection at favorable temperatures. The optimum temperature range for fruit infection and brown rot development was 27 to 30°C. No brown rot developed at 22°C or less. The optimum temperature for sporulation in culture and on the fruit surface was 24°C, with sporangium production decreasing rapidly at higher or lower temperatures. A few sporangia were produced with 18 h of fruit wetness, and numbers increased as duration of wetness increased up to 72 h. Propagules were splash-dispersed by single droplets of water from infested peel disks horizontally about 350 to 450 mm and vertically about 30 to 45 mm with most isolates. Sporangia were not dispersed by air currents alone. Few sporangia of P. nicotianae were produced on fruit surfaces, and they were not readily dispersed by falling water droplets. Brown rot caused by P. palmivora can become epidemic in Florida from July to October during the rainy season because of its high temperature optimum and prolific sporulation on the fruit surface.
First Report of Colletotrichum dematium on Tomato in Argentina
Authors: Dal Bello G. M.
Published: May 2007

Anthracnose of tomato (Lycopersicon esculentum Mill. var. pyriforme (Dunal) L.H. Bailey) was observed on ripe fruits of pear-shaped tomato in the postharvest phase during September 1998 to February 1999. Anthracnose causes a rot of ripe fruit that can cause significant losses in the field and during storage. Symptoms occurred on fruits of several cultivars grown in commercial fields at La Plata, Buenos Aires Province, Argentina. Fruit rot began as small, round (1 to 2 mm diameter), grayish, sunken, watersoaked lesions. The center of the spots became tan and flecked with small black specks. Individual spots enlarged concentrically to approximately 2 cm in diameter and became covered with numerous, submerged, black acervuli that formed in concentric rings and, under wet conditions, produced a mass of slimy salmon-colored spores. In time, total fruit rot often occurred due to coalescence of multiple lesions. Symptoms developed during storage, resulting in diminished fruit quality and marketable value. Colletotrichum dematium (Pers.) Grove was isolated consistently by plating surface-disinfected lesion margins on acidified potato dextrose agar (PDA). Colonies on PDA were gray, olivaceous to black, with abundant acervuli. Conidia were one-celled, hyaline, and falcate, with acute apices measuring 17 to 28 × 2 to 4 μm, consistent with the description of C. dematium (1). Acervuli were superficial, black, and setose. A fungal isolate was selected to complete Koch's postulates. Surface-disinfected ripe fruits of tomato cvs. Perita and Larga Vida were punctured with a sterile needle containing conidia from sporulating cultures. Inoculated fruits were incubated at 25°C for 48 h in a moist chamber. After 3 to 5 days, soft, watery spots developed at the inoculation point on the fruit, and C. dematium was reisolated from the lesions. Fruits that were punctured but not inoculated did not develop symptoms or yield C. dematium. To confirm pathogenicity on leaves, disease-free tomato plants were sprayed with a conidial suspension (2 × 105 spores per ml) of the pathogen. Control plants were sprayed with sterile water. Inoculated plants and controls were left bagged for 48 h and placed in a greenhouse at 20 to 25°C. After 1 week, necrotic leaf spots developed on inoculated plants. Leaf spots were small, circular, and brown. Yellow rings often surrounded the spots. C. dematium was reisolated from lesions on these leaves. This is the first report of C. dematium on tomato in Argentina.

Reference: (1) B. C. Sutton. 1980. The Coelomycetes: Fungi Imperfecti with Pycnidia, Acervuli and Stromata. Commonwealth Mycological Institute, Kew, England.