bluuebunny/crossref_metadata_2025 huggingface dataset:
First Occurrence of Downy Mildew of Statice, Caused by Peronospora statices, in California and the Rest of the United States
Authors: Koike S. T. , Nolan P. A. , Tjosvold S. A. , Robb K. L.
Published: May 2007

In California, hybrid statice (Misty series; Limonium bellidifolium × Limonium latifolium) is grown as a commercial cutflower crop in fields and greenhouses. In 1997, downy mildew was observed on statice plantings in both southern (San Diego County) and central (Monterey and Santa Cruz counties) parts of coastal California. Initial symptoms consisted of light green, irregularly shaped leaf spots that, after a few days, became chlorotic. As disease progressed, chlorotic spots coalesced and turned necrotic, at times resulting in extensive death of leaf tissues. Under favorable conditions, the purple to gray sporulation of the pathogen could be seen on abaxial surfaces of leaves. Conidiophores had main trunks with dichotomous branches and measured 194 to 335 μm in length (mean = 229 μm) from the base to the first branches and 7 to 8 μm across at the widest part. Branch ends were slender with curved tips that measured 5 to 8 μm long. Conidia were ovoid to globose with very short pedicels, and measured 14 to 19 μm × 14 to 17 μm. Conidial surfaces appeared slightly roughened when viewed with a scanning electron microscope. Clearing leaf sections with 10% NaOH (1) revealed the presence of yellow-brown, globose oospores that measured 31 to 47 μm. The pathogen was identified as Peronospora statices (1). Pathogenicity was demonstrated by pressing leaves with abundant sporulation against healthy leaves of test plants (Misty White) and then placing inoculated plants in a humidity chamber. After 10 to 12 days, symptoms similar to those originally observed developed on inoculated plants; after 14 to 16 days, purple fungal growth morphologically similar to the original isolates grew on leaves. Uninoculated control plants did not develop symptoms or signs of downy mildew. This is the first report of downy mildew caused by P. statices on statice in California and the rest of the United States. The disease has also been confirmed on Blue Fantasia (L. bellidifolium × L. perezii). This disease has been reported previously in Italy, The Netherlands, and the United Kingdom (1).

Reference: (1) G. S. Hall et al. Eur. J. Plant Pathol. 103:471, 1997.
Internal Movement of Erwinia amylovora Through Symptomless Apple Scion Tissues into the Rootstock
Authors: Momol M. T. , Norelli J. L. , Piccioni D. E. , Momol E. A. , Gustafson H. L. , Cummins J. N. , Aldwinckle H. S.
Published: May 2007

Shoot tips of potted Empire and Golden Delicious trees on the susceptible dwarfing rootstock M.26 in the greenhouse were injected with inoculum containing 5 × 109 CFU/ml Erwinia amylovora. At intervals after inoculation, trees were sampled at increments between the shoot tip and the roots by excising stem segments. Segments were ground in phosphate buffer and assayed for the presence of E. amylovora by plating on semi-selective medium and by a polymerase chain reaction (PCR)-based detection method. Eleven days after inoculation, E. amylovora was detected by PCR in symptomless scion tissue >50 cm below the shoot-tip in Empire and Golden Delicious, and in 2-year-old tissue in Golden Delicious. By 21 days, E. amylovora was detected in the M.26 rootstock of Empire trees, and by 41 days in the M.26 rootstock of Golden Delicious. In a similar experiment the following year, Empire trees on M.26 rootstock were inoculated with E. amylovora at early (16 May), mid- (11 June), and late (6 July) phenophase of shoots. Three weeks after inoculation, E. amylovora was detected by PCR from M.26 rootstocks of five of six plants inoculated at the late phenophase, compared to zero of six plants inoculated at the early or mid-phenophase. Late-season fire blight infections of the scion may be particularly hazardous for the health of the rootstock.
Root and Foot Rot of Loquat in Taiwan Caused by Phytophthora
Authors: Chern L. L. , Ann P. J. , Young H. R.
Published: May 2007

Loquat trees growing in central Taiwan were inflicted with a disease causing wilting and death of plants due to severe foot and root rot. The vascular tissues of all infected plants turned brown. Typical as well as atypical isolates of Phytophthora parasitica were isolated from the diseased basal stem and root tissues but not from the discolored vascular tissues. Symptoms observed in the field were reproduced when roots and stems of loquat seedlings were inoculated with zoospores of atypical isolates of P. parasitica; whereas only fibrous root rot resulted from inoculation with typical isolates of P. parasitica. Atypical isolates could be differentiated from the typical isolates of P. parasitica by several characteristics, including colony appearance, partial caducous sporangia, size of oospore, growth at 36°C, mycelial soluble protein patterns, and pathogenicity.
Physiologic Specialization of Puccinia recondita f. sp. tritici in Nebraska During 1995 and 1996
Authors: Watkins J. E. , Rutledge S. S. , Baenziger P. S. , Youngquist W.
Published: May 2007

Field samples of Puccinia recondita f. sp. tritici, collected from four wheat-growing regions in Nebraska in 1995 and from three in 1996, were characterized for virulence. Twenty virulence phenotypes were identified in 1995 and 18 in 1996. Virulence phenotypes MBR-10,18 (virulent on Lr genes, 1, 3, 3ka, 10, 11, 18, and 30) and MDR-10,18 (virulent on Lr genes 1, 3, 3ka, 10, 11, 18, 24, and 30) were the most prevalent, with each phenotype comprising 21.6% of the isolates characterized in 1995. Of the 1995 isolates, 24% were virulent on 10 or more host genes. No virulence to Lr16 and Lr17 was detected. In 1996, virulence phenotype MBR-10,18 was the most prevalent and comprised 20.5% of the isolates characterized. Of the 1996 isolates, 33% were virulent on 10 or more host genes. All isolates in both years were virulent on Lr1, Lr3, and Lr10. New virulence phenotypes were detected in 1996 that were not detected in 1995. In 1996, virulence was more frequent on Lr2a, Lr16, and Lr17 and less frequent on Lr3ka, Lr18, Lr24, Lr26, and Lr30. The number of isolates virulent on Lr24 and Lr26 has decreased from 83 and 53%, respectively, in 1992, to 34 and 1%, respectively, in 1996.
Fumigation of Fruit with Short-Chain Organic Acids to Reduce the Potential of Postharvest Decay
Authors: Sholberg P. L.
Published: May 2007

Vapors of acetic (1.9 or 2.5 μl/liter), formic (1.2 μl/liter), and propionic (2.5 μl/liter) acids were tested for postharvest decay control on 8 cherry, 14 pome, and 3 citrus fruit cultivars. Surfacesterilized fruit were inoculated with known fungal pathogens by drying 20-μl drops of spore suspension on marked locations on each fruit, placing at 10°C to equilibrate for approximately 24 h, and fumigating by evaporating the above acids in 12.7-liter airtight fumigation chambers for 30 min. Immediately after fumigation, the fruit were removed, aerated, aseptically injured, and placed at 20°C until decay occurred. All three fumigants controlled Monilinia fructicola, Penicillium expansum, and Rhizopus stolonifer on cherry. Formic acid increased fruit pitting on six of eight cultivars and was the only organic acid to increase blackening of cherry stems when compared to the control. Decay of pome fruit caused by P. expansum was reduced from 98% to 16, 4, or 8% by acetic, formic, and propionic acids, respectively, without injury to the fruit. Decay of citrus fruit by P. digitatum was reduced from 86 to 11% by all three acids, although browning of the fruit peel was observed on grapefruit and oranges fumigated with formic acid.
Four Garlic Viruses Identified by Reverse Transcription-Polymerase Chain Reaction and Their Regional Distribution in Northern Japan
Authors: Takaichi Miyuki , Yamamoto Mika , Nagakubo Takayuki , Oeda Kenji
Published: May 2007

A specific and highly efficient indexing method for four major garlic viruses, GV1 carlavirus, GV2 potyvirus, onion yellow dwarf virus (OYDV), and mite-borne mosaic virus, was developed using the reverse transcription-polymerase chain reaction method (RT-PCR). When specific primers were synthesized to amplify the coat protein genes of these viruses, the amplified PCR bands had the same expected sizes. This indexing method can be performed using an extremely small amount of leaf tissue (50 mg) to obtain reproducible data. Diseased garlic plants collected from five fields in northern Japan were tested using this method. As GV2 was detected in all the fields, and high frequency of disease symptoms was obtained in the case of heavy infection, GV2 may well be a major garlic virus in this region. By contrast, GV1 was detected in only one of the five fields. OYDV and mite-borne mosaic viruses were also detected in various fields and at different frequencies. Judging from the virus indexing data and the disease symptoms, these two viruses appeared to cause severe symptoms in the case of a mixed infection with GV2. The frequency of virus re-infection to virus-free clones was low in isolated fields, and GV2 was the major virus that re-infected virus-free clones.
Assessing the Representativeness of Data on Yield Losses Due to Rice Diseases in Tropical Asia
Authors: Savary Serge , Elazegui F. A. , Teng Paul S.
Published: May 2007

The representativeness of information on yield losses due to rice diseases in tropical Asia was studied. Published studies involving different groups of diseases (viral, bacterial, and fungal) and conducted in different rice production ecosystems were compared to help identify research gaps, the filling of which could improve current disease management in rice and help in developing strategies that fit the management needs of fast-evolving rice production systems in the future. Four criteria of representativeness of yield loss information were used: representativeness over time (the proportion of studies conducted over more than one crop cycle), representativeness over space (the proportion of studies conducted in more than one location), representativeness of scale (the proportion of studies conducted on the scale of plots or fields), and representativeness of injury (the standard deviation of the proportion of studies using inoculation, spontaneous infection, or chemical control). A strong imbalance in both the number and the representativeness of studies dealing with fungal, viral, and bacterial diseases was found. Most of the few studies of yield loss due to viral diseases (mainly rice tungro disease) were conducted on the scale of individual (potted) plants or were based on one-year data sets, often reflecting strong epidemics only. Studies of bacterial diseases were conducted in single locations only, and whether such results can be extrapolated still needs to be addressed. There is an acute need to better document yield losses in rice ecosystems other than the irrigated ecosystem. While studies conducted in the upland, rain-fed lowland, and deep-water rice ecosystems seem to have a high degree of representativeness, this cannot compensate for their small number in view of the great diversity of these environments. Studies of irrigated rice tend to concentrate on one year and one location. This approach may be based on the erroneous view that the irrigated ecosystem is homogeneous, and possible extrapolation of data from these studies needs to be examined.
First Report of Botryotinia fuckeliana on Kerguelen Cabbage on the Sub-Antarctic Marion Island
Authors: Kloppers F. J. , Smith V. R.
Published: May 2007

Pringlea antiscorbutica R. Br. (the Kerguelen cabbage) is a monotypic species endemic to five sub-Antarctic islands. It does not occur elsewhere and is the only brassica found in the sub-Antarctic region as a whole (1). On Marion Island (46° 54′S, 37° 45′E) the distribution and abundance of the cabbage has declined alarmingly over the past 20 years and the plants increasingly are showing symptoms of microbial pathogen attack. Leaves display brown, water-soaked lesions and sometimes whole plants collapse into a black, slimy residue. Small sections of lesions were sampled, surface sterilized, and placed on water agar and potato dextrose agar (PDA) to which streptomycin (0.1 g/liter) was added. Nonsterilized sections were placed in petri dishes on moist, sterilized, filter paper. Plates were incubated at 15°C in the dark. Botryotinia fuckeliana (de Bary) Whetzel (conidial state; Botrytis cinerea Pers.:Fr) was consistently isolated. Gray to white mycelium grew rapidly on PDA and after 10 days abundant black sclerotia (2 to 16 mm long) were observed on the medium. To confirm pathogenicity, four detached leaves of P. antiscorbutica were each inoculated with a single, 5-mm-diameter PDA plug of B. fuckeliana. Four leaves with noncolonized PDA plugs were used as controls. The leaves were placed with their petioles in sterile water in a transparent incubation chamber. Chamber temperature (minimum 3.9°C, maximum 7.7°C and mean 6.4°C) and light (100 µmol s-1 m-2 photosynthetic photon flux density) approximated field conditions quite closely but relative humidity (annual mean for the island, 81%) was on average 10% higher in the chamber. First symptoms were observed after about 48 h. After 5, 7, and 8 days, brown, water-soaked lesions averaged 14 × 7, 28 × 11, and 36 × 18 mm, respectively. Control leaves showed no symptoms. Reisolations from lesions produced B. fuckeliana. Identity of the pathogen was confirmed by the South African National Collection of Fungi Biosystematics Division, Pretoria. The sub-Antarctic climate is probably conducive to the rapid spread of B. fuckeliana and to its ability to infect P. antiscorbutica. Other factors, such as the recent introduction of the diamondback cabbage moth (Plutella xylostella) to the island and grazing damage by an introduced slug species (Deroceros caruanae) probably exacerbate the threat offered by the fungus to this plant species, one of the last and perhaps the only, remaining relic of an extensive circum-Antarctic flora.

Reference: (1) A. J. Dorne and R. Bligny. Polar Biol. 13:55, 1993.
Marasmiellus Leaf Disease on Maize in West Africa
Authors: Cardwell K. F.
Published: May 2007

A leaf disease of maize previously described as borde blanco (1) or horizontal banded blight (2) was recently observed for the first time in three West African countries. The symptom was white, dry lesions that grew phasically on the edge of the leaf, resulting in horizontal bands delineated by purple to brown margins. Minute basidiocarps (1 mm high) were seen in the white zone of the banded lesions, often arranged linearly. The appearance of the fungus was consistent with a report from Sierra Leone and Guinea Conakry of a basidiomycete on maize of the order Agaricales, Marasmiellus paspalli (Petch) Singer (2). Lamellae were lacking, replaced on mature basidiomes by up to four ridges, which concurred with the description of an unnamed West African variety (1). The pileus and stipe of the mushroom were consistently white when fresh, and light beige when mature. The fungus grew readily on potato dextrose agar, forming a cottony white colony with occasional dark stromatic tissue, and hyphae with abundant clamp connections. Out of over 100 fields visited in 1993 and 1994, the disease was seen in one site only in southern Cameroon in 1994. In 1997, it was found in all maize fields in four separate areas in the southern humid forest zone of that country. In Ghana in November 1996, it was prevalent in a survey of 60 fields, with leaf area losses from 30 to 40%. In August of 1997, the disease appeared in low incidence on maize in Nigeria. The appearance of the Marasmiellus disease in Cameroon, Nigeria, and Ghana in the last 3 years represents a geographic shift from where the pathogen has been previously reported (1,2). It is not known at this time if significant yield loss is being incurred.

References: (1) F. M. Latterell and A. E. Rossi. Plant Dis. 68:728, 1984. (2) M. M. Payak and R. C. Sharma. Curr. Sci. 55:1135, 1986.
First Report of Xylella fastidiosa on Catharanthus roseus in Brazil
Authors: Ueno B. , Funada C. K. , Yorinori M. A. , Leite R. P.
Published: May 2007

In 1998, plants of periwinkle (Catharanthus roseus L.) showing small leaves, short internodes, and dieback symptoms were observed in a garden at the Instituto Agronomico do Parana (IAPAR), Londrina, PR, Brazil. Stems of these plants were cut into short sections and the sap extracted from the tissue by squeezing with pliers. The sap was blotted onto a glass slide and examined for the presence of bacteria by light microscopy (×400). Microscopy observations revealed the presence of a large number of slender, rod-shaped bacterial cells. The bacteria present in the stems of periwinkle were isolated on buffered cysteine-yeast extract (BCYE) and periwinkle wilt (PW) agar media. Stems were disinfected in 70% alcohol and cut into short sections, and the sap extracted as described above. The sap was blotted directly onto the media and the plates were incubated at 28°C. Typical colonies of Xylella fastidiosa were observed 10 days after isolation on both media. Indirect immunofluorescence tests with antibody specific to X. fastidiosa and anti-IgG conjugated with tetrametylrhodamine isothiocyanate (TRITC) were carried out with xylem sap of periwinkle stem and the isolated bacteria. In both cases, immunofluorescence tests were positive for X. fastidiosa. These results confirm that periwinkle plants were infected with X. fastidiosa. This is the first report of the association of X. fastidiosa with periwinkle plants in Brazil. However, the symptoms observed for the X. fastidiosa-infected periwinkle plants differed from those described previously in the U.S. (1): those symptoms consisted of marginal chlorosis and occasional vein clearing of leaves and wilting of the plants.

Reference: (1) R. E. McCoy et al. Plant Dis. Rep. 62:1022, 1978.
Incidence of Ear Rot Pathogens Under Alternating Corn Tillage Practices
Authors: Flett B. C. , McLaren N. W. , Wehner F. C.
Published: May 2007

The efficacy of periodic plowing in reduced-tillage fields in reducing corn ear rot caused by Stenocarpella maydis, Fusarium moniliforme, F. subglutinans, and F. graminearum was determined over three seasons at Bloekomspruit, South Africa. A positive linear relationship was recorded for Stenocarpella ear rot incidence and surface stubble mass. Moldboard plow plots consistently had lower stubble mass and Stenocarpella ear rot incidence than did reduced tillage practices. A cross-moldboard plow applied after one, two, and three seasons of reduced tillage reduced stubble mass and Stenocarpella ear rot incidence in the respective season only. Stenocarpella ear rot incidence increased during the subsequent season in which the original tillage practices were again applied. Alternating tillage practices would therefore not reduce Stenocarpella ear rot in the long term. Reduced disease incidence can only be achieved by moldboard plowing during each season. Alternating tillage practices had no effect on ear rots caused by Fusarium spp. during all seasons.
Detection of Apple Stem Grooving Virus in Dormant Apple Trees with Crude Extracts as Templates for One-Step RT-PCR
Authors: Marinho Vera L. A. , Kummert J. , Rufflard G. , Colinet D. , Lepoivre P.
Published: May 2007

Partial nucleotide sequences of amplification products obtained from four European apple stem grooving virus (ASGV) isolates using degenerate primers showed 80 to 85% similarity with the published ASGV sequence of a Japanese strain but 98 to 100% identities among themselves. Based on these sequences, two ASGV-specific primers (ASGV4F-ASGV4R) were designed to amplify a 574-bp fragment located in the putative viral RNA polymerase. With these primers, six European and five American ASGV isolates, maintained in herbaceous hosts (Chenopodium quinoa, Nicotiana glutinosa, and N. occidentalis) or in apple trees, were readily detected by reverse transcription-polymerase chain reaction (RT-PCR). Using these specific ASGV primers, dsRNA preparations have been shown to constitute good templates for reliable amplification of ASGV sequences from leaves and bark tissues of apple trees, both in a two-step RT-PCR protocol and in the one-step Titan One-Tube RT-PCR. System. Furthermore, the one-step RT-PCR system allowed a specific amplification of ASGV sequences directly from clarified crude extracts of leaves and bark tissues of apple trees during both active growth and the dormant season.
Characteristics of a Potyvirus of the Bean Yellow Mosaic Virus Subgroup in Sesbania speciosa Germ Plasm
Authors: Gillaspie A. G. , Hopkins M. S. , Pinnow D. L. , Jordan R. L.
Published: May 2007

A plant of Sesbania speciosa with leaf mosaic and distortion symptoms was identified in a germ plasm regeneration plot at Griffin, Georgia. The Sesbania virus produced mild or moderate mosaic symptoms on Glycine max cvs. Bragg and Tracy M, Lupinus albus, Nicotiana benthamiana, Pisum sativum cv. Perfected Wales, Phaseolus vulgaris cvs. Black Turtle, Bountiful, and Pinto, and did not infect N. tabacum. Bean yellow mosaic potyvirus (BYMV) and pea mosaic potyvirus (PMV) do not infect Perfected Wales pea and they produce mosaic, distortion, and necrosis on white lupine. The PMV strain tested produced much more severe symptoms on the three green beans, with top necrosis on Pinto. BYMV produced local latent infection of N. tabacum and BYMV and PMV produced mosaic with distortion on N. benthamiana. The Sesbania virus was seed-transmitted at a low rate in S. speciosa. Indirect-enzyme-linked immunosorbent assay tests with a general potyvirus monoclonal antibody and BYMV and white lupine mosaic virus (WLMV) polyclonal antisera were strongly positive. Tests of the Sesbania virus against a monoclonal antibody panel suggests that it is not BYMV or any of the previously described subgroup members, but is a member of the BYMV subgroup. This is the first report of a seedborne BYMV-like virus of Sesbania spp.
A Global Marker Database for Phytophthora infestans
Authors: Forbes Gregory A. , Goodwin Stephen B. , Drenth André , Oyarzun Pedro , Ordoñez Maria Eugenia , Fry William E.
Published: May 2007

A marker database was compiled for isolates of the potato and tomato late blight pathogen, Phytophthora infestans, originating from 41 locations which include 31 countries plus 10 regions within Mexico. Presently, the database contains information on 1,776 isolates for one or more of the following markers: restriction fragment length polymorphism (RFLP) “fingerprint” consisting of 23 bands; mating type; dilocus allozyme genotype; mitochondrial DNA haplotype; sensitivity to the fungicide metalaxyl; and virulence. In the database, 305 entries have unique RFLP fingerprints and 258 entries have unique multilocus genotypes based on RFLP fingerprint, dilocus allozyme genotype, and mating type. A nomenclature is described for naming multilocus genotypes based on the International Organization for Standardization (ISO) two-letter country code and a unique number. Forty-two previously published multilocus genotypes are represented in the database with references to publications. As a result of compilation of the database, seven new genotypes were identified and named. Cluster analysis of genotypes from clonally propagated populations worldwide generally confirmed a previously published classification of “old” and “new” genotypes. Genotypes from geographically distant countries were frequently clustered, and several old and new genotypes were found in two or more distant countries. The cluster analysis also demonstrated that A2 genotypes from Argentina differed from all others. The database is available via the Internet, and thus can serve as a resource for Phytophthora workers worldwide.
Characterization and Survival of Rhizoctonia solani AG2-2 LP Associated with Large Patch Disease of Zoysia Grass
Authors: Aoyagi T. , Kageyama K. , Hyakumachi M.
Published: May 2007

Prevalence and sites of survival of Rhizoctonia solani AG2-2 LP were studied in zoysia grass for 6 years. AG2-2 LP isolates commonly were recovered over all seasons at sites with a history of large patch disease. In patch margins, AG2-2 LP isolates were recovered from crowns of zoysia grass regardless of whether the disease occurred, but were most frequently isolated from the sheath tissues during disease occurrence. In healthy sites approximately 30 cm from the patch, isolates were obtained before but not during disease occurrence. Once disease occurred, patch symptoms rapidly expanded to the edge of tissue colonized by the pathogen during autumn to early spring. To verify that the pathogen spread to healthy areas, the clonal relationship among isolates was examined using their anastomosis reaction. Isolates recovered from the patch and healthy area outside the patch were of the same clone, but isolates from different patches differed. Cultural characteristics and pathogenicity of the AG2-2 LP isolates were compared with R. solani AG2-2 IIIB and R. solani AG2-2 IV. The AG2-2 LP isolates showed an irregular cluster of mycelia (not sclerotia), an irregular zonation, dark brown main hyphae, and sparse aerial hyphae on potato dextrose agar after 4 weeks of incubation. Optimum temperature for growth was 23°C. Cultural characteristics of AG2-2 subgroups IIIB and IV differed from LP isolates. All isolates of AG2-2 LP caused moderate to high levels of disease on zoysia grass, but were nonpathogenic or caused little disease on bent grass and sugar beet. These results indicate that cultural characteristics and host range of AG2-2 LP are different than those of AG2-2 IIIB and AG2-2 IV.
Bacterial Spot of Tomato and Pepper on Four East Caribbean Islands: Races, Their Abundance, Distribution, Aggressiveness, and Prospects for Control
Authors: O'Garro Leonard W.
Published: May 2007

A total of 5,134 strains of Xanthomonas campestris pv. vesicatoria obtained from diseased pepper and tomato fruits at 22 diverse locations on the East Caribbean islands of Antigua, St. Christopher, St. Lucia, and Grenada were assessed for pathogenicity, taxonomic group phenotypes, and sensitivity to copper, zinc, and streptomycin. Altogether, 15 known races, namely T1, T2, P0T1, P0T2, P1T1, P1T2, P2T1, P2T2, P3T1, P3T2, P4T2, P5T2, P5T3, P6T2, and P6T3, were detected. Races T1, P0T1, P0T2, P1T2, P2T1, and P3T1 were common to all islands except St. Lucia. St. Lucia had races P2T2, P3T2, P4T2, and P6T2 in common with Grenada and two races each from among the four pathotypes in common with Antigua and St. Lucia. Races T1, P1T2, P3T1, and P3T2 were the most abundant strains of the bacterium in Antigua, whereas the two latter pathotypes, as well as races P0T1 and P2T1, were among the most prevalent strains in St. Christopher. In contrast, races P6T2 and P5T2 predominated in St. Lucia, and P6T2, P1T2, and P3T2 were the abundant pathotypes in Grenada. Generally, the largest bacterial spot fruit lesions were associated with the predominant races on each island, and the smallest lesions were generally linked to races capable of overcoming gene Bs2. Only these latter races were similar to group B strains of X. campestris pv. vesicatoria with respect to the presence of β-protein in their cellular protein profiles, ability to hydrolyze starch, and inability to oxidize cis-aconitate. Other race types tested resembled group A strains of the bacterium in their ability to utilize cis-aconitate, inability to hydrolyze starch and pectate, and the presence of the α-protein in profiles of cellular proteins. Copper-resistant strains of X. campestris pv. vesi-catoria constitute 8.7 to 10.6% of the pathogen collections from Antigua and St. Christopher and 44.4 and 66.7% of pathotypes from St. Lucia and Grenada, respectively. Almost all strains were sensitive to zinc. Streptomycin resistance was observed among 62% of the strains in St. Christopher and Grenada and 62.8 to 83.6% of those in Antigua and St. Lucia.
Characterization of Benomyl Resistance in Mycosphaerella fijiensis, Cause of Black Sigatoka of Banana, in Costa Rica
Authors: Romero Ronald A. , Sutton Turner B.
Published: May 2007

Sixty-eight and eighty-six percent of monoascosporic isolates of Mycosphaerella fijiensis from two banana plantations in Costa Rica, in which benomyl was used for ≈10 years to control black Sigatoka, were resistant to benomyl in February and November 1994, respectively. No resistance to benomyl was detected in isolates collected during February 1994 from farms with no history of benomyl use that were located ≈50 km from the nearest banana plantations. Only 1% of isolates was resistant to benomyl in a sample taken during November 1994. In three additional banana farms where benomyl had not been used for 3 to 5 years before sampling, ben-omyl resistance persisted at a high frequency. Benomyl-resistant and -sensitive isolates were distributed equally throughout the range of isolate sensitivity to propiconazole, indicating no relationship between resistance to benomyl and lower sensitivity to propiconazole but double resistance to these two compounds. Five benomyl-resistant and five benomyl-sensitive isolates of M. fijiensis were inoculated to banana plants under greenhouse conditions. Benomyl-resistant isolates were more aggressive than benomyl-sensitive isolates, as determined by measures of disease severity, incubation time, and number of lesions at 40 days after inoculation.
First Report of Botryosphaeria dothidea Basal Canker of Pistachio Trees in South Africa
Authors: Swart W. J. , Blodgett J. T.
Published: May 2007

Pistachio (Pistacia vera) cultivation is a relatively new industry in South Africa with tremendous economic potential. However, disease problems could develop in time. The pathogens of pistachio found in other parts of the world plausibly will spread to South Africa and new pathogens never recorded on this host may develop here. In the summer of 1998, 2-year-old rootstocks of P. atlantica and P. integerrima displaying basal cankers and discolored phloem and xylem were observed in the Prieska district of the Northern Cape province. The objective of this study was to identify the causal agent(s). Cankered stems were split and small samples of discolored wood were aseptically placed on corn-meal agar containing streptomycin and incubated for 5 days. Fungi that grew into the agar were transferred to 1.5% water agar dishes containing pine needles to aid sporulation. Species isolated from stems included Fusarium spp. (44%), Fusicoccum aesculi (anamorph of Botryosphaeria dothidea) (23%), a Cytospora sp. (19%), a Chaetomium sp. (3%), and several nonsporulating mycelial fungi (11%). Inoculum of suspected pathogens (F. aesculi, the Cytospora sp., and two Fusarium spp.) were prepared by culturing fungi in petri dishes on potato dextrose agar overlaid with sterile cheesecloth strips (approximately 15 × 25 mm) until the strips were completely colonized. Greenhouse inoculations involved wounding P. atlantica stems by removing the bark (approximately 3 × 6 mm) approximately 10 cm above the soil, and wrapping the colonized cheesecloth followed by Parafilm around the stems at the wound site. Eight plants per isolate and eight wounded and nonwounded (untreated) control plants were used. Noncolonized cheesecloth was applied to wounded controls but not to nonwounded controls. Treatments were assigned randomly. Eight weeks after inoculation, the surrounding bark was removed from all treated shoots and the cambium was examined for discoloration. The length of each cambial lesion was measured and stem sections were surface disinfested and transferred to 1.5% water agar dishes, and the presence of the inoculated fungi was confirmed. Only F. aesculi was pathogenic to P. atlantica and produced cankers on all stems. The fungus was recovered from all tissues sampled 3 cm beyond the wound sites, 88% of those sampled from the wound sites, and none of the control treatments. Discoloration of the phloem and xylem was similar to that observed in the field. The mean canker length was 41 mm on trees with a mean stem diameter of 7 mm. The appearance of B. dothidea, in addition to B. obtusa (1), on pistachio justifies the need for establishing a disease management program for pistachio in South Africa.

Reference: (1) W. J. Swart and W.-M. Botes. Plant Dis. 79:1036, 1995.
Aggressiveness and Perennation of Isolates of Cochliobolus heterostrophus from North Carolina
Authors: Carson M. L.
Published: May 2007

Selection occurring during the saprophytic or overwintering phase of the life cycle of Cochliobolus heterostrophus, the causal agent of southern leaf blight of maize, may be a factor in the persistence of apparently less aggressive isolates in the pathogen population. The relative aggressiveness and ability to perennate of 22 isolates of C. heterostrophus from North Carolina was measured in series of experiments. Significant differences in aggressiveness and percent perennation (overwintering survival) were observed. There was a weak but often significant negative correlation between the ability of isolates to persist on the soil surface and their aggressiveness. The ability of race O isolates to sporulate on senescent corn leaf discs was positively correlated with their aggressiveness. Selection against increased aggressiveness during overwintering does not appear sufficient by itself to counter selection for increased aggressiveness occurring during the pathogen's pathogenic phase.
Reaction of Selected Soybean Genotypes to Isolates of Fusarium solani f. sp. glycines and Their Culture Filtrates
Authors: Huang Y. H. , Hartman G. L.
Published: May 2007

Four soybean plant introductions, PI 520.733, PI 567.374, PI 567.650B, and PI 567.659, and one soybean cultivar, Great Lakes 3202, were inoculated under greenhouse conditions with four isolates of Fusarium solani f. sp. glycines. Foliar disease severity rating was greatest on PI 567.659, followed by Great Lakes 3202, PI 520.733, PI 567.650B, and PI 567.374. There was no significant interaction between isolates and soybean entries for foliar disease severity ratings. Experiments also were conducted to determine if disease development and root colonization differed among entries. Root infection of the five entries did not differ (P = 0.05). Foliar disease progress curves increased faster for PI 567.659 and Great Lakes 3202 than for PI 567.374. The area under the disease progress curve (AUDPC) value for PI 567.374 was the lowest and differed (P = 0.01) from AUDPC values for Great Lakes 3202 and PI 567.659. There were no differences (P = 0.01) in length of taproot lesions, losses in root dry weight, and vascular stem length discoloration among the entries, and there was no correlation (P = 0.05) between these measurements and foliar AUDPC values. Cut seedling stems immersed in culture filtrate developed interveinal chlorosis on leaves of each entry within 2 days. Disease severity on cut seedlings of PI 567.374 was lower (P = 0.01) than on the other entries. There was a positive correlation (r = 0.94, P = 0.05) between AUDPC values of the five entries inoculated with the fungus and the cut seedling test using culture filtrate.
Shiitake Mycelial Leachate Suppresses Growth of Some Bacterial Species and Symptoms of Bacterial Wilt of Tomato and Lima Bean in vitro
Authors: Pacumbaba R. P. , Beyl Caula A. , Pacumbaba R. O.
Published: May 2007

Mycelial leachate of shiitake mushroom inhibited growth of Pseudomonas syringae pv. glycinea, P. syringae pv. tabaci, Xanthomonas campestris pv. glycines, X. campestris pv. campestris, Erwinia amylovora, Ralstonia solanacearum, Curtobacterium flaccumfaciens pv. flaccumfaciens, Bacillus cereus, Escherichia coli, Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus. The mycelial leachate applied as soil drench prevented symptom expression of bacterial wilt of tomato and lima bean in the laboratory. The results suggested that the shiitake mycelia leachate contained an antibiotic ingredient.
Evaluation of Methyl Iodide as a Soil Fumigant for Root-Knot Nematode Control in Carrot Production
Authors: Hutchinson Chad M. , McGiffen Milton E. , Ohr Howard D. , Sims James J. , Becker J. Ole
Published: May 2007

Methyl iodide performance as a soil fumigant was compared with methyl bromide for Meloidogyne incognita control in carrot production. Both compounds were applied to tarped beds by hot-gas fumigation in growers' fields near Bakersfield, California. Methyl iodide was applied at 112, 168, 224, and 336 kg ha-1 and methyl bromide at 112 and 224 kg ha-1. Other chemical treatments included a non-fumigated control, metam sodium (373 liters ha-1), applied through overhead irrigation, and 1,3-dichloropropene (1,3-D; 112 liters ha-1) commercially shank applied. Soil was either extracted or bioassayed with tomato plants to determine M. incognita populations prior to application of fumigants, 2 weeks after fumigant application, and at carrot harvest. Carrots were rated for marketability based on size and ematode-induced damage. Methyl bromide, methyl iodide, and 1,3 D were effective at reducing M. incognita populations over the season at all rates tested. In both trials, plants in plots fumigated with either methyl bromide or methyl iodide produced at least 161 and 181% more marketable carrots without nematode damage, respectively, than plants in control plots. Methyl iodide was an effective alternative to methyl bromide for nematode control in carrot production.
Virulence of Xanthomonas oryzae pv. oryzae on Rice Lines Containing Single Resistance Genes and Gene Combinations
Authors: Adhikari Tika B. , Basnyat Ram Chandra , Mew T. W.
Published: May 2007

Fifty isolates of Xanthomonas oryzae pv. oryzae were collected from different rice-producing districts of Nepal and evaluated for their virulence on these 11 rice lines having from one to four resistance genes: IRBB4 (Xa4), IRBB5 (xa5), IRBB7 (Xa7), IRBB8 (xa8), IRBB10 (Xa10), IRBB14 (Xa14), and IRBB21 (Xa21), two-gene combination AY4+5 (Xa4 and xa5), three-gene combinations NH21-37-1-1 (Xa4, xa5, and xa13) and NH24-10-1-3 (Xa4, xa5, and Xa21), and four-gene combination NH56-1-44-4 (Xa4, xa5, xa13, and Xa21). The ability of an isolate to cause lesions with different lengths across the lines was interpreted as virulence. Isolates that were consistently associated with high or low virulence were statistically differentiated. Most isolates produced large lesions on near-isogenic lines with single genes and small lesions on lines with different gene combinations. Based on infection responses on the two-, three-, and four-gene combinations, five virulence groups were identified. Isolates in virulence group I were widely distributed. The line × isolate interactions were generally not significant with gene combinations, indicating a low possibility of specificity. A line with a four-gene combination, NH56, showed wider spectrum and higher level of resistance to X. oryzae pv. oryzae than the other lines. The results of this study will facilitate the deployment of effective resistance to X. oryzae pv. oryzae in Nepal.
Isolation of Spiroplasma citri from Flowers and Seeds Collected from Infected Periwinkles
Authors: Chang C. J. , Zheng Bixing
Published: May 2007

Isolations were attempted from flowers, stems, and seeds from six Spiroplasma citri-infected periwinkles and from flowers and stems from two healthy plants. Each flower was separated into four parts: petals, sepals, pistils, and corolla tubes. A total of 140 seeds from infected plants were germinated, with a germination rate of 59%. Two and three months after germination, 25 plants from seeds were sampled for the isolation of S. citri. The average spiroplasma cells g-1 of diseased pistils, sepals, petals, corolla tubes, or stems was 1.87 × 108, 1.9 × 107, 1.89 × 106, 3.7 × 106, or 2.35 × 106, respectively. The number of cells isolated from pistils was significantly higher than that from stems, whereas the numbers from sepals, corolla tubes, and petals were comparable to those from stems. No spiroplasma was isolated from flower parts of two healthy plants, from seeds, or from samples collected from 25 plants grown from seeds. Results indicated that flowers were good sources for the isolation of S. citri and confirmed that there is no seed transmission of the S. citri infection in periwinkles.
Occurrence of the White Rust Pathogen, Albugo tragopogonis, in Seed of Sunflower
Authors: Viljoen A. , van Wyk P. S. , Jooste W. J.
Published: May 2007

White rust of sunflower (Helianthus annuus L.), caused by Albugo tragopogonis (Pers.) S. F. Gray, appeared in South African fields not previously planted to sunflower. Spread to these fields from infested fields was unlikely, as some of the newly affected fields were planted out of season and were more than 300 km away from other sunflower production fields. Several reports of this nature led us to investigate the possibility of seed transmission of the causal organism. Extensive colonization of sunflower heads by A. tragopogonis was observed in field trials and breeding nurseries. Head infections consisted of two distinct lesion types. White rust pustules, typical of those formed on abaxial sides of leaves, were recognized on abaxial sides of involucral bracts. Grayish, localized lesions containing dark-colored oospores of the fungus, similar to those formed on stems and petioles (1), were produced in sub-epidermal tissue and extended 3 to 5 mm deep into receptacles. Colonization of seeds was found in only a few lines. Oospores were produced in the pericarps and testae of seeds. No oospores or hyphae, however, were observed in the embryo. This is the first report of A. tragopogonis being seed-borne. Since the incidence of seed infection is low, spread of disease to infested fields is expected to be insignificant. Of more concern, however, is the possible long-range dissemination of the fungus by means of infected seed into regions or countries where the disease has not been previously reported.

Reference: (1) P. S. Van Wyk et al. Helia 18:83, 1995.
First Report of Lentil Ascochyta Blight Caused by Ascochyta lentis in Italy
Authors: Cappelli C. , Buonaurio R. , Torricelli R.
Published: May 2007

In May 1997, ascochyta blight incited by Ascochyta lentis Vassiljevsky was observed at an incidence of less than 5% in lentil (Lens culinaris Medik.) fields in Umbria (Central Italy). Symptoms appeared on leaves and stems as tan spots surrounded by a dark margin. Small black pycnidia that produced a pink exudate containing hyaline, 1 septate, 14.2 to 15.8 × 3.5 μm conidia under high humidity were visible in the center of the spots. The fungus was consistently isolated on potato dextrose agar from diseased leaves or stems. To satisfy Koch's postulates, a conidial suspension (106 conidia per ml) of the fungus was sprayed on leaves of 20-day-old lentil plants (landrace Castelluccio) that were maintained in a humidity chamber for 96 h after inoculation. Lesions resembling symptoms that occurred in the field were observed on plants 3 weeks after inoculation. Symptoms were not observed on control plants sprayed with water. The fungus reisolated from the diseased plants was identical to the original isolates. Based on morphological characteristics of pycnidia and conidia as well as pathogenicity, the fungus was identified as A. lentis. A deep-freeze blotter method (2) was used to detect A. lentis in lentil seeds of 20 local landraces used by Umbrian farmers and two accessions from Canada and Turkey, as well as in seed collected from infected fields. The fungus was present only in the two lentil accessions with an incidence of about 5%. Although the fungus had been isolated from Italian seed germplasm in 1986 (1), this is the first report of ascochyta blight occurring in lentil crops in Italy. The heavy rainfalls that characterize the first stage of lentil cultivation in Umbria are favorable for disease development while hot and dry conditions that usually occur during flowering and maturation prevent the dissemination of inoculum and the infection of the seeds. For these reasons, some Umbrian areas could be more suitable for production of ascochyta-free lentil seeds.

References: (1) W. J. Kaiser and R. M. Hannan. Phytopathology 76:355, 1986. (2) T. Limonard. Proc. Int. Seed Test. Assoc. 33:343, 1968.
First Report of Colletotrichum gloeosporioides as a Foliar and Die-back Pathogen of Prunus africana in Kenya
Authors: Mwanza E. J. M. , Waithaka S. K. , Mibey R. K. , Kariuki G. , Simons S. A.
Published: May 2007

During tree disease surveys between February 1996 and March 1998 in highland forests of Kenya, leaves of Prunus africana (Hook f.) Kalkman collected from regeneration wildings in natural forests and seedlings raised in nurseries were found to be consistently heavily infected with a leaf spot and shot-hole disease caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz., anamorph of Glomerella cingulata (Stoneman) Spauld. & H. Schrenk. The pathogen was identified by sectioning sub-epidermal acervuli on the leaf and also by plating infected tissue segments on 2% malt extract agar. The cultural and conidial morphologies were characteristic of C. gloeosporioides. The isolate is maintained at Kenya Forestry Research Institute (KEFRI) culture collection (No. 069-63) and identity ascertained by the International Mycological Institute (IMI) (ref. W5794). To confirm pathogenicity, leaves of 3-month-old seedlings of P. africana were sprayed to run-off with a conidial suspension adjusted to 105 conidia per ml or sterile water as a control. Following inoculation, the seedlings were covered with transparent plastic bags for 48 h and kept in a glasshouse at 23 ± 3°C under natural light conditions and relative humidity of 80%. Leafspot symptoms similar to those found on leaves of wildings in natural forests and nursery seedlings were evident on the inoculated leaves within 3 weeks. Five weeks later the necrotic spots on the leaves measured 2 to 6 mm in diameter. The spots were circular or irregular usually surrounded by a zone paler than the healthy tissue. Later the centers of the spots fell, leaving clean shotholes. C. gloeosporioides was consistently reisolated from all inoculated plants. When infection was severe, the pathogen caused premature leaf fall and die-back of the leader shoot. P. africana, formerly known as Pygeum africanum, is a widespread tree species in moist tropical Africa and produces durable timber; extracts from its bark are used for the treatment of prostrate gland disorders. This is the first report of which we are aware of C. gloeosporioides emerging as an important pathogen of P. africana.

Reference: (1) M. H. Tsingalia. Afr. J. Ecol. 27: 207, 1989.
Development of Fungal Brown Spot and Spot Blotch on Cultivated Wild Rice in Minnesota
Authors: Nyvall R. F. , Percich J. A.
Published: May 2007

Symptoms of fungal brown spot of cultivated wild rice (Zizania palustris), caused by Bipolaris oryzae, initially occurred on the flag and lower aerial leaves of wild rice at the boot stage of development; whereas spot blotch symptoms, caused by B. sorokiniana, first occurred at the floating leaf stage of plant development on both the floating leaf and the first aerial leaves. The percentage of B. oryzae isolated from all lesions did not increase significantly until early grain formation. Lesion numbers then increased rapidly until plant maturity, when B. oryzae was isolated from 36.9 and 49.3% of all flag and bottom aerial leaf lesions, respectively. On both the flag and lower aerial leaves, the percentage of lesions yielding B. sorokiniana increased slowly until early grain formation, then increased rapidly until plant maturity, 17.6 and 14.1% respectively. Numerous spots on the floating and first aerial leaves, previously thought to be caused by Bipolaris spp. infections, were caused primarily by Nakataea sigmoidea, Colletotrichum spp., and Phoma spp. The number of conidia of B. oryzae produced per lesion under laboratory conditions was greatest from lesions on lower leaves from early-mid flowering until plant maturity. The number of conidia of B. sorokiniana from lesions on both upper and bottom leaves increased until early-mid flowering, then remained relatively constant until plant maturity except that the number of conidia from lesions on bottom leaves declined.