bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Race of Pyrenophora tritici-repentis from Brazil
Authors: Ali S. , Francl L. J.
Published: May 2007

Pyrenophora tritici-repentis causes tan spot of wheat worldwide. Fungal isolates have been characterized into seven races based on their ability to induce necrosis and chlorosis on appropriate wheat differentials (1,2). Nineteen single-spore isolates of P. tritici-repentis were recovered from diseased wheat leaves collected from Brazil. The isolates were tested for their race structure by individually inoculating a suspension of 3,000 conidia per ml on wheat differential seedlings at the 2-leaf stage in the greenhouse. The isolates were tested three times and consistent results were found. The differential set was comprised of Glenlea, Katepwa, ND495, 6B365, Salamouni, and M-3. Seven of the 19 isolates were grouped into race 1 because they produced necrosis on Glenlea, Katepwa, and ND495; chlorosis on 6B365; and neither symptom on Salamouni and M-3. Twelve of the isolates produced necrosis on Glenlea, Katepwa, ND495, 6B365, and Salamouni, and neither symptom on M-3. Necrotic reactions to these isolates on 6B365 (chlorotic or resistant to currently identified 7 races) and Salamouni (resistant to all 7 races), and the resistant reaction on M-3 (resistant to all 7 races) differentiate them from the other seven races. Therefore, we grouped these isolates under a new race and designated this as race 8. To our knowledge, this is the first report on the occurrence of race 8 in P. tritici-repentis. This discovery holds particular significance to breeders and pathologists interested in producing wheat lines with resistance to tan spot. Additionally, we suggest that M-3 be added to the differential set because this line is resistant to all eight identified races. More isolates from Brazil are under investigation to discover the P. tritici-repentis race structure in the country.

References: (1) S. Ali et al. (Abstr.) Phytopathology 92(suppl):S3, 2002. (2) S. E. Strelkov et al. Can. J. Plant Pathol. 24:29, 2002.
A New Soilborne Disease of Dry, Edible Beans in Western Nebraska
Authors: Harveson R. M.
Published: May 2007

During July 2001, wilting, dry bean plants (Phaseolus vulgaris L.) at the 3- to 4-leaf stage were observed in a field near Ogallala, NE. Affected plants exhibited dark brown lesions on the hypocotyls and lower stems. Isolations from lesions on diseased plants on potato dextrose agar (PDA) yielded several isolates of an unknown fungus containing binucleate hyphal cells and numerous clamp connections. After growth on PDA for 6 weeks, all fungal isolates remained sterile and did not produce identifying spores, chlamydospores, or sclerotia. Two of the recovered field isolates were randomly selected for pathogenicity tests. Great Northern bean plants (cv. Beryl) were grown in a peat moss/perlite mix (3:1) in 10-cm plastic pots and inoculated separately with each of the two isolates at the two-true leaf stage. Two-week-old cultures grown on PDA (two 100 × 15 mm plates) were ground in 400 ml water in a blender for 3 to 4 min. Approximately 50 to 60 ml of the mycelial suspension was drenched around stems in each pot (two plants per pot), and incubated in growth chambers at 20, 30, and 35°C with a 12-h photoperiod. Six replicates were used for each isolate/temperature combination. After 4 weeks at both 30 and 35°C, fungi were consistently reisolated from stem lesions of wilting plants like those from the field-infected specimens. These fungi were also morphologically identical to the original isolations, thus confirming pathogenicity of the isolates and completing Koch's postulates. No disease was observed at 20°C. The pathogenicity evaluations were repeated twice with similar results. A group of fungi initially called sterile, white, basidiomycetes (SWBs) have been reported causing disease in other legumes from subtropical climates, including snap bean (2,4) and pigeon pea (3). Similar fungi isolated from bermudagrass were identified as Marasmius spp. after induction of sporocarps in vitro (1). The Nebraska isolates appear to be similar, if not identical to those from previous reports (1,2,3), but will be referred to as SWBs until a teleomorph has been identified. To my knowledge, this is the first report of these pathogens on dry, edible beans and on a legume crop from a temperate climate.

References: (1) R. E. Baird et al. Plant Dis. 76:244, 1992. (2) C. M. Howard et al. Phytopathology 67:430, 1976. (3) W. J. Kaiser et al. Plant Dis. 71:1006, 1987. (4) D. R. Sumner et al. Plant Dis. Rep. 63:981, 1979.
A Rapid Method Using PCR-Based SCAR Markers for the Detection and Identification of Phoma sclerotioides: The Cause of Brown Root Rot Disease of Alfalfa
Authors: Larsen R. C. , Hollingsworth C. R. , Vandemark G. J. , Gritsenko M. A. , Gray F. A.
Published: May 2007

A rapid technique for identification and detection of Phoma sclerotioides, the causal agent of brown root rot of alfalfa, has been developed using polymerase chain reaction (PCR). Amplification products obtained from random amplified polymorphic DNA (RAPD) reactions were cloned and sequenced, and two extended primer sets were designed from the resulting data that were used to detect sequence-characterized DNA markers. A single 499-bp DNA amplification product was consistently obtained from primers PSB12499 that was specific for 19 isolates of P.sclerotioides but was not produced from Phoma medicaginis or Phoma betae, or from other soilborne pathogens including Aphanomyces euteiches, Rhizoctonia solani, Fusarium oxysporum, Pythium ultimum, or Phytophthora infestans. A 499-bp amplification product was also produced from root tissue known to be infected with the fungus as verified by microscopic examination. A similar PCR product was obtained from soil samples collected from fields with an established infection of P. sclerotioides on alfalfa. This PCR-based assay enables detection of P. sclerotioides from alfalfa root tissue and in soil samples in a single day, including extraction of DNA, compared with standard methods that require up to 100 days for identification using agar media.
Survival in Soil of Colletotrichum acutatum and C. gloeosporioides Pathogenic on Strawberry
Authors: Freeman Stanley , Shalev Zvi , Katan Jaacov
Published: May 2007

The survival ability in soil of different inocula of strawberry isolates of Colletotrichum gloeosporioides and C. acutatum was studied under laboratory and field conditions. Two isolates of each species used in this study were identified according to morphological characteristics and by molecular techniques. Conidia of all four isolates survived for up to 1 year in autoclaved soil, whereas viability declined rapidly in untreated soils at 22% soil moisture (field capacity), with a 95% reduction in population recorded within 4.0 to 9.8 days. In methyl bromide (MB)-treated field soil at field capacity, a 95% decline in the viability of conidia of the two species was recorded within 8.9 to 12.9 days. At 11% soil moisture content, the time required for a 95% population reduction of the isolates of C. gloeosporioides and C. acutatum conidia was 124.5 and 114.4, and 72.8 and 74.2 days, respectively. C. acutatum was not recovered from naturally infected crowns after burial for 5 months in MB-fumigated and untreated soils at 10- and 20-cm depths under field conditions, but the decline was slower in the MB-fumigated soil. However, recovery of the pathogen from artificially inoculated mummified fruit after 5 months of burial ranged from 15 to 39%. Soil solarization for 4 weeks and MB fumigation treatments eradicated the pathogen from buried, artificially inoculated fruits. Based on this study, the potential contribution of conidia as well as mummified fruits to disease epidemics should be considered.
A New Pathovar, Pseudomonas syringae pv. alisalensis pv. nov., Proposed for the Causal Agent of Bacterial Blight of Broccoli and Broccoli Raab
Authors: Cintas N. A. , Koike S. T. , Bull C. T.
Published: May 2007

The etiology of three foliar bacterial diseases of crucifers and the relationships between their causal agents were evaluated. Data from LOPAT, carbon utilization tests, and fatty acid analysis indicated that bacterial blights of broccoli and broccoli raab, and leaf spot of broccolini, were caused by strains of Pseudomonas syringae. Data from phage sensitivity, ice nucleation, single carbon source utilization, Polymerase chain reaction using BOXA1R primer (BOX-PCR), and host range analyses were identical for the pathogen causing leaf spot of broccolini and P. syringae pv. maculicola. The broccoli raab and broccoli pathogens infected broccoli raab, all crucifers tested, tomato, and three monocots (California brome, oat, and common timothy). None of the other pathogens tested (P. syringae pv. maculicola, P. syringae pv. tomato, or P. syringae pv. coronafaciens) caused disease on broccoli raab or on both crucifers and monocots. Data from phage sensitivity, ice nucleation, single carbon source utilization, BOX-PCR, and host range analyses were identical for the pathogens from broccoli raab and broccoli, but were different from other pathovars tested, and supported the hypothesis that a new pathovar of P. syringae pv. alisalensis pv. nov. caused a leaf blight on broccoli and broccoli raab.
First Report of the Dagger Nematode Xiphinema rivesi, a Member of the X. americanum Group, from Slovenia
Authors: Urek G. , Širca S. , Kox L. , Karssen G.
Published: May 2007

The dagger nematode, Xiphinema rivesi Dalmasso, is a virus-transmitting plant-parasitic nematode described from France (2) and also reported from Germany, Portugal, and Spain. While this species is only known from a few local sites within Europe, it is widespread in North America and also present in Peru and Pakistan (3). X. rivesi is able to transmit at least four North American nepoviruses, including Cherry rasp leaf virus, Tobacco ringspot virus, Tomato ringspot virus, and Peach rosette mosaic virus (1,4). In early spring 2002, nematodes of the X. americanum group were detected in soil samples taken near the roots of peach plants from an orchard in Bilje near Nova Gorica, Slovenia. Resampling in June and September at the same site and at an adjacent, approximately 30-year-old peach orchard confirmed the presence of the nematode in relatively high numbers (5 per 100 ml of soil). Adult females were isolated and sent for further identification to the Plant Protection Service in Wageningen, the Netherlands. The nematode was morphologically identified as X. rivesi and confirmed at the rDNA-level with internal transcribed spacer restriction fragment length polymorphism analysis. Because both sampling sites where the nematode was found are close to the Vipava River in an area of extensive stone and pome fruit production, it is likely that the nematode is also present in other orchards in this region. The origin of this quarantine nematode is unknown as there is no direct link with Slovenian orchards and import of plant material from abroad in the last decades. To our knowledge, this is the first report of X. rivesi in Slovenia and the fourth report of this species in Europe.

References: (1) D. J. F. Brown et al. Phytopathology 84:646, 1994. (2) A. Dalmasso. Mem. Mus. Hist. Nat. Nouv. Série A., Zool. 61:33, 1969. (3) Data Sheets on Quarantine Pests: Xiphinema americanum sensu lato. Page 629 in: Quarantine Pest for Europe, CABI, Wallingford, UK, 1997. (4) L. W. Stobbs et al. Plant Dis. 80:105, 1996.
Horizontal Spread of Ilarviruses in Young Trees of Several Peach Cultivars
Authors: Uyemoto J. K. , Bulluck L. R. , Pethybridge Sarah , McCorkell Bruce , Asai W. K.
Published: May 2007

Natural spread of Prune dwarf virus (PDV) and Prunus necrotic ring-spot virus (PNRSV) was monitored among healthy trees of six peach (Prunus persica (L.) Batsch) cultivars interplanted into a mature peach orchard between virus-infected trees of the cultivar Carson. Spread of PDV to a few trees of cvs. Andross, Carson, and Halford occurred during bloom just after the dormant test trees were planted in the orchard, as indicated by serological and biological assays during the next season. In contrast, virus infections in cvs. Dr. Davis, Loadel, and Ross were not detected until the fourth to sixth growing seasons. By the seventh season, cumulative transmissions for PDV and PNRSV were 41 and 9, respectively, which included double virus infections in five test trees. Significant differences in cumulative transmission of PDV but not of PNRSV occurred by the fourth season (P = 0.0020). Overall, virus infections among the six cultivars ranged from 70 to 100%.
Validation of Potato Early Blight Disease Forecast Models for Colorado Using Various Sources of Meteorological Data
Authors: Gent David H. , Schwartz Howard F.
Published: May 2007

Disease forecasts from regional or remotely sensed meteorological data free growers from infield weather data monitoring and may improve disease forecast implementation. This study was initiated to validate potato early blight forecast models in Colorado and to determine the influence of sources of meteorological data on forecast accuracy. Hourly temperatures were recorded by Campbell Scientific CR-10, Pessl Instruments μMetos Model MCR300, and Spectrum Technologies Model 450 WatchDog weather stations and data loggers within potato fields, field-specific temperature estimations generated by mPOWER3/EMERGE from off-site weather stations, and regional COAGMET CR-10 weather stations. Mean hourly temperature deviations between mPOWER3/EMERGE or in-field stations and COAGMET varied from 0.93°C greater to 1.11°C less than COAGMET observations. Initial appearance of early blight lesions was predicted using a 300 physiological day threshold in commercial fields in each year from 1998 to 2001 and in experimental plots in each year from 1997 to 2001 as determined by COAGMET meteorological observations. All sources of meteorological data generated early blight forecasts within 6 days of each other across all locations and years. COAGMET weather stations should free potato growers and integrated pest management personnel from collecting in-field microclimatic data and speed the implementation of disease forecasting.
First Report of the Potato Cyst Nematode (Globodera pallida) in the Czech Republic
Authors: Zouhar M. , Rysanek P. , Gaar V.
Published: May 2007

Potato cyst nematode, Globodera pallida, was detected in several soil samples collected from various areas of the Czech Republic. Globodera rostochiensis pathotype Ro1 is known to be widespread in the Czech Republic. G. pallida was reported from the neighboring countries of Austria, Germany, and Poland, and also was suspected to be present in the Czech Republic, but it has never been unambiguously proved (1). Recently, nematode isolates have been recovered that multiply readily on Ro1 resistant potato cultivars. These isolates were identified on the basis of three tests: (i) microscopic observations of cyst vulval area morphology and stylets of second-stage larvae; (ii) enzyme-linked immunosorbent assay using a commercial kit; and (iii) a polymerase chain reaction method (2). A complete series of G. pallida and G. rostochiensis pathotypes from Scotland and Germany served as controls. Results were identical for all three methods used. One sample contained G. pallida only, five samples contained mixtures of G. rostochiensis and G. pallida, and one sample contained G. rostochiensis only. The origin of G. pallida contamination is unknown. Strict quarantine measures have been taken to prevent G. pallida from spreading into neighboring areas. To our knowledge, this is the first evidence of the occurrence of G. pallida in the Czech Republic.

References: (1) J. Potocek et al. EPPO Bull. 21:81, 1991. (2) M. Zouhar et al. Plant Prot. Sci. 36:81, 2000.
First Report of Septoria Blight of Parsley Caused by Septoria petroselini in the Mediterranean Region of Turkey
Authors: Kurt S.
Published: May 2007

During December 2001 to March 2002, Septoria blight of parsley was observed in approximately 500 ha of commercial parsley crops in Arsuz County, Hatay, in the Mediterranean Region of Turkey. Incidence of disease ranged from 42 to 80%. Symptoms included irregularly shaped, grayish brown spots (average 3 to 8 mm diameter) with a slightly darker brown margin of necrotic tissue that developed into tan-to-brown lesions surrounded by chlorotic halo on the leaves. Oval-shaped lesions were observed occasionally on petioles. Lesions contained erumpent, dark brown, flask-shaped pycnidia with the ostiole on the upper surface of the foliage. Thirty samples, consisting of diseased leaves and petioles of parsley, were collected from each field. Infected tissues were surface-sterilized in 1% NaOCl for 2 min, rinsed in sterile distilled water, placed on petri dishes containing potato dextrose agar (PDA), and incubated for 10 to 14 days at 25°C. The fungus formed long, multiseptate (0 to 4), hyaline, filiform conidia (14 to 29 μm × 0.5 to 1.9 μm), and short conidiophores within the pycnidia. Based on the morphological characteristics of the fungus, the pathogen was identified as Septoria petroselini Desm. (1). Monoconidial cultures of 18 isolates were prepared. Pathogenicity was confirmed by brush-inoculating slightly wounded foliage of 5- to 7- week-old parsley plants (cv. Kereviz yapragi) with a conidial suspension (106 conidia per ml of sterile water) of each isolate of S. petroselini. Control plants that were brush-inoculated with distilled water and inoculated plants were placed in clear polyethylene bags that were closed and incubated at 20°C for 48 h. The bags were removed, and plants were maintained in a dew chamber for 21 days at 65 to 70% relative humidity. Foliar symptoms developed 15 days after inoculation and appeared similar to lesions observed in the field. Yellowing and necrosis of leaves was also observed on >60% of inoculated plants. No lesions developed on the control plants. The pathogen was readily reisolated on PDA from inoculated plants. To our knowledge, this is the first report of Septoria blight of parsley in the Mediterranean Region of Turkey.

Reference: (1) R. F. Cerkauskas and J. Uyenaka. Plant Dis. 74:1037, 1990.
Biological and Molecular Characterization of a Novel Tobamovirus with a Unique Host Range
Authors: Adkins Scott , Kamenova Ivanka , Achor Diann , Lewandowski Dennis J.
Published: May 2007

Tobamoviruses are among the best characterized and most studied plant viruses. Three subgroups of tobamoviruses correspond to viral genome sequence and host range to include those viruses infecting (i) solanaceous plants, (ii) brassicas, or (iii) cucurbits or legumes. We isolated a virus from Florida landscape plantings of the malvaceous plant hibiscus (Hibiscus rosasinensis) that appears to be a tobamovirus based upon its virion morphology, genome organization, and coat protein sequence. The experimental host range of this virus included five malvaceous species but excluded all tested brassica, cucurbit, and legume species and 12 of the 19 solanaceous species tested. The unique host range and comparison of coat protein gene and protein sequences with those of recognized tobamoviruses indicate that this is a novel to-bamovirus. A limited survey revealed that this virus is widespread in hibiscus and related species in the Florida landscape.
Subanguina radicicola, the Root-Gall Nematode Infecting Poa annua in New Brunswick, Canada
Authors: Mitkowski N. A. , Jackson N.
Published: May 2007

Poa annua frequently is found as the dominant turfgrass species on golf course putting greens grown in the range of cool-season grasses. While not intentionally established, it is an aggressive weed in stands of bentgrasses (Agrostis spp.). When significant encroachment of P. annua occurs, it often is maintained indefinitely. In May 2003, P. annua putting greens at the Riverside Country Club in Rothesay, New Brunswick, Canada showed signs of an unidentified disease. Putting greens were slow to green up and large chlorotic patches were evident across affected areas. When roots were examined, extensive galling was observed. Galls were slender and often twisted in appearance. Upon dissection of washed galls, hundreds of eggs were exuded into the surrounding water droplet, and mature male and female nematodes were observed. Further morphological examination of males, females, and juvenile nematodes demonstrated that they were Subanguina radicicola (Greef 1872) Paramanov 1967 (1,2). Each P. annua plant had an average of four galls (with a range of two to nine) primarily located within the uppermost centimeter of the soil. Of 18 P. annua putting greens, four were affected by the nematode and displayed the same damage symptoms. S. radicicola has been identified from American beachgrass in Rhode Island and from P. annua in Oregon, but to our knowledge, this is the first report of the nematode affecting P. annua on a golf course in eastern North America.

References: (1) W. F. Mai and P. Mullin. Plant-Parasitic Nematodes: A Pictorial Key to Genera. Cornell University Press, Ithaca, New York, 1996. (2) G. Thorne. Principles of Nematology. McGraw-Hill Book Company, Inc., New York, 1961
First Report of Peronospora arborescens as the Causal Agent of Downy Mildew on Papaver nudicaule in Italy
Authors: Garibaldi A. , Minuto A. , Bertetti D. , Gullino M. L.
Published: May 2007

Iceland poppy (Papaver nudicaule L.) is increasingly grown on the Italian Riviera for export as a cut flower. During the spring of 2003, leaves with irregular, brown, angular spots were collected from a commercial crop grown outdoors near Ventimiglia (northern Italy) with temperatures ranging from 3 to 14°C. Leaves of infected plants appeared curled and blistered; the infected portions of the leaves turned chlorotic. On both surfaces of infected leaves, a characteristic gray, furry growth was evident, particularly at the center of the necrotic areas. Infected leaves eventually died without dropping. Basal leaves with poor air circulation were the most severely affected by the disease. Microscopic observations revealed conidiophores branching dichotomically at least five times. Conidiophores ended with sterigmata bearing single conidia. Conidia measured 19 to 24 × 16 to 18 μm and were elliptical to near spherical and hyaline. Oospores were not present. The pathogen was identified as Peronospora arborescens based on the morphological characteristics (2). Pathogenicity was confirmed by inoculating 60-day-old healthy P. nudicaule plants with a conidial suspension (1 × 105 conidia per ml). Five plants were used as replicates. Inoculated and noninoculated plants were maintained in a growth chamber at 15°C and 90 to 95% relative humidity. After 7 to 10 days, typical symptoms of downy mildew developed oninoculated plants. Peronospora arborescens was observed on infected leaves. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of Peronospora arborescens on P. nudicaule in Italy. Peronospora arborescens was previously reported on P. nudicaule and on many other species of Papaver (P. somniferum, P. dubium, P. caucasicum, P. rhoeas, P. setigerum, and P. argemone) in everal countries (1,2).

References: (1) P. J. Cotteril and I. G. Pascoe. Australas. Plant Pathol. 27:263, 1998. (2) S. M. Francis. No. 686 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, U.K., 1981.
Tomato yellow leaf curl virus Can Be Acquired and Transmitted by Bemisia tabaci (Gennadius) from Tomato Fruit
Authors: Delatte H. , Dalmon A. , Rist D. , Soustrade I. , Wuster G. , Lett J. M. , Goldbach R. W. , Peterschmitt M. , Reynaud B.
Published: May 2007

The whitefly Bemisia tabaci is an insect pest causing worldwide economic losses, especially as a vector of geminiviruses such as Tomato yellow leaf curl virus (TYLCV). Currently, imported and exported tomato fruit are not monitored for TYLCV infection because they are not considered to represent a potential risk as a virus source for whiteflies. A survey of tomato fruit imported into Réunion Island indicated that more than 50% of the fruit contained TYLCV as determined by DNA blot analysis. Moreover, we showed that TYLCV was present at a high titer in tomato fruit, and demonstrated that it can be acquired by whiteflies and subsequently transmitted to healthy tomato plants. Potential risk of the spread of TYLCV by tomato fruit in natural conditions needs to be further assessed.
First Report of Tomato yellow leaf curl virus in Tomato in Guadeloupe
Authors: Urbino C. , Tassius K.
Published: May 2007

In September 2001, symptoms of stunting and chlorotic curled leaves of reduced size were observed on tomato plants in Guadeloupe. These symptoms were different from those described for Potato yellow mosaic virus, which has been present since 1993, but similar to those described for Tomato yellow leaf curl virus (TYLCV). Samples from symptomatic plants were collected and analyzed by polymerase chain reaction (PCR). Primers PC1 (5′-TGACTATGTCGAAGCGACCAGG-3′) and PC2 (5′-CGACATTACAGCCTCAGACTGG-3′) were designed to amplify a 950-bp fragment within the coat protein gene (CP) of TYLCV-IL species (2). Primer pair MP16/MP82 (3) amplified a 550-bp fragment from the conserved nonanucleotide sequence (TAATATTAC) to the 5′ end of the CP gene. Products of expected sizes were obtained with both pairs of primers from all symptomatic samples but not from uninfected samples. A 950-bp and a 550-bp PCR product were cloned into a pGEM-T Easy Vector (Promega, Madison, WI) and sequenced with plasmid specific primers (SP6 and T7). Sequences were compared with those available in the NCBI database using BlastN. Fifteen of the sequences that gave the highest score with BlastN were aligned with the Guadeloupe sequences using Clustal W. The nucleotide sequence of the 950-bp fragment (GenBank Accession No. AY319645) shared at least 97% sequence identity with that of TYLCV from Israel (EMBL Accession No. X15656), Puerto Rico (GenBank Accession No. AY134494), Cuba (EMBL Accession No. AJ223505), and the Dominican Republic (GenBank Accession No. AF024715). Similar percentages of identity were obtained with the 550-bp sequence (GenBank Accession No. AY319646). These results confirm that a begomovirus belonging to the species TYLCV-Israel is infecting tomato in Guadeloupe. To our knowledge, this is the first report of TYLCV in this region of the Caribbean. Puerto Rico is the closest location from which TYLCV was previously reported (1). In May 2002, typical TYLCV symptoms were observed in all tomato production areas at an incidence of 80 to 100%.

References: (1) J. Bird et al. Plant Dis. 85:1028, 2001. (2) Y. Martinez et al. Rev. Prot. Veg. 18:168, 2003. (3) P. Umaharan et al. Phytopathology 88:1262, 1998.
First Report of Pink Seed of Lentil and Chickpea Caused by Erwinia rhapontici in Canada
Authors: Huang H. C. , Erickson R. S. , Yanke L. J. , Hsieh T. F. , Morrall R. A. A.
Published: May 2007

A new disease of lentil (Lens culinaris Medik.) and chickpea (Cicer arietinum L.) caused by Erwinia rhapontici (Millard) Burkh. was found in seed samples from commercial fields in Saskatchewan, Canada in 2002. Infected seeds had a pink or pinkish-brown discoloration of the seed coat. Isolation from surface-sterilized pink seeds resulted in bacterial cultures that produced a water-soluble pink pigment on potato dextrose agar (PDA). Four isolates from different lentil crops, LRC 8265, LRC 8310, LRC 8309, and LRC 8313 and one isolate from a chickpea crop, LRC 8266, were tested as previously described (2). Results of the tests were identical to those for pink bean isolates of E. rhapontici (2) with the following minor exceptions: all were negative for Voges-Proskauer; LRC 8266 was positive for tagatose; LRC 8266, LRC 8309, and LRC 8313 were negative for lactose; and LRC 8266 and LRC 8309 were positive for 5-keto gluconate. For pathogenicity tests, each isolate was inoculated into 30 pods from 6 lentil plants (cv. Laird), 30 pods from 6 desi chickpea plants (cv. Myles), and 30 pods from 6 kabuli chickpea plants (cv. Sanford) by the method described for pink seed of pea (1) and bean (2). Each pod was inoculated with 0.1 ml (0.2 ml for kabuli chickpeas) of bacterial suspension, approximately 108 CFU/ml, by injection through the mid-rib at the basal end. The same number of uninoculated and water-inoculated pods served as controls. Plants were kept in the greenhouse (20 ± 5°C) for 4 weeks, after which isolations of the pathogen were performed as described above. In duplicate experiments, all the isolates caused pink lesions on pods and seeds of lentil, desi chickpea, and kabuli chickpea. The frequency of infected seeds among the five isolates (four lentil and one chickpea) ranged from 50 to 100% on lentil, 73 to 100% on desi chickpea, and 43 to 100% on kabuli chickpea. E. rhapontici was reisolated from seeds with lesions but not from asymptomatic seeds. The study demonstrates that in addition to pea (1) and common bean (2), E. rhapontici is also the causal agent of pink seed of lentil and chickpea. The observation that lentil isolates can infect chickpea and vice versa suggests that host specificity may be lacking in E. rhapontici. To our knowledge, this is the first record of E. rhapontici on lentil and chickpea.

References: (1) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990. (2) H. C. Huang et al. Plant Dis. 86:921, 2002.
First Report of Hypocotyl and Root Rot Disease Caused by Pythium deliense on Soybean Sprouts in Korea
Authors: Yun S.-C. , Kim J.-W.
Published: May 2007

Soybean (Glycine max Merr.) sprouts have been a traditional Korean food for at least 1,000 years. During the summers of 2000 and 2001, severe hypocotyl and root rot occurred on fully grown soybean sprouts, especially in commercial recirculating mass production systems. Brown rot on water-soaked hypocotyls and roots of soybean sprouts caused a 10 to 20% loss in production yield. To investigate the cause, 180 sections of tissue were surface sterilized for 30 s in 75% ethanol and plated on potato dextrose agar (PDA). A fungus with white, aerial mycelia and cultural characteristics of Pythium sp. was isolated consistently. The fungal isolates were identified as Pythium deliense Meurs based on various mycological characteristics (2) on corn meal agar (CMA) and sucrose-asparagine bentgrass leaf culture medium (1). P. deliense oogonia were spherical, smooth, 19 to 23 μm in diameter, and their stalks bent toward the antheridia. The antheridia were the shape of a straw hat, curved club-shaped, terminal or intercalary, monoclinous, occasionally diclinous, 12 to 15 × 8 to 11 μm, and 1 per oogonium (2). In pathogenicity tests, soybean sprouts and the fungus were cultured simultaneously in containers (30 × 30 × 50 cm [W × L × H]) with a daily 3-h showering period at 25°C. There were 8,000 to 10,000 seeds per container inoculated with four plugs of agar inoculum (2 × 2 cm). Inoculum was prepared from 5-day-old fungal cultures grown on PDA. After 6 days, the inoculated soybean sprouts showed the same symptoms as described above, whereas the noninoculated sprouts remained healthy. The fungal pathogen was reisolated from all the inoculated sprouts. P. deliense has never been reported as a pathogen of soybean sprouts. To our knowledge, this is the first report of hypocotyl and root rot disease caused by Pythium deliense on soybean sprout in Korea.

References: (1) J.-W. Kim and E.-W. Park. Kor. J. Mycology 25:276, 1997. (2) A. J. Van der Plaatis-Niterink. Monograph of the genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcultures, Inst. R. Neth. Acad. Sci. Lett. The Netherlands, 1981.
Occurrence of White Top of Pea Caused by a New Strain of Pseudomonas syringae pv. pisi
Authors: Suzuki A. , Togawa M. , Ohta K. , Takikawa Y.
Published: May 2007

A new bacterial disease has been observed on pea in Shizuoka prefecture, Japan, since 1981. The disease occurs in early autumn when pea plants grow vigorously. The disease is characterized by chlorosis and whitening of apical shoots, including leaflets, stipules, and young pods. Usually, these white top (WT) symptoms are associated with extensive water-soaked lesions on stems and on leaflets at the basal part of the diseased plants. Thirty-four bacterial isolates from WT plants were characterized and identified together with 16 strains of Pseudomonas syringae pv. pisi from common bacterial blight of pea. The bacteria were gram-negative rods, having one to six polar flagella. The results of LOPAT tests were + - - - +, showing that they belong to P. syringe. In stab inoculation on stems, the WT isolates produced WT symptoms with water-soaked spots 14 days after inoculation. The 16 P. syringae pv. pisi strains never induced WT symptoms and, on the contrary, caused the typical bacterial blight. WT isolates were not pathogenic on any other plants tested. Phenotypic properties differentiated WT isolates and P. syringae pv. pisi strains into two groups; one consists of WT isolates and P. syringae pv. pisi group A, the other is P. syringae pv. pisi group B. Two distinct fingerprint profiles were identified by repetitive sequence based-polymerase chain reaction. WT isolates and P. syringae pv. pisi group A belonged to the same fingerprint type in rep-PCR, whereas a distinct fingerprint was shown by strains of the P. syringae pv. pisi group B. We concluded that the WT isolates should be included in P. syringae pv. pisi as a distinct strain in symptom expression.
First Report of Swiss Needle Cast Caused by Phaeocryptopus gaeumannii on Douglas-Fir in Turkey
Authors: Temel F. , Stone J. K. , Johnson G. R.
Published: May 2007

Two 15-year-old Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) test plantations at Artvin, in the eastern Black Sea Coast Region of Turkey, were inspected in July 2003. Trees in both plantations had yellow-to-brown foliage, and most trees retained only the current year's needles, resulting in sparse tree crowns. Numerous minute, black fruit bodies were present along the rows of stomata on the lower surfaces of needles from both plantations. Laboratory examination revealed that the fruiting bodies that emerged through the stomata were those of Phaeocryptopus gaeumannii [Rohde] Petrak, the causal agent of Swiss needle cast (SNC). Although low infection levels are relatively harmless, heavily infected trees lose all but the current year's foliage, with resulting average volume growth reductions of 23 to 52% (2,3). The pathogen occurs throughout the natural range of Douglas-fir in western North America, where it is native, as well as in eastern North America, Europe, Australia, and New Zealand, where both host and fungus have been introduced (1,2). The pathway of introduction of the pathogen to Turkey is unknown. Douglas-fir is the only known host of P. gaeumannii, and the pathogen is not known to be seedborne. Where P. gaeumannii has been introduced outside of western North America, infected nursery stock has been considered the most probable source (1). However, the affected Artvin plantations were established with seedlings produced in Turkey by using seed obtained from various sources. Earlier Douglas-fir plantations in Turkey date from 1953 and were established by using seed originating from France. The possibility that the pathogen could have arrived with untracked Douglas-fir seedlings from outside Turkey imported by arboreta or private nurseries cannot be excluded. Alternatively, scattered Douglas-fir plantations could have served as links between the Artvin infestation and known infested areas in central and eastern Europe, with spread occurring via windborne ascospores, similar to the spread of the pathogen to Denmark from the British Isles (ca. 1930) (1). Presence of severe SNC infections in Douglas-fir test sites at Artvin could hamper efforts to use this species in operational forestry in Turkey. To our knowledge, this is the first report of the occurrence of Swiss needle cast on Douglas-fir in western Asia. Voucher specimens have been deposited in the Oregon State University herbarium (OSC 106394-106403).

References: (1) J. S. Boyce. Phytopathology 30:649, 1940. (2) E. M. Hansen et al. Plant Dis. 84:773, 2000. (3) D. Maguire et al. West. J. Appl. For. 17:86, 2002.
First Report of Stem and Root Rot of Tomato Caused by Phytophthora capsici in South Africa
Authors: Labuschagne N. , Thompson A. H. , Botha W. J.
Published: May 2007

Tomato plants, grown in open hydroponic systems under shadecloth and plastic near Barberton and Pretoria in South Africa and Srelebi Phikwe in Botswana, developed symptoms of wilting with brown-to-black cankers on the lower stems, blackening of the vascular tissues, and root rot. Pathogens isolated from affected tissues were identified as Phytophthora capsici Leonian (1) and Pythium aphanidermatum (Edson) Fitzp. (2).They occurred separately or together. Pythium aphanidermatum has previously been recorded on tomato in South Africa. P. capsici isolates were papillate, caducous, grew at >36°C, had tapered sporangial bases, and a maximum sporangial length of >70 μm. Koch's postulates were confirmed by inoculating 4-week-old tomato seedlings (cv. Floradade) grown at 22 to 30°C in a steam-pasteurized mixture of sawdust compost, pine bark, and vermiculite (3:2:1). Plugs from V8 juice agar cultures of P. capsici were placed on wounds made on the stems of 10 seedlings. Ten wounded uninoculated plants served as controls. Water-soaked lesions were visible on the stems of all inoculated plants after 2 days. Control plants remained healthy. After 4 days, lesions turned dark brown with affected plants wilted or dead. Reisolation yielded P. capsici. The experiment was repeated with similar results. To our knowledge, this is the first report of P. capsici on tomatoes in South Africa.

References: (1) A. H. Thompson et al. S. Afr. J. Bot. 60:257, 1994.(2) W. Dick. Keys to Pythium. University of Reading Press, Reading, U.K., 1990.
Evaluation of Inoculation Techniques for Fusarium Ear Rot and Fumonisin Contamination of Corn
Authors: Clements M. J. , Kleinschmidt C. E. , Maragos C. M. , Pataky J. K. , White D. G.
Published: May 2007

Fumonisins have been associated with potentially serious toxicoses of animals and humans. Prior to initiating a corn (Zea mays) breeding program for resistance to these mycotoxins, an efficient inoculation technique must be developed. Four inoculation techniques were evaluated on 14 commercial corn hybrids in Urbana, IL in 1999 and 2000. The techniques were: injection of inoculum through the ear husk leaves at R2 (blister); silks sprayed with inoculum at R2 and covered with a shoot bag until harvest; silks sprayed with inoculum at R2, covered with a shoot bag, reinoculated 1 week thereafter, and covered with a shoot bag until harvest; and insertion of six Fusarium-colonized toothpicks into the silk channel at R2. Only injection of inoculum through the husk leaves significantly increased the concentration of fumonisin in grain and severity of Fusarium ear rot compared with a control. This technique effectively differentiated hybrids previously identified as resistant or susceptible to Fusarium ear rot. The rank order of hybrids inoculated with this technique did not significantly change in the 2 years of this study. This technique is suitable for efficiently evaluating a large number of corn genotypes for resistance to Fusarium ear rot and fumonisin concentration.
Effects of Broccoli Rotation on Lettuce Drop Caused by Sclerotinia minor and on the Population Density of Sclerotia in Soil
Authors: Hao Jianjun , Subbarao Krishna V. , Koike Steven T.
Published: May 2007

Field experiments were conducted at Spence Road site and at the Hartnell College East Campus site in Salinas, CA, to determine the effects of crop rotation with broccoli or a fallow period on lettuce drop caused by Sclerotinia minor and the density of pathogen sclerotia in the soil. Treatments at the Spence Road site with low inoculum density (<7 sclerotia per 100 cm3 of soil) distributed randomly included: successive crops of lettuce (LLL), lettuce rotated with broccoli (LBL), and lettuce followed by a fallow period (LFL). Treatments at the Hartnell site with high inoculum density (>7 sclerotia per 100 cm3 of soil) distributed uniformly included: continuous lettuce (LLLL), broccoli-lettuce-broccoli-lettuce (BLBL), broccoli-broccoli-lettuce-lettuce (BBLL), and fallow-lettuce-fallow-lettuce (FLFL). At the Spence Road site, continuous lettuce did not increase lettuce drop incidence for at least 2 years, although an increase in soilborne sclerotia was observed annually but was below the threshold at which a correlation between inoculum density and disease incidence is observed. Rotation with broccoli resulted in small reductions in disease incidence only in the first year. The density of sclerotia was lowest in the LFL treatment, and the highest in the LLL. At the Hartnell site, rotation with broccoli significantly reduced both sclerotia and lettuce drop incidence. The number of broccoli crops rather than the sequence of lettuce rotations with broccoli was critical for reducing the numbers of S. minor sclerotia in soil. Fallowing after a lettuce crop resulted in marginal reductions in sclerotia and lettuce drop incidence. Viability of recovered sclerotia was not significantly different between treatments, although differences between seasons were detected. Results suggest that rotations with broccoli can be a practical lettuce drop management strategy.
Relationship of Epiphytic Growth of Mycosphaerella citri to Greasy Spot Development on Citrus and to Disease Control with Fenbuconazole
Authors: Mondal S. N. , Timmer L. W.
Published: May 2007

Greasy spot, caused by Mycosphaerella citri, produces foliar lesions and severe defoliation of citrus trees. Ascospore production and deposition by M. citri, development of epiphytic growth, and symptoms were monitored on grapefruit trees in the field and on rough lemon trap plants for 2 years. Ascospore production and deposition peaked in April to May both years. However, epiphytic mycelium did not develop extensively until the summer rainy season was well underway in July. Some epiphytic growth and symptoms formed on trap plants placed in the grove for 2-week periods throughout the year. In the summer, epiphytic growth was apparent 15 days after the exposure period, and symptoms appeared about 60 days after exposure, but development was much slower in cooler and drier months. One or two fenbuconazole applications before the development of epiphytic mycelium in July completely controlled greasy spot on spring growth leaves for 12 to 18 months. Applications in July or August were less effective. Epiphytic mycelium developed more rapidly on summer growth; therefore, fungicide applications need to be timed more precisely.
First Report of Cucumber mosaic virus in Teucrium fruticans
Authors: Cardin L. , Poupet A. , Onesto J. P.
Published: May 2007

Teucrium fruticans (shrubby germander), family Lamiaceae, is a hardy shrub. Being drought tolerant, it is widespread in the Mediterranean area. Because it is readily propagated through cuttings, it is also planted in hedges. In 1997 and 2000, respectively, yellow chlorotic areas were observed on the foliage of T. fruticans in Saint Jean Cap Ferrat (France) and San Remo (Italy). These symptoms were distinct from those produced by a rust that frequently affects T. fruticans in these areas. Viruses from both locations were identified as Cucumber mosaic virus (CMV) based on the following: (i) symptoms after mechanical inoculation of Nicotiana tabacum cv. Xanthi nc, N. tabacum cv. Samsum, Chenopodium quinoa, C. amaranticolor, Vigna unguiculata cv. Black, and Cucumis sativus cv. Poinsett; (ii) the morphology of particles observed in electron microscopy of uranyl acetate stained leaf dips from tobacco; and (iii) positive result from leaves of diseased T. fruticans and mechanically inoculated host plants cited above based on enzyme-linked immunosorbent assay (ELISA) using CMV antisera. On tobacco cv. Xanthi nc, the French (F) and Italian (I) isolates first induced essentially necrotic rings on the inoculated leaves followed by the same systemic symptoms as described above. The two isolates were cloned from local lesions after two successive inoculations in V. unguiculata cv. Black, multiplied in tobacco, purified with the citrate-chloroform method, and stabilized with formaldehyde (1). The serotype determination was made by double immunodiffusion in agar gel with the CMV-D and CMV-To strains and homologous antisera (1,2). The formation of spurs and antigen-antibody lines indicated that both isolates belonged to the ToRS serotype (1). Thirty plants of T. fruticans cv. Azureum, first tested negative for CMV using ELISA, were mechanically inoculated with the F isolate (25 plants) and the CMV-D strain (five plants) and cultivated in a hydroponic system. Three months later, plants inoculated with the F isolate were positive for CMV using ELISA and displayed clear symptoms with chlorotic spots, which were sometimes ring-shaped. As plants mature, symptoms tend to disappear on young shoots. For the CMV-D strain, three plants of five were ELISA positive, but did not show any typical symptoms. This report demonstrates the infection of T. fruticans by CMV and the symptom induction by some CMV isolates. In September 2002, two CMV isolates were collected from T. fruticans in public gardens in Menton (France) and Genoa (Italy). These new isolates have the same characteristics as those described in this report.

References: (1) J. C. Devergne and L. Cardin. Ann. Phytopathol. 7:225, 1975. (2) M. H. V. van Regenmortel. Adv. Virus Res. 12:207, 1966.
First Report of Fusarium oxysporum on Eruca vesicaria and Diplotaxis spp. in Europe
Authors: Garibaldi A. , Gilardi G. , Gullino M. L.
Published: May 2007

Two types of rocket are available on the market in Italy: (i) Eruca vesicaria (synonym E. sativa) known as ruchetta or cultivated garden rocket; and (ii) several species of Diplotaxis (Diplotaxis erucoides, D. muralis, and D. tenuifolia), which are wild plants now widely cultivated. Rocket is increasingly used in the mediterranean cuisine as salad and or to decorate dishes. In spring 2002, plants of the cultivated (E. vesicaria) and wild (Diplotaxis spp.) rocket showing symptoms of a wilt disease were observed in several commercial plastic greenhouses near Bergamo, in northern Italy. Wilted plants were first observed during the spring and summer of 2001 when temperatures were between 26 and 35°C. In May 2002, symptoms were again observed in the same area, on the same farm as well as other farms. Although the distribution of the disease was generally uniform, symptoms were more severe in the central part of the greenhouses where temperatures were warmest (30 to 60% of plants were affected). Diseased plants were stunted and chlorotic with brown or black streaks in the vascular system. Vascular tissues of affected plants appeared red or brown. Vascular streaks in the chlorotic leaves extended from the crown and were continuous with a red-brown discoloration in the vascular system of the crown and upper taproot. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissues when plated on a Fusarium-selective medium (2). Microconidia measured 8.8 × 3.0 µm. E. vesicaria and Diplotaxis spp. were grown in steam-sterilized soil, and 10 days after emergence they were artificially inoculated by root dipping in a spore suspension (1 × 105 CFU/ml) of three F. oxysporum strains collected from infected plants. Uninoculated plants served as control. Plants (60 per treatment) were grown at 25 to 28°C in growth chambers. Wilt symptoms developed on all plants 20 days after inoculation, and F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on cultivated rocket in Europe and the first on wild rocket (Diplotaxis spp.) in the world. A wilt of E. sativa attributed to F. oxysporum f. sp. erucae was previously reported in India in 1973 (1). Studies are being carried out to determine if the Italian isolates of F. oxysporum belong to the same formae speciales.

References: (1) C. Chatterjee and J. N. Rai. Indian Phytopathol 28:309, 1973. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.