bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of the Occurrence of Wheat dwarf virus in Wheat in China
Authors: Xie J. , Wang X. , Liu Y. , Peng Y. , Zhou G.
Published: May 2007

In May of 2004 and 2005, several diseased wheat (Triticum aestivum L.) plants showing extreme dwarfing, various types of yellowing, and reduced or no heading were found in the breeding fields of the Institute of Crop Science, Shanxi Academy of Agricultural Sciences, Taiyuan, Shanxi Province, China. On the basis of these symptoms, infection with Wheat dwarf virus (WDV) was suspected. Total DNA was extracted from diseased plants with the DNeasy Plant Mini kit (Qiagen, Hilden, Germany). Primers were designed based on the WDV-Enkoping1 genome sequence (NC_003326) (1), including: 245f, 5′-CGACTACGCCTGGCGAACATTTG-3′ (residues 245–267); 806r, 5′-TCTGGCATTGCCTGTTTCGG-3′ (complementary to residues 787–806); 1381f, 5′-CAGTGACATCTTCGCCGGAG-3′ (residues 1381–1400); and, 1886r, 5′-ACTCCGTAAGCCTCGAATCC-3′ (complementary to residues 1867–1886). With primer pairs 245f/806r, 1381f/1886r, 245f/1886r, and 1381f/806r, PCR products of 560, 506, 1642, and 2,275 bp were expected, respectively. After amplification, fragments of the expected sizes were seen on 1% (w/v) agarose gels. The fragments were purified by using a DNA gel extraction kit (TaKaRa, Dalian, China) and cloned into the pGEM-T vector (Promega, Madison, WI). The plasmids were transformed into E. coli strain DH5α and plasmid DNA was isolated from overnight cultures by alkaline lysis. Insert sequences were determined using the dideoxynucleotide chain termination method with an automated sequencer (ABI BigDye 3.1, Applied Biosystems, Foster City, CA). At least three independently isolated clones were analyzed for each PCR product. The compiled 2,750 nt sequence (GenBank Accession No. DQ868525) was 98.1, 98.5, 97.8, and 97.9% identical to WDV-Enkoping1 (NC_003326), WDV-SE (X02869), WDV-B (AM040732), and WDV-F (AM040733), respectively. Therefore, the virus isolate (WDV-TY) was identified as WDV (genus Mastrevirus, family Geminividae). Wheat samples collected from different provinces from 2004-2006 were also infected with WDV as indicated by PCR using the same primer pairs. For Shijiazhuang (Hebei Province), Yangling (Shanaxi Province), Kunming (Yunnan Province), Yuncheng (Shanxi Province), Tianshui (Gansu Province), Gangu (Gansu Province), and Zhenzhou (Henan Province), 13 of 14, 6 of 6, 5 of 5, 4 of 4, 2 of 3, 1 of 2, and 1 of 1 samples were positive, respectively, indicating a broad distribution of WDV in China. To our knowledge, this is the first report of WDV in wheat in China.

Reference: (1) A. Kvarnheden et al. Arch Virol. 147:205, 2002.
First Report of Bacterial Blight of Rutabaga (Brassica napus var. napobrassica) Caused by Pseudomonas syringae pv. alisalensis in California
Authors: Koike S. T. , Kammeijer K. , Bull C. T. , O'Brien Doug
Published: May 2007

In 2005, commercial, organically grown rutabaga (Brassica napus var. napobrassica) in San Benito County, CA showed symptoms of a previously undescribed disease on approximately 30% of the plants. Initial symptoms consisted of small (1 to 2 mm in diameter), angular, water-soaked flecks that often were surrounded by chlorotic haloes. These flecks enlarged and coalesced into large, irregularly shaped, gray brown lesions that could be as long as 10 mm. Lesions were visible from both adaxial and abaxial leaf surfaces and generally retained the chlorotic borders. A blue-green fluorescing pseudomonad was consistently isolated from lesions on King's medium B. Eight isolates were characterized and were levan positive, oxidase negative, and arginine dihydrolase negative. Isolates did not rot potato slices but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Samsun). These data indicated that the bacteria belonged to Lelliot's LOPAT group 1 (2). This was confirmed with data from fatty acid methyl ester analysis (MIS-TSBA version 4.10; MIDI, Inc., Newark, DE) that showed that the isolates were highly similar (similarity = 0.922 or greater) to Pseudomonas syringae. Amplification of repetitive bacterial sequences (rep-PCR) using the BOXA1R primer and the polymerase chain reaction resulted in identical banding patterns for the rutabaga isolates and the P. syringae pv. alisalensis pathotype strain. Pathogenicity was demonstrated by growing inocula of six isolates in nutrient broth shake cultures for 48 h (24°C), adjusting the bacterial suspension to 106 CFU/ml, and misting the resulting suspensions onto rutabaga (cv. American Purple Top). Plants were enclosed in plastic bags for 24 h and then incubated in a greenhouse (24 to 26°C). Control plants were misted with sterile water and treated the same way. After 5 to 7 days, foliar symptoms similar to symptoms seen in the field developed on all inoculated plants, and reisolated bacteria were characterized and found to be P. syringae pv. alisalensis. Control plants remained symptomless. The results of two sets of pathogenicity tests were the same. To our knowledge, this is the first report of commercially grown rutabaga as a host of P. syringae pv. alisalensis and the first report of a B. napus host of this pathogen. This bacterial pathogen has previously been reported on commercial plantings of arugula (Eruca sativa), broccoli (Brassica oleracea var. botrytis), and broccoli raab (Brassica rapa var. rapa) in California and under experimental conditions it causes disease on additional hosts, including members of the Poaceae (1).

References: (1) N. A. Cintas et al. Plant Dis. 86:992, 2002. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.
Development of Gibberella Ear Rot on Processing Sweet Corn Hybrids Over an Extended Period of Harvest
Authors: Nordby J. N. , Pataky J. K. , White D. G.
Published: May 2007

Gibberella ear rot, caused by Gibberella zeae, has increased in prevalence recently on lateseason processing sweet corn grown in North America. Little information is available about the development of Gibberella ear rot on processing sweet corn hybrids over extended periods of harvest. In five trials from 2003 to 2005, 12 processing sweet corn hybrids were inoculated with G. zeae and evaluated for severity of Gibberella ear rot on sequential harvest dates from 19 to 27 days after midsilk. Ear rot severity was assessed using a rating scale based on the percentage of kernels with visible symptoms of G. zeae colonization including kernel rot and mycelial growth. Severity ranged from 1.6 to 47.8% over the five trials. None of the hybrids was highly resistant to Gibberella ear rot, although some appeared to be less susceptible. Gibberella ear rot was less severe on three hybrids (GH 2690, GG 147, and Sprint) and more severe on three hybrids (GG 42, GG 145, and Jubilee). Other hybrids had moderate levels of ear rot or responses that varied among years. The relative response of hybrids did not change substantially during the extended period of harvest; however, the rate at which Gibberella ear rot developed on hybrids differed in 2003 and 2005 as reflected by a significant hybrid by harvest interaction. The interaction was primarily the result of Gibberella ear rot developing more severely on susceptible hybrids than on the less susceptible hybrids. The difference in Gibberella development could be exploited to limit losses due to this disease under certain circumstances. If a sweet corn processor had several fields ready to harvest at the same time, and some fields were planted with hybrids that are more susceptible while other fields were planted with hybrids that are less susceptible, losses due to Gibberella ear rot might be minimized by harvesting the most susceptible hybrids first. Other hybrids that might be best suited for early or late harvest can be identified from Gibberella ear rot ratings 28 days after silk channel inoculation at the midsilk growth stage.
First Report of Exserohilum rostratum Associated with Rice Seed in Venezuela
Authors: Cardona R. , González M. S.
Published: May 2007

Rice (Oryza sativa L.) is an important cereal crop in Venezuela and is planted on approximately 200,000 ha. Fungal diseases caused by the Helminthosporium complex of fungi are considered a major constraint to rice production. In 2005, a blotter method was used to identify fungi associated with rice seed. Seeds (150) of cv. INIA-017 were placed on a plate with moistened filter paper and incubated at 26 ± 2°C with a 12-h light/12-h dark cycle for 5 days until fungal sporulation. Single spores were transferred to 2% water agar (WA). Germinated spores were then transferred to potato dextrose agar (PDA), and resultant colonies were preserved until used. To induce sporulation, 4-mm-diameter discs were cut from 72-h-old cultures, transferred to WA, and incubated at 26 ± 2°C for 48 h (modified technique of Alcorn [1]). Discolored seed yielded isolates of Bipolaris oryzae (Berda de Haan) Shoemaker and Exserohilum rostratum (Drechs.) Leonard and Suggs (2). Pathogenicity tests were performed on 60-day-old rice plants of cv. Blue Bonnet 50. Four plants per pot were used for each isolate. Before inoculation, plants were placed in humidity chambers for 48 h. Spores were harvested from discs into a beaker containing 50 mL of a dilute gelatin solution (Gelatin Difco; 5 g/100 mL of sterile distilled water [SDW]). Spore suspensions were filtered through cheesecloth and adjusted to 7 × 104 spores per ml. The inoculated plants were placed in humidity chambers for 72 h. Control plants were sprayed with SDW. Inoculated plants were removed from humidity chambers and placed on a greenhouse bench. Plants inoculated with B. oryzae were symptomatic 5 days after inoculation; resultant lesions were red-brown with chlorotic borders. Lesions subsequently turned gray with reddish borders and were rhombic in shape. Plants inoculated with E. rotratum were symptomatic 7 days after inoculation with elliptical lesions that were orange-brown along venation. These lesions turned gray with reddish borders. Both fungi were reisolated from symptomatic leaf tissue. To our knowledge, this is the first report of E. rostratum from rice in Venezuela.

References: (1) J. L. Alcorn. Mycotaxon. 17:1, 1983. (2) A. Sivanesam. Mycol. Pap. 158, 1987.
Cucurbit aphid-borne yellows virus Is Prevalent in Field-Grown Cucurbit Crops of Southeastern Spain
Authors: Kassem M. A. , Sempere R. N. , Juárez M. , Aranda M. A. , Truniger V.
Published: May 2007

Despite the importance of field-grown cucurbits in Spain, only limited information is available about the impact of disease on their production. During the 2003 and 2004 growing seasons, systematic surveys were carried out in open field melon (Cucumis melo) and squash (Cucurbita pepo) crops of Murcia Province (Spain). The fields were chosen with no previous information regarding their sanitation status, and samples were taken from plants showing viruslike symptoms. Samples were analyzed using molecular hybridization to detect Beet pseudo-yellows virus (BPYV), Cucurbit aphid-borne yellows virus (CABYV), Cucumber mosaic virus (CMV), Cucumber vein yellowing virus (CVYV), Cucurbit yellow stunting disorder virus (CYSDV), Melon necrotic spot virus (MNSV), Papaya ringspot virus (PRSV), Watermelon mosaic virus (WMV), and Zucchini yellow mosaic virus (ZYMV). We collected 924 samples from 48 field plots. Out of these, almost 90% were infected by at least one of the viruses considered, usually CABYV, which was present in 83 and 66% of the melon and squash samples, respectively. In the case of melon, CYSDV, BPYV, and WMV followed CABYV in relative importance, with frequencies of around 20 to 30%, while in squash, CVYV and BPYY showed frequencies between 28 and 21%. The number of multiple infections was very high, 66 and 56% of the infected samples of melon and squash, respectively, being afflicted. CABYV was present in all multiple infections. The high incidence of CABYV in single and multiple infections suggests that this virus may well become an important threat for cucurbit crops in the region. Restriction fragment length polymorphism (RFLP) analysis revealed that CABYV isolates can be grouped into two genetic types, both of which seemed to be present during the 2003 epidemic episode, but only one of the types was found in 2004.
Integration of Copper-Based and Reduced-Risk Fungicides for Control ofBlumeriella jaapiion Sour Cherry
Authors: McManus Patricia S. , Proffer Tyre J. , Berardi Raffaele , Gruber Barrett R. , Nugent James E. , Ehret Gail R. , Ma Zhonghua , Sundin George W.
Published: May 2007

Practical resistance to sterol demethylation inhibitor (DMI) fungicides among populations of Blumeriella jaapii, the cherry leaf spot (CLS) pathogen, was documented in 2005. In the present study, strategies to reduce selection for DMI-resistant strains of B. jaapii and adapt to possible restrictions on the use of chlorothalonil are described. Ten field trials were conducted on the sour cherry cultivars Balaton and Montmorency to test the efficacy of integrating respiration-inhibitor and copper-based fungicides into spray programs. Programs that included up to three sprays of copper-based fungicides were among the most effective for controlling CLS, although leaf phy-totoxicity was sometimes observed. Under high disease pressure, eliminating chlorothalonil compromised CLS control. ‘Balaton’ and ‘Montmorency’ did not differ in the percentage of leaves with CLS or defoliation resulting from CLS. The physical modes of action of representative DMI, QoI, and copper-based fungicides were evaluated in a leaf disk assay. Trifloxystrobin, a QoI fungicide, provided the best protection against infection by B. jaapii. All fungicides were more effective than water when applied 46 h postinfection, although differences were not statistically significant in one of two trials. Tebuconazole, a DMI, was the only fungicide that was more effective than water in preventing resporulation from existing lesions in both trials. Isolates of B. jaapii, which varied in DMI-sensitivity, all were sensitive to copper in vitro.
First Report of Fusarium Wilt of Flue-Cured Tobacco Caused by Fusarium oxysporum f. sp. batatas in Spain
Authors: Rodríguez-Molina M. C. , Palo E. , Palo C. , Espárrago G. , Verdejo E. , Torres-Vila L. M. , García J. A. , Blanco I.
Published: May 2007

Tobacco (Nicotiana tabaccum L.) is among the most important crops in La Vera Region (Cáceres, west-central Spain) where, since 2001, flue-cured tobacco plants showing typical symptoms of a vascular disease associated to the cyst nematode (Globodera tabacum) complex have been frequently observed (2). Symptoms observed were wilting, yellowing, and drying of the leaves, usually on one side of the plant; stunted and distorted leaves with curved midribs due to the unequal growth; and brown vascular discoloration of stems and midribs. Several diseased plants were collected during the summers of 2003 and 2004, and F. oxysporum was consistently isolated from sections of necrotic midribs. To confirm the pathogenicity of F. oxysporum isolates, plants of flue-cured tobacco (cv. Ct-681) were inoculated. Since Fusarium wilt of tobacco may be caused by F. oxysporum f. sp. vasinfectum or F. oxysporum f. sp. batatas (1), plants of cotton (cv. Acala) and sweet potato (cvs. Nemagold and Nancy Hall) were also inoculated to determine the forma specialis designation. Twenty plants per cultivar and isolate were inoculated with six isolates at the two to four true-leaf stage by pouring into the substrate 200 ml of a conidial suspension (1 × 105 CFU/ml). After inoculation, plants were incubated in a growth chamber at 28°C (day) and 24°C (night) with a 16-h photoperiod. All six F. oxysporum isolates were pathogenic to tobacco and sweet potato, but there were differences among isolates in time from inoculation to appearance of first disease symptoms (7 to 15 days after inoculation in tobacco and sweet potato) and also in disease severity 30 days after inoculation (60 to 100% wilt or mortality in tobacco and 50 to 100% in sweet potato). F. oxysporum was reisolated from stems of inoculated plants. No disease symptom was observed in cotton plants 60 days after inoculation, and F. oxysporum was not reisolated from them. Results of inoculation on the differential hosts indicated that disease symptoms in tobacco were caused by F. oxysporum f. sp. batatas. To our knowledge, this is the first report of F. oxysporum f. sp. batatas causing disease in flue-cured tobacco in Spain.

References: (1) G. M. Armstrong and J. K. Armstrong. Phytopathology 58:1242, 1968. (2) G. Espárrago and I. Blanco. Plant Dis. 86:1402, 2002.
Downy Mildew Caused by Bremia lactucae on Strawflower (Helichrysum bracteatum) in California
Authors: Koike S. T. , Ochoa O. E.
Published: May 2007

In 2006, field-planted strawflower (Helichrysum bracteatum (Venten.) Andr.) grown for cutflowers in coastal San Mateo County was severely infected with a downy mildew disease. Initial symptoms consisted of irregularly shaped chlorotic lesions. Lesions were typically vein delimited, and in particular, did not cross the central longitudinal vein of the lanceolate leaves. Lesions were large and could exceed 6 cm long. Profuse white sporulation developed on the abaxial sides of the lesions. As disease progressed, lesions became gray brown and necrotic. Cutflower stems having symptomatic foliage were unmarketable. Hyaline conidiophores emerged from stomata, branched dichotomously, and had branch tips ending in swollen vesicles bearing sterigmata. Conidia were hyaline and ovoid to globose in shape. The pathogen was identified as Bremia lactucae Regel. To establish pathogenicity, strawflower plants were spray inoculated with a conidial suspension of 1 × 104 conidia/ml, incubated for 24 h in a dew chamber (18 to 20°C), and then maintained in a greenhouse (22 to 24°C). After 14 days, symptoms and signs of downy mildew developed on inoculated plants and the pathogen was confirmed to be B. lactucae. Untreated control plants did not develop downy mildew. Because lettuce (Lactuca sativa L.) is grown extensively in this coastal region, we investigated the pathogenicity of B. lactucae from strawflower on lettuce by inoculating a lettuce downy mildew differential series that includes 20 lettuce lines, four wild L. serriola lines, and strawflower. A conidial suspension of 1 × 106 conidia/ml was applied to all plants; plants were then incubated in a growth chamber with irradiation at 15°C. After 14 days, only the strawflower plants showed downy mildew lesions and sporulation. Collected from diseased field-grown strawflower, 100 downy mildew conidia were measured and had dimensions of 24.4 × 17.4 μm. These conidia were significantly longer than the B. lactuca conidia collected from lettuce (21.8 × 18.1 μm) grown in a nearby area (LSD [P = 0.05] = 2.2), though dimensions were within the reported length range for B. lactucae (12 to 31 μm) (2). To our knowledge, this is the first report of downy mildew caused by B. lactucae on strawflower in California. Inoculation studies indicate that these strawflower and lettuce pathogens from California likely belong to distinct formae speciales (2), though a B. lactucae isolate in Italy was able to infect both hosts (1). The pathogen has been reported on strawflower in Florida, Egypt, Italy, and the United Kingdom (1).

References: (1) A. Garibaldi et al. Plant Dis. 87:315, 2003. (2) W. M. Morgan. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 682. CAB International, Wallingford, UK, 1981.
First Report of Iris yellow spot virus on Onion in New York
Authors: Hoepting C. A. , Schwartz H. F. , Pappu H. R.
Published: May 2007

Iris yellow spot virus (IYSV [family Bunyaviridae, genus Tospovirus]), a potentially devastating disease of onion vectored by onion thrips (Thrips tabaci Lindeman), has been reported from most states in the western United States where significant onion production occurs, with the most recent report from Texas (1). In June 2006, volunteer onion (Allium cepa) plants in Orleans County, New York (Elba muckland) were found to have symptoms indicative of IYSV infection. The scapes (seed stalks) of the volunteer onions found at the edge of a cull pile from a 2005 onion crop exhibited diamond-shaped lesions, each with a distinct green center and a double yellow border. Approximately 25 of 100 plants of red and yellow onion cultivars exhibited characteristic IYSV lesions. The cull pile was composed primarily of locally grown onions, although a few of the bulbs were grown from imported bare-root transplants imported from Arizona. Symptomatic plants tested positive for IYSV using IYSV-specific antiserum from Agdia Inc. (Elkhart, IN) in a double-antibody sandwich-ELISA. The presence of IYSV was verified by reverse transcription (RT)-PCR using primers derived from the small RNA of IYSV (S-RNA). The primers flanked the IYSV nucleocapsid (N) gene (5′-TAA AAC AAA CAT TCA AAC AA-3′ and 5′-CTC TTA AAC ACA TTT AAC AAG CAC-3′ (3). RT-PCR assays produced a PCR amplicon of expected size (approximately 1.2 kb) and the product was cloned and sequenced. Nucleotide sequence analysis confirmed the identity of the amplicon as that of the IYSV S-RNA. Sequence comparisons showed 95 to 98% identity with known IYSV N gene sequences available in GenBank. The virus is poorly transmitted to onion by mechanical inoculation and we did not have access to a noninfested colony of the onion thrips vector to transfer the virus from these samples to noninfected onions. No asymptomatic plants were tested. Among the onion-growing states in the eastern United States, IYSV has previously only been reported from Georgia (2). To our knowledge, this is the first report of IYSV in New York and the greater northeastern United States. The finding of this disease in New York confirms further spread of the virus within North America and the need for research to develop more effective management options to reduce the impact of IYSV on onion crops.

References: (1) M. Miller et al. Plant Dis. 90:1359, 2006. (2) S. W. Mullis et al. Plant Dis. 90:377, 2006. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006.
First Report of Tobacco streak virus Infecting Guizotia abyssinica from India
Authors: Arun Kumar N. , Lakshmi Narasu M. , Zehr U. B. , Ravi K. S.
Published: May 2007

Guizotia abyssinica (L.f.) Cass. (niger), an important oil seed crop grown in India, is used in foods, paints, soaps, and as an illuminant. During a survey conducted in 2004 to monitor Tobacco streak virus (TSV) in Helianthus annuus L. (sunflower) and Arachis hypogaea L. (groundnut), typical symptoms of leaf and petiole necrosis were observed in niger plants from Karnataka State, India. The field-collected samples reacted with TSV-specific polyclonal antiserum in direct antigen coated (DAC)-ELISA. Indicator host species were mechanically inoculated with extracts from symptomatic leaves and grown under greenhouse conditions. The inoculations resulted in local necrotic lesions on Vigna unguiculata cv. C-152 (cowpea), Gomphrena globosa, and Nicotiana tabacum cv. Xanthi (tobacco) at 3 to 4 days postinoculation (dpi) and systemic mosaic mottling on sunflower and G. globosa at 7 to 9 dpi. To identify the virus at the molecular level, total RNA was isolated (RNeasy kit, Qiagen Inc., Chatsworth, CA) from the virus-inoculated cowpea leaf and used for reverse transcription-PCR using TSV CP (coat protein) specific primers (2). The resulting ~720-bp amplicon corresponding to the CP gene of TSV was cloned into pGem-T vector (Promega, Madison, WI) and sequenced. The resulting sequence of the TSV-niger isolate (TSV-NG) comprised 717 nucleotides encoding 238 amino acid residues of the viral coat protein (GenBank Accession No. DQ864458). Comparison of the sequence with those of other TSV CP gene indicated 98.5 to 99.3% nucleotide and 97.9 to 99.6% amino acid sequence identity with TSV isolates from India (1,2; GenBank Accession Nos. AF505073, AY061930, AY061929, AF515823, AF515824, and AF515825). The sequence of TSV-NG had 89.5 and 80.0% amino acid identity with TSV-WC, type strain from the United States (GenBank Accession No. X00435) and TSV-BR, isolate from Brazil (GenBank Accession No. AY354406), respectively. On the basis of symptoms, transmission, and serological and molecular data, the causal agent of necrosis in niger was identified as a strain of TSV widely prevalent in other oil seed and vegetable crops in India. The new report of Tobacco streak virus infecting niger from India, indicated the expansion of host range among oil seed crops.

References: (1) A. I. Bhat et al. Indian J Biotechnol. 1:350, 2002. (2) K. S. Ravi et al. Plant Pathol. 50:800, 2001.
Characterization of Wheat-Triticale Lines Resistant to Powdery Mildew, Stem Rust, Stripe Rust, Wheat Curl Mite, and Limitation on Spread of WSMV
Authors: Li Hongjie , Conner R. L. , Liu Zhiyong , Li Yiwen , Chen Yu , Zhou Yilin , Duan Xiayu , Shen Tianmin , Chen Qin , Graf R. J. , Jia Xu
Published: May 2007

High yield potential and the wide adaptability of wheat-rye T1BL·1RS translocation lines are attractive to breeders. The wheat-rye lines Lankao 1, 3, 4, and 5 were resistant to a wide spectrum of wheat powdery mildew (Blumeria graminis f. sp. tritici) isolates from both China and Canada. They also were resistant to a mixture of wheat stem rust (Puccinia graminis f. sp. tritici) pathotypes (98WSR) and wheat stripe rust (P. striiformis f. sp. tritici) races from western Canada and China. Colonization of wheat curl mite (WCM) (Aceria tosichella) resulted in slower development of rolling and trapping leaves in the Lankao lines than in the WCM-susceptible check cultivars. The delayed development of Wheat streak mosaic (WSM) symptoms on Lankao lines was observed when transmitted by viruliferous WCM, even though they were susceptible to Wheat streak mosaic virus (WSMV). This effect of Lankao lines on limiting the spread of WSM was comparable with other known sources of WCM resistance. Sequential C-banding and genomic in situ hybridization analyses revealed the presence of a pair of T1BL·1RS translocated chromosomes in the Lankao lines. Segregation analysis of the F2 progeny plants derived from crosses between Lankao 4 and the susceptible wheat cvs. Mingxian 169 and Lovrin 13 indicated that a single dominant gene was responsible for the isolate-specific resistance against wheat powdery mildew in Lankao 4. Polymerase chain reaction analysis using an STS marker amplified rye chromatin in powdery mildew-resistant and -susceptible F2 plants of the Mingxian 169 × Lankao 4 cross demonstrated that the resistance of Lankao 4 was not controlled by a gene or genes located on the rye chromosome arm of T1BL·1RS. The resistance of the Lankao lines to diseases and limitation of the spread of WSMV, in combination with good quality and high yield potential, makes them useful for wheat improvement and production.
Erwinia persicina Causing Chlorosis and Necrotic Spots in Leaves and Tendrils of Pisum sativum in Southeastern Spain
Authors: González A. J. , Tello J. C. , Rodicio M. R.
Published: May 2007

In 2003, symptoms of generalized chlorosis as well as necrosis in leaves and tendrils were observed in Pisum sativum L. cv Tirabeque grown in green fields in southeastern Spain (Granada Province), and by 2004, the disease affected approximately 12 ha. Bacteria isolated from symptomatic samples were gram negative, rod shaped, motile, oxidase negative, facultatively anaerobic, and fermentative, which coincided with the general characteristics of the family Enterobacteriaceae. The gene encoding the 16S rRNA from two isolates (LPPA 406 and LPPA 408) was sequenced after PCR amplification (1). The two sequences were identical (EMBL Accession No. AM294946 for LPPA 408) and showed 99% similarity with several strains of Erwinia persicina (including the type strain ATCC 35998, LPPA 373, LMG 11254, GS04, and LMG 2691). Additional biochemical tests were performed using E. persicina ATCC 49742 as a control. The three strains were negative for arginine dihydrolase activity, indol production, hydrolysis of casein, and hydrolysis of gelatin. In contrast, they were positive for assimilation of adonitol, l-lactate, mannitol, m-inositol, erythritol, sorbitol, sucrose, nitrate reduction, hydrolysis of aesculin, and growth in 5% NaCl at 36°C. Nevertheless, E. persicina ATTC 49742, but not the isolates from P. sativum, produced a pink pigment. The latter isolates were also tested for pathogenicity. Bacterial suspensions (108 CFU/ml) were spray inoculated on 10 pea seedlings of cv. Tirabeque. Seedlings were covered with transparent plastic bags for 2 days and held in an incubation chamber at 22°C and 80% relative humidity with a 12-h photoperiod. Assays were conducted twice. Symptoms that developed were similar to those originally observed in the field, whereas symptoms did not occur on control seedlings sprayed with sterile distilled water. Bacteria sharing the characteristics of the inoculated isolates were recovered from symptomatic plants, hence fulfilling Koch's postulates. E. persicina has been isolated previously from bean in the United States (3) and southeastern Spain (1) and from tomato, banana, and cucumber in Japan (2). To our knowledge, this is the first report of the bacterium on P. sativum.

References: (1) A. J. González et al. Plant Dis. 89:109, 2005. (2) M. V. Hao et al. Int. J. Syst. Bacteriol. 40:379, 1990. (3) M. L. Schuster et al. Fitopatol. Bras. 6:345, 1990.
First Report of Apple chlorotic leaf spot virus in Quince in Greece
Authors: Mathioudakis M. M. , Candresse T. , Katis N. I.
Published: May 2007

The sanitary status of pome fruit trees was evaluated in central and northern Greece during a survey in the autumn of 2004 and spring of 2005. Twenty-six leaf samples were collected from five symptomless and 21 symptomatic quince trees showing fruit deformation (FD) symptoms and diffuse chlorotic leaf spots. All samples were tested for the presence of Apple chlorotic leaf spot virus (ACLSV), a member of the Trichovirus genus, initially by ELISA and then by a specific reverse transcription (RT)-PCR assay reported previously (1). ACLSV has a broad host range that includes most, if not all, Prunoidae (peach, apricot, plum, and cherry) and Maloidae (apple, pear, and quince) fruit tree species. Although it has been tentatively linked with fruit, leaf, bark, and growth retardation symptoms in quince (2,3), its geographic distribution and association with specific symptoms is still poorly determined. ACLSV was initially detected by serology in two plants, one symptomless and one showing FD symptoms. ACLSV presence in these two samples and in an additional symptomless plant was confirmed by the ACLSV-specific RT-PCR assay. Sequencing of the RT-PCR amplicon from the symptomatic isolate (EMBL Accession No. AM292923), which was positive in both assays, confirmed the identification of ACLSV. The obtained sequence shows 93% nucleotide identity with an apple isolate of ACLSV (EMBL Accession No. AY677103). To our knowledge, these findings represent the first report of the presence of ACLSV in quince in Greece. They further indicate that at least for some host-cultivar/virus isolate combinations, ACLSV may be asymptomatic in quince and that the symptoms observed in the plants sampled are unrelated to ACLSV infection.

References: (1) T. Candresse et al. Acta Hortic. 386:136, 1995. (2) J. C. Desvignes. Page 202 in: Virus Diseases of Fruit Trees. CTIFL Publishing, 1999. (3) S. Paunovic and M. Rankovic. Jugosl. Vocarstvo 31:231, 1997.
Late Season Occurrence of Soybean Rust Caused by Phakopsora pachyrhizi on Soybean in Illinois
Authors: Hartman G. L. , Hines R. A. , Faulkner C. D. , Lynch T. N. , Pataky N.
Published: May 2007

Soybean rust, first reported in the continental United States in Louisiana in 2004 (2), is one of the most important foliar diseases of soybean worldwide. On 10 October 2006, 20 soybean leaflets from 20 plants at physiological maturity were arbitrarily collected in research plots near Glendale, IL at the University of Illinois Dixon Springs Agricultural Center in Pope County and sent by overnight courier. On 11 October, leaflets were examined with a dissecting microscope at the Soybean Disease Laboratory at the National Soybean Research Center, and then at the Plant Disease Clinic, University of Illinois. Tan, angular lesions that were 2 to 4 mm in diameter were observed on the lower leaf surfaces of two of the 20 leaflets. Within these lesions, there was one uredinum on one leaflet and four on the other leaflet exuding hyaline, echinulate urediniospores (20 × 25 μm). On 11 October 2006, these leaflets were sent by overnight courier to the USDA/APHIS/PPQ/NIS Laboratory, Beltsville, MD Plant Disease Clinic for identification by morphological examination and by PCR using primers specific to Phakopsora pachyrhizi (1). Both tests confirmed the presence of P. pachyrhizi. The 18 leaflets that did not have sporulating pustules on 11 October were incubated in the laboratory for 5 days at near 100% relative humidity. Following incubation, nine leaflets were observed to have uredinia exuding urediniospores with a range of 1 to 43 uredinia per leaflet. These results indicate that incubation may be necessary to maximize the potential to observe uredinia exuding urediniospores. To our knowledge, this is the first report of P. pachyrhizi infecting plants in Illinois.

References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.
First Report of Damping-Off of Durum Wheat Caused by Arthrinium sacchari in the Semi-Arid Saskatchewan Fields
Authors: Mavragani D. C. , Abdellatif L. , McConkey B. , Hamel C. , Vujanovic V.
Published: May 2007

Durum wheat (Triticum durum Desf.) is an important crop in western Canada. In 2005, Arthrinium sacchari was frequently isolated from soil and durum wheat plants of the semi-arid fields of Swift Current, Saskatchewan, Canada (50°16′N, 107°44′W). The susceptibility of durum wheat to damping-off caused by this fungus was evaluated. To our knowledge, this is the first report of A. sacchari in North America (1) and the first mention of its association with durum wheat. DNA was extracted (MoBio Isolation Kit, Carlsbad, CA) from 2-week-old A. sacchari isolates (FBC.3, FBC.45, and FBC.143) grown on PDA. The internal transcribed spacer (ITS) of the rDNA was amplified from each isolate and sequenced (Plant Biotechnology Institute, Saskatoon, SK, Canada) and similarity analyses were performed using the BLAST search algorithm in GenBank. All three sequences (Accession Nos. EF076710, EF076711, and EF076712A) showed 99% similarity with A. sacchari (Accession No. AF393679). An in vitro assay was performed by placing 1-cm2 agar plugs containing mycelia of A. sacchari (FBC.3, FBC.45, and FBC.143) onto surface-sterilized durum. Surface-sterilized seeds inoculated in the same way with Fusarium graminearum or F. avenaceum were used as negative controls, and noninoculated surface-sterilized seeds were used as a positive control. A second in vitro assay involved inoculating the same isolates onto seeds placed in sterilized sandy soil. In both assays, 10 seeds per petri plate and three plates per treatment were used and plates were incubated at 21°C for 1 week in darkness. All experiments were performed twice. On PDA, preemergence damping-off was found in 60% of A. sacchari FBC.3, 55% of A. sacchari FBC.45 and FBC.143, 50% of F. avenaceum, and 58% of F. graminearum inoculated seeds. In sterilized soil, the incidence of preemergence damping-off ranged from 43 to 30%. Subsequent incubation over a period of 3 weeks resulted in 100% postemergence damping-off in A. sacchari FBC.45 and FBC.3 as well as in both Fusarium spp. inoculated controls, 60% postemergence damping-off in A. sacchari FBC.143, and no damping-off in the noninoculated control. Arthrinium and Fusarium spp. were reisolated only from symptomatic plants, satisfying Koch's postulates. In conclusion, durum wheat is highly susceptible to damping-off caused by A. sacchari, showing characteristic dark brown or violet lesions in infected tissues. A. sacchari was previously reported to be present in South America and eastern Asia. In China, it is considered an important mycotoxigenic species (2). Thus, infection of durum wheat crops with A. sacchari could pose a significant threat to North American wheat production.

References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2006. (2) X. J. Liu et al. Acta Mycol. Sinica 7:221, 1988.
First Report of the Perfect Stage of Powdery Mildew of Sugar Beet in North Dakota Caused by Erysiphe polygoni
Authors: Bradley C. A. , Burlakoti P. , Nelson R. S. , Khan M. F. R.
Published: May 2007

Powdery mildew caused by Erysiphe polygoni was widespread on sugar beet (Beta vulgaris) in North Dakota during 2006. This disease is generally not prevalent in the state because of the application of fungicides, which also have efficacy against powdery mildew, for control of Cercospora leaf spot caused by Cercospora beticola. Because Cercospora leaf spot pressure was low in 2006, fewer fungicide applications were made in the state, thus allowing for more observations of powdery mildew. Leaf samples from four fields near Amenia, Minto, Prosper, and St. Thomas, ND were collected in mid-September to look for the perfect stage of E. polygoni, since this has recently been observed in Idaho, Colorado, Montana, and Nebraska (1–3). Only the leaves collected from the field near Amenia had visible immature (yellow and brown) globose ascomata; ascomata were not observed on the leaves collected in the other fields. Additional leaves were collected from the field near Amenia in early October; these leaves had immature and mature (black) globose ascomata that were 70 to 105 μm in diameter. Mature ascomata contained ovoid to elliptic asci with one to four hyaline-to-golden pigmented ascospores (20 to 25 × 12 to 20 μm). The color, shape, and size of ascomata, asci, and ascospores were similar to previously reported observations (1–4). The prevalence of the perfect stage in North Dakota is unknown, since no statewide surveys were conducted. To our knowledge, this is the first report of the perfect stage of E. polygoni on sugar beet in North Dakota. The occurrence of the perfect stage could lead to a means for overwintering in this area. Because of the means for genetic recombination, the risk of fungicide resistance and the development of races may increase.

References: (1) J. J. Gallian and L. E. Hanson. Plant Dis. 87:200, 2003. (2) R. M. Harveson. Plant Dis. 88:1049, 2004. (3) B. Jacobsen et al. Plant Dis. 89:1362, 2005. (4) E. G. Ruppel. Powdery mildew. Pages 13–15 in: Compendium of Beet Diseases and Insects. E. D. Whitney and J. E. Duffus, eds. The American Phytopathological Society. St. Paul, MN, 1986.
Artificial Inoculation of Wheat for Selecting Resistance to Stagonospora Nodorum Blotch
Authors: Cowger Christina , Murphy J. Paul
Published: May 2007

In the eastern United States, natural epidemics of Stagonospora nodorum blotch (SNB) are not consistently severe enough to facilitate substantial progress in breeding moderately resistant cultivars of soft red winter wheat. We compared three artificial inoculation methods to natural inoculum in a field experiment involving seven wheat (Triticum aestivum) cultivars with varying levels of SNB resistance. Artificial inoculation methods were: Phaeosphaeria nodorum conidia applied by atomization to three- to four-leaf wheat in early winter, P. nodorum conidia applied by atomization at boot stage in late spring, and P. nodorum-infected wheat straw applied in early winter. The experiment was conducted at Kinston and Plymouth, NC, in 2003–2004, 2004–2005, and 2005–2006, and all treatments had three replicates. Percent diseased canopy was assessed and comparisons were made using disease severity at a single date (early to soft dough stage) and area under the disease progress curve (AUDPC). The relative resistance level of cultivars was consistent across sites, years, and inoculum methods, although the rankings of moderately susceptible and susceptible cultivars were sometimes switched. On average, late spores and straw caused significantly more disease than early spores or natural inoculum (P ≤ 0.05). Biplot analysis indicated that all artificial methods had a higher mean capacity to discriminate among cultivars than did natural inoculum (P ≤ 0.05). On average, artificial inoculation increased the capacity of environments to separate wheat cultivars by SNB resistance.
Pre- and Post-Infection Activity of Azoxystrobin, Pyraclostrobin, Mefenoxam, and Phosphite Against Leather Rot of Strawberry, Caused by Phytophthora cactorum
Authors: Rebollar-Alviter A. , Madden L. V. , Ellis M. A.
Published: May 2007

Pre- and post-infection activity of azoxystrobin, pyraclostrobin, mefenoxam, and phosphite against leather rot of strawberry, caused by Phytophthora cactorum, was determined under greenhouse conditions. Strawberry plants (cv. Honeoye) were grown in pots, and attached fruit at the green-to-white stage of development were used in evaluations. Plants and fruit were sprayed to runoff with the above-mentioned fungicides either before (protectant) or after (curative) inoculation with a zoospore suspension (105 zoospores/ml) of P. cactorum. Inoculated plants with fruit were placed in a mist chamber for 12 h to ensure infection. Fungicides were applied at either 2, 4, or 7 days before inoculation or 13, 24, 36, or 48 h after inoculation. Incidence (proportion of diseased fruit) was recorded 6 days after inoculation. Azoxystrobin and pyraclostrobin provided protectant activity for up to 7 days before inoculation, but only slight curative activity when applied 13 h after inoculation. Phosphite and mefenoxam also provided protection for up to 7 days, as well as curative activity of at least 36 h. There were no significant differences in protectant activity among the QoI fungicides azoxystrobin and pyraclostrobin, phosphite and mefenoxam.
Environmental Monitoring and Exploratory Development of a Predictive Model for Dead Spot of Creeping Bentgrass
Authors: Kaminski John E. , Dernoeden Peter H. , Fidanza Michael A.
Published: May 2007

Dead spot of creeping bentgrass is incited by Ophiosphaerella agrostis. The objectives of this 3-year field study were to: (i) elucidate environmental conditions associated with the expression of dead spot symptoms, (ii) develop a model to assist in predicting the appearance of dead spot symptoms and epidemics in creeping bentgrass, and (iii) elucidate the association between ascospore release and the appearance of new dead spot symptoms. Environmental parameters measured included relative humidity (RH), air (AT) and soil (ST) temperatures, solar irradiance (SOL), precipitation and irrigation (RAIN), and leaf wetness duration (LWD). Dead spot symptoms generally did not occur at temperatures (air or soil) below 15°C. Two descriptive models were developed that predicted the appearance of dead spot symptoms with an accuracy of 74 to 80%. Between 1 May and 31 October 2000 to 2002, the appearance of new dead spot infection centers was most accurately predicted (80%) by the single parameter of STMean ≥ 20°C. In years with severe levels of dead spot, the occurrence of major infection events was predicted on 37 of 40 days (93%). A combination of elevated air (ATMax ≥ 27°C) and soil (STMean ≥ 18°C) temperatures, low relative humidity (RHMean ≤ 80%), shortened periods of leaf wetness (LWD ≤ 14 h), and high levels of solar radiation (SOLMean ≥ 230 W m−2) were associated with the development of major dead spot epidemics. Ascospore discharge and the appearance of new infection centers occurred in a cyclic pattern that peaked about every 12 days. New infection centers appeared 3 to 10 days after the release of a large number of ascospores.
Host Range and Phylogeny of Fusarium solani f. sp. eumartii from Potato and Tomato in California
Authors: Romberg M. K. , Davis R. M.
Published: May 2007

Fusarium solani f. sp. eumartii, historically considered solely a pathogen of potato (Solanum tuberosum), was associated with tomato plants (Lycopersicon esculentum) exhibiting foot rot symptoms in California. The pathogenicity of California isolates of F. solani f. sp. eumartii from potato plants with Eumartii wilt symptoms and tomato plants with foot rot symptoms was determined on potato, tomato, pepper (Capsicum anuum), and eggplant (S. melongena). Isolates from both potato and tomato caused dry rot symptoms on potato tubers and root or collar rot on all four host species in the greenhouse. In field trials, isolates from both tomato and potato were pathogenic on tomato, potato, and pepper, confirming that the host range of F. solani f. sp. eumartii is not limited to potato. The phylogeny of isolates from potato and tomato was determined based on sequences of two DNA fragments: rDNA internal transcribed spacer regions and partial sequences of elongation factor 1-α. All of the California isolates of F. solani f. sp eumartii from tomato and potato formed a single monophyletic clade distinct from other formae speciales and mating populations of F. solani. The results of this study demonstrate that Eumartii wilt and tomato foot rot in California both are caused by F. solani f. sp. eumartii.
Survival of Inoculum of Phytophthora capsici in Soil Through Time Under Different Soil Treatments
Authors: French-Monar Ronald D. , Jones Jeffrey B. , Ozores-Hampton Monica , Roberts Pamela D.
Published: May 2007

From September 2001 until August 2002 and from September 2002 until August 2003, inoculum of Phytophthora capsici consisting of mycelium and oospores was buried in soil under three different soil treatments: soil solarization, fumigation with methyl bromide and chloropicrin, and white-on-black plastic mulch without fumigation or solarization. The effect of these soil treatments on the population and survival of P. capsici was evaluated through time after 28, 63, 119, 175, 245, and 343 days. Three techniques were used for detection of the localized inoculum in soil: soil dilution plating (SDP), a modified soil dilution plating technique with an overlay assay to allow for extra incubation (mSDPO), and lemon leaf baiting of soil (LLB). No viable inoculum was detected from any soil samples from the fumigated plots regardless of the soil detection technique used. By the last sampling date, viable oospore inoculum was still detected in both soil solarization and nontreated soils, but only using mSDPO and LLB. Overall, the mSDPO assay was the most sensitive assay, followed by LLB. Using mSDPO, populations in the last sampling date were 32.9 CFU/g soil for the untreated plots and 14.7 CFU/g soil for the solarized plots. Survival of P. capsici for a year would indicate that oospores have the potential to survive from year to year, and possibly much longer, in Florida and other locations.
Characterization of a Phytoplasma Associated with Cabbage Yellows in Iran
Authors: Salehi M. , Izadpanah K. , Siampour M.
Published: May 2007

In 2001, a disease tentatively named Iranian cabbage yellows (ICY) was observed in cabbage fields of Zarghan (Fars Province, Iran). The major symptoms of the disease were yellowing, little leaves, plant stunting, opening of the head, and proliferation of the buds at the base of the stem into a witches'-broom. Among leafhoppers collected in cabbage fields, only Circulifer haematoceps transmitted the ICY agent. The disease agent was transmitted by the leafhopper from cabbage to cabbage, cauliflower, rape, and periwinkle, causing phytoplasma-type symptoms in these plants. Polymerase chain reaction (PCR) using phytoplasma-specific primer pair P1/P7 and nested PCR using P1/P7 and R16F2n/R16R2 primer pairs amplified products of expected size (1.8 and 1.2 kb, respectively) from symptomatic cabbage plants. Both restriction fragment length polymorphism (RFLP) of nested PCR products (1.2 kb) and phylogenetic analyses of 16S–23S rDNA spacer region sequence indicated that the ICY phytoplasma had the closest relationship to subgroup A members of the clover proliferation group, including beet leafhopper-transmitted virescence agent, ‘Candidatus Phytoplasma trifolii’, Columbia Basin potato purple top phytoplasma, and vinca virescence phytoplasma. Cabbage is reported as a new natural host to the 16SrVI group of phytoplasmas.