bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Thielaviopsis paradoxa Causing Fruit Rot on Sala (Salacca edulis) in Thailand
Authors: Soytong K. , Jitkasemsuk S.
Published: May 2007

Sala (Salacca edulis, a hybrid between S. wallichiana and S. glabrescens) is extensively cultivated in Southeast Asia for its highly valued fruit (1). During the rainy season in 1999, a fruit rot of sala caused by Thielaviopsis paradoxa (2) was observed to occur on immature and mature fruits for the first time in Trad and Chantaburi provinces, Thailand. Infected fruit discolored brown to black and appeared rotted with white mycelia on the lesions. Fruit eventually abscised. Conidiophores of the fungus were usually straight and hyaline to pale brown. The conidia (8.75 to 12.5 × 3.75 to 5.5 μm) were cylindrical to elliptical and also hyaline to pale brown. The brown, smooth, and ovate chlamydospores (15 to 25 × 8.7 to 14.5 μm) were borne terminally in chains from short hyphal branches. To fulfill Koch's postulates, six isolates of the fungus were grown on potato-dextrose agar for 7 days. Plugs of mycelia agar (0.5 cm in diameter) from each isolate were inoculated onto fresh fruit (four fruit per isolate) after the surface was disinfected with 10% sodium hypochlorite for 3 min. Non-inoculated fruits with sterile distilled water were served as controls. After incubation at 30°C and 80% RH in a humidity chamber for 4 days, lesions occurred on all the inoculated fruit. The fungus was subsequently recovered from the lesions. One isolate has been deposited in the Fungal Culture Collection, King Mongkut's Institute of Technology, Ladkrabang, Thailand (TF 1-6/1999).

References: (1) G. Hamballi et al. 1989. Proceedings of the First PROSEA International Symposia, Indonesia. (2) A. Johnston and C. Booth. 1983. Plant Pathologist's Pocketbook. CMI, Surrey, England.
Identification of Co-1 Anthracnose Resistance and Linked Molecular Markers in Common Bean Line A193
Authors: Mendoza Azucena , Hernández Fernando , Hernández Sanjuana , Ruíz Daniel , de la Vega Octavio Martínez , Mora Gustavo , Acosta Jorge , Simpson June
Published: May 2007

Phaseolus vulgaris line A193 has been shown to be widely resistant to Colletotrichum lindemuthianum, including race 1472, one of the most virulent races of C. lindemuthianum characterized. Resistance to C. lindemuthianum race 1472 in P. vulgaris line A193 was investigated in segregating F2 and F2.3 populations from a cross between A193 and Flor de Mayo Bajio (a commercial cultivar highly susceptible to C. lindemuthianum). Resistance to 1472 in A193 was determined to be conditioned by a single dominant gene. Inoculation of crosses between A193 and cultivars Michigan Dark Red Kidney and Perry Marrow with race 1472 suggest that resistance in A193 is conditioned by the Co-1 gene. Inoculation of the cross A193 × Perry Marrow with C. lindemuthianum race 2, demonstrated that resistance to race 2 in Perry Marrow is also conditioned by a single dominant gene and is distinct to resistance in A193 or Michigan Dark Red Kidney. Three AFLP markers (ECAG/MACC-1, EACA/MAGA-2, EAGG/MAAC-8) linked in repulsion to the Co-1 locus were identified by screening the A193 × Flor de Mayo F2 population with 314 random amplified polymorphic DNA, amplified fragment length polymorphism, and restriction fragment length polymorphism markers. The two most closely linked markers should be useful in marker-assisted selection for Co-1.
Comparison of Dig-Labeled PCR, Nested PCR, and ELISA for the Detection of Clavibacter michiganensis subsp. sepedonicus in Field-Grown Potatoes
Authors: Lee I.-M. , Lukaesko L. A. , Maroon C. J. M.
Published: May 2007

The sensitivity of digoxigenin- (dig-) labeled polymerase chain reaction (PCR) was compared with nested PCR and enzyme-linked immunosorbent assay (ELISA) for the detection of the potato ring rot bacterium, Clavibacter michiganensis subsp. sepedonicus, in seed potatoes and stem tissues. The bacterial DNA was extracted from chopped tuber or stem tissue by a modified hot alkaline DNA extraction method. C. michiganensis subsp. sepedonicus specific DNA sequence was amplified by dig-labeled PCR with the primer pair CMSIF1/CMSIR1 previously designed based on the insertion element IS1121 of C. michiganensis subsp. sepedonicus. Dig-labeled PCR products were then blotted on a nylon membrane and the signal was detected by a colorimetric assay using alkaline phosphatase. The new assay procedure has a detection sensitivity close to that of nested PCR and simplicity of the standard ELISA procedure commonly used commercially. The dig-labeled PCR assay was more sensitive than ELISA and can be used to detect C. michiganensis subsp. sepedonicus in symptomless field potato tubers.
Xanthomonas albilineans Haplotype B Responsible for a Recent Sugarcane Leaf Scald Disease Outbreak in Cuba
Authors: Diaz M. , Peralta E. L. , Iglesia A. , Pazos V. , Carvajal O. , Perez M. P. , Giglioti E. A. , Gagliardi P. R. , Wendland A. , Camargo L. E. A.
Published: May 2007

Over the past 3 years, the incidence of sugarcane leaf scald disease (LSD) caused by Xanthomonas albilineans has increased at alarming rates in some Caribbean countries. LSD was in latent phase since 1978, when the disease was reported in Cuba, until February 1998 when typical symptoms were observed in germ plasm collections and in some commercial plantings. More than 150 bacterial isolates from different sugarcane varieties and from different localities were isolated on Wilbrink agar medium and characterized. All isolates had shown similar cultural and biochemical patterns. However, serological differences between isolates from the recent outbreak and the ones obtained prior to 1998 were detected by indirect ELISA testing. Differences between Cuban isolates obtained prior to 1998 and those from the recent outbreak were confirmed by analysis of repetitive DNA sequences dispersed throughout the genome. According to the pattern obtained, the newer isolates were similar to reference strains classified as haplotype B by pulsed field gel electrophoresis (1). It is concluded that the recent outbreak of LSD was caused by a strain different than the ones previously detected in Cuba.

Reference: (1) M. J. Davis et al. Phytopathology 87:316, 1997.
Effective Biomass Reduction of the Invasive Weed Species Banana Poka by Septoria Leaf Spot
Authors: Trujillo Eduardo E. , Kadooka Chris , Tanimoto Victor , Bergfeld Steve , Shishido Glenn , Kawakami Galen
Published: May 2007

Inoculations of Septoria passiflorae for biological control of banana poka (Passiflora tripartita var. tripartita) at different forest sites in Hawaii, Kauai, and Maui resulted in successful establishment of the Septoria leaf spot disease at all sites during 1996. Semi-annual monitoring of sites in 1997 revealed low disease incidence and no disease spread to adjacent non-inoculated plants. Site inspections in March 1998 revealed light disease epidemics causing visible defoliation at inoculated sites on Kauai and Maui. Banana poka biomass reduction at sites with light epidemics of the disease in Kauai and Maui were estimated to be less than 10% in 1998, whereas in 1999 biomass reduction ranged from 50 to 95%. Five of 11 inoculation sites in 1996 on the island of Hawaii showed no disease. These five sites on Kaloko had frequent acid rainfall averaging 3.2 pH, which inhibited spore germination and infection. Six sites, free of acid rain, three at Hilo Forest Reserve and three at Puuwaawaa Wildlife Sanctuary, had severe disease epidemics by 1998, and vine defoliation was >90%. Widespread epidemics of the disease occurred in 1999, resulting in estimated 80 to 95% biomass reductions in more than 2,000 hectares of native forest infested with banana poka.
Multiplication and Movement of a Citrus Strain ofXylella fastidiosaWithin Sweet Orange
Authors: Almeida R. P. P. , Pereira E. F. , Purcell A. H. , Lopes J. R. S.
Published: May 2007

Populations of cultivable cells of a citrus variegated chlorosis (CVC) disease strain of Xylella fastidiosa in stems and leaf veins of sweet orange (Citrus sinensis (L.) Osbeck) seedlings were estimated by dilution plating at 1, 2, 4, 8, and 16 weeks after needle inoculation. Cell populations ranged from log 4 to log 5 CFU/g of tissue after 1 week and increased to log 5 to log 7 CFU/g (median log 6) after 8 to 16 weeks. Recovery of greater than log 5 CFU/g from stem nodes distal to the inoculation site indicated systemic movement of the bacteria. Foliar symptoms in inoculated seedlings first appeared after 8 weeks. Population estimates from leaf veins of CVC-affected trees in citrus groves were in the same range but slightly lower (average log 5.8 CFU/g). X. fastidiosa was isolated from citrus more efficiently in periwinkle wilt-GelRite (PWG) and periwinkle wilt (PW) media than in charcoal-yeast extract with ACES buffer (BCYE) medium The relatively lower populations of cultivable cells of X. fastidiosa in citrus with CVC symptoms, compared with those reported in grapevines with Pierce's disease, suggest that most cells of X. fastidiosa within symptomatic citrus may be dead, explaining in part the low rates of vector transmission from citrus to citrus.
Effects of Deficit Irrigation on Hull Rot Disease of Almond Trees Caused by Monilinia fructicola and Rhizopus stolonifer
Authors: Teviotdale B. L. , Goldhamer D. A. , Viveros M.
Published: May 2007

Almond trees were irrigated from March through November 1994 and 1995 with 70, 85, and 100% of potential evapotranspiration (ETc). Deficit irrigation was accomplished by delivering 70 or 85% of ETc at every irrigation (sustained) or 50% of ETc during 1 June to 31 July (70 regulated) or 1 to 15 July (85 regulated). The natural incidence of dead leaf clusters and dead spurs, twigs, and small branches, measured at harvest, lessened with decreasing amounts of water, and regulated deficits were more effective than sustained deficits in reducing disease. Fruit at early dehiscence on trees in each of the five irrigation treatments were inoculated with 0.1 ml of suspensions of 104 spores per ml of Monilinia fructicola or Rhizopus stolonifer. Monilinia fructicola caused more hull rot than R. stolonifer, and both pathogens responded similarly to the irrigation treatments. The rate of fruit maturation was monitored for approximately 4 weeks before harvest by scoring the percent abscission and dehiscence and measuring the hull moisture content of fruit on trees in each irrigation treatment. Dry kernel weight was determined at harvest. Maturation was slower and kernel weight greater in treatments receiving 85% of ETc than 70% or those under sustained compared with regulated irrigation regimes.
A New Badnavirus in Ribes Species, its Detection by PCR, and its Close Association with Gooseberry Vein Banding Disease
Authors: Jones A. Teifion , McGavin W. J. , Geering A. D. W. , Lockhart B. E. L.
Published: May 2007

Gooseberry vein banding disease (GVBD) affects Ribes species and cultivars worldwide. It is the second most important virus-like disease in these crops after black currant reversion disease. In this paper, we describe a bacilliform virus, Gooseberry vein banding associated virus (GVBAV), which is associated closely with GVBD, and provide evidence that GVBAV is a distinct species within the genus Badnavirus. Purified GVBAV particles were ca. 120 × 30 nm in size and contained dsDNA. The sequence of a 1.5-kb DNA fragment amplified from viral genomic DNA was similar to those of a wide range of badnaviruses and contained motifs characteristic of the RNase H domain of the badnavirus open reading frame (ORF) III polyprotein. Phylogenetic analyses suggest that GVBAV is most closely related to Spiraea yellow leaf spot virus. Using sequence derived from the polymerase chain reaction (PCR)-amplified DNA fragment, virus-specific primers were designed. These primers were used in PCR to assay for GVBAV in a range of Ribes germplasm affected with GVBD, with other unrelated virus-like diseases and viruses found in Ribes, and in healthy plants. GVBAV was detected in all of 58 GVBD-affected plants from diverse sources, but not from healthy Ribes plants nor from plants infected with other viruses.
Effect of Desiccants and Herbicides on Germination of Pseudosclerotia and Development of Apothecia ofMonilinia vaccinii-corymbosi
Authors: Cox K. D. , Scherm H.
Published: May 2007

Pseudosclerotia (infected, mummified fruit) are the only source of primary inoculum of Monilinia vaccinii-corymbosi, the causal agent of mummy berry disease of blueberry. Laboratory applications of potential inhibitors of carpogenic germination were made to pseudosclerotia at three distinct developmental stages, i.e., ungerminated pseudosclerotia, pseudosclerotia with emerging stipes, and those with mature apothecia. Potential inhibitors evaluated included soybean oil and ammonium thiosulfate (two desiccants used experimentally as bloom thinners in fruit crops) and diuron and simazine (two commonly used herbicides), each applied in an aqueous suspension with 3% Latron B-1956 surfactant. Various aspects of carpogenic germination including the percentage of pseudosclerotia that produced stipes or apothecia, the number of stipes or apothecia per pseudosclerotium, the percentage of stipes that developed into apothecia, longevity of stipes and apothecia, and ascospore numbers were assessed. Compared with water, application of ammonium thiosulfate (2%) and diuron (2%) reduced stipe and apothecium production when sprayed on ungerminated pseudosclerotia, but these reductions were generally not significantly different from those achieved with Latron B applied alone (P > 0.05). The two compounds, however, completely inhibited the development of stipes into apothecia when applied to pseudosclerotia with stipes and caused a >3-fold reduction in apothecium longevity when applied to pseudosclerotia with mature apothecia. Application of simazine (2%) before germination or at stipe emergence resulted in the development of malformed apothecia from which no ascospores were recovered; stipe and apothecium longevity were also reduced. Soybean oil (15%) and Latron B applied alone had weak or inconsistent effects on most aspects of carpogenic germination of pseudosclerotia, although both compounds, when applied at stipe emergence, significantly reduced ascospore numbers in subsequently formed apothecia. The results suggest that diuron and simazine applied for weed control in commercial blueberry plantings may have beneficial side effects in reducing carpogenic germination of pseudosclerotia. The strong inhibitory effect of ammonium thiosulfate on all aspects of carpogenic germination, along with its value as a nitrogen fertilizer and ancillary herbicide, warrants further evaluation of this compound's performance and economics in the field.
Current Status and New Natural Hosts of Tomato yellow leaf curl virus (TYLCV) in Spain
Authors: Jordá C. , Font I. , Martínez P. , Juarez M. , Ortega A. , Lacasa A.
Published: May 2007

Tomato yellow leaf curl virus (TYLCV) is a major constraint to tomato production in Spain. This virus was observed for the first time in several tomato fields in Murcia (Spain) in the autumn of 1992 and Canary Islands in 1999. Currently the virus is prevalent along the Mediterranean coast of Spain (provinces of Málaga, Granada, Almería, Murcia, Alicante, Valencia, and Barcelona) and in the Canary Islands. Two viral species have been identified in Spain, TYLCV-Sar in 1992 and TYLCV-Is in 1997. TYLCV-Is is more severe than TYLCV-Sar and produces the greatest economic losses. Curling of leaflets, yellowing, and growth reduction are more pronounced in plants infected with TYLCV-Is than in those infected with TYLCV-Sar. In order to study the presence and behavior of both viral species in the affected area, over 1,320 tomato plants were sampled. DNA was extracted from the samples and analyzed by polymerase chain reaction (PCR) amplification. The degenerate primer pair for Begomovirus detection (AV494/AC1048) (2) was used to amplify the core region of the capsid protein gene. The amplified fragments were later analysed by restriction fragment length polymorphism (RFLP) with HaeIII enzyme to differentiate between TYLCV-Is and TYLCV-Sar species. The results showed that TYLCV-Sar (43.4%) and TYLCV-Is (56.6%) coexist in tomato crops and, in contrast with previous results (1), displacement of TYLCV-Sar for TYLCV-Is was observed. A search for the alternative hosts that may serve as virus reservoirs in areas where the virus is prevalent involved testing 210 samples of 95 species of weeds by PCR, with the same primers. The following species were found to be infected: Conyza sumatrensis (Retz.) E. Walker, Convolvulus sp., Cuscuta sp., Chenopodium murale L., Datura stramonium L., Dittrichia viscosa (L.) W. Greuter, Malva parviflora L., and Solanum nigrum L. This is the first reference of C. sumatrensis, Convolvulus sp., Cuscuta sp., and Ch. murale as natural hosts of TYLCV. These plants were symptomless.

References: (1) S. Sanchez-Campos et al. Phytopathology 89:1038, 1999. (2) S. D. Wyatt et al. Phytopathology 86:1288, 1996.
First Report of Barley yellow striate mosaic virus Infecting Barley and Wheat in Lebanon
Authors: Makkouk K. M. , Ghulam W. , Kumari S. G.
Published: May 2007

Symptoms suggestive of virus infection in barley, bread wheat, and durum wheat were observed at high incidence in November 2000 in Terbol, Beqa'a Valley, Lebanon. The symptoms were mainly stunting, accompanied by leaf striping and yellowing. Symptomatic plant samples (27 barley, 37 bread wheat, and 81 durum wheat) were collected and tested for the presence of four different viruses by tissue-blot immunoassay (TBIA) (1) at the Virology Laboratory of ICARDA, Aleppo, Syria. Antisera used were for Barley stripe mosaic virus (BSMV, genus Hordeivirus) (2); Barley yellow dwarf virus (BYDV, genus Luteovirus, family Luteoviridae) (PAV serotype) (2); Wheat streak mosaic virus (WSMV, genus Tritimovirus, family Potyviridae) (3); and Barley yellow striate mosaic virus (BYSMV, genus Cytorhabdovirus, family Rhabdoviridae) provided by M. Conti, Instituto di Fitovirologia applicata, Turino, Italy. BYSMV was detected in 12 barley, 18 bread wheat, and 56 durum wheat samples; the corresponding numbers of barley, bread wheat, and durum wheat plants testing positive for BYDV-PAV were 4, 7, and 6, respectively. BSMV and WSMV were not detected in any of the samples tested. BYSMV was purified from infected wheat plants, and the purified preparation had a UV 260:280 ratio of 1.18, typical of Rhabdoviruses. In SDS-polyacrylamide gel electrophoresis, the purified virus preparation indicated the presence of 66, 47, and 15 kDa structural proteins, typical of the G, N and M proteins of Rhabdoviruses. In western blot, the 66 and 47 kDa protein bands reacted strongly with BYSMV antiserum. This is the first record of BYSMV infecting barley and wheat in Lebanon.

References: (1) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (2) K. M. Makkouk and S. G. Kumari. Rachis Newsl. 12:24, 1993. (3) K. M. Makkouk and S. G. Kumari. Rachis Newsl. 16:74, 1997.
Assessment of Barriers to Prevent the Development of Potato Tuber Blight Caused by Phytophthora infestans
Authors: Glass J. R. , Johnson K. B. , Powelson M. L.
Published: May 2007

Experiments were conducted in an irrigated, sandy loam soil to evaluate mulches and hill sizes as barriers to prevent the development of potato tuber blight caused by Phytophthora infestans. In mulching experiments, five treatments were applied to field plots of cv. Red LaSoda: 1, no mulch; 2, polyurethane spray foam in an 8-cm-diameter area immediately surrounding the plant stem; 3, black polyethylene film over the entire hill except near the stem; 4, a combination of treatments 2 and 3; and 5, a water-permeable, agricultural textile treated with copper hydroxide applied over the same hill area as in treatment 3. In 1998, the incidence of tuber blight in plots mulched with black film (treatments 3 and 4) averaged 32% compared with 56% in plots without this mulch (treatments 1 and 2). In 1999, incidence of tuber blight in plots with and without black film averaged 9 and 20%, respectively. Mulching the stem area with spray foam (treatments 2 and 3) did not reduce the incidence of blighted tubers when compared with the appropriate control. The copper-treated textile mulch (treatment 5) provided reductions in the incidence of tuber blight similar to those observed with the use of black polyethylene film. In a hill size experiment conducted once in 1998 and twice in 1999, three hill size treatments were established on cvs. Red LaSoda, Shepody, and Russet Burbank. Red LaSoda was the most susceptible and Russet Burbank the least susceptible to tuber blight. Comparison of blight incidence in tubers classified by depth in the hill revealed few differences among the hill size treatments, although over all treatments, tubers covered with more than 15 cm of soil had a lower incidence of blight (1 to 14%) than tubers with less soil cover (13 to 59%). Most tuber infections were apparently initiated in eyes and were not concentrated on a portion of the tuber such as the stolon (proximal) or distal end. The fact that black film and textile mulches reduced tuber infection indicates that inoculum of P. infestans can move from foliage to tubers through soil and that inoculum movement is not limited to large channels in the hill such as those created by the potato stems. The mulch treatments, however, provided only partial protection of tubers, limiting the practicality of such treatments to commercial producers. Hill size treatments had little effect on tuber blight incidence, indicating that adequate suppression of tuber infection in an environment conducive to late blight may be inseparably linked to adequate suppression of the foliar phase.
A New Phytophthora Root Disease of Alder in Italy
Authors: Santini A. , Barzanti G. P. , Capretti P.
Published: May 2007

A Phytophthora was found associated with wilt and mortality of Italian alder (Alnus cordata) seedlings in a nursery in northern Tuscany, Central Italy. This disease is one of the major constraints to alder survival in northern Europe (3). Symptoms included sparse yellowish brown foliage with abnormally small leaves, dark stained necrosis of the bark at the collar level, and reduction of the root system due to the death of the tap root and lateral roots. These symptoms resemble those on chestnut, walnut, and oak plantlets colonized by P. cambivora. The diseased seedlings were 1 to 2 years old and were grown on both beds and soil. Tissue isolation from infected parts of the plants yielded a P. cambivora-like species in culture. Pure cultures were appressed and felty in appearance with sparse or no aerial mycelium when grown on V8 agar, carrot agar, or potato dextrose agar. Sporangia were ovoid, non-papillate, and averaged 51.8 μm in length and 36.6 μm in width (range: 45 to 60 μm and 30 to 40 μm). The isolates were homothallic with smooth-walled oogonia with a diameter ranging from 20 to 45 μm and with two-celled, amphigynous antheridia. Colonies showed rapid development at 25°C (mean radial growth = 6 mm/day), but at 30°C growth was strongly inhibited, unlike P. cambivora isolates previously collected in the same area, which were more thermophilic. The morpho-physiological features of the alder isolates resembled those of the Swedish variant of the alder Phytophthora (2). Identification was confirmed by C.M. Brasier (Forestry Authority Research Station, UK). Two-year-old alder seedlings (1.3 cm diameter, height 70 cm) grown in pots were wound-inoculated in the trunk. Six weeks after inoculation, symptoms were produced identical to those described above, as well as necrosis of the bark tissue varying in length from 0.5 to 3 cm. Isolations from diseased bark tissue yielded fungal colonies resembling those described above. The pathogen, described for the first time in England in 1995 (1), is now present throughout northern Europe. This is the first report for the Mediterranean region, which suggests that the fungus will cause disease in the drier and warmer climates of southern Europe.

References: (1) C. M. Brasier et al. Plant Pathol. 44:999, 1995. (2) C. M. Brasier et al. Proc. Natl. Acad. Sci. USA 96:5878, 1999. (3) J. N. Gibbs et al. Eur. J. For. Pathol. 29:39, 1999.
Recovery of Pyrenophora tritici-repentis from Barley and Reaction of 12 Cultivars to Five Races and Two Host-Specific Toxins
Authors: Ali S. , Francl L. J.
Published: May 2007

Barley, a collateral host of Pyrenophora tritici-repentis (cause of tan spot of wheat), could promote genetic variation in the fungal population and serve as a reservoir of local primary inoculum for a wheat crop in the next season. Samples of diseased barley leaves were collected from 35 locations in North Dakota during the 1999 growing season. P. tritici-repentis was recovered from 2 to 5% of the sampled lesions taken from three of the samples. The majority of the samples also harbored Pyrenophora teres, Stagnospora nodorum, and Cochliobolus sativus. All 10 isolates of P. tritici-repentis recovered from the samples were grouped as race 1, because they induced both necrosis and chlorosis on the appropriate wheat differentials. In addition, 12 barley cultivars were tested for their reaction to five races of P. tritici-repentis, and all were resistant. The fungus could not be recovered when isolations were later attempted from the inoculated leaves. Barley cultivars also were infiltrated with two host-specific toxins, Ptr ToxA and ToxB. They were insensitive, because they did not develop necrosis or chlorosis to the toxins. Our results indicate that barley is highly resistant to the fungus and is unaffected by its host-specific toxins. Prevalence of race 1 in a very low frequency on barley during the growing season suggests that barley does not play a significant role in tan spot epidemiology on wheat or promote variation in the fungal population.
Control of Postharvest Botrytis Fruit Rot with Preharvest Fungicide Applications in Annual Strawberry
Authors: Blacharski R. W. , Bartz J. A. , Xiao C. L. , Legard D. E.
Published: May 2007

The control of postharvest Botrytis fruit rot was evaluated during 1997-98 and 1998-99. Weekly applications of captan and thiram were examined at two or three different rates, respectively. Iprodione applications were combined with the captan and thiram treatments and also applied alone for two peak bloom periods. Strawberry fruit were harvested and graded twice weekly for marketable yield and preharvest incidence of Botrytis fruit rot. For postharvest evaluations, fruit from four harvests were selected and stored at 4°C, and Botrytis fruit rot incidence was recorded over 14 days of storage. Fungicide treatments reduced the incidence of preharvest Botrytis fruit rot and increased marketable yield. The incidence of postharvest Botrytis fruit rot was significantly affected by harvest date, length of time in storage, and fungicide treatment. The highest rate captan and thiram treatments had the least Botrytis fruit rot and the longest storage life. Reduced-rate captan and thiram treatments generally did not provide the same control as their respective high-rate treatments. Iprodione added to either the captan or thiram treatments did not consistently reduce the preharvest or postharvest incidence of Botrytis fruit rot or increase yield. Regular, full-rate fungicide treatments appear to be necessary to control Botrytis fruit rot in Florida and to provide the storage life necessary to reach distant markets.
Genetic Resistance of Pearl Millet Male-Sterile Lines to Diverse Indian Pathotypes of Sclerospora graminicola
Authors: Thakur R. P. , Rai K. N. , Rao V. P. , Rao A. S.
Published: May 2007

Single-cross F1 hybrid cultivars based on cytoplasmic-nuclear male-sterility (CMS) system have contributed significantly to increasing productivity of pearl millet (Pennisetum glaucum). Genetic resistance to downy mildew (Sclerospora graminicola) in parental lines is critical for successful commercial cultivation of a hybrid cultivar. In this study, 46 genetically diverse male-sterile lines (A-lines), including 42 test A-lines, four control A-lines, a commercial hybrid, and a highly susceptible line, were evaluated in disease nurseries at four diverse locations in India and compared with pathotype isolates from the same locations under greenhouse environments. Variability in downy mildew incidence (0 to 100%) due to genetic differences among lines, among pathotypes, and that due to line × pathotype interaction were all highly significant (P < 0.001). In the field experiment, eight of the 42 test A-lines, including 841A (control), that recorded ≤10% disease incidence, were identified as resistant compared with 84 to 100% incidence on the control susceptible line 7042S. Resistance in eight of these test A-lines (863A, ICMA 88004, -94333, -98222, -98111, -92777, and -96666) and 841A was confirmed against the four pathotypes in greenhouse experiments. Cluster analysis of downy mildew incidence data from field and greenhouse experiments, using the Euclidian distance, classified the 48 lines into four distinct groups with the above eight A-lines in the resistant group. These resistant A-lines would be useful in the development of F1 hybrids with stable resistance to diverse pathotypes of downy mildew in India.
Relative Susceptibility of Selected Apple Cultivars to Colletotrichum acutatum
Authors: Biggs A. R. , Miller Stephen S.
Published: May 2007

Eighteen apple cultivars were tested in the field and laboratory for their relative susceptibility to one of the bitter rot pathogens, Colletotrichum acutatum. Fruit were inoculated in the field at 3 to 4 weeks preharvest with cheesecloth strips soaked in a conidia suspension. In the laboratory, detached fruit were inoculated using a conidia suspension in capped, sterile microcentrifuge tubes attached to the fruit surface with modeling clay. The same fruit as above also were inoculated over a wound on the side opposite the nonwounded inoculation. Fruit were tested for relative susceptibility to the fungus with five criteria: disease incidence and severity of attached fruit in the field, disease incidence and severity of detached fruit in laboratory inoculations of nonwounded fruit, and disease severity in laboratory inoculations of wounded fruit. Relative cultivar ranks from field tests were not reproducible in the 2 years studied, whereas laboratory tests showed moderate reproducibility with nonparametric rank correlation tests. Based on the laboratory data from 2 years of study, cultivars were classified into four relative-susceptibility groups: most susceptible: Pristine, Honeycrisp, and Ginger Gold; highly susceptible Yataka, Sansa, Arlet, and Enterprise; moderately susceptible: Sunrise, Golden Supreme, PioneerMac, GoldRush, Golden Delicious, and Creston; and least susceptible: Fuji. Compared to previous cultivar rankings, the results of the present study indicate that new apple cultivars from the first NE-183 planting show no improvement in resistance to C. acutatum.
Wheat Straw Mulch and Its Impacts on Three Soilborne Pathogens of Peanut in Microplots
Authors: Ferguson Lisa M. , Shew B. B.
Published: May 2007

Experiments were conducted in 1992, 1993, and 1994 to determine the effects of surface residue on incidence of Cylindrocladium black rot (CBR), Sclerotinia blight, and Southern stem rot of peanut in microplots in North Carolina. Soil was infested with either Cylindrocladium parasiticum, Sclerotium rolfsii, or Sclerotinia minor and plots were planted with the peanut cultivars NC 7 or NC 10C. Wheat straw was applied to establish 80 to 90% soil-surface coverage. Disease incidence data were collected every 2 weeks in 1992 and weekly in 1993 and 1994. Southern stem rot incidence did not increase with straw amendment but final inoculum density of Sclerotium rolfsii was highest in straw-amended plots. Straw amendment enhanced CBR incidence in 1992, but had minimal effects in 1993 and 1994. Neither root rot severity nor inoculum density of C. parasiticum was affected by straw treatment. Straw application reduced Sclerotinia blight in 1992 and 1993 but not in 1994 compared with unamended plots. Initial inoculum density had the greatest impact on final Sclerotinia minor populations. Soil temperature and moisture were monitored in 1993 and 1994. Soil at 0 to 2 cm of depth in strawamended microplots was 1 to 2°C cooler than in unamended plots.
Powdery Mildew Caused by Erysiphe pisi on Alfalfa in Idaho and Oregon
Authors: Mohan S. K. , Bijman V. P. , Miller D. R.
Published: May 2007

During July to November 2000, alfalfa (Medicago sativa L.) plants with powdery mildew symptoms were observed in commercial hay and seed fields, research plots, and a greenhouse in southwestern Idaho (Canyon County) and eastern Oregon (Malheur County). Affected leaves and stems showed white, effuse, dense, amphigenous mycelium bearing Oidium conidia, often with necrotic, brown blotches or streaks. In July, symptoms and signs were found mostly on the lower stems and leaves, but by October, all aerial parts of the plants were involved. Based on location of the mycelium and the conidiophore and conidial characteristics, the fungus was identified as Erysiphe pisi (J. C. David, personal communication). Cleistothecia were not observed. Natural incidence of the disease, which varied from less than 5% infected plants in July to more than 90% infected plants in November, was observed in commercial fields of cvs. Pioneer 53V08 (hay), Sparta (hay), and DS 907 (seed); in research (seed production) plots on cvs. Alfagraze, Anchor, Barrier, Beaver, Cut'N'Graze, Rambler, and Rangelander; and in the greenhouse on cvs. Aggressor, Archer II, Nemagone, Pecos, and Robust. Greenhouse inoculations by dusting with conidia from infected alfalfa plants (cv. Pioneer 53V08) demonstrated the susceptibility of alfalfa cvs. Affinity, Amerigraze, Innovator, and Salado and pea (Pisum sativum L.) cvs. Aladdin, Badger, Bolero, Cabree, Dwarf Gray Sugar, Early Perfection, Encore, Lazor, Maestro, Melting Sugar, Novella, Pursur, Somerwood, Spring, Stampede, and Sugar Ann. Red clover (Trifolium pratense L.) cvs. Redland, Redland II, and Premier showed positive but limited symptoms (smaller colonies, scant mycelium, and brown necrosis) following inoculation. Uninoculated control plants remained free from powdery mildew. Previous reports of powdery mildew on alfalfa in the United States (2) have attributed it to E. polygoni (Massachusetts and Wyoming) or Oidium sp. (Hawaii). Recently, powdery mildew caused by E. pisi was reported from alfalfa in research nurseries and greenhouses in Wisconsin (1). To our knowledge, this is the first report of occurrence of powdery mildew of alfalfa caused by E. pisi in the northwestern U.S., and may constitute a potential new problem for hay and seed production in this region.

References: (1) J. I. Edmunds et al. Plant Dis. 82:832, 1998. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. APS Press, St. Paul, MN.
First Report of Basal Rot of Leek Caused by Fusarium culmorum in Spain
Authors: Armengol J. , Vicent A. , Sales R. , García-Jiménez J. , Rodríguez J. M.
Published: May 2007

A severe basal rot of leek (Allium porrum L.) was first observed in 1996 in Sueca (Valencia) eastern Spain, and again from 1998 to 2000 in several fields in Haro (La Rioja) northern Spain, where the disease caused significant economic losses. Leeks were stunted, wilted, and had water-soaked tissues with a characteristic reddish purple discoloration at the base of the stem. Affected plants could be pulled up easily because of rotting of the basal plate and root system. Similar symptoms were also observed on seedlings 2 to 3 weeks after transplanting. Isolations from symptomatic stems and roots onto potato dextrose agar (PDA) supplemented with 0.5 mg/ml of streptomycin sulfate (PDAS) consistently yielded a Fusarium sp. Isolates were transferred to potato sucrose agar (PSA) and synthetic low nutrient agar (SNA) and incubated at 25°C for 10 days with a 12-h photoperiod. The isolates were identified as Fusarium culmorum (Wm. G. Sm.) Sacc. based on colony morphology on PSA and phialide and conidial morphology on SNA. This disease has been described on garlic (1), but there are few reports about its incidence on leek (2). Pathogenicity tests were conducted on leek cvs. Alora, Axel, Casado, Goliath, and Varea using five isolates of F. culmorum from different locations. Ninety-day-old seedlings were inoculated by introducing a spore suspension to obtain a soil infested with the fungus at 104 colony-forming units (CFU)/g of potting mix (a sterilized mixture of equal portions [v/v] of soil, sand, and peat moss). Plants were maintained in a greenhouse at 20 to 30°C. Within 45 to 70 days after inoculation, symptoms developed that were similar to those observed in the field. The fungus was reisolated from affected plants, completing Koch's postulates. All isolates were pathogenic, and all leek cvs. were highly susceptible to the pathogen. To our knowledge, this is the first report of F. culmorum affecting leek in Spain.

References: (1) F. J. Crowe et al. Phytopathology 76:1094, 1986. (2) G. Tamietti and A. Garibaldi. Riv. di Patol. Veg. IV. 13:69, 1977.
Identification of Pepper mild mottle virus in Commercial Bell Pepper in Florida
Authors: Adkins S. , Lamb E. M. , Roberts P. D. , Gooch M. D. , Breman L. , Shuler K. D.
Published: May 2007

Pepper mild mottle virus (PMMoV) has been identified on pepper in Florida several times since 1997. Initial observations were on ornamental peppers (Capsicum chinense, C. frutescens, and C. annuum). However, in the winter growing seasons of 1999 and 2000, PMMoV was detected in several bell pepper (C. annuum) cultivars in commercial production fields in south Florida. Symptoms in bell pepper plants were observed to vary with plant age and cultivar, and included stunting of young plants and puckering and yellow mottling of leaves. Fruit was deformed (lumpy and mottled) and slightly reduced in size. Older fruit exhibited brown streaks and, in some cultivars, an undesirable color at maturity. Incidence in commercial bell pepper fields varied from <1 to 30%. Symptoms on mechanically inoculated indicator hosts, analysis of viral-associated double-stranded RNA, and inclusion body morphology suggested the presence of a tobamovirus. PMMoV was specifically identified by serological testing using ELISA (Agdia, Elkhart, IN). To our knowledge, this is the first definitive identification of PMMoV (2) in Florida, although a prior isolation of the same or a similar virus was made in 1964 and reported as the Samsun latent strain of Tobacco mosaic virus (1). The occurrence of this seedborne virus in an area of intensive commercial pepper production requires careful monitoring to avoid future significant losses.

References: (1) W. H. Greenleaf et al. Phytopathology 54:1367, 1964. (2) C. Wetter. Plant Dis. 68:597, 1984.
Oversummer Survival of Monilinia vaccinii-corymbosi in Relation to Pseudosclerotial Maturity and Soil Surface Environment
Authors: Cox K. D. , Scherm H.
Published: May 2007

Pseudosclerotia (infected, mummified fruit) on the orchard floor act as oversummering and overwintering structures and the sole source of primary inoculum of Monilinia vaccinii-corymbosi, the causal agent of mummy berry disease of blueberry. Survival of pseudosclerotia may be affected by their maturity (degree of stromatization), which can vary considerably at the time of fruit abscission in early summer, and by variations in the soil surface environment. From July through October in 2 years, survival of pseudosclerotia of varying initial maturity (expressed as the proportion of fruit containing mature, melanized entostromata; immature, nonmelanized entostromata; or undifferentiated mycelia) was investigated in the laboratory relative to soil surface temperature and soil moisture content and in the field in relation to shading (full sun versus 50% shade) and ground cover (bare soil versus grass). In the laboratory, oversummer survival, expressed as the percentage of intact pseudosclerotia at the end of the experiment, was higher for cool soil temperatures (approximately 15°C), soils drier than field capacity, and pseudosclerotia containing mature entostromata. In the field, survival was related solely to initial maturity of pseudosclerotia and was highest for pseudosclerotia containing mature entostromata. Shading or grass ground cover did not significantly (P > 0.05) affect oversummer survival, presumably because they did not greatly modify soil temperature or soil moisture. When individual, intact pseudosclerotia were tested for viability using fluorescein diacetate staining, a linear relationship (r = 0.982, P < 0.0001, n = 90) between viable and intact pseudosclerotia was observed, supporting the use of the percentage of intact pseudosclerotia as a measure of oversummer survival.
First Report of Anthracnose of Cagaita Caused by Colletotrichum gloeosporioides in Brazil
Authors: Anjos J. R. N. , Charchar M. J. A.
Published: May 2007

Cagaita (Eugenia dysenterica Mart. Ex DC.), family Myrtaceae, is an important wild perennial fruit crop in Central Brazil (1). Anthracnose symptoms were observed on cagaita leaves in a field in Brasília, Federal District (S 15° 36′ 16″ W 47° 42′ 42″), in August 2000. A fungus was consistently isolated from infected leaves and grown on potato dextrose agar (PDA) and its identification was made by P. F. Cannon of CABI Bioscience as Colletotrichum gloeosporioides (Penzig) Penzig & Sacc. (IMI 384184). Pathogenicity tests were performed on 16 cagaita seedlings by placing mycelial PDA plugs on leaves previously wounded with a sterile needle. Control plants were inoculated with plugs without mycelia. After inoculations, the plants were placed in a dew chamber maintained at 25°C for 72 h and later transferred to the greenhouse. Necrotic leaf spots developed on 100% of the inoculated plants 4 days later. Koch's postulates were fulfilled by consistently reisolating C. gloeosporioides from inoculated plants. Control plants remained symptomless. Inoculations were repeated twice with the same results. To the authors' knowledge, this is the first report of anthracnose caused by C. gloeosporioides of cagaita in Brazil.

Reference: (1) S. P. Almeida et al. 1998. Pages 182–186 in: Cerrado: espécies vegetais úteis. Embrapa Cerrados.
First Report of Exserohilum monoceras on Barnyardgrass in Argentina
Authors: Sisterna M. , Bezus R.
Published: May 2007

Barnyardgrass, Echinochloa crus-galli (L) Beauv., is ranked as the world's third worst weed (2). Punctiform, purplish brown spots were found on leaves and sheaths of 7- to 8-week-old barnyardgrass in a rice crop cultivated in La Plata, Argentina (34° 54′S, 58° 30′W). Individual lesions ranged from 1 to 2 mm diameter. Isolates from the lesions were identified as Exserohilum monoceras (Drechsler) Leonard & Suggs (1) (confirmed by A. Watson, Univ. McGill, Canada). Cultures on potato dextrose agar formed dark green colonies. Conidia were 75 to 135 × 15 to 19 μm, 5- to 7-distoseptate, straight or slightly curved, fusoid, tapering gradually towards the base, pale- to mid-olivaceous brown, with a small protruding plenum-type hilum. Barnyardgrass at the 3-leaf stage was inoculated in a greenhouse with a suspension of 105 conidia per ml of water to confirm the pathogenicity of E. monoceras. Plants were bagged and kept in a humidity chamber for 48 h, at approximately 16°C. After 10 days lesions developed that were similar to those found on infected plants in the field. E. monoceras was reisolated from these lesions. This pathogen is being studied as a biocontrol agent for barnyardgrass in tropical areas (2).

References: (1) J. L. Alcorn. Mycotaxon 7:411, 1978. (2) W. Zhang and A. Watson. Can. J. Bot.75:685, 1997.
Occurrence of Potyviruses on Yam (Dioscorea spp.) in Colombia and First Molecular Characterization of Yam mild mosaic virus
Authors: Dallot S. , Guzmán M. , Bousalem M.
Published: May 2007

A survey to determine the prevalence of potyviruses on yams, Dioscorea alata and D. cayenensis-rotundata, was undertaken in Colombia. Two hundred fifty leaf samples showing mottling symptoms were collected on the Atlantic coast and analyzed by antigen-coated plate enzyme-linked immunosorbent assay with universal potyvirus monoclonal antibodies (Agdia, Elkhart, IN). Potyviruses were detected in 70% (165/235) of the D. alata and in 66% (10/15) of the D. cayenensis-rotundata samples. The presence of Yam mild mosaic virus (YMMV) was indicated in some of these samples by immunocapture reverse-transcriptase polymerase chain reaction performed as previously reported (1). A 600-bp fragment that included the core and C-terminal region of the coat protein gene (CP) and the 3′ untranslated region (3′UTR) was amplified from a D. alata isolate using universal potyvirus primers (1), cloned, and sequenced (EMBL Acc. AJ311725). Comparison with the two previously published YMMV sequences revealed 96.1 and 97.4% identity for the deduced amino acid sequence in the CP region, 74.1 and 83.2% nucleotide identity in the 3′UTR for Papua New Guinea (AB022424 [2]) and Martinique (AJ250336) isolates, respectively. YMMV is known to be widespread on D. alata in Africa and the South Pacific and has been recently identified in the Caribbean (1). To our knowledge, this is the first report of its occurrence in Colombia. A study of its incidence and genetic diversity in South America has been undertaken.

References: (1) M. Bousalem and S. Dallot. Plant Disease 84:200, 2000. (2) S. Fuji et al. Arch Virol. 144:1415, 1999.
First Report on the Occurrence of Bacterial Stripe Organism Acidovorax avenae subsp. avenae in Rice Seeds from Burkina Faso
Authors: Somda I. , Veena M. S. , Mortensen C. N.
Published: May 2007

Breeder rice seeds from Burkina Faso harvesteds in 1999 were tested for Acidovorax avenae subsp. avenae. This pathogen affects rice, maize, sorghum, and other Gramineae. Ten samples of 200 seeds in each sample were tested by the cassette holder method for detection of this bacterium (1). Seedlings were evaluated for symptom development after 14 days at 27 to 30°C and 100% relative humidity under fluorescent light (12 h photoperiod). Bacterial stripe symptoms were observed in seedlings raised from 9 of 10 seed samples tested, and incidence ranged from 5 to 20%. Diseased seedlings showed water-soaked areas on coleoptiles and brown stripes on leaf sheaths and mid-ribs. Twenty-six strains obtained from diseased seedlings were characterized using several criteria. Colonies were small, whitish-grey, raised, entire and translucent on nutrient agar and cream-tan, raised, entire, and did not produce fluorescent pigment on King's medium B. They were Gram negative, oxidase positive and nitrate positive. Variable reactions were recorded for starch hydrolysis; 22 strains reacted positively and 4 negatively. All 26 strains reacted positively in ELISA performed with antiserum against A. avenae subsp. avenae. Results using Biolog GN MicroPlates (Biolog Inc., Hayward, CA computer identification system, Release 4.0) showed all strains to be A. avenae subsp. avenae (sim. 0.709 to 0.802). Hypersensitive reactions on leaves of 2-month-old tobacco plants infiltrated with bacterial suspensions were recorded within 24 h. Strains were tested for pathogenicity by injecting stems of 21-day-old rice plants with bacterial suspensions (approximately 108 CFU/ml). Inoculated seedlings were incubated for 4 to 7 days under humid conditions at 28°C. Inoculated rice plants showed brown stripes and non-inoculated control seedlings remained symptomless. Based on biochemical, serological, and biological characteristics, strains were identified as A. avenae subsp. avenae. This is the first report of A. avenae subsp. avenae, causal agent of bacterial stripe of rice, in Burkina Faso. The common presence of A. avenae subsp. avenae in breeder rice seeds emphasizes the need for control measures to limit further spread to unaffected rice-growing areas and other cereal crops.

Reference: (1) D. D. Shakya et al. Phytopathol. Z. 114:256–259, 1985.