bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of White Rust of Gerbera Caused by Albugo tragopogonis in North America
Authors: Vazquez G. L. , Aquino M. J. , Norman M. T. , Martinez F. A. , Sandoval R. V. , Corona R. M. C. , Strider D. L.
Published: May 2007

In October, 1995, in Villa Guerrero, Mexico, white erumpent sori were detected on the undersurfaces of leaves of a bed of African daisy (Gerbera jamesonii H. Bolus ex J. D. Hook.). The white sori on the undersurfaces of leaves corresponded to chlorotic spots on the upper leaf surfaces. All gerbera plants examined were severely diseased. The gerbera planting was adjacent to a planting of chrysanthemums with symptoms of white rust caused by Puccinia horiana Henn. Symptoms on the leaves of the two crops looked similar, and therefore P. horiana was suspected of causing both diseases. However, when subepidermal sori (pustules) on Gerbera plants were examined microscopically, erumpent chains of round to cylindrical, hyaline to pale yellow sporangiospores borne on short club-shaped sporangiophores were found. The sporangiospores are typical of Albugo tragopogonis (Pers.) S. F. Gray, and it was concluded that the white rust found on gerbera in Villa Guerrero, Mexico, was caused by A. tragopogonis. This disease was reported on gerbera from Australia and New Zealand in 1965 (1) and from Spain in 1977 (2). Other hosts of A. tragopogonis include members in the genera Pericallis (cineraria), Centaurea (dusty miller, basket flower, cornflower, bachelor's-buttons), Ambrosia (common ragweed), Tragopogon (salsify), Antennaria (everlasting, pussytoes), Artemisia (wormwort, mugwort), Cirsium (thistle), Matricaria (false chamomile, pineapple weed), Iva (marshelder), Parthenium (guayule, American feverfew), and Xanthium (common cocklebur, spiny cocklebur). This is the first report of white rust of gerbera caused by A. tragopogonis in North America, and may represent a new disease problem for species of important floral crops in the future.

References: (1) R. F. Doepel. J. Agric. West. Aust. Ser. 4 6:439, 1965. [Rev. Appl. Mycol. 45:80, 1966] (2) H. P. Plate and H. Kruber. Nachrichtenbl. Dtsch. Pflanzen-schutzdienst (Berlin) 29(11):169, 1977. [Rev. Plant Pathol. 57:204, 1978]
First Report of Sclerotinia sclerotiorum on Basil in Canada
Authors: Paulitz T. C.
Published: May 2007

Wilt of basil (Ocimum basilicum L.) branches was observed in home gardens with a past history of Sclerotinia rot in Ste. Anne de Bellevue, Quebec, in the summers of 1994 and 1996. The wilt was accompanied by brown, longitudinal discoloration of the stem, with dark brown to purple-colored advancing margins. No rot or external mycelium was seen on mature woody portions of the wilted branches. Sclerotinia sclerotiorum (Lib). de Bary was isolated from wilted stems on 2% water agar and potato dextrose agar (PDA). Symptoms were reproduced in the greenhouse in 1995 and 1996 by inoculating stems of 10 1-month-old plants with mycelial plugs from 7-day-old PDA cultures. Wilt and necrosis of the outer layer of the inoculated stems were observed in all plants and the pathogen was reisolated from stems. During rainy periods in July 1996, sclerotia (3 to 6 mm diameter) formed on the stems and leaves of some infected plants in gardens. S. sclerotiorum has been reported in the U.S. on greenhouse-grown basil (1), but this is the first report from Canada and from field-grown plants. This disease may be confused with Fusarium wilt on mature plants, because of the dark discoloration of the stem, severe wilting, and lack of white, cottony mycelium.

Reference: (1) G. E. Holcomb and M. J. Reed. Plant Dis. 78:924, 1994.
Delphinella balsameae Tip Blight of Abies lasiocarpa in Vermont
Authors: Merrill W. , Wenner N. G. , Kelley R.
Published: May 2007

In 1996, a windbreak planting of Abies concolor (Gordon & Glend.) Lindl. ex Hildebr. and A. lasiocarpa (Hook.) Nutt. on a Christmas tree farm in Lamoille County, VT, incurred tip blight caused by a Delphinella sp. Although only scattered new shoots of the intermixed A. concolor and nearby A. balsamea (L.) Mill. were killed, more than 75% of the new shoots in the lower 1.8 m of the crowns of A. lasiocarpa were killed. This posed the question, whether the pathogen was the native D. balsameae (A. M. Waterman) E. Müller in E. Müller & Arx or whether the western species, D. abietis (Rostr.) E. Müller in E. Müller had been introduced. Dead 1996 shoots were collected from all species on 15 July. Most ascomata were immature. However, occasional ascomata bore well-developed bitunicate asci with hyaline, uniseptate ascospores averaging 40 × 9 μm, confirming the pathogen was D. balsameae (1). Funk reported this pathogen on A. lasiocarpa in British Columbia without documentation; this is the first record of it attacking this species in eastern North Amer-ica. Although the seed source was unknown, the extreme susceptibility of A. lasiocarpa in comparison to other Abies spp. in the area suggests that caution should be used in planting this species in the Northeast.

Reference: (1) A. M. Waterman. J. Agric. Res. 70:315, 1943.
Incidence of Phoma terrestris, Causal Agent of Red Root Rot, in Corn Roots and Soil in Delaware and on the Eastern Shore of Maryland
Authors: Newby D. L. , Carroll R. B. , Whittington D. P.
Published: May 2007

Red root rot of corn (Zea mays L.) has caused sporadic disease losses in Delmarva during the past 6 years. A survey was made between 21 August and 14 September 1995 in 11 counties in Delaware and on the eastern shore of Maryland to detect Phoma terrestris (E. M. Hans.) in corn roots and in the surrounding soil. Sampling was based on one field per 1,200 ha of corn production in each county. Three root samples and one soil sample were collected from each of 100 corn production fields from corn plants with diseased basal stalk tissue. The presence of P. terrestris was confirmed by cultures from root samples that produced a beet-red color on Watson's sterile wheat straw agar (2). Serial dilutions of soil samples in 0.1% water agar were mixed with unsolidified Watson's basal medium, followed by amendment with a 2-(4-thiazolyl)benzimidazole solution (1). P. terrestris was detected in root samples from 99% of the fields surveyed and from 82% of the soil samples. Soil populations ranged from 0.2 to 200 CFU per g of soil, with a mean of 12.5 CFU. This survey indicated that P. terrestris is widespread in corn production fields in Delaware and on the eastern shore of Maryland. Disease symptoms in surveyed fields indicated that pathogenicity on corn is variable, generally does not result in serious losses, and is related to hybrid susceptibility and growing conditions.

References: (1) B. Sneh et al. Phytopathology 64:275, 1974. (2) R. D. Watson. Plant Dis. Rep. 45:289, 1961.
Fusarium solani on Soybean Roots: Nomenclature of the Causal Agent of Sudden Death Syndrome and Identity and Relevance of F. solani form B
Authors: Roy K. W.
Published: May 2007

Two morphological forms of Fusarium solani pathogenic on soybean, forms A and B, were further characterized and distinguished from other fungi. Questions regarding their identity were addressed. Soybean plants grown in the field and in a growth chamber were inoculated with Fusarium solani form A and F. solani f. sp. phaseoli. F. solani form A incited leaf symptoms typical of sudden death syndrome; F. solani f. sp. phaseoli did not. It was concluded that the two fungi are different and distinguishable on the basis of host specialization and the types of symptoms they incite on soybean. F. solani form A, the causal agent of sudden death syndrome, was designated F. solani (Mart.) Sacc. f. sp. glycines form. nov. Cultural and morphological characteristics of F. solani form B, the cause of seedling disease and root rot of soybean, and Plectosphaerella cucumerina were compared to determine the validity of a report indicating that they were conspecific. Results demonstrated that F. solani form B and P. cucumerina are distinctly different and not conspecific. The relevance of identifying and recognizing the two F. solani forms as separate and distinct members of the F. solani pathogen complex on soybean is discussed.
Russet of Apple Fruit Caused byAureobasidium pullulansandRhodotorula glutinis
Authors: Heidenreich M. C. Matteson , Corral-Garcia M. R. , Momol E. A. , Burr T. J.
Published: May 2007

Russet on apple fruits was caused by inoculation with isolates of Aureobasidium pullulans and Rhodotorula glutinis but not with Metschnikowia pulcherrima or two other unidentified yeasts, YT2 and YT17. Another unidentified yeast, YT5, caused russet in 1 of 2 years. Epiphytic survival of isolates on fruit was measured 3 months after inoculation. All isolates that caused russet survived epiphytically on fruit at harvest. With the exception of M. pulcherrima, nonrusseting isolates were not detected on the fruit at harvest. Conidia, hyphae, and chlamydospores characteristic of A. pullulans were observed in naturally russeted tissues of 14 different apple cultivars and Bartlett and Bosc pear collected from 13 orchards in New York state. A. pullulans was the most commonly isolated microorganism, and all A. pullulans isolates caused apple russet but varied in the severity of russet they caused. Isolates were identified using standard identification schemes. In addition, A. pullulans isolates were compared by generating fingerprints of restriction fragments of a PCR-amplified region of ribosomal DNA consisting of ITS-1, the 5.8S gene, and ITS-2.
Early Season Survey of Pea Viruses in Pakistan and the Detection of Two New Pathotypes of Pea Seedborne Mosaic Potyvirus
Authors: Ali Akhtar , Randles J. W.
Published: May 2007

Sixty-two commercial pea fields or experimental plots located in eight districts of the major pea-growing areas of North West Frontier Province (NWFP) of Pakistan were surveyed for pea viruses in the early winter growing season of 1995. Samples were analyzed by dot-immunobinding assay (DIBA) using antisera to 14 different viruses. Of the 713 plants sampled, 82 were positive for either bean yellow mosaic potyvirus, cucumber mosaic cucumovirus, or pea seedborne mosaic potyvirus (PSbMV), with an average incidence of 9.4, 0.57, and 1.5%, respectively. PSbMV was also detected in 1 to 5% of dry seed from five of the 12 pea varieties tested and in 8 to 20% of seedlings raised from seed of three of these varieties. The infectivities of 12 PSbMV isolates found in the survey of pea varieties from Pakistan were compared using a standard range of pea differential genotypes, and the isolates were classified into four distinct pathotypes. Four isolates were classified as pathotype P-1 and two as P-4. The remainder did not fit into the existing PSbMV pathotype classification and were tentatively placed into two other groups named U-1 and U-2.
Evaluation of Inoculation Methods for Screening Horseradish Cultivars for Resistance toVerticillium dahliae
Authors: Atibalentja N. , Eastburn D. M.
Published: May 2007

Four inoculation methods—colonized oatseed, root dip, infested soil, and set dip—were tested in the greenhouse for their effectiveness in identifying horseradish cultivars that are resistant to Verticillium wilt of horseradish. Examination of the inoculum density-disease relationships derived with each of these methods on susceptible (647A) and resistant (769A) cultivars showed that all were effective, though at varying degrees, in differentiating between susceptible and resistant reactions. Results were more consistent with the root dip method as it produced the largest least-squares means difference in wilt index between the two cultivars, the highest r2, the lowest coefficient of variation, the shortest incubation periods, and the highest incidence of foliar symptoms. Overall, inoculum concentrations accounted for only a small amount of the total variation in wilt index (0.14 ≤ r2≤ 0.73). This observation, in accord with previous reports on other hosts of Verticillium dahliae, would suggest that inoculum densities may not be a good predictor of the severity of Verticillium wilt of horseradish.
Effect of Epiphytic Fungi on Brown Rot Blossom Blight and Latent Infections in Sweet Cherry
Authors: Wittig H. P. P. , Johnson K. B. , Pscheidt J. W.
Published: May 2007

Antagonistic effects of Aureobasidium pullulans, Epicoccum purpurascens, and Gliocladium roseum on establishment of Monilinia fructicola infections on cv. Royal Anne cherry blossoms were assessed in a mist chamber and under field conditions. Conidia of each fungus were applied to blossoms that were subsequently inoculated with conidia of M. fructicola. Mist chamber experiments on forced blossoms demonstrated that incidence of recovery of M. fructicola from blossoms was significantly reduced (P ≤ 0.05) to similar levels when either E. purpurascens or the fungicide benomyl had been applied 24 h prior to inoculation with M. fructicola. In field trials in 1990, 1991, and 1993, application of E. purpurascens reduced blossom blight relative to nontreated blossoms by 47, 58, and 45%, respectively; whereas application of A. pullulans caused reductions of 54, 13, and 47%, respectively. Comparable reductions in blossom blight for the fungicide iprodione were 80, 95, and 98%, respectively. Latent M. fructicola infections were evaluated by dipping immature green cherries in a dilute solution of the herbicide paraquat. Applications of E. purpurascens and A. pullulans to blossoms reduced the number of latent M. fructicola infections in green cherries by 24 and 48%, respectively, in 1990; 57 and 62%, respectively, in 1991; and 19 and 16%, respectively, in 1993. This compares with reductions of 95, 91, and 17% in 1990, 1991, and 1993, respectively, with the fungicide iprodione. E. purpurascens and G. roseum also were recovered from surface-disinfested, paraquat-dipped cherry fruit. Percent recovery of these fungi was significantly (P ≤ 0.05) higher from treatments where they had been applied to blossoms compared with the nontreated control.
Effects of Calcium Salts on Growth, Polygalacturonase Activity, and Infection of Peach Fruit by Monilinia fructicola
Authors: Biggs A. R. , El-Kholi M. M. , El-Neshawy S. , Nickerson R.
Published: May 2007

The effects of several calcium salts on growth, polygalacturonase (PG) activity, and infection of peach fruit by Monilinia fructicola were determined. All salts except calcium formate, calcium pantothenate, and dibasic calcium phosphate reduced growth of M. fructicola on amended potato-dextrose agar (PDA) after 7 days. Minimal growth occurred on PDA amended with calcium propionate. Calcium hydroxide, calcium oxide, calcium silicate, and calcium pyrophosphate reduced growth by approximately 65% compared with the control. Substances that were inhibitory on amended PDA were also inhibitory in potato-dextrose broth (PDB) but varied in effectiveness depending on whether PDB or PDA was used. The correlation between the amount of growth on PDA versus that in PDB was not significant. Fungal PG activity was inhibited by all salts used in this study except dibasic calcium phosphate and calcium tartrate. Greatest inhibition of PG was associated with calcium propionate followed by calcium sulfate, tribasic calcium phosphate, calcium gluconate, and calcium succinate. The activity of calcium salts was not affected by pH. PG activity was correlated with growth on PDA (r s = 0.48, P ≤0.04) but was not correlated with growth in PDB. When inoculum was sprayed on detached fruit, the incidence and severity of brown rot were least on fruit that had been dipped in solutions of calcium propionate or calcium silicate. When inoculum was applied as a localized drop to wounded fruit that had been dipped in a solution containing 1,200 mg of calcium per liter, brown rot severity was least for fruit treated with calcium oxide and calcium hydroxide. For nonwounded fruit and drop inoculations, calcium hydroxide was the most effective in reducing brown rot incidence, and all salts reduced rot severity similarly. There were significant correlations between growth in PDB and disease incidence and severity 4 days after inoculation at both calcium levels (600 and 1,000 mg per liter). Furthermore, disease incidence and severity at both levels of calcium were also correlated significantly with PG activity. Future investigations on brown rot and calcium salts should utilize PDB for in vitro investigations and spray mist inoculations for fruit studies.
Occurrence of Peach Latent Mosaic Viroid (PLMVd) on Plum in Italy
Authors: Faggioli F. , Loreti S. , Barba M.
Published: May 2007

Peach latent mosaic disease was originally described in France in 1976 (1). The disease is often latent in peach trees but may induce mosaic symptoms on leaves, irregularly shaped colorless fruit with cracked sutures and enlarged pits, bud necrosis, and delay in foliation, flowering, and fruit maturity. Recently, the disease has been shown to be caused by peach latent mosaic viroid (PLMVd) (2). PLMVd is distributed worldwide on peach. A recent survey in Italian plum orchards has showed the occurrence of PLMVd in two plum cultivars (Black Diamond and Angeleno) at different geographical locations in central Italy. Plum samples showed bark necrosis and bark split on branches and trunk; moreover, 1-or 2-year-old shoots and stem appeared dwarfed because of shortening of internodes and reduced growth. Budwood from plum samples were grafted, in greenhouse, onto peach GF305 indicator plants. Total nucleic acids (TNA) were then extracted from peach GF 305, or plum leaves, after 6 months of postinoculation. The presence or absence of PLMVd was ascertained by bidirectional polyacrylamide gel electrophoretic (dPAGE) analysis and by spot hybridization assay with PLMVd cRNA probe provided by A. Hadidi. A dPAGE analysis of TNA extracted from grafted peach GF305 showed a band with the same electrophoretic mobility as that of D-168 strain of PLMVd positive control. No bands were observed in healthy peach GF305 or from healthy or diseased plum extracts. The lack of detection of a viroid band from diseased plum samples by dPAGE analysis may be due to low titer of the viroid in infected plum. Molecular hybridization analysis of total nucleic acids with PLMVd cRNA probe, however, showed positive hybridization signals with nucleic acids from grafted peach GF305 or infected plum. Thus, PLMVd or a very closely related viroid infects plum trees. Moreover, on the basis of biological and serological assays, apple chlorotic leaf spot trichovirus, in a sample, and prunus necrotic ring spot ilarvirus, in the second one, were found in association with PLMVd. The same symptoms observed in the two PLMVd-infected plums occurred in other plants infected only by the two viruses (alone or in association). These data suggest that, very probably, PLMVd does not play a specific role in the etiology of the field symptomatology described above. In any case, this is the first report for the occurrence of PLMVd on plum in Italy.

References: (1) J. C. Desvignes. Acta Hortic. 67: 315, 1976. (2) R. Flores and G. Llacer. Acta Hortic. 235:325, 1988.
Seed Treatment with a Fungal or a Bacterial Antagonist for Reducing Corn Damping-off Caused by Species of Pythium and Fusarium
Authors: Mao W. , Lewis J. A. , Hebbar P. K. , Lumsden R. D.
Published: May 2007

Bioassays were conducted under greenhouse conditions to test the efficacy of antagonists applied to corn (Zea mays) seed for protection against seed rot and seedling damping-off at 18 and 25°C in a field soil artificially infested with a combination of Pythium ultimum, P. arrhenomanes, and Fusarium graminearum. Biomass of Gliocladium virens isolates Gl-3 or Gl-21, Trichoderma viride isolate Tv-1, or peat-based slurry of Burkholderia cepacia isolates Bc-B, Bc-T, or Bc-1 was coated individually onto corn seeds in one test, and Gl-3 or Bc-B at four inoculum levels was used in another test. Seed treatments with most of the biocontrol agents, as well as with the fungicide captan, significantly (P ≤ 0.05) increased seedling stand, plant height and fresh weight, and decreased root rot severity compared with untreated seeds in pathogen-infested soil. Coating seeds with the biocontrol fungus G. virens isolate Gl-3 was the most effective treatment, resulting in greater (P ≤ 0.05) seedling stand, plant height, and fresh weight, and lower (P ≤ 0.05) severity of root rot than those parameters from seeds treated with captan or other antagonists at both temperatures. The results from the seeds treated with Gl-3 were similar to those of untreated seeds in noninfested soil. In treatments with Bc-1, Bc-T, Bc-B, or Tv-1, incubation temperature affected plant emergence, root rot severity, plant height, and fresh weight (P ≤ 0.01). Conversely, in seeds coated with Gl-3 or Gl-21, these parameters were similar at both temperatures. The minimum number of propagules needed per corn seed to obtain plant emergence comparable to that from captan-treated seeds was between 104 and 105 CFU for Gl-3 and >108 for Bc-B. When propagules of Gl-3 were applied at a rate >106 CFU per seed, seedling emergence was greater (P ≤ 0.05) than that from captan-treated seeds.
Identification and Geographic Distribution of Serotypes of Potato Virus Y
Authors: Ellis P. , Stace-Smith R. , de Villiers G.
Published: May 2007

From a panel of 10 monoclonal antibodies (MAbs) prepared against specific isolates representing the three recognized strain groups of potato virus Y (PVY), i.e., common (PVYO), tobacco veinal necrosis (PVYN), and stipple streak (PVYC), seven were selected for serotype analysis. These MAbs were tested for reactivity with 52 PVY strains representing all three strain groups from an international collection. Within the PVYN strain group, five serotypes were identified and designated N1 to N5. The PVYO strain group was more diverse, and nine serotypes were defined and designated O1 to O9. Only one serotype, designated C1, was defined) within the PVYC strain group. The same panel of MAbs was used to test 632 PVY samples collected from potato seed certification plots in North America. Although no PVY(N) serotypes were found, all of the PVYO serotypes were identified, and several samples, tentatively assigned to the C1 serotype, were found.
Yield Loss Assessment of Barley Yellow Dwarf Disease on Spring Oat in Illinois
Authors: Bauske Ellen M. , Bissonnette Suzanne M. , Hewings Adrianna D.
Published: May 2007

The quantitative relationship between yield of spring oat cvs. Ogle and Noble and incidence of barley yellow dwarf (BYD) disease caused by barley yellow dwarf virus (BYDV-PAV-IL) was studied. Field plots were infested with Rhopalosiphum padi vectoring BYDV-PAV-IL. A linear critical point regression model was developed that related percentage of maximum yield to BYD incidence, assessed by estimating the percentage of plants with BYD symptoms at Feekes growth stage 10.5 in each plot. The model y = 96.9 - 0.45x (r2 = 0.53) best explained the relationship. Test weight was unaffected by BYD. Although Noble consistently sustained higher disease incidence than Ogle, covariate analysis indicated that the effect of BYD on yield was similar for both cultivars. Studies of random versus focus inoculation of Noble oat, designed to determine the importance of compensation in reducing yield loss associated with BYD, indicated that compensation did not play an important role.
Significance of Thinned Fruit as a Source of the Secondary Inoculum of Monilinia fructicola in California Nectarine Orchards
Authors: Hong Chuanxue , Holtz Brent A. , Morgan David P. , Michailides Themis J.
Published: May 2007

The significance of thinned fruit as a source of secondary inoculum in the spread of brown rot, caused by Monilinia fructicola, under semi-arid weather conditions of the San Joaquin Valley in California, was investigated in seven nectarine orchards in 1995 and 1996. Between 6 and 60% (depending on the orchard) of thinned fruit showed sporulation by M. fructicola. Brown rot was significantly less severe at preharvest (five orchards) and postharvest (one orchard) on fruit harvested from trees in plots from which thinned fruit were completely removed than on those in plots from which thinned fruit were not removed. M. fructicola sporulated more frequently on thinned fruit placed into irrigation trenches than on those left on the dry berms in tree rows. The incidence of preharvest fruit brown rot increased exponentially as the density of thinned fruit increased on the orchard floor. These results suggest that thinned fruit left on the floor of nectarine orchards can be a significant inoculum source of secondary infections. Removal or destruction of thinned fruit should reduce brown rot in nectarine and possibly other stone fruit orchards under semi-arid California conditions.
Diversity and Longevity of the Soybean Debris Mycobiota in a No-Tillage System
Authors: Baird R. E. , Mullinix B. G. , Peery A. B. , Lang M. L.
Published: May 2007

The survival of the mycobiota on pod and stem debris of soybean produced in a no-tillage system with cover crops of alfalfa, canola, rye, or wheat or with no cover was studied during 1994 and 1995. Fiberglass mesh bags containing pods and stems were assayed every 28 to 31 days to determine the isolation frequency of fungi. Over 90% of the 11,906 isolates obtained were members of the Deuteromycotina. The most common genera isolated were Alternaria, Cercos-pora, Colletotrichum, Epicoccum, Fusarium, and Phoma. Alternaria spp. had the greatest isolation frequencies and constituted 40% of the total cultures. Numbers of total fungi (all fungi isolated) on sampling dates in 1994 were similar to the totals in 1995. In May 1994, the mean isolation rates for many of the fungal species were significantly lower (P = 0.05) in several of the cover crops, but no consistent pattern could be determined. Common soybean pathogens isolated included Colletotrichum spp., Diaporthe spp., and Cercospora kikuchii. Fusarium graminearum, which is responsible for several diseases of maize and wheat, was commonly isolated during this study. Of the Diaporthe spp. (anamorph Phomopsis spp.), 87% were identified as D. phaseolorum var. sojae. Colletotrichum spp. were identified as C. truncatum in 85% of the isolates, C. destructivum (teleomorph Glomerella glycines) in 12%, and both species in 3%. Cercospora kikuchii was more commonly isolated from pods than from stem tissue, and Colletotrichum spp. occurred more frequently on stems. Isolation frequencies of Diaporthe spp. were greater in May of both years than in the preceding months. These results show that no-tillage soybean debris harbors numerous fungi pathogenic to soybean, and producers who grow soybeans continuously may find more disease in this crop and lower yields. Fungi that attack crops such as maize and wheat were commonly isolated from soybean debris in both years, and a no-tillage rotation which includes maize or wheat could result in increased disease in these crops. Isolation frequencies of the fungi from cover crops varied with the sampling date, but no consistent patterns could be determined for a particular cover crop or fungal species. This is the first detailed study of survival rates of soybean, maize, and wheat pathogens that overwinter on soybean debris in a no-tillage system.
First Report of Banana Streak Virus Infecting Banana Cultivars (Musa spp.) in Taiwan
Authors: Su Hong-Ji , Hung Ting-Hsuan , Wu Meng-Ling
Published: May 2007

Banana (Musa sapientam L.) is an economically important crop for both export and local consumption in Taiwan. Recently, leaf symptoms characteristic of banana streak disease (1) were found on banana cv. Mysore (AAB group) introduced from Australia in the germ plasm collection of the Taiwan Banana Research Institute. The citrus mealybug (Planococus citri) has been shown to transmit banana streak virus (BSV) but not banana bunchy top virus or cucumber mosaic virus (CMV) (2). When mealybugs were fed on leaves of diseased Mysore banana and transferred to healthy banana cv. Cavendish seedlings in a growth chamber, the latter developed fine chlorotic streaks characteristic of symptoms caused by BSV within 1 to 3 months. Some chlorotic streaks became necrotic. BSV was detected in diseased but not healthy leaves of Mysore and Cavendish bananas by polymerase chain reaction (PCR) with primer pairs of BSV provided by J. E. Thomas of Queensland Department of Primary Industries. Subsequently, fine chlorotic streaks were observed in leaves of Cavendish banana in several fields in southern Taiwan. Some of these diseased plants developed severe leaf necrosis, causing heart rot of spindle leaves characteristic of symptoms caused by CMV. Presence of BSV in these plants was verified by PCR assay. However, CMV was also detected by double antibody sandwich-enzyme-linked immunosorbent assay with a monoclonal antibody to CMV, indicating that these plants were simultaneously infected by both viruses. This is the first report of BSV infecting Musa spp. in Taiwan.

References: (1) B. E. L. Lockhart. Phytopathology 76:995, 1986. (2) B. E. L. Lockhart. 1995 Food & Fertilizer Technol. Center (ASPAC) Tech. Bull. 143. 11 pp.
Citrus Blight Found in Yucatan, Mexico
Authors: Wutscher H. K. , Cervantes H. A. , Derrick K. S.
Published: May 2007

Citrus blight, a serious tree decline problem of unknown cause in humid citrus-growing areas such as Florida and Louisiana, South America, South Africa, and the Caribbean, has never been reported from Mexico. Citrus blight has no reliable visual symptoms, and physical and chemical tests have to be used for diagnosis. We used water injection into the trunk (2), zinc and potassium analysis of the outer trunk wood (3), and an immunological test for specific blight proteins in the leaves (1). Low uptake when water is injected into the trunk, and high zinc and potassium in the wood, compared with healthy trees, are characteristic of citrus blight (3). Water injection tests and wood analysis of four healthy and four declining trees in the Dzan, Yucatan, Mexico, area in August 1995, showed highly significant differences in water uptake (healthy trees 44.3 ml/min, declining trees 1.0 ml/min), little difference in wood zinc (healthy 2.8 μg/g, declining 3.0 μg/g) and 39% more potassium in the wood (healthy 0.147%, declining 0.204%). No leaf protein tests were done at this location. Tests on eight declining and five healthy trees in Seye, Yucatan, Mexico, in June 1996, showed significant (P = 0.01 to 0.05) differences in water uptake (healthy 12.9 ml/min, declining 0.6 ml/min), in wood zinc (healthy 2.0 μg/g, declining 7.0 μg/g) and potassium in the wood (healthy 0.156%, declining 0.251%). Leaf samples from all eight declining trees were positive for blight in a specific protein test (1). The visual symptoms of all declining trees tested were the same as those of blight-affected trees in Florida and Cuba: zinc deficiency symptoms in the leaves, thin foliage, wilt, and sprouting from the trunk and the main branches. The reasons for the lack of earlier reports of citrus blight from Mexico are apparently climatic and rootstock related. Many of Mexico's citrus-producing areas are dry and blight does not occur in dry areas such as the Mediterranean countries and California. Most of Mexico's citrus is grown on sour orange (Citrus aurantium L.) rootstock that is highly resistant to citrus blight, but very susceptible to tristeza virus disease. In response to warnings that tristeza disease might appear in Yucatan, growers planted Valencia orange (C. sinensis (L.) Osbeck) on Cleopatra mandarin (C. reticulata Blanco) rootstock in Dzan and on Volkamer lemon (C. limon (L.) N. L. Burm.) in Seye, both highly susceptible to citrus blight (4). Changes in rootstock to avoid one disease led to problems with another.

References: (1) K. S. Derrick et al. Proc. Fla. State Hortic. Soc. 105:26, 1993. (2) R. F. Lee et al. Plant Dis. 68:511, 1984. (3) H. K. Wutscher and C. J. Hardesty. J. Am. Soc. Hortic. Sci. 104:9, 1979. (4) R. H. Young et al. Proc. Fla. State Hortic. Soc. 91:56, 1978.
Characterization of Pathogenic Races ofFusarium oxysporumf. sp.melonisCausing Fusarium Wilt of Melon in New York
Authors: Zuniga T. L. , Zitter T. A. , Gordon T. R. , Schroeder D. T. , Okamoto D.
Published: May 2007

Forty-six isolates of Fusarium oxysporum f. sp. melonis obtained from soil samples throughout melon-producing areas in New York State were identified on the basis of pathogenicity and colony morphology. Physiological races 1 and 2 were identified by their reaction on a set of differential melon cultivars. Race 1 was widely distributed, occurring in six of the seven New York counties surveyed. Twenty-seven of the 28 race 1 isolates were associated with vegetative compatibility group (VCG) 0134, whereas one was incompatible with all known VCGs of F. oxysporum f. sp. melonis. Twelve out of 18 race 2 isolates were associated with VCG 0131, and occurred in four counties in eastern and western New York. Five isolates of race 2, associated with VCG 0130, were recovered from a farm in Washington County, as was a single race 2 isolate which was incompatible with all known VCGs of F. oxysporum f. sp. melonis. Restriction fragment length polymorphisms in the nuclear DNA revealed variability among the isolates examined, but race 1/VCG 0134 isolates from New York and Maryland were identical or nearly so, as were race 2/VCG 0131 isolates from the two states. These findings suggest a close relationship between the populations of F. oxysporum f. sp. melonis in New York and Maryland. Race 2 isolates were more virulent than race 1 isolates, based on the number of days to first symptoms and death of melon seedlings.
Inoculum Density and Expression of Major Gene Resistance to Fusiform Rust Disease in Loblolly Pine
Authors: Kuhlman E. G. , Amerson H. V. , Jordan A. P. , Pepper W. D.
Published: May 2007

Inoculum densities of 25 × 103 to 200 × 103 per ml of basidiospores from single aeciospore isolates avirulent or virulent to the Fr1 (fusiform resistance-1) gene were used to inoculate a control-pollinated loblolly pine family heterozygous for this gene. With two avirulent isolates, the regression curve of gall frequency 9 months after inoculation went from 26 to 50% as inoculum density increased to 100 × 103 spores. The regression curve flattened at higher inoculum densities. With two virulent isolates, gall frequency increased from 47% to a plateau at 97% as spore density increased. A double-blind element of the study correlated the occurrence of the genetic marker (RAPD marker J7-485A) for Fr1 resistance in haploid megagametophyte tissuend the presence or absence of galls on seedlings after artificial inoculations. With avirulent isolates at the two higher densities of 100 × 103 and 200 × 103, marker presence-absence and phenotypic assessments of gall presence-absence agreed for 95% of the seedlings. At the 50 ×103 level, marker-phenotype agreed for 86% of the seedlings. The increased marker-phenotype association resulted from a reduction or elimination of disease escapes as Fr1 resistance remained stable even at higher spore densities. The double-blind study indicates that resistant individuals can be identified from the megagametophyte tissue of germinating seedlings. With virulent isolates, marker and disease phenotype did not correlate, even at the lowest inoculum density. The virulent isolates appear to be homozygous for virulence because infection of marker-positive resistant seedlings equaled or exceeded that of marker-negative susceptible seedlings at the lowest inoculum density.
Effect of Sprinkler Irrigation on Bacterial Soft Rot and Yield of Broccoli
Authors: Ludy R. L. , Powelson M. L. , Hemphill D. D.
Published: May 2007

The effect of amount of applied water under two irrigation frequencies (once versus three times per week) on the incidence of bacterial soft rot, caused by Erwinia carotovora subsp. carotovora, and yield of broccoli was investigated in field studies conducted in 1987 and 1988. At head initiation, the amount of applied water was varied by utilizing a line source irrigation system. Incidence of soft rot was higher in the OSU breeding line 86-3 plots, followed by cv. Citation and then cv. Gem. Soft rot was not consistently affected by amount of applied water. Differences in amount of disease were apparent, however, between the separate irrigation frequency studies in 1988; disease incidence more than doubled under the high- compared with the low-frequency irrigation. Further studies on the effects of frequency and timing of sprinkler irrigation on soft rot and yield of Gem broccoli were undertaken in 1993 and 1994. Six sprinkler irrigation regimes, a factorial combination of frequency (irrigation every 2, 4, or 8 days) and timing (morning or evening), were established. Total water applied did not differ by treatment. Incidence of soft rot was negligible at the first harvest in both years. At the last harvest, the incidence of soft rot was significantly reduced, from 22 to 10% in 1993 and from 30 to 15% in 1994, by the change in frequency of irrigation from 2 to 8 days. In contrast, timing of irrigation had no effect on disease incidence. Yield of broccoli was not affected by either frequency or timing of irrigation.
Foliar Resistance to Phytophthora palmivora as an Indicator of Pod Resistance in Theobroma cacao
Authors: Iwaro A. D. , Sreenivasan T. N. , Umaharan P.
Published: May 2007

Resistance to Phytophthora palmivora was assessed in leaves and pods of 12 diverse cacao genotypes at the penetration and post-penetration stages of infection to determine the relationship of resistance between stages and sites of infection. Penetration resistance was based on the frequency of lesions, whereas lesion size was used as a measure of post-penetration resistance. We observed significant clonal differences for leaf and pod resistance at the two stages of infection. A poor correlation between resistance at the penetration and post-penetration stages in both leaves and pods indicated that these two forms of resistance are independent and governed by different mechanisms. Correlation between resistance of leaves and pods was not significant at the penetration stage, whereas that of post-penetration resistance was positive and significant. This shows that internal or tissue resistance is common between leaf and pod and indicates that leaf resistance at the post-penetration stage of infection could be used to predict pod resistance; however, resistance of leaves at the penetration stage cannot be used to predict penetration resistance in pods. A high positive correlation obtained between attached leaves and pods with their detached counterparts showed that detached organs can be used for the prediction of resistance in attached leaves and pods.
Effect of Dew Period and Temperature on the Ability of Exserohilum monoceras to Cause Seedling Mortality of Echinochloa Species
Authors: Zhang W. M. , Watson A. K.
Published: May 2007

In greenhouse and controlled environment experiments, disease development and mortality of Echinochloa crus-galli, E. colona, and E. glabrescens caused by Exserohilum monoceras were affected by duration, frequency, and timing of dew period, as well as by dew-period temperature and post-dew temperature. When adequate dew was provided, 100% mortality occurred for all three Echinochloa spp. over the broad dew-period temperature range of 20 to 30°C. The effect of post-dew temperature on disease development varied with the initial dew period. The minimum dew period to achieve 100% mortality was 16 h for E. colona, 12 h for E. crus-galli, and 8 h for E. glabrescens. Increasing dew period enlarged the range of temperature for maximum efficacy, whereas the use of optimum dew-period temperature decreased the dew period requirement. Delaying the initiation of the dew period by 24 h did not adversely affect disease development. Increased disease development occurred for inoculated seedlings treated with repetitive dew periods of shorter duration than the optimal period. These findings characterize one of the epidemiological requirements, i.e., dew requirement, needed to assess the potential of E. monoceras for the control of Echinochloa spp. in rice.
Gazaniaspp.: A New Host of Lettuce Mosaic Potyvirus, and a Potential Inoculum Source for Recent Lettuce Mosaic Outbreaks in the Salinas Valley of California
Authors: Zerbini Francisco Murilo , Koike Steven T. , Gilbertson Robert L.
Published: May 2007

Lettuce mosaic potyvirus (LMV) outbreaks in the Salinas Valley of California have increased in recent years despite a comprehensive lettuce mosaic management program. In a previous study, it was established that new serologically and/or genetically distinct LMV strains were not responsible for these outbreaks. Therefore, the role of alternate hosts was investigated. Here we provide evidence that the ornamental plant, Gazania spp., is an alternate host of LMV. A number of lines of evidence were used to establish that gazanias were infected by LMV, including indirect enzyme-linked immunosorbent assay, dot blot hybridization with an LMV coat protein (CP) probe, and sap- and aphid-transmission of LMV from gazania to lettuce and Nicotiana benthamiana. Additionally, an LMV CP fragment was amplified from an infected gazania plant by reverse transcription-polymerase chain reaction, and the nucleotide sequence of this fragment was 99% identical to the CP sequence of an LMV isolate from the Salinas Valley. We further show that LMV-infected gazanias are widely distributed in the Salinas Valley, and are present near areas where LMV outbreaks have occurred. Field experiments demonstrated that LMV could be transmitted from infected gazania to lettuce. LMV-infected gazanias also were found in local nurseries, suggesting that infection of gazania with LMV had occurred prior to planting in the Salinas Valley (i.e., lettuce was not serving as the source of inoculum for infection of gazania in the Salinas Valley). These results establish that gazania is an alternate host of LMV, and suggest that gazanias may be a primary inoculum source for recent lettuce mosaic outbreaks in the Salinas Valley.
Cloning and Sequencing of the Coat Protein Gene of a New Isolate of Citrus Tristeza Virus from Mexico
Authors: Cepeda-Nieto A. C. , Barrera-Saldaña H. A.
Published: May 2007

Citrus tristeza virus (CTV) causes one of the most important citrus diseases. CTV strains cause a wide range of symptoms in infected citrus worldwide. Although it has not yet affected Mexico's citrus industry, CTV constitutes a threat since one of its most efficient vectors, Toxoptera citricida, is migrating north from South America and is now in the Caribbean region. Efforts have been made to prevent spread of the virus, through early detection with serological methods (3). Use of the polymerase chain reaction (PCR), not yet a competitor of immunological methods in field diagnosis of CTV, offers a quick detection alternative. As a first step toward using PCR in early diagnosis and characterization of CTV, we searched for the CTV coat protein gene in experimentally infected leaves of Citrus aurantifolia grown at a government research station (INIFAP) at General Terán, NL. Researchers at General Terán had collected the isolates during a random sampling of orange orchards in the Gulf state of Veracruz. The original orange trees had no apparent symptoms and had been examined as a preventive measure. Several of the original orange trees were CTV positive in their initial tests with polyclonal antibody and in subsequent tests with CTV-specific monoclonal antibody MCA-13. Characteristic CTV-like particles had also been observed by electron microscopy. The only symptom induced in indicator plants was yellowing of the leaf veins. In our laboratory, reverse transcription of RNA from one of the indicator plants, coupled with PCR (RT-PCR) (1), was used to clone and sequence one of the isolates to confirm the CTV identification and establish PCR methods. Oligonucleotide primers were derived from published sequences, but unique restriction enzyme sites (EcoRI and XbaI) were added to their 5′ ends to facilitate cloning. To exclude artifacts, nucleotide sequences were obtained from both strands after cloning in M13 vectors. Although the expected RT-PCR product of 700 bp was obtained, an unexpected EcoRI site was found at position 678 of the coat protein gene. A phenylalanine residue was found at position 124, as in severe strains of CTV from various regions of the world (2). Similarities between our CT sequence (U32116) and those of other GenBank accessions are as follows: 91.17% for M76485; 90.14% for L12175; and 89.32% for S67800.

References: (1) M. D. Jones and N. S. Foulkes. Nucleic Acids Res. 17:8387, 1989. (2) H. Pappu et al. Proc. Natl. Acad. Sci. USA. 90:3641, 1993. (3) C. Vela et al. J. Gen. Virol. 67:91, 1986.
First Report of Colletotrichum capsici on Bell Pepper in Mississippi
Authors: Roy K. W. , Killebrew J. F. , Ratnayake S.
Published: May 2007

Anthracnose (ripe rot) of bell pepper (Capsicum annuum L.), caused by Colletotrichum capsici (Syd.) E. J. Butler & Bisby, was observed in seven home gardens in Copiah, DeSoto, and Oktibbeha counties in Mississippi in 1994. Falcate conidia measuring 20.5 × 4.0 μm were produced on lesions of fruits in moist chambers. Conidial size and other distinguishing features agreed with the description of C. capsici (1). Pure cultures of the pathogen were obtained by aseptic transfer of conidia to agar. Occurrence of symptomatic fruits in gardens ranged from 15% in Starkville to 3% near Crystal Springs, MS, but nine of the gardens inspected had no fruit rot. The most severe disease occurred on ripening fruits. Lesions similar to those observed were produced by inoculating sterilized toothpick tips infested with C. capsici into fruits, followed by incubation in a moist chamber. Koch's postulates were completed by reisolation of the fungus from inoculated fruits.

Reference: (1) J. E. M. Mordue. 1971. No. 317 in: Descriptions of Pathogenic Fungi and Bacteria. Commonw. Mycol. Inst., Kew, England.
Detection of Both Subgroups I and II of Cucumber Mosaic Cucumovirus and Their Satellite RNAs on Pepper in Argentina
Authors: Atencio F. A. , Gracia O. , Mendoza E. E. A. , Zandomeni R. , Grau O.
Published: May 2007

Pepper plants (Capsicum annuum L.) showing stunting, mild to severe mosaic, leaf narrowing and deformation, prominent veins, fruit atrophy or malformation, and necrotic patterns on leaves and fruits were collected from commercial and experimental farms from seven districts in the central western neighboring provinces of Mendoza and San Juan. Cucumber mosaic cucumovirus (CMV) was identified directly from field samples from crude RNA extracts by reverse transcription-polymerase chain reaction (RT-PCR) (1). The PCR-amplified products were analyzed by restriction enzyme digestion with PvuII and VspI to distinguish the CMV subgroups. Serological assays (double immunodiffusion tests and indirect triple antibody sandwich enzyme-linked immunosorbent assay) with subgroup-specific monoclonal and polyclonal antisera also differentiated between the subgroups, although with lower sensitivity than found with PCR. Both subgroups I and II were found, no mixed infections were detected, and subgroup membership was related to geographical distribution: subgroup-I samples were detected in San Juan sites (north), and samples collected from the southern area (Mendoza) were of subgroup II. Some samples were sap-transmitted and passed repeatedly through tobacco and pepper. Satellite RNAs (satRNAs) were detected from total RNA extracts by RT-PCR with specific primers (5′-end oligonucleotide: 5′GGGTTATATCTGCGTGAG3′ and 5′CACGGAGATCAGCATAGC3′ as 3′-end primer). One satRNA isolate from each area was amplified and cloned. Three and five clones, respectively, were sequenced, obtaining 313/315 nucleotide and 334 nucleotide consensus sequences that appear to be similar (98.2 and 98.9%, respectively) to CMV-Y satRNA. This is the first report of CMV subgrouping and detection of CMV satRNAs in Argentina.

Reference: (1) H. Rizos et al. J. Gen. Virol. 73:2099, 1992.