Take-all or nothing.

Take-all disease of Poaceae is caused by Gaeumannomyces graminis (Magnaporthaceae). Four varieties are recognised in G. graminis based on ascospore size, hyphopodial morphology and host preference. The aim of the present study was to clarify boundaries among species and varieties in Gaeumannomyces by combining morphology and multi-locus phylogenetic analyses based on partial gene sequences of ITS, LSU, tef1 and rpb1. Two new genera, Falciphoriella and Gaeumannomycella were subsequently introduced in Magnaporthaceae. The resulting phylogeny revealed several cryptic species previously overlooked within Gaeumannomyces. Isolates of Gaeumannomyces were distributed in four main clades, from which 19 species could be delimited, 12 of which were new to science. Our results show that the former varieties Gaeumannomyces graminis var. avenae and Gaeumannomyces graminis var. tritici represent species phylogenetically distinct from G. graminis, for which the new combinations G. avenae and G. tritici are introduced. Based on molecular data, morphology and host preferences, Gaeumannomyces graminis var. maydis is proposed as a synonym of G. radicicola. Furthermore, an epitype for Gaeumannomyces graminis var. avenae was designated to help stabilise the application of that name.

Serenomyces associated with palms in southeastern USA: isolation, culture storage and genetic variation.

Serenomyces is a genus belonging to the family Phaeochoraceae, which is known to occur only in association with the plant family Arecaceae (palms). It is presumed to be one of the causes of a leaf disease referred to as either rachis blight or petiole blight, depending on the palm species affected. The fungus is not readily observed, with few reports in the literature; it cannot be readily isolated from tissue, with only one known instance of it being cultured on artificial media and has no DNA sequences deposited in GenBank. Over an 8 y period, leaves symptomatic for rachis or petiole blight were obtained from Florida and South Carolina, USA. The fungus was induced to produce ascospores, and single-spore isolates were obtained in culture and, in some instances, induced to produce ascospores in culture. Based on ascospores size and ITS sequencing, Serenomyces from Phoenix canariensis and P. dactylifera form one group, Serenomyces from Thrinax radiata form a second group and Serenomyces from Sabal palmetto form a third. All three groups are most similar morphologically to Serenomyces phoenicis. Due to the observed instability of Serenomyces in culture, we have suggestions regarding the storage of this fungus.

First Report of Fusarium oxysporum f. sp. palmarum in Texas Causing Fusarium Wilt of Washingtonia robusta.

Fusarium wilt of palms occurs worldwide, caused by different Fusarium oxysporum ff. spp. including F. oxysporum f. sp. elaeidis, F. oxysporum f. sp. canariensis, and F. oxysporum f. sp. albedinis (3). Prior to 2010, F. oxysporum f. sp. canariensis was the only palm infecting species known to occur in the United States. In 2010, isolates of F. oxysporum were reported from dying Syagrus romanzoffiana and Washingtonia robusta in Florida. Based on morphological and molecular data, as well as the unique host species affected by the pathogen, this fungus was determined to be a new forma specialis of F. oxysporum, designated f. sp. palmarum (1). The pathogen infects foliar tissue, causing complete necrosis of the crown and leading to tree death within 2 to 3 months. In June 2012, the Texas Plant Disease Diagnostic Laboratory (TPDDL) received a plant sample from a dying W. robusta palm, exhibiting reddish-brown stripes on the petiole with chlorotic and necrotic leaves, from an established palm in the landscape from Harris County, Texas. Fungal cultures were obtained from symptomatic foliar tissue and identified as F. oxysporum based on morphology. Microconidia were oval to reniform, 1- to 2-septate, measuring 5 to 18 × 2.5 to 5 µm. Phialides were short with microconidia produced in false heads. Macroconidia were curved and slender with a foot-shaped basal cell, usually 3-septate, and 22 to 37 × 2.5 to 5 µm. Chlamydospores were roundish and ranged from 7 to 13 µm in diameter. Fungal colonies had white to purple mycelia when grown on potato dextrose agar. DNA from a single spore culture was extracted, amplified by PCR using primers corresponding to a segment of the translation elongation factor 1α (EF-1α) gene, and the PCR product sequenced (2). Using the sequence alignment tool (BLASTn) in GenBank, the TPDDL's sequence (GenBank Accession No. KC897693) was aligned with EF-1α regions from F. oxysporum f. sp. palmarum isolates previously entered into the database ([1]; accessions GQ154455[=NRRL53544] and GQ154456[=NRRL46589]), revealing 100% homology between the isolates. Based on host source and sequence similarity, the fungus was tentatively identified as F. oxysporum f. sp. palmarum. Pathogenicity tests were performed on three leaf seedlings of W. robusta and W. filifera. Fifteen plants of each species were inoculated with the suspect isolate (designated KB2012) and 10 control plants were mock-inoculated as described by (1). Plants were grown in a greenhouse for 8 weeks post-inoculation. During this time, 83% of inoculated plants developed foliar lesions and died or severely declined, and all control plants remained healthy. F. oxysporum was recovered in culture from 100% of the symptomatic plants. DNA was extracted from fungal cultures, and EF-1α was amplified by PCR and sequenced, as described above. The amplicon was determined to share 100% homology with known F. oxysporum f. sp. palmarum isolates, confirming this fungus as the cause of disease in W. robusta. This is the first report of this pathogen in Texas, as well as the first report outside of Florida. This is also the first documentation of W. filifera as a host of this pathogen. References: (1) M. L. Elliott et al. Plant Dis. 94:31, 2010. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) G. W. Simone. Pages 17-19 in: Compendium of Ornamental Palm Diseases and Disorders, M. L. Elliott et al., eds. The American Phytopathological Society, St. Paul, MN, 2004.

First Report of Fusarium Wilt Caused by Fusarium oxysporum f. sp. palmarum on Canary Island Date Palm in Florida.

Canary Island date palm (Phoenix canariensis Chabaud) is an ornamental grown throughout the world. In the fall of 2009, a single plant of this species was observed with Fusarium wilt symptoms at a commercial property in Orlando, FL. Individual leaves had chlorotic or necrotic leaflets on one side of the leaf blade and a reddish brown stripe along the petiole and rachis. Petiole cross-sections exhibited discolored vascular tissue. Fusarium oxysporum was isolated from this tissue, with typical characteristics of macroconidia in pale orange sporodochia, microconidia in false heads on short monophialides, and chlamydospores (3). All colonies on potato dextrose agar had pale pinkish-salmon-colored mycelia. Macroconidia were mostly 3-septate, slightly curved, and ranged from 4.1 to 4.6 × 39.5 to 43.7 µm. Microconidia were unicellular, oval to reniform, and ranged from 3.1 to 3.3 × 7.1 to 7.5 µm. Single-spore isolates (PLM-509 and PLM-510A) were selected for molecular characterization, with PCR conducted using ef1 and ef2 primers (2). Resulting products were sequenced and queried for similarity against the NCBI and the FUSARIUM-ID databases (2) using BLAST. In both databases, the isolates did not match F. oxysporum f. sp. canariensis. Rather, the isolates matched F. oxysporum f. sp. palmarum, and of particular interest, were NRRL 46589 (GenBank Accession No. GQ154456) and NRRL 46592 (GenBank Accession No. GQ154468), which the isolates matched with 100% similarity. These NRRL isolates were from the same commercial property but different locations on the property as this Canary Island date palm (1). Prior to this identification, F. oxysporum f. sp. palmarum had only been associated with Fusarium wilt of queen palm (Syagrus romanzoffiana) and Mexican fan palm (Washingtonia robusta) in Florida (1). Furthermore, in September 2008, two of four Mexican fan palms in a concrete planter (not in the ground) at the same location as the diseased Canary Island date palm (in the ground) were symptomatic for Fusarium wilt and the pathogen was confirmed as F. oxysporum f. sp. palmarum. Therefore, pathogenicity studies were conducted on three-leaf seedlings of P. canariensis and W. robusta using PLM-510A. There were five replicate palms per isolate and control treatment, and they were inoculated by the same methodology used previously for seedlings (1). After 3 months, all inoculated W. robusta were dead and one of five inoculated P. canariensis was dead. After 6 months, three more P. canariensis had died for a total of four of five inoculated palms. The pathogen was reisolated from diseased palms of both species. All control palms remained healthy. The sequence for PLM-510A has been deposited in the NCBI database (GenBank Accession No. HQ727681). To our knowledge, this is the first report of Fusarium wilt of Canary Island date palm caused by F. oxysporum f. sp. palmarum. References: (1) M. L. Elliott et al. Plant Dis. 94:31, 2010. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

First Report of Fusarium Wilt Caused by Fusarium oxysporum f. sp. canariensis on Canary Island Date Palm in Texas and South Carolina.

Canary Island date palm (Phoenix canariensis) is native to the Canary Islands and widely grown throughout the world as an ornamental. At a home site in Austin, TX in May 2008 and a commercial site near Charleston, SC in December 2009, declining Canary Island date palms were observed. Symptoms included individual leaves with chlorotic or necrotic leaflets on one side of the leaf blade (one-sided wilt or death) and a distinct reddish brown stripe along the petiole and rachis. Cross-sections through the petiole or rachis exhibited discoloration of internal tissue. Fusarium oxysporum was isolated from the internal petiole or rachis tissue of each palm sample onto one-quarter-strength potato dextrose agar (PDA). Typical macroconidia in pale orange sporodochia, microconidia in false heads on short monophialides, and chlamydospores were observed (2). Macroconidia were mostly 3-septate, slightly curved, and ranged from 3.8 to 4.2 × 42.9 to 46.5 µm. Microconidia were single cell, oval to reniform, and ranged from 2.5 to 2.9 × 7.2 to 7.8 µm. Single-spore isolates grown on full-strength PDA (12-h light and 26°C) produced abundant white-to-pale lavender mycelia with a purple pigment in the agar. One isolate from each location (PLM-385B from Texas and PLM-511A from South Carolina) was selected for pathogenicity tests and molecular characterization. The translation elongation factor 1-α gene (EF-1α) was amplified in each isolate by PCR using the ef1 and ef2 primers (1). Products were sequenced and queried for similarity against the NCBI database and the FUSARIUM-ID database ( http://isolate.fusariumdb.org/index.php ) (1) using the BLAST search tool. In both databases, both isolates matched F. oxysporum f. sp. canariensis strain NRRL 26035 (GenBank Accession No. AF008485; FD_01211) at 100% sequence similarity. Sequences for PLM-385B and PLM-511A have been deposited in the NCBI database (GenBank Accession Nos. HM591537 and HM591538, respectively). Pathogenicity of these two isolates was tested on three-leaf Canary Island date palm seedlings. There were five replicate palms per isolate and control treatment. All potting mix was shaken from the roots and three groups of five seedlings were placed in small buckets. Twenty-five milliliters of a 106 conidia ml-1 suspension was pipetted down among the leaf bases and the excess drained onto the roots. Control palms received sterile water. Seedlings were covered with plastic for 48 h and then transplanted into separate growing containers. Ten weeks after inoculation, initial symptoms of a leaf wilt (off-color and folded over) were observed on some of the inoculated palms. After 4 months, all palms inoculated with PLM-511A were dead and three of the five palms inoculated with PLM-385B were dead. The pathogen was reisolated from diseased palms. All five control palms remained healthy. While the symptomatic palm in Texas had been in the home site approximately 2 years, which implied the palm could have been already infected when transplanted, the palm in South Carolina had been planted in 1990. To our knowledge, this is the first report of Fusarium wilt of Canary Island date palm in Texas and South Carolina. Previously in the United States, the disease had only been noted in California, Florida, and Nevada. References: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

First Report of Bud Rot Caused by Phytophthora palmivora on African Oil Palm in Colombia.

A bud rot disease, referred to as "pudricion del cogollo" or PC (for its name in Spanish), is a major disease of oil palm in four production areas of Colombia. Even though the disease has been studied for more than 40 years in Central and South America, the causal agent remained unknown (1). Infection first develops in the palm heart (cogollo) above the meristematic zone. Initial external symptoms appear as necrotic lesions on the sides of the spear leaf (youngest, unexpanded leaf) and the sizes of the lesions remain static as tissues emerge, expand, and mature. Under favorable environmental conditions (temperature around 26°C and relative humidity above 80%), further rotting of the heart eventually destroys the bud. A baiting technique with papaya and cocoa fruits was successfully used to trap the causal agent from symptomatic spear leaf tissue collected from the provinces of Nariño and Santander (2), where the disease is severe. Small, triangular-shaped pieces were removed from healthy fruits that had been surface sterilized, and a corresponding piece of diseased oil palm tissue was inserted into the hole and sealed with the removed fruit tissue. The whole fruit was wrapped with plastic and incubated at 25°C. Once the fruit traps showed initial necrotic symptoms, fruit tissue from the advancing point of the lesions was plated on Phytophthora-selective media. Four isolates of Phytophtora palmivora, all A2 mating type, were obtained during this study and each presented similar white and depressed mycelium when grown on oatmeal agar (OMA) medium. Papillated, ellipsoidal sporangia with short pedicels had an average size of 37.1 (breadth) × 52.8 µm (length). Chlamydospores averaged 35.1 µm in diameter and were similar to those observed in diseased palm tissue. DNA from the Phytophthora isolates was used as a template for PCR using ITS1/ITS4 primers. BLASTn analysis of the ITS sequences (GenBank Accession No. GQ398157) showed 99.9% homology with P. palmivora. The sequences of the four isolates were identical. For pathogenicity testing, cultures were grown on OMA. Two milliliters of distilled water containing 40,000 sporangia were injected into the base of the spear leaf of 105 nursery palms; the same number of palms was injected with 2 ml of distillated water as controls. Initial PC symptoms were observed 3 to 4 days after inoculation on 85% of inoculated palms and 15% of these palms developed typical bud rot symptoms under favorable conditions. No symptoms were observed on the controls. The presence of Phytophthora was confirmed by light microscopy and P. palmivora was reisolated from symptomatic palms with the fruit-baiting technique. The presence of Phytophthora in the four Colombian growing areas was also confirmed using Agdia (Elkhart, IN) immunostrips followed by DNA extraction from the Immunostrip wick and ITS sequencing to confirm the species. To our knowledge, this is the first report of P. palmivora causing PC on oil palm in Colombia. References: (1) H. de Franqueville. Exp. Agric. 39:225, 2003. (2) G. Sarria et al. Rev. Palmas, Colombia. 29(3):31, 2008.

Fusarium oxysporum f. sp. palmarum, a Novel Forma Specialis Causing a Lethal Disease of Syagrus romanzoffiana and Washingtonia robusta in Florida.

A new disease of Syagrus romanzoffiana (queen palm) and Washingtonia robusta (Mexican fan palm) has spread across the southern half of Florida during the past 5 years. The initial foliar symptom is a one-sided chlorosis or necrosis of older leaf blades, with a distinct reddish-brown stripe along the petiole and rachis and an associated discoloration of internal tissue. Within 2 to 3 months after onset of symptoms, the entire canopy becomes desiccated and necrotic but the leaves do not droop or hang down around the trunk. Based on pathogenicity and morphological and molecular characterization, the etiological agent has been identified as a new forma specialis of Fusarium oxysporum, designated f. sp. palmarum. Sequence analysis of a portion of the translation elongation factor 1-α gene (EF-1α) separated 27 representative isolates into two EF-1α groups, which differed by two transition mutations. Members of both EF-1α groups are pathogenic on both species of palm. A phylogenetic analysis inferred from partial EF-1α sequences from a genetically diverse set of F. oxysporum isolates, including three other formae speciales pathogenic on palm (i.e., f. sp. albedinis, f. sp. canariensis, and f. sp. elaeidis), suggested that f. sp. palmarum and f. sp. albedinis may be more closely related to one another than either is to the two other palm pathogens.

Survival, growth and pathogenicity of Gaeumannomyces graminis var. graminis with different methods of long-term storage.

The fungal plant pathogen Gaeumannomyces graminis var. graminis was preserved with 12 different storage methods. Five strains, each with unique morphological and pathological characteristics, were used for comparison of the methods. The storage treatments included potato-dextrose agar slants, with or without mineral oil, stored at either 4 C, 28 C or ambient temperature; colonized agar plugs placed in glycerol solution at either -75 C or -20 C; colonized agar plugs placed in sterile deionized water at either 4 C or ambient temperature; and mycelial growth on intact or precut pieces of filter paper, desiccated and stored at ambient temperature. Survival was evaluated at 6, 12, 24, 36, 48 and 120 mo. The three best treatments for survival were PDA slants, with or without mineral oil, and colonized agar plugs stored in water, all at ambient temperature. All five fungal strains were recovered from all four replicates at each sampling date for agar plugs stored in water at ambient temperature. The worst treatments were agar slants and agar plugs in water stored at 4 C and agar plugs stored in glycerol at -20 C. Morphological characteristics were not affected by storage treatments. In general, there were minimal or no effects on growth and pathogenicity for all strains for all storage treatments with survival. Colonized agar plugs stored in water at ambient temperature provides an economical storage method (materials and labor) that does not need an electrical power for long-term maintenance.

First Report of Bipolaris sacchari Causing Leaf Spot on Lygodium japonicum and L. microphyllum in Florida.

Lygodium japonicum (Thunb.) Sw. (Japanese climbing fern) and L. microphyllum (Cav.) R.Br. (Old World climbing fern) are invasive, noxious weeds in Florida. During 2001, L. japonicum sporelings were collected from natural sites in Hamilton, Highland, and Madison counties and transported to Broward County (Fort Lauderdale) for research use. During February 2002, leaf spots were observed on pinnules (leaflets) of these containerized plants growing in a shadehouse. A fungus with Bipolaris-like spores was isolated from affected pinnules and purified and stored for future evaluation. In early 2005, the fungus was grown on 1.5% water agar, with sterile, wheat straw pieces embedded in the agar surface, at 26°C and a 12-h photoperiod using cool-white fluorescent and Verilum full-spectrum bulbs. Conidia were 80.5 ± 14.5 µm (range 53.2 to 123.4 µm) × 15.1 ± 1.6 µm (range 12.1 to 19.4 µm), pale brown, slightly curved, narrowly ellipsoid, without a protuberant hilum, distoseptate (8 ± 1, range 6 to 10), and germinated from both polar cells. Conidiophores were septate and smooth. Conidiogenous nodes were smooth. On the basis of these characteristics, the fungus was identified as Bipolaris sacchari (E. Butler) Shoem. (1,2). Pathogenicity toward L. japonicum and L. microphyllum was determined using conidia produced on potato dextrose agar at 26°C and a 12-h photoperiod. A 1 × 106 conidia ml-1 suspension was sprayed until runoff on healthy plants grown in 450-ml containers. Control plants were sprayed with sterile water. There were four replicate plants per treatment. Plants were covered with plastic bags to maintain high humidity and placed in a growth chamber with a 12-h photoperiod at 28°C (light cycle) and 22°C (dark cycle). Bags were removed after 72 h, and small (1 to 2 mm), water-soaked spots were evident throughout the plant canopy on both Lygodium spp. Plants were incubated for three more weeks under the same photoperiod and temperatures with ˜70% relative humidity (light cycle) and ˜45% relative humidity (dark cycle), and then evaluated for disease. At least 50% of L. microphyllum pinnules and 25% of L. japonicum pinnules on each inoculated plant had small (1 to 2 mm), brown leaf spots or larger (approximately 5 mm) necrotic spots. B. sacchari was reisolated from both types of spots from both Lygodium spp.; there was no evidence of fungal sporulation on the plants. No symptoms were apparent on control plants. To our knowledge, this is the first report of B. sacchari on a non-Poaceae host in Florida. References: (1) J. L. Alcorn. Ann. Rev. Phytopathol. 26:37, 1988. (2) A. Sivanesan. Graminicolous Species of Bipolaris, Curvularia, Dreschslera, Exserohilum and Their Teleomorphs. CAB International, Wallingford, Oxon, UK, 1987.

Severe aggression in rats induced by mescaline but not other hallucinogens.

Pairs of male Sprague-Dawley rats were administered mescaline, lysergic acid diethylamide (LSD), psilocin, N,N-dimethyltryptamine (DMT), 3,4-dimethoxyphenylethylamine (DMPEA), or 5-hydroxydopamine (5-OHDA) IP prior to being placed in a shock-elicited aggression situation. When foot shock was delivered, controls struck each other with their forepaws, but never engaged in either biting or injurious fighting. Mescaline-treated rats (50 or 250 mg) rarely struck each other, but engaged in nearly lethal biting. While LSD (25--400 micrograms/kg), psilocin (2.0 mg/kg), and DMT (5 mg/kg) produced some biting, this did not significantly differ from controls and never resulted in injuries. At higher doses, psilocin, DMT, and DMPEA decreased the amount and intensity of fighting. Rats treated with 5-OHDA (8--200 mg/kg) or LSD (25--400 micrograms/kg) did not differ from controls. These results suggest that mescaline's ability to induce pathological aggression in rats exposed to foot shock is not shared by other hallucinogens or nonhallucinogenic mescaline analogues.

The Mammography Quality Standards Act of 1992. History and philosophy.

The Mammography Quality Standards Act (MQSA) of 1992 established a precedent in the practice of mammography by creating federal quality standards for all parts of the mammography system. Heralded by some as crucial so all US women can reap the full benefits of early detection of breast cancer, MQSA implementation was delegated to the Food and Drug Administration (FDA) on June 2, 1993. In this article the major historical forces that surrounded MQSA's enactment as well as the FDA's philosophy on regulation development, inspections, and compliance under MQSA is summarized.

Drug-induced ataxia in opponents elicits "pathological" fighting in undrugged rats exposed to footshock.

One member of a pair of rats was administered either mescaline, lysergic acid diethylamide (LSD), pentobarbital, or ethanol intraperitoneally twenty minutes prior to exposure to footshock in the presence of an undrugged opponent. At high doses, all drugs elicited biting from the undrugged rat of sufficient intensity to produce injury to its drugged opponent. Low doses produced species-typical fighting behavior which consisted of striking each other with their forepaws while upright and failed to elicit biting. Biting attacks by the undrugged rat were highly correlated with ataxic behavior by the drugged rat. Conversely, species-typical aggressive behavior was highly correlated with behaviors such as boxing or upright threat posture. These results suggest that drug-induced ataxic behavior may disinhibit mechanisms that regulate intra-species behavior, thus producing behavior that is more typical of inter-species aggression.

Reliability of white blood cell counting.

The Laboratory Proficiency Testing Program has successfully operated mandatory proficiency testing for 13 years in Ontario, Canada, using committees of volunteer peers. This is an alternative to gubernatorial proficiency testing. Using white blood cell (WBC) count determinations as a focus, we present our results. Ninety-six percent of participants attained WBC count results within +/- 10% of an all-methods mean and 77% attained results within +/- 5%. Ninety-six percent displayed satisfactory precision. Details of the program, ie, testing material, computer analysis, reference results, and scope of committee action, are discussed. In 1975, clinical expectations for WBC count determinations greatly exceeded most laboratories' capabilities. By 1987, participants were able to produce reliable, clinically useful WBC count results. The paramount reason for this improvement is the transition from manual to automated counting methods resulting from the stimulus of proficiency testing and the concomitant education.

Nicotine gum in smoking cessation: a placebo-controlled, double-blind trial.

Sixty subjects were run in a study comparing the use of nicotine gum with placebo gum during cessation from smoking. Subjects were given clinic support and chewed the gum ad libitum. A survival analysis showed the two groups differed significantly in successful abstinence over time (p less than .03). Differences between groups appeared early (within weeks) and, at six months, a 28% superiority of nicotine over placebo gum was demonstrated with mean success rates of 48% and 20%, respectively. Between six months and one year, relapse in the nicotine group accounted for the 30% vs. 20% success rates for nicotine and placebo observed at one year. In a pilot study ("dispensary") testing the efficacy of the two gums when intervention was minimal, subjects in both groups resumed smoking within the first two weeks. The enhanced short-term success rates with nicotine gum in the clinic study are attributed to an effective interaction between use of the active preparation and clinic support. Long-term cessation may require extended maintenance procedures and/or an identification of optimal gum use.

Cross Pathogenicity of Gaeumannomyces graminis var. graminis from Bermudagrass, St. Augustinegrass, and Rice in Florida and Texas.

Isolates of Gaeumannomyces graminis var. graminis were obtained from St. Augustinegrass, bermudagrass, and rice in Florida, and rice and St. Augustinegrass in Texas. In Florida, all seven isolates evaluated were cross pathogenic on each of the three grass hosts. Rice isolate FL-173 caused significantly greater disease of the lower leaf sheath and root disease severity of rice compared with other isolates, whether from rice or both turfgrass species. The rice and both turfgrass isolates generally suppressed heights and shoot and root weights compared with the control. All isolates from either rice or both turfgrass species generally had root disease ratings significantly different from the control for either bermudagrass or St. Augustinegrass. However, rice isolate FL-173 and St. Augustinegrass isolate FL-104 were significantly more aggressive on St. Augustinegrass; whereas the maximum root disease rating of bermudagrass was only associated with bermudagrass isolate FL-19 and St. Augustinegrass isolate FL-104. In Texas, both the rice isolate TX-91-1 and the St. Augustinegrass isolate TX-10466-2 of G. graminis var. graminis were pathogenic on St. Augustinegrass, common bermudagrass, and rice. Both isolates caused similar disease severity on common bermudagrass and St. Augustinegrass, but isolate TX 10466-2 caused less severe disease symptoms on rice than did isolate TX-91-1. Overall, G. graminis var. graminis was most aggressive on the host from which it was originally isolated, such as rice or St. Augustine, but differences in host-plant reactions were not always statistically significant, especially with bermudagrass.

Natural Epiphytotic of the Rust Puccinia psidii on Melaleuca quin-quenervia in Florida.

Melaleuca quinquenervia (Cav.) S. T. Blake (melaleuca), a tree of Australian origin, is an invasive weed of natural areas in southern Florida and has been listed as a federal noxious weed. During January 1997, severe incidence of a rust disease was detected on new growth of about 70% of the melaleuca trees over a 2-km strip in Broward and Dade counties. These top-pruned trees were 3 to 5 m tall with bushy appearance and had many new shoots. The rust was observed on melaleuca saplings and trees in a 20-km radius in January through March 1997. Leaf lesions began as chlorotic flecks that expanded, produced spores, and developed into necrotic spots. Infected leaves were severely distorted. Branches were severely defoliated and succulent twigs were often girdled by lesions, causing dieback of the new growth. Yellow uredinia were observed on all young leaves and some petioles and twigs. Urediniospore morphology and dimensions (17 to 27 × 15 to 24 µm) are consistent with the description of Puccinia psidii G. Wint. (1) and the University of Florida's herbarium material of P. psidii on Pimenta dioica (L.) Merr. (allspice) (2). An inoculation test was conducted with 40-cm-tall melaleuca seedlings. Fully expanded leaves and terminals of these seedlings were brushed or sprayed with freshly collected urediniospores, covered with plastic bags, and placed in a growth chamber maintained at 16°C (night) and 26°C (day) with a corresponding 12-h light cycle for 72 h. The plastic bags were then removed and the seedlings maintained in high humidity and ambient temperatures in a shadehouse. Typical symptoms and sporulation occurred after 10 and 12 days, respectively, following inoculation. Although P. psidii has been recorded on 11 genera in Myrtaceae in the Americas (1,2), including melaleuca, an epiphytotic of this magnitude on melaleuca has not been reported. A different race of P. psidii has been suspected to cause sudden epiphytotics on Pimenta officinalis Lindl. in Jamaica (1). Further research related to host range is warranted to determine the specificity of P. psidii, as this rust may have potential as a microbial biological control agent of melaleuca. References: (1) G. F. Laundon and J. M. Waterson. C.M.I. Descriptions of Pathogenic Fungi and Bacteria No. 56, 1965. (2) R. B. Marlatt and J. W. Kimbrough. Plant Dis. Rep. 63:510, 1979.

Viability and stability of biological control agents on cotton and snap bean seeds.

Cotton and snap bean were selected for a multi-year, multi-state regional (south-eastern USA) research project to evaluate the efficacy of both commercial and experimental bacterial and fungal biological control agents for the management of damping-off diseases. The goal for this portion of the project was to determine the viability and stability of biological agents after application to seed. The biological seed treatments used included: (1) Bacillaceae bacteria, (2) non-Bacillaceae bacteria, (3) the fungus Trichoderma and (4) the fungus Beauveria bassiana. Seed assays were conducted to evaluate the following application factors: short-term (< or = 3 months) stability after seed treatment; quality (i.e. isolate purity); compatibility with chemical pesticides and other biocontrol agents; application uniformity between years and plant species. For the bacterial treatments, the Bacillaceae genera (Bacillus and Paenibacillus) maintained the greatest population of bacteria per seed, the best viability over time and the best application uniformity across years and seed type. The non-Bacillaceae genera Burkholderia and Pseudomonas had the least viability and uniformity. Although Beauveria bassiana was only evaluated one year, the seed fungal populations were high and uniform. The seed fungal populations and uniformity for the Trichoderma isolates were more variable, except for the commercial product T-22. However, this product was contaminated with a Streptomyces isolate in both the years that it was evaluated. The study demonstrated that Bacillaceae can be mixed with Trichoderma isolates or with numerous pesticides to provide an integrated pest control/growth enhancement package.

Modality effects in short term recognition memory.

Retention was assessed using a four-alternative recognition test in a modified Brown-Peterson paradigm. Performance decreased with the length of the distraction interval at a faster rate when the test modality (auditory or visual) did not match the presentation modality than when test and presentation modalities did match. These results, which were replicated in a second experiment, were interpreted in terms of a dual-access model of the recognition process and a feature conception of memory codes. Also, in Experiment 1, modality-specific encoding was not circumvented by dual-modality presentation (auditory plus visual): dual-modality presentation resulted in performance comparable to that observed following visual presentation. When subjects were instructed to attend to both modalities equally in Experiment 2, the pattern of results reflected a corresponding shift in attentional bias but modality-dependent encoding was circumvented only partially. This result was interpreted as being inconsistent with either the notion of modality-specific processing capacities or dual-code theory.