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At least 20 epidemics of Fusarium head blight (FHB) of wheat have been registered in the last 50 years in Argentina, with variable intensity. Damage induced by the disease is further aggravated by the presence of mycotoxins in affected grains that may cause health problems to humans and animals. The trichothecene chemotype was analyzed for 112 isolates of Fusarium graminearum from Argentina by polymerase chain reaction and two field trials were conducted to study the aggressiveness of a subsample of 14 representative isolates and to analyze deoxynivalenol (DON) production in planta and in vitro. All isolates belonged to the 15-acetyl-DON chemotype. Significant differences were observed in both the symptom severity induced in wheat spikes and the in vivo DON production, and a close correlation was found between these two variables. However, in vitro toxigenic potential was not correlated with the capacity of F. graminearum isolates to produce DON under natural conditions. The progress of infection in the rachis of inoculated wheat spikes was analyzed and the pathogen presence verified in both symptomatic and symptomless spikes. Even isolates with a limited capacity to induce symptoms were able to colonize the vascular tissue and to produce considerable amounts of DON in planta.

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The green belt area surrounding the city of La Plata, Argentina, produces more than 70% (around 280 ha) of the lettuce (Lactuca sativa L.) cultivated under greenhouse for fresh consumption in the country. In February 2011, April 2012, and December 2013, butterhead lettuce plants from cv. Lores showing wilt and stunted growth symptoms, red-to-brown discoloration of vascular tissues, and yellow leaves were found in greenhouses in La Plata. Sections of tap root, crown and stem from symptomatic plants showing dark-brown streaking of the vascular tissue were surface sterilized and isolations were made. A total of 21 monosporic isolates obtained from different lettuce production fields were identified as Fusarium oxysporum Schltdl. based on morphological characteristics (2). Vegetative compatibility group (VCG) analysis (1) was conducted on 11 of these isolates and all isolates belonged to the same VCG. To fulfil Koch's postulates, two pathogenicity tests were conducted with these 11 isolates in winter (July 2012) and summer (December 2013). Healthy 20-day-old butterhead lettuce seedlings of two cultivars (Reina de Mayo and Lores in the winter and summer tests, respectively) were inoculated by dipping the roots of each plant in a spore suspension (~3 × 105 CFU ml-1), planted in 1-liter pots containing autoclaved soil and grown in a greenhouse with only natural daylight. Control treatments were prepared by dipping the seedling roots in sterilized distilled water. All inoculated plants showed wilt symptoms 15 to 20 days after inoculation (dai) and 45 to 50 dai in the summer and winter pathogenicity tests, respectively. The delay in the appearance of symptoms observed during the winter test is consistent with the effect of planting date on the development and final incidence of Fusarium wilt of lettuce reported by Matheron et al. (3). No symptoms were observed in control treatments. F. oxysporum was re-isolated from vascular tissues of the stems of symptomatic plants and the formae speciales lactucae J.C. Hubb. & Gerik was confirmed by PCR using the specific primer pair GYCF1 and R943 (4). The identification of only one VCG for the tested isolates agrees with the hypothesis of seed transmission of the pathogen, which might explain the dissemination of Fusarium wilt of lettuce in geographically distant areas (2). Studies are being carried out to determine the race of these Argentinian isolates of F. oxysporum f. sp. lactucae. To our knowledge, this is the first report of F. oxysporum f. sp. lactucae infecting lettuce in Argentina. References: (1) J. C. Correll et al. Phytopathology 77:1640, 1987. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006. (3) M. E. Matheron et al. Plant Dis. 89:565, 2005. (4) G. C. Y. Mbofung and B. M. Pryor. Plant Dis. 94:860, 2010.

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Annually, ~20 ha of sweet basil (Ocimum basilicum L.) are cultivated in greenhouses in the green belt area surrounding La Plata, Argentina, mainly for fresh consumption. In 2004 to 2007, basil plants of cv. Genovese showed wilt symptoms, necrosis of leaves and stems, asymmetrical growth, and discolored vascular tissue in greenhouses in La Plata. In 2007, the same symptoms were observed on plants of cv. Morada grown from seeds that were produced in Italy. Isolations were completed from root, crown, and stem sections of diseased plants of cv. Genovese from three greenhouses in 2004 to 2007, and from commercial seeds, stem sections, flowers, and seeds of diseased plants of cv. Morada in 2007. Seeds and portions of symptomatic tissues were surface-disinfested with 0.5% NaOCl for 1 min, rinsed in sterilized distilled water, air dried, and plated on 2% potato dextrose agar (PDA). Twenty-seven isolates were identified as Fusarium oxysporum Schltdl. based on morphological characteristics (4), and the species identification confirmed by PCR assay using a F. oxysporum f. sp. basilici-specific primer pair, Bik 1 and Bik 2 (1). Vegetative compatibility groups (VCGs) were determined for the 27 isolates through complementation of nitrate-nonutilizing mutants generated from these isolates (2) and paired with two Italian tester strains from an international collection (PVS-Fu 220 and PVS-Fu 125, provided by V. Balmas, Univeristà degli Studi di Sassari, Italy). All 27 isolates from Argentina belonged to VCG 0200. This is a unique VCG for F. oxysporum f. sp. basilici and has been identified in Israeli, American, and Italian isolates of the fungus (3). To fulfill Koch's postulates, pathogenicity tests were conducted with 12 isolates selected to reflect the multiple sources of fungal recovery, including root, crown, and stem sections, and leaves of diseased plants of cv. Genovese and commercial seeds, stem sections, flowers, and seeds of cv. Morada. Isolates were each grown on moistened (40% w/w), autoclaved, polished rice for 10 days, dried, and ground in a grinder. The number of CFU/g rice was determined by serial dilution plating onto PDA plates. The inoculum was added to autoclaved soil at 104 CFU/g dry soil. For each isolate, 8 healthy basil seedlings of each of cvs. Genovese and Morada were planted in pots, each containing 1 liter of inoculated soil. The control treatment consisted of 8 basil seedlings of each of the same cultivars planted in autoclaved soil mixed with sterilized, ground, polished rice. Plants were grown in a greenhouse with natural daylight for 45 to 50 days after inoculation. All inoculated plants showed the same symptoms described for the original basil plants. No symptoms were observed on the control plants. F. oxysporum f. sp. basilici was re-isolated from the vascular tissue of stems of symptomatic plants but not from control plants, and species identification confirmed by PCR assay as previously described. The presence of the pathogen was verified in the seed lot produced in Italy, suggesting that this could have been a source of inoculum that introduced the pathogen into La Plata, Argentina, as supported by the hypothesis that infested seed resulted in spread of a clonal population of F. oxysporum f. sp. basilici internationally (1). To our knowledge, this is the first report of F. oxysporum f. sp. basilici infecting sweet basil in Argentina. References: (1) A. Chiocchetti et al. Plant Dis. 85:607, 2001. (2) J. C. Correll et al. Phytopathology 77:1640, 1987. (3) A. Garibaldi et al. Plant Dis. 81:124, 1997. (4) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

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OBJECTIVE: To examine the accuracies of body mass index (BMI) and skinfold thicknesses in classifying the body fatness of 7365 8- to 19-year-old subjects in a national sample. STUDY DESIGN: We used percent body fat determined by dual-energy x-ray absorptiometry (PBFDXA) between 1999 and 2004. Categories of PBFDXA and the skinfold sum (triceps plus subscapular) were constructed so that that numbers of children in each category were similar to the number in each of 5 BMI categories based on the Centers for Disease Control and Prevention growth charts. RESULTS: Approximately 75% of the children and adolescents who had a BMI-for-age ≥ 95th percentile (considered obese) had elevated body fatness, but PBFDXA levels were more variable at lower BMIs. For example, only 41% of the boys who had a BMI < 25th percentile, had a similarly low PBFDXA. The use of the skinfold sum, rather than BMI, slightly improved the identification of elevated levels of body fatness among boys (P = .03), but not among girls (P > .10). A low sum of the triceps and subscapular skinfold thicknesses was a better indicator of low PBFDXA than was a low BMI, but differences were smaller among children with greater levels of body fatness. Among girls who had a PBFDXA above the median, for example, BMI and the skinfold sum were correlated similarly (r = 0.77-0.79) with body fatness. CONCLUSIONS: Both BMI and skinfold thicknesses are fairly accurate in identifying children who have excess body fatness. In contrast, if the goal is to identify children who have low body fatness, skinfold thicknesses would be preferred.

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OBJECTIVES: We analyzed the health of Mexican American women aged 15 to 44 years, by generation and language preference, to guide planning for reproductive health services in this growing population. METHODS: We used personal interview and medical examination data from the 1999 to 2004 National Health and Nutrition Examination Surveys. We used SUDAAN for calculating age-adjusted prevalence estimates of demographic and health characteristics. The Satterthwaite adjusted F test and Student t test were used for subgroup comparisons. RESULTS: The women had different health profiles (P < .05) by generation and language preference. Second- and later-generation women and women who used more English were more likely to be sexually active, to have been younger at first intercourse, and to have had more male sexual partners than were first-generation women and women who used more Spanish. Compared with their first-generation counterparts, second- and later-generation women drank more alcohol, were better educated, had higher incomes, and were more likely to have health insurance. Third-generation women were more likely to have delivered a low-birthweight baby than were first-generation women. CONCLUSIONS: Differences by generation and language preference suggest that acculturation should be considered when planning interventions to promote healthy reproductive behaviors among Mexican American women.

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Night-blooming cereus (Hylocereus undatus A. Berger) is generally used as rootstock of ornamental cactus because of its rapid growth and tolerance to humid substrates. Since 2002, in Gran Buenos Aires, a new disease has been observed in grafted crops in all production stages. Incidence was as much as 30% in many greenhouses. Symptoms consisted of soft rot that started near the soil line and developed upward until it affected all the rootstock. The scion was not rotten, but died as a consequence of rootstock infection. All the roots were symptomless. For pathogen isolation, symptomatic tissues were surface disinfected by a 1-min immersion in 0.2% NaOCl, placed on potato dextrose agar (PDA), and incubated at 22 ± 2°C. Only a Fusarium spp. was consistently isolated in pure culture. Twenty healthy potted night-blooming cereus plants, 10 of them previously injured with needles on the rootstock near the soil line, were gently removed from the substrate and inoculated by a 1-min immersion of their base in a suspension of 1.4 × 106 conidia per ml of sterile distilled water, prepared from 15-day-old cultures. Ten control plants, five of them previously injured, were immersed in sterile distilled water. Inoculated and noninoculated plants were replanted in the original substrate, placed in a climatic chamber at 22 ± 2°C, and monitored for disease expression. Basal rot was observed on all injured inoculated plants 12 days after inoculation. Symptoms on undamaged plants appeared 22 days after inoculation. After 72 days of incubation, all inoculated plants were totally rotten. Control plants remained symptomless. The same pathogen was reisolated to fulfill Koch's postulates. For species identification, single-spore cultures were grown on PDA and carnation leaf agar in a climatic chamber at 23 ± 2°C with a 12-h darkness/near ultraviolet light regimen. The micromorphology and culture features, mainly conidial ontogeny, were consistent with descriptions of Fusarium oxysporum Schlechtend.:Fr. (1). The pathogen was able to penetrate undamaged tissues. Needle injuries accelerated infection. To our knowledge, this is the first report of Fusarium oxysporum on H. undatus in Gran Buenos Aires, Argentina. A culture of the pathogen was deposited at the fungal collection of PRHIDEB-CONICET (University of Buenos Aires) as BAFCult 3158. Reference: (1) P. E. Nelson et al. Fusarium species. An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, PA, 1983.

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Since 1986, irregular, blotchy lesions of leaves and petioles of tulip tree (Liriodendron tulipifera L.) have been observed each summer in the city of La Plata, Argentina. Leaf spots are initially 2 to 3 mm in diameter and water soaked, and then they become brown or black with faint chlorotic margins that are more noticeable on the adaxial surface. Lesions may attain a diameter of 12 mm. Veins and petioles may also be affected and lesions may coalesce, especially at leaf margins. Surface-sterilized pieces of necrotic tissue collected from eight sites in the La Plata area were plated on potato dextrose agar and incubated at 27°C. Two Colletotrichum species were consistently isolated from the lesions. Single-spore cultures were obtained and identified as C. acutatum (1) and C. gloeosporioides (4). When cultured on V8 medium, mycelial growth of C. acutatum was tufted and pale gray, and the reverse side of colonies was buff to cream or pale gray to tan, but never dark. Hyaline conidia were buff to rosy buff en masse and elliptical or elongated with abruptly tapering ends measuring 8.04 to 13.58 × 2.68 to 3 µm. Micromorphology of conidia were compared with C. acutatum "Herb IMI 232176" (1). C. gloeosporioides cultures were dark gray; their reverse was dark mouse gray to fuscous black. The cirrhus was peach to orange and hyaline conidia were oblong with rounded ends measuring 8.6 to 13.40 × 2.68 to 4.02 µm. Pathogenicity was verified on greenhouse-grown tulip trees and strawberry cv. Pájaro (Fragaria × ananassa) by spray inoculation with conidial suspensions of C. acutatum (107/ml), C. gloeosporioides (106/ml), and a mixture of both species (equal parts of each suspension). Controls were sprayed with sterile distilled water. Irregular, blotchy lesions of tulip tree appeared 30 days after inoculation. Anthracnose symptoms (3) were observed on strawberries 7 days after inoculation. In all cases, lesions produced by the mixture were larger than those obtained with individual species. The inoculated fungi were reisolated from lesions of all species tested, fulfilling Koch's postulates. No lesions were observed on control plants. Voucher specimens were deposited in La Plata Spegazzini Herbarium, Argentina as C. acutatum (LPS 47187) and C. gloeosporioides (LPS 47188); cultures of both fungi were also deposited as LPSC 795 and LPSC 796, respectively. C. acutatum and C. gloeosporioides cause Liriodendron leaf blotch in Argentina. Glomerella cingulata was previously reported affecting L. tulipifera (2), but to our knowledge, this is the first report of tulip tree as a host of C. acutatum. References: (1) B. J. Dyko and J. E. M. Mordue. No. 630 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1979 (2) K. Ito and T. Kobayashi. Bull. For. Exp. Stn. Meguro 146:1, 1962. (3) C. J. Ramallo et al. Plant Dis. 84:706, 2000. (4) J. A. von Arx. Phytopathol. Z. 29:413, 1957.

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Fungi from the soil of public areas in La Plata, Argentina were isolated and evaluated for their biological interaction with Toxocara canis eggs in vitro. We isolated and identified two fungal species: Fusarium pallidoroseum and Mucor hiemalis. Each species was co-cultured with T. canis eggs in sterile distilled water. The samples were observed by light and scanning electron microscopy (SEM) at days 4, 7 and 14 post-inoculation. Under the conditions of our experiments, F. pallidoroseum exhibited a high ovicidal activity on T. canis eggs, whereas M. hiemalis exhibited no such effects.

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Fusarium solani Mart. (Sacc.) is the causal agent of stem rot and damping-off of lisianthus (Eustoma grandiflorum (Raf.) Shinn.) (1). Since the end of the 1980s, when this flower crop was introduced in Argentina, it has been affected by a basal stem rot (2). A previously undescribed disease was observed in 100% of the greenhouses in the Buenos Aires Province that grow lisianthus. Symptoms that developed after seedlings were transplanted included stunting, shortened internodes with reduced stem diameter, and small narrow leaves that were a dull green color. Some affected plants turned yellow-brownish and died 2 to 3 months after transplanting. Other plants recovered but produced low quality flowers later than normal. A third group of plants remained stunted (5 to 10 cm high) until the last flower harvest (about 8 to 10 months). F. solani was consistently isolated from basal stems and roots of diseased plants. For pathogenicity tests, inoculum was produced by culturing the fungus for 10 days in petri dishes containing sterile moistened rice. Inoculum was air dried, crushed, and mixed with soil that had been autoclaved at 112°C for 40 min on each of two consecutive days. The propagules in the soil were estimated by soil plate dilutions on the Nash & Snyder-PCNB medium at a ratio of about 104 CFU/g soil. Twenty plants of each cultivar Echo White and Echo Blue, whose roots had been pruned, were planted in both infested and noninfested soil. After about 40 days, stunting was observed in 85% of the inoculated plants, while controls remained asymptomatic. F. solani was reisolated from symptomatic plants, thus fulfilling Koch's postulates. A test also was conducted in a commercial greenhouse that produced lisianthus for several years, in which healthy plants were planted in three plots fumigated with methyl bromide and in three nonfumigated plots. The mean cfu/g soil of F. solani in the methyl-bromide treated plots was 5 × 102 and 1.6 × 104 CFU/g in the nontreated plot. After 120 days, the incidence of stunting in the treated plots was 0.6 and about 88% in the control plots. F. solani was recovered from symptomatic plants. Because disinfestation of soil is generally practiced in flower production, stunted plants are limited and can be confused with root problems. This is the first report of F. solani causing stunt on lisianthus. References: (1) J. J. Taubenhaus and W. N. Ezekiel. Phytopathology 24:19, 1934. (2) S. M. Wolcan and G. A. Lori. Invest. Agr. Prot. Veg. 11:465, 1996.

RESUMO

Geraldton waxplant (Chamaelauciun uncinatum Schauer.) is a shrub that produces flowered branches used in bouquets. Waxplant was introduced into Argentina (Buenos Aires province) in the 1990s and currently is cultivated in greenhouses. In the summer of 1995, a previously undescribed disease was observed on plants at different stages of growth. Plants showed a progressive yellowing of the branches from the base to the top of the stems. Leaves of diseased plants became grayish green, then yellow, and finally straw colored. Leaves remained attached to the branches after the plants died. Roots and stem discoloration was observed and the root cortex sloughed off. A Phytophthora sp. was isolated from the roots and lower stems of symptomatic plants. Koch's postulates were completed in a greenhouse at 28 to 34°C using the cvs. Snowflake, Violet, and Orchid. Inoculum was obtained by growing the fungus for 7 days in Petri dishes containing an autoclaved wet mixture of polished rice + wheat bran + V8 juice + perlite (1:1:1:1, by volume). The inoculum was mixed with soil (4:100, wt/wt) in pots, and 15 4-month-old plants per cultivar were transplanted into infested and noninfested soil. Plants of the cv. Snowflake were the most susceptible with symptoms starting 25 days after inoculation. At the end of the trial (five months) 86% of these plants died. Disease development was delayed on plants of cvs. Orchid and Violet and mortality was only 20% on Orchid and 26% on Violet. Control plants remained healthy. The Phytophthora sp. was reisolated from plants showing typical symptoms. The fungus was cultivated on potato-dextrose agar at 25°C and morphological characteristics were recorded. The colony diameter was 3.7 cm after 5 days. Ovoid, obturbinate and obpyriform to limoniform, papillate and caducous sporangia were observed. They averaged 42.1 ± 10.7 × 31.7 ± 9.2 µm (range 25.0 to 65.0 × 18.7 to 55.0 µm) with a length-breadth ratio = 1:1 to 1.81, av. 1.25:1. Many sporangia were distorted in their shapes and averaged 61.7 ± 30.5 × 24.8 ± 4.5 µm (range 27.5 to 125.0 × 20.0 to 32.5 µm) with a length-breadth ratio = 1.31:1 to 4.6:1, av. 2.1:1. After the zoospores were discharged, a narrow exit pore was observed (3.7 to 8.7 µm, av. 6.9 µm). Pedicels were not conspicuous or were short when present. Oogonia and amphigynous antheridia were readily observed in single culture. Spherical oospores nearly filling the oogonium and containing many subcellular inclusions averaged 29.7 ± 8.9 µm (range 17.5 to 47.5 µm). Terminal or intercalary, rounded to ovoid chlamydospores developed in smooth or swollen hyphae. Based on cultural and morphological characteristics, the species infecting waxplant was identified as P. boehmeriae Sawada (1). This is the first record of P. boehmeriae on geraldton waxplant. References: (1) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN.

RESUMO

During the summer of 1995-1996, an 80-ha field of 6-year-old asparagus plants (cv. UC 72) in Saladillo (Province of Buenos Aires) was affected by a decline syndrome (1). The plants showed a decline in vigor and approximately 60 to 70% of the plants died. The symptomatic plants were chlorotic, stunted, with stem lesions and crown and root rot. Fusarium moniliforme and F. proliferatum were isolated from vascular and epidermal tissues of roots, crowns, and stems. Identification of Fusarium to species was made by examining conidiogenous cells from colonies cultured on KCl medium (2). Microconidia were born in long and short chains and false heads. The isolates were identified based on the the presence of polyphialides in F. proliferatum and their absence in F. moniliforme, which produces monophialides only (2). In two separate trials, asparagus seeds (cv. UC 72) were surface sterilized and placed in steamed soil infested with a conidial suspension of each species. The viable propagules in the soil (CFU per g) were estimated by soil plate dilutions on Nash & Snyder-PCNB (pentachloronitrobenzene) medium. The F. moniliforme and F. proliferatum soil densities were 19.2 × 103 and 23 × 103 CFU per g of soil, respectively. The pots were placed in the greenhouse on different benches to avoid cross-contamination. After 4 months, inoculated plants showed root and crown discoloration. F. moniliforme and F. proliferatum were reisolated (64 and 75%, respectively) from discolored portions of internal and external root and crown tissues. Although the stems did not show symptoms, F. moniliforme and F. proliferatum were also recovered (27 and 38%, respectively) from asymptomatic tissues. Six months after inoculation the plants developed chlorotic symptoms with crown and root rot, and then wilted. F. moniliforme and F. proliferatum were reisolated from root systems, crowns, and stems of all inoculated plants. F. moniliforme and F. proliferatum are involved in corn stalk and ear rot in Argentina. Corn and asparagus are frequently grown in close proximity and often follow one another at a particular site. Airborne and soil debris carrying F. moniliforme and F proliferatum from corn may be an additional source of inoculum for asparagus in Argentina. The results indicate that the presence of F. moniliforme and F. proliferatum is a factor that contributes to asparagus decline in Argentina. References: (1) W. H. Elmer et al. Plant Dis. 80:117, 1996. (2) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University, University Park, 1983.

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Soybean (Glycine max) is an important crop in the northern area of the province of Buenos Aires, Argentina. Phomopsis spp. and Fusarium spp. are the prevalent pathogens in soybean seeds. Infection levels for both pathogens can be greater than 50%. In seedlings growing in sand or soil, both pathogens produce rotten lesions on cotyledons and hypocotyls, but over the past 2 years a plumele soft rot has also been observed associated with detached teguments that was previously demonstrated to be caused by Fusarium spp. (1). In 1996, seeds with a germination level lower than 82% were selected from an assay including 22 cultivars, and examined for the presence of Fusarium spp. The infection level ranged from 2 to 16%, and the Fusarium spp. present were identified as F. equiseti, F. oxysporum, and F. pallidoroseum. After each Fusarium sp. was cultured on potato dextrose agar, a conidial suspension was prepared and adjusted to 1.8 × 106 conidia per ml. This inoculum was sprayed on water-soaked paper, in petri dishes, and good quality soybean seeds were placed on the paper, with 400 seed for each Fusarium sp. The petri dishes were maintained at 26°C for 24 h. Control seeds were plated on water-soaked paper. Inoculated seeds were sown in sand with a water content of 16% wt/wt, covered with polyethylene bags, and incubated for 7 days in a growth chamber at 26°C and a 12-h light period. All the samples inoculated with the three Fusarium spp. exhibited seed rot, seedlings with cotyledon and hypocotyl lesions as described previously (2), but also plumele soft rot. Control seedlings remained symptomless. This is the first report confirming that the characteristic plumele soft rot of soybean seedlings is a nonspecific symptom associated with F. equiseti, F. oxysporum, and F. pallidoroseum. References: (1) B. González et al. ISTA-PDC Symp., 2nd. 1996. (2) G. S. Saharan and V. K. Gupta. Plant Dis. Rep. 56:693, 1972.

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In Argentina, due to climatic conditions, Fusarium head blight (FHB) caused by Fusarium graminearum, affected the 1993/94 wheat crop. To evaluate the severity of this disease, samples of wheat where gathered from four zones of the wheat area. Sanitary conditions and mycotoxin contamination were determined. One zone (IIN) was intensely affected by FHB with 90% of samples in grade III (bad quality). No samples were grade I (good quality). The other zones were less affected falling into grade I or II (moderate quality). In all samples tested F. graminearum was the most prevalent species singly or in combination with others. Zone II N, with a DON mean level of I1.26 ppm, did not fulfil aceptability limits, whereas zones IIS, III and IV with overall means of 2.12, 1.57 and 1.0 ppm, respectively, did. Statistical analysis showed a close relation between percentage FHB and DON contamination (r:-0.71, p<0.01) in infected samples.

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In trials of wheat establishment in irrigated areas in the Patagonian valleys (Picún Leufú), sectors with plants showing symptoms of typical foot-rot were detected. In order to investigate the phytopathogenic mycoflora of these soils (arid zone), the population of Fusarium spp was analysed quali- and quantitatively and its tolerance to water stress by measuring the mycelial growth in the presence of different water potentials. Fusarium spp detected in that type of soil did not coincide with those commonly present in traditional wheat zones. In 100% of the samples analysed the predominant fungus present vas Fusarium equiseti. This species was the one isolated from wheat plants with foot-rot. It was isolated in soil sown with wheat as well as in soils free of wheat. In none of the samples, was the number less than 10,000 propagules/g of soil. In sporadic cases F. moniliforme and F. oxysporum appeared. When comparing, in different water potentials, the growth capacity of isolated species in the arid zone with respect to the other phytopathogenic species common in wheat (F. graminearum an F. poae), it was noted that F. equiseti showed the greatest tolerance to water stress. This species had the capacity to grow in water potentials as low as -12 MPa. This physiological characteristic was manifest in the strains of F. equiseti found in the arid zone and also in those isolated in a wet zone.(ABSTRACT TRUNCATED AT 250 WORDS)

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In trials of wheat establishment in irrigated areas in the Patagonian valleys (Picún Leufú), sectors with plants showing symptoms of typical foot-rot were detected. In order to investigate the phytopathogenic mycoflora of these soils (arid zone), the population of Fusarium spp was analysed quali- and quantitatively and its tolerance to water stress by measuring the mycelial growth in the presence of different water potentials. Fusarium spp detected in that type of soil did not coincide with those commonly present in traditional wheat zones. In 100

of the samples analysed the predominant fungus present vas Fusarium equiseti. This species was the one isolated from wheat plants with foot-rot. It was isolated in soil sown with wheat as well as in soils free of wheat. In none of the samples, was the number less than 10,000 propagules/g of soil. In sporadic cases F. moniliforme and F. oxysporum appeared. When comparing, in different water potentials, the growth capacity of isolated species in the arid zone with respect to the other phytopathogenic species common in wheat (F. graminearum an F. poae), it was noted that F. equiseti showed the greatest tolerance to water stress. This species had the capacity to grow in water potentials as low as -12 MPa. This physiological characteristic was manifest in the strains of F. equiseti found in the arid zone and also in those isolated in a wet zone.(ABSTRACT TRUNCATED AT 250 WORDS)

RESUMO

A toxicogenic strain of Fusarium graminearum which produces DON and ZEA was cultivated on natural solid substrates (wheat, polished rice and hulled rice) under different environmental conditions. The production of both toxins and mycelium growth (in terms of glucosamine) were evaluated to establish the relation between the production of DON and ZEA and the different mycelium growth on the substrates mentioned above. Polished rice was the substrate on which most production of both toxins was obtained. Comparing the three substrates studied, the highest quantities of DON were obtained at a temperature of 27 degrees C during incubation period, being indifferent to the presence of light except in the case of hulled rice. Whereas for ZEA the best conditions in wheat and polished rice were medium temperatures (17 degrees-21 degrees C respectively) and darkness. While in hulled rice the ideal conditions for the production of both toxins were temperature of 27 degrees C and the presence of light. Concerning the mycelium growth, this was very scarce when cultivated in hulled rice, increasing in polished rice and being largest in wheat. The increase or reduction of the mycelium growth in the different substrates was not proportional to the increase or decrease of the production of both toxins. Therefore, production of DON and ZEA could be subjected to the nature of the substrate and environmental conditions, more than the rate of development of Fusarium graminearum in cereal grains.

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Isolations from different hosts were performed to identify by their morphological, biometric and culture characteristics the species of the genus Fusarium commonly affecting crops in La Plata and its surroundings. An identification index was designed with the species isolated and a comparative chart was constructed through a revision of the genus to establish equivalents between the main classification systems.

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Isolations from different hosts were performed to identify by their morphological, biometric and culture characteristics the species of the genus Fusarium commonly affecting crops in La Plata and its surroundings. An identification index was designed with the species isolated and a comparative chart was constructed through a revision of the genus to establish equivalents between the main classification systems.

RESUMO

Toxic metabolites from some Fusarium poae (Peck) Wollenweber strains can produced alimentary toxic aleukia in man. In order to establish the toxicity of a F. poae strain isolated in our country, a skin test was performed in a depilated area of the flank of non-pigmented skin and white hair rabbits. The toxicity of culture extracts, measured according to the intensity of the lesions, was evidenced by the cellular degenerative processes induced. Rats fed with the same fungus strain cultured on sterile corn developed internal haemorrhages.

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RESUMO

Ciertas cepas de Fusarium poae (Peck) Wollen. son productoras de metabolitos que ocasionan la aleuquia toxica alimenticia (A.T.A.) en seres humanos, como sucedio en Rusia en 1942. Para establecer el poder toxico de una cepa de Fusarium poae aislada de trigo, se efectuo una prueba biologica sobre piel de conejo. Con ese fin se utilizaron conejos de pelo y piel blancos a los que se rasuro una superficie del flanco donde se probaron posteriormente los extractos. El poder de toxicidad fue medido en base a una escala de acuerdo al grado de lesion producido. Se demostro que la cepa era realmente toxica dado que provoco avanzados procesos degenerativos celulares. Se suministraron oralmente cultivos del mismo hongo en maiz esteril a ratas albinas las que sufrieron hemorragias internas

Assuntos