Asian Soybean Rust: Incidence, Severity, and Morphological Characterization of Phakopsora pachyrhizi (Uredinia and Telia) in Argentina.

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is the most destructive disease of soybean (Glycine max) in many areas of the world. ASR was first detected in Argentina during 2002 in a limited area in the northern region of the country (2). During the 2004 growing season, P. pachyrhizi spread rapidly throughout most soybean growing areas of northwestern and northeastern Argentina. ASR was also was found in some fields in Entre Ríos and Santa Fe provinces. In all areas, symptoms were expressed late in the 2004 season (growth stages R5.5 to R7) and yield losses were minimal. The objectives of this study were to quantify P. pachyrhizi infection in the canopy and morphologically characterize the fungus from fields where it had been previously detected by polymerase chain reaction (PCR) (3). Incidence (percentage of plants affected) and severity (percentage of leaf area affected, including chlorosis) were visually estimated for 10 plants arbitrarily collected (April 2004) from each of three fields located in Charata (Chacabuco), Chaco Province (Sample 1, collected in the R6 stage), La Paloma (Moreno), Santiago del Estero Province (Sample 2, stage R6 to R7), and Tolloche (Anta), Salta Province (Sample 3, stage R5.5). Disease assessments were made for the lower, middle, and upper canopy from 15 leaves per plant. The number of pustules per cm2 and uredinia per lesion were recorded from the undersides of central leaflets for each trifoliolate observed. Tissue sections were made to observe fructifications of P. pachyrhizi. Incidence of affected plants was 100% in all fields. Disease severity for Sample 1 was 45% (range 30 to 60%), 20% (10 to 30%), and 10% (5 to 20%) for the lower, middle, and upper canopy, respectively; for Sample 2: 60% (30 to 80%), 40% (25 to 50%), and 25% (15 to 40%) for the lower, middle, and upper canopy, respectively; and for Sample 3: 25% (10 to 50%), 15% (10 to 20%), and 10% (5 to 15%) for the lower, middle, and upper canopy, respectively. The number of pustules per cm2 for Sample 1 was 156/cm2 (range 88 to 200); Sample 2: 172/cm2 (128 to 232); and Sample 3: 120/cm2 (72 to 232). The number of uredinia per lesion for Sample 1 was 6 per lesion (range 1 to 15); Sample 2: 5.5 per lesion (1 to 13), and Sample 3: 2.8 per lesion (1 to 5). The two spore types that were commonly observed were urediniospores and teliospores. Telia were found on infected leaves mixed with uredinia in every sample. Urediniospores measured 16 to 22 µm (mean 18.5 µm) × 25 to 30 µm (mean 27 µm). Teliospores measured 8 to 11 µm (mean 9 µm) × 19 to 27 µm (mean 23.8 µm). Spores sizes are in the range described by Ono et al. (1). To our knowledge, this is the first report of epidemiological and morphological characterization of ASR in Argentina and the first report of the telial stage of P. pachyrhizi on soybean in South America. References: (1) Y. Ono et al. Mycol. Res. 96:825, 1992. (2) R. L. Rossi. Plant Dis 87:102, 2003. (3) SINAVIMO, Sistema Nacional Argentino de Vigilancia y Monitoreo de plagas. Roya de la soja: Resultados de la campaña 2003-2004. On-line publication. SENASA, 2004.

Validation of a continuous penile blood-flow measurement by pulse-volume-plethysmography.

Today, in the assessment of cavernous artery blood-flow, the most commonly used technique is Doppler ultrasound velocimetry (continuous, pulsed, color-coded or power), which is often considered as the gold standard. Plethysmographic techniques and radioactive tracers have been widely used for the assessment of global penis flow variations but are not adequate for continuous blood-flow measurement. A new pulse-volume plethysmographic (PVP) device using a water-filled penile cuff was employed to assess continuous blood-flow measurement in the penis. Simultaneously Doppler velocity was recorded and served as a gold standard. A penile water-cuff is connected through a pressure tube to a three-way tap. The pulse-volume changes in the penile water-cuff are measured by means of a latex membrane placed over one of the three-way taps. The displacements of the latex are recorded by a photoplethysmograph. The third tap is connected to a 5 l perfusion bag placed 30 cm above the penis so as to maintain constant pressure in the whole device whatever the penis volume. Twenty-four volunteers were tested. The Doppler velocity signal and pulse volume of cavernous arteries were measured simultaneously after PGE1 intra-cavernous injection. Blood-flow variations were induced by increasing penis artery compression with a second penile water-cuff used as a tourniquet fitted onto the penis root, and the pressure of which could be modified by a water-filled syringe. The amplitude of the plethysmographic pulse-volume signal and the area under the Doppler velocity signal were correlated. The inter-patient (n=24) correlation ranged from 0.455 to 0.904, with a mean correlation of 0.704 and P<0.0001. PVP measurement by a water-filled cuff was validated by ultrasound velocimetry. This new continuous, non-invasive and easy-to-use technique enables physiological and physiopathological flow-measurement during sleep, under visual sexual stimulation (VSS), or following artificial erection. Simultaneous recording of penile blood-flow by PVP and intra-cavernous pressure (ICP) measured by a non-invasive device will provide fundamental inflow and outflow information in both physiological and pathophysiological conditions, and further enable venous leakage to be assessed by a mathematical model.

First Report of Nectria haematococca Causing Wilt of Olive Plants in Argentina.

Death of 8- to 12-month-old olive plants (Olea europaea L. 'Arbequina', 'Arauco', and 'Picual') has been observed since 1998 in northwestern Argentina. No mycelium or perithecium was observed when examining rotting roots of greenhouse-collected plants. Root segments of diseased plants were plated on potato dextrose agar. Cultures developed a white mycelium after 2 to 3 days, producing microconidia, macroconidia, and chlamydospores identified as Fusarium solani (1). After 15 days of incubation at 23 ± 2°C, reddish perithecia developed infrequently on root segments and adjacent substratum. Single-septate ascospores were hyaline and turned light brown with longitudinal striations at maturity. Microscopic measurements agreed with Nectria haematococca (1). To conduct Koch's postulates (two experiments, two treatments including inoculated and controls, 10 replicates per treatment), young rooted cuttings (6- to 12-month-old) were transferred to pots with a soilless mix and F. solani-colonized oat grains (10:1 vol/vol) and placed in growth chamber (25 to 28°C). First symptoms of the disease were leaf drooping and apex bending after 5 days. At approximately 9 days, leaves turned brownish, developed wilting from the tip downward, and plant death. Controls remained healthy. The fungus was reisolated, and perithecia of N. haematococca developed. F. solani has been reported causing wilt and sudden death in olive previously (2,3). To our knowledge, this is the first report of perithecial development associated with F. solani on olive. References: (1) C. Booth. The Genus Fusarium. CAB International, Wallingford, UK, 1971. (2) R. L. Munjal et al. Studies on diseases of olive in himachal pradesh. Pages 437-440 In: Improvement of Forest Biomass. Symposium Proceedings. Indian Society of Tree Scientists. P. K. Kosla, ed. Sdan, India, 1982. (3) B. A. Pérez et al. (Abstr.) Phytopathology 91 (suppl):S71, 2001.

[Supra-systolic elevation of the intra-cavernous pressure secondary to stimulation of the glans penis]. / Elévation suprasystolique de la pression intra-caverneuse secondaire à une stimulation du gland.

The role of the perineal muscles in human penile erections is still controversial. The authors investigated surface electromyographic activity of the ischiocavernous muscles together with intracavernous pressure recordings during pressure stimulations of the glans penis. Successive glans stimulations were associated with ischiocavernous muscle contractions and increases in intracavernous pressure reaching two- to fourfold the systolic blood pressure. High correlation coefficients were found between electromyographic and intracavernous pressure amplitudes. Voluntary contractions were accompanied by intracavernous pressure peaks of similar durations, and areas delineated by integrated electromyographic and intracavernous pressure curves showed very high correlation coefficients. Anaesthesia of the dorsal nerve resulted in dramatic reductions of muscle activity and intracavernous pressures in response to glans stimulation. These results suggest that the activity of the muscles in response to pressure stimulation of the glans penis is important to augment rigidity during vaginal penetration and intercourse due to their ability to increase intracavernous pressures.

[Considerable increase in the perineal arterial flow secondary to stimulation of the glans penis]. / Augmentation importante du débit artériel périnéal secondaire à une stimulation du gland.

The authors investigated the changes in human perineal blood flow by Doppler ultrasonography before, during, and after pressure stimulations (30,150 mm Hg) applied to the glans penis. We found a local increased blood flow response in 72% of 50 patients who consulted our center for erectile dysfunctions. Precise measurement analyses of 10 of these subjects allowed us to further characterize this response. Its latency ranged from 0.1 to 0.8 sec. and its duration from 4 to 13 sec. The blood flow increased up to 8 times the prestimulation level. This consistent increase in perineal blood flow showed much less variability than either the latency or duration of the response. The results of this study suggest that intravaginal pressures exerted on the glans penis during vaginal penetration and intercourse trigger an augmentation of blood flow into the corpora cavernosa. The reflex nature of this response is currently under investigation.