RESUMEN

The preservation of the world's biodiversity for future generations has been a global objective for many years, with the establishment of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species in 1964. However, the conservation of parasites is a more recent development and, due to the difficulty in obtaining data and studying some of the parasitic species, comes its own series of challenges. Using parasites of cyprinid hosts (one critically endangered, one endangered and three near threatened) collected from South Africa's Cape Fold freshwater ecoregion (CF) as a case study, this paper discusses the challenges and possible solutions for implementing a fish parasite conservation project. Novel data on the fish parasites (1819 metazoan parasite individuals, representing the Acanthocephala, Cestoda, Copepoda, Digenea, Monogenea and Nematoda) of the CF are provided from the five endemic hosts, Cheilobarbus serra (Peters, 1864), Labeobarbus seeberi (Gilchrist et Thompson, 1913), Pseudobarbus phlegethon (Barnard, 1938), Sedercypris calidus (Barnard, 1938), and Sedercypris erubescens (Skelton, 1974). Conservation statuses for selected parasite taxa are also proposed based on the conservation statuses of the fish hosts, according to the Conservation Assessment Methodology for Animal Parasites (CAMAP).

RESUMEN

BACKGROUND: South Africa has the highest prevalence of human immunodeficiency virus (HIV) infection in the world, and is commonly found in association with appendicitis. Atypical presentation of appendicitis in the presence of HIV infection makes clinical diagnosis of appendicitis unreliable, and inflammatory markers are commonly used as adjuncts. The aim of this study was ascertain the value of inflammatory markers in the diagnosis of appendicitis in patients with and without HIV infection. METHODS: Patients with acute appendicitis were studied and divided into HIV-infected and HIV-uninfected groups. Symptoms, and systemic and local signs were recorded. Appendiceal pathology was classified as simple or as complicated by abscess, phlegmon or perforation. Total white cell count (WCC) and C-reactive protein (CRP) were chosen as inflammatory markers. Findings were compared between the two groups. RESULTS: The study population consisted of 125 patients, of whom 26 (20.8 per cent) had HIV infection. Clinical manifestations did not differ statistically, and there was no difference in the incidence of simple or complicated appendicitis between the two groups. The mean CRP level was significantly higher in HIV-infected patients (194.9 mg/l versus 138.9 mg/l in HIV-uninfected patients; P = 0.049), and mean WCC (x109/L) was significantly lower (11.07 versus 14.17×109/l respectively; P = 0.010). CONCLUSION: Clinical manifestations and pathology did not differ between HIV-infected and HIV-uninfected patients with appendicitis, except that the WCC response was significantly attenuated and CRP levels were generally higher in the presence of HIV infection.

Asunto(s)

RESUMEN

Aspergillus clavatus poisoning is a neuromycotoxicosis of ruminants that occurs sporadically across the world after ingestion of infected feedstuffs. Although various toxic metabolites are synthesized by the fungus, it is not clear which specific or group of mycotoxins induces the syndrome. A. clavatus isolates were deposited in the culture collection of the Biosystematics Division, Plant Protection Research Institute, Agricultural Research Council during incidences of livestock poisoning (1988-2016). Six isolates were still viable and these plus three other South African isolates that were also previously deposited in the collection were positively identified as A. clavatus based on morphology and ß-tubulin sequence data. The cultures were screened for multiple mycotoxins using a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method. Twelve A. clavatus metabolites were detected. The concentrations of the tremorgenic mycotoxins (i.e., tryptoquivaline A and its related metabolites deoxytryptoquivaline A and deoxynortryptoquivaline) were higher than patulin and cytochalasin E. Livestock owners should not feed A. clavatus-infected material to ruminants as all the South African A. clavatus isolates synthesized the same compounds when cultured under similar conditions.

Asunto(s)

RESUMEN

Rhizoctonia is a major pathogen of potato causing substantial yield losses worldwide. Control of Rhizoctonia diseases is based predominantly on the application of fungicides. However, little is known about the fungicide response variability of different Rhizoctonia anastomosis groups associated with potato diseases in South Africa. A total of 131 Rhizoctonia isolates were obtained from potato growing regions of South Africa from 2012 to 2014 and evaluated for sensitivity to fungicides in vitro and in vivo. The fungicides comprised six chemical formulations and one bio-fungicide representing seven Fungicide Resistance Action Committee groups. All Rhizoctonia anastomosis groups were sensitive to tolclofos-methyl (EC50: 0.001 to 0.098 µg a.i. ml-1) and fludioxonil (EC50: 0.06 to 0.09 µg a.i. ml-1) and showed variation in sensitivity to pencycuron, iprodione, benomyl, and Bacillus subtilis QST 713. However, for azoxystrobin, Rhizoctonia isolates exhibited variable sensitivity ranging from sensitivity (EC50: <0.09 µg a.i. ml-1) to insensitivity with EC50 values exceeding 5 µg a.i. ml-1. In greenhouse and field trials, tolclofos-methyl and fludioxonil exhibited significantly greater control of stem and black scurf whereas azoxystrobin was the least effective. This work demonstrated variable sensitivity within and among anastomosis groups of R. solani and binucleate Rhizoctonia to different fungicides. Information on fungicide sensitivity of Rhizoctonia isolates is crucial in the development of effective Rhizoctonia control strategies and facilitates monitoring of fungicide insensitive isolates in the pathogen population.

Asunto(s)

RESUMEN

BACKGROUND: Rates of open reduction of intussusception were noted to be unacceptably high during an institutional internal audit. OBJECTIVES: To determine the impact of revised protocols to better select patients for pneumatic reduction (PR), and document associated morbidity and mortality, and the factors that affect the above. METHODS: Medical records of patients between 3 months and 3 years of age presenting to the Department of Paediatric Surgery at Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa, from 2007 to 2010 were reviewed. Determining factors, including duration of symptoms, admission C-reactive protein (CRP) level and weight, were analysed against clinical outcomes, notably PR, bowel resection, relook laparotomy and death. RESULTS: A total of 97 cases were suitable for inclusion. In 62 of these (63.9%), PR was attempted; this was successful in 32 cases (51.6%), giving an overall successful PR rate of 33.0%. In 7 of the 62 patients, a pneumoperitoneum was documented during the reduction attempt. Of the 65 patients who underwent surgery, 53 required intestinal resection and 12 had spontaneous or manual reduction. Ileostomy was necessary in 9 patients, and 7 required relook laparotomy. The overall mortality rate was 9.1%. Averages of 'determining factors' assessed against clinical outcome were as follows: mean weight (standard deviation (SD)) 7.4 (4.3) kg, mean duration of symptoms (DOS) 3.0 (SD 2.2) days, and admission CRP level 50.9 mg/L (range 1 - 249.3). Prolonged DOS and a raised CRP level predicted a poor outcome. CONCLUSION: Despite marked improvements in management and PR outcomes, intussusception remains associated with significant morbidity and mortality. Prolonged DOS and an elevated CRP predict worse outcomes. The use of these markers in association with clinical factors may assist management decisions, specifically with regard to operative or non-operative management. Awareness and education are key to prompt presentation and early diagnosis. Well-defined protocols introduced at all points of contact ensure early recognition and resuscitation as well as prompt referral for definitive management.

RESUMEN

A survey of anastomosis groups (AG) of Rhizoctonia spp. associated with potato diseases was conducted in South Africa. In total, 112 Rhizoctonia solani and 19 binucleate Rhizoctonia (BNR) isolates were recovered from diseased potato plants, characterized for AG and pathogenicity. The AG identity of the isolates was confirmed using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA. R. solani isolates recovered belonged to AG 3-PT, AG 2-2IIIB, AG 4HG-I, AG 4HG-III, and AG 5, while BNR isolates belonged to AG A and AG R, with frequencies of 74, 6.1, 2.3, 2.3, 0.8, 12.2, and 2.3%, respectively. R. solani AG 3-PT was the most predominant AG and occurred in all the potato-growing regions sampled, whereas the other AG occurred in distinct locations. Different AG grouped into distinct clades, with high maximum parsimony and maximum-likelihood bootstrap support for both R. solani and BNR. An experiment under greenhouse conditions with representative isolates from different AG showed differences in aggressiveness between and within AG. Isolates of AG 2-2IIIB, AG 4HG-III, and AG R were the most aggressive in causing stem canker while AG 3-PT, AG 5, and AG R caused black scurf. This is the first comprehensive survey of R. solani and BNR on potato in South Africa using a molecular-based approach. This is the first report of R. solani AG 2-2IIIB and AG 4 HG-I causing stem and stolon canker and BNR AG A and AG R causing stem canker and black scurf on potato in South Africa.

RESUMEN

Garden rocket (Eruca sativa syn.: E. vesicaria subsp. sativa (Mill) Thell.) is an annual plant of the Brassicaceae grown for fresh consumption as a salad vegetable. During winter (May to July) of 2013 and 2014 in South Africa, typical symptoms of white rust were observed in two commercial crops (each ~0.5 ha) of the garden rocket cv. Rucola coltivata in Centurion, Gauteng Province, at 33 and 80% incidence, respectively. Symptomatic leaves were deposited in the National Collection of Fungi, Plant Protection Research Institute, Agricultural Research Council, Pretoria, South Africa (PREM 61073). Early infections appeared as white to cream, blister-like sori on the lower leaf surfaces, and pale yellow lesions on the corresponding upper leaf surfaces. Later stages of infection were characterized by coalescing of lesions into large, irregular, necrotic blotches and development of additional sori on the petioles and stems. Sporangiophores were hyaline, clavate or cylindrical, and measured 24 to 30 × 11 to 14 µm (n = 50). Sporangia developed in basipetal chains and were hyaline, globose or polyangular, and 15 to 20 µm (n = 100). Based on these morphological characters and the host plant, the pathogen was identified as Albugo candida (Pers.) Kunze (2). Genomic DNA was extracted using the DNeasy Plant Mini DNA extraction kit (Qiagen) from sori containing sporangia collected from naturally infected leaves, according to the manufacturer's specifications. The internal transcribed spacer (ITS) region of ribosomonal DNA (rDNA) and the cytochrome c oxidase subunit II (COX2) region were amplified and sequenced (1). The ITS (GenBank Accession No. KM588081) and COX2 (KM588082) sequences confirmed identity of the pathogen as A. candida with 100% homology to the corresponding sequences of several A. candida isolates, including DQ418503 for the ITS sequence and DQ418514 for the COX2 sequence, of a voucher specimen of A. candida on E. sativa (BPI 184870) from Pakistan. Inoculum was prepared by scraping sporangia from infected leaves of the cv. Rucola coltivata collected from the 2014 field and placing the material in sterilized, distilled water (SDW) for 12 h at 5°C to induce zoospore formation. Pathogenicity tests were performed by spraying a suspension of 1 × 105 sporangia/ml onto each of 10 5-week-old rocket seedlings of the cv. Rucola coltivata. Ten additional seedlings were inoculated similarly with SDW to serve as a control treatment. The plants were maintained at 12 to 15°C and 95% RH for 72 h (3) before being moved to a shaded greenhouse at 20 to 24°C and 90% RH. Control plants remained symptomless, whereas white rust symptoms similar to those observed in the original fields developed on leaves of inoculated seedlings 10 to 14 days later, demonstrating that A. candida was the causal agent of the disease on E. sativa. To our knowledge, this is the first report of A. candida infecting garden rocket in South Africa. References: (1) Y.-J. Choi et al. Mol. Phylogenet. Evol. 40:400, 2006. (2) K. Mukerji. Descriptions of Pathogenic Fungi and Bacteria No. 458. CMI, Kew, Surrey, UK, 1975. (3) M. J. Sullivan et al. Plant Dis. 86:753, 2002.

RESUMEN

The omnipresent fungal genus Alternaria was recently divided into 24 sections based on molecular and morphological data. Alternaria sect. Porri is the largest section, containing almost all Alternaria species with medium to large conidia and long beaks, some of which are important plant pathogens (e.g. Alternaria porri, A. solani and A. tomatophila). We constructed a multi-gene phylogeny on parts of the ITS, GAPDH, RPB2, TEF1 and Alt a 1 gene regions, which, supplemented with morphological and cultural studies, forms the basis for species recognition in sect. Porri. Our data reveal 63 species, of which 10 are newly described in sect. Porri, and 27 species names are synonymised. The three known Alternaria pathogens causing early blight on tomato all cluster in one clade, and are synonymised under the older name, A. linariae. Alternaria protenta, a species formerly only known as pathogen on Helianthus annuus, is also reported to cause early blight of potato, together with A. solani and A. grandis. Two clades with isolates causing purple blotch of onion are confirmed as A. allii and A. porri, but the two species cannot adequately be distinguished based on the number of beaks and branches as suggested previously. This is also found among the pathogens of Passifloraceae, which are reduced from four to three species. In addition to the known pathogen of sweet potato, A. bataticola, three more species are delineated of which two are newly described. A new Alternaria section is also described, comprising two large-spored Alternaria species with concatenate conidia.

RESUMEN

Since the first report of brown spot of potatoes (Solanum tuberosum) caused by Alternaria alternata (Fr.) Keissl in South Africa (3), disease intensity has steadily increased. No fungicides are registered for control of brown spot of potatoes in South Africa but growers attempt to control the disease with products registered for early blight, which include various QoI fungicides. Failure to control brown spot with QoI fungicides led to an investigation on putative development of resistance among A. alternata populations. In the summer of 2012, diseased leaves were collected from five potato growing regions. Isolations were made from the margin of brown spot lesions by plating surface disinfested tissue on V8 agar medium (200 ml V8 juice, 3 g CaCO3, 20 g agar). Plates were incubated at 25°C in darkness for 7 days, purified, and single-spore cultures transferred to fresh potato dextrose agar (PDA) plates. Identity of isolates was confirmed using conidial morphology and PCR amplification using species-specific primers AAF2 and AAR3 (1). Eight A. alternata isolates (PPRI 13607, 13608, 13609, 13610, 13611, 13612, 13613, and 13614) were obtained and screened for sensitivity to azoxystrobin in vitro by evaluating relative conidial germination on media amended with 0, 1.0, 2.5, 5.0, 10, 25, 50, 75, 85, and 100 µg of azoxystrobin per ml of media. The dose effect of the fungicide on germination and the EC50 of each isolate were computed using the probit analysis. Isolates were subjected to DNA extraction and the partial cytochrome b (cyt b) was amplified using primer pair CBF1 and CBR2 (2). PCR products were transformed into DH5α competent cells using a pGEM-T Easy vector. Both strands of the cloned fragments were sequenced using primers T7 and SP6 (4). Isolates PPRI 13611 and 13614 had low EC50 values of 0.11 and 0.23 µg/ml, respectively, and a mean EC50 of 0.17 µg/ml, showing their relative sensitivity to azoxystrobin. The other six isolates had EC50 values ranging from 51.88 to 114.92 µg/ml, and a mean EC50 of 71.60 µg/ml, showing their resistance to azoxystrobin. Sequence analysis of the partial cyt b gene showed strong association of resistance in isolates PPRI 13607, 13608, 13609, 13610, 13612, and 13613 to a base substitution resulting in an amino acid substitution at position 143 (G143A). Isolates PPRI 13611 and 13614 did not exhibit this mutation. Although resistance has been reported on other crops where QoI fungicides, including azoxystrobin, have been used to control different pathogens, this is the first report of resistance to a QoI fungicide in field isolates of A. alternata from potatoes in South Africa. Identification of resistance will help to explain failure to control this disease using QoI fungicides. Further monitoring of resistance to azoxystrobin and other QoI fungicides is warranted. References: (1) P. Konstantinova et al. Mycol. Res. 106:23, 2002. (2) Z. Ma et al. Pesticide Biochem. Phys. 77:66, 2003. (3) J. van der Waals et al. Plant Dis. 95:363, 2011. (4) E. Youssef et al. DNA Seq. 11:541, 2001.

RESUMEN

Black scurf and stem canker caused by Rhizoctonia solani Kühn (teleomorph: Thanathephorus cucumeris Frank Donk) are potato diseases of worldwide economic importance (4). R. solani consists of 13 anastomosis groups (AGs) of which AG 3-PT is considered the dominant causal agent of potato diseases globally (1,4). However, other AGs such as AG 2-1, 5, and 8 have been reported to cause potato diseases (1,4). In February 2013, potato stem samples (cv. Mondial) displaying dark brown lesions resembling those caused by Rhizoctonia stem canker were obtained from a commercial field in Limpopo Province, South Africa. Symptomatic tissue was disinfected with 1% NaOCl for 1 min, rinsed in sterile water, and 4-mm stem pieces excised from the margins of symptomatic tissues and plated on 2% water agar supplemented with 20 mg/l of chloramphenicol. Single hyphal tips taken from fungal isolates identified as R. solani based on morphological traits (3) were transferred to potato dextrose agar. DNA was isolated from the resulting cultures and ITS region of rDNA was sequenced as previously described (2). The resulting sequences of three of the isolates, Rh 81, Rh 82, and Rh 83 (KF712285, KF712286, and KF712287), were 99% similar to those of AG 4 HG-III found in GenBank (DQ102449 and AF354077). Therefore, based on molecular methods, these three isolates were identified as R. solani AG4 HG-III. To determine pathogenicity of the AG4 HG-III isolates, certified disease free mini-tubers (Generation 0, cv. Mondial, produced in tunnels) were used in pot trials. PDA plugs of each isolate were added to 10 g of barley grains, which had been sterilized by autoclaving for two consecutive days at 121°C for 30 min, and were incubated for 14 days until fully colonized. Ten colonized barley grains were placed 10 mm above each mini-tuber planted in 5l pots containing sterile potting mixture of sand:clay:pinebark (1:1:1). Ten tubers were inoculated with each isolate. Uninoculated, sterile barley grains were applied to the control treatment. Mini-tubers were grown in a greenhouse maintained at 22°C with light for a 12 h day. After 7 weeks, five plants for each isolate were destructively sampled and assessed for stem canker symptoms. At 120 days after sowing, the remaining five plants per treatment were assessed for blemishes on progeny tubers. The stem canker incidences of plants inoculated with Rh 81, Rh 82, and Rh 83 were 25, 25, and 50%, respectively, whereas no symptoms were observed in control plants. Sclerotia formation and blemishes were not observed on any of the progeny tubers, which might indicate that these strains are only able to infect stems, or that environmental conditions were not suitable for tuber blemish or black scurf development. R. solani AG4 HG-III was consistently re-isolated from symptomatic stems displaying brown lesions, and the identity of the re-isolates were confirmed by molecular tests as previously described, thereby fulfilling Koch's postulates. To our knowledge, this is the first report of R. solani AG4 HG-III causing stem canker on potato in South Africa and worldwide. Knowledge of which AGs are present in crop production systems is important when considering disease management strategies such as crop rotation and fungicide treatments (3). References: (1) C. Campion et al. Eur. J. Plant. Pathol. 109:983, 2003. (2) N. Muzhinji et al. Plant Dis. 98:570, 2014. (3) L. Tsror. J. Phytopathol. 158:649, 2010. (4) J. W. Woodhall et al. Plant. Pathol. 56:286, 2007.

RESUMEN

Rhizoctonia solani consists of 13 anastomosis groups (AGs) designated AG1 to 13. AG3-PT is considered the predominant AG in potatoes (4) and is associated with quantitative and qualitative yield losses. Qualitative losses are typically associated with the tuber blemish disease, black scurf. However, atypical tuber blemishes such as elephant hide consisting of corky lesions on the tuber surface (2) have also been attributed to Rhizoctonia. Such atypical blemishes are not considered specific to Rhizoctonia, making direct-cause effect estimates difficult (1). Koch's postulates for the elephant hide symptom and R. solani AG3-PT have not been completed. Recently, growth cracking and scab lesions were observed on potato tubers in South Africa and attributed to a new Streptomyces species (3). These lesions and cracks were similar to elephant hide symptoms attributed to R. solani AG3-PT. Therefore, the cause of the elephant hide symptom in South Africa was investigated further. Symptoms of elephant hide and cracking have been observed on tubers from the Eastern Free State, KwaZulu-Natal, Limpopo, Mpumalanga, North-Eastern Cape, Northern Cape, North West, Sandveld, and Western Free State growing regions. In 2012, three samples of potato tubers (cv. BP1) with elephant hide and cracking were selected for analysis. These samples were collected from Clanwilliam in the Sandveld potato growing region. Tubers were surface sterilized with 1% NaOCl; sections of affected tissue were excised and plated onto potato dextrose agar (PDA). Rhizoctonia-like colonies were identified and after further sub-culturing on PDA, three representative isolates (Rh3, Rh4, and Rh6) of R. solani from each sample were obtained. For each isolate, genomic DNA was extracted and the rDNA ITS region sequenced using ITS1-F and ITS4 (2). The resulting sequences (KF234142, KF234143, and KF234144) were at least 98% identical to other AG3-PT sequences on GenBank (JX27814 and KC157664). To confirm Koch's postulates, pathogenicity tests were conducted with the three isolates. PDA plugs of each isolate were added to 10 g of barley grains which were incubated for 14 days until fully colonized. The barley grains were then used to inoculate disease-free mini-tubers (cv. BP1) in 5l pots containing a sand-clay-pine bark mixture (1:1:1 ratio). Potato plants inoculated with sterile barley grains served as controls. Plants were held for 120 days in a greenhouse at 22°C with light for 12 h a day. Incidence of the elephant hide symptom for isolates Rh3, Rh4, and Rh6 was 58%, 33%, and 37.5%, respectively. Growth cracking and black scurf were also observed with each isolate. R. solani AG3-PT was successfully re-isolated from symptomatic tubers, confirming Koch's postulates. This is the first report of R. solani AG3-PT causing elephant hide in potato tubers in South Africa. Elephant hide caused by R. solani AG3-PT has been reported in tubers from France (2) and the United Kingdom (3), but Koch's postulates were not proven. In this study, Koch's postulates were proven for R. solani AG3-PT causing scab or elephant hide symptom and cracking in potato tubers. R. solani AG3-PT should thus be considered in addition to Streptomyces as a cause of this symptom and control strategies should also consider R. solani AG3-PT. References: (1) G. J. Banville et al. Pages 321-330 in: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control, B. Sneh et al., eds. Kluwer Academic Publishers, Dordrecht, The Netherlands, 1996. (2) M. Fiers et al. Eur. J. Plant. Pathol. 128:353, 2010. (3) R. Gouws and A. McLeod. Plant Dis. 96:1223, 2012. (4) J. W. Woodhall et al. Eur. J. Plant. Pathol. 136:273, 2013.

RESUMEN

A sheep farmer provided a maize-based brewer's grain (mieliemaroek) and bales of Eragrostis curvula hay to ewes and their lambs, kept on zero-grazing in pens. The 'mieliemaroek' was visibly mouldy. After 14 days in the feedlot, clinical signs, including generalised weakness, ataxia of the hind limbs, tremors and recumbency, were noticed. Six ewes died within a period of 7 days. A post mortem examination was performed on 1 ewe. The carcass appeared to be cachectic with mild effusions into the body cavities; mild lung congestion and pallor of the kidneys were observed. Microscopical evaluation revealed nephrosis and birefringent oxalate crystals in the renal tubules when viewed under polarised light. A provisional diagnosis of oxalate nephrosis with subsequent kidney failure was made. Amongst other fungi, Aspergillus niger was isolated from 'mieliemaroek' samples submitted for fungal culture and identification. As A. niger is known to synthesise oxalates, a qualitative screen to detect oxalic acid in the mieliemaroek and purified A. niger isolates was performed using high-performance liquid chromatography (HPLC). Oxalic acid was detected, which supported a diagnosis of soluble oxalate-induced nephropathy.

Asunto(s)

RESUMEN

Rhizoctonia disease (black scurf of tubers and stem canker) of potato (Solanum tuberosum L.) caused by Rhizoctonia solani Kühn was first recorded in South Africa in 1918 (3). Although the sclerotial form on tubers is one of the most common potato diseases in the country, it is not known which anastomosis groups (AGs) of R. solani are involved. Between 1999 and 2001, R. solani was isolated from 28 plant and 56 soil samples collected in 7 (Eastern Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, Northern Cape, and Sandveld) of the 14 potato-production regions of South Africa and screened for hyphal anastomosis with tester strains of R. solani AG-1 to AG-10 according to Carling et al. (1). Of the 411 isolates from tubers with black scurf symptoms, 408 were AG-3 and three were AG-5. Symptomless tubers yielded two AG-3 isolates and three AG-5 isolates. Of 39 isolates from symptomatic stems and roots, 32 were AG-3, five were AG-4, and two were AG-5. Of the 127 isolates obtained from soil, 86, 28, 7, 3, and 3 were AG-3, AG-4, AG-5, AG-7, and AG-8, respectively. More than one AG was isolated from five of the seven regions. Virulence of 40 isolates representative of the above AGs was determined in triplicate on sprouts growing from seed tubers of potato cultivar Up-to-Date in a sand/soil mixture as described by Carling and Leiner (2) but using cultures grown in cornmeal/sand instead of colonized agar disks as inoculum. Damage to sprouts (lesions, girdling, and death) was assessed after 28 days at 16 to 28°C according to the 0 to 4 rating scale (2). Chi-square analysis of the data indicated that AG-3 was the most virulent, with isolates from sclerotia on tubers and lesions on stems more aggressive than those from symptomless tubers or soil. AG-4 and AG-5 caused significantly less disease than AG-3, but none of the AG-7 and AG-8 isolates showed any virulence to potato sprouts. References: (1) D. E. Carling et al. Phytopathology 77:1609, 1987. (2) D. E. Carling and R. H. Leiner. Phytopathology 80:930, 1990. (3) E. M. Doidge. S. Afr. Fruit Growers 5:6, 1918.

RESUMEN

Cultivation of lisianthus (Eustoma grandiflorum (Raf.) Shinn.) is a minor industry in South Africa, with only a few growers producing the crop commercially. Commercial production at a location in Gauteng Province is hampered by rotting of the crowns and roots of plants that result in mortality of as much as 22% of the plants. At advanced stages of infection, the crowns of affected plants characteristically are covered with masses of fusoid, curved hyalophragmospores. Crowns and roots of symptomatic plants that were submitted by the grower in January 2003 were surface disinfested by immersing for 2 min in a 3% solution of sodium hypochlorite, and segments excised from the plant tissue were plated on potato dextrose agar supplemented with 50 mg l-1 of rifampicin. Fusarium solani (Mart.) Appel & Wollenw. (1), was consistently and exclusively isolated from the segments. Teleomorph Nectria haematococca Berk. & Broome, commonly developed in culture after incubation for 4 to 6 weeks, although no sexual structures were observed on infected plants. A spore suspension containing 104 micro- and macroconidia ml-1 was prepared for each of two single-conidial isolates of F. solani. Using a 0.8-mm-diameter hypodermic needle, 100 µl of each suspension was injected subepi-dermally into the crown of each of three 1-month-old disease-free lisian-thus plantlets (cv. Texas Blue Bell) growing in 500-ml plastic pots filled with sterilized vermiculite. In addition, each suspension was incorporated at 2% (vol/vol) into three pots with sterile vermiculite, and a plantlet was planted in each pot. Control plantlets were treated similarly, but with sterile distilled water. All inoculated plantlets developed crown rot and wilted within 2 weeks while maintained at 28°C in a greenhouse, regardless of mode of inoculation, and F. solani was readily reisolated from their crowns and roots. Control plantlets remained symptomless and did not yield F. solani. Crown and root infection of lisianthus by F. solani has been described (2,3), but to our knowledge, this is the first report of the disease in South Africa. References: (1) P. E. Nelson et al. Fusarium species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park. 1983. (2) J. J. Taubenhaus and W. N. Ezekiel. Phytopathology 24:19, 1934. (3) S. Wolcan et al. Plant Dis. 85:443, 2001.

RESUMEN

Studies in England, USA and Australia, have shown that the working hours of female dentists do not differ significantly from the working hours of their male counterparts, until they have children. The purpose of this study was to establish whether the same phenomenon exists in South Africa and to compare working patterns of South African male and female dentists regarding nature of practice/employment, location of practice, work satisfaction and breadwinner status. Questionnaires were sent to 285 female dentists, selected by their first name in the SAMDC register. An equal number of questionnaires were sent to male dentists, selected according to the proportional random sampling technique. The total response achieved was 35.8 per cent. The female dentists' working hours showed a distinct drop as soon as they started a family (from 86 per cent, practising more than 35 hours per week, to 34 per cent) while the male dentists' hours remained unchanged (90 per cent). The fact that so many more male dentists (81 per cent) than female dentists (19.6 per cent) are primary breadwinners, explains why such a high percentage of female dentists can afford to work part-time. The majority of both male (89.7 per cent) and female (70 per cent) dentists are in private practice. However, a considerably larger percentage of females work for a salary in State clinics and at Universities. This study shows that gender, breadwinner status and the presence and age of children have a marked influence on the working patterns of South African dentists.

Asunto(s)

RESUMEN

The purpose of this in vitro investigation was to determine the shear bond strength (SBS) of composite resin bonded to deciduous (D) and permanent (P) dentine using the Scotchbond Multi-Purpose system (SMP, 3M). Twenty extracted, sound permanent human molar teeth (Group A) and twenty carious primary molars (Group B) were used in this study. All samples were ground wet on a polishing machine (220 grit) in order to expose superficial buccal dentine surfaces. Dentine surfaces were treated with the Scotchbond Multi-Purpose system according to manufacturers instructions. Z100 composite stubs were bonded to the treated dentine surfaces using a silicone rubber split mould. Bonds were stressed to failure in an Instron using a shear load. Data were calculated and analysed statistically (Student-t test). The mean SBS in MPa were 17.12 +/- 3.71 to deciduous and 23.60 +/- 2.47 to permanent dentine. SMP demonstrated a statistical higher (p < 0.01) shear bond strength to permanent than to deciduous dentine.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

Recognition of metal cations by biological systems can be compared with the geochemical criteria for isomorphous replacement. Biological systems are more highly selective and much more rapid. Methods of maintaining an optimum concentration, including storage and transfer for the essential trace elements, copper and iron, used in some organisms are in part reproducible by coordination chemists while other features have not been reporduced in models. Poisoning can result from a foreign metal taking part in a reaction irreversibly so that the recognition site or molecule is not released. For major nutrients, sodium, potassium, magnesium and calcium, there are similarities to the trace metals in selective uptake but differences qualitatively and quantitatively in biological activity. Compounds selective for potassium replace all the solvation sphere with a symmetrical arrangement of oxygen atoms; those selective for sodium give an asymmetrical environment with retention of a solvent molecule. Experiments with naturally occurring antibiotics and synthetic model compounds have shown that flexibility is an important feature of selectivity and that for transfer or carrier properties there is an optimum (as opposed to a maximum) metal-ligand stability constant. Thallium is taken up instead of potassium and will activate some enzymes; it is suggested that the poisonous characteristics arise because the thallium ion may bind more strongly than potassium to part of a site and then fail to bind additional atoms as required for the biological activity. Criteria for the design of selective complexing agents are given with indications of those which might transfer more than one metal at once.

Asunto(s)

Asunto(s)