Showing papers by "CABI published in 1999"

DNA extraction and PCR amplification method suitable for fresh, herbarium-stored, lichenized, and other fungi

Abstract: This paper presents a DNA extraction method suitable for fresh, herbarium-stored, lichenized and other fungal specimens. The method is fast and reliable, comparatively inexpensive and is suitable for obtaining PCR amplification quality DNA from large numbers of samples in a short time. The method has been tested with over 300 samples ofAscochyta, Phyllosticta, Ramalina, Parmelia andPhysconia. Amplifiable fungal DNA was extracted from pure cultures, leaf lesions, whole thalli and dissected “only-fungal” sections of lichenized fungi. In addition, the method has proved suitable for use with herbarium specimens of both lichenized and non-lichenized fungi, stored as dried pure cultures or dried infected plant material.

Plant community dynamics in a calcareous grassland under climate change manipulations

Abstract: This study investigates the effects of field manipulations of local climate to determine the potential impact of climate change on plant community dynamics in a calcareous grassland. The experimental site is located in a grassland at the Wytham estate, Oxfordshire, UK. The one hectare study area is within a 10 ha abandoned arable field on Jurassic corallian limestone. Two climate change scenarios were used: warmer winters with increased summer rainfall and warmer winters with summer drought. Plant cover and species richness were significantly increased in plots receiving supplemented summer rainfall, while the amount of litter was significantly reduced. Litter formation was significantly increased by winter warming and drought. The responses of the plant community to the climate manipulations were related to the life-history attributes of the dominant species. Seedling recruitment was limited by microsite availability, which also varied in the different climate manipulations. The results are discussed in terms of successional dynamics. They suggest that warmer winters may delay succession, as gap formation in the sward will provide sites for colonisation of annuals, thereby enabling their persistence in the sward. Under wetter conditions during summer, perennial grasses tend to close the sward, thereby inhibiting the establishment of later successional species.

Positive effects of an arbuscular mycorrhizal fungus on aphid life history traits

Abstract: Two generations of two aphid species (Myzus ascalonicus and M. persicae) were reared on Plantago lanceolata plants, with and without root colonization by the arbuscular mycorrhizal fungus, Glomus intraradices. Life history traits of the aphids measured were nymphal development time, teneral adult weight, growth rate, total fecundity, adult longevity and duration of post-reproductive life. For both aphids in both generations, mycorrhizal colonization increased aphid weight and fecundity, while other traits were unaffected. The increases were consistent between generations. In a second experiment, M. persicae was reared on plants with and without the fungus, under varying N and P regimes. The results of N addition were inconclusive because there was high aphid mortality. However, under P supplementation, positive effects of the mycorrhiza on aphid growth were seen at low and medium P levels, while at high P levels these effects disappeared. The positive effects of mycorrhizal colonization reported here are contrary to the majority of previous studies with chewing insects, which have reported negative effects. A number of possible mechanisms for this apparent discrepancy are discussed.

Effect of island geological age on the arthropod species richness of Azorean pastures

Abstract: Species richness of six pasture arthropod assemblages (total arthropod species, total herbivore species, sucking and chewing herbivores, total predatory species and spiders) were regressed against several geographical variables (area, distance from the nearest mainland, maximum elevation and geological age of the islands) of three Azorean islands (S. Maria, Terceira and Pico). The species were sampled by the fixed-quadrat size sampling method and the results obtained are consistent with the geological age hypothesis, i.e. the species richness of the six indigenous arthropod assemblages increases with the geological age of the islands, both at local and regional scales. Higher values of indigenous and endemic species richness were consistently found on the older island (S. Maria), and the lowest values on the most recent island (Pico). Moreover, when considering the age of Faial (an older island probably once connected with Pico) as a estimate of the age of Pico, correlations between species richness and island age were improved, thereby strengthening the relationship. The older island (S. Maria) has more specialized herbivores and a greater proportion of herbivores in relation to predatory arthropods. Ecological and biogeographical studies in the Azores should take into account the effects of the time each island has been available for colonization and evolution.

Genetic diversity of Ganoderma in oil palm plantings

Abstract: Isolates of Ganoderma spp. associated with basal stem rot of oil palm were obtained by sampling from two palm plantings in Malaysia. Members of a subset of these were compared using a combination of somatic incompatibility and molecular genetic analyses. Incompatibility interactions between heterokaryons in culture indicated that Ganoderma generally occurred as numerous distinct strains, with compatible strains usually confined to individual palms. Analysis of restriction fragment length polymorphisms (RFLPs) in presumptive mitochondrial DNA (mtDNA) revealed heterogeneity among isolates from neighbouring palms, and from within individual palms. The combination of mtDNA variability and somatic incompatibility suggests that Ganoderma BSR does not spread by direct root-to-root contact between palms. The results may indicate infection spread through basidiospore dispersal or through contact with a heterogeneous long-term residual inoculum in debris.

Isolation, Characterization, and Avenacin Sensitivity of a Diverse Collection of Cereal-Root-Colonizing Fungi

Abstract: A total of 161 fungal isolates were obtained from the surface-sterilized roots of field-grown oat and wheat plants in order to investigate the nature of the root-colonizing fungi supported by these two cereals. Fungi were initially grouped according to their colony morphologies and then were further characterized by ribosomal DNA sequence analysis. The collection contained a wide range of ascomycetes and also some basidiomycete fungi. The fungi were subsequently assessed for their abilities to tolerate and degrade the antifungal oat root saponin, avenacin A-1. Nearly all the fungi obtained from oat roots were avenacin A-1 resistant, while both avenacin-sensitive and avenacin-resistant fungi were isolated from the roots of the non-saponin-producing cereal, wheat. The majority of the avenacin-resistant fungi were able to degrade avenacin A-1. These experiments suggest that avenacin A-1 is likely to influence the development of fungal communities within (and possibly also around) oat roots.

Development of strategies for the incorporation of biological pesticides into the integrated management of locusts and grasshoppers

Abstract: Effective biological pesticides based on oil formulation of deuteromycete fungal spores have been developed for use against locusts and grasshoppers. The isolate IMI 330189 of Metarhizium anisopliae (flavoviride) var. acridum has been regis- tered, extensively field tested and its operating characteristics explored. It should form an powerful component technology in the integrated management of locust and grasshopper pests. 2 The particular advantages of Metarhizium anisopliae were found to be efficacy and persistence, low vertebrate toxicity, little environmental impact, conservation of natural enemies and potential for recycling. Additional socio-economic advan- tages include the possibility of local production, ease of disposal and versatility in use. The principal disadvantages relate to operating characteristics such as slower speed of kill and slightly greater lability in storage than chemical pesti- cides. 3 Strategies are being developed to integrate biological control agents into locust and grasshopper management schemes; for Metarhizium the accent is placed on: (i) treating the pest before it invades crops and (ii) situations with a high pre- mium on environmental issues. 4 For some pest situations, fast-acting chemical pesticides will still be necessary for crop protection. 5 A cheaper biological agent, such as Nosema locustae, with the capacity to persist in the pest insect population would be useful. Research is recommended on the long-term impact of Nosema in Africa. 6 An evaluation of the utility of the manual destruction of egg pods leads to the conclusion that we should consider the possibility of importing egg parasitoids, such as Scelio parvicornis from Australia, into Africa. 7 Further development work is needed to clarify the economics and politics of lo- cust and grasshopper control; to improve the regulatory framework for biopesti- cides; to inform key decision makers of the availability and potential of Metarhizium; and to implement the bio-intensive IPM strategies described.

Operational and economic analysis of a West African pilot-scale production plant for aerial conidia of Metarhizium spp. for use as a mycoinsecticide against locusts and grasshoppers.

Abstract: Aerial conidia of Metarhizium anisopliae (flavoviride) var. acridum strain IMI 330189 used for the inundative biological control of grasshoppers and locusts in sub-Saharan Africa are produced in a purpose-built facility at the International Institute for Tropical Agriculture in Benin using a standard, two-stage mass-production system. The yields average 31.1 g of dry conidia powder/kg of rice substrate, the production capacity is 300-350 kg of conidia/year and the production costs are estimated at US$21/100 g (the recommended dose for 1 ha). The production process parameters vary within narrow limits established during optimization, but the yield is characterized by a high level of variation over time. The incubation period and temperature are identified as key factors, although they account for less than 40% of the yield variation. The variation in conidial viability and contamination are correlated with several parameters, but none can adequately explain this variation. The handling time, a principal li...

Diversity and abundance of insect herbivores foraging on seedlings in a rainforest in Guyana

Abstract: Summary 1. Free-living insect herbivores foraging on 10 000 tagged seedlings representing five species of common rainforest trees were surveyed monthly for more than 1 year in an unlogged forest plot of 1 km2 in Guyana. 2. Overall, 9056 insect specimens were collected. Most were sap-sucking insects, which represented at least 244 species belonging to 25 families. Leaf-chewing insects included at least 101 species belonging to 16 families. Herbivore densities were among the lowest densities reported in tropical rainforests to date: 2.4 individuals per square metre of foliage. 3. Insect host specificity was assessed by calculating Lloyd’s index of patchiness from distributional records and considering feeding records in captivity and in situ. Generalists represented 84 and 78% of sap-sucking species and individuals, and 75 and 42% of leaf-chewing species and individuals. In particular, several species of polyphagous xylem-feeding Cicadellinae were strikingly abundant on all hosts. 4. The high incidence of generalist insects suggests that the Janzen–Connell model, explaining rates of attack on seedlings as a density-dependent process resulting from contagion of specialist insects from parent trees, is unlikely to be valid in this study system. 5. Given the rarity of flushing events for the seedlings during the study period, the low insect densities, and the high proportion of generalists, the data also suggest that seedlings may represent a poor resource for free-living insect herbivores in rainforests.

Direct and indirect effects of climate change on St John's wort, Hypericum perforatum L. (Hypericaceae).

Abstract: We report results from a continuing, long-term field experiment addressing biotic responses to climatic change in grasslands. We focus on effects of summer precipitation (enhanced rainfall, drought, control) and winter ground temperatures (warming, control) on growth, reproduction and herbivory in St John's wort, Hypericum perforatum L. Both winter warming and summer rainfall regimes modified performance and interactions of H. perforatum, particularly those with herbivorous insects. Winter warming had positive effects, with earlier initiation of plant growth and reduced damage by gall-forming and sucking insects in spring, but also had strong negative effects on plant height, flowering, and reproduction. Summer drought reduced reproductive success, but even severe drought did not affect plant growth or flowering success directly. Rather, summer drought acted indirectly by modifying interactions with herbivorous insects via increased vulnerability of the plants to herbivory on flowers and capsules. Overall, the effects of summer precipitation were expressed mainly through interactions that altered the responses to increased winter temperatures, particularly as summer drought increased. The field site, in Oxfordshire, UK, is near the northern limit of distribution of the species, and the experiment tested probable responses of H. perforatum as climates shift towards those more typical of the current center of the distribution of the species. However, if climates do change according to the projected scenarios, then H. perforatum is unlikely to fare well near its northern boundary. Increased winter temperatures, particularly if accompanied by increased summer drought, will probably render this species even less abundant in England than at present.

The chemotherapy of rodent malaria. LVI. Studies on the development of resistance to natural and synthetic endoperoxides.

Abstract: Chloroquine-sensitive Plasmodium berghei N and chloroquine-resistant P yoelii ssp NS were exposed to selection pressure, in the '2% relapse technique', from artemisinin, artesunate, a bicyclic, synthetic endoperoxide Ro 41-3823 (an analogue of arteflene) or Fenozan B07, a synthetic 1,2,4-trioxane endoperoxide Whereas resistance against artemisinin did develop to a moderate level in both parasites, only a low level of resistance or none developed to the other compounds, and resistant parasites readily lost resistance once drug-selection pressure was withdrawn The relevance of these observations and the experience of other investigators are discussed in relation to the possible risk that resistance may be developed in nature once endoperoxides are deployed widely against multidrug-resistant P falciparum

Biogeography of the Cinara cupressi complex (Hemiptera : Aphididae) on Cupressaceae, with description of a pest species introduced into Africa

Abstract: In recent decades, aphids identified as Cinara cupressi (Buckton) have seriously damaged commercial and ornamental plantings and native stands of Cupressus, Juniperus, Widdringtonia and other Cupressaceae in Africa, Italy, Jordan, Yemen, Mauritius and Colombia. Aphids currently identified as Cinara cupressiappear to belong to a species complex. This work was undertaken to identify the pest, its likely area of origin and any specific natural enemies, to facilitate a biological control programme. The biogeography of the species complex was studied using morphometric analysis of specimens from all the major regions where they have been collected, and analysis of host-plant ranges, parasitoid records and host association information. The cause of tree damage is shown to be an unnamed species, here described as C. (Cupressobium) cupressivora Watson & Voegtlin sp. n., which probably originated on Cupressus sempervirens in a region from eastern Greece to just south of the Caspian Sea. The remainder of the complex, Cinara cupressisensu lato, apparently consists of three morphologically similar species (C. sabinae(Gillette & Palmer) and C. cupressi (Buckton), probably originating in North America, and an unidentified species). There is insufficient data available to separate these taxa, or to determine the status of C. canadensis Hottes & Bradley, so C. sabinae and C. canadensis are left in synonymy under C. cupressi (Buckton). Lachniella tujae del Guercio and L. juniperi signata del Guercio, thought to be part of the C. cupressi complex, were found to be junior synonyms of C. tujafilina (del Guercio); these new synonymies are proposed and lectotypes of L. tujae and L. juniperi signataare designated.

Formulation of vegetable fat pellets with pheromone and Beauveria bassiana to control the larger grain borer, Prostephanus truncatus (Horn)

Abstract: The use of hydrogenated rapeseed oil as a carrier for conidia of the entomopathogenic fungus Beauveria bassiana (Bals) Vuill was investigated as part of a research programme on the control of the larger grain borer, Prostephanus truncatus (Horn). Melting the oil, which is solid at temperatures below 32 °C, allows the incorporation of materials such as aggregation pheromones and conidia; sudden cooling produces solid fat pellets. In attraction tests conducted with pellets containing P truncatus aggregation pheromone, significantly higher numbers of beetles were attracted to pellets containing pheromone at a concentration of 4 ml litre−1 compared to control pellets for at least four weeks when held in Petri dishes in the laboratory and for at least six weeks when pellets held in insect traps were exposed to outside conditions. The attraction was retained over a period of storage in glass bottles; pellets stored in the freezer or incubator (at −10 °C or 27 °C) attracted beetles according to the pheromone level for the duration of the work (14 and 13 months respectively). When pheromones and conidia were incorporated into the same pellets they could be stored in a freezer or refrigerator retaining over 80% viability after 51 weeks; those stored in an incubator at 27 °C showed significantly lower germination at 20.7–27.2% after the same time. There was an indication that the pheromone caused a slight reduction in the viability of conidia, although this may have been just a slight delay in the speed of germination. Rapid dose transfer from pellets with conidia with and without the addition of pheromone was demonstrated. Insects were exposed to pellets for 24 hours and 96–100% mortality was observed in treatments containing conidia within six days of exposure. © 1999 Society of Chemical Industry

Spatial and temporal patterns of seed attack and germination in a large-seeded neotropical tree species.

Abstract: It has long been argued that seed dispersal enhances recruitment in tropical trees by allowing offspring to `escape' strong density/distance-dependent attack by insects, pathogens and rodents. Here we examined the effects of canopy openness and parent-offspring distance upon the frequency and timing of Chlorocardium rodiei seed attack and germination within a 15-ha plot of Guyanan tropical rain forest. Seeds were artificially dispersed beneath parent trees, in the understorey away from trees and in gaps. Analysing our data from an 85-week period of regular monitoring, we found that the main spatial gradients, canopy openness and distance to nearest adult conspecific, do not lead to differences in the final number of seeds attacked by infesting scolytid beetles or rodents. The timing of beetle attack, however, varied along the distance gradient and this difference affords seeds at further distances a `window' in which to germinate and produce a seedling before attack. Canopy openness was not a good predictor of rooting success, but distance was strongly associated with root and shoot formation success and the mean time to shoot formation. There was a strong negative effect of distance on the likelihood of a seed being colonised by scolytid beetles prior to removal by rodents and shoot failure was strongly associated with prior infestation. We believe these results bring a key point to bear on the well-established notion of distance-dependent attack on seeds in tropical rainforests, viz. that seed characteristics (size, germination syndrome) and the timing of attack may be more important in explaining patterns of early seedling recruitment than distance. Our studies suggest that advantages accrued through dispersal in species like Chlorocardium will depend heavily on the `race' between seed germination and attack. In the case of Chlorocardium, the `race' can be lost at considerable distances due to its prolonged dormancy and the temporal fluctuations in fruitfall and rainfall which influence attack and germination. The results presented here suggest that the lag between seed attack and germination in tropical trees can regulate the influence of parent-offspring distance on cohort recruitment at this life history stage.

The chemotherapy of rodent malaria. LVII. Drug combinations to impede the selection of drug resistance, Part 1: Which model is appropriate?

Abstract: The principle has finally been accepted that, whenever possible, antimalarial drugs should be deployed in appropriate combinations in endemic areas, in order to minimize the inevitability that monotherapy will, probably sooner than later, select populations of drug-resistant parasites. Which laboratory models can predict the combinations of old or novel compounds that are likely to be of practical value in minimizing this risk? Very few relevant data on the use of Plasmodium falciparum in vitro have been published. Most research has been carried out with one or other strain of chloroquine-sensitive P. berghei or with chloroquine-resistant P. yoelii ssp. NS in mice. The two most widely used procedures to select for resistance are the 'serial technique' (ST), in which drug selection pressure in vivo is gradually increased, and the '2% relapse technique' (2%RT), in which a single, large drug dose is applied at the time of each passage. Both procedures have been used to demonstrate the ability of pairs of drugs (e.g. sulfadoxine with pyrimethamine, cycloguanil with dapsone, pyrimethamine or sulphonamides with chloroquine, mepacrine or mefloquine) or triple combinations (e.g. sulfadoxine-pyrimethamine with chloroquine, mefloquine or pyronaridine) to delay the development of resistance. The relative merits of the ST and 2%RT are discussed and the data obtained by these procedures are compared with the results of deploying drug combinations in man, especially against multidrug-resistant P. falciparum. It is concluded that, even though the rodent malaria models are imperfect, no better alternatives are available at present with which to predict the value of antimalarial combinations for the protection of the individual components. The 2%RT is considered to be the procedure of first choice.

Temperature and plant nutrient effects on the development, survival and reproduction of Cinara sp. nov., an invasive pest of cypress trees in Africa

Abstract: Cinara sp. nov., previously identified as Cinara cupressi (Buckton) (Homoptera: Aphididae), is an important alien aphid pest of cypresses and junipers, and invaded Africa in the late 1980s. The work reported here was carried out as part of a larger programme aimed at the classical biological control of the aphid in Africa. Basic life history attributes including life table statistics of the aphid were quantified in order to facilitate the development of efficient aphid culturing methods and essential baseline information necessary for the culturing of potential parasitoid biological agents prior to selection for introduction to Africa. Developmental rates and fecundity were studied under four constant temperatures (10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C). The effects of several plant nutrients (nitrogen, potassium and phosphorus) supplied at different dose levels on life history attributes of Cinara sp. nov. were also studied. Unlike most other aphids, the apterous morph of Cinara sp. nov. developed through only three instars, and the alate four instars. The aphid is highly aggregative and exploits a wide range of feeding sites from young green branches to woody stems. The developmental period of Cinara sp. nov. ranged from 9.3 days at 25 degrees C to 22.3 days at 10 degrees C and the developmental threshold was 0.61 degrees C. Reproduction was delayed, because of the longer duration of development, and nymph production decreased with decreasing temperature. The intrinsic rate of increase ranged between 0.117 at 25 degrees C and 0.060 at 10 degrees C. Aphid size increased significantly as temperature was lowered. Wing formation was not induced when apterae were reared for up to three generations at each constant temperature but continuous crowding in the supply cultures held at 21 degrees C resulted in a high number of alates being formed. No appreciable effects of the different plant nutrients, supplied either singly or in combination, on the duration of instars or overall survival could be detected.

Comparison of rRNA genotype frequencies of Parmelia sulcata from long established and recolonizing sites following sulphur dioxide amelioration

Abstract: The variable internally transcribed spacer (ITS) regions of the rRNA gene cluster, and the termini of the large and small subunit genes, were amplified from 231 specimens of the lichen-forming fungusParmelia sulcata from the UK and Spain. Amplification products comprised three distinct size groups of 580, 622 and 835 base pairs (bp). Analyses of the collections from England, Wales and central Spain established the 622 bp genotype as the most widespread, and the 835 bp genotype as the next most frequent. The size difference was due to a group I intron at the 3′ end of the small subunit. The relative frequencies of the three genotypes were consistent between long established sites in Spain and the UK. The frequencies of the different size classes were examined in the vegetatively reproducing populations recolonizing following the amelioration of sulphur dioxide air pollution. Populations ofP. sulcata from long established sites where sulphur dioxide levels are known to have risen and then fallen contained two genotypes. Populations from recolonising sites whereP. sulcata had previously been lost consisted of a single genotype (622bp). This technology provides a powerful tool for testing hypotheses relating to the individuality and population structure of lichens, and has implications for lichen conservation.

Differentiation of mitochondrial subgroups in the Verticillium lecanii species complex

Abstract: Presumptive mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs) were obtained from 54 fungal isolates identified as Verticillium lecanii, V. psalliotae or ‘V. lecanii-like’. Analysis of the mtDNA RFLPs showed 20 different patterns, indicating considerable genetic variation within the V. lecanii species complex. There was no direct correlation between host and mtDNA pattern, or between mtDNA patterns and previously described isoenzyme-defined specific groups. Isolates from tropical and subtropical areas showed considerable variation in genotypes, while isolates from temperate regions appeared less variable.

Recovery of fungi after storage for over a quarter of a century

Abstract: This paper discusses the recovery of a sample of strains originally preserved on silica gel over the period 1970–1973 Fifty-three strains were tested of which 18 recovered, demonstrating survival for more than 20 years The recovery of 26 of the strains is directly compared with that of replicates from oil storage and freeze-drying A summary of storage of 421 strains by the silica gel technique is given, reporting survival of 64% for a quarter of a century or more The technique is ideal for preserving sporulating fungi of the Ascomycota and many species of mitotic fungi for laboratories of limited facilities

Presence of a 20 bp insertion/deletion in the ITS1 region of Verticillium lecanii

Abstract: Polymerase chain reaction (PCR) amplification of the complete ribosomal RNA internally transcribed spacer (ITS) region of 36 isolates of Verticillium lecanii and related species gave a single 620 bp product in 31 isolates. Five isolates received as V. lecanii, however, gave a single product of 600 bp. Restriction fragment analysis of the PCR products from all isolates gave consistent patterns for the 31 isolates with a 620 bp product. The five isolates with the 600 bp product showed only minor discrepancies to these, generally related to the size of only one restriction fragment. The total ITS region was sequenced from 10 typical 620 bp isolates and one 600 bp isolate. Sequence variation between the isolates varied from 0 to 14.5%, and the 20 bp size discrepancy was found to relate to an insertion or deletion in the centre of the ITS1 region.

Fungal pathogens of Calotropis procera (rubber bush), with two new records from Brazil.

Abstract: Fungal pathogens associated with the asclepiadaceous weed Calotropis procera (rubber bush) are documented from published, as well as unpublished sources. Two new host-pathogen associations from Brazil; Phaeoramularia calotropidis and Puccinia obliqua, are recorded. The latter species infects the host systemically and induces the formation of conspicuous and damaging witches’ brooms. The rust appears to exert some control of C. procera in the more humid areas of Brazil and the biocontrol potential of this and the other listed pathogens is discussed.

Description of a new species of Orseolia (Diptera: Cecidomyiidae) from Paspalum in West Africa, with notes on its parasitoids, ecology and relevance to natural biological control of the African rice gall midge, O. oryzivora

Abstract: Field sampling of grasses growing in and near rice fields at 12 sites in Nigeria during April/May 1994 recorded the presence of galls on Paspalum scrobiculatumat densities of up to 10.9 galls per m2. These galls were induced by Orseolia bonzii Harris, sp. n., which is described. This species is morphologically close to, but distinct from, the African rice gall midge, Orseolia oryzivora Harris & Gagne, with which it has been confused in earlier studies of that pest species. In host-transfer experiments O. bonzii did not transfer to rice, Oryza sativa. Six hymenopterous parasitoids were reared from galls of O. bonzii and the most abundant of these were Platygaster diplosisae Risbec, Aprostocetus nr. procerae (Risbec) and Neanastatusnr. cinctiventris Girault. Host-transfer experiments with the Platygasterand Aprostocetus species from O. bonzii on Paspalum indicated that the Platygaster may not transfer onto O. oryzivora on rice whereas the Aprostocetus does. The overlap between the parasitoid faunas of the two species of Orseolia is potentially useful as it may be possible to enhance the natural biological control of O. oryzivora by manipulating parasitoid populations on Paspalum.

Molecular differences distinguish clonal lineages within East African populations of Fusarium oxysporum f.sp. cubense

Abstract: Molecular approaches for the assessment of intraspecific diversity within an economically important plant pathogen were compared with traditional physiological methods (vegetative compatibility testing). The vegetative compatibility groups (VCGs) of 14 isolates of Fusarium oxysporum f.sp. cubense (FOC) from Kenya were first assessed using nitrate non-utilizing mutants. Nine of these isolates, from different areas of the country, were compatible with one or more of VCGs 0124, 0125, 0128 and 01220, i.e. they formed a single clonal lineage. Three isolates, all originating from the banana growing district of Kisii, were compatible with the VCG 01212 and formed a second distinct clonal lineage. Mutants could not be recovered from one isolate (62) and two isolates (27 and 30) were not vegetatively compatible with any of the VCG testers and may represent two novel VCGs. Polymerase chain reaction (PCR) fingerprinting, especially when using the M13 derived primer, was found to produce banding patterns that correlated with clonal lineage and also distinguished isolates 27 and 30 when analysed by unweighted pair group method analysis and principle co-ordinate analysis. This approach also distinguished FOC from F. oxysporum IMI350438 isolated from Triticum sp. and from isolates of Colletotrichum gloeosporioides. Total protein profiles were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and although clonal lineages were not separated, isolates 27 and 30 were again distinguishable and FOC produced a different profile to F. oxysporum (IMI 350438) and C. gloeosporioides.

First Report of Colletotrichum gloeosporioides as a Foliar and Die-back Pathogen of Prunus africana in Kenya.

Abstract: During tree disease surveys between February 1996 and March 1998 in highland forests of Kenya, leaves of Prunus africana (Hook f.) Kalkman collected from regeneration wildings in natural forests an...