bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fungitoxic properties of selected South African plant species against plant pathogens of economic importance in agriculture
Authors: PRETORIUS J C , ZIETSMAN P C , EKSTEEN D 
Published: July 2006

SummaryThirty‐nine plant species, representing 20 families from the subclasses Rosidae, Asteridae, Commelinidae and Liliidae, were collected from the Blyde River Canyon Nature Reserve, Mpumalanga, South Africa. Crude extracts were prepared and bioassayed, at equal concentrations, for their antifungal potential by determining the inhibitory effects on the mycelial growth of seven economically important plant pathogenic fungi. Statistically significant differences between plants and plant parts were observed as well as the resistance of different fungi to treatment with different plant extracts. The most significant mycelial growth inhibition was obtained with extracts from two species of the subclass Liliidae, namely Aristea ecklonii and Agapanthus inapertus. The crude extract of A. ecklonii performed best of all extracts as it totally inhibited the mycelial growth of all seven of the plant pathogenic test organisms and outperformed the inhibition by a broad spectrum synthetic fungicide (carbendazim/difenoconazole). Crude extracts of A. inapertus showed complete inhibition of four and strong inhibition of the remaining three plant pathogenic fungi. Although not as efficient as the previous two species, the extract of Anisopappus junodii, from the subclass Asteridae, also showed promising antifungal activity by completely inhibiting mycelial radial growth of two and strongly inhibiting that of the remaining five fungi.
In vivo control of Mycosphaerella pinodes on pea leaves by a crude bulb extract of Eucomis autumnalis
Authors: PRETORIUS J C , CRAVEN P , VAN DER WATT E 
Published: July 2006

SummaryWe previously reported on the in vitro antifungal activity of a crude whole plant extract from Eucomis autumnalis against seven economically important plant pathogenic fungi. A crude extract of the bulb showed similar in vitro mycelial growth inhibition of the same plant pathogenic fungi as well as that of an eighth fungus, Mycosphaerella pinodes, the cause of black spot or Ascochyta blight, in peas. Subsequently, fourth internode leaves were removed from 4 wk old pea plants, placed on moist filter paper in Petri dishes and inoculated with an M. pinodes spore suspension before and after treatment with the extract. The control of Ascochyta blight by different concentrations of the crude E. autumnalis extract was followed in vivo by leaf symptoms over a 6 day period at 20°C in a growth cabinet. The crude extract prevented M. pinodes spore infection of the leaves when the leaves were inoculated with spores both before or after treatment with the extract, confirming complete inhibition of spore germination. The crude E. autumnalis extract showed no phytotoxic reaction on the leaves even at the highest concentration applied.
Variability in the developmental stage of apricot ovules at anthesis and its relationship with fruit set
Authors: ALBURQUERQUE N , BURGOS L , EGEA J 
Published: July 2006

SummaryThe stage of ovule development at anthesis and its relationship with fruit set was studied in several apricot cultivars growing in Mediterranean climatic conditions. Although generally the ovule was immature at anthesis, a great variability was found in the stage of development of the ovules from different cultivars. Considering functional ovules to be those with an embryo sac with at least four nuclei at anthesis, the earliest flowering varieties frequently showed more than 50% of functional ovules. Though these results could suggest that there is an influence of the chilling requirement on the percentage of functional ovules at anthesis, data recorded from two cultivars, ‘Goldrich’ and ‘Colorao’, with high chilling requirements, contrast with this suggestion. These results indicate that in apricot flowers the development of the embryo sac at anthesis is genotype dependent. The fact that a high frequency of functional ovules at anthesis was found, in cultivars with more than 50% of fruit set, suggests that, to be fertilised, a certain level of development of the apricot ovules at this time is necessary.
Ascocarp formation and survival and primary inoculum production in Erysiphe (sect. Microsphaera) pulchra in dogwood powdery mildew
Authors: MMBAGA M T 
Published: July 2006

SummaryDevelopment of powdery mildew Erysiphe (sect. Microsphaera) pulchra in dogwood (Cornus florida) was assessed over a 5‐year period (1996–2000). Variations in the timing of initial infection, disease severity, ascocarp formation, and primary inoculum density were evaluated. Ascocarps formed late in the growing season (September‐November) when relatively low temperatures (< 27°C) persisted for at least 2 weeks, but ascocarp abundance was not influenced by disease severity. Studies conducted in a controlled environment showed that low temperatures triggered ascocarp formation and neither day length nor host plant age affected ascocarp formation. Ascocarps formed within 12–14 days at 18°C/ 10°C (day/night) and 23°C/15°C, but required 25 days at 26°C/18°C; no ascocarps formed at 28°C/ 20°C. Because ascocarps are an important source of primary inoculum for dogwood powdery mildew, ascocarp survival was evaluated in a 2‐year study (1998–2000). 60–80% of mature, dark‐coloured ascocarps survived at ‐10°C and ‐20°C and maintained viable spores for 4 months, but only 4–12% of partially developed, light brown ascocarps survived at ‐10°C and ‐20°C in the first experiment and only 30–40% survived in the second experiment. Immature ascocarp initials (cream‐yellow in colour) withered and disintegrated at all temperatures (24°C/20°C, 4°C, ‐10°C, and ‐20°C). Because ascocarps need time to mature, the timing of ascocarp initiation affects ascocarp maturity and thus winter survival and primary inoculum density. The evaluation of spring inoculum dispersal to spore traps and trap plants in 1999 and 2000 showed that rainfall patterns in early spring influenced primary inoculum and thus the timing of initial infection.
Transmission features of Mai de Río Cuarto virus in wheat by its planthopper vector Delphacodes kuscheli
Authors: ARNEODO J D , GUZMAN F A , CONCI L R , LAGUNA I G , TRUOL G A 
Published: July 2006

Summary Mal de Rio Cuarto virus (MRCV, Fijivirus) infects maize (Zea mays) and other gramineae, producing significant losses in Argentina. Although MRCV mainly affects maize, other cereals, such as wheat, serve as potential virus reservoirs and hosts for the planthopper vector Delphacodes kuscheli. Aspects of the virus‐vector relationships were elucidated by studying the minimum periods of acquisition access (AAPmin), latency (LPmin) and inoculation access (IAPmin) in wheat (Triticum aestivum L.). Trials were conducted under controlled conditions of temperature (24 ± 1°C), photoperiod (12 h light) and humidity (50 ± 5%). The results show that the AAPmin was 5 h, LPmin was 10 days (even though, the median latent period was between 16 and 17 days) and IAPmin was 30 min. Our experiments have demonstrated, for the first time, a persistent manner of virus transmission. No differences were detected in transmission ability between males and females. The implication of these results on virus taxonomy and epidemiology are discussed.
Cavity spot of carrot (Daucus carota)
Authors: HILTUNEN L H , WHITE J G 
Published: July 2006

SummaryCavity spot disease of carrot (Daucus carota) has been one of the intractable problems for both growers and scientists. Carrots are rejected at grading with one or two visible lesions, and when disease incidence passes a relatively low threshold it becomes uneconomic to harvest crops. For the scientist, there has been considerable pressure to produce both information on the cause of the disease and a cure. Many putative causes have been advanced over the years, but these were almost always contradicted by subsequent work. The first solid indication of involvement of a pathogen was when three different fungicides with activity against Oomycete fungi all reduced disease. Very quickly the causal agents Pythium violae and Pythium sulcatum were isolated from cavity spot lesions and Koch's postulates satisfied. The species are not typical of the more common pythia, having slow growth at normal temperatures, which means that in the context of isolation work, plates may be overgrown by other species before they are seen. Metalaxyl fungicide was identified as the most effective in controlling cavity spot caused by P. violae, but P. sulcatum is naturally tolerant of the fungicide. Recently, metalaxyl has been shown to be subject to enhanced microbial degradation. This phenomenon has been associated with failure to control cavity spot. No other fungicide has been shown to be consistently effective in the field, and none has been registered for disease control. For the future, this means that control of cavity spot can not be based solely on fungicidal control. Other, complementary strategies are necessary for reducing disease. Calcium carbonate is known to have significant effects on cavity spot, probably by inducing a soil microflora inhibitory to filamentous fungi. Management of agronomic aspects such as irrigation, soil cultivation and the length of time for which crops are grown may all be used, while carrot cultivars with some field resistance may be beneficial. However, one of the most significant factors is disease avoidance by not selecting fields with high inoculum levels. One serology‐based risk assessment test has been produced and commercialised, and molecular probes which could be the basis of more sensitive tests are available for both pathogens. The potential for disease reduction via a management strategy combining several key components is discussed.
Integrating cultural control methods for tomato late blight (Phytophthora infestans) in Uganda
Authors: TUMWINE J , FRINKING H D , JEGER M J 
Published: July 2006

SummaryCultural control measures against tomato late blight (Phytophthora infestans) were evaluated in six field experiments over 3 years in Uganda. Each experiment included sanitation (removal of diseased plant tissues), fungicide (mancozeb) application, and an untreated control, as standard treatments. Late blight incidence and severity were greatly reduced by sanitation, without reducing the number of healthy leaves; however, tomato growth and production were adversely affected. Fungicide treated plants retained the highest numbers of flowers and attached fruits and gave the highest yields. Three cultural practices were evaluated in repeated experiments for their effectiveness in alleviating the adverse effects of sanitation. Tomatoes grown within plastic shelters early in the production cycle were taller, and had more healthy leaves than those grown late. The numbers of diseased leaves and disease severity were equally low in sanitation alone and plastic shelter/with sanitation treatments. Flower and fruit production were significantly higher when tomatoes were grown under early shelters with sanitation than with sanitation alone. Planting density was increased without significant effects on late blight and tomato growth and production. Intercropping tomato with soybean (Glycine max) or sesame (Sesamum indicum), with sanitation, limited late blight development, but taller intercrops suppressed tomato growth and production. Integrated treatments (combining plastic shelters, a sesame intercrop and high tomato planting density) were evaluated, with and without sanitation, against the fungicide mancozeb. The mean numbers of healthy leaves in the integrated treatments were not significantly less than with fungicide treatment. Late blight incidence and severity were higher in the integrated plots without than with sanitation. The numbers of flowers and attached fruits were not significantly less in integrated treatments than in fungicide treated plots, but tomato yield was highest with fungicide treatment.
Leaf photosynthetic parameters of two maize (Zea mays) cultivars in response to various patterns of chilling temperatures and photon flux densities
Authors: SAROPULOS A S , DRENNAN D S H 
Published: July 2006

SummaryChilling‐induced photosynthetic impairment was examined in leaves of maize (Zea mays L.) seedlings of two cultivars, one adapted to western Europe and one adapted to Mexican highlands.Three experiments were performed in a controlled environment. The effects of chilling night temperatures, of chilling at high light intensity and of variable chilling day temperatures on photosynthetic parameters, were evaluated.Chilling in the dark period resulted in stomatal limitation of net photosynthesis. Chilling at moderate to high light intensities caused chilling‐dependent photoinhibition of CO2 uptake. Photobleached maize leaves did not resume normal photosynthetic function.Maize cv. Batan 8686 from the highlands of Mexico was less susceptible to photosynthetic damage than maize cv. Bastion adapted for cultivation in W. Europe, when exposed to chilling night temperatures, or to mild chilling photoinhibitory conditions.
Rapid vascular movement of tobraviruses does not require coat protein: evidence from mutated and wild‐type viruses
Authors: SWANSON M , BARKER H , MACFARLANE S A 
Published: July 2006

SummaryEarly studies of the tobravirus Tobacco rattle virus (TRV) described two types of virus isolate with apparently different disease characteristics. M‐type isolates, which contain both viral genomic RNAs and form virus particles, could be passaged by mechanical inoculation and produced rapid but shortlived systemic symptoms. In contrast, NM‐type isolates, which contain only RNA1 and do not form virus particles, were difficult to passage by mechanical inoculation and were very slow to produce systemic symptoms. From the early observations on such isolates made in the 1960s, it has become accepted that M isolates with encapsidated TRV particles move rapidly through the vascular system whereas NM isolates containing only unencapsidated TRV RNA1 move only slowly via plasmodesmata from cell to cell and take many weeks to reach the upper parts of plants. However, we show that NM isolates of TRV and another tobravirus Pea early‐browning virus (PEBV) move into systemic tissue of TV. benthamiana and N. clevelandii by 6 days post inoculation, suggesting that this rapid movement occurs via the vasculature. The systemic movement of TRV and PEBV mutants lacking functional coat protein that have been modified to express the green fluorescent protein were examined by confocal microscopy. This confirmed that the tobraviruses do not require the CP for long distance movement via the phloem, a property that is shared with only a small group of plant viruses.
15N stable isotope labelling of slugs (Gastropoda: Pulmonata)
Authors: HAKVOORT S G H , SCHMIDT O 
Published: July 2006

SummaryStable isotope tracers are a promising tool for investigating the ecology of terrestrial slugs, including predator‐prey relationships, migration behaviour, nutrient turnover and dietary routing. The objective of the present feasibility study was to label two economically important slug groups, Deroceras reticulatum and keeled slugs (families Limacidae and Milacidae, respectively), with the stable isotope 15N under controlled laboratory conditions. Significant isotopic enrichment in slug tissue was detected after 4 days and persisted for at least 10 days after slugs had been fed on 15N enriched food for a period of 15 days. The time course of 15N uptake into slug tissues and its relation to food consumption were well described mathematically. Estimated mean 15N assimilation efficiencies from labelled maize mixed with unlabelled wheat bran were 30% and 38%, respectively, for the species groups studied. These findings suggest that slugs can be readily and efficiently labelled and that it is feasible to devise protocols for producing large numbers of isotopically labelled slugs for use in ecological studies. A simple method is described for the collection and analysis of cutaneous mucus from individual slugs which can be used to test uniformity of isotopic labelling.
Prospects for molecular breeding of barley
Authors: THOMAS W T B 
Published: July 2006

SummaryData from UK Recommended List Trials showed that the introduction of new cultivars of spring and winter barley has maintained a significant increase in yield over time, whereas there has been no significant improvement in hot water extract, the major determinant of good malting quality, in either crop. Commercial barley breeding is based upon phenotypic selection, and the introduction of molecular breeding methods must either increase the rate of advance, or offer an improvement in the cost‐effectiveness of breeding programmes. Molecular breeding can be applied to either single gene or polygenic characters but is not widely used in commercial barley breeding, other than as a marker for resistance to the Barley Yellow Mosaic Virus complex. There are many reports of potential targets for use in molecular breeding but the few validation studies that have been carried out to date are disappointing. Results from genomics studies are likely to lead to the identification of key candidate genes, which can be associated with economically important characters through co‐location on certain chromosomal regions. Associations between candidate gene sequence haplotypes and phenotypic characteristics is expected to identify allelic combinations, which are most frequently observed in successful cultivars, that can be used in molecular breeding of barley on a commercial scale.
Strategies of plant breeding for improved rumen function
Authors: KINGSTON‐SMITH A H , THOMAS H M 
Published: July 2006

SummaryIn general, breeding programmes directed at the improvement of forage have concentrated on easily measurable phenotypes such as yield, digestibility, resistance to lodging, etc. Selection programmes have improved forage production but historically have addressed relatively few quality considerations. In addition, selection for quality has been limited by availability of suitable analytical techniques. With the current emphasis on quality rather than quantity and the desire by the public for greater understanding about where their food comes from, quality considerations should be a greater target in future breeding programmes. This review briefly covers previous improvements in quality of grazed and silage forages and considers how new technologies might be employed to realise targets for future improvements. In particular we address the concept that interactions between rumen micro‐organisms and ingested plant material in the rumen are not static but are in fact dynamic. This has implications for post‐ingestion biology and feed utilisation.
Differentiation of velogenic, mesogenic and lentogenic strains of Newcastle disease virus by multiplex RT‐PCR
Authors: SONGHUA SHAN , CHAOGANG SHAO , CAOZHE XU , JIAN ZOU , YONGQIANG HU , JIANHUA WU , ZUXUN GONG 
Published: July 2006

SummaryA multiplex RT‐PCR technique has been developed for differentiation of velogenic, mesogenic and lentogenic pathotypes of Newcastle disease virus (NDV), using a set of three oligonucleotide primers designed from NDV genomic RNA (P1, P2 and P3). The primer pair P1 and P2 generated a RT‐PCR product of 204 bp, only with RNA from velogenic and mesogenic strains, whereas the P1 and P3 generated a 364 bp product only with RNA from mesogenic and lentogenic strains. Thirty four NDV strains, including some reference strains (known pathotypes), NDV field isolates and NDV vaccine strains, as well as other avian virus strains, were tested with multiplex RT‐PCR. All reference strains tested were differentiated in agreement with their intracerebral pathogenicity index (ICPI) values or with the pathotypes known in previous reports. The nucleotide sequence analysis of RT‐PCR products for four NDV strains was fully in agreement with the RT‐PCR characterisations of these strains. The RT‐PCR results of other avian RNA viruses further confirmed the reliability and specificity of this technique. However, the RT‐PCR failed to detect some other avian NDV, which may not originate from chicken. This multiplex RT‐PCR technique is simple and easy to perform. It could be applied not only to determine the origin of NDV, but also may be used diagnostically in molecular epidemiological analysis of ND and for prediction of pathotypes of NDV isolates.
Effects of three modern insecticides, pyriproxyfen, spinosad and tebufenozide, on survival and reproduction of Chrysoperla carnea adults
Authors: MEDINA PILAR , BUDIA FLOR , DEL ESTAL PEDRO , VIÑUELA ELISA 
Published: July 2006

SummaryThree novel insecticides, pyriproxyfen, spinosad and tebufenozide, were evaluated for their effect on survival and reproduction of Chrysoperla carnea adults using two methods of exposure: direct contact and ingestion. Pyriproxyfen and tebufenozide proved to be harmless to adult survival, whereas spinosad 72 h after treatment reduced the number of adults by 39.8% and 87.2% in topical and ingestion treatment at the maximum concentration recommended (800 mg a.i. litre−1). Fecundity was not affected irrespective of the insecticide or time of application (before or after the onset of oviposition). Concerning fertility, only pyriproxyfen exerted a negative effect on hatching when the eggs were deposited by females treated by ingestion in the post‐oviposition period at the highest concentration tested (150 mg a.i. litre−1).
Isolation of anti‐fungal phenolic compounds from petioles of two Hevea brasiliensis (rubber) genotypes and their effect on Phytophthora meadii
Authors: JAYASURIYA K E , WIJESUNDERA R L C , DERANIYAGALA S A 
Published: July 2006

SummaryPhenolic compounds were present in greater amounts in non‐infected petioles of genotypes of Hevea brasiliensis that are resistant to Phytophthora leaf disease than in genotypes that are susceptible. Phenolic compounds extracted from petioles of either susceptible (PB86) or resistant (RRIC100) genotypes, before or after infection with Phytophthora meadii, had anti‐fungal properties. Artificially infected petioles of PB86 had phenolic acids, triterpenoids or flavonoids, whereas healthy petioles contained only triterpenoids or flavonoids. However, healthy or infected petioles of RRIC100 contained only trace amounts of the above compounds and of vanillin (3‐methoxy‐4‐hydroxybenzaldehyde). Vanillin and umbelliferone (7‐hydroxycoumarin) were shown to suppress zoospore germination of P. meadii on glass slides and to inhibit its growth in pea broth and V‐8 juice agar. Vanillin was slightly more active than umbelliferone. Resistance of RRIC100 to Phytophthora was suspected as being related to the polymerisation of phenolic compounds to form lignin, which may suppress further spread of the pathogen's mycelium into healthy tissues. Formation of lignin from phenolic aldehydes as a barrier to disease spread may be a critical factor in resistance.
Localisation and movement of Plum pox virus in apricot stem tissues
Authors: DICENTA F , MARTÍNEZ‐GÓMEZ P , RUBIO M , AUDERGON J M 
Published: July 2006

SummaryLocalisation and movement of Plum pox virus (PPV), sharka disease, in stem tissues of susceptible and resistant apricot (Prunus armeniaca L.) cultivars was studied. Two different assays were performed. In the first assay, apricot cultivars were grafted on to a non‐inoculated GF305 peach rootstock and, after two months, the sprouted apricot was inoculated by chip‐grafting. In the second assay, apricot cultivars were grafted on to a previously chip‐inoculated GF305 showing strong PPV symptoms. Localisation of virus was studied in apricot stem by immuno‐tissue printing and sharka symptoms in GF305 and apricot leaves were also observed. Virus was mainly localised in the xylem, and sometimes in the cortex and pith. Results revealed that, while all the cultivars allowed limited virus movement from the inoculation point, only the susceptible cultivars (Screara, Bebeco and Colomer) allowed long distance movement and even showed symptoms in leaves.