Sex-based variation in insecticide susceptibility and tolerance related biochemical parameters in tea mosquito bug <Emphasis Type="Italic">Helopeltis theivora</Emphasis>

Helopeltis theivora, one of the major pests of tea from North east India, reported to acquire tolerance against commonly used synthetic pesticides. Study on relative toxicity of both sexes of H. theivora along with their detoxifying enzyme levels were carried out to assess developemnt of sex-based tolerance of pest against the pesticides. The present study showed that female develop more tolerance among H. theivora population than male. Relative toxicity tests showed that LC₅₀ was higher in female than male H. theivora. This result reflects in general, sex level difference in tolerance status of the pest along with corresponding changes in the quantities of detoxifying enzymes. Female of H. theivora showed significantly higher general estearse and glutathione-S-transferase activities than that of male; however there was no significant difference in cytochrome P450 activity. The total body lipid content was also found to be higher in female than male, which indicated female attribute to be more tolerant than male. Body weight of female was significantly higher than that of male, which showed positive correlation with general esterase and glutathione-S-transferase. Hence, on application of recommended dose of pesticide, chance of survivability of female is better in field, leading to addition of more tolerant forms.     

Change in activity of detoxifying enzymes in directionally selected population of tea mosquito bug (<Emphasis Type="Italic">Helopeltis theivora</Emphasis>) (Heteroptera: Miridae) by an organophosphate insecticide

The heteropteran bug, Helopeltis theivora is a polyphagous pest attacking the foliage crop tea and several other crops grown in the old world tropics. Application of synthetic insecticides, especially organophosphate was so far an effective and economic means of conventional management of the pest. Severe selection (bottlenecking) of H. theivora population by exposure to LC₈₀ dose of an organophosphate insecticide, monocrotophos resulted in 105 fold increase in tolerance level in the third generation. The total activity of general esterases (GE) and cytochrome P450 mono-oxygenases (CYP450) analogously increased in insecticide-selected F2 generation by 16.4 and 9.5 fold, respectively. Such enhanced enzyme activity could be related to the higher tolerance levels of the selected bug. Electropherogram of GE and CYP450 of the insecticide-selected generations indicated a change in isozyme profile with their elevated expressions. Induced isozymes in insecticide selected generations were only partially inhibited, when blocked by the insecticide. These findings imply that different groups (zones) of isozymes of the detoxifying enzymes are involved in imparting higher tolerance in insecticide-selected generations. Isozyme profiles of defence enzymes can be used as indices for identifying tolerance level in the field population of H. theivora, enabling tea planters to carry out rapid monitoring of the tolerance status of the pest populations, thereby providing a ready clue to choose an effective insecticide for pest management.     

Impact of environmental factors on infestation of tea leaves byHelopeltis theivora, and associated changes in flavonoid flavor components and enzyme activities

Attack of tea plant (Camellia sinensis (L.) O. Kuntze) leaves by the tea mosquito bugHelopeltis theivora (Hemiptera: Miridae) was positively correlated to temperature and rainfall, and partially to humidity, as determined in 12 varieties during the period 2000–2002. The insect attack was severe during the months of May–September, which had high temperature and rainfall, and led to severe loss of biomass due to curling and drying up of the leaves. The biochemical response of these 12 varieties of tea to attack by the insect was determined with special reference to oxidative enzymes and flavonoid flavor components. Insect attack led to an increase in the activities of the oxidative enzymes peroxidase, ascorbate peroxidase and polyphenol oxidase. Activities of phenyl alanine ammonia lyase generally decreased as a result of insect attack, which was significant in the United Planters Association of South India (UPASI) varieties. A significant decrease in polyphenols was also obtained in UPASI varieties. HPLC analysis of catechins revealed a decrease in some of the catechins in the infected leaves. Analysis of theaflavins from infusion of healthy andHelopeltis-infested tea leaves revealed no changes. http://www.phytoparasitica.org posting Dec. 19, 2004.     

Bestaat er een verband tusschen het voorkomen van black heart en het optreden van virusziekten bij den aardappel?

Summary Biourge andSokal have claimed: firstly: Black heart is not caused by lack of oxygen, followed by suffocation of central part of the tuber, but it results from attack byBacillus mesentericus vulgatus;Flugge) andBacillus mesentericus ruber (Globig); Secondly: Tubers suffering from black heart develop plants suffering from the diseases, which have been ascribed to viruses. Therefore it is not necessary to suppose the existance of viruses. This type of disease is caused by the bacilli mentioned. Sanitation of the plants can be performed by keeping the tubers during 48 hours at 42 centigrades. The tubers withstanding this heating without turning black develop virus-free plants. The present author however has, in controlling experimentally the work of the writers mentioned above, not been able to detect any relation between the occurrence of black heart in the tubers and of viroses in the sprouts. Sensibility for black heart proved to be more dependent on the climate and the soil, than on hereditary characters of the potato variety. Between the melanine-value (as aimed byHaehn) and the intensity of black heart, thus far no correlation has been found by the present author.     

Schurft op Pyrancantha

Summary Spilocaea pyracanthae (Otth) v. Arx comb. nov. (Syn.:Fusicladium pyracanthae (Otth) Viennot-Bourg.), the scab fungus ofPyracantha coccinea, overwinters in its conidial stage on the living leaves and on twigs. No perithecial stage could be found the last three years on overwintered fallen leaves.     

A virus of celery related toCucumis virus 1st. Chr. Noordam

Conclusion There is a difference between the reactions ofApium graveolens to the typicaltomato aspermy virus on the one hand, and to the virus isolated by the writer from celery, and identified afterNoordam andRoland asCucumis virus 1st. Chr. Noordam, on the other hand.If it is assumed that the difference is not caused by the varieties of celery used, this suggests thattomato aspermy virus andCucumis virus 1st. Chr. are not quite identical.Samenvatting Op selderij werd een virus gevonden dat dezelfde symptomen op toetsplanten, en dezelfde serologische reactie geeft alsCucumis virus 1st. Chr. Noordam. Tot nu toe kon het tomato aspermy virus niet op selderij worden overgebracht. Als dit verschil niet veroorzaakt wordt door de gebruikte selderijvariëteiten, dan kan geconcludeerd worden, dat de twee virussen niet precies dezelfde zijn.Sustained by the Institute for Scientifical Research in Agriculture and Industry (IRSIA).     

Influence of altitude on adult emergence and dynamics ofKaltenbachiola strobi (Winnertz) (Diptera: Cecidomyiidae) populations and its parasites in the Tatra National Park, Poland

A field study onKaltenbachiola strobi (Winnertz) (Diptera: Cecidomyiidae), was carried out between 1987 and 1993 in the highest mountain range in the Western Carpathians located within the Tatra National Park, in southern Poland. Rearing and analysis of 5 780 cones ofPicea abies (L.)Karst., collected from trees growing at different altitudes, yielded 30,478 individuals ofKaltenbachiola strobi, which infested 89.10% of the cones. In case of 29.81% of cones there were more than 20 larvae ofK. strobi per cone. It was shown thatK. strobi in the Tatra Mts. is more abundant in spruce stands of the upper mountain forest zone. Significant connections between the time of cone infestation byK. strobi and its parasitoids and characteristic phenophases in spruce foliage and cone development, and also the development of selected vegetation of the forest floor at different heights above sea level were determined. It was shown that the population dynamics ofK. strobi had tendency to alternate the increase and decrease in numbers every two years. It was also discovered that every two years spruce cones were inhabited by the population ofK. strobi with increased percentage of individuals having prolonged diapause. In total, the parasitoids reduced the population ofK. strobi by about 16–22.63%. Parasitism ofK. strobi in the lower mountain forest zone was higher than in the upper zone.Triplatygaster contorticornis Ratz. (Hymenoptera: Platygasteridae),Torymus azureus Boheman (Hymenoptera: Torymidae) andTetrastichus strobilanae Ratz. (Hymenoptera: Eulophidae) were most effiecient in reduction of the population ofK. strobi, and in the lower mountain forest zoneT. azureus was the dominant parasitoid species, while in the upper zoneT. contorticornis andT. strobilanae. It was shown that a considerable part of the populations ofT. azureus, T. contorticornis andT. strobilanae have their diapause prolonged and highly synchronized with the diapause of their host.     

“Zwartbenigheid” bij tulp en iris,veroorzaakt doorSclerotium wakkerii nov. spec.

Samenvatting Aansluitend op een vorige publikatie over de z.g. zwartbenigheid bij tulpen (Boerema, 1960) zijn in dit artikel nadere gegevens medegedeeld over deze ziekte en de veroorzakende schimmel. Een 23-tal bloembolgewassen zijn door uitplanting op zwaar besmette grond getoetst op hun gevoeligheid voor deze ziekte. Daarbij kon het typische ziektebeeld van de zwartbenigheid alleen worden verkregen bij tulpen en bolirissen. De uit de praktijk afkomstige stelling dat ook krokussen voor deze ziekte gevoelig zijn (Silver & Slootweg, 1959), kon niet worden bewezen.De kenmerkende eigenschappen van de sclerotiën vormende schimmel die deze zwartbenigheid veroorzaakt, zijn uitvoerig besproken. Daar de schimmel onbekend blijkt te zijn, is deze beschreven als een nieuwe soort:Sclerotium wakkerii. Deze schimmel is nauw verwant aanSclerotium denigrans Pape, die een zwarte verkleuring vanConvallaria-kiemen veroorzaakt (Pape, 1943).Summary After reference to an earlier paper on black leg of tulips (Boerema, 1960) the present paper gives further data on the disease and the causal fungus. Besides affecting tulips, the disease is also found in the field on bulbous irises. The disease symptoms are shown in figs. 1, 2, 3 and 4.The susceptibility to black leg of 23 bulb species was tested in heavily contaminated soil. In agreement with experience in practice, only tulips and irises developed the typical black leg symptoms. In other bulb species a black discoloration of the dead membraneous bulb or tuber tunic was sometimes found, but no disease symptoms appeared above ground. This applied also to crocus, for which susceptibility to black leg in the field has been claimed (Silver & Slootweg, 1959).The black leg-fungus is easily isolated on cherry agar at 20 °C (fig. 5a), after treating the attacked tissue with a detergent and rinsing with tap water. Growth of the fungus was studied on malt agar, as this medium favours good and rapid growth. The relation between the growth rate on malt agar in the dark and temperature is shown in fig. 6. In the early stage a white flat mycelium is formed; later this turns brownish-black, secreting a typical dark pigment in the medium (fig. 7a and 7b). The hyphae (fig. 5d) vary in width from 1.8 to 7.5 , the walls being rather thick, 0.4 to 0.8 . The hyphae are often anastomosed and branched. After 2 or 3 weeks in culture the fungus develops brownish-black round or flattened irregular sclerotia 2–5 mm in diameter and 0.5–1.5 mm thick, consisting of a compact mass of hyaline hyphae surrounded by thick-walled dark coloured cells (fig. 5a and 5c). When the fungus is grown at low temperatures sclerotia sometimes develop in the aerial mycelium. These are always somewhat spherical and at first white in colour (fig. 5b). In an old culture of the fungus grown on malt agar microconidia formed in phialides were found in 1960 (Boerema, 1960). This has not been observed again, however, so possibly a contamination was concerned.The black leg fungus differs from all other known sclerotia producing fungi.¹ It is therefore described as a new species,viz. Sclerotium wakkerii Boerema & Posthumus nov. spec. We take pleasure in naming this species after Dr.J. H. Wakker (1859–1927), originator of scientific work on bulb diseases. Living cultures of the fungus have been placed at the disposal of the Centraalbureau voor Schimmelcultures at Baarn (type culture) and at the Commonwealth Mycological Institute at Kew. Dried plate cultures were sent to the Commonwealth Mycological Institute at Kew and the Rijksherbarium at Leyden. Sclerotium wakkerii closely resemblesSclerotium denigrans Pape, the cause of a black discoloration of the shoots of lily of the valley (Pape, 1943). However, the sclerotia ofSclerotium denigrans are considerably smaller than those ofSclerotium wakkerii.     

De invloed van enige virussen op de concentraties van organische zuren in een aantal planten

Samenvatting In dit onderzoek werden de concentraties van organische zuren in gezonde en in even oude, met virus geïnfecteerde planten vergeleken. Deze proefplanten warenPhysalis floridana, Nicotiana tabacum var. White Burley enLycopersicum esculentum var. Ailsa Gray. Partijen van 40 of 60 planten werden mechanisch geïnoculeerd, respectievelijk met X-virus, Y-virus, tabaksmozaïekvirus en een virus, dat rozetziektesymptomen op de kers veroorzaakt. Bovendien werd bladrolvirus, overgebracht doorMyzus persicae, bijPhysalis en tomaat in het onderzoek betrokken.Zowel op de dag van de inoculatie als 7, 14 en 21 dagen later werden 20 gezonde planten en 20 exemplaren van elke genoemde partij geoogst. Elk monster werd met water geëxtraheerd. Na zuivering van het extract door een sterke kationwisselaar Imac C 12 en concentratie in vacuo werden de organische zuren met behulp van silicagelzuilen en mengsels van chloroform en n-butanol als solvents kwantitatief bepaald. Twee dimensionale papierchromatografie maakte verificatie van de identificatie van de in de extracten voorkomende zuren mogelijk.Behoudens een enkele uitzondering werd in het algemeen gevonden, dat de zieke planten hogere zuurgehalten bezitten dan de gezonde. Het wordt waarschijnlijk geacht, dat door de virusinfectie het evenwicht tussen de fotosynthese, de ademhaling en de eiwitsynthese zodanig verschuift, dat het gehalte van de organische zuren, speciaal dat van appel- en citroenzuur, verhoogd wordt.Summary A number of publications, concerning special aspects of the relationship between virus synthesis and the metabolism of organic acids, showed a reciprocal influence. However a more general investigation into the influence of the virus infection on the changes in organic acids seemed necessary.In the present paper the concentrations of organic acids in healthy plants and in those of the same age, infected with virus, are compared. For this purpose plants ofPhysalis floridana, Nicotiana tabacum var. White Burley andLycopersicum esculentum var. Ailsa Gray were used. Groups of 40 or 60 plants were inoculated with potato virus X, potato virus Y, tobacco mosaic virus and a virus, causing symptoms of rozet ziekte in cherry respectively. The potato leaf roll virus, transmitted byMyzus persicae, was used withPhysalis and tomato.On the day of inoculation as well as 7, 14 and 21 days later 20 healthy plants and 20 specimen of each group, above mentioned, were harvested. These samples were boiled for five minutes in an amount of water of twice the fresh weight. After mixing, each suspension obtained was subjected to 10,000 atm. in a hydraulic press, the sap then centrifuged (8000 r.p.m. during 10 min.) and the residue washed once. The combined supernatants were percolated through a strong cation-exchanger Imac C 12 (columns of 30×1.2 cm). The effluent contained the organic acids and the carbohydrates. Further purification appeared not to be necessary. The solution was concentrated in vacuo at 40–50°C and dried in a warm stream of air.The organic acids in the dried preparations were analyzed according to the method ofBulen, Varner & Burrell (1952) on silicagel columns of 4 grams, the preparation of which is described byNijkamp (1954). AsBulen et al. worked with columns of 8 grams, we used proportional amounts of solvent mixtures of chloroform and n-butanol, recommended in their publications. After placing the column on a fraction collector, the fractions were titrated against 0.01 n NaOH, using bromothymolblue as an indicator.Although each organic acid leaves the column at a definite fraction-number we verified the identifications of the acids by means of paper chromatography (Wolfgang, 1957) on Ederol-202 filter paper. A mixture of 80 volumes of 96% ethanol, 4 vol. of ammonia and 16 vol. of water as the first solvent and a mixture of 77 vol. of n-butanol, 12 vol. of formic acid and 11 vol. of water as the second solvent were used. After dipping the paper in a mixture of 16 ml aniline, 5 g glucose, 30 ml 96% ethanol and 470 ml light petroleum (b.p. 40–60°C) and heating for 15 min. at 120°C the acids became visible as brown spots on a white background. Especially oxalic, malic and citric acids were demonstrated on the papers.In general the tables show that during the development of the plants the content of organic acids, particularly of the oxalic, malic and citric acids, is lower in normal plants than in diseased ones. ThePhysalis plants, infected with the viruses X and Y and the tomatoes, inoculated with leaf roll virus and virus X are an exception to this. Their contents of organic acids being the same during the first week after the virus-inoculation as those of normal plants. The higher concentrations of the acids in tobacco could be shown very clearly already one week after the infection, whereas the symptoms were not yet visible. The same occurs in the case of tomatoes infected with virus Y, tobacco mosaic virus and the cherry virus.Investigations by several authors have shown an increased respiration activity and a decrease in photosynthesis. It is assumed that the substrate for the synthesis of organic acids will be present at a lower rate. As the synthesis of proteins would be decreased, a higher content of organic acids would result.     

Over de cicadellidenfauna van de kers

Summary In connection with the investigation of a possible vector of the Eckelrader virus disease of sweet cherry in the Netherlands, an examination was made of the leaf hopper fauna of cherry. Five species were found breeding regularly on this hostplant viz.Typhlocyba quercus (F.),Erythroneura alneti (Dhlb.),Erythroneura flammigera (Geoffr.),Empoasca flavescens (F.), andEupteroidea stellulata (Burm.). Some details about their biology are given. Other leafhopper species found on cherry, but which are probably only there by accident, are mentioned.      

Comments on the method to test side effects of pesticides on the predatory mitePhytoseiulus persimilis Ath.-Hen

A paper published byKniehase & Zoebelein (1990) describes a new laboratory method to test the side effects of pesticides on the predatory mitePhytoseiulus persimilis and criticizes the laboratory test developed by the International Working Group pesticides and beneficial organisms of the International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS). The present publication discusses the advantages and disadvantages of both methods, responds to the criticism and mention the overall concept of the IOBC/WPRS Working Group including semifield and field test methods.In einer Arbeit vonKniehase undZoebelein (1990) wird ein neues Laborverfahren zur Prüfung der Nebenwirkung von Pflanzenschutzmitteln auf die RaubmilbePhytoseiulus persimilis beschrieben. Die genannten Autoren äußern sich kritisch über das seither von der Arbeitsgruppe Pflanzenschutzmittel und Nutzorganismen der International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS) praktizierte Verfahren. In der vorliegenden Arbeit werden die Vor- und Nachteile der beiden Prüfmethoden diskutiert. Einer Reaktion auf die Kritik folgt eine kurze Beschreibung der gesamten Konzeption der genannten Arbeitsgruppe, die auf einer Kombination aus Labor-, Halbfreiland- und Feldprüfverfahren beruht.     

Electron microscopical investigations of mosaic diseased wheat plants found in Italy

Summary For some years past at several places in the province of Brescia a mosaic disease of wheat has been detected which probably must be attributede to a virus (Grancini, 1959). Presumably the same disease has recently been constatated in other provinces of North Italy.Electron microscopical study of diseased wheat leaves showed that the preparations which were obtained with the dipping method ofBrandes (1957) all contained rod-shaped virus particles with a length of 300 m. These particles were absent from healthy plants. Whether or not this virus is directly responsible for the mosaic disease could not be established, since we did not succeed in transmitting the virus artificially.Samenvatting Sedert einige jaren wordt op verschillende plaatsen in de provincie Brescia een mozaïekziekte bij de tarwe gevonden, waarvna de oorzaak waarschijnlijk aan een virus moet worden toegeschreven (Grancini, 1959).Bij elektronemicroscopisch onderzoek van zieke bladeren is gevonden, dat de preparaten, welke met de doop-methode vanBrandes (1957) verkregen waren, alle staafvormige virusdeeltjes ter lengte van 300 m bevatten (fig. 1). In preparaten van gezond bladmateriaal kwamen deze deeltjes niet voor. Of dit virus direct aansprakelijk is voor de mozaïekziekte kon nog niet aangetoond worden, aangezien het tot nu toe niet gelukt is het virus langs kunstmatige weg over te brengen.     

Effect of host plants on fitness traits and detoxifying enzymes activity of Helopeltis theivora, a major sucking insect pest of tea

Helopeltis theivora Waterhouse (Heteroptera: Miridae) is a major sucking insect pest of tea (Camellia sinensis) which feeds on a wide variety of alternative host plants. Feeding biology and fitness traits of H. theivora, on two alternative host plants, viz., Mikania micrantha (Asteraceae) and Psidium guajava (Myrtaceae), besides C. sinensis (Theaceae), were studied along with corresponding levels of xenobiotic defense enzymes. C. sinensis is the preferred host of H. theivora. The development time of H. theivora is significantly shorter on C. sinensis (13.3?±?0.16?days) than on the two other hosts, M. micrantha (14.2?±?0.22?days) and P. guajava (14.7?±?0.23?days). Similarly, the fecundity (C. sinensis: 172.6?±?4.5 eggs/female, M. micrantha: 128.6?±?4.4 eggs/female, P. guajava: 118.7?±?3.3 eggs/female), oviposition period (C. sinensis: 24.1?±?0.7?days, M. micrantha: 22.5?±?0.6?days, P. guajava: 21.7?±?0.8?days) and hatchability (C. sinensis: 80.9?±?1.9%, M. micrantha: 69.4?±?1.6%, P. guajava: 64.1?±?1.7%) are recorded to be significantly higher on C. sinensis. The age at reproductive maturity and egg incubation periods were lower on C. sinensis than on the two other host plants. Host-based variation in H. theivora fitness traits is interpreted in light of differential activity of three principal xenobiotic detoxifying enzymes, the general esterases (GEs), glutathione S-transferases (GSTs) and cytochrome P450 monooxygenases (CYPs). The activities of these enzymes in H. theivora were significantly enhanced when the insect fed on M. micrantha and P. guajava as compared with on C. sinensis.     

Over enige insecten in lisdodden

Summary Observations on the biology ofLimnaecia phragmitella Stt. (fam. Momphidae, Lepid.) — made in the Netherlands — are mentioned.The species was previously considered as being rare but now is known to be numerous in a few areas. The caterpillars live in the heads of Typha where they feed on the seeds and later on the core. They hibernate when halfgrown, develop further in the spring and early summer and pupate in June; the moths appear during July.The species has a worldwide distribution: England, Central and Southern Europe, Northern Africa, Australia, New Zealand and the United States of America. In the latter country it was studied byP. W. Claassen together with a number of other Typha-insects occurring in the U.S.A. (Cornell Un. Memoir 47, Oct. 1921).The present author has found an hemipteron,Chilacis typhae Perris (Lygaeidae), in Typha heads occurring together with the caterpillars ofLimnaecia. This insect has also been reported in the literature as being rare in the Netherlands. It is suspected of living on the caterpillars but this has not been shown.     

Cigar‐end disease of banana in the southern region of Oman (Dhofar)

Abstract

Cigar‐end disease of banana, Verticillium theobromae has become apparent in the southern region of Oman, and is prevalent under warm and humid conditions. Benomyl and thiabendazole were found to effectively control V. theobromae in artificially induced cigar‐end disease.     

Species of Botryosphaeriaceae associated on mango in Brazil

The aim of the present study was to assess diversity in the Botryosphaeriaceae on trees and fruit of mango (Mangifera indica L.) in a semi-arid region in northeastern Brazil in which most exported fruit in the country are produced. Using morphological characteristics and DNA sequence data (ITS-1, ITS-2 and 5.8S rDNA) we confirmed the presence of Lasiodiplodia theobromae in the region, and for the first time report Fusicoccum aesculi and Neofusicoccum parvum. L. theobromae was prevalent in the Assú Valley and F. aesculi and N. parvum were in the São Francisco Valley. In fruit inoculations, L. theobromae and N. parvum were more virulent than F. aesculi.     

Een virus inAtropa belladonna

Summary In a bgarden at Baarn, The Netherlands,Atropa belladonna plants, grown from seed, showed symptoms similar to those described bySmith (1946, 1957) for Belladonna mosaic. After inoculation of solanaceous test plants with sap from diseased plants, the following species showed symptoms:Atropa belladonna L.,Capsicum annuum L.,Hyoscyamus niger L.,Nicandra physaloides Gaertn.,Nicotiana glutinosa L.,Nicotiana tabacum L. var. Samsun,Petunia hybrida andPhysalis floridana Rydb. The symptoms suggest that the virus may be identical with that described bySmith. A high virus concentration was found inHyoscyamus niger. Nicandra physaloides, Petunia hybrida, Physalis floridana, in the roots and the pericarp of diseasedAtropa plants, and also inSolanum nigrum L. andDatura stramonium L. The latter two species showed hardly any symptoms. A. low virus concentration was found inCapsicum annuum, though this plant showed severe symptoms.The dilution end point of the virus was between 10^–3 and 10^–4; virusinactivation occurred between 70° and 80°C.In electron micrographs the rod-shaped virus particles appeared similar to those of rattle virus.Virus could be detected in the roots of tobacco plants after the leaves had been inoculated with sap of diseasedAtropa-plants (Table 1). The reverse did not occur. Following immersion of the roots of tobacco plants in virus-containing sap these plants were potted in steamed soil. Subsequently the roots proved to be infected but the stems and leaves contained no virus. However,Atropa plants treated in the same way, did show leaf symptoms.It appeared, that the roots of young, healthy tobacco plants could become infected with virus, when grown in naturally infested soil for only tow days (Table 2). Fungus cultures isolated from diseased roots did not show any infectivity. Nematodes are probably the vectors of this virus (Sol, Van Heuvel & Seinhorst, 1960).Met medewerking van Merr.J. M. Dekhuyzen-Maasland, Dr. S. Gayed (Karthoum), Mej.C. van Heuven, C. de Vooys en Mej.R. van Wessem.     

Effect of GRAS compounds on mycelial growth, pectic enzyme activity and disease severity of postharvest pathogens on rambutan (Nephelium lappaceum)

The GRAS compounds cinnamaldehyde (at 30 ppm), acetaldehyde (at 70 ppm), benzalde-hyde (at 50 ppm) and potassium metabisulphite (at 250 ppm) either completely inhibited or significantly reduced thein vitro mycelial growth ofGliocephalotrichum microchlamydosponim,Colletotrichum gloeosporioides andBotryodiplodia theobromae, the causative fungi of brown spot, anthracnose and stem end rot, respectively, of rambutan fruits,Nephelium lappaceum. The four compounds also significantly reduced the severity of all three diseases and the activity of pectic lyase and polygalacturonase enzymes secreted by the three fungi.     

Identity of red currant spoon leaf virus

Summary Red currant spoon leaf virus, isolated from red currant in The Netherlands, is a strain of raspberry ringspot virus; it shares most of its antigenic groups with the type strain from Scottish raspberry but causes distinctive symptoms inPetunia hybrida. It differs from tomato ringspot virus, obtained byHildebrand (1942) from red currant in the United States.Klesser's (1951) red currant ringspot virus is probably the same as red currant spoon leaf virus.Samenvatting Het hier beschreven onderzoek heeft uitgewezen, dat het in Nederland uit rode bes geïsoleerde lepelbladvirus (van der Meer, 1960) een stam van het ringspot-virus van framboos is. Hoewel het lepelbladvirus de meeste antigenen gemeen heeft met de type-stam van het framboze-ringspot-virus, die uit een Schotse frambozeplant werd verkregen (tabel 1), kunnen beide worden onderscheiden op grond van de symptomen die zij opPetunia hybrida teweegbrengen. Het lepelbladvirus verschilt van het ringspot-virus van tomaat, dat in de Verenigde Staten doorHildebrand (1942) uit rode bes werd geïsoleerd. Het doorKlesser (1951) bestudeerde ringspot-virus van rode bes is waarschijnlijk hetzelfde als het lepelbladvirus.     

Investigation ofHippeastrum mosaic virus inHippeastrum hybridum

An attempt was made to identify a mosaic disease inHippeastrum hybridum. Infectious virus material could be demonstrated in roots, leaves, stem, perianth, stamen and pistil. Inclusion bodies were found in the epidermis of leaves, stem, spatha leaves and in the perianth. Virus concentration in a young stage was high but decreased by aging of the perianth. Efforts to transmit the virus by aphids failed. However, the virus was transmitted by seed in a few cases. Plants of 30 species reacted negatively upon inoculation with the virus.Hippeastrum hybridum, Gomphrena globosa, Chlorophytum spec. andLycopersicum esculentum could be infected experimentally. On account of the host range and presence of inclusion bodies the mosaic symptoms inHippeastrum are not caused by tomato spotted wilt virus or Cucumber mosaic virus. Results suggest that the virus under investigation is theHippeastrum mosaic virus. Dr.M. K. Corbett, Wageningen, succeeded in purifying the virus by density gradient centrifugation. Whe preparation contained flexuous rod particles. Plants ofDatura stramonium, Nicotiana glutinosa andN. tabacum Samsun could be infected. Within two weeks after inoculation with purified virus solution these plants showed systemic symptoms.

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Samenvatting In een kwekerij te Hoorn werden planten vanHippeastrum hybridum aangetroffen, die mozaïekverschijnselen vertoonden. De oorzaak hiervan werd nagegaan. Infectieus virusmateriaal kon worden aangetoond in wortels, bladeren, bloemstengel, bloemdekbladen, meeldraden en stijl. Celinsluitsels kwamen voor in de epidermis van bladeren en stengel en in de bloemschede. De aanwezigheid van insluitsels in het bloemdek was afhankelijk van de ouderdom van de bloem. Er schijnt een omgekeerd evenredige relatie te bestaan tussen de virusconcentratie en het aantal insluitsels in bloemen.Pogingen om het virus over te brengen door bladluizen mislukten. In enkele gevallen had zaadoverdracht plaats.Dertig plantesoorten reageerden negatief op een inoculatie met virushoudend sap.Hippeastrum hybridum, Gomphrena globosa, Chlorophytum spec. enLycopersicum esculentum konden wel worden geïnfecteerd. Gezien de waardplantenreeks en het voorkomen van celinsluitsels kunnen de mozaïeksymptomen inHippeastrum niet toegeschreven worden aan Tomato spotted wilt-virus of het komkommer-mozaïek-virus, maar is het waarschijnlijk dat zij worden veroorzaakt door hetHippeastrum-mozaïek-virus, reeds beschreven doorBrierley (1948),Johnson (1951) enProcenko & Procenko (1964).Dr.M. K. Corbett, Wageningen, slaagde erin het virus te zuiveren door middel van density gradient-centrifugering.Datura stramonium, N. glutinosa enN. tabacum Samsun werden systemisch ziek binnen twee weken na inoculatie met de gezuiverde virus-oplossing.