Transference of resistance to black-currant gall mite, Cecidophyopsis ribis, from gooseberry to black currant

Field and insectary tests confirmed that the black-currant gall mite (Cecidophyopsis ribis) is unable to survive on gooseberry and red currant. A dominant gene Ce, controlling resistance to the gall mite, has been transferred from gooseberry to black currant. Resistant, large-fruited, self-fertile black currants of commercial potential have been obtained in the third backcross. One accession of Ribes bracteosum and three of R. americanum proved field susceptible to the gall mite, but twenty-four accessions of other Ribes species remained free from galled buds for at least 3 years in an infection plot.     

Ultrastructure of the black currant gall mite, Cecidophyopsis ribis (Acari: Eriophyidae), the vector of the agent of reversion disease

Electron microscopy of ultrathin serial sections was used to determine the structure and anatomy of the eriophyid gall mite, Cecidophyopsis ribis, the vector of the agent of black currant reversion disease. The composite picture derived from these studies has determined the location of the food canal, and major internal organs of the mite. Detailed ultrastructural studies on the anterior of suitably orientated mites has also provided detailed information on the geometry and complex structure of three sets of stylets in the feeding apparatus. No evidence was found of structures resembling virus-like particles or of other described plant pathogens in the feeding apparatus and food canal of mites obtained from black currant plants affected with reversion disease. However, little or no food was apparently present in the food canal of most mites examined. This is the first detailed report of the anatomy and the ultrastructure of the mouthparts of this important plant pest and vector.     

Field experiments on the spread of black currant reversion virus and its gall mite vector (Phytoptus ribis Nal.)

In two experiments the spread of reversion virus from a row of systemi-cally infected black currant bushes heavily infested by the gall mite vector (Phytoptus ribis Nal.) was predominantly in the direction of the winds prevailing during the dispersal period. On each side of the sources there was a curvilinear decrease of galled buds and of virus infection as distance increased. In another experiment a central source of mites and virus was surrounded by concentric hexagons comprising alternate rows of healthy and virus-infected bushes. At leaf-fall, galls were forty times more numerous on virus-infected than on healthy bushes; plants in the sector downwind developed the most galls and those upwind the least. On both healthy and virus-infected bushes in each sector, the incidence of galls decreased with increasing distance from the source. The gradients of infestation were steeper on healthy than on virus-infected bushes, especially in sectors upwind from the source. In some sectors the infestation gradients were distorted because many of the virus-infected bushes were so heavily infested that most of the buds became galled. The spread of virus to initially healthy plants decreased from 100 to 75% near the source, to zero at the periphery. More bushes became infected downwind from the source than upwind. In each experiment more bushes developed galls than later produced symptoms of virus infection, the incidence of which was positively correlated with the number of galls recorded the previous winter.     

The ontogeny of cold tolerance in the gall fly, Eurosta solidagensis

The lower lethal temperature of many insects indicates an overwintering flexibility as a result of either extensive supercooling or production of cryoprotectants. Ontogenetically, the gall fly (Eurosta solidagensis) utilizes both means of seasonal cryoprotection. All stages except third instar larvae demonstrate supercooling points well below the lowest temperature normally experienced by that particular stage. The third instar larvae exhibit a high supercooling point but are well protected by a cryoprotectant system consisting of glycerol, sorbitol, and trehalose. Glycerol is accumulated, possibly from triglyceride sources, during early autumn and reaches plateau levels (0·6 M) by early winter. Sorbitol synthesis is delayed until freezing exposures and reaches a plateau with glycerol at 0·3 M. It is not until mid-winter that peak trehalose levels are reached (300 mg %). All cryoprotectant levels are a reflection of haemolymph concentrations.Laboratory acclimation experiments further quantify these results. Trehalose synthesis is time and temperature dependent and appears to be affected by developmental processes.     

Seasonal cold hardiness in maritime pine assessed by different methods

Three screening methods—visual scoring (V), relative conductivity (C) and fluorometry (F)—were used to study the genetic variation in cold hardiness among six populations of maritime pine (Pinus pinaster Ait.) comprising both Atlantic and Mediterranean origins. Freezing damage assessments were carried out in three organs—needles, stems and buds—in two seasons, spring and autumn. We found high levels of genetic differentiation among populations for cold hardiness in autumn, but not in spring. Within populations, differences were always significant (p?<?0.05) no matter which organ or screening method was used. Measuring F was the fastest and most easily replicated method to estimate cold hardiness and was as reliable as V and C for predicting the species performance. In autumn, there was a positive correlation between the damage measured in all three types of organs assessed, whereas in spring, correlation among organs was weak. We conclude that sampling date in spring has a crucial impact to detect genetic differences in maritime pine populations, whereas autumn sampling allows more stable comparisons. We also conclude that the fluorometry method provides a more efficient and stable comparison of cold hardiness in maritime pine.     

Low-temperature storage and cold hardiness in two populations of the predatory midge Aphidoletes aphidimyza, differing in diapause intensity

Abstract. The potential for medium-time, low-temperature storage was compared in diapausing larvae of two populations of Aphidoletes aphidimyza , a predatory midge used to control aphids in greenhouses . During 4 months of storage, no statistical decrease of survival rate ( c . 75%) was observed in the population Palamos (field collected). However, a significant decrease (below 50%) was recorded in the population Biobest (commercial, selected for the best performance in greenhouses). Measuring physiological parameters related to the rate of diapause development revealed that the larvae of the population Palamos (in contrast to Biobest ) showed a significant metabolic suppression even at the relatively high temperature of 17°C, a slower rate of glycogen depletion during storage at 3°C and a longer duration of diapause development (a higher intensity of diapause, collectively). A higher capacity for survival at subzero temperatures (cold hardiness), in either the supercooled or frozen state, was also found in the Palamos population. It is suggested that the higher survival at low-temperature storage might be linked directly to the higher diapause intensity. It remains unclear, however, whether and how the performance during low-temperature storage is linked to the capacity for cold hardiness.     

厚壳桂种群在不同群落中的分子生态研究

使用ＡＦＬＰ（Ａｍｐｌｉｆｉｅｄ ｆｒａｇｍｅｎｔ ｌｅｎｇｔｈ ｐｏｌｙｍｏｒｐｈｉｓｍ）方法对南亚热带演替顶级种厚壳桂在２个不同群落,常绿阔叶林和针阔混交林中的遗传分化进行了研究,结果表明,种群的大部分遗传变异（８９．５５％）是由于个体与个体之间的差异造成的,有１０．４５％的遗传变异是由于群落的不同造成的,其显著性检测为极显著。这种结果是由于群落的微环境不同和种群生物学特性造成的。     

The fate ofsepia in small populations ofDrosophila melanogaster

Asepia gene found inD. melanogaster collected in North Carolina, and wildtype flies from North Carolina, Bogotá, Barcelona, and California were used to strt 120 cultures that were maintained by mass transfers of adults every third week for more than a year. The frequency ofsepia was determined in these cultures at the termination of the experiment. Thesepia gene was present in considerable frequency (16%–65%) in all backgrounds except one; in cultures involving wildtype chromosomes from North Carolina, it was virtually eliminated. Each of the wildtype backgrounds exhibited a characteristic final frequency ofsepia, suggesting that they had reached at least quasi-stable equilibria. Although it is likely that the retention ofsepia depended upon the superiority of flies heterozygous for this mutant, the technique does not reveal whethersepia itself was involved in the apparent heterosis.The work reported here was done under Contract No. AT-(30-1)-2139, U. S. Atomic Energy Commission.     

Cold hardiness of the overwintering black carpenter ant

Abstract Cold hardiness was investigated in overwintering field nests of the black carpenter ant Camponotus pennsylvanicus (De Geer) in the Commonwealth of Virginia. No active nest thermoregulation was observed: temperatures of galleries, worker bodies, worker clusters, and larval clusters were within 3°C of ambient temperature. Nest temperatures generally fluctuated less rapidly and severely than did ambient temperature; thus, the nest afforded protection from potentially fatal sudden temperature drops. Glycerol, the only polyol cryoprotectant detected, was found in all castes and larvae. Supercooling points were low and ranged from ? 17°C in major workers to ?22°C in larvae. A second heat release peak, occurring around ? 8°C, was seen in all adults, but it was not observed in larvae. This higher temperature peak in adults probably represents the freezing of the gut contents, as adults were found to overwinter with the crop full or partially full. Larvae did not overwinter with liquid food in the gut.     

Effect of different isolates of Beauveria bassiana on field populations of Lygus hesperus

Lygus hesperus (Knight) (Hemiptera: Miridae) is a particularly damaging pest of many crops in the Western United States. Current control tactics are chemically based and there is some concern over resistance building up in populations. Based on previous laboratory studies conducted in California and Mississippi, USA, two new isolates of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) were selected for field-testing against L. hesperus in California. Alfalfa plots were treated with one of three isolates of B. bassiana (a commercial isolate, an isolate from CA (WTPB2) or an isolate from MS (TPB3)) or the chemical pesticide Warrior T. More than 75% of the adults collected from plots 3 days after application with B. bassiana were infected but no differences in percentage infection occurred among fungal treatments. In addition, approximately 30% of the insects collected from control plots or plots treated with Warrior T were also infected. PCR analysis using SSR markers revealed that the isolate causing most of the infections in fungus treated plots was the isolate applied. A mix of infections was found in control plots and plots treated with Warrior T. Despite high levels of infection, no significant reductions of adult populations occurred until 10–14 days after application when plots treated with Warrior T or B. bassiana had about half the numbers of adult L. hesperus as the control plots.     

The ecology of the free-living stages of Trichostrongylus axei

Callinan A.P.L. 1978. The ecology of the free-living stages of Trichostrongylus axei. International Journal for Parasitology8: 453–456. The development and survival of the free-living stages of Trichostrongylus axei was studied in western Victoria in 1974–1976. For all plots in which development occurred, preinfective larvae (L₁-L₂) were recovered within 0–5 days, infective larvae (L₃) in faeces within 4–28 days and L₃ on herbage and soil within 4–21 days. The mean minimum development time to L₃ on herbage and soil was 12.3 ± 0.7 days and the mean development time to maximum yield of these was 33.8 ± 7.4 days. A mean of 66.7 ± 6.6% of L₃ on herbage and soil were actually found on herbage. Yields of L₃ on herbage and soil varied from 0 to 8.9 % of the number of eggs put out on each plot. Yields varied approximately inversely as the mean daily temperatures for the period until maximum yield. No L₃ were observed to survive over summer.     

Sex pheromone of the female currant borer, Synanthedon tipuliformis: Identification and field evaluation

(E,Z)-2,13-octadecadien-1-ol acetate and (Z)-13-octadecen-1-ol acetate have been identified from the ovipositor extracts of the currant borer, Synanthedon tipuliformis (Clerck), by capillary GC, and the structures were verified by GC-MS. The diene/monoene ratio in the extract was found to be 93:7. Mixtures of these two compounds as well as the diene alone attracted conspecific males in the field.

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Zusammenfassung (E,Z)-2,13-Octadecadienylacetat und (Z)-13-Octadecenylacetat wurden in Ovipositor-Extrakten des Johannisbeerglasflüglers Synanthedon tipuliformis kapillar-gaschromatographisch nachgewiesen. Die Strukturen wurden mittels Gaschromatographisch-Massenspektrometrie bestätigt. Das Verhältnis Dien/Monoen im Extrakt betrug 93:7. Mischungen der beiden Komponenten wie auch (E,Z)-2,13-Octadecadienylacetat allein lockten im Freiland Männchen dieser Glasflüglerart an.

     

The uptake of cationized ferritin by guinea-pig gall bladderin vitro

Summary Tissue pieces of guinea-pig gall bladder were grownin vitro for up to ten days. Over this period at different intervals, specimens were exposed to cationized ferritin in culture medium for 1 h and then grown in ferritin free medium for up to 24 h. Other specimens were grown in culture medium containing cationized ferritin for up to 24 h. Both treatments produced a similar morphological sequence. Electron microscopy at all intervals studied showed the cationized ferritin was first bound by the apical cell membrane, clumped and internalized in large 400 nm vesicles. It was then carried to lysosomes in the region of the Golgi apparatus. Within 1 h, the marker was exocytosed in clumps into the lateral intercellular space, accumulating against the basement membrane in a roughly regular approximately 60 nm array. This pathway of cationized ferritin through the gall bladder epithelium is the same as that followedin vivo although the time taken was shorterin vitro.     

Pathogenicity of Beauveria bassiana and Metarhizium anisopliae to the tobacco spider mite Tetranychus evansi

Seventeen isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and two isolates of Beauveria bassiana (Balsamo) Vuillemin were evaluated for their pathogenicity against the tobacco spider mite, Tetranychus evansi Baker & Pritchard. In the laboratory all the fungal isolates were pathogenic to the adult female mites, causing mortality between 22.1 and 82.6%. Isolates causing more than 70% mortality were subjected to dose–response mortality bioassays. The lethal concentration causing 50% mortality (LC₅₀) values ranged between 0.7×10⁷ and 2.5×10⁷ conidia ml⁻¹. The lethal time to 50% mortality (LT₅₀) values of the most active isolates of B. bassiana and M. anisopliae strains varied between 4.6 and 5.8 days. Potted tomato plants were artificially infested with T. evansi and treated with B. bassiana isolate GPK and M. anisopliae isolate ICIPE78. Both fungal isolates reduced the population density of mites as compared to untreated controls. However, conidia formulated in oil outperformed the ones formulated in water. This study demonstrates the prospects of pathogenic fungi for the management of T. evansi.     

Temperature requirements of a house-dust mite Dermatophagoides pteronyssinus compared with the climate in different habitats of houses

Laboratory test show an optimal development of a house-dust allergen generating mite, Dermatophagoides pteronyssinus (Trouessart) at a temperature of 25° C; after 8 weeks at a temperature of 30° the number of mites is 40% of the number at 25°, at 20° only 15%. In the Dutch climate only in summer is relative humidity in houses high enough to allow rapid population growth, but the average temperature on floors in summer is usually below 20°. In occupied beds and upholstered chairs temperatures increase in a short time to optimal levels for mite breeding, and relative humidity increases by 5–8%. It is to be expected that in summer beds and chairs are suitable breeding places in a temperate climate.

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Zusammenfassung Laborexperimente ergaben eine optimale Entwicklung der Hausstaub-Allergie erzeugenden Milbe Dermatophagoides pteronyssinus bei 25°. Nach 8 Wochen beträgt bei 30° die Anzahl der Milben nur 40% der bei 25° erzielten; bei 20° nur 15%. Im holländischen Klima ist die rel. LF in den Häusern nur im Sommer hoch genug, um eine Milbenpopulation schnell wachsen zu lassen, doch liegt die durchschnittliche Temperatur auf dem Fuboden im Sommer gewöhnlich unter 20°. In Gegenwart von Betten und gepolsterten Stühlen steigt die Temperatur in kurzer Zeit bis zu einer optimalen Höhe und die rel. LF um 5–8%. Man darf annehmen, da in einem gemäigten Klima im Sommer Bette und Stühle geeignete Milbenbrutstätten sind.

     

Survival and photosynthetic activity of different Dinophysis acuminata populations in the northern Baltic Sea

This study deals with a recently found phenomenon in the northern Baltic Sea: the occurrence of the dinoflagellate Dinophysis acuminata in the deep water below the thermocline. This was first observed in July 2001 at the station BY 15 in the Gotland Deep, where a sharp and intensive chlorophyll fluorescence signal was encountered at 77 m depth. The fluorescence peak was due to a dinoflagellate community dominated by Dinophysis acuminata (approximately 18 000 cells l⁻¹). The survival of this community was followed in laboratory incubations in low light (20 μE m⁻² s⁻¹) and low temperature (+5 °C). After 5 weeks incubation, 67–84% of the initial cell abundance was lost, while few D. acuminata cells survived up to 24 weeks in the original sample. During the incubation, the fluorescence signal of the cells became fainter and the chloroplasts smaller and aggregated. On two occasions a D. acuminata cell was found attached to a smaller cell by a thin cytoplasm strand, possibly indicating mixotrophic behavior. During the following summer (2002), the photosynthetic efficiency of D. acuminata collected from thermocline layers of few stations and from the nitracline (75–80 m) at one station was studied in photosynthesis irradiance (P–E) incubations. Photosynthetic activity occurred in all populations, with differences in their photosynthetic carbon uptake rates. Photosynthesis of D. acuminata populations was saturated between 250 and 500 μE m⁻² s⁻¹; maximum cell-specific carbon uptake rates (P_m) ranged from 160–925 pg C cell⁻¹ h⁻¹. The P_m-rates in populations originating below the thermocline and in an artificially darkened population were markedly lower than in populations from upper water layers. The varying maximum photosynthetic rates of these populations may reflect their history, e.g. time spent in different light environments.     

Effects of natural and field-simulated blooms of the dinoflagellate Prorocentrum minimum upon hemocytes of eastern oysters, Crassostrea virginica, from two different populations

Oysters, Crassostrea virginica, from two populations, one from a coastal pond experiencing repeated dinoflagellate blooms (native), and the other from another site where blooms have not been observed (non-native), were analyzed for cellular immune system profiles before and during natural and simulated (by adding cultured algae to natural plankton) blooms of the dinoflagellate Prorocentrum minimum. Significant differences in hemocytes between the two oyster populations, before and after the blooms, were found with ANOVA, principal components analysis (PCA) and ANOVA applied to PCA components. Stress associated with blooms of P. minimum included an increase in hemocyte number, especially granulocytes and small granulocytes, and an increase in phagocytosis associated with a decrease in aggregation and mortality of the hemocytes, as compared with oysters in pre-bloom analyses. Non-native oysters constitutively had a hemocyte profile more similar to that induced by P. minimum than that of native oysters, but this profile did not impart increased resistance. The effect of P. minimum on respiratory burst was different according to the origin of the oysters, with the dinoflagellate causing a 35% increase in the respiratory burst of the native oysters but having no effect on that of the non-native oysters. Increased respiratory burst in hemocytes of native oysters exposed to P. minimum in both simulated and natural blooms may represent an adaptation to annual blooms whereby surviving native oysters protect themselves against tissue damage from ingested P. minimum.