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.     

Cold hardiness in the two-spotted spider mite (Tetranychus urticae Koch)

Summary The effect of temperatures below 0° C on different stages of the two-spotted spider mite, and in particular on active adult females, has been investigated.Survival of active females at-5° was higher at approximately 100% relative humidity than at a lower degree of humidity. Higher rates of survival were also caused by acclimation of active females and larvae for one day at +5° before storage at-15°. No differences in cold-hardiness were found in active females from an organophosphorous resistant strain and a susceptible strain, and the ability to survive depended on the time-temperature exposures (see Fig. 3).Eggs were killed very rapidly at-15° C, while larvae survived longer exposures than active females. Compared at the LT₅₀ level females in diapause survived three times the exposure endured by acclimated active females.Supercooling points measured at a rate of cooling of 2° C per minute were highest in diapausing females and lowest in eggs. Acclimation had no effect on the supercooling points of active females. All stages were killed by freezing. It seems likely that the difference in survival between acclimated and not acclimated active females at-15° is caused by different ability to live in a supercooled state.

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Zusammenfassung Es wurde die Wirkung von Temperaturen unter 0° auf verschiedene Stadien der Bohnenspinnmilbe, insbesondere auf aktive erwachsene Weibchen untersucht.Die Überlebensrate aktiver Weibchen war bei nahezu hundertprozentiger relativer Luftfeuchtigkeit höher als bei niederer Feuchtigkeit. Höhere Überlebensraten wurden auch durch Akklimatisation aktiver Weibchen und Larven für einen Tag bei 5° vor der Behandlung mit-15° erreicht. Es wurden keine Unterschiede in der Kältewiderstandfähigkeit aktiver Weibchen eines phosphorsäureesterresistenten und eines anfälligen Stammes gefunden. Die Überlebensfähigkeit hängt von Dauer und Temperatur der Einwirkung ab.Eier wurden von-15° sehr schnell abgetötet, während Larven längere Einwirkungszeiten überlebten als aktive Weibchen. Bei einem Vergleich der LT₅₀ überlebten diapausierende Weibchen dreimal längere Einwirkungszeiten, als sie von akklimatisierten aktiven Weibchen ertragen wurden.Unterkühlungspunkte—gemessen bei einer Abkühlungsrate von 2° pro Minute—lagen bei diapausierenden Weibchen am höchsten und bei Eiern am niedrigsten.Akklimatisierung hatte keinen Einfluß auf die Unterkühlungspunkte aktiver Weibchen. Durch Gefrieren wurden alle Stadien getötet. Es erscheint möglich, daß der Unterschied im Überleben akklimatisierter und nichtakklimatisierter Weibchen bei-15° durch die verschiedene Fähigkeit bedingt ist, in einem unterkühlten Zustande zu leben.

     

Biotypes of Dasineura tetensi, differing in ability to gall and develop on black currant genotypes

Variation in damage levels on certain black currant, Ribes nigrum L., genotypes, caused by the black currant leaf midge, Dasineura tetensi (Rübs.) (Diptera: Cecidomyiidae), has been observed in northern Sweden. I investigated whether this variation is due to variation in virulence among midges. From a field population of midges, I successfully selected for virulence and avirulence, respectively, on the resistant black currant genotype cultivar `Storklas' (called resistant genotype). The performance of avirulent and virulent midge larvae on two black currant genotypes were studied in experiments where first or second instar larvae were artificially transferred. There were no differences in larval survival and developmental rate between the two midge types when transferred to the susceptible currant genotype `7801–31' (called susceptible genotype). Larvae of the virulent strain established galls and developed on `Storklas' but development was initially slower there than on the susceptible currant genotype. Larvae of the avirulent strain suffered high mortality or remained in first instar on that same currant genotype when transferred alone, but developed readily if transferred together with virulent larvae. Larvae transferred in second instar to host plants susceptible to the larvae resumed feeding and developed further to maturity. Second instar larvae were also able to establish new galls even though these galls were not as well developed as those caused by first instar larvae. Black currant plantations in northern Sweden were surveyed and local midge populations were found to be composed of either avirulent, virulent or a mixture of both midge types. Virulent midges were not restricted to plantations where resistant currant genotypes were grown. I conclude that, at least, two biotypes of the midge exist, and that those two are distinguished by the ability to gall and survive on `Storklas'.     

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.     

鄱阳湖区黄毛鼠(Rattus losea)繁殖生态

2015—2016年对鄱阳湖区的滨湖农田和湖滩草洲的黄毛鼠种群繁殖进行了研究。研究结果表明,其种群雌雄比为81.36%,在不同的季节、生境和年龄组之间都有一定的差别,雌雄比在夏季较低,春、秋、冬季的雌雄比都超过了50.00%,其中冬季的达到了133.33%。农田和湖滩草洲上的雌雄比也都超过了50.00%,且农田的高于湖滩草洲的。在不同的年龄组之间,雌雄比最高的为幼体组140.00%,其次为成体90.20%。所有雌鼠全年的怀孕率为45.26%,平均胎仔数为6.74只,繁殖指数为1.36。夏和秋季的怀孕率都较高,冬季未捕获到怀孕鼠,仅捕获到有怀孕经历(有宫斑)的雌鼠。从繁殖指数看,春、秋季维持高峰水平,且秋峰高于春峰。雌性黄毛鼠总的参产率为71.58%,各季节间变化呈现单峰曲线,夏季最高,其次是秋季和春季,冬季停止怀孕。随着年龄的增长,平均胎仔数有明显增加的趋势,成体组胎仔数最高,而繁殖指数也是以成体组最高,说明成体组是种群中繁殖的主体。雄性黄毛鼠的睾丸下降率全年总计为81.36%,分四季平均为79.64%,春、夏、秋季都维持在较高水平,冬季最低。下位睾丸的大小季节性差异极显著(P0.01),春季与冬季相比,有显著性差异,说明开春后,雄性黄毛鼠在生殖潜能上已有明显变化。这些特征与雌鼠的繁殖高峰基本吻合。说明黄毛鼠主要在春、夏、秋季繁殖,繁殖盛期在春、秋季。从不同的年龄组看,幼体组个体不参与繁殖,亚成体组个体开始参与繁殖,繁殖主体是成体组个体。     

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.     

Cold hardiness in the black rice bug, Scotinophara lurida

Abstract.  The mechanisms and strategies for winter survival of the black rice bug Scotinophara lurida are investigated along with the relationship between cold hardiness and diapause. The ability of S. lurida to survive subzero temperatures varies depending on developmental stage, temperature and exposure duration. Mean supercooling point (SCP) varies from –7.6 to –10.7 °C with developmental stage, but is not significantly different between stages examined. The SCP also varies with season, being lowest in January and increasing rapidly in February and remaining almost at the same level (–7.3 to 9.6 °C) until April The osmolality of haemolymph of field-collected S. lurida adults rises dramatically from 53.9 mOsm kg⁻¹ in August to 75.3 mOsm kg⁻¹ in December, and then declines linearly to 57.0 mOsm kg⁻¹ in May. Field-collected S. lurida adults show a peak glucose content in October, glycerol content in November and trehalose content in December. Only trehalose content decreases after the application of the juvenile hormone analogue, fenoxycarb, suggesting that trehalose is a cryoprotectant during diapause. These various physiological and biochemical traits related to cold tolerance in S. lurida may be, at least in part, under the control of juvenile hormone through the reproductive diapause programme.     

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。     

Strategies of freeze avoidance in larvae of the goldenrod gall moth,Epiblema scudderiana: Laboratory investigations of temperature cues in the regulation of cold hardiness

Laboratory manipulations of ambient temperature were used to investigate the role of temperature in triggering or modulating cold-hardiness adaptations, supercooling-point depression and cryoprotectant accumulation, in larvae of the goldenrod gall moth, Epiblema scudderiana (Clemens), a freeze-intolerant species. Low temperature strongly facilitated cryoprotectant synthesis; larvae subjected to a 1°C per day decrease in temperature showed a major increase in the rate of glycerol synthesis when temperature fell below 5°C with highest rates of synthesis, greater than 90 μmol g⁻¹ d⁻¹, at temperatures between 0 and −10°C. Conversely, abrupt rewarming of larvae from −18 to 23°C in mid-November stimulated a rapid loss of glycerol (from a starting level of 1763 ± 278 μmol/g wet weight) with a half time of only 1.5 days. Supercooling-point depression was not keyed to ambient temperature but appeared to be an endogenous event occurring over the same time interval in laboratory animals held at warm or cold temperatures, as well as in outdoor animals. Rewarming of cold-adapted larvae in November resulted in only a small rise in supercooling point (and did not break diapause) but rewarming in February resulted in a 19°C increase in supercooling point in 4 days, followed rapidly by pupation.     

不同生境下入侵植物胜红蓟种群构件生物量分配特性

为探究入侵植物胜红蓟在种群构件水平上的生长特性,以更好地了解其整体的生存策略和入侵性,通过测定胜红蓟各构件的生物量、各构件生物量相关性、繁殖构件/营养构件比和根冠比,对Ⅰ房前屋后、Ⅱ菜园地、Ⅲ桔园和Ⅳ路边4种不同生境下的胜红蓟种群构件的生物量分配进行了分析研究。结果表明:不同生境下胜红蓟种群各构件的生物量既存在差异,又存在相同的趋势,即:茎生物量叶生物量根生物量花果生物量;生境Ⅱ胜红蓟总生物量、茎、叶和花果生物量均最大,生境Ⅳ的均最小,两者之间均存在显著差异(P0.05);不同生境中胜红蓟种群的根、茎、叶、花果生物量分配与其各构件生物量大小顺序并不一致,前者各生境间的差异小于后者各生境间的差异;4种生境下繁殖构件与营养构件生物量比大小顺序依次为ⅣⅢⅡⅠ,其值分别为0.069、0.061、0.050和0.042,根冠比大小顺序依次为ⅢⅠⅣⅡ,其值分别为0.211、0.179、0.154和0.090;胜红蓟植株株高与各构件及各构件之间存在极显著正相关(P0.01),株高与各构件的相关性中,株高与茎生物量的相关性最强,相关系数为0.525,各构件的相关性中,茎生物量与叶和花果生物量的相关性较强,其相关系数均大于0.900。胜红蓟种群在不同生境下各构件的生物量、繁殖构件/营养构件比和根冠比表现出的差异显示了其较强的表型可塑性和对异质环境的适应性,可能增强了其入侵性。不同生境下胜红蓟种群各构件生物量相同的趋势及生物量分配比间相对较小的差异显示了胜红蓟种群构件生物量分配模式的相对稳定性。胜红蓟种群各构件间的极显著相关性显示了其整体性的生存策略。     

The sex ratio of the spider mite Tetranychus urticae

Inbred lines that differed in the ratio of females to males were selected. These tended to breed true and the trait for a high frequency of daughters was semi-dominant and expressed as a control of arrhenotoky by the mother. A small maternal effect altered the sex ratio of genetically similar females. The variability of the sex ratio in nature would appear to be a genetic polymorphism.

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Résumé Il a été possible, à partir de la descendance de femelles isolées, et par croisement de retour entre frère et sur, d'isoler deux lignées différant par leur sex ratio: l'une présentant une faible proportion de femelles, l'autre une majorité de femelles. Des croisements entre ces deux lignées montrent que le caractère «majorité de femelles» est semi-dominant, mais les croisements réciproques diffèrent à cause d'un petit effet maternel. Un croisement de retour entre des femelles de la génération F¹ et des mâles de la lignée présentant une faible proportion de femelles, confirme l'hypothèse que le sex-ratio des ufs pondus est déterminé par quelques loci qui contrôlent la semi-dominance des caractères «haute proportion de femelles». Le caractère du sex ratio peut être transmis soit par le mâle, soit par la femelle, mais l'influence maternelle est plus forte. Les différences observées dans la nature quant au sex ratio et à sa variabilité dans les familles d'une population paraissent donc être dues à un polymorphisme génétique.

     

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.     

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.     

Divergent mechanisms of frost-hardiness in two populations of the gall fly, Eurosta solidaginsis

Two populations of the gall fly Eurosta solidaginsis utilize different strategies to endure seasonal exposure to temperatures below freezing. Both populations are freezing tolerant. In north temperate populations, supercooling points rise from ?10.2°C to ?6.2°C following exposures to temperatures below freezing. This level is maintained throughout winter and ensures frequent and prolonged periods of tissue freezing. South temperate populations depress the supercooling point to ?14.2°C during autumn and early winter, and this depression precludes extracellular ice formation during periods of supra-optimal temperature fluctuations. During mid-winter, supercooling points rise to the same level as in northern groups.Both populations accumulate three principal cryoprotective agents following first frost exposures (glycerol, sorbitol and trehalose). Cryoprotectants levels do not peak in northern populations until 4–6 weeks after first frost. In southern populations the accumulation profile is characterized by a high initial rate of synthesis, a protective overshoot and pronounced seasonal fluctuations. The relative survival advantages of each strategy are discussed.     

Seasonal changes in cold hardiness of Ophraella communa

Insects can prepare themselves to tolerate subzero temperatures through various physiological changes, such as the alteration in body water or glycerol content. Indeed, it has been hypothesized that increasing glycerol body content has the benefit of decreasing the temperature necessary to freeze their body water and therefore increasing the supercooling point (SCP) and the cold hardiness. We here studied physiological plasticity in cold tolerance in Ophraella communa LeSage (Coleoptera: Chrysomelidae), a potential biological control agent of an invasive plant, the common ragweed, Ambrosia artemisiifolia L. (Asteraceae). Pupae of O. communa were collected from June to October, and the water and glycerol contents and the SCP of emerging adults were assessed. We found that SCP, water, and glycerol contents of beetles fluctuated significantly with season. Glycerol content of males and females increased with decreasing temperature between July and October, and glycerol content reached a maximum in October in the field. The lowest SCP was observed in adults in October prior to overwintering, and the highest SCP was evident in the summer population in July. Thus, cold hardiness of the beetles in the autumn population was significantly higher than in the summer population. We therefore conclude that cold tolerance, via changes in the relative composition of their body fluids and fats, is a plastic trait that can be influenced by fluctuations in abiotic factors (e.g., temperature) throughout the breeding season of the insect.     

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.