The prospects for cryopreservation of noctuid eggs in the mass production of Trichogramma spp.

BioControl - Successful long-term cryopreservation of lepidopteran eggs for the mass production of parasitoids of the genus Trichogramma Westwood (Hymenoptera: Trichogrammatidae) requires a more...     

不同赤眼蜂对灰白蚕蛾卵的偏好性比较

在实验室条件下,利用不同种类和品系的赤眼蜂Trichogramma spp.对灰白蚕蛾Ocinnara varians选择性和灰白蚕蛾对其适合性的差异,筛选防治灰白蚕蛾的有效蜂种和品系,结果表明,在供试的8种赤眼蜂中,松毛虫赤眼蜂Trichogramma dendrolimi、短管赤眼蜂Trichogramma pretiosum、舟蛾赤眼蜂Trichogramma closterae、暗黑赤眼蜂Trichogramma euproctidis和拟澳洲赤眼蜂Trichogramma confusum 5种赤眼蜂较其它3种赤眼蜂更偏好寄生灰白蚕蛾的卵,每雌蜂在灰白蚕蛾卵上的接触次数、寄生卵数都相对较多,且羽化率也都较高.广赤眼蜂Trichogramma evanescens对灰白蚕蛾卵的接触次数最多,为6.60次/雌,但寄生卵数却很少,为4.55粒/雌,羽化率也很低,为27.86%.玉米螟赤眼蜂寄生灰白蚕蛾的卵比较多,为14.35粒/雌,但对灰白蚕蛾卵的接触次数很少,仅1.20次/雌,羽化率也很低,为24.17%.卷蛾分索赤眼蜂对灰白蚕蛾卵的接触次数和寄生卵数最少的,分别为0.60次/雌和2.20粒/雌,且被寄生卵全部不能发育成功.综合分析结果表明,松毛虫赤眼蜂是最适合寄生灰白蚕蛾卵的赤眼蜂种,可作为其生物防治的潜在寄生蜂.     

不同温度下稻螟赤眼蜂在黏虫卵上的种群生命表

稻螟赤眼蜂Trichogramma japonicum Ashmead是水稻二化螟Chilo suppressalis(Walker)的优势卵寄生蜂。本文构建了以黏虫卵为中间寄主,稻螟赤眼蜂在20℃、25℃、30℃、33℃四个温度条件下的生命表。研究结果表明利用黏虫卵繁育稻螟赤眼蜂时,不同温度下其生长发育和繁殖均存在显著差异,雌蜂平均寿命随温度的升高呈下降趋势,在20℃条件下,雌蜂平均寿命为1.44 d,显著长于其它温度,当温度为30~33℃时,雌蜂寿命最短,平均为0.59 d。在温度为20℃和25℃时,稻螟赤眼蜂的羽化率显著高于温度较高的30℃和33℃,平均为94.73%。在25℃条件下,黏虫卵繁育的稻螟赤眼蜂的净生殖力(R 0)最大,达到31.9176,单雌寄生卵数最多,为32.88个,表现出最强的繁殖能力,而在30℃条件下,瞬时增长率r m和周限增长率λ达到最大值。综合生命表参数、单雌寄生黏虫卵数、寿命、羽化率等指标,利用黏虫卵工厂化繁殖稻螟赤眼蜂的最佳温度为25℃。本研究为利用黏虫卵大量繁殖稻螟赤眼蜂提供了有价值的参考。     

Long-term stability of enzymes in human serum stored in liquid nitrogen

We analyzed the stability of the enzymes alpha-amylase (EC 3.2.1.1), alkaline phosphatase (EC 3.1.3.1), alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.1), creatine kinase (EC 2.7.3.2), glutamate dehydrogenase (EC 1.4.1.3), gamma-glutamyltransferase (EC 2.3.2.2) and lactate dehydrogenase (EC 1.1.1.27) of a human serum pool during storage in liquid nitrogen for a period of 10 months. Except amylase and creatine kinase, all enzymes were stable. Amylase increased in activity, creatine kinase activity decreased. Therefore, human serum stored at -196 degrees C can be used as satisfactory substitute for lyophilized enzyme control serum in internal quality control and stable enzyme material for optimization of methods.     

Fertility life table parameters of different strains of Trichogramma spp. collected from eggs of the carob moth Ectomyelois ceratoniae

Fertility life table parameters were assessed for five populations (strains) of two Trichogramma species, T. embryophagum Hartig and T. principium Sugonyaev & Sorokina, collected from eggs of the carob moth Ectomyelois ceratoniae (Zeller) in Iranian pomegranate orchards. Four combinations of two constant temperatures (25°C, 30°C) and two relative humidity levels (50% RH, 70% RH) were used. The overall intrinsic rate of natural increase (r_m) was significantly decreased with decreased relative humidity but was uninfluenced by temperature. The highest and lowest r_m values were observed in T. embryophagum from Qum (0.34 ± 0.004) and T. embryophagum from Varamin (0.13 ± 0.01), respectively. Two‐way interaction analyses revealed that the strains had significantly different responses in their r_m values at different temperatures and relative humidities. In general, r_m values were significantly higher at 25°C and 70% RH than at 30°C and 50% RH. The Qum strain of T. embryophagum was the most promising candidate to be considered as a biocontrol agent against E. ceratoniae due to its high reproductive rate (0.27 ± 0.01) at conditions (30°C and 50% RH) similar to the actual climatic conditions in Iranian pomegranate orchards during the major part of the growing season.     

Lipid and hydrocarbon production byBotryococcus spp. under nitrogen limitation and anaerobiosis

The production of lipids and hydrocarbons in batch cultures of the algaeBotryococcus braunii andB. protuberans has been studied with respect to nitrogen limitation under aerobic and anaerobic conditions. Nitrogen deficiency significantly decreased the dry weight, chlorophylla and protein contents but the amounts of carotenoids, carbohydrates and lipids increased in both the species. Nitrogen starvation gave a 1.6-fold increase in lipid content. Anaerobiosis under nitrogen deficient conditions gave greater lipid production than anaerobiosis in nitrogen supplemented medium. Under nitrogen deficiency, the hydrocarbon fraction increased and the polar lipids decreased. Anaerobiosis induced hydrocarbon synthesis more significantly than nitrogen deficiency but decreased other non-polar and polar lipids.     

Maturation and hatching of eggs from silkworm ovaries preserved in liquid nitrogen

Ovarian imaginal discs prepared from fifth-instar larvae of the silkworm, Bombyx mori were treated with graded concentrations of glycerol, cooled at a rate of 1°C/min to ?35°C and preserved in liquid nitrogen for 2 days or more and then rapidly thawed (500°C/min). The frozen and thawed ovaries were transplanted into fifth-instar female larvae, in which more than 20% of the ovaries developed to produce mature eggs with a chorion according to the state of host development. By parthenogenetic activation, the mature eggs started embryogenesis and hatched to produce larvae. About 50% hatching occurred in the eggs developed in a C 108 × Cambodge host, and about 10% in a C 108 × Aojuku host. The hatched larvae completed post-embryonic development as did the normal larvae.     

Behavioural variations among strains of Trichogramma spp.: Host-age selection

Host-age selection by several Trichogramma spp. strains was examined in laboratory choice-tests, in order to use this as a criterion to select a candidate strain for inundative releases against lepidopterous pests of cabbage in the Netherlands. The behaviour of individual females toward combinations of host eggs of two different ages (zero vs 2 and 1 vs 3-day-old) of the host species Mamestra brassicae, Pieris brassicae and P. rapae was observed directly. Host age generally did not appear to affect contact or acceptance of eggs of either host species, except that oviposition was generally lower in the oldest M. brassicae eggs. The duration of the oviposition behaviour was sometimes influenced by host-age. All strains were able to discriminate between parasitized and unparasitized hosts by external or internal examation. The lack of variation among the strains suggests that the host-age selection pattern of a given host-Trichogramma combination is predominantly dependent on the host species. The results are discussed in relation to optimal foraging theory.

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Résumé Afin de sélectionner une souche candidate de Trichogramma sp. pour des lâchés inondatifs contre les Lépidoptères, pestes du chou aux Pays-Bas, la sélection hôte-âge de plusieurs souches de Trichogramma spp., issues d'un éventail de 60 souches, a été examinée en laboratoire par des tests de choix. Le comportement de femelles individuelles, mises en présence de combinaisons d'oeufs-hôtes d'âges différents (zero ou 2 jours et 1 ou 3 jours) des espèces-hôtes Mamestra brassicae, Pieris brassicae et P. rapae, a été observé directement. En général, l'âge de l'hôte ne semble pas affecter le contact et l'acceptation des oeufs quelque soit l'espèce-hôte. La ponte diminue généralement dans les oeufs les plus âgés de M. brassicae, mais pas chez les autres espèces. La durée du comportement de ponte est parfois influencée par l'âge de l'hôte. Toutes les souches ont montré la capacité de discriminer entre les hôtes parasités et nonparasités, a l'examen externe ou interne et ceci, indépendamment de l'âge de l'hôte. Le manque de variation parmi les souces suggère que le mode de sélection hôte-âge est surtout caractéristique de l'espèce-hôte. Les resultats sont discutés en relation avec la théorie de fourrage optimal.

     

A contribution to the quantitative evaluation of yeast cultures stored in liquid nitrogen

Different ways of the evaluation of viability of cultures stored in liquid nitrogen are compared. The streaking technique is recommended for a rapid evaluation. It is sufficient to determine the suitability of the medium, of cryopreservatives and of the whole procedure. On storage of melted cultures for 1–7 d at 4 °C it was found that the cultures could be transported directly in a suitable package maintaining the low temperature on the condition that the transportation would not last longer than 5 d.     

Loss of vacuum in rubber stoppered vials stored in a liquid nitrogen vapor phase freezer

A total of 1885 rubber stoppered 3-ml vials (NS-33 and NS-51 glass (expansion sizes), sealed under vacuum, were subjected to the ultracold temperatures of a liquid nitrogen vapor phase (LNVP) freezer for 16.5 hr and tested for vacuum loss after equilibration back to 25 °C. The presence of a vacuum in each vial was checked before and after freezing. Results with two lots of vials per glass expansion size showed positive or no negative pressure rather than a vacuum in 46.25% (NS-33), 98.25% (NS-33), 64.72% (NS-51), and 99.38% (NS-51) of the vials. Apparently, the fit or slight misfit of the stopper into the vial opening and the hardness of the butyl rubber stopper at ultracold temperatures enhance the chances of leakage around the stopper area under extremely cold temperatures. Storage of rubber stoppered vials containing lyophilized products sealed under vacuum in LNVP freezers is not advisable.     

Survival of Entamoeba and related amoebae at low temperature-II. Viability of amoebae and cysts stored in liquid nitrogen

It was found that E. histolytica, E. histolytica-like, E. hartmanni, E. invadens, E. terrapinae, E. moshkovskii grown with a mixed bacterial flora, could be recovered after prolonged storage in liquid nitrogen. The longest period yet tested for E. histolytica is 382 weeks (7·3 years). Storage of amoebae of E. ranarum and E. coli was less successful. E. histolytica amoebae grown axenically or monoxenically were less easily stored than those amoebae grown with a mixed bacterial flora. Cysts were non-viable after freezing.E. histolytica amoebae showed the same virulence to rats and sensitivity to emetine after storage in liquid nitrogen, as was observed before freezing.A summary of a recommended procedure for freezing Entamoeba and related amoebae is given.     

Conservation of Ephestia kuehniella eggs as hosts for Trichogramma ostriniae

Mass rearing of numerous biological control agents depends on large amounts of factitious hosts like Ephestia kuehniella eggs. Moreover, production of some parasitoids, such as Trichogramma, requires hosts of high quality. The objective of this study was to determine the optimal conservation method that allows E. kuehniella eggs to remain suitable for parasitism and development of Trichogramma ostriniae for the longest period of time. Fifteen sterilization–conservation treatments were compared: nine consisting of submersion of the eggs in liquid nitrogen as a conservation mode, two consisting of sterilization of the eggs with UV and four consisting of sterilization with freezing at ?15°C. Liquid nitrogen submersion of E. kuehniella eggs did not allow the production of T. ostriniae. The sterilization by exposition to UV light followed by conservation using vacuum packing and refrigeration at 4°C provided the longest conservation of E. kuehniella eggs for T. ostriniae rearing. It was the only treatment (75.4 ± 4.62%) for which the parasitism rate remained over 70% after 2 weeks.     

Cold storage of Trichogramma ostriniae reared on Sitotroga cerealella eggs

Efficient storage of the biological controlagent Trichogramma ostriniae couldimprove current parasitoid production methodsby making the system more flexible andefficient. Initial studies compared emergencerates of T. ostriniae reared onSitotroga cerealella eggs held at 6 °C, 9 °C, 12 °C,15 °C, and 24 °C for up to 8 weeks after parasitism.At 15 °C, emergence occurred in <2 weeks.Emeregence was >80% for parasitized eggsstored at 9 °C and 12 °C for 4 and 6 weeksrespectively. Storage at 6 °C caused asignificant decline in emergence after 2 weeks. Subsequent trials focused on fitness of storedT. ostriniae. Percentage of emergedfemales parasitizing eggs, female longevity,and fecundity were quantified after storage.The percentage of females successfullyparasitizing O. nubilalis eggs wasgreatest for the 9 °C four-week treatment(100%). Compared to 24 °C controls, storage at12 °C for 6 weeks or at 9 °C for 8 weeks reduced thepercentage of females parasitizing. Longevityof females held in cold storage was generallyless than that of controls. Rates of parasitismby stored Trichogramma was generallysimilar to controls after 2 to 4 weeks' storageat 9 °C and 12 °C but declined with storage longerthan 4 weeks. Emergence of progeny of cold-storedfemales was lower than controls for alltreatments. The percentage of female progenyfrom cold stored females was comparable tocontrols up to 4 weeks of storage.     

Suitability assessment of three Trichogramma species in the control of Mythimna separata (Lepidoptera: Noctuidae)

Mythimna separata (Walker) is a serious cosmopolitan pest. Trichogramma species have been used worldwide as biological control agents of lepidopteran pests. However, no data on the control efficiency of Trichogramma species on this pest have been reported. We evaluated the suitability of M. separata eggs for three Trichogramma species, Trichogramma dendrolimi Matsumura, T. ostriniae Pang et Chen and T. japonicum Ashmead, and compared the suitability with that of Corcyra cephalonica (Stainton) eggs. The parasitism rate, development time, emergence rate, female proportion, body size and egg load of female offspring indicated that the M. separata egg is a suitable host for the three Trichogramma species. On the other hand, the non‐emergence rate and the relationship between egg load and body size reflected that M. separata eggs are less suitable for the three Trichogramma species than C. cephalonica eggs. Egg resorption occurred in T. japonicum 4 days after emergence.     

Regulation of nitrogen catabolic enzymes in Bacillus spp.

The levels of the inducible nitrogen catabolic enzymes arginase (L-arginine amidinohydrolase, EC 3.5.3.1) and alanine dehydrogenase (L-alanine:NAD+ oxidoreductase [deaminating], EC 1.4.1.1) from Bacillus licheniformis and histidase (L-histidine ammonia-lyase, EC 4.3.1.3) from Bacillus subtilis and the ammonia assimilatory enzymes from B. licheniformis were determined in cultures grown in the presence of different nitrogen sources. Although the levels of these enzymes were dependent upon the nitrogen source present, induction of the catabolic enzymes in response to the addition of inducer occurred even in the presence of preferred nitrogen sources. Intracellular pool sizes of ammonia, glutamate, glutamine, and alpha-ketoglutarate were measured in continuous cultures of b. licheniformis growing in the presence of different nitrogen sources. A comparison of the pool sizes of these metabolites with the ammonia assimilatory enzyme levels showed that the pools of the metabolites did not change in a manner consistent with their use as regulators of the synthesis of any of these enzymes.     

Variation in biological parameters of Trichogramma spp. purchased from commercial suppliers in the United States

The efficacy of biological controlobtained through releases of commerciallysupplied Trichogramma is influenced by bothabiotic conditions in the field during andfollowing release and an array of biologicalattributes of the released Trichogramma. Thisstudy was undertaken to assess the degree ofvariation that existed among commerciallysupplied Trichogramma in an array of biologicalparameters that potentially may influence thelevel of control that can be expected in aTrichogramma release program. Shipments ofTrichogramma were obtained from 12 commercialsuppliers of beneficial insects over a 2-yearperiod and the following parameters weremeasured: percentage of emergence duringshipping, total percentage of emergence,percentage of females, percentage ofbrachypterous females, percentage ofbrachypterous males, adult female longevity,and species composition. In addition, weestimated the percentage of macropterousfemales that had not emerged prior to the timethe shipment was received, based on the firstfour parameters. Results indicate a high levelof variation in each of these parameters amongsuppliers of Trichogramma and among shipmentsby individual suppliers. The proportion ofnon-emerged macropterous female wasps was lowfor all suppliers (range 2.5–27.7%). Thiswas primarily attributable to the highincidence of brachyptery among female wasps. However, variation among suppliers in theincidence of emergence during shipping and theproportion of female wasps in a shipment alsocontributed to the low proportion ofnon-emerged macropterous female wasps. Inaddition, in 11 of 24 shipments received duringthe 2-year study, the Trichogramma speciesdiffered from that specified by the shipper orthe shipment contained a mixture ofTrichogramma species.