Hessian fly-resistance gene transferred from chromosome 4Mv of Aegilops ventricosa to Triticum aestivum

 A new Hessian fly (Mayetiola destructor) resistance gene from Aegilops ventricosa and its transfer to hexaploid wheat is described. The 4D(4M^v) substitution line H-93-33 derived from the cross [(Triticum turgidum H-1-1×Aegilops ventricosa no. 11)×Triticum aestivum H-10-15] was highly resistant to the Spanish population tested. Resistance seemed to be inherited as a single dominant factor in the F₂ generation resulting from a cross of H-93-33 with its susceptible parent (H-10-15). Resistance in Ae. venticosa no. 10 was located on chromosome 4M^v using M^v wheat/Ae. ventricosa addition lines. The resistance gene transferred from Ae. ventricosa no. 11 to H-93-33 (H27) is allelic with respect to that of Ae. ventricosa no. 10 and is non-allelic with respect to the genes H3 and H6 from Monon and Caldwell respectively. The assignment of H27 gene to chromosome 4M^v is further supported by its linkage to a gene encoding isozyme Acph-M^v1, previously located on chromosome 4M^v in the line H-93-33. A new marker from homoeologous chromosome group 4 (Amp-M^v2) present in H-93-33 and the 4M^v addition line is described. Received: 12 October 1996 / Accepted: 22 November 1996     

THE EFFECTS OF WINTER LENGTH ON THE GENETICS OF APPLE AND HAWTHORN RACES OF RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE)

Host plant-associated fitness trade-offs are central to models of sympatric speciation proposed for certain phytophagous insects. But empirical evidence for such trade-offs is scant, which has called into question the likelihood of nonallopatric speciation. Here, we report on the second in a series of studies testing for host-related selection on pupal life-history characteristics of apple- (Malus pumila L.) and hawthorn- (Crataegus mollis L. spp.) infesting races of the Tephritid fruit fly, Rhagoletis pomonella (Walsh). In particular, we examine the effects of winter length on the genetics of these flies. We have previously found that the earlier fruiting phenology of apple trees exposes apple-fly pupae to longer periods of warm weather preceding winter than hawthorn-fly pupae. Because R. pomonella has a facultative diapause, we hypothesized that this selects for pupae with more recalcitrant pupal diapauses (or slower metabolic/development rates) in the apple-fly race. A study in which we experimentally manipulated the length of the prewintering period for hawthorn-origin pupae supported this prediction. If the period preceding winter is important for apple- and hawthorn-fly pupae, then so too should be the length (duration) of winter; the rationale for this prediction is that “fast developing” pupae that break diapause too early will deplete their energy reserves and disproportionately die during long winters. To test this possibility, we chilled apple- and hawthorn-origin pupae collected from a field site near Grant, Michigan, in a refrigerator at 4°C for time periods ranging from one week to two years. Our a priori expectation was that longer periods of cold storage would select against allozyme markers that were associated with faster rates of development in our earlier study. Since these electromorphs are typically found at higher frequencies in hawthorn flies, extending the overwintering period should favor “apple-fly alleles” in both races. The results from this “overwinter” experiment supported the diapause hypothesis. The anticipated genetic response was observed in both apple and hawthorn races, as allele frequencies became significantly more “apple-fly-like” in eclosing adults surviving longer chilling periods. This indicates that it is the combination of environmental conditions before and during winter that selects on the host races. Many tests for trade-offs fail to adequately consider the interplay between insect development, host plant phenology, and local climatic conditions. Our findings suggest that such oversight may help to explain the paucity of reported fitness trade-offs.     

Studies on population dynamics and spatial distribution of leafhoppers in vineyards (Homoptera: Cicadellidae)

Thirty-two species of Cicadellidae, including the Macropsinae, Agalliinae, Penthimiinae, Aphrodinae, Cicadellinae, Typhlocybinae and Deltocephalinae, 10 of which were already known as phytoplasma vectors, were captured in vineyards using yellow sticky traps. Adult population dynamics of the most abundant species of Penthimiinae and Deltocephalinae were studied over the whole growing season. Penthimia nigra was captured in May and June, Anoplotettix fuscovenosus in June-August, Fieberiella florii in August-October, Macrosteles sexnotatus in May and October, Scaphoideus titanus in July-September, Thamnotettix spp. (Th. confinis, Th. dilutior, Th. exemtus, Th. zelleri) in April-June, while Euscelidius variegatus, Neoaliturus fenestratus, Platymetopius major and Psammotettix spp. (P. alienus, P. confinis) were trapped throughout the growing season. The aggregation level of the above species was investigated by means of Taylor's power law. A. fuscovenosus showed a nearly random distribution in vineyards (0.95 < b < 1.11), while N. fenestratus, P. major and S. titanus were strongly aggregated (1.32 < b < 1.81). The other species showed intermediate levels of aggregation (1.12 > b < 1.32). The results indicate that at least six Deltocephalinae species, A. fuscovenosus, E. variegatus, F. florii, M. sexnotatus, N. fenestratus and S. titanus, known as phytoplasma vectors and commonly found in vineyards, could play a role in Grapevine Yellows (GY) epidemiology. GY transmission trials with these species are needed.     

Effects of wind on movement of Diachasmimorpha longicaudata, a parasitoid of tephritid fruit flies, in a laboratory flight tunnel

Cohorts of mass-reared adult female Diachasmimorpha longicaudata (Ashmead), parasitoids of tephritid fruit fly larvae, were released in a laminar air flow wind tunnel to study the effects of air movement on flight and walking behaviors. Wind in the tunnel was cycled on and off at intervals to simulate gusty conditions observed in the field. Wind speed influenced parasitoid movement during both the wind-on periods and during the calm intervals between gusts. Wind speeds of 0.8 m per second suppressed flight and walking behaviors, while wind speeds of 0.4 m/s stimulated both flight and walking behaviors. There was an exponential increase in the ratio of activity in calm to activity in wind as wind speed increased.     

Life history response of female Mediterranean fruit flies, Ceratitis capitata, to periods of host deprivation

Female medflies were subjected to four different patterns of host deprivation at each of three levels for a 24-day period. Treatments ranged from host absence 8 days post-eclosion to host absence 2 out of 3 days. Survival was recorded daily and egg production was recorded on the days in which hosts were present.The direct effect of host deprivation is to deny females the opportunity to oviposit. This disrupts their reproductive cycle and reduces their overall reproductive effort. Reduced reproductive effort at young ages increases survival (up to 2-fold) and daily reproduction (up to 8-fold) at older ages. Therefore, the long term effect of host deprivation is to postpone senescence.The implications of these findings regarding medfly sensescence are discussed in relation to: (i) reduction in population extinction rates during periods of host scarcity and (ii) egging strategies in medfly mass-rearing.

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Résumé Les femelles de C. capitata ont été privées d'hôtes suivant 4 modalités pendant 3 durées (33, 50 et 67% de leur vie) par période de 24 heures. Les modalités se répartissaient de la privation pendant 8 jours après l'éclosion jusqu'à 1 jour sur 3. La survie a été notée chaque jour et la ponte pour tous les jours où il y avait des hôtes.L'effect direct de l'absence d'hôte est d'empêcher la femelle de pondre. Ceci interrompt leur cycle de ponte et réduit leur activité reproductrice totale. Un effort reproductif réduit des femelles jeunes augmente la survie (jusqu'à 2 fois) et la ponte quotidienne (jusqu'à 8 fois) chez les femelles plus âgées. Ainsi, l'effet à long terme de la privation d'hôtes est d'ajourner la sénescence.Les implications de ces observations sur la sénescence de C. capitata sont discutées quant à: (1) la réduction des taux d'extinction des populations pendant les périodes de rareté d'hôtes; et: (2) les stratégies d'obtention de pontes dan les élevages de masse de C. capitata.

     

ADH allele frequency changes in olive fruit flies shift from olives to artificial larval food and vice versa, effect of temperature

When field collected olive fruit flies, Dacus oleae Gmelin (Diptera: Tephritidae), were maintained on an artificial larval medium or on ripe (black) olives in the laboratory for four consecutive generations, the frequency of alcohol dehydrogenase (ADH) allozymes changed (impressively) only in the flies kept on artifical larval food. When flies reared in the laboratory for about 2 years (allele frequencies of artificially reared flies in equilibrium) were provided ripe olives for oviposition for three consecutive generations, the ADH allozyme frequencies changed substantially within only one generation, remaining stable thereafter. The change was towards the frequency levels of natural populations of flies. Finally, when field collected flies were reared artificially under three different daily temperature regimes (i.e. 17, 17–25 and 25 °C), the general pattern of ADH allozyme frequency changes was not affected by the different temperature regimes. The only difference was that the stable temperatures, especially the high one, exhibited more rapid changes of allele frequencies than the daily fluctuating temperature regime.

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Résumé Quand des lots de Dacus oleae Gmelin (Dipt. Tephritidae) ont été conservés pendant plusieurs générations au laboratoire sur des olives mûres (noires) ou sur un substrat alimentaire larvaire artificiel, la fréquence des allozymes de l'alcohol déshydrogénase n'a changé fortement que chez les mouches élevées sur substrat artificiel. Quand les mouches élevées pendant deux ans sur substrat artificiel (fréquences alléliques en équilibre) sont ensuite pourvues en olives mûres (noires) pendant 3 générations pour pondre, les fréquences des allozymes de l'alcool deshydrogénase ont changé nettement en une génération, restant stable ensuite. Le changement rapprochait les fréquences obtenues de celles des populations naturelles.Quand les mouches récoltés à l'extérieur étaient élevées artificiellement dans trois conditions de températures (17° constant, 17/25 et 25° constant), les modifications des fréquences étainent semblables; cependant, le changement était plus rapide aux températures constantes, surtout la plus élevée.

     

Abortion by the tsetse fly Glossina palpalis palpalis after treatment with insecticides

Batches of wild-caught adult females of Glossina palpalis palpalis R.-D. were treated topically (0.36 l per fly) with different doses of 14 chemical insecticides in acetone and subsequent abortion (if any) and death of each fly were recorded. Control flies received acetone alone. No fly was fed after treatment. Abortion rates of treated fly-batches and the corresponding control batch were compared by Fisher's exact test. The rate of abortion for 274 control flies rose from 1.1% on day 1 to 6.3% on day 5, then declined to the last abortions on day 9. The increase of rate probably resulted from increasing period of starvation. Significantly increased rates of abortion of eggs or immature larvae, compared with the control, were only found with high doses of fenitrothion, propoxur, permethrin and dieldrin and with various doses of sumithrin, sumicidin and deltamethrin. Abortion was most frequent for the last three; synthetic pyrethroids. All significant rates were for rapid abortion, within 24 h after treatment, and many abortions for sumithrin, sumicidin and deltamethrin were within 60 min Pyrethroid-treated flies frequently showed rapid and prolonged knock-down. Especially for pyrethroids, many aborted eggs or larvae were covered with white, sticky fluid. It is suggested that insecticides caused high rates of abortion by general relaxation of maternal muscles, thus opening the vaginal sphincter, smoothing the uterine wall and allowing accumulated milk gland secretions to flow into the uterus. This reduced friction between contents and the uterine wall and the egg or larva escaped passively through the vaginal aperture.

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Résumé Les femelles de G. palpalis palpalis provenaient de captures de populations sauvages près d'Abuja au Nigéria. Les lots de mouches ont reçu des applications locales (0,36 l par mouche) de 14 insecticides chimiques à différentes doses. L'émission d'un oeuf ou d'une larve immature était considérée comme un avortement. Les témoins ont reçu de l'acétone. Les mouches n'ont pas été alimentées après traitement. Les résultats des différents lots ont été comparés par le test de Fisher. Pour 274 mouches traitées à l'acétone, le taux d'avortement croît de 1,1% le ler jour à 6,3% le 5e jour pour diminuer jusqu'au taux final le 9e jour, qui n'excède pas le taux naturel de 7%. On peut penser que le taux croissant est dû à la prolongation du jeûne et que l'acétone n'est pas un abortif. Les avortements se sont produits chez les mouches qui ont reçu chacun des 14 insecticides, les taux variant avec les doses, et pour la plupart des insecticides, augmentant avecle le temps depuis le traitement. Les taux d'avortement étaient particulièrement augmentés pour les lots traités avec des doses élevées de fénitrothion. propoxur ou perméthrine, et étaient très significativement augmentés chez ceux traités avec des doses très élevées de dieldrine ou différentes doses de sumithrine, sumicidine ou deltaméthrine: tous ces taux élevés étaient enrigstrés dans le jour après le traitement.Les avortements étaient particulièrement rapides, dans les 60 minutes, pour la sumithrine, la sumicidine et la delthaméthrine. Aucune mouche traitée à l'acétone ou à l'un des 11 autres produits n'a avorté dans les 60 minutes. Beaucoup de mouches traitées aux pyréthroïdes ont présenté un effrondement rapide et prolongé, suivant la dose. Beaucoup d'oeufs et de larves avortés après traitement aux pyréthroïdes étaient couverts d'un fluide blanc et visqueux. On peut estimer que les insecticides ont provoqué l'avortement par relâchement des muscles maternels, permettant l'ouverture du vagin, le déridement de la paroi utérine et la décharge dans l'utérus des secrétions de lait accumulées dans les glandes. Ceci a réduit la friction entre les parois de l'utérus et son contenu (oeuf ou larve) qui glissait à travers l'ouverture du vagin. Il est peu vraisemblable que les avortements induits par les insecticides puissent réduire les populations pendant les traitements.

     

The biochemical genetics of permethrin resistance in the Learn-PyR strain of house fly

Permethrin resistance in the Learn-PyR strain of house fly was examined in four genetically derived substrains, each being homozygous for a different resistant autosome of the Learn-PyR strain. The resistance of these derivative strains was characterized toxicologically and biochemically. The relative levels of resistance to permethrin conferred by each autosome were 5>3>1>2. Three factors were associated with resistance: (1) increased mixed-function oxidase (MFO) activity associated with elevated levels of cytochrome P-450, cytochrome b₅, and NADPH-cytochrome c reductase (P-450 reductase) activity; (2) target-site insensitivity (kdr); and (3) decreased cuticular penetration. Permethrin resistance factors on chromosome 1 consisted of a piperonyl butoxide (PB)-suppressible mechanism correlated with increased levels of cytochromes P-450 and b₅; on chromosome 2, a PB-suppressible mechanism associated with elevated amounts of cytochrome P-450; on chromosome 3, decreased cuticular penetration, kdr, and increased amounts of P-450 reductase activity; and on chromosome 5, a largely PB-suppressible mechanism correlated with elevated levels of cytochrome P-450 and P-450 reductase activity.     

Application of quality control procedures to large scale rearing of the Mediterranean fruit fly

Quality control charting was applied to a number of criteria implemented to monitor the large scale (ca 10 million pupae per week) production of Ceratitis capitata (Wiedemann) and to assess the quality of the flies so produced. The control chart procedure was useful and indicated the development involving adult flight ability. It also illustrated the variability inherent in some parameters e.g. percent recovery of pupae from eggs, but in the absence of similar data from other rearing facilities it is not possible to state whether or not that level of virability is inherent in the process.

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Résumé Une procédure de contrôle de la qualité a été appliquée à une série de critères de l'élevage de masse (c'est-à-dire 10 millions de pupes var semaine) de C. capitata pour garantir la qualité des mouches produites. La charte de contrôle a été utile et a permis de mettre en évidence un problème concernant l'apptitude au vol des adultes. Elle a illustré la variabilité de certains paramètres, par exemple le taux de pupes obtenues à partir des oeufs, mais en l'absence de données semblables provenant d'autres élevages, il n'est pas possible de savoir quelle part du taux de variabilité est inhérente ou non à la méthode.

     

Performance of controlled-release formulations of trimedlure to attract the Mediterranean fruit fly, Ceratitis capitata

Mediterranean fruit flies (Ceratitis capitata Wied.) are detected by traps baited with the attractant, trimedlure (TML), deposited on the standard cotton dental roll dispenser. Since this dispenser is effective for only 2–4 weeks, controlled-release dispensers may extend the field life of TML-baited traps. A polymeric plug containing 70% by weight TML was highly effective for 8–12 weeks. Other formulations were less effective in the tests with released flies. A release rate of ca. 17 mg of standard TML/day or higher gave insect captures which were generally lower but statistically equivalent to those with the reference dispenser which released 61–63 mg/day. Normalized insect catches increased approximately as the square root of the release rate; the curvilinear regression equation suggested that TML release rates of ca. 52 and 15 mg/day give insect captures equal to ca. 100% and 50%, respectively, of the reference catches. The most attractive TML isomer (TML-C) was a highly effective attractant at a release rate of ca. 4 mg/day.

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Résumé C. capitata était attiré par des pièges alimentés avec de la trimedlure (TML), attractif déposé sur un distributeur commercial de coton dentaire en rouleau. Puisque ce distributeur ne fonctionne que 2 à 4 semaines, des distributeurs à libération contrôlée peuvent augmenter le temps de fonctionnement de pièges fournis en TML. Un bouchon en polymère contenant en poids 70% de TML a été très efficace pendant 8 à 12 semaines. D'autres formules ont été moins efficaces avec des mouches lâchées. Un taux de libération, de 17 mg ou plus de TML moyen par jour, capture moins, mais sans différence statistique significative, qu'un distributeur témoin qui libérait 61 à 63 mg/j. Les captures d'insectes ont augmenté à peu près comme le carré du taux de libération; l'équation de régression curviligne a conduit à penser que la libération de TML à des taux de 52 et 15 mg/j, provoque des captures égales à 100% et 50% des captures de référence. L'isomère le plus attractif (TML-C) a été un attractif très efficace au taux de libération de 4 mg/j.