Oviposition choice and larval survival of Dasineura marginemtorquens (Diptera: Cecidomyiidae) on resistant and susceptible Salix viminalis

Abstract.

• 1 Substantial intraspecific variation exists in Salix viminalis resistance to the gall midge Dasineura marginemtorquens. Earlier work has found this variation to have a large genetic component. Willow clones are stable in their resistances between midge generations and different nutrient levels in both field and laboratory culture.
• 2 This study reports the results of laboratory experiments on female oviposition choice and larval survival on potted plants from clones that are very different in resistance as determined in field studies.
• 3 In choice experiments using pairs of plants, the average female midge did not prefer susceptible willow clones over resistant ones for oviposition. In about one third of the replicates, midges actually laid more eggs on the resistant clone. Further work is necessary to examine the nature of variation among midges in discrimination of these plant types.
• 4 Resistance is manifested as great differences in larval survival. Six days after oviposition survival was 92% on susceptible plants but only 6% on resistant ones. Galls developed on all of the susceptible plants, while in 73% of the resistant plants galls were not even initiated.
• 5 The plant traits causing resistance are enigmatic. Larval behaviour suggests that resistant plants interfere with feeding behaviour. On resistant plants, most larvae wander for more than 24 h without initiating any galls before dying. On susceptible plants many first instar larvae begin feeding and initiate galls within this period.

     

Selection ofAzolla forms resistant to the water lily aphid,Rhopalosiphum nymphaeae Life history of Rhopalosiphum nymphaeae

Genotypic and environmentally determined differences inSalix viminalis L. suitability forDasineura marginemtorquens (Bremi) (Diptera: Cecidomyiidae) growth and survival were investigated in laboratory and field experiments. Earlier studies have documented high neonate larval mortality on certainS. viminalis genotypes. Here we present results from laboratory experiments which show no difference in larval establishment behaviour on resistant and susceptible willow genotypes. These data indicate that larvae are not able to detect the plant characteristic responsible for resistance. In a field study insect performance was measured on willow shoots of dissmilar size. Adult body size was positively correlated to willow shoot length. In turn, body size was positively correlated to potential fecundity. These results are discussed in relation to observed high densities ofD. marginemtorquens in vigorously growing willows cultivated for biomass production.     

Molecular Species of Free Ceramides in Aspergillus oryzae

Free ceramides isolated from A. oryzae were fractionationed into three groups by thin-layer chromatography on silica gel G according to degree of hydroxylation of the molecules. Each group was converted to trimethylsilyl ether derivatives, which were analyzed by gas-liquid chromatography-mass spectrometry for the structure of the molecular species. As a result, the representative molecular species of ceramides were characterized as N-lignoceroyl-phytosphingosine (1%), N-2-hydroxylignoceroyl-phytosphingosine (31%) and N-2,3-dihydroxylignoceroyl-phytosphingosine (31%).     

Evidence for a female sex pheromone in the brassica pod midge Dasineura brassicae

ABSTRACT. The responses of Dasineura brassicae Winn. (Diptera, Cecidomyiidae) to odours from both male and female midges and from their host ( Brassica napus ) and non-host ( Vicia faba ) plants were studied using a Y-tube olfactometer. Female but not male D. brassicae are attracted to crushed B. napus leaves but not to those of V. faba. Males are attracted to live virgin females, to crushed virgin and mated females and to hexane washes of females, suggesting that the female produces a sex pheromone that attracts males. Males were also attracted to hexane washes of female ovipositors, but not to washes of the bodies of females without ovipositors, suggesting that the ovipositor is the site of pheromone release or production. Males were not attracted to live mated females or to other live or crushed males and mated females were not attracted to other mated females.     

In vitro culture of ovaries of a viviparous gall midge

Summary Ovaries of the viviparous pedogenetic gall midgeHeteropeza pygmaea can be cultured in hemolymph obtained from X-ray-sterilized larvae of the same species. In this culture medium, formation of follicles is essentially the same as in vivo, and sometimes female larvae develop from these follicles. The ovaries of such larvae, in their turn, have been cultured in vitro to produce larvae. In this way, in vitro development from oogonium to larva has been maintained for several generations. When using hemolymph obtained from larvae grown under different conditions, the in vitro cultured ovaries produce a second type of egg which probably is male-determined. Ovarian development in vitro has been studied with differential interference contrast optics and time-lapse cinemicrography. This work was supported by the Swiss National Science Foundation Grant No. 3.2010.73.     

Components of resistance to the sorghum midge, Contarinia sorghicola

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible cultivars (CSH 1 and Swarna). Data were recorded on the numbers of eggs, larvae, emerged adults and grain damage in panicles of different genotypes infested with 60 midge females/panicle under no-choice conditions. The size of floral parts (glume, lemma, palea, lodicule, stigma, style, ovary and anther), rate of grain development and tannin content of grain were measured. The lengths of glume gl and 82, lemma L1 and L2, palea, lodicule, anther, style and stigma were positively associated with susceptibility to sorghum midge. Rate of grain development (between 3rd and 7th day after anthesis) was negatively associated with susceptibility to sorghum. Tannin content of grain was also negatively correlated with midge susceptibility, although there were distinct exceptions (e.g. DJ 6514 is highly resistant bur has a low tannin content).     

Antixenosis component of resistance to sorghum midge, Contarinia sorghicola Coq. in Sorghum bicolor (L.) Moench

Sorghum midge, Contarinia sorghicola Coq. (Diptera: Cecidomyiidae) is the most destructive pest of grain sorghum, and host-plant resistance is an effective method of controlling this insect. We studied the antixenosis component of resistance to sorghum midge using multi-, double- and no-choice cage tests, and under multi-choice field conditions to quantify and understand the nature of antixenosis component of resistance to this insect in Sorghum bicolor (L.) Moench. Midge response towards sorghum panicles was influenced by panicle size and cage type used to study the orientation behaviour. Maximum number of midges were recorded at 30 and 60 min after initiating the experiment. Antixenosis shown by C. sorghicola under multi-choice field conditions to ICSV 197 and TAM 2566 was not confirmed under cage tests, while DJ 6514, AF 28 and IS 3461 were non-preferred both under field and cage conditions. Midge-resistant female parents (PM 7061 and PM 7068) were less preferred than the midge susceptible (ICSA 42 and 296A) female parents. Male-sterility did not influence host finding and acceptance by the midge females, although in one out of two tests, the maintainer lines (B-lines) were preferred over the male-sterile lines (A-lines).     

水稻对稻瘿蚊为害补偿力与经济阈值研究

１９９４－１９９８年针对水地稻瘿蚊为害补偿力及经济阈值进行了研究,结果表明：⑴水稻对稻瘿蚊为害具有较强的补偿能力,但基本属于不足补偿,不同标葱梯度其补偿力不同,每造成１％的标葱引起的产量损失远小于１％,其补偿率一般在５５％－８０％之间,产量损失及其损失率与标葱数呈极显正相关,有效穗和产量补偿率与标葱数则呈显负相关;⑵在相同受害程度下,密植损失大,补偿力小,而稀植损失小,补偿能力大,秧苗期补偿效     

水稻资源GXM-001-2对稻瘿蚊的抗性鉴定与遗传分析

稻瘿蚊对南方水稻的危害日趋严重,育种上急需新的抗源。利用广西地方品种GXM-001-2作父本,分别与感虫品种TN1和已知抗性基因载体品系W1236(Gm1)、IET2911(Gm2)、BG404-1(gm3)、OB677(Gm4)、ARC5984(Gm5)、多抗1号(Gm6)杂交、自交和回交,获得F1、F2、BC1F1群体,对亲本和各杂交后代进行稻瘿蚊的抗性评价及遗传分析。结果表明,抗源GXM-001-2高抗稻瘿蚊中国Ⅱ型,抗中国Ⅳ型,且抗性均由1对显性基因控制;等位性测定表明抗源中的抗性基因与已知抗性基因Gm1、Gm2、gm3、Gm4、Gm5、Gm6不等位,推测该基因可能是1个新的抗稻瘿蚊基因。     

The biology of Dasineura dielsi Rübsaamen (Diptera: Cecidomyiidae) in relation to the biological control of Acacia cyclops (Mimosaceae) in South Africa

Abstract  Acacia cyclops is an invasive Australian tree in South Africa and a target for biological control using seed-reducing agents. In southern Australia, two gall-forming Cecidomyiidae, Dasineura dielsi (Small Fluted Galler) and Asphondylia sp., develop on the flowers and seeds of A. cyclops , respectively. The larvae of D. dielsi form woody fluted galls on the ovaries of flowers and prevent the development of fruit. Immature Asphondylia sp. develop in the loculi of green fruit and destroy developing seeds. Dasineura dielsi was selected as a biological control candidate for A. cyclops in South Africa and was approved for official release after host specificity evaluation and consideration of potential conflicts of interest. Dasineura dielsi naturalised in South Africa in 2001 and after 3 years dispersed up to 450 km from a single population at Stellenbosch, Western Cape. At sites where D. dielsi has been present longest, high gall densities occur on A. cyclops during the peak flower season in summer. Four hymenopterans, ? Synopeas sp., Mesopolobus sp., Torymus sp. and an unidentified Platygastridae, were reared from D. dielsi galls and are suspected parasitoids of the cecidomyiid, with incidence levels less than 10%. Monitoring is required to evaluate trends in the population status of D. dielsi , its parasitoids and seed production of A. cyclops . Importantly, field monitoring should determine the extent and nature of possible competitive interactions between D. dielsi and an introduced seed-feeding weevil, Melanterius servulus .