Another adaptive aspect to be considered is the negative effect of resistance to insecticide, since there tend to be adaptive costs linked to such resistance. In this study, the clone C2R, resistanttotheparasitoid, also had greater LD 50 (0.29 µg a.i./mg aphid) and also greater nymphal production than the other clones, with no adaptive cost, at least in terms of fertility. The superior reproduction of clone C2R compared other treatments was observed both in the absence (control) and in the presence of selection pressure (insecticide treatments), indicating that this is an advantageous characteristic ofthe clone, which, by having the smallest mortality, had the greatest population increase, even when exposed toacetamiprid. According to Belinato & Martins (2016), in the absence of insecticides, susceptible individuals can have reproductive advantages, and therefore levels of resistance in the population tend to decrease. Studies related tothe adaptive cost associated to resistance have found contrasting results. Hollingsworth et al. (1997) observed that a line of A. gossypii resistanttothe insecticide methomyl, had greater fertility than a susceptible line. Similarly, Eggers-Schumacher (1983) reported that a resistant line of M. persicae had a reproductive advantage in relation tothesusceptible line in the absence of selection pressure. In contrast, Konno & Omoto (2006) observed that the line of A. gossypii resistanttothe insecticide carbosulfan was at a reproductive disadvantage in relation tothesusceptible line in the absence of selection pressure, similar to Stone
Secondary endosymbionts have been pointed out as causing aphids’ resistance to parasitoids and increased heat tolerance. However, symbionts can be eliminated by high temperatures, so that resistant insects become susceptibleto parasitoids. Resistance toparasitoid can generate adaptive costs, such as reduced fecundity and longevity. The objectives of this study were to assess the adaptive cost for aphid Lipaphispseudobrassicae (Davis) resistanttoparasitoidDiaeretiellarapae (McIntosh) at optimum temperature for aphid development, observe if resistance increases heat tolerance and analyze if resistance diminishes after high temperature shock. Four groups obtained from three clones (C1, C2 and C3) of L. pseudobrassicae were formed in laboratory. One ofthe clones produced two groups, one with resistant individuals (C1R) andthe other with individuals susceptible (C1S) to D. rapae. The other two groups were composed ofparasitoid-resistant clones (C2R and C3R). For each group, six Petri dishes (5cm), each containing twenty first-instar nymphs, were maintained at optimum temperature for insect development (22ºC), and six plates were submitted to high temperature shock (37ºC) for one hour. After this period, insects were maintained at 22ºC in Petri dishes (5cm) with a cabbage leaf disk over an agar layer. Aiming to verify if resistance was maintained after thermal shock, 24 nymphs from each third generation group were parasitized after thermal shock. No difference was observed in survival or fecundity ofresistantandsusceptible clones at optimum temperature for development of L. pseudobrassicae. Resistant clones showed longer generation time (T). However, net reproductive rate (Ro), longevity and reproductive period ofresistant L. pseudobrassicae were higher than those ofsusceptible individuals, even when comparing resistantandsusceptible individuals from the same clone. No difference in the intrinsic rate of increase (rm) was observed between resistantandsusceptible individuals. Survival of immatures and fecundity of all clones were reduced by thermal shock. Regardless of thermal shock, there was no parasitism in resistant clones; meanwhile, parasitism in susceptible clones was 100% without thermal shock and 95.2% after heat shock. Biological aspects and parameters in the Fertility Life Table of L. pseudobrassicae under ideal conditions for its development or after thermal shock did not show any costs or adaptive advantages to aphids resistantto D. rapae. Resistance toparasitoid was maintained even after exposure of aphids at high temperature.
The aphids Lipaphispseudobrassicae (Davis) and Myzus persicae (Sulzer) (Hemiptera: Aphididae) are important Brassicaceae pests, occurring worldwide and causing signiﬁcant damage to crops. Interspe- ciﬁc variations in the resistance to natural enemies can potentially impact the interaction among aphid populations. Here we evaluated the hypothesis of associational resistance by determining if the presence ofresistant aphids (L. pseudobrassicae) reduces the rate of parasitism by Diaeretiellarapae (McIntosh) on non-resistant aphids (M. persicae). The experiment was conducted using collard green plants infested with M. persicae and L. pseudobrassicae either resistant or susceptibleto D. rapae. The percentage of par- asitism by D. rapae was greater on L. pseudobrassicae in thesusceptible than in theresistant treatment, but parasitism rates on M. persicae did not differ between the treatments. There was no difference in average growth rate between M. persicae andsusceptible L. pseudobrassicae populations, but resistant L. pseudobrassicae had greater growth rate than M. persicae. These results suggest that over a short period of time the presence ofresistant L. pseudobrassicae does not affect the rate of parasitism by D. rapaeon M. persicae.
The aphid Lipaphispseudobrassicae (Davis) (Hemiptera: Aphididae) is an important pest of Brassicaceae plants, and in Uberlândia, Minas Gerais, this aphid has low percentages of parasitism because of its resistance totheparasitoidDiaeretiellarapae (McIntosh). It is unknown if the resistance is caused by genetic factors or by beneficial associations with microorganisms. The aim of this study was to determine whether the resistance of L. pseudobrassicae is caused by individual biotype or by association with secondary endosymbionts organisms. For the rearing, the aphid L. pseudobrassicae was retained in leaf discs positioned on 1% agar/water solution in Petri dishes (10 cm diameter). The parasitoids were multiplied in second instar nymphs of Myzus persicae (Sulzer). We identified clones resistantandsusceptibletoparasitoid, analyzed the influence of superparasitism in the resistance, the loss of resistance in the aphid’s progeny, the presence of encapsulation structures oftheparasitoid in parasitized aphids, and conducted molecular tests to compare the composition of symbionts in resistantandsusceptible clones. It was found that in susceptible clones parasitism ranged from 47 to 67% andthe parasitism in resistant clone was zero. Superparasitism did not alter the resistance; however, aphids resistant that received three ovipositions had a higher proportion of individuals with changes caused by parasitism than those who received one oviposition of D. rapae. It was verified the loss ofthe resistance in 6.7% ofthe progeny ofresistant clone. There were no structures that indicate the encapsulation of eggs or larvae ofparasitoid in resistant aphids. Molecular tests indicated no difference in the composition of symbiotic bacteria between resistantandsusceptible aphids ofthe same clone. The results indicate that the cause of L. pseudobrassicae’s resistance totheparasitoid D. rapae is due tothe presence of secondary endosymbionts.
and Holling 1984), Aphidius smithi Sharma and Subba Rao on Acyrthosiphon pisum (Harris) (Mack- auer 1983), L. fabarum on Aphis craccivora Koch (Takalloozadeh et al., 2004), A. matricariae and A. colemani on different densities of A. gossypii (Zam- ani et al., 2006) and Aphidius matricariae (Holiday) on Aphis fabae (Scopoli) (Tahriri et al., 2007). Type III functional response has previously been report- ed for D. rapaeonLipaphis erysimi (Kalt) (Pandey et al., 1984) and Schizaphis graminium (Rondani) (Dashti et al., 2010), A. colemani and Lysiphlebus testaceipes Cresson on Schizaphis graminium (Ron- dani) (Jones et al., 2003), T. indicus on A. craccivora (Singh and Sinha 1983) and T. pallidus on C. jug- landicola (Rakhshani et al., 2004). When the parasi- toids are limited for a fixed time to search for hosts, generally a decelerating (type II) functional re- sponse curve is displayed (Burnett, 1951; Griffiths, 1969; Allen and Gonzalez, 1975; van Lenteren and Bakker, 1978; Collins et al., 1981; Hertlein and Tho- rarinsson, 1987). Several factors such as host spe- cies, host densities, previous experiences and tem- perature may affect the type of functional response (Juliano and Williams, 1985; Coll and Ridgway, 1995; Runjie et al., 1996; Messina and Hanks, 1998; Wang and Ferro, 1998; De Clercq et al., 2000; Mo- haghegh et al., 2001; Moezipour et al., 2008). It may also depend onthe different geographical race oftheparasitoid species (van den Bosch et al., 1979), an important aspect ofthe Iranian population of D. rapae. Both type II and III responses in parasitoids relate to some degree of success, including estab- lishment and partial control. It must also be noted that not all functional response studies considered are comparable in terms of analysis and experimen- tal set-up. Indeed, the results of functional response experiments may be overestimating type II curves. For instance, it has been suggested that time-lim- ited experiments may force a type II curve onthe insects’ behavior (van Lenteren and Bakker, 1976; Walde and Murdoch, 1988; Ives et al., 1999).
The aphid Lipaphispseudobrassicae (Davis) has been shown low parasitism toparasitoidDiaeretiellarapae (Mc’Intosh) in Uberlândia region, probably due to secondary endosymbionts association. These symbionts can provide adaptive advantages to aphids such as increased resistance to parasitoids and heat. Moreover, symbionts can increase the production of cytochrome P450, which is the main enzyme on degradation of insecticides. Therefore, the objective of this study was to evaluate the resistance relationship of L. pseudobrassicaetotheparasitoid D. rapae with the resistance to acetaprimid insecticide. This was done in order to verify if the resistance toparasitoid can increase the resistance to insecticide. To do so, the lethal dose ofacetamipridto kill 50% ofthe individuals (LD 50 ) andthe fecundity ofthe insects submitted to insecticide application were evaluated for aphids resistantandsusceptibletoparasitoid. We used four groups of L. pseudobrassicae collected in Uberlândia, MG. The first two groups were formed, respectively, by individuals ofthe same clone (C1), resistant (C1R) andsusceptible (CIS) toparasitoid. The third group was formed by resistant individuals of a clone collected in canola (C2R) andthe fourth group was formed by individuals from a population of commercial farming of cabbage (P1). To determine the LD 50 we used 30 individuals of each aphid group, separated in three repetitions of 10 insects, which were submitted to dose-response trials with five concentration of acetaprimid insecticide ( 0 . 01 , 0 . 1 , 1 , 10 and 100 ng. i.a/aphid). Besides, a control treatment using only acetone was done. The mortality andthe number of nymphs produced 72 hours after the product application were observed andthe LD 50 was determined. There was no difference to LD 50 for individuals ofthe same clone, C1R and C1S (0,06 e 0,06 ng. ia./aphid, respectively). The clone C2R showed the highest LD 50 (0,14 ng. i.a/aphid) and P1 had the lowest (0,01 ng. i.a/aphid). Analogously, fecundity of C2R clones was the highest one while P1 had the lowest. The individuals ofthe same clone C1 did not show any difference onthe number of nymphs produced. Thus, it cannot be assumed that resistance totheparasitoid is associated with resistance tothe insecticide andthe chemical control with acetaprimid is an option for controlling L. pseudobrassicaeresistanttoparasitoid D. rapae.
Two seeds of each genotype were sown in a 300 mL polystyrene pot containing a substrate composed of sandy-clay soil, earthworm humus and vermiculite at 6:3:1 proportion. Five days after planting, thinning was carried out, leaving only one plant per pot. The most vigorous plants with similar height and canopy volume were selected to compose the experiment, being infested onthe twelfth day after sowing with five/six-day old adult insects, from a colony of aphids ofthe same age group. Then, the plants were arranged equidistantly on benches and covered with anti-aphid cages (1.0 × 1.0 × 0.50 m).
was 0.57 to 0.69, which was close to 1 male : 2 female. Production of males occurs parthenogetically (arrhenotoky). In the laboratory, parasitism reached 40% when two adult C. luridus were exposed per parasitoid. The number of Microctonus sp. adults that emerged per parasitized beetle ranged from 4.7 to 14.2. Larval- pupal viability was 31.7 to 64.8% andthe female sex ratio ranged from 0.0 to 0.37, with prevalence of males. The egg-pupal period was 12.7 days andthe pupal-adult period was 10.7 days, resulting in a mean life cycle (egg-adult) of 22.4 days for this parasitoid (25ºC, 70% R.H.). This is the first report of a new species of
ated with resistance to a variety of arthropods in wheat (Ni et al. 2001, Boyko et al. 2006, Franzen et al. 2007, Han et al. 2009), barley (Gutsche et al. 2009), and buffalo grass (Heng-Moss et al. 2004). A recent study performed by Pierson et al. (2011) was the Þrst report ontheeffectsof soybean aphid feeding on peroxidase activity in soybeans. Their results indicated that per- oxidase activity increased in the tolerant soybean KS4202, suggesting these enzymes might be involved in the tolerance response. In a subsequent study, Prochaska (2011) analyzed the transcriptional changes in infested and uninfested KS4202 and a sus- ceptible genotype to gain insight into the genes in- volved in the tolerance response and mechanisms ofthe resistance. After 15 d of aphid feeding, Þve per- oxidase genes were identiÞed as being differentially expressed between KS4202-infested and uninfested plants. The same peroxidases genes were not differ- entially expressed in thesusceptible soybean in re- sponse to aphid feeding. It was speculated that these peroxidases might be serving to detoxify the ROS accumulated and be involved in triggering signaling molecules for speciÞc plant defense pathways.
A couve, Brassica oleracea L. var. acephala, é uma hortaliça conhecida mundialmente, sendo cultivada em praticamente todo o território brasileiro (Filgueira 1982, Lara et al. 1982). Destaca-se entre as hortaliças como um dos mais importantes alimentos para a nutrição humana por ser rica em ferro, cálcio, vitamina A e ácido ascórbico (Franco 1960). Como na maioria das plantas cultivadas pelo homem, a incidência de insetos pragas na couve também é alta. Entre as pragas conhecidas, os pulgões têm grande importância, destacando-se a espécie Lipaphis erysimi (Kalt, 1843). Este pulgão tem distribuição mundial, ataca as partes terminais de talos e inflorescências de várias espécies de crucíferas, causando encarquilhamento e amarelecimento das plantas, além de atuar como vetor de mais de 10 tipos de vírus fitopatogênicos, incluindo aqueles resposáveis pelo anel negro da couve e mosaicos da couve-flor, do rabanete e do nabo (Peña-Martinez 1992).
ABSTRACT - Lysiphlebus testaceipes (Cresson) has a broad aphid host range; however the quality of these preys may interfere in its biological feature. This study aimed to evaluate the quality of three Macrosiphini, Brevicoryne brassicae (L.), Lipaphis erysimi (Kaltenbach) and Myzus persicae (Sulzer), and three Aphidini Schizaphis graminum (Rondani) Rhopalosiphum maidis (Fitch) and Aphis gossypii Glover as hosts to L. testaceipes andto determine the relation possible of host preference, of size and quality ofthe host. The tests were carried out in climatic chamber at 25 ± 1°C, RH 70 ± 10% and 12h photophase. Theparasitoid did not oviposite in B. brassicae and L. erysimi, while the other species were nutritionally suitable totheparasitoid. L. testaceipes showed preference for aphids from tribe Aphidini and these hosts presented better quality totheparasitoid when compared to Macrosiphini. Interactions among size, preference and quality between the Aphidini were found. L testaceipes showed preference (parasitism rate 76.7%) for R. maidis, the bigger host (hind tibia with 0.281 mm). This host provided bigger size (hind tibia with 0.49 mm) and higher emergence rate (95.6%) totheparasitoid when compared to A. gossypii (parasitism rate of 55.7%). Also the smaller host A. gossypii (0.266 mm) provided smaller size hind tibia (0.45 mm) and higher mortality oftheparasitoid (emergence rate 72.1%). However, the development time was shorter andthe longevity was higher in A. gossypii (6.3 and 5.4 days, respectively) when compared tothe host R. maidis (6.7 and 3.8 days, respectively), and not been related to host size.
O parasitoide L. testaceipes é um importante agente de controle biológico e comumente encontrado no Brasil, parasitando diversas espécies de pulgões (Hemiptera: Aphididae). Dentre essas espécies estão: Aphis coreopsidis (Thomas), Aphis craccivora (Koch), Aphis gossypii (Glover), Aphis nerii (Boyer de Fonscolombe), Aphis spiraecola (Patch), Myzus persicae (Sulzer), Rhopalosiphum maidis (Fitch), Rhopalosiphum padi (Linnaeus), S. graminum, Sitobion avenae (Fabricius) e Aphis (Toxoptera) citricidus (Kirkaldy) (STARÝ et al., 2007), sendo que pulgões da tribo Aphidini (gêneros Aphis, Rhopalosiphum e Schizaphis) apresentam maior qualidade hospedeira para o parasitoide quando comparada com a tribo Macrosiphini (gêneros Brevicoryne e Myzus) (SILVA et al., 2008)
In a soybean crop, Rocha et al. (2000) also failed to observe any significant effects produced by ASM onthe population of Heterodera glycines Ichinohe, but only a tendency towards a drop in the population when ASM was applied by watering into the soil at the highest concentration (0.3 g/L). It is possible that in some nematode pathosystems, additional time is required to activate resistance mechanisms. When ASM (50 µg i.a./mL) was applied to vine leaves, there was no change in the number of Meloidogyne spp. in the roots three days after inoculation, but the population had dropped three weeks after inoculation, a period compatible with plant- nematode interaction, when giant cells are induced and maintained in the host, allowing the parasites to feed and grow (Owen et al., 2002). In soybean crop it is impossible to apply the resistance inductor prior to nematode inoculation,
Soybean cultivars with syncytium degeneration occurring four to five days after infection, present a small number of males (Endo, 1965). Luedders (1987) found that resistance genes against this nematode can affect males and females differentially, as occurs with PI 88788, but does not seem to affect male development. Halbrendt et al. (1992) also did not find changes in male development in PI 209332. However, in the same study, they observed that male development is severely affected in PI 89772 and in cultivar Pickett. Those authors stated that resistance of PI 209332 affects the development of J 3 and J 4 , resistance of cultivar Pickett affects the development of J 2 and J 3 , while resistance of PI 89772 affects all developmental stages. Since H. glycines males feed only during the stages J 2 and J 3 , the genotypes with resistance affecting the end ofthe nematode cycle (J 3 and J 4 ), exert lesser influence on male development.
The aphid parasitoid Lysiphlebus testaceipes (Cresson) is an important biological control agent of Rhopalosiphum padi (Linnaeus) andthe use of silicon (Si) in plant nutrition induces resistance to aphids in wheat. The female parasitoids are attracted to chemical cues (volatiles) released by plants in the process of herbivory. However, the release of volatiles by plants can be changed also by abiotic factors, such as Si fertilization. In order to determine the compatibility of biological control with parasitoids andthe induction of resistance by Si in the control of wheat aphids, this study evaluated the influence of Si fertilization and herbivory caused by R. padi in wheat plants onthe olfactory response of L. testaceipes females. Silicon fertilization was done when the plants reached the Z07 growth stage, by applying 0.350 g silica gel (5.7% available silicon) tothe soil, corresponding to 300 kg ha -1 of Si. Leaf Si content of plants that have not received and that were fertilized with this nutrient was determined. Herbivory induction was performed when plants reached the Z13 stage by infesting them with 40 R. padi aphids from different instars, which remained onthe plant for 24 hours. After this period, aphids, as well as their exuviae, were removed from the plants. Bioassays of female attraction oftheparasitoid L. testaceipes (24-48h old, mated and without oviposition experience) were performed in a "Y" olfactometer. Wheat plants were used with the following treatments: not fertilized with Si and undamaged by R. padi, not fertilized with Si and damaged by R. padi, fertilized with Si and undamaged by R. padi, and fertilized with Si and damaged by R. padi. Wheat plants fertilized with Si had 1.7 times (0.27%) more Si in the leaves than plants without Si fertilization (0.16%). Lysiphlebus testaceipes females did not respond to non-fertilized and undamaged plants. However, the parasitoids were attracted to plants not fertilized with Si and damaged by R. padi, to plants fertilized with Si and undamaged by R. padi andto plants that received the two stimuli: Si fertilization and herbivory. When treatments that had attracted parasitoids were compared, there was no preference of L. testaceipes by none of them. Positive responses were observed for plants fertilized with Si, regardless of herbivory, suggesting that volatiles released by these plants are similar to those of plants attacked by aphids. Silicon fertilization did not affect attraction of parasitoids by plants subjected to herbivory. Thus, induction of resistance by Si fertilization may be considered compatible with the biological control of aphids by parasitoids.
To test the assumption that exposure ofthe host toparasitoid for long periods could provoke superparasitism, the aim of this work was to test the consequences onthe immature development time, productivity of parasitoids per pupa, sex ratio and rate of parasitism of Nasonia vitripennis bred in Chrysomya megacephala pupae. Each individual pupa was placed in a glass tube with one parasitoid female for 24, 48, 72 and 96 h period of exposure, under controlled laboratory conditions. Twenty replicates of each period were performed. ANOVA with a 5% significance level was applied. The 72 h exposure caused the immature development time to increase. The mean parasitoids emergence per pupa did not vary significantly with the time of exposure. There were a significantly higher number of females than males and a trend in sex ratio deviation towards the females in all ofthe treatments. An increase in the number of unviable pupae rates were observed with increased exposure time.
The primary aim of this study was to produce a global description ofthe transcriptome modifications induced by F. psychrophilum in the pronephric trout leukocytes during the early stages ofthe infection (5 days pi), when the response is well advanced but has not yet led to major pathology. Since the bacteria were injected i.m. to fish 100– 150 g while F. psychrophilum typically infects fry and fingerlings, our model likely did not mimic perfectly the natural infection but allowed to identify innate pathways of response to a general infection by F psychrophilum in resistant versus susceptible fish. Importantly, transcriptome profiles may vary between different stages of development. Our analysis identified three main sets of genes involved in innate immunity: genes encoding matrix metallo- proteases, genes of pro-inflammatory and regulatory cytokines, and genes encoding anti-bacterial effectors (figure 5). It appeared sometimes difficult to associate a unique trout gene to a given probe. When several probes (each designed from a unique TIGR contig) matched a common counterpart in mammals, they may designate either different genes duplicated in rainbow trout or different splicing isoforms ofthe same gene. C3 is a good example of this situation, since it is present as multiple copies in the rainbow trout genome , which may produce variable signals for the different C3-specific probes present in the array. In such situations, gene-specific expression level could not be easily confirmed by real time QPCR. We therefore considered that the corresponding gene set was induced as a whole, but we could not conclude about the difference of induction of individual genes between resistantandsusceptible fish.