Seasonal occurrence and relative abundance of aphids on potato plants with classical and transgenic characters of resistance to Colorado potato beetle Leptinotarsa decemlineata (Say)

The seasonal abundance and dynamics of potato-infesting aphids were studied in two seasons, on potato Solanum tuberosum L. with various types of transgenic and classical resistance to primary pests, especially the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say). The lines tested were the NewLeaf potato, a transgenic expressing the Bacillus thuringiensis CryIIIA toxin (BTT); NYL 235-4 a parental line derived from S. berthaultii (NYL) with a high density of glandular trichomes; and a transgenic line expressing oryzacystatln I (OCI), a proteinase inhibitor gene from rice; potatoes from two commercial cultivars, Superior and Kennebec, served as controls. Over the two seasons, Macrosiphum euphorbiae (Thomas) and, to a lesser extent, Myzus persicae (Sulzer) were by far the most abundant aphids observed in the experimental plots. M. persicae was observed relatively late in the season, and was most abundant on the Kennebec-OCI potato. Macrosiphum euphorbiae was more regular over seasons, and its highest densities were observed on the NYL 235-4 line. The population of M. euphorbiae showed markedly different patterns on the five lines studied, which was clearly related to potato plant phenology. Density of M. euphorbiae was observed on the NYL 235-4 line, in late July and early August.     

Aphid responses to plants with genetically manipulated phloem nutrient levels

Abstract.  Aphids ( Myzus persicae , Macrosiphum euphorbiae and Aulacorthum solani ) are reared on potato plants with phloem sucrose concentrations reduced by up to two-fold by expressing the antisense of the sucrose-H⁺ symporter ( StSUT1 ) gene. The performance of My. persicae and A. solani on the antisense plants is comparable or superior to that on the wild-type plants, but Ma. euphorbiae increases more slowly on the antisense plants than on the wild-type and fails to feed from the antisense line with the lowest phloem sucrose concentration. Electrical monitoring by electical penetration graphs reveals that Ma. euphorbiae either do not locate the sieve elements or withdraw their stylets prematurely from the sieve elements of these plants. This difference between Ma. euphorbiae and the other aphid species may reflect interspecific variation in response both to the low phloem sucrose in transgenic plants and to pleiotropic effects of the transgene on the wider physiology of the plants. All aphid species perform well on plants with phloem sucrose concentrations that, when administered via chemically-defined diets, support little or no aphid growth. These results illustrate the need for caution in extrapolating conclusions reached for diet-reared aphids to aphids on plants, and demonstrate the importance of plant-based experiments for studies of the nutritional physiology of aphids.     

温度对桃蚜和马铃薯长管蚜实验种群生命表参数的影响

【目的】桃蚜Myzus persicae (Sulzer)和马铃薯长管蚜Macrosiphum euphorbiae (Thomas)是2种主要的马铃薯害虫。本研究旨在明确温度对这两种马铃薯蚜虫生长发育、存活、繁殖及种群增长的影响。【方法】在室内测定了5个温度（10, 15, 20, 25和30℃）下桃蚜和马铃薯长管蚜的生长发育、存活和繁殖指标,并组建了4个恒温条件下（10,15,20和25℃）的实验种群生命表。【结果】在10~25℃范围内,2种蚜虫的若蚜期、世代历期、成蚜寿命和产蚜期等均随温度的升高而缩短,而30℃高温抑制了其发育、存活和繁殖。2种蚜虫的平均世代历期（T）随温度的升高而缩短,桃蚜和马铃薯长管蚜分别从10℃的30.08 d和35.35 d缩短至25℃的14.28 d和12.95 d。桃蚜的净增殖率（R₀）在15℃时最高（86.00）,其次为20℃（73.75）,再次为25℃（62.49）,最低为10℃（51.00）;马铃薯长管蚜的R0在15℃最高（58.97）,其次为10℃（51.98）,再次为20℃（48.94）,最低为25℃（12.36）。桃蚜的内禀增长率（r_m）随温度的升高而增大,从最小10℃的0.1307增大到25℃的0.2896;马铃薯长管蚜的r_m在20℃时最大（0.2182）,其次为25℃（0.1942）,再次为15℃（0.1485）,最小为10℃（0.1118）。在相同的温度下,桃蚜的发育速率、净增殖率和内禀增长率均高于马铃薯长管蚜。【结论】温度对2种马铃薯蚜虫的生长发育、存活、繁殖及种群增长有显著的影响,桃蚜在马铃薯上的种群增长能力强于马铃薯长管蚜。这一结果为马铃薯蚜虫预测模型的建立奠定了必要的基础,并解释了桃蚜在马铃薯上发生数量多于马铃薯长管蚜的原因。     

Screening for resistance against Myzus persicae and Macrosiphum euphorbiae among wild Solanum

As a consequence of selection for productive traits, the genetic diversity of Solanum tuberosum cultivars has been drastically reduced. With the goal to develop aphid-resistant potato cultivars, our objective was to quantify the resistance of 14 accessions belonging to five wild potato species ( Solanum chomatophilum , Solanum stoloniferum stoloniferum , Solanum bukasovii , Solanum marinasense and Solanum medians ) against two aphid pests, Myzus persicae and Macrosiphum euphorbiae . Aphids were reared under controlled conditions in microcages clipped on the abaxial face of mature leaves of the Solanum species. The five wild Solanum species induced more than 90% of nymph mortality in M. persicae . The mortality rate of Ma. euphorbiae was also >90% on all S. chomatophilum , S. stoloniferum and S. medians accessions and on S. bukasovii -PI 414155. When enough adult aphids emerged, that is for Ma. euphorbiae on three S. bukasovii and three S. marinasense accessions, the prereproductive period, the adult survival and fecundity were assessed. These parameters allowed us to calculate the intrinsic rate of natural increase ( r_m ), the finite rate of increase and the population doubling time (DT). The r_m and the finite rate of increase were significantly reduced, whereas the population's DT was significantly enhanced for most (five out of six) wild Solanum accessions. All accessions of S. chomatophilum , S. stoloniferum and S. medians and S. bukasovii -PI 414155 were highly resistant to both M. persicae and Ma. euphorbiae . In conclusion, S. chomatophilum -PI 310943 and -PI 310990, and S. stoloniferum -PI 195167, -PI 201855 and -PI 275248, can be amenable for potato breeding programmes.     

Effect of an alternate weed host, hairy nightshade, Solanum sarrachoides, on the biology of the two most important potato leafroll virus (Luteoviridae: Polerovirus) vectors, Myzus persicae and Macrosiphum euphorbiae (Aphididae: Homoptera)

Hairy nightshade, Solanum sarrachoides (Sendtner), is a ubiquitous weed in potato agro-ecosystems and nonagricultural lands of southeastern Idaho and the Pacific Northwest. This weed increases the complexity of the Potato leafroll virus (PLRV) (Luteoviridae: Polervirus)-potato pathosystem by serving as aphid and virus reservoir. Previous field studies showed higher densities of green peach aphid, Myzus persicae (Sulzer), and potato aphid, Macrosiphum euphorbiae (Thomas), the two most important vectors of PLRV, on S. sarrachoides compared with potato plants in the same fields. Some of the S. sarrachoides plants sampled in these surveys tested positive for PLRV. Viral infections can alter the physiology of plant hosts and aphid performance on such plants. To understand better the potential effects of S. sarrachoides on the PLRV-potato-aphid pathosystem, the life histories of M. persicae and M. euphorbiae were compared on virus-free and PLRV-infected S. sarrachoides and potato. Individual nymphs of each aphid species were held in clip cages on plants from each treatment to monitor their development, survival, and reproductive output. Nymphal survival for both aphids across plant species was higher on S. sarrachoides than on potato, and, within plant species, it was higher on PLRV-infected plants than on noninfected plants. With a few exceptions, similar patterns occurred for fecundity, reproductive periods, adult longevity, and intrinsic rate of increase. The enhanced performance of aphids on S. sarrachoides and on PLRV-infected plants could alter the vector population dynamics and thus the PLRV-disease epidemiology in fields infested with this weed.     

Wild Solanum resistance to aphids: antixenosis or antibiosis?

The type (antixenosis or antibiosis) of resistance against the aphids Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) was characterized for the wild tuber-bearing potatoes, Solanum chomatophilum Bitter and Solanum stoloniferum Schltdl. & Bouché through behavioral (olfactometry and electrical penetration graph) and physiological studies. In dual-choice assays, only S. stoloniferum exerted attraction to M. euphorbiae. This ruled out the possibility that plant volatiles of S. chomatophilum and S. stoloniferum may contribute to the high resistance expressed. In electrical penetration graph experiments, aphids feeding on S. stoloniferum showed increased salivation phases, whereas phloem ingestion was drastically reduced for both aphid species. Because reaching phloem elements was not delayed in both species, the resistance mechanism was phloem-located. The antixenosis exhibited by S. stoloniferum was similar on young and mature leaves. S. chomatophilum also showed phloem-located antixenosis against M. persicae. In contrast, M. euphorbiae had no difficulty to reach S. chomatophilum phloem tissues and to ingest sap. S. chomatophilum resistance against M. euphorbiae was antibiosis and only expressed in mature leaves, where a complete nymphal mortality was observed.     

Aphid parasitoid complex in potato in the context of IPM in Belgium

Parasitic hymenoptera of potato aphids were collected and identified in 2000 and 2001 in 11 potato fields in Belgium. Nine Aphidiidae species, parasiting seven aphid species, were found: Aphidius ervi, Aphidius matricariae, Aphidius picipes, Binodoxys angelicae, Diaeretiella rapae, Praon abjectum, Praon gallicium, Praon volucre and Toxares deltiger. A. ervi and A. picipes were the dominant and sub-dominant species, with 54% and 28% of the primary parasite collected, respectively. Both species and T. deltiger were found on Aphis nasturti, Aulacorthum solani, Macrosiphum euphorbiae and Myzus persicae, the four most important aphid potato in Belgium. Parasitism rate of A. nasturtii and, to a lesser extent, M. euphorbiae was low compared to A. solani and M. persicae. Parasitism of A. solani was particularly high, with 63.5% in 2000 and 89.2% in 2001, and this species was the preferred host of several Aphidiid species. The abundance of alternative hosts as other crops pest aphids or non-pest aphids on wild plants in agroecosystems could explains the efficacy of these species. The biological control of A. nasturtii and M. euphorbiae by parasitic hymenoptera was poorer, and several studies need to be undertaken to find suitable parasitic hymenoptera species effective on these aphids and agro-environmental measures able to promote them.     

Transgenic potatoes with enhanced levels of nematode resistance do not have altered susceptibility to nontarget aphids

Cysteine proteinase inhibitors (cystatins) confer resistance to plant-parasitic nematodes when expressed in transgenic plants. The survival and growth of nymphs of the peach-potato aphid, Myzus persicae, were adversely affected when cystatins were added to artificial diets. When aphids were clip-caged onto transgenic plants expressing chicken egg white cystatin (CEWc) there was no adverse effect on aphid fitness. Field populations of aphids on transgenic Desiree potatoes, expressing CEWc or a modified version of oryzacystatin I, were not significantly different from populations on control Desiree plants. The effect of other nematode management options on aphid numbers was also studied. A conventionally bred cultivar, with partial nematode resistance, supported higher populations of aphids than the transgenic lines at the beginning of the sampling period. Peak aphid densities on the untreated control and untreated transgenic lines were 7 and 5.2 aphids per plant. Aldicarb, commonly used to control nematodes on potatoes, reduced the value to less than 0.2 aphids per plant. The results demonstrate that levels of expression in the plant tissue actually consumed are important in determining the risk of cystatins to nontarget invertebrates. The study also highlights the importance of including currently used management options in any assessment of the impact of transgenic plants on nontarget organisms.     

Effect of mixed viral infections (potato virus Y-potato leafroll virus) on biology and preference of vectors Myzus persicae and Macrosiphum euphorbiae (Hemiptera: Aphididae)

Mixed viral infections of heterologous viruses such as Potato virus Y (family Potyviridae, genus Potyvirus, PVY) and Potato leafroll virus (family Luteoviridae, genus Polerovirus, PLRV) are a regular occurrence in Idaho's potato, Solanum tuberosum (L.), cropping systems. An increased number of plant samples from Idaho's potato fields over the past 2 yr has serologically tested positive for both PVY and PLRV via double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and exhibited more severe symptoms than singly-infected plants (PVY or PLRV). Several studies have extensively examined the mixed infection phenomenon but to the best of our knowledge, none have examined the effect of such infections on vector biology and preference. Laboratory studies were conducted to examine the effect of mixed viral (PVY-PLRV) infection on the fecundity and preference of two of the most efficient PVY and PLRV vectors, the green peach aphid, Myzus persicae (Sulzer), and the potato aphid, Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae). M. persicae and M. euphorbiae adults were clip-caged (one adult per cage) to leaflets of PVY, PLRV, PVY-PLRV-infected, and noninfected potato plants. The number of nymphs produced in all four treatments was recorded after 96 h. M. persicae and M. euphorbiae fecundity was significantly higher on mixed infected plants than on singly infected plants or noninfected plants. Preference of alatae and apterae of M. persicae and M. euphorbiae was determined with the use of settling bioassays. Both alatae and apterae of M. persicae and M. euphorbiae preferentially settled on PVY-PLRV-infected plants than on singly infected plants (PVY or PLRV) or noninfected plants.     

Detection of the luteoviruses, beet mild yellowing virus and beet western yellows virus, in aphids caught in sugar-beet and oilseed rape crops, 1990–1993

The incidence of beet mild yellowing luteovirus (BMYV) and non-beet-infecting strains of beet western yellows luteovirus (BWYV) in individual winged aphids, caught in yellow water-traps, in sugar beet during the spring and early summer, and in oilseed rape plots in the autumn, was monitored using monoclonal antibodies in ELISA tests from 1990 to 1993. Between 0% and 8% of the Myzus persicae trapped in sugar beet each year carried BMYV, whereas 0% to 4% caught in oilseed rape in the autumn contained this virus. In 1990, 6.5% of Macrosiphum euphorbiae trapped in sugar beet contained BMYV, but in subsequent years less than 1% were carrying virus. Much higher proportions (26–67%) of the M. persicae tested from sugar beet contained BWYV, and similar proportions tested from oilseed rape (24–45%) also carried this virus in the autumn. In contrast only 3–19% of the M. euphorbiae caught in sugar beet contained BWYV, and none in oilseed rape. In 1991 and 1992 large numbers of Breuicoryne brassicae were caught in the plot of oilseed rape, of which over 50% contained BWYV; none were carrying BMYV. In transmission studies between 1990 and 1992, 1% and 27% of M. persicae transmitted BMYV and BWYV respectively to indicator plants; subsequent ELISA tests on the same aphids showed that 3% and 33% respectively contained the two viruses. One percent of M. euphorbiae transmitted BMYV, but none were found to contain BMYV using ELISA; 15% transmitted BWYV whilst only 5% were found to carry the virus. In 1992 and 1993 the incidence of BMYV-infection in the sugar-beet fields in which aphids had been trapped ranged from 1.2%, in a field which had received granular pesticide (aldicarb) at drilling plus three foliar aphicidal sprays, to 39.5% in a field which had received only one foliar spray. In 1992 in a sugar-beet crop which had received no aphicidal treatments, and where 2.8% of immigrant M. persicae and 2.5% of M. euphorbiae contained BMYV, 11.6% of plants developed BMYV infection. Lowest levels of infection were associated with the use of granular pesticides at drilling. In 1990, 80% of oilseed rape plants in a field plot were infested with a mean of seven wingless M. persicae per plant by mid-December; 37% of these plants were infected with BWYV. The studies show that M. persicae is the principal vector of BWYV, and large proportions of winged M. persicae carry the virus, in contrast to BMYV, which is consistent with the common occurrence of BWYV in brassica crops such as oilseed rape.     

Effects of plant protease inhibitors, oryzacystatin I and soybean Bowman-Birk inhibitor, on the aphid Macrosiphum euphorbiae (Homoptera, Aphididae) and its parasitoid Aphelinus abdominalis (Hymenoptera, Aphelinidae)

Transgenic plants expressing protease inhibitors (PIs) have emerged in recent years as an alternative strategy for pest control. Beneficial insects such as parasitoids may therefore be exposed to these entomotoxins either via the host or by direct exposure to the plant itself. With the objective of assessing the effects of PIs towards aphid parasitoids, bioassays using soybean Bowman-Birk inhibitor (SbBBI) or oryzacystatin I (OCI) on artificial diet were performed on Macrosiphum euphorbiae-Aphelinus abdominalis system. OCI significantly reduced nymphal survival of the potato aphid M. euphorbiae and prevented aphids from reproducing. This negative effect was much more pronounced than with other aphid species. On the contrary, SbBBI did not affect nymphal viability but significantly altered adult demographic parameters. Enzymatic inhibition assays showed that digestive proteolytic activity of larvae and adults of Aphelinus abdominalis predominantly relies on serine proteases and especially on chymotrypsin-like activity. Immunoassays suggested that OCI bound to aphid proteins and accumulated in aphid tissues, whereas SbBBI remained unbound in the gut. Bioassays using M. euphorbiae reared on artificial diets supplemented with both OCI and SbBBI showed a fitness impairment of Aphelinus abdominalis that developed on intoxicated aphids. However, only SbBBI was detected in parasitoid larvae, while no PI could be detected in adult parasitoids that emerged from PI-intoxicated aphids. The potential impact of PI-expressing plants on aphid parasitoids and their combined efficiency for aphid control are discussed.     

Pathogenicity of hyphomycet fungi to aphids Aphis gossypii Glover and Myzus persicae (Sulzer) (Hemiptera: Aphididae)

The aphids Aphis gossypii and Myzus persicae are cosmopolitan, poliphagous and damage cultivated plants. The effects of the entomopathogenic fungi Beauveria bassiana (isolate IBCB 66), Metarhizium anisopliae (isolate IBCB 121), Paecilomyces fumosoroseus (isolate IBCB 141) and Lecanicillium (= Verticillium) lecanii (isolate JAB 02) on third instar nymphs of A. gossypii and M. persicae were evaluated in the laboratory at 25 degrees C, 70 +/- 10% RH and 12h photophase. The aphids were transferred to petri dishes with a foliar disk (cotton or pepper) with a layer of 1 cm tick of agar-water. The fungi were applied in a suspension containing 1.0 x 106 to 1.0 x 108 conidia/ml. In the control treatment 1 ml of sterilized water was added to the foliar disks. The mortality of aphids was evaluated daily. B. bassiana and M. anisopliae caused 100% mortality at the seventh day after inoculation, for both species. L. lecanii was the fungus that provided mortality later in the aphids and M. persicae was more susceptible to both fungi than A. gossypii.     

Direct and indirect sublethal effects of Galanthus nivalis agglutinin (GNA) on the development of a potato-aphid parasitoid, Aphelinus abdominalis (Hymenoptera: Aphelinidae)

Snowdrop lectin (Galanthus nivalis agglutinin, GNA), has been shown to confer partial resistance to two potato aphids Myzus persicae and Aulacorthum solani, when incorporated in artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess the potential effect of GNA on the aphid parasitoid Aphelinus abdominalis. GNA (0.1% w/v) was successfully delivered to Macrosiphum euphorbiae via artificial diet and induced a reduced growth rate and increased mortality compared to aphids fed a control diet. As aphid parasitoid larvae are endophagous, they may be exposed to GNA during their larval development and potential "chronic toxicity" on A. abdominalis was investigated. The amounts of GNA present in aphid and parasitoid tissues were estimated by western blotting. Results suggest that parasitoids excrete most of the GNA ingested. Sublethal effects of GNA on several parasitoid fitness parameters (parasitism success, parasitoid development and size, emergence success, progeny survival and sex ratio) were studied. No direct detrimental effect of GNA on A. abdominalis was observed. However, GNA had an indirect host-size-mediated effect on the sex ratio and the size of parasitoids developing in GNA-fed aphids. This work highlights the need to determine the exact "causes and effects" when assessing the ecological impact of transgenic plants on non-target beneficial insects. Such bioassays form the basis of a tiered risk assessment moving from laboratory studies assessing individuals towards field-scale experiments assessing populations.     

Effects of kaolin particle film on Myzus persicae (Hemiptera: Aphididae) behaviour and performance

The emergence of resistance mechanisms to, and revocation of, many insecticides used in the control of the polyphagus aphid pest, Myzus persicae (Sulzer), has increased the pressure to develop novel approaches for the control of the pest in many crops. Kaolin-based particle films provide a physical barrier against insect pests and show considerable potential for controlling M. persicae. We conducted a series of laboratory experiments to investigate the mode of action of kaolin against aphids. The material appeared to have no direct effect on M. persicae; spraying adult aphids with aqueous kaolin suspension had no significant impact on their subsequent survival or reproduction on untreated plants. Similarly, when aphids were placed on kaolin-treated host-plants (Brassica oleracea), their performance (survival, growth rate and reproduction) was not significantly different from aphids on untreated plants. However, when M. persicae were given a choice between kaolin-treated and untreated (or water solvent-treated) leaf areas, both adults and nymphs exhibited a significant preference for non-kaolin-treated host-plant material. Rejection of kaolin-treated plant material occurred very rapidly (within 20 min) and this behavioural effect may be related to the efficacy of kaolin in controlling aphids under field conditions.     

FACTORS AFFECTING THE SPREAD OF APHID-BORNE VIRUSES IN POTATO IN EASTERN SCOTLAND: I. OVERWINTERING OF POTATO APHIDS, PARTICULARLY MYZUS PERSICAE (SULZER)

Three species of potato aphids, Myzus persicae (Sulzer), Macrosiphum euphorbiae (Thomas) and Aulacorthum solani (Kltb.), overwinter in eastern Scotland, primarily as apterae on perennial, glasshouse, frame and brassica crops. Brassica crops are the commonest hosts of overwintering Myzus persicae , the principal vector of potato leaf roll and Y viruses, and these crops are concentrated in the market-gardening areas of the Lothians and Moray. Although crops of savoy cabbage and brussels sprout often carried numerous M.persicae during the winter, spring cabbage, cabbage for seed and broccoli seem the most important overwintering hosts because they usually persist until mid-May, long enough to allow the development and dispersal of alatae to spring-planted crops. Many alatae dispersed during July and August from crops colonized in spring. Although M. persicae overwintered as eggs on peach and viviparously on plants in glasshouses, the influence of such sites, which are generally distributed throughout the main seed-potato growing areas of Angus, Perth and Fife, was local and unless numerous M. persicae survive the winter on weeds, the market-garden area of the Lothians is probably the most important source from which this aphid disperses in spring and early summer to colonize potato crops in eastern Scotland.     

Probiotic effects of beta-glucuronidase on the peach-potato aphid Myzus persicae (Aphididae)

beta-glucuronidase (GUS) is a reporter protein commonly expressed in transgenic plants allowing the visualization of the transformed individuals. In our recent work, we showed that consumption of transformed potato plants expressing this GUS enzyme improves performance of the phloem feeding aphid Myzus persicae. Those results led us to the conclusion that the expression of GUS in potato plants might be responsible for the probiotic effect measured in feeding aphids. In the present paper, artificial diets were used to provide active GUS (10 and 500 microg ml(-1)), inactivated heated GUS (500 microg ml(-1)), glucuronic acid (10, 100 and 500 microg ml(-1)), and bovine serum albumin (500 microg ml(-1)) to M. persicae. Our results reveal that these chemicals provided as food intake might influence the biological parameters of this aphid. Experiments showed a probiotic effect of 500 microg ml(-1) GUS diet, resulting in reduced larval mortality, and increased adult reproduction period and fecundity, which led to an increased population growth potential (r(m)=0.17+/-0.01 versus r(m)=0.12+/-0.03 for aphids fed on control diet). A lower amount of added GUS led to fewer variations, biological parameters being only slightly altered (r(m)=0.14+/-0.03). Statistically similar alterations of the biological parameters were obtained when comparing aphids fed on the diet added with inactivated GUS or the non-structural bovine serum albumin protein (r(m)=0.15+/-0.02 and 0.14+/-0.03, respectively). Feeding assays conducted with glucuronic acid supplemented diets enhanced longevity and nymph production of the adult aphids and reduced larval mortality, resulting in r(m)=0.15+/-0.02 for the highest dose (500 microg ml(-1)). Although 100 microg ml(-1) glucuronate diet did not induce any effect on M. persicae (r(m)=0.12+/-0.03), aphids fed on 10 microg ml(-1) glucuronate diet exhibited unexpected reduced demographic parameters (r(m)=0.10+/-0.03). Immuno-histological analysis showed GUS labeling along the whole digestive epithelium of adults and in various tissues including embryos and bacteriocytes. These results suggest that GUS crosses through the digestive tract. Western blots performed with protein extracts of transformed potato plants expressing the gus gene showed a unique band of molecular weight 76 kDa. On the contrary, in extracts from aphids fed on transgenic potato plants or bred on GUS 500 microg ml(-1) artificial diet, several proteins of lower molecular weight were hybridized, revealing proteolysis of ingested GUS. It is concluded that GUS protein, and more precisely GUS activity, is responsible for the probiotic effects on aphid feeding. The possible pathways of induction of such physiological alterations by GUS are discussed.     

Distribution of Aphids (Hemiptera: Aphididae) in Potato Growing Areas of Southwestern Australia

Sticky traps, water traps and leaf samples were used to monitor aphid populations at 32 sites in southwestern Australia between October and May for four seasons between 1988–92. Twenty-seven sites were located in potato, Solanum tuberosum L., crops, with five others located in mixed vegetable crops or pastures. Sites were located in an area of approximately 90,000 km², and encompassed most of the potato growing areas of the region. Thirty-four species of aphids were detected. Potato-colonising aphids found were Myzus persicae, Aulacorthum solani, Macrosiphum euphorbiae and Aphis craccivora. M. persicae was the most widespread, and its seasonal distribution in southwestern Australia is presented. Fewer M. persicae were recorded and it arrived later in the season for 2 of 3 years at southern sites than northern sites. At sites where both sticky traps and leaf sampling were used, leaf sampling often detected M. persicae before they were found on traps. Results suggest that potato crops grown on the southern coast will be least vulnerable to infection by aphid-borne viruses.     

Azadirachta indica metabolites interfere with the host-endosymbiont relationship and inhibit the transmission of potato leafroll virus by Myzus persicae

The effects of neem (Azadirachta indica A. Juss) seed kernel extracts (NSKE) and azadirachtin on the ability of Myzus persicae (Sulz.) to transmit potato leafroll luteovirus (PLRV) was studied. Moreover, it was investigated whether treatments with these compounds would exert an effect on larval growth and mortality, and on the aphid intracellular symbionts. Endosymbiotic bacteria play an essential role in the performance of aphids, and in luteovirus transmission by aphids. NSKE and azadirachtin were offered to one-day-old M. persicae nymphs via a membrane feeding system. The neem metabolites displayed a 100% mortality at doses higher than 2560 ppm. At intermediate doses, ranging between 320 and 2560 ppm, larval growth and mortality were affected in a dose-dependent manner. The transmission of PLRV by M. persicae was inhibited by 55–90%. The endosymbiont population of the aphid was clearly affected by a treatment with neem metabolites as the release of their most abundant protein, Buchnera GroEL, into the haemocoel of the aphid was inhibited. Moreover, morphological aberrations on the bacterial endosymbionts were observed in aphids which fed on 2560 ppm of azadirachtin. At doses lower than 160 ppm of NSKE or azadirachtin, the endosymbiont population of M. persicae, and mortality, growth and feeding behaviour were similar to that of the untreated groups of aphids. However, PLRV transmission was still inhibited by 40–70%. The possible targets of the neem metabolites in the aphid are discussed.     

多种植物提取物对桃蚜和萝卜蚜的拒食活性研究

采用改进的蜜露色斑法 ,测试 34种植物乙醇提取物 (0 0 1g干重·mL-1,0 0 1gDW·mL-1)和几种天然源药剂对桃蚜Myzuspersicae(Sulzer)和萝卜蚜Lipaphiserysimi(Kaltenbach)取食的影响。结果表明 ,白蝴蝶Syngonium podophyllumSchott.、苍耳XanthiumsibiricumPrtr.etWidd、白花非洲山毛豆Tephrosiavo gelliHook .的提取物对两种蚜虫的活性均较高 ,2 4h对桃蚜的拒食率分别达 0 6 82、0 6 2 9和 0 80 6 ,对萝卜蚜的拒食率分别为 0 4 0 5、0 370和 0 383,与对照之间差异极显著 ;油茶Camelliaoleifera和花椒Zanthoxylumschinifolium的提取物拒食作用亦较强 ,2 4h对桃蚜的拒食率分别为 0 5 5 2和 0 5 14 ,对萝卜蚜的拒食率分别为 0 5 70和 0 5 18。三种药剂 (0 3%印楝素乳油、鱼藤酮精、机油乳剂 )在所测试的浓度对两种蚜虫的拒食率均达 0 719以上 ,拒食效果显著。     

低浓度SO2污染与桃蚜的生长和繁殖

用40或80ppbSO₂熏气处理过的油菜饲养桃蚜(Myzus persicae),研究低浓度SO₂污染对这种蚜虫的影响。与对照组相比,两个处理组若蚜的发育速率显著加快,5天内的平均相对生长速率(MRGR)分别增加22.3%和31.5%。成蚜的繁殖力提高40—90%,导致桃蚜种群的内禀增长率(r_m)分别升高17%和27%。比较了桃蚜和其它3种蚜虫对SO₂污染的反应强度,讨论了SO₂污染促进某些植食性昆虫生长的可能原因。