首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   36篇
  免费   1篇
  2016年   1篇
  2013年   2篇
  2010年   2篇
  2009年   2篇
  2008年   1篇
  2006年   1篇
  2005年   4篇
  2004年   1篇
  2003年   1篇
  2002年   2篇
  2001年   2篇
  1998年   2篇
  1997年   2篇
  1996年   3篇
  1995年   3篇
  1994年   2篇
  1992年   2篇
  1990年   1篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
To test the hypothesis that early maturation of barley affords it some resistance to cereal aphids, the colonisation, survival, growth, reproduction and emigration of M. dirhodum on barley was measured and compared with previously published results for this aphid on wheat.
Barley plants were colonised as readily as wheat plants. Survival to maturity was similar on both hosts. Relative growth rate was higher on wheat than on barley for most of the season while reproduction was similar on both. Emigration, measured alate production, was significantly higher on mature wheat than on mature barley.
It is proposed that the increase of M. dirhodum populations on barley is normally terminated early in the year directly plant maturation and consequent drying out of the leaves, resulting in the death of aphids. This is different to the situation on wheat, which matures later, and where emigration following plant induced alate induction has been shown to be the major factor affecting the decline in population growth.
These results support the hypothesis that early maturation of barley provides some resistance to M. dirhodum.  相似文献   
2.
Under solid-state and liquid-state cultivations, the entomopathogenic fungus Verticillium lecanii F091 produced different types of spores. The aerial spores (AS) on cooked rice formed clusters on the tips of conidiophores, while the submerged spores (SS) were dispersed in the medium. The aerial spore appeared relatively uniform in size, which was 6.1 ± 0.9 m long, and 2.2 ± 0.3 m wide. The submerged spore varied in shape and size, with a mean length of 5.0 ± 1.0 m and width of 1.9 ± 0.5 m. Under scanning electron microscopy, the AS had a tendency to have rough, brittle surface characteristics; however, the SS appeared smooth on the surface. These spores were compared in two different germination media. On SMAY (Sabouraud maltose, agar, yeast extract, and neopeptone) coated coverslips, the AS did not show germ tubes until 8 h of incubation; while the SS showed many germ tubes. However, over 90% spore germination ratio was reached for both types of spores at 18-h of incubation. In the liquid medium, the SS germinated rapidly and many spores even produced spores on the spores; while the AS germinated, grew, and branched in the submerged culture gradually, and some sporulated on the tips of the short branches, or on the mycelia until 18 h of incubation. Evidently, the germination, growth patterns of aerial or submerged spores differed greatly under the different culture conditions. The virulence of the pathogen in relation to the type of spore of V. lecanii is discussed.  相似文献   
3.
Neotyphodium (Clavicipitaceae: Balansieae) fungal endophyte infection does not always confer temperate grass resistance to insect herbivores, although reports indicate that over 40 species are adversely affected by its infection. Laboratory and glasshouse experiments were conducted to improve our knowledge of the anti‐insect properties of Neotyphodium‐infected (E+) non‐commercial grasses, and E+ wild barley (Hordeum) specifically. Neotyphodium infection of four plant inventory (PI) lines of wild barley conferred resistance to Mayetiola destructor (Say) (Diptera: Cecidomyiidae), whereas none of the E+ wild barley accessions reduced the survival of Rhopalosiphum padi (L.) (Homoptera: Aphididae). Metopolophium dirhodum (Walker) (Homoptera: Aphididae) densities were significantly lower on the E+ clones of Hordeum brevisubulatum ssp. violaceum (Boissier and Hohenacker) (PI 440420), compared with densities on endophyte‐free (E–) plants of this species in population growth experiments. Neotyphodium infection of three Hordeum bogdanii (Wilensky) PI lines did not confer resistance to M. dirhodum; however, one of these E+ lines (PI 314696) was resistant to this aphid in a second population growth experiment. Our results provide additional evidence that the outcome of a grass–endophyte–insect interaction is influenced by the host grass species or genotype, Neotyphodium species or genotype, and the insect species involved. They also reinforce this phenomenon for non‐commercial grass–endophyte–insect interactions and underscore the potential role of endophytes in mediating wild barley–insect interactions and their potential to act as defensive mutualists.  相似文献   
4.
Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) is one of the three most important cereal aphid species in Germany and central European countries. High temperature is known to play a detrimental role in the reproduction and survival of aphids. Detailed experiments were conducted to assess the effects of high temperatures (27, 29, 31, and 33 °C), exposure pattern (8 h day?1 for 1, 2, 4, and 6 days), and exposure development stage (2nd, 3rd, 4th instar larvae, and adult) on the reproduction and longevity of M. dirhodum. All three factors have a significant influence on the aphids. Increasing the temperature to over 29 °C significantly decreases their lifetime fecundity and longevity. Mature aphids are more sensitive to high temperatures than younger ones. A high temperature pulse to treat aphids older than 3rd instar larvae greatly shortened their longevity and lessened their lifetime fecundity. Lifetime fecundity and longevity was found to be inversely related to exposure pattern. A high temperature pulse lasting longer than 1 week greatly reduced the lifetime fecundity and longevity. The limitation of the data collected from experiments at constant temperatures for aphid forecasting is discussed.  相似文献   
5.
During the years 1989–1992 cereal aphids were caught alive in a low level (1.5 m high) suction trap operated in Le Rheu (Brittany, France) and tested for BYDV transmission. In most cases comparisons with data collected simultaneously by a 12.2 m suction trap operating in the same site resulted in good relationships between weekly catches at both heights. Results from transmission tests showed that: (i) the two main BYDV vectors were Rhopalosiphum padi and Metopolophium dirhodum during the years of experiment; (ii) PAV and MAV were the commonest viruses and RPV was relatively scarce; (iii) during spring M. dirhodum appeared to be the most important MAV vector and nearly as good a PAV vector as R. padi; (iv) during autumn R. padi was the only vector of the three viruses with mixed transmission allowing it to transmit also MAV probably by heteroencapsidation. To give an indication of the risk of infection, infectivity indices were calculated by multiplying the numbers of aphids caught by the 12.2 m suction trap by the proportion that were infective. These infectivity indices agreed with field records of primary infections.  相似文献   
6.
7.
Abstract 1 Recommended and reduced rate applications of pirimicarb and alpha‐cypermethrin were applied to winter wheat crops to control summer infestations of grain aphid (Sitobion avenae) and rose‐grain aphid (Metopolophium dirhodum). 2 Aphid numbers were assessed weekly and the yield response to treatment application was compared with accumulated aphid days on the crop. 3 Responses to aphicide treatment varied between sites according to variations in the subsequent development of aphid populations under varying weather conditions and differential pressures from aphid natural enemies. 4 Alpha‐cypermethrin treatment reduced spider density at most sites, and also resulted in a resurgence of aphid populations at three sites.  相似文献   
8.
Abstract Glasshouse and laboratory experiments were conducted with Aphidius rhopalosiphi parasitizing Metopolophium dirhodum to test whether the presence in the same environment of another plant species (tomato or marigold) induced aerial allelopathy in wheat plants.
Emerging parasitoids were offered the choice of two odours of wheat plants in an olfactometer – wheat grown alone and wheat grown in the presence of the second plant species.
Female parasitoids responded more strongly than males, but both sexes preferred the odour of wheat grown in the environment in which they had developed (i.e. with or without the second plant species present).
Moving the tomato plants from the cages where they had been placed with wheat to the cages that had previously had wheat alone just before the aphid mummy formed showed that the odour environment the emerging parasitoid responded to was that of the mummy rather than that of the developing parasitoid larva. From this it was concluded that the parasitoids in the olfactometer were responding not only to wheat volatiles, but also to tomato volatiles absorbed on the surface of the mummy and encountered by the emerging adult parasitoid.
By excising the parasitoid pupa from the mummy formed on one wheat cultivar, and offering the emerging parasitoids the surface of aphid mummies formed on a different cultivar, it was confirmed that olfactometer responses represented a learning of the chemistry of the surface of the mummy encountered at or after emergence.  相似文献   
9.
New and extensively revised keys are given to help identification of the European species of Metopolophium Mordvilko, 1914. The morphs keyed are (1) the apterous viviparous females from Gramineac, (2) the alate viviparous females and (3) the males and oviparous females of those species that overwinter as eggs on Rosa spp. Taxonomic notes are given on some individual species. Two new taxa, M. fasciatum sp. nov., and M. festucae (Theobald) cerealium subsp. nov. are described. Metopolophium myrmecophilum (Theobald) becomes a new synonym of M. festucae (Theobald), sensu stricto , and the resulting question of the possible conservation of the latter, which is the junior subjective synonym, is discussed. A revised checklist of the European species of Metopolophium is given.  相似文献   
10.
Abstract 1. Variation in plant chemistry does not only mediate interactions between plants and herbivores but also those between herbivores and their natural enemies, and plants and natural enemies. 2. Endophytic fungi complete their whole life cycle within the host plant’s tissue and are associated with a large diversity of plant species. Endophytes of the genus Neotyphodium alter the chemistry of the host plant by producing herbivore toxic alkaloids. 3. Here we asked whether the endophyte‐tolerant aphid species Metopolophium festucae could be defended against its parasitoid Aphidius ervi when feeding on endophyte‐infected plants. In a laboratory experiment, we compared life‐history traits of A. ervi when exposed to hosts on endophyte‐infected or endophyte‐free Lolium perenne. 4. The presence of endophytes significantly increased larval and pupal development times, but did not affect the mortality of immature parasitoids or the longevity of the adults. Although the number of parasitoid mummies tended to be reduced on endophyte‐infected plants, the number of emerging parasitoids did not differ significantly between the two treatments. 5. This shows that the metabolism of individual aphids feeding on infected plants may be changed and help in the defence against parasitoids. An increase in parasitoid development time should ultimately reduce the population growth of A. ervi. Therefore, endophyte presence may represent an advantage for endophyte‐tolerant aphid species through extended parasitoid development and its effect on parasitoid population dynamics.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号