How symbiotic bacteria influence plant utilisation by the polyphagous aphid, Aphis fabae

To explore the effect of rearing-plant species on the contribution of the symbiotic bacterium, Buchnera, to aphid performance, larvae of Aphis fabae that contained the bacteria (symbiotic aphids) and larvae experimentally deprived of the bacteria (aposymbiotic aphids) were reared on 16 plant species. Mortality of aphids was low on most plant species. The relative growth rate (RGR) of the larvae varied with plant species, and was generally depressed by elimination of the bacteria; the mean values of RGR varied between 0 and 0.29 μg μg⁻¹ day⁻¹ for symbiotic aphids and 0 and 0.17 μg μg⁻¹ day⁻¹ for aposymbiotic aphids. The extent to which RGR was depressed by aposymbiosis varied significantly between plant species, suggesting that aphid host plant may influence the contribution of the bacteria to plant utilisation. It is proposed that the bacteria may be particularly important on plants with phloem sap of high amino acid content of low quality, i.e. low concentrations of essential amino acids. Received: 18 August 1996 / Accepted: 13 January 1997     

Plant compensation, natural biological control, and herbivory by Aphis gossypii on pre-reproductive cotton: the anatomy of a non-pest

Crop plant compensation for herbivory and the population dynamics of herbivores are two key elements in defining an herbivore's pest status. We studied the dynamics of natural, unmanipulated populations of the aphid Aphis gossypii on seedling plantings of cotton, Gossypium hirsutum and Gossypium barbadense, over a 4-year period in California's Central Valley. Aphid populations colonized all plantings, but reached densities in excess of 0.5 aphids/leaf during only one year (1991), when outbreaks occurred. Outbreak populations were, however, ephemeral; predation and parasitism suppressed aphid populations prior to the initiation of flower bud production, when cotton plant growth may become photosynthate-limited. Effective natural biological control was observed despite the action of hyperparasitoids and the heavy mortality of immature parasitoids that occurred when predators consumed parasitized aphids.We conducted manipulative experiments during 1991 and 1992 to quantify the ability of pre-reproductive G. hirsutum to compensate for aphid herbivory. In 1991 aphid populations in the high-damage treatment reached densities as high as any observed naturally during the past 37 years. Damage symptoms were severe: leaf area was reduced by up to 58% and total above-ground plant biomass was reduced by 45%. By the time of crop harvest, however, plants had compensated fully for the early damage in each of the three traits that define cotton's economic value: the timing of crop maturation, the yield of cotton fiber, and the quality of cotton fiber. Aphid feeding damage did, however, produce some changes in plant architecture that persisted throughout the growing season, including a decrease in the number of vegetative branches. In 1992 aphid populations and associated damage were much lighter, but the qualitative responses to herbivory were consistent with those observed in 1991. Plant compensation for early damage was complete for economically significant measures, and vegetative branch production was again suppressed in mature cotton plants. There was no evidence for a change in the suitability of G. hirsutum as a host plant for A. gossypii as a result of early damage (induced resistance).We conclude that pre-reproductive G. hirsutum, which has not yet begun strong allocations to reproductive structures or established architectural complexity, has retained effective means of compensating for herbivory. In contrast to other systems exhibiting strong compensation, G. hirsutum appears to compensate in part by enhancing apical dominance. The recognition of early-season A. gossypii as non-pests is critical to the sustainability of cotton production, because it will allow growers to forego pesticide applications that accelerate the evolution of pesticide-resistance and disrupt natural communities of predators and parasitoids.Deceased, formerly at the Shafter Research Station, 17053 Shafter Ave., Shafter, CA 93263, USA     

棉株内含物和外源JH对棉蚜成蚜有翅率及种群消长的影响

通过系统研究得出 ,棉花植株中油酸、缬氨酸和脯氨酸对棉蚜种群消长有影响 ,油酸、天门冬氨酸和丝氨酸对棉蚜成蚜有翅率有影响 ;外源保幼激素类似物对棉蚜种群消长和成蚜有翅率均有重要影响 .     

Peptide modification by incorporation ofα-trifluoromethyl substituted amino acids

Summary Metabolic stabilization of pharmacologically active peptides can be achieved by incorporation of sterically hindered non-natural amino acids, e.g. C ^, -disubstituted amino acids.-Trifluoromethyl substituted amino acids, a subclass of C ^, -disubstituted amino acids, also fulfil this requirement while featuring additional properties based on the electronic influence of the fluorine substituents.This review summarizes the results concerning the stability of peptides containing-TFM amino acids towards proteolysis by-chymotrypsin. Furthermore, configurational effects of-TFMAla on the proteolytic stability of peptides are explained using empirical force field calculations. The influence of-TFMAla incorporation on the secondary structure of selected tripeptide amides is compared to the effects exerted by its fluorine-free analogue, aminoisobutyric acid.Finally, results on metabolic stabilization and biological activity of modified thyrotropin releasing hormone are interpreted.     

Stylet activity of cowpea aphid (Homoptera: Aphididae) on leaf extracts of resistant and susceptible cowpea cultivars

Electrical penetration graph recordings using direct current (DC-EPGs) were used to analyze aspects of the probing behavior of cowpea aphid,Aphis craccivora Koch, on intact plants and on hexane, ethyl acetate, and methanol extracts of leaves of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpeaVigna unguiculata (L.) Walp. In one set of experiments, recordings were done on plants with or without parafilm wrapping, or on plants painted with raw leaf juice and extracts of the two cultivars. In another study, recordings were done on leaf extracts homogenized in water or in 0.5M sucrose solution and then placed in parafilm membrane sachets. Electrodes were inserted into soil mix for the experiments on potted plants or into extract fractions and raw juice for the membrane feeding experiments on leaf extracts in parafilm sachets. Waveform signals were recorded from resistance fluctuations from interactions between aphids and substrates, and electromotive forces generated within each preparation. ICV-12 plants with or without parafilm wrapping, and ethyl acetate extracts and raw juice of that cultivar significantly (P≤0.05) reduced stylet penetration behavior. Thus, antixenosis as manifested by disruption of aphid stylet activity on host substrates, appeared to be a governing modality of aphid resistance in ICV-12.     

RELEVANCE OF PLANT VOLATILES TO SEX PHERO‐MONE IN LURING APHIDS IN THE FIELD1

Abstract Outdoor trials were made to test the responses of male aphids to pheromone lures in fields with different host‐plants, in order to know whether host‐plants would affect catches of males to pheromone lures. In peach orchard, males of three aphid species, i.e. Myzus persicae, Hyalopterus amygdali and Rhopalosiphum nymphaeae, were found in traps baited with aphid sex pheromone nepetalactone and nepetalactol. The most numerous numbers was M, persicae and it was also attracted by plant‐derived nepetalactone alone in peach orchard and cabbage garden. Schizaphis graminum males were caught in water traps in wheat field. In apple orchard, males of two aphid species, Aphis cifricola and Sappaphis sinipiricola were caught in significantly larger numbers in the pheromone traps than in the control traps. Field study indicated that the sex pheromone of H. amygduli comprises either one or both of nepetalactone and nepetalactol, and nepetalactone may be one component of sex pheromones of A cifricola and S sinipiricola Another field trial had shown that catches were increased if volatiles from a steam‐distilled extract of peach leaves were released simultaneously with nepetalactone. Elec‐troantennograms (EAGs) were recorded from males of M. persicae to volatiles of peach leaves and buds.     

Influence of prey quality on the fitness of two phenotypes of Harmonia axyridis adults

The performance of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) adults of the aulica and nigra phenotypes fed on Aphis fabae Scopoli and Myzus persicae (Sulzer) was compared by measuring their voracity, daily biomass consumption, daily weight gain, efficiency of food utilisation, and reproductive capacity. Our results demonstrated differences in the suitability of A. fabae and M. persicae for the two phenotypes of the predator. This suggests that either differences occur in the nutritive requirements of the predators, or in the nutritive value of the two prey species. Both A. fabae and M. persicae supported the growth and oviposition of the aulica and nigra phenotypes. Although nigra females consumed fewer M. persicae, they achieved the same daily weight gain as aulica females. The predator phenotypes consumed the same amount of A. fabae, but the daily weight gain of aulica females was higher than that of nigra. The two predator phenotypes had the same feeding efficiency when consuming M. persicae or A. fabae. The reproductive capacity of nigra females was higher, when this phenotype consumed A. fabae rather than M. persicae.     

Cucurbit aphid‐borne yellows virus (CABYV) modifies the alighting,settling and probing behaviour of its vector Aphis gossypii favouring its own spread

Plant pathogens are able to influence the behaviour and fitness of their vectors in such a way that changes in plant–pathogen–vector interactions can affect their transmission. Such influence can be direct or indirect, depending on whether it is mediated by the presence of the pathogen in the vector's body or by host changes as a consequence of pathogen infection. We report the effect that the persistently aphid‐transmitted Cucurbit aphid‐borne yellows virus (CABYV, Polerovirus) can induce on the alighting, settling and probing behaviour activities of its vector, the cotton aphid Aphis gossypii. Only minor direct changes on aphid feeding behaviour were observed when viruliferous aphids fed on non‐infected plants. However, the feeding behaviour of non‐viruliferous aphids was very different on CABYV‐infected than on non‐infected plants. Non‐viruliferous aphids spent longer time feeding from the phloem in CABYV‐infected plants compared to non‐infected plants, suggesting that CABYV indirectly manipulates aphid feeding behaviour through its shared host plant in order to favour viral acquisition. Viruliferous aphids showed a clear preference for non‐infected over CABYV‐infected plants at short and long time, while such behaviour was not observed for non‐viruliferous aphids. Overall, our results indicate that CABYV induces changes in its host plant that modifies aphid feeding behaviour in a way that virus acquisition from infected plants is enhanced. Once the aphids become viruliferous they prefer to settle on healthy plants, leading to optimise the transmission and spread of this phloem‐limited virus.     

The effect of flowering calendula and cuphea plants on Orius insidiosus survival and predation of Aphis glycines

Flowering oilseed crops have the potential to diversify agroecosystems currently dominated by corn and soybeans and improve the provision of ecosystem services such as pest control. Nectar and pollen feeding may increase natural enemy fitness and searching behaviour, increasing their survival and prey consumption rates. The soybean aphid (Aphis glycines Matsumura; Hemiptera: Aphididae) is a particularly widespread and costly agricultural pest. In this study, we evaluate the effects of two flowering oilseed crops, cuphea and calendula, on the survival of the insidious flower bug (Orius insidiosus Say; Hemiptera: Anthocoridae) and its consumption levels of A. glycines placed on soybean plants. We also evaluated the survival of O. insidiosus when placed on glandular and non-glandular cuphea varieties. The amount of A. glycines that remained unconsumed by O. insidiosus did not differ among treatments. Because mortality levels of O. insidiosus were higher on glandular compared to non-glandular cuphea plants, glandular trichomes, or plant hairs, may play a role in impeding movement and prey consumption by O. insidious.     

宁夏危害枸杞的蚜虫种类为棉蚜、桃蚜和豆蚜

宁夏是我国最重要的枸杞Lycium chinense Miller生产基地,蚜虫是危害枸杞的重要害虫。多年来枸杞蚜虫一直作为一个未定名物种使用Aphis sp.。2015年作者对宁夏危害枸杞的蚜虫进行了标本采集,经中国科学院动物研究所乔格侠研究员鉴定确认是常见的3种蚜虫,分别是棉蚜Aphis gossypii Glover、桃蚜Myzus persicae(Sulzer)和豆蚜Aphis craccivora Koch。本文提供了它们的鉴定检索表和简要形态特征描述、寄主植物和分布情况。