FACTORS AFFECTING THE SPREAD OF APHID-BORNE VIRUSES IN POTATO IN EASTERN SCOTLAND

Experiments at Invergowrie, south-east Perthshire, showed that the extent of spread of potato leaf-roll and Y viruses varied from year to year and that virus Y consistently spread more than leaf roll. Most spread of Virus Y occurred before the end of June and of leaf-roll virus before the end of July. Both viruses spread slightly more in late- than in early-planted crops. When plants with leaf roll and already colonized by Myzus persicae were placed in a healthy crop of Majestic potatoes at intervals during the season, the amount of virus spread decreased rapidly with increasing age of the crop. Spread of leaf roll occurred in all of twenty-five 'seed' crops in different districts of eastern Scotland in 1955 but in only twenty out of thirty-six similar crops in 1956. Annual and regional differences in virus spread appear to reflect differences in the time at which migrant aphids reach potato crops in early summer and the rate at which infestation builds up in the crops.     

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.     

THE CORRELATION OF APHID NUMBERS WITH THE SPREAD OF LEAF ROLL AND RUGOSE MOSAIC IN POTATO CROPS

An analysis of the results of experiments in different parts of England and Wales from 1941 to 1947 on the spread of potato leaf roll and rugose mosaic showed that leaf roll spread was correlated with the number of alate Myzus persicae (Sulzer) caught on sticky traps throughout the potato-growing season; there was some correlation with the maximum count of M. persicae per 100 leaves, but this possibly results from the correlation between trapped aphids and the number per 100 leaves. Spread of rugose mosaic (potato virus Y) was correlated to a lesser degree with number of M, persicae , perhaps because other aphid species are often vectors. With both diseases higher correlations were obtained when the infected plants were dispersed among the healthy crop than when they were placed together in a row. It is concluded that it is possible to predict the average health of potato stocks in the following year from average trap data; further work may enable the health of individual stocks to be predicted.     

PRELIMINARY STUDIES ON POTATO APHIDS IN NORTH AND NORTH-EAST SCOTLAND

Studies of potato aphids made in the potato seed-growing areas of north and north-east Scotland during 1950-3 showed that potato plants were first infested during July, but with few aphids; maximum populations did not develop until mid-late August or early September, which is the period of potato haulm destruction in seed crops. Myzus persicae (Sulzer) was scarce in rural districts and most numerous near urban areas. The main influx of alatae occurred in early August. Aulacorthum solani (Kltb.) was the predominant species north of Inverness. Macrosiphum euphorbiae (Thomas) was present in small numbers in many potato fields, but Aphis nasturtii (Kltb.) was extremely scarce.
Because of the small numbers of aphids found during two years by examining two or three compound leaves per haulm, it was preferable to count the aphids on one main stem and all its leaves.
Stove-pipe sticky traps provided information complementary to complete stem/leaf examination, but are considered to be of doubtful use in an area where aphids are few.     

THE USE OF SOIL INSECTICIDES TO CONTROL POTATO APHIDS AND VIRUS DISEASES

A replicated trial was done to find whether the insecticides Thimet and Rogor applied in the soil affected the spread of aphid-transmitted viruses from infected to healthy plants with potato crops. The insecticides were applied at planting as activated carbon formulations at rates equal in cost to three sprays with DDT emulsion at 2 lb. DDT per acre. The infected plants were removed (rogued) in late June.
Thimet applied along the furrows with the fertilizer, and Rogor applied in individual doses beneath each tuber, kept the plants free from aphids from a week after the plants emerged until early August. Thimet in individual doses was less effective but greatly decreased the aphid infestation. All treatments prevented or greatly decreased the spread of leaf-roll virus, but they only slightly decreased the spread of virus Y. No treatment damaged the plants or depressed yields significantly.
Tubers harvested from the plots treated with insecticides contained only very small quantities of the insecticides, but shoots from them, when infested with adult Myzus persicae (Sulz.), carried fewer aphids a week after infestation than did shoots from control tubers. Shoots of tubers from treated plots also grew more slowly than those from the controls.
The aphicidal efficiency of Thimet applied as individual doses separated from the tubers by distances of up to 6 in., decreased as the distance increased, but the effect of distance became less as time passed.
Reasons for the differences in the behaviour of the insecticides are discussed, and the possibilities that the method offers to control virus diseases. The application of insecticides to soil promises to be a useful way of controlling the spread of viruses, provided the harvested crop is free from toxic residues.     

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.     

CHANGES IN THE TRANSMISSIBILITY BY APHIDS OF A STRAIN OF CUCUMBER MOSAIC VIRUS

A strain of cucumber mosaic virus isolated from a spinach plant in 1946 was readily transmitted by Myzus persicae until 1955 when it lost this property, although it was still being propagated in conditions in which other strains remained transmissible. M. circumflexus also transmitted other strains but not this one. It was transmitted as readily as other strains by Aphis gossypii and Myzus ascalonicus. M. ascalonicus transmitted less frequently than Aphis gossypii. Transmission of the spinach strain by other aphids did not make it transmissible by Myzus persicae ; nor did propagation in different plant species or several passages through spinach. In 1955 the spinach strain was occasionally transmitted by M. persicae , but the cultures isolated in this way were no more readily transmissible by the aphid than was the bulk culture maintained by manual inoculation of sap, and after a few weeks all cultures ceased to be transmitted by M. persicae.     

THE EFFECT OF DIFFERENT HOST PLANTS OF POTATO VIRUS C IN DETERMINING ITS TRANSMISSION BY APHIDS

A stock of potato virus C derived from Edgecote Purple potatoes in 1945 was not then transmitted by aphids, although more than 2000 aphids were used in conditions optimal for transmitting the serologically related potato virus Y. This stock of virus C has been propagated continuously since, by manual inoculation in a series of Nicotiana glutinosa and N. tabacum , and in 1955 it was transmitted by the aphid Myzus persicae (Sulz.): about one in twenty of the aphids transmitted it compared with one in two for potato virus Y.
Virus C derived from the Edgecote Purple potatoes in 1955 was not transmitted by aphids; both stocks of virus C produced only local lesions in Majestic potato leaves, and gave similar symptoms in tobacco.
When inoculated to Majestic potatoes and then returned to tobacco plants, potato virus C usually ceased to be aphid transmitted and did not recover this property in any of the subsequent subcultures.
Transmission from stock by aphids did not isolate a strain of virus C which was any more readily transmitted by aphids, indeed, for the first two or three subcultures, aphids usually transmitted more readily from plants inoculated manually. But the few isolates which remained aphid transmissible, after a second passage through potato, were rather readily transmitted.
These results suggest that the ability of a virus to be aphid transmitted is, at least in part, determined by the host plant in which it is multiplying, but the nature of the changes which determine this ability are unknown.     

Local and systemic responses induced by aphids in Solanum tuberosum plants

The aphids Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer) (Homoptera: Aphididae) are serious pests of potato (Solanum tuberosum L.) (Solanaceae), notably in transmitting several plant viruses. Heterospecific interactions may occur between these two species as they are often seen at the same time on the same potato plant in the field. As aphid infestation is known to induce both local and systemic changes, we conducted experiments to determine the effect of previous infestation on probing behaviour and feeding‐related parameters. We used the DC electrical penetration graph technique to characterize the influence of previous infestation by conspecific M. persicae or by heterospecific Ma. euphorbiae on M. persicae feeding behaviour at both local and systemic levels, i.e., on previously infested leaves and on non‐previously infested leaves of infested plants, respectively. Conspecific and heterospecific infestation led to similar modification of M. persicae feeding activities. However, the effects of previous infestation occurring at the local level were opposite to those observed at the systemic level. Myzus persicae food acceptance was slightly enhanced on previously infested leaves, whereas it was inhibited on non‐infested leaves of infested plants, which indicated an induced resistance mechanism. Our results advance the understanding of the mechanisms involved in aphid–host plant acceptance and colonization processes on potato plants in conspecific and heterospecific situations.     

Analysis of clonal diversity of the peach–potato aphid, Myzus persicae (Sulzer), in Scotland, UK and evidence for the existence of a predominant clone

Clones of the peach–potato aphid, Myzus persicae (Sulzer), mostly from Scotland, UK were examined using an rDNA fingerprinting technique. Eighty patterns (genotypes) were found amongst the 276 clones. A large number of clones (30%) from all sample areas in Scotland exhibited the same simple pattern, suggesting the presence of a single M. persicae clone. There was no difference in genotype distributions between M. persicae collected from brassica or potato crops, suggesting that host-adapted genotypes have no advantage in the field. Different fingerprints were randomly distributed in the environment, although clones taken from the same leaf were more often the same fingerprint. Highly distinctive fingerprints, which were more widely distributed, suggest that this technique could be used to follow individual clones. In addition to the common clonal type, multiple fingerprint bands were found over successive years, implying that, in Scotland, local overwintering asexual populations are the most common source of M. persicae in the following year.     

Field studies of potato leaf roll virus spread in south-eastern Scotland, 1962–1969, in relation to aphid populations and other factors

Between 1962 and 1967 spread of potato leaf roll virus (PLRV) and the pattern of potato crop infestation by common potato aphids was investigated at sites in the counties of East Lothian, West Lothian, Midlothian and Berwickshire. Within this area aphid activity and the extent of PLRV spread varied considerably both within years and between years.
Macrosiphum euphorbiae activity as measured by the angle of colonization method was as well correlated with PLRV spread as that for Myzus persicae , and in certain years Aulacorthum solani and Aphis fabae may become common enough to have an effect. Spread was not well correlated with site altitude or with distance from the market garden area of Musselburgh, previously thought to be the main regional overwintering centre for aphids. Evidence is presented of the more general distribution of market gardening in the area which may account for these variations. Results from infector units of different sizes and bulk samples suggest, as do earlier findings, that in southern Scotland PLRV spread is mainly from sources within the crop. The practical implications for potato certification in the region are discussed.     

甘蓝幼苗受桃蚜危害后叶片中部分酶活性的变化

对桃蚜（Myzus persicae Sulzer）危害后甘蓝（Brassica oleracea L.）幼苗叶中多酚氧化酶（PPO）、苯丙氨酸解氨酶（PAL）、过氧化物酶（POD）活性及同工酶进行了研究。结果表明,随桃蚜危害时间延长,处理叶片PPO、PAL和POD的活性与对照相比均表现出升高的趋势,方差分析表明与对照之间差异显著。同工酶电泳结果表明,POD同工酶的部分谱带随危害时间而发生变化,但EST同工酶在接虫前后则无明显的变化。     

Variation for resistance to aphids (Homoptera: Aphididae) among tomato inbred backcross lines derived from wild Lycopersicon species

Two tomato inbred backcross line (IBL) populations, derived from crosses between aphid-susceptible Lycopersicon esculentum Mill. 'Peto 95-43' X resistant wild L. pennellii Corr (D'arcy) accession LA716, and Peto 95-43 X resistant wild L. hirsutum f. glabratum Mull accession LA407, were evaluated in replicated field experiments for resistance to potato aphid, Macrosiphum euphorbiae (Thomas), and green peach aphid, Myzus persicae (Sulzer). Aphid infestation scores for each IBL and control (LA716, LA407, Peto 95-43, and susceptible 'Alta') plot were recorded weekly for 5 and 9 wk during the summers of 2000 and 2001, respectively. Aphid infestation scores from leaflets were used to calculate area under the infestation pressure curve (AUIPC), a measure of aphid infestation throughout the growing season, for each IBL and control. Score AUIPC was highly correlated with actual aphid count AUIPC, indicating that scores accurately reflected aphid infestation. Score AUIPC was also highly correlated across both years (2000 and 2001) and locations. Low score AUIPC was significantly correlated with larger plant size and sprawling, indeterminate plant growth habit. Seven IBLs, LA716, and LA407 were significantly more resistant to aphids (lower score AUIPC) than susceptible parent Peto 95-43 in both years. Two IBLs, 1034 and 1051, were not significantly different from resistant LA407 for score AUIPC in both years. The seven aphid-resistant IBLs identified here can be useful as donor parent material for resistance breeding efforts in cultivated tomato.     

Over-wintering of aphids,especially Myzus persicae,Sulzer, in root clamps

Mangold clamps in many districts of the British Isles were found to provide overwintering sites for Myzus persicae (Sulz.), Hyperomyzns staphyleae (Koch) and Aulacorthum solani (Kalt.). After a severe winter, when other means of overwintering are few, clamps may be the most important source of Myzus persicae. Only Myzus ascalonicus Doncaster was found in swede clamps.
Factors affecting the infestation of clamped mangolds by M. persicae were the number of aphids on the crop when lifted, the methods of topping and clamping the roots, and the temperature in the clamp. M. persicae was introduced on the leaves, and close topping was often an efficient means of control. Close topping did not control Hyperomyzus staphyleae; normally, this aphid does not seem to be a root-feeding species, but with artificially colonized mangolds it fed on both exposed roots and foliage. It is not known how this species enters the clamps. The temperature in clamps was influenced by that of the outside air and the type of cover, but changes were long-term and did not reflect diurnal variations in external air temperature. Straw, covered with soil, was the best form of cover.
In addition to harbouring Myzus persicae , mangold clamps are also important sources of sugar-beet yellows virus.     

植物挥发性物质对蚜虫性信息素诱蚜效果的影响(英文)

本研究首先是在不同的寄主植物中利用蚜虫性信息素进行田间诱蚜实验。结果表明寄主植物影响性信息素田间诱蚜的种类和效果。在桃园 ,以蚜虫性信息素荆芥内酯和荆芥醇为性诱剂的水盆诱捕器 ,诱到 3种蚜虫的雄蚜 ,分别是桃蚜、桃粉大尾蚜和莲缢管蚜。其中 ,桃蚜占绝大多数 ,且还被性信息素的单一组分植物提取的荆芥内酯所吸引。麦田中诱到的雄蚜为麦二叉蚜。苹果园中诱到的雄蚜是绣线菊蚜和梨中华圆尾蚜 ,且性信息素诱捕器中的数目远多于对照诱捕器。据田间诱蚜实验结果推测 ,荆芥内酯和荆芥醇对桃粉大尾蚜有吸引作用 ,荆芥内酯可能是绣线菊蚜和梨中华圆尾蚜性信息素的一个组分。另外进行的田间实验表明寄主植物挥发性物质对蚜虫性信息素诱蚜效果有影响 ,当荆芥内酯诱捕器同时释放桃叶挥发物时 ,诱到的桃蚜雄蚜数量明显增加。触角电位记录实验也表明桃蚜雄蚜对桃叶挥发物和桃芽挥发物有反应。     

The influence of size and duration of aphid infestation on host plant quality, and its effect on sugar beet yellowing virus epidemiology

This paper studies the influence of previous infestation on the host quality of sugar beet (Beta vulgaris L.) for aphids and the influence of previous infestation on sugar beet yellowing virus epidemiology. Sugar beet previously infested with Myzus persicae (Sulzer) or Aphis fabae Scopoli (Homoptera: Aphididae) had an improved host quality for subsequently infesting aphids of the same species. There was a significant negative relationship between the number of M. persicae infesting a plant and the proportion of those that died with a dark deposit in their stomachs, and a significant positive relationship between the number that settled on a plant and the number that infested it previously. Nymphs feeding on previously infested plants grew more rapidly than those on control plants. The beneficial effect of previous infestation persisted for at least 2 weeks and prolongation of the infestation beyond 2 weeks was of no further benefit to the aphids. Field grown sugar beet, previously colonised by M. persicae, was more susceptible to natural infestation by M. persicae up to 5 days after exposure. Previously infested plants were also more susceptible to infection with beet mild yellowing virus (BMYV) but not beet yellows virus (BYV), suggesting that the aphids on the previously infested sugar beet settled more readily and were more inclined to feed (and thus transmit BMYV) than aphids on the previously uninfested plants. The consequences for the control of sugar beet yellowing virus vectors are discussed.     

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.     

THE SPREAD OF VIRUS DISEASES TO SINGLE POTATO PLANTS BY WINGED APHIDS

Young potato plants in pots exposed in the open near plots of potatoes for limited periods at intervals during the summer, became infested with large numbers of winged aphids only during warm, calm and dry weather. Although visited by aphids during May and June, when much of the spread of viruses occurred in nearby potato crops, few of the potted plants became infected. Most potted plants became infected in July when alate aphids were leaving neighbouring potato crops. Widely different proportions of the exposed plants became infected in different years; in two of the three years, many more plants were infected with virus Y than with leaf roll virus.     

施钾与蚜害处理后马铃薯叶片中多酚氧化酶活性的变化

蚜虫危害是影响马铃薯Solanum tuberosum产量和品质的重要因素之一, 而多酚氧化酶（polyphenol oxidase, PPO）与植物的抗性密切相关。为了阐明施钾条件下马铃薯与桃蚜Myzus persicae的关系, 本实验通过比色法、 iTRAQ技术和蛋白免疫印迹法研究了对照（不施钾, 不接虫）、 接虫、 施钾以及施钾＋接虫4种处理后马铃薯叶片中多酚氧化酶活性的变化。结果表明： 施钾显著降低桃蚜种群数量。随着桃蚜发育期延长, 桃蚜的种群数量显著低于对照, 且6 g/株施钾量对桃蚜种群数量的抑制效果最强。以6 g/株作为施钾量, 对不同处理后马铃薯叶片中多酚氧化酶活性研究显示, 施钾、 接虫+施钾处理均使马铃薯叶片中PPO活性显著提高, 分别比对照增加了44%和67%。通过液相色谱 质谱/质谱联用仪（LC-MS/MS） 分析, 接虫、 施钾、 接虫+施钾处理均不同程度上调了PPO蛋白表达量。Western杂交结果显示： 施钾、 接虫+施钾处理显著增加了PPO的相对表达量, 且接虫+施钾处理使该相对表达量达到最高。结果说明, 施钾、 接虫+施钾处理通过诱导马铃薯叶片中的PPO活性, 从一个侧面提高了马铃薯抗蚜虫能力。     

Volatiles from potato plants infected with potato leafroll virus attract and arrest the virus vector, Myzus persicae (Homoptera: Aphididae)

The influence of viral disease symptoms on the behaviour of virus vectors has implications for disease epidemiology. Here we show that previously reported preferential colonization of potatoes infected by potato leafroll virus (genus Polerovirus) (luteovirus) (PLRV) by alatae of Myzus persicae, the principal aphid vector of PLRV, is influenced by volatile emissions from PLRV-infected plants. First, in our bioassays both differential immigration and emigration were involved in preferential colonization by aphids of PLRV-infected plants. Second, M. persicae apterae aggregated preferentially, on screening above leaflets of PLRV-infected potatoes as compared with leaflets from uninfected plants, or from plants infected with potato virus X (PVX) or potato virus Y (PVY). Third, the aphids aggregated preferentially on screening over leaflet models treated with volatiles collected from PLRV-infected plants as compared with those collected from uninfected plants. The specific cues eliciting the aphid responses were not determined, but differences between headspace volatiles of infected and uninfected plants suggest possible ones.