Amphorophora Rubi Research Articles

Re-visiting the Aphidius urticae s. str. group: re-description of Aphidius rubi Starý and A. silvaticus Starý (Hymenoptera: Braconidae: Aphidiinae).

Here we tested Aphidius urticae s. str. host-associated lineages from Microlophium carnosum (Buckton), Amphorophora rubi (Kaltenbach), Macrosiphum funestum (Macchiati) and Aulacorthum vaccinii Hille Ris Lambers with the barcoding region of the mitochondrial cytochrome oxidase subunit I gene used to analyse population differences and elucidate phylogenetic relationships between the separated taxa. This molecular marker has been shown to be the most informative molecular marker in resolving species complexes in aphidiine parasitoids. Analyses of the mitochondrial sequences revealed the existence of three clearly separated mitochondrial lineages of A. urticae s. str. group associated with: i) Macrosiphum funestum and Aulacorthum vaccinii aphid hosts, ii) Microlophium carnosum and iii) Amphorophora rubi. This corresponds to the initial descriptions of A. rubi, A. silvaticus and A. urticae and their aphid host associations prior to synonymization of A. rubi and A. silvaticus with A. urticae. On the other hand, significant evolutionary distances ranging from 2.3 to 9.2% between the three mitochondrial lineages were not accompanied by clear morphological differences. Therefore, re-descriptions of A. rubi and A. silvaticus are presented, together with their morphological differentiation in a key, as well as their phylogenetic relationships and genetical differentiation.

Diversity of bacteria associated with natural aphid populations.

The bacterial communities of aphids were investigated by terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments generated by PCR with general eubacterial primers. By both methods, the gamma-proteobacterium Buchnera was detected in laboratory cultures of six parthenogenetic lines of the pea aphid Acyrthosiphon pisum and one line of the black bean aphid Aphis fabae, and one or more of four previously described bacterial taxa were also detected in all aphid lines except one of A. pisum. These latter bacteria, collectively known as secondary symbionts or accessory bacteria, comprised three taxa of gamma-proteobacteria (R-type [PASS], T-type [PABS], and U-type [PAUS]) and a rickettsia (S-type [PAR]). Complementary analysis of aphids from natural populations of four aphid species (A. pisum [n = 74], Amphorophora rubi [n = 109], Aphis sarothamni [n = 42], and Microlophium carnosum [n = 101]) from a single geographical location revealed Buchnera and up to three taxa of accessory bacteria, but no other bacterial taxa, in each aphid. The prevalence of accessory bacterial taxa varied significantly among aphid species but not with the sampling month (between June and August 2000). These results indicate that the accessory bacterial taxa are distributed across multiple aphid species, although with variable prevalence, and that laboratory culture does not generally result in a shift in the bacterial community in aphids. Both the transmission patterns of the accessory bacteria between individual aphids and their impact on aphid fitness are suggested to influence the prevalence of accessory bacterial taxa in natural aphid populations.

Separation of three Rubus‐feeding species of aphid — Sitobion fragariae (Wlk.), Macrosiphum funestum (Macch.) and Amphorophora rubi (Kalt.) (Hemiptera: Aphididae) — by electrophoresis

SummaryFour species of aphid infest wild and cultivated blackberry (Rubus fruticosus agg., R. lachiatus, etc) and other Rubus species in Britain and Continental Europe, ‐ Sitobion fragariae (Walker), Macrosiphum funestum (Macchiati), Amphorophora rubi (Kaltenbach) and Aphis ruborurn (Bösrner). The nymphs, especially the early instars, of the first three species are fairly difficult to differentiate morphologically. However, they can clearly be separated using electrophoresis. The present paper describes diagnostic enzyme/isoenzyme banding patterns which allow differentiation of the first three species as apterous and alate adults and their instars using two enzymes ‐ carboxylesterase (EST) and phosphatase (PHOS).

Parasitoid spectrum of Acyrthosiphon-aphids in Central Asia (Hymenoptera: Aphidiidae)

AbstractThe spectrum of parasitoids (namely of Acyrthosiphon pisum Harris and A. gossypii Mordw.) is reviewed with respect to the host range of the particular species. Distribution of parasitoids is analysed with respect to the vertical zonation and corresponding changes in host range and relative abundance of the species. Monoctonus tianshanensis n.sp. (from Amphorophora rubi Kalt. and Impatientinum asiaticum Nevs.) and Aphidius popovi n.sp. (from Amphorophora catharinae Nevs.) are described.

The effect of resistance to Amphorophora rubi in raspberry (Rubus idaeus) on the spread of aphid‐borne viruses

SUMMARYThe effectiveness of resistance to the aphid Amphorophora rubi in restricting the spread of aphid‐borne viruses was assessed in a field experiment using six genotypes of red raspberry. In one block of the experiment, the genotypes alternated with rows of virus‐infected Mailing Jewel raspberry, and in the other they alternated with virus‐free Mailing Jewel. During 4 years, the numbers of A. rubi and the amount of 52V virus spread in the two blocks were similar, suggesting that this virus was mostly introduced from outside the plots.Lloyd George and Mailing Jewel raspberry became heavily infested with A. rubi and were rapidly infected with raspberry leaf mottle, raspberry leaf spot and 52V viruses. Glen Clova and Norfolk Giant raspberry, which contain minor genes for resistance to A. rubi, were infested with fewer A. rubi and virus spread more slowly in these cultivars. A. rubi were rare on Mailing Orion and an East Mailing raspberry selection (888/49) which have genes A1 and A10 respectively for resistance to A.rubi, and these plants remained largely free of virus. The role of minor and major gene resistance to A. rubi in restricting virus spread is discussed.A few Macrosiphum euphorbiae and Myzus ornatus were recorded on several of the raspberry genotypes.

Association of different kinds of bacilliform particle with vein chlorosis and mosaic diseases of raspberry (Rubus idaeus)

SUMMARYThin sections of diseased raspberry (Rubus idaeus) were examined by electron microscopy. Plants of the cv. Baumforth's B and of an aphid (Amphorophora rubi)‐resistant breeding selection (6820/54), both infected with raspberry vein chlorosis virus (RVCV) but not with other detectable viruses, contained large bacilliform particles c. 430 × 65 nm. Particles occurred in the cytoplasm and perinuclear space of a small proportion of xylem parenchyma cells. They had an inner core c. 25–30 nm in diameter with cross‐banding of periodicity 4·5 nm, and were bounded by an outer membrane. They are probably the particles of RVCV.Plants of cv. Mailing Jewel and of a selection (M14) both showing symptoms of raspberry mosaic (veinbanding) disease contained smaller bacilliform particles c. 125 × 30 nm, which occurred singly or in clusters in the cytoplasm of a small proportion of vascular parenchyma cells. It is not known which, if any, of the viruses associated with raspberry mosaic are represented by the particles.

Some Properties of a Mechanically Transmissible Virus Widespread in Raspberry (Rubus idaeus) in Scotland

SUMMARYA virus, code‐named 52V, was obtained from 16 cultivars and seedlings of red raspberry by inoculation of sap to Chenopodium quinoa during spring or autumn. Some raspberry plants were infected with 52V after six months in the field, and more than 50 per cent of the plants of some cultivars were infected after four years. The virus was also obtained from Rubus occidentalis plants previously infected with virus from red raspberry by means of aphids (Amphorophora rubi and Aulacorthum solani). These aphids transmitted 52V from red raspberry to C. quinoa.52V was transmitted by inoculation of sap to six herbaceous species but induced symptoms only in Chenopodiaceae. In C. quinoa sap, 52V lost infectivity after dilution to 10−2, heating for 10 min at 52·5°C, storage at 18°C for 24 hr or treatment with n‐butanol to 8·5 per cent (v/v). Preparations made by clarifying extracts with chloroform or ether followed by differential centrifugation contained a few isometric particles c. 30 nm in diameter which may be those of the virus.

VARIABILITY IN THE WILD RASPBERRY

SummarySurveys of wild raspberries in Europe and Britain, and of progenies raised from seed collected in the wild, showed widespread polymorphism for the gene H (hairy/subglabrous canes) and less frequent polymorphism for P (spine colour intensifier). No yellow fruited (t), spineless (s) or sepaloid (sx3) plants were seen. Breeding experiments snowed there was no close linkage between H and the incompatibility S locus. Male sterility occurred in three out of nineteen progenies and partial female sterility, accompanied by abnormalities affecting vegetative characters, segregated in three out of eleven progenies from sibbing four seedlings. This condition was due to a semi‐lethal gene, gr.Progenies varied widely in response to powdery mildew (Sphaerotheca macularis (Fr.) Jaczewski), from 0 to 100% of seedlings proving resistant. The incidence of resistance in progenies tended to increase with increasing altitudinal origin of the parent, total percentage resistance in all progenies being 6.6, 59.6, 64.3 and 97.2 for parental altitudes of less than 500 m, 500–1000 m, 1000–1500 m and over 1500 m, respectively. It is suggested that higher mildew resistance may be a secondary effect of greater cold hardiness at high altitudes.Resistance to the aphid Amphorophora rubi occurred in seventeen out of twenty‐eight wild progenies. Resistance to strain 3 of the aphid was more common than to strain 2; in both cases, the incidence of resistance tended to decrease with increasing altitude of the parent. Only one very small progeny was homozygous for resistance. Resistant and susceptible classes were usually sharply differentiated, indicating the segregation of major resistance genes. Genes conferring, respectively, strain 2 resistance alone, strain 3 resistance alone and resistance to both strains, were isolated.

A new gene from Rubus occidentalis L. For resistance to strains 1, 2, and 3 of the rubus aphid, Amphorophora rubi Kalt.

A new gene, A 10, conferring strong resistance to Amphorophora rubi Strains 1, 2, and 3, has been isolated. Strain 4 has proved impossible to maintain so its response to A 10 is unknown.

The Distribution, Abundance, and Genetic Relationships of Four Strains of the Rubus Aphid(Amphorophora Rubi(Kalt.)) in Relation To Raspberry Breeding

Field collections of Amphorophora rubi (Kalt.), the rubus aphid, from 28 localities were classified into strains by their reaction to the raspberry varieties Mailing Landmark and Seedling 136/2, the former being resistant to strains 1 and 3 of the aphid, and the latter to strain 2. A new strain, numbered 4, was isolated, capable of breeding on both varieties, and it was found that the field distribution of this strain and of strain 2 was closely linked with the variety Landmark.Strains 2 and 4 appeared to have low fertility when inbred and, after a year of rearing in captivity, were all found to be homozygous for the genes conditioning their host plant reaction. Hybridization of strains 2 and 3 led to increased fertility and to the production, in the F2, of strain 4 types. An hypothesis postulating single-gene control of the ability to colonize Landmark and 136/2 is advanced and genotypes for the four strains are suggested.The implications of the discovery of strain 4 for plant breeding for resistance using the plant genes A1+A2 or A1+A3 are discussed, since strain 4 is capable of breeding on plants carrying these combinations. It is concluded that the low population levels of strain 4 are due to low fertility, and that the gene combination A1+A2 or Al+A3 should still be of use, particularly if field sources of strains 2 and 4 are reduced or eliminated by grubbing out any plantations of the variety Landmark.

STUDIES ON RUBUS VIRUS DISEASES IN BRITISH COLUMBIA: VII. RASPBERRY VEIN CHLOROSIS

A virus disease occurring in the Lloyd George variety of red raspberry (Rubus idaeus L.) in British Columbia has been identified as raspberry vein chlorosis, a disease previously reported from Scotland. The virus was transmitted to the Lloyd George and Washington varieties of red raspberry, loganberry (R. loganobaccus Bailey), and the Alpine strawberry (Fragaria vesca L.) by the aphid Aphis idaei V.d.G. In each of these hosts, the characteristic symptom was a net-like chlorosis of the tissue bordering the smaller veins of the leaf. The large raspberry aphid, Amphorophora rubi (Kalt.), was not a vector. Experiments using A. idaei showed that most individuals require more than 1 day on the virus source to become viruliferous. The length of time that aphids remained viruliferous depended upon the conditions of the test; viruliferous aphids feeding upon healthy raspberry plants lost the ability to transmit the virus within a day, while those feeding upon strawberry, or held in a Petri dish without food, retained the virus longer than 1 day.

Genetics of resistance to Amphorophora rubi (Kalt.) in the raspberry II. The genes A2–A7 from the American variety, Chief

The American raspberry variety Chief is shown to carry three dominant genes, A5, A6 and A7, each capable of conferring strong resistance to Amphorophora rubi strain 1.Chief also carries three genes, A2, A3 and A4, for resistance to A. rubi strain 2. A2 is a dominant gene conferring full resistance by itself; A3 and A4 are dominant complementaries, neither gene by itself having any effect on resistance. A5 is linked with either A3 or A4 with a crossover value of 10%.The gene A1 from Baumforth A, which confers resistance to strains 1 and 3, when combined with A3 gives resistance to strain 2 also. Thus the three strains of A. rubi at present recognized on raspberries in Britain can be controlled by using either the combination A1A2 or A1A3.

STUDIES OF VIRUS DISEASES OF STRAWBERRIES IN BRITISH COLUMBIA: III. TRANSMISSION OF STRAWBERRY VIRUSES BY APHIDS

Eleven aphid species commonly found on rosaceous plants were tested as vectors of eight strawberry viruses. Amphorophora rubi (Kalt.), Aphis rubifolii (Thomas), Aulacorthum solani (Kalt.), Macrosiphum rosae (L.), Myzus ascalonicus Doncaster, M. ornatus Laing, M. persicae (Sulz.), Pentatrichopus fragaefolii (Cock.), P. tetrarhodus (Walk.), and P. thomasi Ris Lambers transmitted the vein banding virus from one or both of two sources. P. fragaefolii, P. tetrarhodus, and P. thomasi transmitted mild mottle, while only P. fragaefolii and P. thomasi transmitted curly-dwarf mottle. M. rosae transmitted vein banding and possibly mild yellow edge. Aphis forbesi Weed failed to transmit any of the viruses tested. None of the species tested transmitted witches’ broom, crinkle, or strawberry latent-A virus.

STUDIES ON RUBUS VIRUS DISEASES IN BRITISH COLUMBIA: VI. VARIETAL SUSCEPTIBILITY TO APHID INFESTATION IN RELATION TO VIRUS ACQUISITION

Field populations of the large raspberry aphid, Amphorophora rubi (Kalt.), were observed for 4 years on 13 varieties of raspberry. Lloyd George and St. Walfried were immune, Malling Enterprise and Malling Promise were resistant, and the remainder were susceptible to infestation. Each variety was naturally infected with black raspberry necrosis virus. Vector studies demonstrated that this virus was acquired with difficulty from the immune varieties and also from the susceptible variety St. Regis, but was readily acquired from the remaining 10 varieties.

Three new Strains of Amphorophora rubi (Kalt.) on cultivated Raspberries in England

Previous work on strains of Amphorophora rubi (Kalt.) is discussed and evidence is presented to show that the form on European raspberry can be divided into three strains. These are designated European raspberry strain 1, 2 and 3. The distribution, abundance and importance of the strains in relation to plant breeding for resistance to A. rubi is discussed.

Relationships of the Strawberry Viruses of England and California

A comparison made at the East Mailing Research Station of the strawberry viruses known in California with those of England indicated that the curly-dwarf mottle, mottle, mild yellow-edge, latent-A, and crinkle viruses occurred in both England and California; the rusty-leaf mottle, lesion-B, vein chlorosis, green petal, mosaic, raspberry yellow dwarf, and raspberry ring spot viruses were not known in California; the vein banding, yellow vein banding, latent-B, lesion-A, and western aster yellows viruses were not found in England; while the leaf-curl virus was known only in plants in the East Mailing Research Station glasshouse. The viruses studied could be provisionally grouped according to their symptoms and vector-host relationships, but the evidence obtained did not clearly define the level of relationships among the viruses within the groups. Comparative tests suggested that the incubation period for development of symptoms in the plant and the rate of virus loss by vectors are useful characters in distinguishing between strawberry viruses, but the acquisition threshold period and rate of virus acquisition appeared to be less useful. Rusty-leaf mottle, curly-dwarf mottle, yellow vein banding, lesion-A, and lesion-B are newly described viruses with aphid vectors. Pentatrichopus thomasi and P. thomasi ssp. jacobi are reported to be vectors of strawberry viruses while Amphorophora rubi was demonstrated to be a vector of the leaf-curl virus. Duchesnea indica and Nicotiana bigelovii are newly determined experimental and natural hosts respectively of the western aster yellows virus.

Observations on the Reproductive Behaviour of Amphorophora rubi (Kalt.), with special Reference to the Phenomenon of Insect Resistance in Raspberries

Sixteen varieties of Rubus, comprising four species, were tested with the Aphid, Amphorophora rubi (Kalt.), which is a vector of virus diseases of Rubus in Europe and N. America, to establish the range of resistance to the development of populations of the insect. The phenomenon of resistance was then further investigated from the aspect of fecundity, reproductive rate, length of life, growth rate and behaviour of the Aphid. In these latter investigations only four varieties of raspberry were employed. The varieties Malling Promise and Lloyd George showed no resistance. Malling Landmark proved to be highly resistant but showed a slight reduction in resistance in the autumn. Newburgh appeared to occupy an intermediate position between Malling Landmark and the other two varieties. There were indications, however, that under field conditions its degree of aphid resistance may be greater than was observed under experimental conditions. Resistance seems to involve a slowing down of the reproductive rate, a shortening of the length of life of adults and prevention of development of the nymphs. The practicability of using aphid-resistant varieties of raspberry to minimise virus spread is discussed.

STUDIES ON RUBUS VIRUS DISEASES IN BRITISH COLUMBIA: IV. TRANSMISSION OF RASPBERRY MOSAIC VIRUSES TO FRAGARIA VESCA L.

By means of the leaf-grafting technique, attempts were made to transmit the two component viruses of raspberry mosaic, rubus yellow-net, and black raspberry necrosis, separately and in combination, to three strains of Fragaria vesca L. Only the rubus yellow-net virus was transmitted to the strawberry and it induced severe symptoms. Neither the raspberry aphid, Amphorophora rubi Kalt., nor the strawberry aphid, Pentatrichopus fragaefolii (Ckll.), transmitted the yellow-net virus from raspberry to strawberry, although A. rubi was able to transmit the virus from strawberry back to raspberry.

STUDIES ON RUBUS VIRUS DISEASES IN BRITISH COLUMBIA: III. SEPARATION OF COMPONENTS OF RASPBERRY MOSAIC

It has been shown that the mosaic disease of red raspberry is the result of multiple infection by two separate viruses. Since these viruses, tubus yellow-net and black raspberry necrosis, have a common, vector, the aphid Amphorophora rubi Kalt., and are both nonpersistent, they are usually transmitted together and the complex nature of the mosaic disease can best be demonstrated by synthesis.

Observations on the North American Form of Amphorophora rubi Kalt. (Homoptera, Aphididae)

In 1937 Schwarze and Huber (3) reported the variety of Rubus idaeus L named “Lloyd George” to be totally resistant to the aphid Amphorophora rubi Kalt. This fact was of some economic significance because the aphid in question had been shown to be an active vector of Rubus viruses in North America. It was suggested that the aphid-resistant qualities of Lloyd George should be incorporated in plant-breeding programmes with a view to producing hybrids, with desirable commercial qualities, which would escape infection by the viruses.