bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency and geographical distribution of specific virulence factors in Bremia lactucae populations in England from 1973 to 1975
Authors: DIXON G. R. , WRIGHT I. R.
Published: February 2008

Samples of lettuces infected with Bremia lactucae were collected from seven areas of England during 1973‐5. These were tested under controlled environmental conditions on a range of differentially resistant cultivars to determine the frequency of virulence (V) factors in the pathogen population. In most cases the results could be accommodated by the relationship advanced by Crate & Johnson (1976). A virulence phenotype was determined for each isolate and individual virulences within isolates were identified as present at high or low frequencies. The most common V factors were V3, V4, V6 and V8 which reflected the resistance (R) factor complement of lettuce cultivars currently in commercial production. There were few gross differences in the geographical distribution of virulence factors between the seven areas. In the West Central region, however, which encompasses the Evesham and Lancashire production areas, results indicated that the use of cultivars containing resistance (R) factors 2 and 8 respectively would have provided protection from the disease during 1974. There were differences in virulence combinations at the holding or locality level within each large area, which could be exploited by growers providing testing was done in their particular locality.

Universally susceptible cultivars and those with only limited resistance factors were often found to be infected with B. lactucae populations which contained large numbers of V‐factors. It might have been expected that these pathogen populations would have been restricted to cultivars with large numbers of R‐factors. This finding conflicts with the suggestion that pathogen populations with complex virulence patterns are ‘unfit’ as compared with those with more simple virulence components.
The effect of sowing density and application of gibberellic acid on male sterility and ear emergence in ethephon‐treated field‐grown wheat
Authors: HUGHES W. G. , BODDEN J. J. , GALANOPOULOU STELLA
Published: February 2008

The induction of male sterility with ethephon and improvement in ear emergence with GA3 (1‐1 kg a.i./ha) applied 3 days later, was investigated in the winter wheat cv. Maris Nimrod sown in the field at72, 138 and 276 spaced plants/m2. Increased sowing density resulted in fewer surviving tillers per plant, a larger number of tillers per unit area and consequently a narrower range of stage of tiller development. This permitted a more accurate assessment of the correct time for ethephon application and resulted in a larger proportion of tillers responding to GA3 by having fully emerged ears. The most effective treatments for the production of emerged male sterile ears were 6‐4 and 12‐8 kg ethephon/ha applied to crops sown at the highest density.
The creation and management of wildfowl refuges as a means of lessening the conflict between farmers and geese
Authors: Owen Myrfyn
Published: February 2008

With increases in goose numbers and incidences of problems with other than traditionally damaging species on new crops conflict has greatly increased recently.

This paper suggested that the creation of managed goose refuges in problem areas provided the best long‐term solution. Examples of the success of refuges were given based on experience at two Wildfowl Trust goose refuges. Goose use of land surrounding these refuges had decreased following their creation and the goose carrying capacity of refuge land had been increased by up to 150% by controlling winter disturbance, cropping and stock grazing. This had been achieved without drastically changing the agricultural regime, which in both areas was in line with local practices.

Because of great annual fluctuations in goose numbers following variations in breeding success and of the difficulty of predicting goose carrying capacity, assessments of the area of land required to accommodate geese in conflict with agriculture in Britain can only be very approximate. Based on goose counts in 1975‐6, some 150000 geese (of four species) were potentially involved and the land area required as refuges to accommodate all of them (giving a maximum figure) in the region of 20 000 acres (7800 ha).
Red deer farming
Authors: Sharman G. A. M.
Published: February 2008

An experimental deer farm has been in operation on heather dominant upland in Kincardineshire since 1970 where the Rowett Research Institute and the Hill Farming Research Organisation have been exploring the possibility of intensifying venison production from such land. Six years' experience indicates that a tame foundation stock of red deer is a feasible basis for making good use of such land for the production of lean deer meat.
A method of inoculating young cocoa plants with basidiospores of Oncobasidium theobromae
Authors: PRIOR C.
Published: February 2008

A method is described for collecting basidiospores of Oncobasidium theobromae onto agar containing 35% w/v sucrose and preparing infective spore suspensions. When cocoa seedlings and clonal cuttings were inoculated, large differences in percentage infection were demonstrated between seedling progenies of resistant and susceptible trees. Resistant clonal cuttings were generally difficult to infect. The value of the technique for resistance screening is discussed.
Control of potato cyst nematode (Globodera rostochiensis) by nematicides and a resistant potato cultivar at four sites in Scotland
Authors: TRUDGILL D. L. , MACKINTOSH G. M. , OSBORNE P. , STEWART R. M.
Published: February 2008

The control of potato cyst nematode (Globodera rostochiensis) by the oxime‐carbamates aldicarb and oxamyl was tested in four fields in Scotland. Dazomet was tested in three of these fields and carbofuran in one. In untreated plots in the three most heavily infested fields Maris Piper (resistant) yielded better than Pentland Crown (non‐resistant). All nematicides increased the yields of both potato cultivars but had a greater effect on the yield of Pentland Crown. Dazomet increased yields of tubers most. Heavy nematode infestation reduced yield of tubers more in a sandy soil than in two sandy loams. In a field with few potato cyst nematodes nematicides did not significantly affect tuber yields.

Although the nematicides greatly increased yields, they were not completely effective in controlling potato cyst nematodes. In treated plots in the lightly infested field, there were more nematode eggs following a crop of Pentland Crown than before. In contrast, Maris Piper markedly decreased post‐cropping populations and except at one site, where dazomet further decreased nematode numbers, combining nematicides with the resistant cultivar failed to decrease nematode numbers further. Nematicides decreased the numbers of larvae invading potato roots by up to 95%, oxamyl at 5–6 kg/ha being consistently the best treatment.
Genetically determined variation in seed germination and field emergence of Brassica oleracea
Authors: HODGKIN T. , HEGARTY T. W.
Published: February 2008

The germination and field emergence levels and germination rates were measured of Brassica oleracea seed lots obtained by outcrossing the progenies of two half diallels to a single pollen parent. Analysis of variation of the seed lots classified according to their maternal grandparents showed that both general and specific combining abilities were important in accounting for the observed differences; the observed performance of many of the seed lots was satisfactorily accounted for by their grandmaternal parentage. The capacity to give high levels of germination was not necessarily related to the capacity to give high relative field emergence levels, maternal grandparents apparently differing in their ability to contribute to these two characters.
Distribution of photosynthate produced before and after anthesis in tall and semi‐dwarf winter wheat, as affected by nitrogen fertiliser
Authors: MAKUNGA O. H. D. , PEARMAN I. , THOMAS S. M. , THORNE G. N.
Published: February 2008

In 2 years the distribution of radioactivity recovered in entire shoots of field‐grown winter wheat was determined at various times after exposing the top two leaves (flag leaf or second leaf) to 14CO2 for 30 s. In 1976 when 14C was supplied to either leaf 14 days before anthesis, 30% was in the ear at anthesis. Less than 5% was in the leaf exposed to I4CO2. The remainder was equally divided between the stem above and below the flag‐leaf node when the flag leaf had been exposed, and was mainly in the lower part of the stem when the second leaf had been exposed. By maturity the proportion in the stem had decreased; 20% of the total activity was in the grain and 30% was still in the ear structures.

When 14C was supplied 10 days after anthesis, the proportion in the ear 24 h later ranged from 42 to 69% of that in the whole shoot when the flag leaf was exposed, and from 6 to 28% when the second leaf was exposed. At maturity these proportions increased to 92 and 85% when the 14C had been supplied to flag leaves and second leaves respectively. When 14C was supplied 25 days after anthesis to either flag leaves or second leaves, more than 90% of the activity was in the mature ears. Less than 5% of the 14C remaining at maturity from any treatment was still in the leaf exposed to 14CO2. Between 2 and 6% of 14C supplied after anthesis was in the non‐grain parts of the ear.

The proportion of the 14C in the ear was greatest for the semi‐dwarf varieties Maris Fundin and Hobbit, less for Maris Huntsman, and least for Cappelle‐Desprez. These varietal differences were large 24 h after exposure to 14CO2, especially in 1976. They were small and rarely significant at maturity.

Nitrogen fertiliser up to 210 kg N ha‐1 had negligible effects on the distribution of 14C, although it greatly increased growth and yield, especially in 1975.
Studies of Rhizobium meliloti isolated from salt‐affected soils
Authors: DOUKA CATHERINE E. , APOSTOLAKIS C. G. , SKARLOY V. D.
Published: February 2008

Rhizobium meliloti strains have been isolated from salt‐affected, non‐cultivated soils of Greece. The effectiveness of the isolates was investigated in test‐tubes using nitrogen‐free salts agar or soil. In the latter case a new simple and rapid technique was used during which plants of Medicago saliva were grown in large test‐tubes containing salt‐affected soil under controlled sterile conditions. Field trial measurements in salt‐affected soils indicate a good response to inoculation.
Effect of high soil temperatures on nodulation of cowpea, Vigna unguiculata
Authors: DAY J. M. , ROUGHLEY R. J. , EAGLESHAM A. R. J. , DYE M. , WHITE S. P.
Published: February 2008

Cowpeas, inoculated with one of five effective strains of Rhizobium isolated from African soils, were grown at root temperatures of 30 oC continuously or at 36, 38, 40, 42 and 44 oC for 5 h/day and returned to glasshouse ambient for the intermediate period. Growth was best at 30 and 36 oC; above 40 oC growth was poor and no nodules formed. At 40 oC two strains failed to nodulate. Symbiotic performance was not dependent only on nodule production as nodule efficiency varied inversely with temperature.

The number of nodules formed by strain R5000 after exposure of inoculated seed or seedlings to 40,42 or 44 oC for 5 h/day on each of 3 or 6 days depended on the age of plant and the duration of exposure to stress. When exposed to 42 or 44 oC during the first 3 days after sowing nodulation was reduced from 18 to 1–3 nodules/plant even after a further 40 days growth at ambient (30 day, 20 oC night). Nodulation was unaffected when 10–15‐day‐old seedlings were exposed to the same conditions.

Numbers of strain R5000 on seed declined rapidly following three daily exposures of 5 h at 39 and 42 oC; at 45 oC less than three bacteria survived on each seed. Other rhizobia of the cowpea group varied greatly in their toleration of high temperatures, some survived well at 45 oC whereas others behaved like R5000.
Observations on the morphs of Macrosiphum avenae and Metopolophium dirhodum on cereals during the summer and autumn
Authors: DEAN G. J.
Published: February 2008

From June to early August 1970, populations of Macrosiphum avenae and Metopolophium dirhodum on marked tillers of field barley were compared with the numbers of alatae trapped at crop height and at 12.2 m. There were always more M. dirhodum than M. avenae on the tillers. Only apterae were produced until mid‐June when both alatae and apterae occurred; after mid‐July only alate M. avenae were found. Until mid‐June most of the flying alatae were caught at 12.2 m as they migrated from spring hosts to cereals. Thereafter, more alate M. avenae were trapped at 12.2 m than at crop level, whereas numbers of alate M. dirhodum were usually comparable at both heights. Although crop and flying populations occasionally showed temporal similarities, insufficient is known about their field distribution and the factors affecting their alate production and flight activity to interpret this relationship.

In the autumn, two consecutive reproductive phases of M. dirhodum occurred on winter wheat grown in pots outdoors. Initially, apterous virginoparae and alatae, probably sexuparae, were produced, whereas only alate males appeared during the second phase. In contrast, M. avenae deposited mainly apterous virginoparae although some oviparae developed in October to lay scattered, probably infertile eggs on the tillers.
Factors influencing the prevalence of Pleospora bjoerlingii on sugar‐beet seed
Authors: BYFORD W. J.
Published: February 2008

Pleospora bjoerlingii was more prevalent on the seed of some sugar beet cultivars than others following both a dry seed harvest when infection was scarce and a wet harvest when superficial infection of seed was common. Methods of cultivation and harvesting that delayed ripening and increased the exposure of the seed to rainfall in a wet season increased the incidence of seed‐borne P. bjoerlingii but the incidence of the fungus on the seed of different cultivars was independent of the effect of cultivar on the time of ripening of the crop.
Interactions of Puccinia hordei and Erysiphe graminis on seedling barley
Authors: ROUND P. A. , WHEELER B. E. J.
Published: February 2008

The development of Puccinia hordei on the first leaf of barley seedlings previously inoculated with Erysiphe graminis was compared with that on uninoculated leaves of comparable age. On cv. Zephyr, more rust pustules developed when leaves were inoculated with both fungi within 24 h but fewer pustules if the period between the two inoculations was longer than 2 days. The reduction in numbers of rust pustules was especially marked where leaves were previously inoculated with many conidia of E. graminis. The size of rust pustules was reduced whatever the period between the two inoculations. Arresting mildew development by applying ethirimol as a soil drench to pots of seedlings inoculated with E. graminis 6 days previously, or floating segments of leaves inoculated with both fungi on 2% sucrose, in part counteracted these effects on rust pustule size. Similar effects were observed with cv. Mazurka where inoculations with E. graminis produced only small necrotic flecks but did induce premature loss of chlorophyll. On this cultivar (in contrast to Zephyr) the inoculation of one leaf surface affected the development of P. hordei on the other.

In comparable experiments using Zephyr, E. graminis produced smaller colonies with fewer conidiophores on leaves previously inoculated with P. hordei. These effects could be alleviated by arresting rust development with a spray containing benodanil or by floating segments of leaves inoculated with both fungi on 2% sucrose. Germination of the conidia of E. graminis, formation of appressoria and initiation of colonies were not affected by the presence of P. hordei.
Alteration of spermosphere ecosystems affecting oviposition by the bean seed fly and attack by soilborne fungi on germinating seeds
Authors: HARMAN G. E. , ECKENRODE C. J. , WEBB D. R.
Published: February 2008

In laboratory studies, treating ‘Butternut’ squash (Cucurbita pepo) seeds with ascospores of Chaetomium globosum NRRL 6296 and 6297 reduced oviposition by the bean seed fly Hylemya platura (Meigen), and reduced seed rot caused by Pythium ultimum and P. aphanidermatum. Treatment of seeds with thiram or captan increased oviposition by the bean seed fly. In the field, treatment of snap bean seeds with C. globosum NRRL 6296, or a commercial seed treatment mixture containing captan, diazinon, and streptomycin sulphate, resulted in significantly less damage by bean seed fly larvae than a treatment with thiram.
Effects of feeding position of the aphids Sitobion avenae and Metopolophium dirhodum on wheat yield and quality
Authors: WRATTEN S. D.
Published: February 2008

The effects of feeding site of Sitobion avenae and Metopolophium dirhodum on grain weight, number and nitrogen content were investigated in the laboratory and in the field. When the latter species was confined to particular leaves in a growth room, grain weight reductions occurred only when the aphid fed on the flag leaf; reductions in percentage grain protein, but not grain weight, followed lower leaf feeding. Leaves which had borne aphids had a higher proportion of nitrogen at death than control leaves, but this explained little of the shortfall in grain nitrogen, which was mainly due to direct removal during aphid feeding.

Multiple regressions of grain weight on aphid species/feeding site in the field confirmed the lack of grain weight effects when lower leaves were colonised; because grain size was greatly reduced by aphid feeding, percentage grain nitrogen increased with increasing aphid density in one cultivar and in others was unchanged. Successive comparison of control grain weights with those from tillers bearing an increasing range of aphid densities resulted in a significant reduction in weight with tillers bearing 21 to 25 aphid units on their ear and flag leaf combined, one unit comprising one adult or fourth‐instar aphid or three of earlier instars. These and other factors affecting the nature and extent of cereal aphid damage are discussed.
Sources and inheritance of resistance to halo‐blight of Phaseolus beans
Authors: TAYLOR J. D. , INNES N. L. , DUDLEY C. L. , GRIFFITHS W. A.
Published: February 2008

Forty‐three accessions of Phaseolus vulgaris and four of P. coccineus were classified on the basis of the reaction of their primary leaves and pods to inoculation with races 1 and 2 of the pathogen Pseudomonas phaseolicola. Four groups were recognised, (1) highly resistant to race 1 only, (2) resistant to both races, (3) slightly resistant to both races or (4) susceptible to both races. Race 1 resistance was present in a number of accessions (e.g. Red Mexican UI3, Rona, Cornell 42–242). Resistance to race 1 and 2 was present in PI 150414, GN Nebraska No. 1 sel. 27, OSU 10183 and other accessions with PI 150414 in their parentage.

Studies on the inheritance of resistance in Red Mexican UI3 and PI 150414 were made in crosses with various susceptible bean cultivars. A single dominant factor was responsible for race 1 resistance in Red Mexican UI3. The resistance factor in PI 150414 to races 1 and 2 behaved as a recessive in crosses with Cascade and Seafarer but was partially dominant in crosses with Gallatin 50. These findings suggest that genetic background can influence the expression of the resistance factor from PI 150414 and largely reconcile the conflicting evidence of previous investigators.
Resistance of the German cockroach (Blattella germanica) to bendiocarb
Authors: BARSON G. , McCHEYNE N. G.
Published: February 2008

Two field strains of the German cockroach Blattella germanica (L.) were collected in England from survivors of treatments with bendiocarb wettable powder, and bred in the laboratory. These and a laboratory susceptible strain were compared by a tarsal contact method to test for resistance to bendiocarb, fenitrothion and dieldrin. The field strains after exposure to the insecticide for 24 h were resistant to bendiocarb in terms of mortality by factors of 5.6 and 6.2 at the LC50 level, but at the LC95 level the resistance factors were only 1.7 and 2.0; however knockdown resistance was detected, with resistance factors at the KD50 level of 10.6 and 8.1. At shorter exposure times of 5 min and 60 min, 2–20% of cockroaches from the field strains survived 55 or 110 mg bendiocarb/m2; there were no survivors from the susceptible strain. Some cockroaches from the field strains were able to recover from knockdown after and during exposure to 110 mg bendiocarb/m2. Both field strains showed some resistance to dieldrin; however, there was no resistance to fenitrothion. When all three strains were exposed to 55 mg fenitrothion/m2 for 5 min, all the insects were knocked down within 3 h, and all had died within 96 h. There was no recovery from knockdown to fenitrothion or dieldrin.
Field control of sore shin (Rhizoctonia solani) of tobacco with benomyl and benodanil*
Authors: COLE DESIRÉE L. , COLE JAMES S.
Published: February 2008

Benomyl and benodanil, applied to tobacco seedlings before transplanting, reduced sore shin infection. Benodanil was the more effective, sometimes restricting damage to 5% of the surface area of the buried portion of stems, compared with 50–60% in untreated plants. The fungicides were applied either as a seedbed drench or a root‐stem dip. The dip method used less fungicide and was generally more effective than the drench at equal concentration but was less practical. Benodanil was over three times as active as benomyl against Rhizoctonia solani in liquid culture.
Competitive ability and ethirimol sensitivity in strains of barley powdery mildew
Authors: HOLLOMON D. W.
Published: February 2008

Strains within field populations of barley powdery mildew (Erysiphe graminis f. sp. hordei) varied greatly in their response to ethirimol. Each strain remained stable whether the fungicide was present or not, and no evidence for adaptation was obtained. Strains of intermediate sensitivity were the most frequent within the pathogen population, and these also dominated model populations maintained in the laboratory. Ethirimol eliminated sensitive strains from laboratory mixtures, and increased the relative fitness of insensitive ones, but not sufficiently to oust the intermediate strains. Mildew from treated field plots was less sensitive than that from untreated plots, but only early in the epidemic. Insensitivity was not related to the level of ethirimol used and, at four times the rate used commercially, insensitive strains were no more frequent than at lower rates. As the complexity of mildew populations increased, changes in ethirimol sensitivity in response to selection became less pronounced, and it is suggested that strains of intermediate sensitivity to ethirimol exert a stabilising effect within natural populations. This could alter if the fitness of insensitive strains were to increase, perhaps through recombination. Consideration should be given to the effect ethirimol might have on the composition of the pathogen population if applied when sexual recombination occurs, and to the role ascospores play in disease development.
Components of adult plant resistance to powdery mildew (Erysiphe graminis f. sp. avenae) in oats
Authors: JONES I. T.
Published: February 2008

The adult plant reaction to mildew (Erysiphe graminis f. sp. avenae) of four oat genotypes was studied. A negative relationship existed in these genotypes between length of latent period and the percentage leaf area with mildew. The very susceptible CI 4877 had the shortest latent period and the largest area of leaf infected, while the highly resistant Cc 4761 had the longest latent period and the least leaf area covered with mildew.

The same association also occurred between leaves within a genotype, particularly those genotypes with adult plant resistance, i.e., Maldwyn and Cc 4761. The more recently developed upper leaves showed the longest incubation period and least percentage area affected compared with lower leaves.

A visual score of pustule sporulation indicated that CI 4877, Milford and Maldwyn had similar well‐sporulating foci, but in Cc 4761 the pustules showed significantly less sporulation.

Estimates of the relative number of spores produced per day over a 15 day period reflected the level of resistance. Thus the most susceptible genotype CI 4877 released over 50 times more spores than Cc 4761, while Milford and Maldwyn respectively produced 9 and 4.5 times more spores than the highly resistant Cc 4761.

The longer latent period of Cc 4761 was reflected in the delay this genotype showed in reaching its relatively low peak production of spores.

The possible use of the latent period as a factor when selecting for adult plant resistance in early growth stages is discussed.
Effect of nitrogen deficiency on photosynthesis and the partitioning of 14C‐labelled leaf assimilate in unshaded and partially shaded plants of Lolium temulentum
Authors: POWELL C. E. , RYLE G. J. A.
Published: February 2008

The effect of a deficiency of applied nitrogen on the rate of leaf photosynthesis, and on the subsequent partitioning of 14C‐labelled leaf assimilate between new leaf, stem, tillers and root, was investigated in single plants of Lolium temulentum L., grown normally in controlled environments, or grown with collars shading the base of the plant. The nitrogen deficiency reduced the rate of leaf photosynthesis, increased the retention of assimilate in the leaf, suppressed the export of assimilate to tillers, and generally increased the export of assimilate to roots and to new leaves. Shading the base of the plant generally had little effect on the rate of leaf photosynthesis, reduced the export of assimilate to roots, and increased the export of assimilate to new leaf and to the stem, which elongated when shading was imposed.
Growth, reproductive development and yield of effectively nodulated cowpea plants in contrasting aerial environments
Authors: SUMMERFIELD R. J. , MINCHIN F. R. , STEWART KATRINE A. , NDUNGURU B. J.
Published: February 2008

Effectively nodulated cowpea plants were grown to reproductive maturity in growth cabinets set to simulate factorial combinations of daylength (11 h 40 min or 13 h 20 min), day temperature (27 or 33°C) and night temperature (19 or 24°C) characteristic of humid tropical environments. The experiment was designed specifically to compare and contrast the growth, reproductive ontogeny and seed yield of these plants with data obtained earlier when the same symbiotic combination (cv. K 2809 and Rhizobium CB 756) received large amounts (197 mg/l) of inorganic nitrogen throughout growth. These comparisons have shown that effectively nodulated plants are potentially no less adaptable to the aerial environment than are plants depending on inorganic nitrogen, whilst producing equally as good, or even better, seed yields.
Host range and properties of potato black ringspot virus
Authors: SALAZAR L. F. , HARRISON B. D.
Published: February 2008

Potato black ringspot virus (PBRV), obtained from cultivated potato in Peru, was found to have a very wide host range resembling that of tobacco ringspot virus (TRSV‐B), to which PBRV is distantly related serologically. However, PBRV caused the more severe symptoms in many species and, unlike TRSV B, infected Lycopersicon esculentum and Cyamopsis tetragonoloba. In Solanum tuberosum, PBRV caused necrotic spots and ringspots in systemically infected leaves in the year of infection and was readily transmitted through tubers to progeny plants, most of which developed no obvious symptoms although systemically infected. TRSV‐B infected non‐inoculated S. tuberosum leaves only sporadically, did not induce symptoms in them and was not transmitted through tubers to progeny plants.

PBRV was cultured in Nicotiana clevelandii and infectivity was assayed in Cheno‐podium amaranticolor or C. quinoa. Virus particles were purified from leaf extracts, after clarification using chloroform, by precipitation with 6% polyethylene glycol and differential centrifugation. Purified preparations contained 25 nm diameter isometric particles with somewhat angular outlines, sedimenting as three components (T, M and B) at 49, 84 and 117 S, and containing a single protein species of mol. wt 59 000. Preparations of PBRV nucleic acid contained two species, estimated by polyacrylamide gel electrophoresis in non‐denaturing conditions to have mol. wt of about 25 106 (RNA‐1) and 15 106 (RNA‐2). Infectivity was associated with B particles, preparations of which contained RNA‐1 and RNA‐2, presumably in different particles. M particles contained RNA‐2, were not infective and enhanced infectivity only slightly when added to B particles. Similar relative amounts of RNA‐1 and RNA‐2 were extracted from unfractionated virus using phenol or Pronase, but preparations obtained using phenol were much the more infective.

PBRV has properties typical of nepoviruses; its present cryptogram is (R/1):2–5/41 + 15/28 or 2 1 5/46:S/S:S/*, nepovirus group.
The relationship of potato black ringspot virus to tobacco ringspot and allied viruses
Authors: SALAZAR L. F. , HARRISON B. D.
Published: February 2008

The relationship between potato black ringspot virus (PBRV), isolates of tobacco ringspot virus from blueberry (TRSV‐B), cherry (TRSV‐C) and calico‐diseased potato (TRSV‐P), and eucharis mottle virus (EuMV) was examined in tests of three types. In gel‐diffusion precipitin tests, the reaction end‐points of antisera, and spur formation, indicated that PBRV and TRSV‐P are very closely related but not identical antigenically, as are TRSV‐B and TRSV‐C, and that these two pairs are more distantly related to each other and to EuMV. In plant‐protection tests in Nicotiana angustifolia, PBRV, TRSV‐B and EuMV conferred protection against the homologous virus but not against one another. PBRV, but not TRSV‐B, conferred protection against TRSV‐P. In tests with the two RNA species of PBRV, infectivity increased greatly when preparations of RNA‐1 and RNA‐2 were mixed, and both species are probably needed for infection. Infectivity did not increase when RNA‐1 or RNA‐2 of PBRV was mixed with RNA‐2 or RNA‐1, respectively, of TRSV‐B; the two viruses seem too distantly related to form pseudo‐recombinants.

It is concluded that PBRV and tobacco ringspot virus should be considered separate viruses, and that TRSV‐P should be considered a strain of PBRV. EuMV should perhaps be recognised as a virus distinct from, but related to, PBRV and tobacco ringspot virus.
Effects of root residues on growth ofPinus radiata seedlings and a mycorrhizal fungus
Authors: CHU‐CHOU MYRA
Published: February 2008

The height of Pinus radiata Don seedlings grown on soils incorporating different proportions of root tissues (25 and 50%) was shown to be reduced by 20–80%. Seedlings watered with aqueous extracts from soil/root mixtures also showed a significant reduction in growth. This growth‐retarding effect was partially overcome by the addition of nutrients or by soil sterilisation. It is postulated that growth retardation was caused not only by nutrient deficiency resulting from the addition of organic matter with a high C/N ratio, but also by phytotoxic substances present in the root tissue.

The effect of water extracts of roots from old P. radiata trees on the growth of young P. radiata seedlings and on a mycorrhizal fungus (Rhizopogon sp.) under aseptic conditions was also studied. Extracts from the inner bark of roots caused complete growth inhibition of the mycorrhizal fungus as well as root necrosis and wilting of P. radiata seedlings. A water‐soluble substance or substances, toxic both to the roots of P. radiata and to its mycorrhizal fungus, is postulated as the causal agent.
Survival and duration of development of Oscinella spp. (Diptera: Chloropidae) on different Gramineae in the laboratory
Authors: Vickerman G. P.
Published: February 2008

The duration of development and survival of Oscinella frit, O. nitidissima and O. nigerrima at different growth stages of several plant species was investigated in the laboratory. The effect of the infestation on the growth of plants was also quantified. Survival of O. frit larvae was significantly lower (P < 0.01) on barley than on either oats or wheat, between which there was no significant difference. Survival was usually highest when plants were infested at the two‐leaf stage and lowest when plants were infested at the five‐leaf stage. The duration of development of both male and female O. frit was longer on barley than on either oats or wheat and generally increased when older plants were infested. The proportion of male flies was greatest when older plants were infested. Duration of development and survival of O. frit was similar on oats and Lolium multiflorum, but larvae did not survive on Dactylis glomerata.

Of the other Oscinella species, O. nitidissima larvae did not survive on oats, wheat and barley and O. nigerrima larvae did not survive on either oats or barley.

The main shoots of cereal plants infested at the two‐, three‐ or four‐leaf stages were rapidly killed by O. frit larvae whereas many of those infested at the five‐leaf stage continued to grow slowly. In response to attack proportionately more tillers were produced by oat plants than by either wheat or barley plants.

When cereals were infested with O. nigerrima larvae the central shoots were damaged, but most recovered and continued to grow. Damage symptoms were most obvious when cereals were infested at the two‐leaf stage, oats being more severely affected than either wheat or barley.
Studies on virulence of the take‐all fungus, Gaeumannomyces graminis, with reference to methology
Authors: Deacom J. W. , Henry Christine M.
Published: February 2008

Current methods for take‐all assessment in laboratory experiment were examined; it was shown that the extent of vascular discoloration may not reflect virulence of a fungal isolate or host resistance to the pathogen under some experimental conditions. A new assessment method for take‐all is described, based on the ability of transport eosin past infection sites. It enables hosts or isolates to be compared by ET50 values, the times from inoculation when 50% of plants fail in eosin‐uptake through the three oldest seminal roots. Use of this technique suggested that barley roots were less affected than were wheat roots by Gaeumannomyces graminis var. tritici.

Further experimental results showed that an isolate of G. graminis that had lost part of its virulence in culture yielded some single‐conidium progeny more virulent than itself. When single‐condium isolates or a mycelial isolate and its single‐conidium progeny were jointly inoculated on wheat, the amount of disease was less than that caused by the more virulent isolate alone.
Host and environmental effects on the infection of maize by Puccinia sorghi. I. Prepenetration development and peneration
Authors: Mahindapala Ranjith
Published: February 2008

Germination of urediniospores of Puccinia sorghi on leafves and on ager was sminilar over the range 5–25°C, being greatest at 15°C, At this temperature, maximum germination was attained withing 5 h. Germination on cover slips started at around 99% r. h. and increased with of humidity.

Urediniospore germination was not affected by leaf age. In generalk, proportionally more spores germinated on the abaxial than on the adaxial surface. Maximum germination was observed on the abxial surface of the tip portion of the leaf.

The optimum temperature for infection structure formation was about 15°C, A munimum period of 3–4 h was required for the initiation of infection. Increase in appressorium and sub‐stomatal vesicle formation with increase in dew perio ws observed, with the maxima being attained at about 24 h after inculation.
Some effects of benomyl and carbendazim on Aphis fabae and Acyrthosiphon pisum on field bean (Vicia faba)
Authors: Bailiss K. W. , Partis G. A. , Hodgson C. J. , Stone E. V.
Published: February 2008

Field bean plants were treated with benomyl in a glasshouse, then nymphs of Aphis fabae and Acyrthosiphon pisum were caged on the second pinnate leaf. Soil drenches at concentrations of 150 and 75 μg benomyl/ml or above increased mortality of A. fabae and A. pisum respectively; 250 μg a.i./ml increased mortality and decreased progeny production of alate A. fabae. The effect on mortality persisted for at least 16 days after treatment. Foliar sprays increased mortality at concentrations of 75 μg a.i./ml and above (A. fabae). Field populations of A. pisum were reduced when bean plants were drenched or sprayed at a concentration of 250 μg a.i./ml and A. fabae populations were reduced by drenches but not by foliar sprays. A commercial formulation of carbendazim (Bavistin) increased aphid mortality whereas the formulation medium did not. Under the experimental conditions, benomyl affected the distribution of both species on young bean plants but did not induce a repellent effect; aphids preferred untreated leaves. Mortality and preference tests, and a field experiment, indicated that A. pisum was affected more than A. fabae.
Rearing and transmission techniques for Haplaxius sp. (Horn: Cixiidae), a suspected vector of lethal yellowing disease of coconuts
Authors: EDEN‐GREEN S. J.
Published: February 2008

Adult Haplaxius sp., identified from Jamaica as H. crudus or H. cocois, are common on coconut foliage in both Jamaica and Florida and are suspected vectors of lethal yellowing disease in both regions. Nymphs, which are subterranean, were mass‐reared on roots of the grasses Stenotaphrum secundatum, Axenopus compressus and Cynodon spp. Transmission of the disease was tested by feeding the nymphs on roots of diseased palms, rearing them on grasses and transferring the emergent adults to foliage of test palms for infection feeds. No transmission was proven.
Aphid‐injection experiments with carrot mottle virus and its helper virus, carrot red leaf
Authors: ELNAGAR S. , MURANT A. F.
Published: February 2008

Carrot mottle virus (CMotV) and its helper virus, carrot red leaf (CRLV), were not transmitted by aphids (Cavariella aegopodii) that had fed through membranes on, or had been injected with, sap from mixedly infected chervil plants or partially purified preparations of CMotV. However, the viruses were transmitted by recipient aphids injected with haemolymph from donor aphids that had fed on mixedly infected plants but not by a second series of recipients injected with haemolymph from the first series. Some of the first series of recipients transmitted both viruses for up to 11 days but others transmitted erratically and many lost ability to transmit after a few days. The results confirm that both viruses are circulative but provide no evidence for multiplication in the vector.

Non‐viruliferous aphids, or aphids that had acquired CRLV by feeding, did not transmit CMotV when they were injected with haemolymph from aphids that had fed on a source of CMotV alone, confirming that they can only transmit CMotV when they acquire it from a mixedly infected plant. When extracts from donor aphids were treated with ether before injection, recipient aphids transmitted both CRLV and CMotV, although the infectivity of CMotV grown in Nicotiana clevelandii in the absence of CRLV is destroyed by ether treatment. CMotV particles acquired by aphids from mixedly infected plants therefore differed in some way from those in singly infected plants. A plausible explanation of these results, and of the dependence of CMotV on CRLV for aphid transmission, is that doubly infected plants contain some particles that consist of CMotV nucleic acid coated with CRLV protein.
The influence of human and goshawk Accipiter gentilis activity on wood‐pigeons Columba palumbus at brassica feeding sites
Authors: KENWARD R. E.
Published: February 2008

Humans caused more than half the disturbance of wood‐pigeons, Columba palumbus, from roadside brassica feeding sites. The birds always flew away from pedestrians, cyclists and horsemen, but often remained feeding when closed vehicles passed. The pigeons resettled immediately on the same feeding site after 23% of goshawk, Accipiter gentilis, attacks, and birds were feeding there later the same day after nearly half the attacks. They resettled immediately after a similar proportion (19%) of the times they were approached by humans on foot, and rarely fed in fields where people were working.

The shorter the time pigeons had spent feeding before an interruption, the sooner they returned after it. This probably reflected the level of their crop food reserves. This behaviour should minimise the effect of short duration disturbance, as caused by goshawk attacks, on wood‐pigeons feeding at brassica sites. Goshawk attacks did not cause a reduction in pigeon pecking‐rate.

Pigeons feeding in roadside fields tended to avoid the side nearest to the road, but not parts of fields adjoining walls and hedges which could have provided cover for predatory attacks. It is concluded that scaring techniques based on man himself are more promising than use of the goshawk in protecting crops against wood‐pigeons.
Effects of foliar sprays of daminozide on the incidence of potato common scab
Authors: MCINTOSH A. H. , BATEMAN G. L.
Published: February 2008

Single foliar sprays of the growth retardant daminozide (1.5–12 g/l) approximately halved the incidence of common scab, caused by soil‐borne Streptomyces scabies, on potted potato plants in the glasshouse. Two analogues of daminozide (N‐dimethylaminomaleamic and N‐(dimethylamino)‐methylsuccinamic acids) also decreased scab, but others were inactive. Of 22 other unrelated growth regulators and translocated chemicals tested as foliar sprays, only gibberellic acid (0.1 g/l) decreased scab incidence, but many of the tubers were distorted. Chlormequat chloride and chlorphonium chloride, as root treatments, were inactive.

In other experiments with daminozide, scab incidence was decreased after application to soil. In tests with two plants per pot, spraying one of each pair decreased its rate of stem extension, but did not affect the other, indicating that little or no daminozide passed into the soil from the roots of the sprayed plant. The decrease in scab brought about by foliar sprays was not altered by varying their timing during the period before symptom development (1 to 5 wk after potting). In agar plate tests, daminozide was only weakly toxic to S. scabies.

It is concluded that daminozide probably decreased scab by altering the physiology of the plants, so that scab symptoms did not develop.
Further studies on the effect of resistance to Amphorophora idaei in raspberry (Rubus idaeus) on the spread of aphid‐borne viruses
Authors: JONES A. T.
Published: February 2008

The rate of spread of viruses transmitted by the aphid Amphorophora idaei into genotypes of raspberry differing in resistance to infestation by A. idaei was studied in a field experiment which exposed plants to large numbers of infective aphids. Under these conditions, genotypes that are readily colonised by A. idaei were totally infected with virus after two to three growing seasons, whereas genotypes with a high degree of resistance were substantially free of virus after four growing seasons but 56% of plants were infected after seven seasons. Genotypes with intermediate resistance were also substantially free of virus after three seasons but 76% of plants were virus infected after seven seasons.

The effectiveness of resistance to A. idaei in raspberry in restricting spread of viruses transmitted by this aphid is discussed.
Leaf photosynthesis in pure swards of two grasses (Lolium perenne and Lolium multiflorum) subjected to contrasting intensities of defoliation
Authors: OLLERENSHAW J. H. , INCOLL L. D.
Published: February 2008

Photosynthetic rates were measured on light saturated, fully‐expanded leaves in pure swards of Lolium perenne and Lolium multiflorum during late summer using 14‐carbon dioxide. These swards were defoliated by cutting at three heights of 3, 6 and 9 cm above the ground. The photosynthetic rates of leaves on tillers in swards cut constantly 3 cm above ground level were higher than those of leaves in swards cut constantly 9 cm above ground level. Additional treatments with various sequences of cuts 3, 6 and 9 cm above ground level were designed to reduce damage to the growing points of tillers whilst ensuring satisfactory harvesting of the shoots. The photosynthetic rates of leaves on tillers cut to various heights above ground level at successive harvests were intermediate between those of similar leaves in the constantly low and high cut swards.

The rates of photosynthesis of Italian ryegrass leaves were higher than those of perennial ryegrass leaves for a short time after defoliation of the constantly high cut swards. However, these perennial ryegrass leaves quickly adapted their rates of photosynthesis to the higher irradiances they received after cutting. Thus grass species differing in morphology adjust to management practices by the use of different photosynthetic strategies.
Populations of the phorid fly Megaselia halterata on an experimental mushroom unit over four years
Authors: BINNS E. S. , GURNEY BARBARA , WYATT I. J. , WHITE P. F.
Published: February 2008

Populations of phorid flies on an experimental mushroom unit were sampled simultaneously in both spawn‐running and mushroom cropping‐houses by sticky traps. Comparison between these populations showed that each reached a maximum about August and that the rate of increase, as measured by the ratio between them, varied from 22 × (at the beginning of February and in mid‐August to 115 × (at the beginning of June and the end of December). Population growth within a crop was assessed from the peaks plotted from weekly catches. Three such peaks could be seen, starting from initial numbers which were high, on average, at casing but with little increase after the seventh week of cropping. However, population growth within crops, found by pooling data for different seasons, showed logistic increases though slopes varied from low, for May to June‐spawned crops, to high for October spawning. Wide variations occurred in the proportion of the total flies represented in the initial catches in the first wk after casing.

Partial regressions were examined for the numbers caught in cropping‐houses on those taken in spawn‐running rooms throughout the year. Catches for crops spawned during June to September gave lower slopes for high cropping‐house populations. Spawn‐running room catches showed a linear relation with outdoor 9.00 a.m. B.S.T. temperature and cropping‐house numbers a logistic relation, a better fit obtaining with temperatures at spawning rather than 5 wk later during cropping. Catches during spawn‐running were correlated with those during subsequent cropping and these with catches made during the previous crop on the unit, irrespective of site. Since it was bimodal, rate of increase between spawn‐running and cropping‐houses did not correlate with outdoor temperature but revealed some very high catches in winter. Many flies were trapped in the cropping‐houses early in the year when flies were absent from spawn‐running rooms. Evidence for movements within farms is discussed, especially with respect to overwintering of the phorid, which validates routine trapping of both populations.