bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of eyespot on the yield of winter wheat
Authors: SCOTT P. R. , HOLLINS T. W.
Published: February 2008

For 4 successive years, cultivars of winter wheat differing in resistance to eyespot (Cercosporella herpotrichoides) and to lodging were grown in plots in which different levels of eyespot were induced by inoculating at different times. Lodging was either allowed, or prevented by growing the plants through nets. Yield losses were greatest in the most severely infected plots in which lodging was allowed; losses were reduced where infection was less severe or where lodging was prevented. In the year in which eyespot was most severe, there was a significant regression of yield on disease severity, even for the plots in which lodging was prevented; where lodging was allowed, regression lines were steeper for the lodging susceptible cultivars, but did not differ for the lodging resistant cultivars. Eyespot reduced the number of tillers, measured in spring, but later there was partial compensation for these losses. Grain number per ear and 1000 grain weight of individual tillers were reduced by severe eyespot infection; moderate infection reduced only 1000 grain weight; slight infection caused no reduction. Tillers without severe infection produced extra grains in severely diseased plots, so that there was no overall effect of eyespot on grain number per ear. The results are discussed in relation to the breeding of dwarf cultivars, which may be highly resistant to lodging but can nevertheless suffer severe losses from eyespot.
Effects of mildew on the growth and yield of spring barley: 1969‐72
Authors: JENKYN J. F.
Published: February 2008

Mildew decreased grain yield by decreasing ear number and grain size (but not grain number/ear), the damage depending on the earliness and severity of mildew. In 1971 when mildew was early and severe, ethirimol seed dressings at 0.22 kg a.i./ha, which gave only early protection, increased yield more than did ethirimol sprays applied to protect the flag leaf and ear. In 1972 sprays were better than seed dressings at this rate because mildew was less severe during the seedling stages.
Growth inhibitors in roots of light‐ and dark‐grown seedlings of Zea mays
Authors: WILKINS H. , BURDEN R. S. , WAIN R. L.
Published: February 2008

Abscisic acid and 6‐methoxy‐2‐benzoxazolinone have been identified as growth‐inhibitory compounds in the primary roots of Zea mays.
Damage caused by the Green Spruce Aphid to Norway and Sitka spruce needles
Authors: PARRY W. H.
Published: February 2008

Three‐month‐old needles of Sitka spruce were less susceptible to Elatobium abietinutn than 15‐month‐old needles. Symptoms appeared after longer aphid feeding times but only a proportion of damaged needles fell. After short feeding periods symptoms appeared in more Norway spruce needles than in Sitka spruce, whereas longer feeding periods resulted in more needles producing symptoms in the Sitka spruce. The symptoms took 4—6 days longer to appear in Norway spruce, and needle fall followed a longer feeding period than on Sitka spruce. Following 72 h feeding, needle fall occurred more quickly on Sitka spruce than on Norway spruce. The time taken for needle fall to occur was inversely related to the feeding time in Sitka spruce but such a response was not evident in Norway spruce. The results are discussed in relation to the differences exhibited in the probing behaviour of the aphid on the two spruces.
Breeding for resistance to the white potato cyst‐nematode, Heterodera pallida
Authors: FULLER J. M. , HOWARD H. W.
Published: February 2008

Progenies bred from material derived from the wild potato, Solanum vernei and from the cultivated potato, S. tuberosum ssp. andigena, clone CPC 2775, were compared for their resistance to Heterodera pallida, pathotype E. The influence of additional resistance derived from the wild species, S. multidissectum, was also investigated.

Both S. vernei and CPC 2775 gave progenies with variable levels of resistance and there was often no clear segregation into resistant and susceptible categories. Incorporation of gene H2 derived from S. multidissectum increased resistance to pathotype E of H. pallida for resistant material bred from both S. vernei and clone CPC 2775. The results indicate that adequate resistance to all British populations of potato cyst‐nematodes can best be obtained by combining the factors for resistance from the two Andigena clones, CPC 1673 (gene H1) and CPC 2775 (gene H3), and from S. multidissectum (gene H2).
Tests for resistance to Aphis fabae in field beans (Viciafaba)
Authors: BOND D. A. , LOWE H. J. B.
Published: February 2008

Two lines of Viciafaba were as resistant to Aphis fabae as Rastatt, one of their progenitors, when compared with susceptible control varieties in glasshouse experiments. In short experiments, fewer adult aphids settled on plants of resistant varieties, which subsequently bore smaller total numbers of aphids. In a longer experiment, the aphids multiplied more slowly on the resistant varieties, which survived after susceptible beans had been killed.

The bean varieties did not vary in numbers of aphids on the stem or growing point but resistant varieties had markedly smaller proportions of the total on the abaxial surface of the leaves; in particular the smaller veins supported fewer aphids. V. narbonensis was very resistant to A. fabae but was susceptible to Myzus persicae, indicating that its resistance mechanism is distinct from that within V. faba.

In infested field trials most of the variation in yield of bean varieties was attributable to the size of A. fabae colonies, and resistant varieties outyielded susceptible varieties. Yields of resistant varieties in the presence of large numbers of aphids were, however, less than those from trials without aphids. In uninfested trials susceptible varieties usually gave the largest yields.

The significance of these observations is discussed in relation to policies and methods for breeding for resistance to A. fabae in V. faba.
Control of Verticillium wilt transmission in strawberry runners with systemic benzimidazole‐type fungicides
Authors: JORDAN V. W. L.
Published: February 2008

Pre‐planting root dips and soil drenches with benomyl, carbendazim (MBC), thiabendazole and thiophanate‐methyl were used to reduce disease severity in mother plants. Transmission of the pathogen Verticillium dahliae through stolons and into young runners was prevented by two applications of benomyl or thiophanate‐methyl at o‐i% active ingredient applied at stolon appearance and 1 month later. Sufficient concentrations of fungistatic residues were detected in all plant tissues to suppress the internal spread of the pathogen.
The significance of ethylene in the ripening of stored apples
Authors: Knee M.
Published: February 2008

Ethylene is ignored in commercial apple storage on the assumption that it does not cause ripening below 7 oC. If substantiated, this would affect ideas of ethylene action, but further investigation shows that ethylene hastens cell wall changes associated with softening in apples stored at 3–5 oC. Modified atmospheres influence these processes through effects on ethylene synthesis and action. Pigment changes are less affected by ethylene and may be more directly influenced by atmospheric composition.
Ethylene as a factor limiting the legume‐Rhizobium symbiosis in tube culture
Authors: Day J. , Dart P. , Roughley R.
Published: February 2008

Growth and nitrogen fixation by Trifolium subterraneum plants at 15 and 10 oC root temperatures is much less in test tubes plugged with cotton wool than in open pots of sand. Removing the ethylene produced by plants growing in cotton wool plugged flasks by adsorption onto activated charcoal, or by aerating with sterile air, increased nitrogenase activity and growth over the first 25 days, to levels approaching that of plants grown in open pots of sand.
Insect pollination of sugar‐beet (Beta vulgaris) seed crops
Authors: FREE J. B. , WILLIAMS INGRID H. , LONGDEN P. C. , JOHNSON M. G.
Published: February 2008

The flowers of sugar‐beet crops grown to produce hybrid seed were visited by many species of insects which often carried much sugar‐beet pollen on their bodies and could have contributed to pollination.
Observations and experiments on the use of an avirulent mutant strain of tobacco mosaic virus as a means of controlling tomato mosaic
Authors: FLETCHER J. T. , ROWE J. M.
Published: February 2008

In 1973 tobacco mosaic virus (TMV) strain M II‐16 was successfully used by growers in the United Kingdom to protect commercial tomato crops against the severe effects of naturally occurring strains of TMV. However, plants in many crops had mosaic leaf symptoms which were occasionally severe, so possible reasons for symptom appearance were examined. The concentration of the mutant strain in commercially produced inocula (assessed by infectivity and spectrophotometry) ranged from 28 to 1220 μg virus/ml; nevertheless all samples contained sufficient virus to infect a high percentage of inoculated tomato seedlings. Increasing the distance between the plants and the spray gun used for inoculation from 5 to 15 cm resulted in a significant decrease in the number of tomato seedlings infected. When M II‐16 infected tomato plants were subsequently inoculated with each of fifty‐three different isolates of TMV, none showed severe symptoms of the challenging isolates within 4 wk, although some isolates of strain o induced atypically mild leaf symptoms. In a further experiment, M II‐16 infected plants showed conspicuous leaf symptoms only 7 wk after inoculation with a virulent TMV isolate. M II‐16 multiplied more slowly in tomato plants and had a lower specific infectivity than a naturally occurring strain of TMV. More than 50% of plants in crops inoculated with strain M II‐16 which subsequently showed conspicuous leaf mosaic contained TMV strain 1 or a form intermediate between strains o and 1. It is suggested that the production of TMV symptoms in commercial crops previously inoculated with strain M II‐16 may result from an initially low level of infection, due to inefficient inoculation, which allows subsequent infection of unprotected plants by virulent strains. Incomplete protection by strain M II‐16 against all naturally occurring strains may also be an important factor.
The distribution of pathotypes of the cereal cyst‐eelworm Heterodera avenae in England and Wales
Authors: SAYNOR M.
Published: February 2008

Two pathotypes of the cereal cyst‐eelworm (Heterodera avenae), occurred commonly in England and Wales and a third pathotype was apparently present in low numbers in a few areas. Pathotype 1, which can breed on most cultivars of wheat, barley and oats, but not on Drost barley nor barley cultivars containing the gene for resistance from barley No. 191, was most common in the south west of England. Pathotype 2, which can breed on most cereals, including Drost barley but not No. 191, was common throughout England and Wales and mixtures of these pathotypes occurred in many places. Pathotype 3, which can breed on barley No. 191 and probably on Drost and most cultivars of cereals, was rare and was found only in low numbers together with either or both Pathotypes 1 and 2. In the initial tests it was present or suspected in only nine fields (6%), but when these soils were retested in more detail the following year, Pathotype 3 was confirmed at only one site.
Effects of chloromequat chloride on related tall and dwarf rice varieties
Authors: GANASHAN P. , WHITTINGTON W. J.
Published: February 2008

The effects in growth room experiments of three levels of 2‐chloroethyltrimethylammonium chloride (chloromequat chloride; CCC) at two nitrogen levels were studied on a tall rice variety and a mutant dwarf derivative. CCC was found to reduce plant height in both varieties, to increase tiller number and spikelet number on the main panicle or in total but to delay flowering. Chemical dwarfing cannot be regarded as an alternative to genetic dwarfing since mutants may be shorter than chemically treated tall genotypes and may themselves respond favourably to further treatment.
Effect of pre‐harvest fungicides on the spoilage of soft fruit after harvest
Authors: DENNIS C.
Published: February 2008

In the 1972 season, Elvaron and Benlate reduced the count of Botrytis cinerea, Cladosporium spp., Penicillium spp. and Aureobasidiutn pullulans on strawberry and raspberry fruits during the first 2 wk of the season, but not subsequently. No such reduction was recorded for Hainesia lythri (strawberries only), Phoma state of Didymella applanata (raspberries only), Mucor spp., and Rhizopus spp. Similar results were obtained in 1973.

In the first half of either season, both fungicides decreased the rate of fungal spoilage of stored fruit (except for Benlate in the 1973 season), although in the latter part of the season, there was little difference in the incidence of fungal spoilage between sprayed and unsprayed fruit. Both fungicides, however, reduced the development of B. cinerea (and Cladosporium spp. on raspberries) on stored fruit irrespective of season or harvest date except for Benlate in the 1973 season where Benlate‐resistant strains of the fungi developed on the fruit. The failure of either fungicide to reduce fungal spoilage in the latter part of the harvesting season was due to the development of Phycomycetes, particularly Mucor mucedo and to a lesser extent Rhizopus stolonifer and R. sexualis, except where Benlate‐resistant strains of B. cinerea and Cladosporium spp. were present.
Future virus problems?
Authors: Plumb R. T.
Published: February 2008

Of seventeen viruses that infect British grasses several have been reported only recently; others that occur in Europe have hosts and vectors in Britain and could become a problem. Ryegrass bacilliform virus and ryegrass spherical virus are described and maize dwarf mosaic virus, maize rough dwarf virus and brome mosaic virus are considered as possible pathogens.
Resistance of red and white clover cultivars to clover rot (Sclerotinla trifoliorum)
Authors: Dixon G. R.
Published: February 2008

Various techniques for assessing the resistance of clover cultivars to clover rot have been investigated, including counting sclerotia around infected plants, measuring lengths of healthy and diseased rows and the use of a key to assess symptom expression on individual plants. The latter was found to be the most suitable under field conditions. Of fifty‐one red clover cultivars tested, nineteen were found to possess some level of resistance. Clover rot appears to be an increasing problem with white clover crops but tests have indicated that resistant cultivars are available.
The distribution and analysis of cabbage root fly egg populations
Authors: FINCH S. , SKINNER G. , FREEMAN G. H.
Published: February 2008

The distribution of the egg stage of the cabbage root fly around brassica plants was studied at Wellesbourne on 0.05–0.4 ha plots during 1970 and 1971.

The three generations of flies occurred at similar times in both years and the numbers of eggs collected generally decreased from the first to the third generation. Differences between generations demonstrated that each generation should be treated separately. The number of plant samples required for a given level of precision increased from the first to the third generation, indicating that experiments relying on egg counts should be planned to coincide with the first generation whenever possible. A sampling plan for the range of oviposition normally encountered during the three generations is illustrated for both one‐ and five‐plant samples. For the same level of precision, estimates of the populations from five‐plant samples required only 50% to 80% of the time of those from one‐plant samples. When aestivation occurs the peak of oviposition in the second generation is difficult to determine, and designed experiments should not be undertaken. The negative binomial distribution failed to describe the clumping of the eggs for a complete generation, since a common k could not be fitted to the data. The distribution of the eggs was best described by Taylor's power law which showed that although sampling factors changed with generation, the value of the power did not. A value of 1.4 appears to be the index of aggregation characteristic of the egg stage of this species.
Leaf growth, stomatal diffusion resistances and photosynthesis during droughting of Lolium perenne populations selected for contrasting stomatal length and frequency
Authors: WILSON D.
Published: February 2008

Lolium perenne selection lines with high calculated stomatal resistances to diffusion (rs) as a result of either few or short stomata, maintained leaf extension rates and photosynthetic rates longer than selection lines with low resistances when deprived of water. There were no significant differences between high and low rs plants in light saturated CO2 uptake of turgid attached leaves.

When grown in soil drying to 21% moisture, plants with low calculated rs exhibited lower minimum leaf resistances (rl) than those with high, measured with a diffusion porometer, on all except the last day. The daily maximum rl (1.5 h after the start of the light period) became greater among low than high rs plants as the difference in rate of leaf extension between the two groups of plants increased with drying soil. Rate of leaf extension was negatively correlated with daily maximum rl and started to decline when relative leaf water content (RLWC), at 5 h after the start of the light period, fell below about 88%. Transpiration rate of plants grown in different soil moisture regimes was correlated (r=+ 0.83, P < 0.01) with mean maximum adaxial leaf conductance (reciprocal of resistance). There was a highly significant correlation (r=+ 0.62, P < 0.01) between calculated adaxial rs and mean minimum measured rl among plants growing at high or intermediate soil moisture, but not at low. Therefore, some random variation in minimum rl, even with adequate moisture, seemed to be unaccounted for by variation in stomatal numbers or size. Selection for increased numbers of adaxial stomata also resulted in more on the abaxial surface, but mean adaxial/abaxial ratio in the ‘frequent’ stomata plants was still only about 9:1.
The fungal flora of soft fruits in relation to storage and spoilage
Authors: DENNIS C. , MOUNTFORD JUNE
Published: February 2008

The fungal population of freshly harvested strawberries, raspberries and blackberries was studied throughout the fruiting seasons and the relative importance of fungi responsible for spoilage of stored fruit from different harvest dates was assessed.

Botrytis cinerea, Cladosporium spp., Penicillium spp., Aureobasidium pullulans and Mucor spp. were consistently present on all three fruits while Colletotrichum gloeosporioides and Didymella applanata were prevalent on raspberries only and Epicoccum purpurascens and Alternaria spp. on blackberries only.

Botrytis cinerea and Mucor mucedo were the predominant spoilage organisms of all three fruits, although the relative importance of the two fungi changed as the season progressed, especially for strawberries. Rhizopus stolonifer, Cladosporium spp., Penicillium spp. and Colletotrichum gloeosporioides were only of minor importance as spoilage organisms.
The role of Thielaviopsis basicola in the specific replant disorders of cherry and plum
Authors: SEWELL G. W. F. , WILSON J. F.
Published: February 2008

The hypothesis that Thielaviopsis basicola might be the causal agent of the specific replant disorders of cherry and plum was tested in experiments with pot‐grown trees and by observations on the distribution of the pathogen. The results obtained with certain strains of T. basicola simulated and were consistent with all features known to characterize the specific replant disorders, viz. inter‐ and intra‐generic specificity of effect; host symptoms; establishment, immobility and persistence of the causal agent in soil; normal growth of affected trees after transfer to ‘non‐replant’ soil; limited influence of soil type on the incidence of the disorder. T. basicola was therefore considered to be the probable causal agent of the specific replant diseases of certain Prunus species. The etiology of these diseases is discussed.

T. basicola was neither pathogenic to apple nor associated with the growth of apple. The apparently closely similar specific replant disorder of Malus is therefore considered to be causally distinct from those of cherry and plum.
Soil populations of Thielaviopsis basicola associated with cherry rootstocks in relation to effects of the pathogen on their growth
Authors: PEPIN H. S. , SEWELL G. W. F. , WILSON J. F.
Published: February 2008

Large differences were found between populations of Thielaviopsis basicola in soils from nursery layer‐beds of different cherry rootsock clones. The soils were classified primarily into those with small (< 700 propagules/g) and those with large (3600–45000 propagules/g) populations, although significant differences occurred between soil populations in the latter group. Clones associated with small soil populations (Prunus pseudocerasus, and P. avium×P. pseudocerasus hybrids) were highly resistant to T. basicola root rot; clones associated with large soil populations (selections and intraspecific crosses of P. avium, and hybrids of P. avium × P. incisa) were susceptible. The results indicated that severe pathogenesis was associated with varying levels of parasitism in different clones, but not that extensive parasitism of cherry species occurred without pathogenesis.

Resistance to T. basicola in the P. pseudocerasus hybrids is an important asset to these potential cherry rootsocks.
Bacilliform particles associated with vein yellowing of Laburnum anagyroides
Authors: SCHULTZ M. G. , HARRAP K. A.
Published: February 2008

Bacilliform particles characteristic of plant rhabdoviruses were found in negatively‐stained leaf sap and in thin sections of Laburnum anagyroides in England showing vein yellowing. The particles were detected principally in the perinuclear space of parenchyma cells. They were not transmitted by sap inoculation to twelve herbaceous species. The affected trees also showed mosaic symptoms but there was no evidence of an association between these and the bacilliform particles.
Laboratory methods for studying non‐preference resistance to cabbage root fly in cruciferous crops
Authors: ELLIS P. R. , HARDMAN J. A.
Published: February 2008

A laboratory method for testing cruciferous plants for their non‐preference resistance to cabbage root fly is described. Test plants were fully randomized on a turntable inside a large chamber containing cabbage root flies. The apparatus was housed in a controlled environment room. The root‐fly eggs, laid in the sand surrounding test plants, were extracted using a flask flotation method which was quicker and more efficient than the stirring technique which it superseded. Two batches of plants were tested alternately, one being exposed to the flies, while the other was sampled for eggs. Each batch of test plants received three 1‐day exposures to egg‐laying, their positions within the test chamber being changed for each exposure to ensure complete randomization.

This test method gave highly consistent results and indicated that there were differences in the flies' preference both between cultivars of radish and cauliflower and for individual plants within cultivars. Plants representing the extremes of preferences discovered in the two crops were saved for further study.

It was not possible to correlate seed weight, time of seedling emergence, foliage surface area, or hypocotyl attitude in relation to soil level, with the egg‐laying preference of the cabbage root flies.
Further properties of black raspberry latent virus, and evidence for its relationship to tobacco streak virus
Authors: JONES A. T. , MAYO M. A.
Published: February 2008

Purified preparations of an isolate of black raspberry latent virus (BRLV) contained quasispherical particles with a mean diameter of 28·5 nm; these particles were resolved into three sedimenting components (s20, w= 82S, 95S and 104S), but when centrifuged to equilibrium in caesium chloride solution they formed a single infective band (σ= 1·35 g/cm3). During electrophoresis in polyacrylamide gels, virus particles separated into three classes, and virus RNA was resolved into three major (mol. wt 1·35, 1·10 and 0·85 × 106) and one minor (mol. wt 0·4 × 106) component. The protein from virus particles had an estimated mol. wt of 28000. Isolates of BRLV were found to be serologically related but not identical to some strains of tobacco streak virus.

No symptoms developed in black raspberry seedlings infected with BRLV by mechanical inoculation, nor in eight red raspberry cultivars infected by graft inoculation. However, graft inoculation of BRLV to Rubus henryi, R. phoenicolasius and Himalaya blackberry induced symptoms typical of necrotic shock disease.
Some effects of the growth‐retardant glyphosine [N, N‐bis (phosphonomethyl) glycine] on the sugar‐beet crop
Authors: JAGGARD K. W.
Published: February 2008

Four experiments tested a range of doses of the growth‐retardant glyphosine on sugar‐beet crops between 1970 and 1972. The period of time between application and harvest was varied. One experiment (1972) in nutrient mist culture examined its effect on seedling root development.

The growth‐retardant decreased root, sugar and top yield of sugar beet at all doses in excess of 0·56 kg a.i. ha‐1 at all treatment times. It increased the α‐amino nitrogen content of beet roots significantly (P < 0·05) with doses in excess of 1·12 kg a.i. ha‐1. When applied to the leaves of seedlings with their roots in nutrient mist culture, glyphosine at 500 ppm and 2000 ppm of a.i. in aqueous solution slowed or stopped root elongation.
Bolting in some carrot populations
Authors: DOWKER B. D. , JACKSON J. C.
Published: February 2008

Genetic differences in bolting resistance between types, between varieties within types and within varieties were demonstrated in some Chantenay and Autumn King carrots and populations derived from crosses between them. The Chantenay type gave a higher proportion of bolters than the Autumn King type. Effects of sowing date and plant density on bolting were also demonstrated, later sowing and higher densities giving lower proportions of bolters. Genotype‐environment interactions were found and the responsiveness of the varieties to environment characterized by linear regression coefficients derived from a joint regression analysis. The most responsive variety tested was Red Cored Chantenay and the least responsive Rialto Improved. Implications of these findings for the breeding of new varieties with earlier harvest periods, and also for the seed multiplication of existing varieties are discussed.
The effect of vesicular arbuscular mycorrhizal associations on growth of cereals
Authors: KHAN A. G.
Published: February 2008

The growth of wheat seedlings which were already mycorrhizal when transplanted to a field deficient in phosphorus was improved compared with non‐mycorrhizal controls, and grain yield was increased three‐fold by the fungus, indicating that Endogone stimulated growth and increased yield. Differences between mycorrhizal and non‐mycorrhizal wheat were eliminated by the application of phosphate fertilizer, indicating that the fungus does not enhance wheat growth in soils containing enough available phosphate. It is probable that the mycorrhizal effect is primarily to improve the supply of phosphate. There were clear relationships between spore number in the soil and mycorrhizal development and between the extent of root infection and increased growth. The extent of root infection was greatest in mycorrhizal plants in soil not supplemented with phosphate and it decreased in inoculated plants in the plot supplemented with superphosphate.

The non‐centrospermous and non‐zygophyllaceous weeds growing on the experimental field had typical vesicular arbuscular infection and indigenous Endogone spores in their rhizospheres. The centrospermous plants were non‐mycorrhizal and had no Endogone spores in their rhizospheres.
Effects of varying air and soil moisture on the water relations and growth of sugar beet
Authors: MILFORD G. F. J. , LAWLOR D. W.
Published: February 2008

Sugar beet were grown for short periods with different amounts of moisture in the soil and air. Growing plants in wet soil (23 % moisture on dry weight) compared with dry soil (15% moisture) increased growth of the shoots and roots and plant dry weights by 15% in young plants and 10% in mature plants. Growing plants in wet air containing 10.9 g m‐3 of water (equivalent to a saturation deficit of 2.5 mb) compared with dry air containing 6.4 g m‐3 of water (saturation deficit = 8.5 mb) increased the dry weights of both young and mature plants by 8%, mostly by increasing the sizes of their storage roots. Wet air and wet soil increased the net assimilation rates of both young and mature plants. Wet soil, but not wet air, increased leaf areas of young plants by accelerating leaf expansion, and both increased the leaf area of mature plants by slowing senescence of the older leaves. Wet soil increased the water potential of the leaves of both young and mature plants and, by doing so, increased their stomatal conductances and rates of photosynthesis. Wet air also increased stomatal conductances and rates of photosynthesis of leaves of plants of both ages, but without changing their water potentials. Stomatal conductances and photosynthetic rates were greater for young leaves than mature on the same plant and at the same water potential. It is suggested that at certain stages in the crops growth photosynthetic efficiency could be increased by applying additional water as a mist to increase the moisture content of the air around the crop.
The effects of predators on the eggs of codling moth Cydia pomonella, in a cider‐apple orchard in south‐west England
Authors: Glen D. M.
Published: February 2008

In a 2‐yr study, predators were shown to inflict heavy mortality on the eggs of codling moth, Cydia pomonella, placed in a cider‐apple orchard where no insecticidal sprays were applied. Predatory Heteroptera sucked out 35 and 57 % of the eggs in the 2 yr respectively, and smaller numbers of eggs (16 %) disappeared, probably consumed by earwigs, Forficula auricularia. The potential of these predators for an integrated control system is briefly discussed.
The effects of cocoa swollen‐shoot virus on the growth and yield of Amelonado and Amazon cocoa (Theobroma cacao) in Ghana
Authors: BRUNT A. A.
Published: February 2008

The virulent strain A of cocoa swollen‐shoot virus (CSSV) severely decreased the growth and yield of Amelonado cocoa (Theobroma cacao) trees kept free of capsids (Distantiella theobroma and Sahlbergella singularis) and the dieback fungus (Calonectria rigidiuscula) in Ghana. Fifteen per cent of graft‐inoculated Amelonado trees showed symptoms within 4 months, and 48, 80 and 100% within 6, 12 and 20 months, respectively. Infected trees, whether shaded or unshaded, began to decline 6 months after infection, and deteriorated rapidly during the next 27 months by which time 16 % had died and most others were moribund; fertilizer applications had no significant effect on the rate at which infected trees deteriorated. Yields of pods and dry cocoa were greatly reduced 2 yr after infection and were very low after 3 yr; yields were significantly reduced by virus infection but there were no significant further effects of applying fertilizer. These results confirm that CSSV strain A alone is very damaging and often eventually lethal to Amelonado trees in Ghana, and indicate that the conflicting results obtained previously in Ghana and Nigeria were probably due to differences in the virulence of the CSSV strains tested.

In contrast, the virus had much less effect on cocoa trees of the Amazon type; only 3% of graft‐inoculated Amazon trees showed symptoms within 4 months, and 43, 84 and 97% after 1, 2 and 3 yr, respectively. Slight deterioration of tree canopies was first detected c. 15 months after infection and, although it continued slowly during the next 21 months, the decline was much less severe than that of Amelonado trees. Yields of both unshaded and shaded trees were apparently reduced by virus infection, but yield losses were much smaller than those of Amelonado trees. These results support the present objectives of controlling the spread of CSSV in Ghana by roguing infected trees, and selecting cultivars with greater tolerance to infection for future use.
A probable rhabdovirus infecting ryegrass (Lolium spp.)
Authors: PLUMB R. T. , JAMES MARI
Published: February 2008

A particle with morphology characteristic of the rhabdovirus group was found in leaf‐dips and thin sections of symptomless Lolium spp. from several places in Britain. The particle was not transmitted mechanically nor by a number of groups of possible arthropod vectors.

Despite the lack of conclusive evidence for the viral nature of the particle its morphology and intracellular localization strongly suggest that it is a member of the rhabdovirus group. This is the first report of such a particle in Lolium spp. and in Gramineae in Britain. The presumed virus is tentatively called ryegrass bacilliform virus (RBV).
Effect of temperature on virus eradication and growth of infected tissue cultures
Authors: WALKEY D. G. A. , COOPER VALERIE C.
Published: February 2008

Cucumber mosaic (CMV) and alfalfa mosaic (AlfMV) viruses were eradicated or their concentrations greatly diminished when infected meristem tips were grown in static or shake culture at 32 or 34 oC. Similar cultures grown at 22 oC remained infected. Tobacco mosaic virus (TMV) was not eradicated from shake cultures at 32 oC and the concentration of TMV in such cultures at 32 oC was sometimes higher than at 22 oC.

The concentration of CMV and AlfMV was considerably less in cultured tissues than in infected leaf material, but that of TMV was similar. Cultures infected with CMV or TMV grew more slowly than healthy cultures. Growth of AlfMV infected and healthy cultures was similar.
Potato gangrene control by ultra low volume sprays of thiabendazole
Authors: LOGAN C. , COPELAND R. B. , LITTLE G.
Published: February 2008

A method is described by which a mist of thiabendazole (TBZ) is applied to potato tubers using an ultra low volume sprayer set over rotating rollers. The fungicidal solution (2 % a.i. TBZ) is applied at 2 1/t of potatoes moving through the mist at 50 kg/min.

Effective control of gangrene in storage was achieved in laboratory and farm trials.
Effects of soil applied benzimidazole fungicides on the behaviour of Cecidophyopsis ribis and on the transmission of Reversion virus
Authors: SMITH B. D.
Published: February 2008

Foliar sprays of benomyl partially protected potted black currant plants from infection with gall mites, whilst soil applications gave complete protection. Soil applications of benomyl, carbendazim and thiophanate‐methyl all gave significant protection against mites under field conditions. Entry of mites into new buds was not affected by these treatments, nor was the transmission of Reversion virus. The main effect of the benzimidazole fungicides is probably on the survival of mites after entry into buds and before gall formation begins.
MBC tolerance in aggressive and non‐aggressive isolates of Ceratocystis ulmi
Authors: BRASIER C. M. , GIBBS J. N.
Published: February 2008

In selection experiments, tolerance to 0–5 ppm methyl benzimidazole‐2‐ylcarbamate (MBC) occurred at a frequency of c. 1 in 1–3 ×108 conidia in both aggressive and non‐aggressive isolates of Ceratocystis ulmi. The tolerant strains were inhibited by 5 ppm MBC, however, and attempts to select strains tolerant to 10 ppm were unsuccessful. In each of three isolates examined, tolerance remained stable after fifteen successive transfers on fungicide‐free medium. Genetic control was nuclear and probably conditioned by a single gene. It is thought unlikely that the appearance of tolerant strains in nature will jeopardize the use of MBC for the control of Dutch elm disease.
The preconditioning effect of day‐length and light intensity on adult plant resistance to powdery mildew in oats
Authors: JONES I. T.
Published: February 2008

Oat genotypes with partial resistance to mildew exhibited a higher level of adult plant resistance (a.p.r.) when grown in 16 h compared with 8 h day‐length. This increased resistance was expressed in the upper leaves, and to some extent in the lower, earlier‐developed leaves.

The expression of increased resistance coincided with floral initiation in Maldwyn, but preceded it in CC4761. The development of a.p.r. and floral initiation were thus not inherently linked, but conditions which accelerated the plants' ontogeny also caused earlier expression of resistance.

For the most efficient testing of breeding material, plants should be grown at long day‐length and high light intensity. When plants are grown at 16 h day‐length and constant temperature of 15 oC, the leaf segments should be inoculated at the 6 to 8 leaf stage because normally susceptible genotypes showed marked resistance when inoculated later.
Studies on plant growth‐regulating substances
Authors: KEMP M. S. , RIUS‐ALONSO C. , WAIN R. L.
Published: February 2008

Series of I, I‐dichloro‐2‐phenoxyethanes, α,α‐dichlorotoluenes and I, I‐dihalo‐2‐phenylethanes have been examined for plant growth‐regulating activity in a number of tests. Some compounds were shown to be active and the results, together with those obtained from metabolism studies, are discussed in terms of chemical structure/biological activity relationships and mode of action.
Induced resistance to rust diseases and its possible role in the resistance of multiline varieties
Authors: JOHNSON R. , ALLEN D. J.
Published: February 2008

Inoculation of wheat seedlings with a non‐virulent race of Puccinia striiformis delayed the onset of sporulation of a virulent race and also decreased the spore mass produced. Similarly, the sporulation of a virulent race of Uromyces appendiculatus on bean seedlings was reduced by application of a weakly virulent race.

We suggest that these effects of induced resistance could retard the development of rust diseases in the field particularly in multiline varieties.
Seasonal fluctuations in ascospore concentrations of Didymella applanata in relation to raspberry spur blight incidence
Authors: BURCHILL R. T. , BEEVER D. J.
Published: February 2008

Ascospores of Didymella applanata were released in rain and dew throughout the summer, the highest concentrations occurring in May when new raspberry canes were emerging.

Infections on new canes did not develop until later in the season, when ascospore concentrations were low although pycnospores were present. Lesions first appeared near the base of the green canes just below the point of attachment of the petioles; they were not associated with obvious leaf, petiole or bud infections. Once maturation of the canes occurred, further infection was prevented.
A comparison of fungicides for the control of raspberry spur blight
Authors: BURCHILL R. T. , SWAIT A. A. J.
Published: February 2008

Effective control of raspberry spur blight (Didymella applanata) and increased crop yields in the following season were obtained in a plantation of cv. Mailing Jewel with a programme of four or five sprays commencing when the new canes first appeared. Treatments were applied at 14‐day intervals and continued until c. 2 wk before harvest.

Thiram (0.16% a.i), benomyl (0.025% a.i.), dichlofluanid (0.10% a.i.) and captan (0.10% a.i.) gave good control of the disease but as benomyl and dichlofluanid were also effective in controlling powdery mildew (Sphaero‐theca macularis) and Botrytis cinerea on the berries these fungicides appear to be the most suitable.
Effect of partial defoliation during the vegetative phase on subsequent growth and grain yield of maize
Authors: ALLISON J. C. S. , WILSON J. H. , WILLIAMS J. H.
Published: February 2008

Maize was grown in two densities, 2–47 or 4–94 plants m‐2, and the following treatments imposed: untreated, plants partly defoliated 51 days after sowing, and alternate plants in a row partly defoliated 44 days after sowing. Plants flowered about 82 days after sowing. Leaf area was decreased by 60–64% by defoliation on day 51.

Defoliation resulted in decreases in grain yield and grain number of 6–17%, though when alternate plants were defoliated in the higher density there was a substantial decrease in yield and number of grains in defoliated plants, which was largely offset by an increase in adjacent intact plants.

When plants were defoliated on day 51 subsequent growth in leaf area was similar to, and that in leaf weight nearly as large as that in untreated plants, while increase in stem weight was substantially less than in untreated plants. By the time of flowering untreated and defoliated plots differed by c. 30% in leaf area. Increments of dry matter after flowering differed by c. 15% between untreated and defoliated plots. The fraction of these increments which entered the grain was c. 90% in both untreated and defoliated plots.

When alternate plants in the row were partly defoliated on day 44 their subsequent increase in leaf area was probably 5–16% less than that of the adjacent intact plants. Increments of dry matter after flowering of plots with alternate plants defoliated were 93–95 % of those of untreated plots; leaf efficiency after flowering was slightly greater than in untreated plots. The fraction of the dry matter increment after flowering which entered the grain was c. 88 % in both intact and defoliated plants of the small density, but was 94% in intact plants and 86% in defoliated plants of the large density.
Genotypic and environmental variation in some colour characteristics of carrots
Authors: DOWKER B. D. , FENNELL J. F. M. , JACKSON J. C. , ARTHEY V. D.
Published: February 2008

Five colour characteristics were studied in seventeen carrot trials in which four varieties of the Chantenay type and four of the Autumn King type were grown at two densities at several sites for 3 yr. The Chantenay type had lower percentages of green‐topped and green‐cored roots and a higher score for internal colour; the Autumn King type had a lower percentage of purple‐topped roots. Differences between varieties within types were also detected. Large environmental effects mainly resulted from differences between individual trials. Percentages of discoloured roots were higher at the low density.

Genotype × environment (GE) interactions of practical importance were detected for all characters except internal colour. Some of these interactions were adequately described in terms of different linear regression coefficients for the genotypes, when genotypic values were regressed on environmental means. The results indicate that a low density should be chosen when selecting for reduced discolorations. Broad‐sense heritabilities, estimated from variance components for the genotypic, environmental and GE effects, show that the most efficient selection for a colour character, in one season and with four test plots per family, would be achieved when such plots were grown at four separate sites.
Strain changes in populations of tobacco mosaic virus from tomato crops
Authors: FLETCHER J. T. , BUTLER D.
Published: February 2008

The incidence of tobacco mosaic virus (TMV) Strain 1 in tomato crops of TMV‐susceptible cultivars increased from 12% in 1971 to 64% in 1974. This change coincided with the introduction of cross protection to reduce the effects of tomato mosaic. Of the isolates collected from nurseries where the technique was used in 1974, 94% were of Strain 1 compared with 39 % from the other nurseries. No new strains were found and all the isolates were tomato forms of TMV.
The effect of benomyl sprays on Sclerotinia trifoliorum and yield of red clover
Authors: JENKYN J. F.
Published: February 2008

Benomyl sprays, applied monthly from September to January, increased the survival and dry‐matter yield of red clover and decreased the numbers of apothecia of Sclerotinia trifoliorum. Two sprays increased dry‐matter yield in the first harvest year, if applied between October and December, but decreased yield in the second harvest year.
The effect of crowding on alate production and weight of apterous exules of the apple‐grass aphid, Rhopalosiphum insertum
Authors: DEWAR A. M.
Published: February 2008

Offspring of Rhopalosiphum insertum are most sensitive to crowding immediately before and after birth. Crowding throughout the nymphal and adult life of the mothers irreversibly determines most offspring as alatae whether the offspring are crowded or not. Offspring of mothers having less exposure to crowding require additional stimuli after birth. The possible evolutionary advantages of such a system are discussed. Hormonal control of alary polymorphism is implicated.

The weight of apterae declined with increased crowding. This is correlated with an increase in alate production, and may thus serve to limit the population increase to a level tolerable by the plant without killing it.
Effects of temperature on overwintering populations of the green spruce aphid Elatobium abietinum
Authors: POWELL W. , PARRY W. H.
Published: February 2008

Recorded minimum temperatures of – 7 oC or lower noticeably reduced overwintering populations of the green spruce aphid, Elatobium abietinum, in north‐east Scotland. It is suggested that, at these temperatures, ice formation in the needles of the host Sitka spruce, caused attached aphids to freeze. Aphid mortality also occurred when maximum temperatures did not rise above + 6 oC for prolonged periods, possibly as a result of starvation following an extended chill coma.

A diagrammatic representation of the main factors affecting anholocyclic populations of E. abietinum during the winter is presented to emphasize the governing role played by temperature. The balance between mortality and recruitment determines the size of the population at the end of the winter, and this in turn determines the subsequent summer infestation. It should be possible, therefore, to predict aphid outbreaks either from winter temperatures or from the number of aphids present at the end of the winter.

Temperature records obtained from integrating thermometers indicated that the inside of the lower crown tended to be the warmest part of the tree during the winter, resulting in greater aphid survival in the lower branches.
Synthesis of mycorrhiza on Pinus oocarpa
Authors: MOMOH Z. O.
Published: February 2008

Mycorrhiza was synthesized using Pinus oocarpa and Rhizopogon luteolus. After one year's successful growth in the laboratory, the seedlings raised were planted out in the field where the inoculated plants continued to grow normally. The uninoculated plants died after planting out. The results are believed to be significant in that a field establishment of mycorrhiza synthesized in controlled conditions is possible. The experiment also demonstrates the absence of suitable mycorrhizal fungi for pine establishment in Nigerian soils.
Variation in Phytophthora infestans on potatoes grown in walk‐in polyethylene tunnels
Authors: SHATTOCK R. C.
Published: February 2008

Small areas of potatoes were grown and the foliage successfully infected with Phytophthora infestans over a 10 wk period using walk‐in polyethylene tunnels which had been modified to allow easy transport from one site to another. These protected the infected crops from possible outside sources of blight and contained the disease spatially. The fungus populations spreading from foliage inoculated with P. infestans race (3,4,10, 11) were monitored for racial stability and some variation in race was recorded. In general, novel races were less, rather than more, virulent than the introduced race.