bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of yield losses as a result of co‐infection by maize streak virus and maize stripe virus in Mauritius
Authors: DOYLE M. M. ROCA DE , AUTREY L. J. C.
Published: February 2008

The effect of co‐infection by maize streak virus (MSV) and maize stripe virus (MStV) on plant growth and grain yield was investigated in a susceptible variety of maize (Zea mays), ZS 5206, in Mauritius. Under natural conditions MSV, transmitted by the leafhopper Cicadulina mbila, was normally established before MStV, which is vectored by the planthopper Peregrinus maidis; as a result, MStV symptoms were often partially or completely masked by those of MSV, making MStV detection by symptomatology very unreliable. MSV and MStV were diagnosed by ELISA and MStV by a novel method of detecting the MStV‐coded non‐capsid protein.

The maize hybrid ZS 5206 was inoculated with either MSV, MStV or both, at two stages in the growth cycle (3–5 or 7–10 leaf stage). A greater reduction in plant growth was observed in plants inoculated singly with MStV (80% and 29% for first and second stage, respectively) than with MSV (50% and 23%, respectively). No cobs were produced by plants singly infected with MStV at the first stage, or co‐infected with MSV and MStV at both stages; however, marginal grain production was recorded in plants singly infected with MSV at the first stage (91% reduction), or infected either with MSV or MStV, at the second stage (65% and 80% reduction, respectively).

In maize hybrid ZS 5206, MStV is more virulent than MSV; co‐infection by both viruses causes greater reductions in plant growth and grain yield than single infection by either virus at a given stage of plant development. In the event of co‐infection by MSV and MStV, yield losses can be erroneously attributed to MSV only if the symptoms of MStV are masked by those of the former and if adequate methods for MStV detection are not used.
Differential expression of root‐knot nematode resistance genes in tomato and pepper: evidence with Meloidogyne incognita virulent and avirulent near‐isogenic lineages
Authors: CASTAGNONE‐SERENO P. , BONGIOVANNI M. , DALMASSO A.
Published: February 2008

Reproduction of artificially selected near isogenic Meloidogyne incognita lineages virulent and avirulent against the Mi resistance gene of tomato was assessed on host and resistant lines and cultivars of pepper. Egg mass production following inoculation of individual potted seedlings with second‐stage juveniles was studied in experiments conducted in controlled environment. Artificially selected Mi‐virulent nematode populations were unable to develop on resistant pepper lines PM 217 and PM 687. This suggests that the genetic systems governing resistance to root‐knot nematodes are differently expressed in tomato and pepper, in spite of the very close phylogenetic relationships and structural genomic homologies occurring between these two vegetable crops. Moreover, these artificially selected nematode populations were also found unable to develop on the susceptible pepper cultivars California Wonder and Doux Long des Landes, while their pathogenicity was not significantly affected on susceptible tomatoes. Due to the existence of naturally virulent Meloidogyne populations, these results enhance the need for a better understanding of the mechanisms involved, in order to develop new forms of management of plant resistance to root‐knot nematodes.
Uptake of the herbicide [14C] 2,4‐D iso‐octyl in the vapour phase by tomato and lettuce plants and some effects on growth and phytotoxicity
Authors: BREEZE V. G. , van RENSBURG E.
Published: February 2008

Tomato and lettuce plants were exposed to vapour of the herbicide [14C‐phenyl] 2,4‐D iso‐octyl at concentrations in the range 0–450 pg litre‐1 for periods of 6, 24 and 72 h in separate experiments using a flowing‐air system. The rate of uptake, as indicated by plant content of radiolabel, was both linear with respect to the vapour concentration and independent of the duration of exposure. The uptake rate of tomato was greater than that of lettuce at any given vapour concentration. Uptake by the apical leaves of lettuce was higher than by the older leaves expressed on an area basis; tomato showed no effect of leaf position. Visible symptoms of phytotoxicity were shown by both species 40 days after exposure to the highest doses. Advantages of using the low‐volatile ester (iso‐octyl) of 2,4‐D to reduce vapour drift damage are discussed in terms of plant uptake.
An assessment of somaclonal variation in linseed (Linum usitatissimum)
Authors: MARSHALL G. , COURDURIES P.
Published: February 2008

Somaclonal lines of linseed from the parent cultivar Norlin were produced from a callus‐based in oitro regeneration system (the R0 generation). In field trials conducted over two seasons, 47 R1 (plants produced from the R0 generation) and 20 R2 somaclonal lines (plants produced from the R1 generation) were compared to the parent cultivar Norlin for quantitative characters. Irrespective of the genotype, traits in R1's and R2's were assessed on the basis of regression analysis as showing heritabilities of between 28% and 64%. Generally, the somaclonal variation assessed during these early generations revealed some detrimental traits, e.g. lower seed yield than the parent (control) cultivar and reduced 1000 seed weights, but a few lines were identified which had early or late flowering dates, improved seed yield and increased 1000 seed weights. It is concluded that somaclonal variation could be of value as an adjunct to classical breeding.
The response of potatoes (Solunum tuberosum L.) to salinity: plant growth and tuber yields in the arid desert of Israel
Authors: LEVY D.
Published: February 2008

The response of potato cultivars to water salinity was studied under field conditions in sandy loessial soil in the arid desert of Southern Israel. The potatoes were drip‐irrigated with water of three different salinities: water commonly used for irrigation (1.0–1.4 dS m‐1); saline water from a local well (6.1–6.9 dS m‐1); and a mixture of the two (3.84.3 dS m‐1). Salinity retarded plant emergence, enhanced haulm senescence and reduced growth of both haulms and tubers. Increasing the salinity progressively reduced tuber yields. Application of the saline water well after plant establishment (Expt A) decreased tuber yields by 615% and 22–31% in the intermediate and the high salinities, respectively. When irrigation with saline water was started soon after planting (Expt B), tuber yields were decreased by 0–17% and 21–79% in the intermediate and the high salinities, respectively. When the tubers emerged in salinised soil, tuber yields were decreased by 21–54% and 42–59% in the intermediate and the high salinities, respectively. A differential response of various cultivars to salinity was observed. None of the potato cultivars or clones exhibited exceptional tolerance to severe salinity. The earlier maturing cvs Atica and Désirée were the least susceptible to the moderate salinity imposed throughout the entire growing season; however, no association was noted between maturation time and the response to salinity.
Differences in yield determining processes of groundnut (Arachis hypogaea L.) genotypes in varied drought environments1
Authors: GREENBERG D. C. , WILLIAMS J. H. , NDUNGURU B. J.
Published: February 2008

Thirty‐six groundnut gentoypes of varied origin were evaluated for their yield, crop growth rates (C), and partitioning to reproductive sinks (p) in three trials. In the trials irrigation and sowing date were used to vary the amount of water available either throughout the crops' life, or through the grain filling phase. Genotype performance across the five environments for these attributes showed that although differences in C existed, differences in the stability of the partitioning were the dominant attribute of genotypes adapted to the drought prone Sahelian region. Data suggested that these differences were more attributable to tolerance to temperature and/or humidity than water stress. Over all treatments canopy temperatures relative to air (CATD) were strongly correlated with the C observed, but not so with yield; and differences between genotypes in the relationship between C and CATD were not statistically significant.
The effect of modifying plant structure on the yield and maturity of the white lupin Lupinus albus
Authors: MILFORD G. F. J. , DAY J. M. , LEACH J. E. , STEVENSON H. J. , HUYGHE C. , PAPINEAU J.
Published: February 2008

Experiments at Rothamsted in the UK and Lusignan in France examined the effect of artificially modifying plant structure on the yield and date of harvest of indeterminate autumn‐sown cultivars of Lupinus albus. Experiments in 1989/90 were done on the cv. Lugel at Rothamsted and those in 1990/91 on the cvs Lugel and Lunoble in both the UK and France.

At Rothamsted in 1990, when the summer was warm and dry, the indeterminate cv. Lugel ripened at the end of August and yielded 5.2 t grain/ha. At Lusignan in 1991, where summer weather was also warm and dry, the two unpruned indeterminate cultivars ripened in late July and yielded c. 4.9 t grain/ ha. However, at Rothamsted in 1991, in a season which was predominantly cool and wet, the two indeterminate cultivars were not harvested until late October and yielded only 1.5 and 2.4 t/ha.

Plants pruned to a semi‐determinate form consisting of the mainstem plus the 1st‐order branches yielded approximately the same as the unpruned inde‐terminates at Rothamsted and slightly less than the indeterminates at Lusignan. The semi‐determinates ripened 10 days earlier than the indeterminates at Rothamsted in 1990 and Lusignan in 1991, and 6 weeks earlier in the UK in 1991.

Epigonal plants with only a mainstem inflorescence, ripened even earlier than the semi‐determinates but, without branch inflorescences, produced less yield and had poorer yield stability. Where disease was not a factor, as at Rothamsted in 1990 and Lusignan in 1991, epigonal plants ripened 3 weeks earlier than the indeterminates and yielded between 1.6 and 2.6 t/ha. When the pruned epigonal plants were badly infested with Pleiochaeta, as at Rothamsted in 1991, they yielded less than 0.4 t/ha.

It is concluded that indeterminate genotypes of L. albus are well adapted to the climatic conditions of Lusignan but lack yield stability further north. For the cooler northern regions of Europe, an autumn‐sown, florally‐determinate genotype with one order of branching would produce adequate yield and have an acceptably early harvest date and yield stability. Such a genotype would have agricultural and economic value as a new protein break crop with a low requirement for nitrogen fertiliser.
Glucosinolate changes in developing pods of single and double low varieties of autumn‐sown oilseed rape (B. napus)
Authors: BILSBORROW P E. , EVANS E. J. , MURRAY F. , ZHAO F. J.
Published: February 2008

Single and double low varieties of oilseed rape were grown in the 1987/88 and 1988/89 seasons to study changes in the concentrations of total and individual glucosinolates within pods during development. Total glucosinolate concentration in seeds of all varieties increased during development when expressed on a fresh weight basis. The levels of the major alkenyl glucosinolates present in the seed; 2–hydroxy‐3–butenyl, 3–butenyl and 4–pentenyl had been reduced in the transition from single to double low varieties. The major indole glucosinolates in the seed, 4–hydroxy‐3–indolylmethyl and 3–indolylmethyl were present in the same amounts in single and double low varieties but in the latter represented a greater proportion of the total seed glucosinolate content. A decline in the total glucosinolate concentration in the pod walls with time together with the analogous profile of individual glucosinolates in the seeds and pod walls suggests that the pod wall is a major site of seed glucosinolate synthesis. Other plant parts may also have an important role to play in provision of intact glucosinolates or precursors to the pod walls for glucosinolate biosynthesis.
The influence of black bean aphid, Aphis fabae Scop., and its honeydew on the photosynthesis of sugar beet
Authors: HUREJ MICHAL , WERF WOPKE VAN DER
Published: February 2008

The effect of black bean aphids on the photosynthesis of sugar beet plants was studied under glasshouse and field conditions. The presence of up to several hundred aphids per leaf had no significant effect on CO2 exchange rates over a range of light intensities between complete darkness and light saturation. Artificially prepared honeydew, sprayed onto leaves in the same amounts and composition as was found on severely aphid‐infested plants, covered 30% of the stomata on the upper epidermis but did not significantly alter the rate of photosynthesis of these leaves in the light or the rate of respiration in the dark. The stomata on the lower epidermis were uncovered and functional. High pressure liquid chromatography of aphid‐produced honeydew detected 20 different amino‐acids. Three amino‐acids, aspartic acid, glutamic acid and gluta‐mine, made up the bulk of the amino‐acid weight in the honeydew produced on young plants, up till the 8 leaf‐stage. In the 10 to 12 leaf‐stage, several different amino‐acids occurred in substantial amounts. The amino‐acids to sugars ratio of the honeydew produced by the aphids decreased strongly as the sugar beet plants aged: from 1:6 in plants with 3 or 4 leaves to 1:25 in plants having 10 to 12 leaves.
The selective use of floral resources by the hoverfly Episyrphus balteatus (Diptera: Syrphidae) on farmland
Authors: COWGILL S. E. , SOTHERTON N. W. , WRATTEN S. D.
Published: February 2008

The use of flowers of non‐crop plants by the syrphid Episyrphus balteatus in margins of cereal fields was assessed quantitatively. G‐tests and the ‘C’ index of Murdoch (1969) were used to compare the use and abundance of twenty‐seven plant species by adult flies from June to August in the UK. The flowers of several plant species were used selectively by hoverflies throughout the season while the relative importance of others changed with date. The prospects for managing the field‐margin flora to enhance biocontrol by hoverflies is discussed.
The effect of silver and other metal ions on the in vitro growth of root‐rotting Phytophthora and other fungal species
Authors: SLADE S. J. , PEGG G. F.
Published: February 2008

A range of metal ions and the oxoanion WO42‐were toxic to zoospores of Phytophthora nicotianae parasitica in the order: Ag+ > Cu++ > WO42‐> Ni+ > Co++ > Zn+. The LD50 for Ag+, 0.11 μM (11.4 ppb), compared with 1.84 μm (117 ppb) for Cu++. Silver was similarly toxic to a range of pathogens including Pythium aphanidermatum, Thielaviopsis basicola and Fusarium oxy‐sporum f.spp. Most zoospores of Phytophthora spp. were killed by Ag+ in the range 46–460 nM (5–50 ppb), bursting at the higher concentrations. A small sub‐population of most propagules exhibited greater tolerance to silver than the whole. In 0.93 μM (100 ppb) Ag+ 1.4% of P. nicotianae parasitica zoospores survived but were all killed at 500 ppb. A population of P. cryptogea (1.9%) surviving 0.47 μm (50 ppb) were killed at 0.93 μM (100 ppb). Zoospore cysts and germlings showed the same sensitivity to silver. Oospores were mostly killed over the range 0.23–0.93 μm (25–100 ppb) Ag+, some surviving up to the lethal concentration of 9.26 μM (1000 ppb). Mycelium of P. cryptogea was generally less sensitive, with some growth occurring at 9.26 μm (100 ppb). Zoosporangiogenesis was unaffected over the range 0.47–4.65 μm (50–500 ppb). Toxicity increased with increased pH over the range 5.0–6.5.

Ionic silver was lost from solution during a microscope slide bioassay by binding to the glass surface. In the presence of chloride ions, colloidal AgCl formed which was equally toxic to P. cryptogea. Silver and AgCl were further lost from solution by colloidal agglomeration ‐ Ostwald ripening ‐ and by AgCl adsorption to glass. Silver, < 90 nM (10 ppb) Ag+ as AgNO3 and particles of silver chloride were both strongly attractive to zoospores of P. cryptogea. Spores burst or failed to germinate on entering lethal concentrations. The results are discussed in the context of the use of silver salts to control Phytophthora root‐rot pathogens and the importance of ion availability in in vitro toxicity assays.
Improved detection of iris severe mosaic virus in secondarily‐infected iris bulbs
Authors: VLUGT CORNELIA I. M. VAN DER , DERKS A. F. L. M. , BOONEKAMP P. M. , GOLDBACH R. W.
Published: February 2008

The influence of wounding and high‐temperature treatment on the detection of iris severe mosaic virus (ISMV) in secondarily ISMV‐infected iris bulbs was studied. Wounding of the bulbs just after lifting, followed by storage for 3 wk at 17°C or 20°C, increased the detectability of ISMV to 100% reliability. High‐temperature treatment and consecutive storage at 17°C induced a similar improvement of detection. It is concluded that a certain degree of stress, such as wounding or high‐temperature treatment, ultimately leads to an increase in viral antigens and thus to improvement of detection. It is hypothesised that the virus titre increases by the altered metabolism during the repair reactions as a response to stress applied to the bulbs.
Resistance to potato leafroll luteovirus can be greatly improved by combining two independent types of heritable resistance
Authors: SOLOMON‐BLACKBURN R. M. , BARKER H.
Published: February 2008

Twelve potato clones were exposed to infection by aphids with potato leafroll luteovirus (PLRV) in three field trials in order to assess their resistance to infection. Up to 92% of the plants of some clones became infected, although other clones were relatively resistant to infection and one clone remained virus‐free in all three trials. The resistance of the same 12 clones to PLRV multiplication was assessed in glasshouse‐grown plant: lants were graft‐inoculated and their daughter tubers were used to grow plants with secondary infection. High concentrations of PLRV were found in some clones (c. 1700 ng/g leaf) while in others much less virus accumulated (as little as 60 ng/g leaf). However, clones in which little virus accumulated were not necessarily those which were most resistant to infection in the field, and there was no association between the two types of resistance. Nevertheless, both types of resistance were found in some clones. The clone G8107(1), which remained virus‐free in all the field exposure trials, was also the most resistant to PLRV multiplication. The combination of these two types of resistance in cultivars should help to eliminate the spread of PLRV in crops.
The effect of pre‐harvest pruning on the quality of cassava starch
Authors: ASAOKA M. , BLANSHARD J. M. V. , RICKARD J. E.
Published: February 2008

Two cassava cultivars CMC 40 and MPer 245 were grown at the Centro Internacional de Agricultura Tropicale (CIAT) in Colombia. Specimens were pruned by the removal of aerial growth 4 weeks prior to harvest and starch granules were isolated from the roots of pruned and control plants after harvest. The glassiness and hardness of cooked roots from the pruned plants showed an increase of 60–70% and 40–60% respectively compared with the controls. Although there was some reduction in the size of the starch granules derived from the pruned roots as compared with the control, pruning had negligible effects upon X‐ray crystallinity, amylose/amylopectin contents, the elution patterns of the isoamylase debranched starch, the susceptibility of the granules to enzyme digestion, their swelling power and solubility, the temperature and enthalpy of gelatinisation and their behaviour in the Rapid Visco Analyser. Minor differences were observed when pruned and control samples were examined in the Brabender amylograph.
Effect of meteorological variates on persistence of primary conidia and capilliconidia of Erynia radicans (Zygomycotin: ntomophthorales) under natural conditions
Authors: UZIEL AVIVA , SHTIENBERG D.
Published: February 2008

Persistence of conidia of an isolate of Erynia radicans (Syn. Zoophthora radicans) was investigated in relation to the meteorological conditions which occurred during autumn‐winter of 1990–91 in the coastal plain in Israel. Capilljconidia shielded from the sun, placed on the abaxial surface of leaves of Plumeria acuminata, persisted for 24 h to at least 120 h. Exposed capilliconidia, placed on the adaxial surface of the same leaves, died within 24 h. Almost all the primary conidia shielded from the sun (placed on the abaxial surface of the same leaves) died within a single day. Conidial viability was expressed in subsequent germination on an agar medium.

Capilliconidial persistence was closely related to the daily air temperatures, expressed as cumulative day‐degrees. Differences in relative humidity had no substantial effect on capilliconidial mortality. At daytime temperatures of ≤ 20°C, mortality after 24 h incubation was lowest (≤ 34%) and the persistence duration, longest (at least 120 h). Increases in daytime temperature up to 24°C for a few hours increased mortality (37–57% after 24 h incubation) and shortened the persistence duration (72–120 h). Exposure to 24–29°C during daytime greatly increased mortality (65–58% after 24 h) and further shortened the persistence duration (24–48 h). Daytime temperatures of > 29°C were lethal to all capilliconidia within 24 h. Temperature had a profound effect on capilliconidial persistence also under controlled environmental conditions. The significance of capiliiconidial persistence is discussed in relation to activity of the fungus in its natural environment.
Chickpea chlorotic dwarf virus, a new leafhopper‐transmitted geminivirus of chickpea in India1
Authors: HORN N. M. , REDDY S. V. , ROBERTS I. M. , REDDY D. V. R.
Published: February 2008

A disease of chickpea in India, characterised by chlorosis, severe stunting and phloem browning, was shown to be caused by a geminivirus. This virus was transmitted by the leafhopper Orosius orientalis from chickpea to chickpea and several other plant species. A method for purification of this virus was devised and a polyclonal antiserum produced. The majority of the purified particles were geminate. The size of the coat protein was shown to be 32 kD and the nucleic acid was shown to be circular ssDNA of 2900 nucleotides. By immunosorbent electron microscopy this virus was shown to be unrelated to the leafhopper‐transmitted geminiviruses known to infect dicotyledons such as beet curly top, bean summer death and tobacco yellow dwarf viruses. On the basis of particle morphology, leafhopper transmission, host range and serology this virus was considered to be a new, hitherto undescribed, geminivirus and was named chickpea chlorotic dwarf virus.
Improved detection of potato leafroll virus in dormant potato tubers and microtubers by the polymerase chain reaction and ELISA
Authors: SPIEGEL SARA , MARTIN R. R.
Published: February 2008

The polymerase chain reaction (PCR) method was reliably used for detection of potato leafroll virus (PLRV) RNA in dormant tubers from field‐grown plants and in vitro‐propagated microtubers. A simple RNA extraction from tuber and microtuber tissue allowed reverse transcription and PCR amplification of viral sequences. It was also demonstrated that ELISA could be used reliably for detection of PLRV in crude sap extracts of dormant microtubers produced in vitro but not in tubers from field‐grown plants.
Preferential grazing of five varieties of spring barley by wild rabbits (Oryctolagus cuniculus)
Authors: BELL A. C. , WATSON S.
Published: February 2008

Assessment of grazing damage to five varieties of spring barley (Hordeum vulgare L.) by wild rabbits in an enclosed site revealed varietal differences. The variety Atem was consistently least grazed and Triumph most grazed by rabbits. When variety effects were removed from the analysis significant negative correlations were observed between plant height and stem damage. Differences in sugar content of varieties did not fully explain varietal selection by grazing rabbits.
Aspects of insecticide resistance in the melon and cotton aphid, Aphis gossypii (Hemiptera: Aphididae)
Authors: FURK C , HINES C M
Published: February 2008

Strains of the aphid Aphis gossypii, taken from cucumber in UK glasshouses were tested for resistance to pirimicarb, diazinon and heptenophos. Compared to a susceptible strain, resistance factors to diazinon of up to 659 were found in populations collected between 1987 and 1989. Compared to the same susceptible strain, diazinon‐resistant populations also showed a reduced response to heptenophos. All field populations tested against pirimicarb were resistant. Host plant preference tests showed that all strains (including stock cultures) tested could readily breed on cotton. However strains originally collected from chrysanthemum did not transfer to cucumber and likewise strains from cucumber would not colonise chrysanthemum. Polyacrylamide gel electrophoresis of four of the aphid strains showed differences in migration rates and intensity of staining of esterase bands. Intensity of staining was correlated with the degree of diazinon resistance.
The distribution of hop latent viroid within plants of Humulus lupulus and attempts to obtain viroid‐free plants
Authors: MORTON A , BARBARA D J , ADAMS A N
Published: February 2008

The detectability of hop latent viroid (HLVd) was investigated in field‐grown hop (Humulus lupulus L.; an herbaceous perennial in which all the aerial parts die at the onset of winter) plants, using dot‐blot hybridisation. The viroid was readily detected in all aerial tissues in the second half of the growing season but it could not be detected very early in the season. Between early‐ and mid‐season, HLVd was first detected at the base of the new stems and then apparently spread up them as they grew but only became detectable near the tips of the shoots at mid‐season, approximately at the time most elongation growth ended and flowering began. Petioles were the most convenient tissues to test, being easy to collect and, relative to leaf lamina tissue, low in inhibitors. Both dot‐blot and in situ hybridisation failed to detect HLVd in shoot tips taken from plants grown at two ‘low’ temperatures (10°C and 15°C). Failure to produce any viroid‐free plants by in vitro culture from such tips suggested that they did contain viroid but at levels too low to detect by either method. Lower temperatures and smaller explants are now being investigated as means of producing viroid‐free plants.
Occurrence of fungally transmitted wheat mosaic viruses in China
Authors: JIANPING CHEN
Published: February 2008

A soil‐borne mosaic disease of winter wheat in Sichuan, Shaanxi, Hubei and Henan provinces was associated with infection by a virus with filamentous particles and that in Shandong, Anhui, Jiangsu and Zhejiang provinces by co‐infection with this virus and soil‐borne wheat mosaic virus. The virus with filamentous particles was identified serologically, by particle sizes, cytopathology and the molecular weights of the coat protein and the two RNA species to be either wheat spindle streak mosaic virus (WSSMV) or wheat yellow mosaic virus. These viruses are probably isolates of the same virus and the name WSSMV is preferred. In baiting tests using infested soil, the dilution endpoints for detecting WSSMV were 1/625‐1/15625, and for the fungus vector, Polymyxa graminis, 1/3125‐1/15625.
Resistance to cyst nematode (Heterodera cajani) in pigeonpea cultivars and in wild relatives of Cajanus*
Authors: SHARMA S B , REMANANDAN P , JAIN K C
Published: February 2008

Heterodera cajani is an important nematode pest of pigeonpea in India. Evaluation of 58 pigeonpea cultivars and 61 accessions of Cajanus acutifolius, C. cajanifolius, C. grandifolius, C. lanceolatus, C. lineatus, C. mollis, C. pla‐tycarpus, C. reticulatus, C. scarabaeoides, C. sericeus, C. volubilis, Flemingia macrophylla, F. stricta, F. strobilifera, Rhynchosia aurea, R. bracteata, R. cana, R. densiflora, R. minima, R. rothii, R. suaveolens and R. sublobata revealed that the tested pigeonpea cultivars lacked resistance to H. cajani. Eight accessions of wild relatives were resistant and 20 accessions were moderately resistant. Based on the white cyst number on roots and low plant‐to‐plant variation, two accessions of C. scarabaeoides (ICPWs 111 and 128), three accessions of Flemingia spp. (ICPWs 194, 202 and 203), and one accession each of R. rothii (ICPW 257), R. densiflora (ICPW 224), and R. aurea (ICPW 210) were identified as resistant and promising for use in intergeneric hybridisation programmes.
Comparison of swathing and desiccation of borage (Borago officinalis) and estimation of optimum harvest stage
Authors: SIMPSON M J A
Published: February 2008

In trials of borage (Borago officinalis L.) between 1988 and 1991, swathing resulted in substantially higher yields than desiccation with diquat or glyphosate. Earlier harvest resulted in slightly lower seed oil content. Optimum swathing stage for uniform crops was estimated as that in which youngest flowers on apical cymes with shed or mature seed were the first to the third from the cyme base (i.e. stage 5,1 to 5,3). In crops with low plant population density, in which production of lowest branches is not suppressed, assessment of swathing stage is likely to be difficult and may require sampling from lower cymes.
Fruit abscission and ethylene production of four blackberry cultivars (Rubus spp.)
Authors: BURDON J N , SEXTON R
Published: February 2008

In all cultivars the force required to harvest fruit declined during ripening. The fruit retention strength (FRS) of ripe fruit varied between cultivars with ‘Ashton Cross’ and ‘Chehalem’ being easier to remove than ‘Bedford Giant’ or ‘Oregon Thornless’. The cultivars ‘Ashton Cross’ and ‘Oregon Thornless’ showed no increase in ethylene production during fruit ripening whereas ‘Bedford Giant’ and ‘Chehalem’ had increased rates of ethylene production (EPR) in the ripe fruit. Exogenous ethylene accelerated abscission, ethylene production and pigment changes in ‘Ashton Cross’ fruit at all stages of development. 1‐amino‐cyclopropane‐1‐carboxylic acid (ACC) supplied to fruit at all stages of development was converted to ethylene at levels in excess of those found naturally. The differences between cultivars are discussed with reference to the role of ethylene in both machine harvesting and post‐harvest storage of blackberry fruit.
Resistance to six viruses in the legume goat's rue {Galega orientalis Lam.)
Authors: VALKONEN JARI P T
Published: February 2008

Plants from 2nd to 6th year leys of the legume goat's rue (Galega orientalis Lam.) were tested for infection with bean yellow mosaic (BYMV), bean common mosaic (BCMV), alfalfa mosaic (AMV), broad bean stain (BBSV), red clover mottle (RCMV) and cucumber mosaic (CMV) viruses by enzyme‐linked immunosorbent assay (ELISA), electron microscopy, and by sap‐inoculation to various test plant species. No virus infections were observed in goat's rue in the field. Glasshouse‐grown seedlings of goat's rue were inoculated with the above viruses. No virus was detected in the inoculated plants. The results suggest that goat's rue is extremely resistant to the above six viruses which are important in other forage legumes.
Occurrence of barley yellow dwarf virus (BYDV) isolates in different farmland habitats in western France and south‐west England
Authors: HENRY M , GEORGE S , ARNOLD G M , DEDRYVER C A , KENDALL D A , ROBERT Y , SMITH B D
Published: February 2008

The incidence and distribution of the three principal isolates of barley yellow dwarf virus (PAV, RPV and MAV) are described in winter cereal crops, cereal (stubble) regrowth and grasses from 11 sites in western France and south‐west England during 1987 and 1988. Isolates were identified by indirect ‘sandwich’ ELISA using the monoclonal antibodies MAC91, MAC92 and MAFF2. More virus infection occurred in all localities and in most of the plant communities sampled, with the exception of perennial grass leys, in 1987 than in 1988. All three isolates were widespread. MAV was associated more with sites further north and PAV more with those further south. The geographical distribution of RPV was less variable. Underlying these trends, the relative abundance of isolates differed considerably between habitats. RPV always predominated in perennial grass leys and MAV in most cereal crops, although in the latter MAV was less prevalent in 1987 than in 1988. The greatest regional difference was found in stubble regrowth where PAV predominated in France but MAV predominated in England. Grasses from field margins (only sampled in England) were mainly infected by MAV and RPV. The implications of these findings for the epidemiology of BYDV are discussed, especially the roles of different host plant communities or habitats in the annual infection cycle of small‐grain cereals.
Inheritance and genetic linkage of fusarium wilt {Fusarium oxysporum f.sp. cucumerinum race 1) and scab {Cladosporium cucumerinum) resistance genes in cucumber (Cucumis sativus)
Authors: VAKALOUNAKIS D J
Published: February 2008

The inheritance of resistance of the cucumber cv. SMR 18 to the race 1 of Fusarium oxysporum f.sp. cucumerinum, the linkage relationship between resistance to race 1 of F. oxysporum f.sp. cucumerinum, resistance to Cladosporium cucumerinum and fruit spine colour, and the reactions of several cucumber cultivars to inoculations with race 1 of F. oxysporum f.sp. cucumerinum and C. cucumerinum were examined. The inbred line Straight 8 (P,), which has white fruit spines and is susceptible to both fusarium wilt and scab was crossed with the inbred line SMR 18 (P2), which has black fruit spines and resistance to both diseases. When F, F2, F3, BC1P1 BC1P2 and BC1P1 selfed progenies were inoculated at the cotyledon stage with a suspension of spores of race 1 of F. oxysporum f.sp. cucumerinum, the ratios of resistant to susceptible plants indicated that resistance was conferred by a single dominant gene, designated Fcu‐1. When 171 BC^! plants were selfed and from each resulting F2 family different groups of 15–25 seedlings each were tested for resistance to either disease, segregation data indicated that the Fcu‐1 locus and the Ccu locus for C. cucumerinum resistance were completely linked. No evidence for linkage was found between the Fcu‐1 (Ccu) locus and the B locus for fruit spine colour. Among the 59 cultivars tested at the seedling stage, 15 were susceptible, while the remainder were highly resistant to inoculations with both pathogens.
Inter‐plot competition in yield trials of potatoes (Solanum tuberosum L.) with single‐drill plots
Authors: CONNOLLY T , CURRIE I D , BRADSHAW J E , McNICOL J W
Published: February 2008

An experiment was carried out to assess the significance of inter‐plot competition in a yield trial of potato cultivars. Seventeen cultivars were deliberately chosen and assessed for yield in single‐drill and four‐drill plots. Inter‐plot competition for fresh‐weight yield was a significant factor in the single‐drill plots. It was modelled using a common competition coefficient with a covariate based on neighbour fresh‐weight yields. In contrast, there was no statistically significant inter‐plot competition for specific gravity. After adjustment for inter‐plot competition, varietal ranking in estimated monoculture yield differed little from that based on unadjusted means. However, there was a reduction in the range of yield estimates, and a closer agreement with the observed pure‐stand yields from the inner two drills of the four‐drill plots. The adjustment for monoculture performance was most pronounced for the higher and lower yielding varieties, as expected from the assumption that the performance of high yielding varieties was enhanced in a competitive environment at the expense of low yielding ones.

A general and flexible method of estimating competition coefficients in variety trials, together with a suitable algorithm, was developed and is explained in an appendix. It was used to check for inter‐plot competition in a number of potato trials with single‐drill plots and a large number of entries. Competition was found in some trials but not in others. Thus, where potato tubers are grown in single‐drill plots for assessment of fresh‐weight yield, adjustment should be made for inter‐plot competition when evidence of inter‐drill competition is found.
Postharvest disease control in mangoes using high humidity hot air and fungicide treatments
Authors: COATES L M , JOHNSON G I , COOKE A W
Published: February 2008

The disease control efficacy of quarantine heat treatments developed for fruit fly disinfestation in mangoes cv. Kensington Pride was evaluated in this study. Heat was applied using high humidity (>95% r.h.) hot air (HHHA) at temperatures ranging from 47–49°C.

Anthracnose, caused by Colletotrichum gloeosporioides, was well controlled in mangoes heated to a core temperature of 46°C, 47°C or 48°C for 24, 10 or 8 min respectively, prior to ripening at 23°C for 16 days. Stem end rot, caused by Dothiorella dominicana and Lasiodiplodia theobromae, was not satisfactorily controlled by these treatments.

In a subsequent experiment, fruit were immersed in a hot benomyl (0.5 g a.i. litre“1 at 52°C for 5 min) or unheated prochloraz (0.25 ml a.i. litre1 at 28°C for 30 s) dip before or after the application of HHHA (core temperature of 47°C for 10 min). During storage at 23°C for 15 days, the incidence of stem end rot was reduced by HHHA alone, although immersion in hot benomyl either before or after HHHA treatment greatly improved stem end rot control.

HHHA treatment (core temperature of 46.5°C for 10 min) alone reduced the incidence of anthracnose in mangoes stored at 13°C for 14 days prior to ripening at 22°C, although a combination treatment consisting of HHHA and either hot benomyl or unheated prochloraz gave complete control of anthracnose under these storage conditions. HHHA treatment alone gave no control of stem end rot in mangoes stored at 13°C prior to ripening at 22°C. A supplementary hot benomyl treatment was required for acceptable control of this disease in cool‐stored mangoes. The development of yellow skin colour in fruit was accelerated by HHHA treatment.
The effects of crop development upon slug distribution and control by Abax parallelepipedus (Coleoptera: Carabidae)
Authors: SYMONDSON W O C
Published: February 2008

The polyphagous carabid beetle Abax parallelepipedus has been shown to be capable of controlling slugs within a lettuce crop in previous studies. This report describes experiments undertaken in plots within a polythene tunnel. Field slugs, Deroceras reticulatum, were introduced to plots containing either large or small lettuce plants, at 30 slugs per plot. The plots were further subdivided into those with or without six beetle predators. Slug numbers were assessed after two weeks, and were found to be affected by plant size, both with and without the presence of predators. These two factors had an additive effect, with both small plant size and the presence of beetles causing significant reductions in slug numbers. Plots with beetles contained either males or females, and females were shown to be significantly better at reducing slug numbers than males, particularly within plots of small plants. The four principal treatments (combinations of two plant sizes and the presence/absence of beetles) generated four distinct patterns of slug distribution within the plots. The potential of the residual slug populations to inflict further damage was measured in a subsequent crop of seedling lettuces. It appeared that the beetles were generally incapable of capturing slugs within large lettuce plants, but were effective predators at soil level. Possible reasons for the survival of fewer slugs in plots with small plants, both with and without the presence of predators, are discussed.
The effect of weeds on the numbers of hoverfly (Diptera: Syrphidae) adults and the distribution and composition of their eggs in winter wheat
Authors: COWGILL S. E. , WRATTEN S. D. , SOTHERTON N. W.
Published: February 2008

The abundance and species composition of syrphid adults in herbicide‐treated and untreated headlands was recorded in a replicated within‐field experiment conducted over a two‐year period. The highest numbers of the most abundant syrphid species, Episyrphus balteatus, were recorded in the untreated headland strips. Analysis of the behaviour of the adult flies showed that they were retained in the untreated strips because they were foraging on the flowering non‐crop plants.

The distribution of syrphid eggs between herbicide treated and untreated headland replicates was examined. A significant positive relationship between the numbers of eggs per aphid and weed density was detected during June in the second year of the study. This is in part attributed to the tendency of Melanostoma females to oviposit on non‐crop plants.

The implications of the implementation of a modified herbicide regime in the headlands of cereal fields for the biological control of cereal aphids by syrphid larvae is discussed.
Fungus gnats vector Fusarium oxysporum f.sp. radicislycopersici1
Authors: GILLESPIE D. R. , MENZIES J. G.
Published: February 2008

Fungus gnat adults transported Fusarium oxysporum f.sp. radicis‐lycopersici from Petri dish culture and infected host plants to the roots and hypocotyls of healthy tomato and bean plants. The source of the fungus did not affect the ability of fungus gnats to transport the fungus to healthy hosts. The presence of fungus gnat larvae in media in which young tomato plants were grown did not increase the incidence of plant infection by the pathogen. Fungus gnat adults appear to aid in the dissemination of F. oxysporum f.sp. radicis‐lycopersici.
Components of partial resistance of barley to Rhynchosporium secalis: use of seedling tests to predict field resistance
Authors: KARI ANDREAS G. , GRIFFITHS ELLIS
Published: February 2008

Components of partial resistance [disease incidence (DI), infection frequency (IF), latent period (LP), spores per lesion (SPL)] were assessed on glasshouse‐grown barley seedlings following inoculation with spore suspensions of Rhynchosporium secalis at growth stage 12 (Zadoks, Chang & Konzak, 1974). Four experiments were carried out at different times during 1988. Three spring barley cultivars [two from Cyprus (cvs Kantara and Athenais) and one from the UK (cv. Triumph)] were used in the first three experiments. In the fourth experiment eight additional UK cultivars with NIAB resistance ratings ranging from 3 to 9 were used. Two races of R. secalis were used in the first three experiments and three in the fourth.

The three cultivars, Kantara, Athenais and Triumph, were examined in all four experiments and significant differences detected for virtually all components of partial resistance in each. Differences, however, were often small and ranking of cultivars varied in different experiments. The greater susceptibility of cv. Kantara compared to cv. Athenais, observed under field conditions in Cyprus, would not be anticipated from the small differences in components of partial resistance observed in these experiments, but, for these cultivars, the possibility of a marked genotype x environment interaction cannot be discounted.

Mean values for the components of partial resistance differed in the four experiments. LP was correlated with mean glasshouse temperature from inoculation to the onset of sporulation but differences in IF and SPL were not correlated with temperature. For these components, light quality and/or duration appeared to be more important.

Overall, there were no differences between races but significant race X cultivar interactions were observed in two experiments.

In the fourth experiment, examining 11 cultivars, there were significant differences between cultivars for all components of partial resistance. IF and LP were correlated but neither of these components was correlated with SPL indicating independent control of this latter component. Both IF and LP were correlated with field performance (NIAB ratings) but there was no correlation with SPL. However, combining IF with mean values of SPL restricted to the 5 days following the end of the LP, produced the best correlation (r= 0.92) with NIAB ratings.

Problems of assessing components of partial resistance and possible means of improving assessments are discussed.
Phytophthora cryptogea root rot of tomato in rockwool nutrient culture:
Authors: KENNEDY R. , PEGG G. F. , WELHAM S. J.
Published: February 2008

The effect of root temperature on growth and yield of rockwool‐grown tomato plants infected with Phytophthora cryptogea was investigated. Measurements of shoot and root growth were taken at high (25oC) and low (15oC) root temperatures during the generative phase of growth. The growth of roots of healthy and P. cryptogea‐infected tomato plants in rockwool blocks was higher in plants grown with roots at 25oC than at 15oC after 60 days and a similar effect was found in slabs after 98 days. Under sub‐optimal conditions for growth the disease became severe when root temperatures were low. Growth of roots was greatest when roots were maintained at a high temperature in combination with an ambient air temperature of c. 15oC and the response was greater in cv. Counter than cvs Calypso and Marathon. Water‐soluble carbohydrates of roots were higher in those produced in blocks than slabs and were reduced by infection compared to healthy plants with roots at 15oC and 25oC. Reduced transpiration rates were found 17 days after inoculation in symptomless plants grown at a root temperature of 25oC. Infection, regardless of the temperature of the roots or cultivar, led to reduced stem growth. The plants grown at 25oC were taller than those with a root temperature of 15oC. After 9 wk of harvest, the cumulative fruit yields in infected cvs Counter and Calypso grown at 25oC were comparable to that in healthy plants grown at either temperature and cumulative fruit numbers followed a similar pattern. High root temperatures led to delayed fruit ripening between weeks 3–10 and a larger number of unripe fruit. The weight of unripe fruit from infected plants grown at 25oC at the terminal harvest was higher than from healthy plants with roots maintained at 15oC.
Attachment of the Flavescence doree pathogen (MLO) to leafhopper vectors and other insects
Authors: LEFOL C. , CAUDWELL A. , LHERMINIER J. , LARRUE J.
Published: February 2008

Flavescence doree (FD) is an important yellows disease of grapevine, caused by mycoplasma‐like‐organism (MLO) and is transmitted in the field by the leafhopper Scaphoideus titanus Ball. It can be transmitted in the laboratory between Vicia faba test plants by the leafhopper, Euscelidius variegatus Kbm. A technique to identify a specific attachment system between the MLO and the leafhopper vectors was developed. In this method, called “Double Dot”, extracts of macerated healthy whole insects or organs applied to a support membrane or cryosections of healthy whole leafhoppers, are incubated with a MLO‐enriched extract from FD‐infected V. faba or FD‐infected E. variegatus. Attached MLO cells were identified by immunolabelling using FD‐MLO specific monoclonal antibodies. Attachment of MLO cells was obtained on extracts of healthy S. titanus and E. variegatus and on tissues such as salivary glands, hemolymph and alimentary tract. On cryosections, MLO attachment was obtained on acini IV and V of the salivary glands and on some acini III, on the ventriculus of the alimentary tract, and on the abdomen fat bodies. “Double dot” experiments were done using other insect species, and MLO cells attachment was obtained on most MLO‐vector insects but also on insects from a few non‐vector species.