bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of host plant resistance and chemical control of the head bug, Calocoris angustatus Leth., on grain quality and seedling establishment in sorghum
Authors: SHARMA H C , SOMAN P , SUBRAMANIAN V
Published: February 2008

The sorghum head bug, Calocoris angustatus Lethiery (Hemiptera: Miridae), is one of the most important pests of grain sorghum in India. Studies were conducted to quantify the effect of head bug damage on grain quality and seedling establishment on head bug‐resistant cultivars (IS 17610 and IS 21443), a moderately susceptible cultivar (IS 9692), and a susceptible commercial cultivar (CSH 11). Differences in 1000‐grain mass, seed germination and percentage of floaters were significant between protected and unprotected plots in CSH 11 and IS 9692, but not in IS 17610 and IS 21443. Grain damage ratings were significantly lower in IS 17610 than in IS 9692 and CSH 11 across different protection levels.

Head bug‐damaged grain had greater protein content than the undamaged grain, possibly because of depletion in starch, and a marginal increase in soluble sugars. Amounts of proline and tyrosine were greater in the bug‐damaged grain than in the undamaged grain, while the reverse was true for aspartic acid, methionine, leucine and lysine. Head bug damage also increased the tannin content in IS 9692 (which is a high‐tannin genotype).

Moisture regimes and insecticide protection levels significantly affected seedling emergence. Seedling emergence of CSH 11 was lower than that in IS 17610. In the latter genotype, the differences between protected and unprotected plots were not significant. Head bug damage thus not only leads to quantitative loss in grain yield, but also spoils the grain quality and renders the grain unfit for seed purposes. These qualitative effects should be taken into account while estimating losses due to bug damage and determining economic thresholds.
Two methods for the prediction of Mycocentrospora acerina infection on stored carrots
Authors: HERMANSEN ARNE , AMUNDSEN TERJE
Published: February 2008

Carrot plants were collected from 26 fields located in different districts in Norway during 1985, 1986 and 1987. Leaves were sampled in the first two years, and roots were sampled in all years. Incidence of Mycocentrospora acerina on the leaves at harvest was correlated (r = 0.82) to the incidence of M. acerina on the roots after storage at 0–1°C for six months (long term storage). Incidence of M. acerina on roots sampled about six weeks before harvest (date c) and placed at 10°C for six weeks (test storage) was correlated (r = 0.84) to incidence of the pathogen after long term storage on roots sampled at harvest (date d). Test storage and long term storage data from parallel samples taken at date d was more strongly correlated (r = 0.90).
Effects of sowing date and vernalisation on the growth of winter barley and its resistance to powdery mildew (Erysiphe graminis f.sp. hordei)
Authors: WHITE N. , JENKYN J F.
Published: February 2008

Detailed studies on the production of individual leaves, and the development of powdery mildew on them, were made in field plots of winter barley sown on different dates. The greater severity of the disease on early‐sown than on later‐sown seedlings during the autumn and winter can probably be explained mainly by changes in the abundance of inoculum and the suitability of the weather for infection. Results from glasshouse experiments suggest that the differences may be reinforced by direct effects of vernalisation on the susceptibility of seedlings to the disease. Contrary effects of sowing date on mildew severity during summer are probably due to the progressively greater resistance to mildew of the later‐formed than of seedling leaves, and the earlier appearance of corresponding leaves on early‐sown than on later‐sown plants. Early sowing can also increase the total number of leaves produced per stem. Therefore, because resistance of the leaves increases progressively, the maximum degree of resistance expressed by the later‐formed (e.g. flag) leaves will often be greater on early‐sown than on later‐sown plants.
Endophytic bacterial systems governing red clover growth and development
Authors: STURZ A V. , CHRISTIE B R.
Published: February 2008

Endophytic competent bacteria capable of promoting both beneficial and detrimental growth responses in red clover (Trifolium pratense L.) were recovered from three adjacent areas of farmland each having a different cropping history — continuous red clover, continuous potatoes (Solanum tuberosum L.) or a 2 yr rotation of red clover and potatoes. The population composition of these rhizobacteria was altered by the various crop sequences. The greatest instance of significant growth responses (beneficial or detrimental) occurred with those bacteria derived from the clover‐potato soil, suggesting increased interactive ‘competition’ among bacterial populations at the ‘interface’ between different crop rotations. Whether bacterial strains promoted or inhibited growth appeared to depend on the cropping history and prior exposure of pre‐bacterised clover plants to the natural microflora in the peat‐based growing media. The interaction between bacterial colonists influenced plant trait expression to the degree that some characteristics were completely masked. Improvements in plant growth were interpreted as an allelopathic side‐effect of the competition between endophytes for the same ecological niche, from which the plant inadvertently benefits.
Use of isoenzyme and protein phenotypes to discriminate between six Pratylenchus species from Great Britain
Authors: IBRAHIM S K. , PERRY R N. , WEBB R M.
Published: February 2008

Six species of Pratylenchus indigenous to Great Britain, P. crenatus, P. fallax, P. neglectus, P. penetrans, P. pinguicaudatus and P. thornei were analysed by slab gel electrophoresis to compare protein patterns and isoenzyme phenotypes of esterase, glucose‐6‐phosphate dehydrogenase, isocitrate dehydrogenase, phosphoglucose isomerase and phosphoglucomutase. Multiple electromorphs were obtained from all enzymes examined. The results demonstrated that isoenzyme phenotypes are useful to supplement the morphological characterisation of these nematode species. Pair‐wise comparisons of the six species were performed giving coefficients of similarity in the range 11–41%. A dendrogram of the six species, generated from the five enzyme banding patterns, gave two groups: group 1 contained P. pinguicaudatus, P. fallax and P. thornei and group 2 contained P. penetrans, P. neglectus and P. crenatus.
Postharvest treatments against Western Flower Thrips [Frankliniella occidentalis (Pergande)] and Melon Thrips (Thrips palmi Karny) on orchids
Authors: MANN J A. , TATCHELL G M. , DUPUCH M J. , HARRINGTON R. , CLARK S J. , McCARTNEY H A.
Published: February 2008

Postharvest treatments, including insecticidal dips, isopropyl alcohol dips, insecticidal fogs and hot‐water immersion, were evaluated to control mixed infestations of Western Flower Thrips (Frankliniella occidentalis) and Melon Thrips (Thrips palmi) on dendrobium orchid blossoms. The limiting factor for all postharvest treatments was phytotoxicity, characterised by a loss of vase life that differed among cultivars. Insecticidal dips and insecticidal fogs were less phytotoxic than hot‐water immersion and isopropyl alcohol dips. Insecticidal fogs consisting of abamectin 2.0% e.c. and abamectin tank‐mixed with Pyrenone e.c. (6% pyrethrins, 60% piperonyl butoxide) reduced the mean number of thrips per blossom by 93.8% and 92.3%, respectively and were nonphytotoxic. An insecticidal aerosol, Floragas (2% permethrin and 0.1% pyrethrum dissolved in high pressure liquified CO2) reduced thrips by 33% to 54% with no phytotoxicity. Insecticidal dips for 3 min with agitation reduced the mean number of thrips per blossom by 43.7% to 99.1%. Of the 12 insecticides and one surfactant tested, only chlorpyrifos 44.4% e.c., fluvalinate 22.3% f., and chlorpyrifos 50% d.f. were both effective and nonphytotoxic. Immersion in water at 49.5°C for 15 and 20 s reduced the mean number of thrips per blossom by 88.1% and 95.3%, respectively. A 70% solution of isopropyl alcohol applied as a postharvest dip did not kill all thrips and was extremely phytotoxic to blossoms.
Effects of fungicides on the growth and conidial germination of Colletotrichum coccodes and on the development of black dot disease of potatoes
Authors: READ P J. , HIDE G A.
Published: February 2008

The effects of 10 fungicides on the growth of Colletotrichum coccodes in agar culture and on the germination of conidia was investigated. In field experiments in 1990 and 1991 the extent to which treating black dot‐affected potato seed tubers with fungicides affected the development of the disease on stem bases, roots and tubers was assessed. Black dot was also assessed on plants from field trials in 1990 which were designed to investigate the efficacy of the soil sterilant 1,3‐dichloropropene (Telone) and two nematicides, aldicarb (Temik) and ethoprophos (Mocap).

Prochloraz and fenpiclonil were the most effective fungicides in decreasing the size of C. coccodes colonies on agar. Imazalil, propiconazole and dichlorophen were also effective, but at higher concentrations, whereas tolclofos‐methyl, thiabendazole and benomyl were only moderately effective. Resistant sectors developed from inhibited colonies on agar containing fenpiclonil and tolclofos‐methyl. Conidial germination was prevented at 1 mg/litre fenpiclonil and 5 mg/ litre dichlorophen; imazalil, benomyl and thiabendazole were also moderately effective.

Fenpiclonil and propiconazole seed tuber treatments consistently decreased black dot infection on roots, stem bases and daughter tubers early in the season, but only fenpiclonil decreased disease on tubers at harvest in October. Propiconazole also delayed emergence and decreased stem numbers. Soil treatment with 1,3‐dichloropropene, aldicarb or ethoprophos had no effect on black dot but Rhizoctonia solani tuber infection and black scurf were increased.
Biology of the hop cyst nematode Heterodera humuli
Authors: MENDE N VON , McNAMARA D G.
Published: February 2008

In an intensively sampled English hop garden, cysts of Heterodera humuli were found in every sample taken. Most occurred in the top 15 cm of soil, decreasing in number by half with every 15 cm in depth. Numbers of second‐stage juveniles fluctuated during the vegetative period in a pattern which indicated that more than one generation, possibly two to three, were produced. The generation time was about 1.5 months. In pot experiments under controlled conditions (20°C; 16 h light/day) the life cycle lasted 40 days. The optimal temperature was 20°C for the development of H. humuli in the roots of its host Humulus lupulus. Most H. humuli juveniles invaded hop roots at 15°C, but egg hatch was greatest at 20°C. In moist soil, second‐stage juveniles survived for at least 54 days and thereafter invaded roots and reproduced.
The first record of the root‐endoparasitic nematode Zygotylenchus guevarai in Britain
Authors: BARKER A D P. , HOOPER D J.
Published: February 2008

The root‐endoparasitic nematode Zygotylenchus guevarai is recorded for the first time in Britain. It occurred in soil from a crop of glasshouse grown Alstroemeria in West Sussex, England.
Detection of cross reactive antigens between Pestalotiopsis theae and tea leaves and their cellular location
Authors: CHAKRABORTY B. N. , BASU P. , DAS R. , SAHA A. , CHAKRABORTY U.
Published: February 2008

Among the 12 varieties of tea tested against three isolates of Pestalotiopsis theae, causal agent of grey blight disease, Teen Ali‐17/1/54 and TV‐23 were found to be highly susceptible while CP‐1 and TV‐26 were resistant under identical conditions. Leaf antigens were prepared from all the tea varieties, three isolates of P. theae and a non‐pathogen of tea (Bipolaris tetramera). Polyclonal antisera were raised against mycelial suspensions of P. theae (isolate Pt‐2) and leaf antigens of Teen Ali‐17/1/54 and CP‐1. These were compared an immunodiffusion test and enzyme‐linked immunosorbent assay to detect cross reactive antigens (CRA) shared the host and the parasite. CRA were found among the susceptible varieties and isolates of P. theae (Pt‐1, 2 and 3). Such antigens were not detected between isolates of P. theae and resistant varieties, B. tetramera and tea varieties or isolates of P. theae. Indirect staining of antibodies using fluorescein isothiocyanate (FITC) indicated that in cross sections of tea leaves, the CRA was concentrated in the epidermal cells and mesophyll tissues. CRA was present in the young hyphal tips of the mycelia and on the setulae and appendages of the conidia of P. theae.
Cavity spot of carrots: Interactions between the host and pathogen, related to the cell wall
Authors: ZAMSKI E. , PERETZ I.
Published: February 2008

This study investigates the structural aspects of cavity spot pathogenesis. Different Pythium spp. isolated from infected carrots, apples and melons were cultured on agar in Petri dishes and used for inoculation of uninfected carrots. Only slow‐growing Pythium spp. (< 15 mm day‐1), such as P. violae and P. sulcatum caused cavity spot lesions. It is suggested that slow‐growing species are able to penetrate, albeit slowly, into the plant tissue for 3 to 4 days before a hypersensitive reaction develops. Fast‐growing species, however, did not cause lesions. Based on ultrastructural observations, we suggest that the following sequence of events occurs between the plant and the pathogen: The fungus infects the walls and grows for several days, during which time small amounts of wall‐degrading enzymes are secreted. Phenylalanine ammonia lyase (PAL) activity and phenols increase linearly immediately upon inoculation. There was a lag phase of about 5 days before lignin began to increase linearly for about a month. Dissolution of wall components decreases the solute potential and water potential in the apoplast. Thus, water moves from the symplast into the apoplast, the turgor pressure gradually dissipates, and the cells shrink and eventually die.
Occurrence of Verticillium dahliae on sunflower (Helianthus annus) in the UK
Authors: CHURCH V. J. , McCARTNEY H. A.
Published: February 2008

In August 1994 verticilliosis‐like symptoms were noticed in a maturing crop of sunflower at IACR‐Rothamsted. Wilting plants with chlorotic areas on some leaves, and dark areas of microsclerotia at the base of stems, were first observed on 11 August. As the plants matured, dark stripes were also observed on the stems. Many stems became brittle and later collapsed. Infected xylem showed a brown discolouration, later turning to black, and microsclerotia developed. Verticillium dahliae was isolated from all parts of the plant.

In general, once symptoms were present, the incidence of verticilliosis‐affected plants increased, and the disease developed, more rapidly in early maturing varieties than in the later maturing types. At harvest, incidence ranged between 24.5% and 89.8%, depending on variety. Early maturing varieties appeared to be more susceptible than later maturing types.

Isolates of V. dahliae were cultured in the laboratory. Sunflower plants were artificially inoculated with these isolates and developed verticilliosis symptoms when grown under controlled environmental conditions.
Specific detection of the Andean strain of potato virus S monoclonal antibodies
Authors: ČEřOVSKÁ N. , FILIGAROVÁ M.
Published: February 2008

Four mouse monoclonal antibodies (MAbs) specific for the Andean strain of potato virus S (PVSA) were produced. The MAbs reacted with four isolates of PVSAbut did not react with four isolates of ordinary strain of PVS (PVSO). The MAbs did not react with six other members of the Carlavirus group including potato virus M. A MAb‐based ELISA, using MAbs (IEB‐1 and IEB‐4‐AP), was devised and shown to specifically detect PVSA.
Cloning and molecular analysis of double‐stranded RNA associated with grapevine leafroll disease*
Authors: HABILI N. , REZAIAN M. A.
Published: February 2008

Eight major dsRNA species ranging from 1.0 to 19.5 kbp were detected in a low‐yielding clone of Sultana (Thompson seedless) grape (Vitis vinifera L., cv. Sultana, clone B4L) affected leafroll disease. Using total dsRNA from this Sultana line as template, a number of cDNA clones were produced. The clones were used as probes for northern blot analysis of dsRNA extracted from Sultana B4L, and from six other grapevine leafroll‐infected Sultana sources differing in yield performance. Based on the hybridisation of each probe with dsRNA bands from various Sultanas, the cDNA clones could be divided into three groups. One group of cDNA clones hybridised to high molccular weight dsRNA (19.5 kbp) from two low‐yielding Sultanas, another group hybridised to high Mr dsRNA from three low‐yielding Sultanas and the third group hybridised to a number of smaller dsRNA species ranging in size between 1.15 and 6.5 kbp. Using the latter cDNA clones, the sequence of 965 nucleotides at the 5′‐end of a 1.15 kbp dsRNA (dsRNA 6) of B4L Sultana was determined. This RNA contains an open reading frame encoding a putative protein of M, = 33 441 with no homology to known protein sequences. The sequence of dsRNA 6 was found to overlap larger dsRNAs of sizes between 2.2 to 6.5 kbp. This allowed us to determine the sequence upstream of the 5′‐end of the positive strand of dsRNA 6. The nucleotide sequence neighbouring the 5′‐end of the positive strand of dsRNA 6 conforms to a consensus sequence proposed as a subgenomic promoter element for the coat protein gene of positive strand RNA plant viruses. The results indicate that more than one virus was present in Sultana B4L and that dsRNA 6 may be a subgenomic species of viral origin.
Beet luteovirus coat protein sequence variation
Authors: de MIRANDA J. R. , STEVENS M. , de BRUYNE E. , SMITH H. G. , BIRD C. , HULL R.
Published: February 2008

The sequences of cDNA clones covering the coat protein genes of 29 isolates of beet mild yellowing virus from sugar beet and beet western yellows virus mainly from oilseed rape were compared. The sequences could be partitioned into seven distinct clusters falling into three main groups. Group 1 isolates were found both in oilseed rape and sugar beet mainly from north Europe; group 2 isolates were from hosts other than sugar beet in England and France; group 3 isolates were beet‐specific and found from northern Italy and Iran. The factors affecting this variation and its significance in relation to coat protein‐mediated protection are discussed.
Mode of action of chlorsulfuron in a sensitive wheat (Triticum aestivum) cultivar: primary and secondary effects on nitrogen assimilation
Authors: DASTGHEIB F. , ANDREWS M. , MORTON J. D. , BARNES M. F.
Published: February 2008

Chlorsulfuron (15 g a.i. ha‐1) inhibited growth of wheat (Triticurn aestivum L. cv. Rongotea) especially on high nitrate (NO3) supply. Decreased growth at high NO‐3 was associated with higher concentrations of reduced nitrogen (N) and NO‐3 in the shoots. Seven days after spraying (DAS), shoot dry weight (dry wt) of sprayed plants was similar with NO‐3 or branched chain amino acids as main N supply but 28 DAS, shoot dry wt was greater with the amino acid treatment.

One DAS, chlorsulfuron caused substantial decreases in extension of the youngest leaf and acetolactate synthase activity and valine content of shoots of plants supplied with NO‐3 or branched chain amino acids. Total amino acid content of shoots was greater in sprayed plants than in unsprayed plants 1 DAS. Acetolactate synthase activity of sprayed plants supplied low NO‐3 returned to normal 14–21 DAS. For sprayed plants transferred from low to high NO‐3 supply 7, 14 or 21 DAS, shoot dry wt 50 DAS increased with increased time of transfer to high NO‐3 while shoot NO‐3 content decreased. Shoot NO3 content of sprayed plants transferred to high NO‐3 supply 7 or 14 DAS was similar to that in unsprayed plants at applied NO‐3 concentrations which inhibited growth. It is concluded that inhibition of acetolactate synthase is likely to be the primary mode of action of chlorsulfuron in this wheat cultivar; data are consistent with the proposal that subsequent NO‐3 accumulation can also inhibit growth.
Development of cercospora blight epidemics and effect on the summer annual Heliotropium europaeum in the field
Authors: BRUN L. A. , SHEPPARD A. W. , DELMOTTE E. , HASAN S. , JOURDAN M.
Published: February 2008

Heliotropium europaeum, common heliotrope, is a serious economic weed in southern Australia. Cercospora blight occurs on H. europaeum in both its native (Mediterranean) and non‐native (Australian) range. The causal agents are genetically different forms of an asexual pathogen in the form‐genus Cercospora in each region. Natural epidemics of cercospora blight killed weed infestations in both Australia and France. The epidemiology of the disease did not differ between the two regions once differences in rainfall had been considered. Rainfall was important for disease spread. In France, field inoculation experiments were conducted using different concentrations of conidia prepared from a monospore isolate. Cercospora blight reduced seed production 89%, but did not reduce viability. Increased inoculum concentration and inoculation of younger plants encouraged an early epidemic, but did not affect the rate of disease development once the epidemic took hold. In order to be effective at controlling this weed in Australia, these pathogens need to attack young hosts and have regular rain‐splash to facilitate spread to new growth.
The effects of inbreeding on the parental values of potato dihaploids
Authors: MAINE M J DE.
Published: February 2008

Dihaploids obtained from a somatically chromosome‐doubled dihaploid potato were crossed with Solanum phureja clones. To test the effect of inbreeding, measurements were made of their seed production and the tuber yield, tuber number and mean tuber weight of their offspring. On average, seed production of the second generation dihaploids was higher than that of the original dihaploid progenitor. Progeny tuber yield and its components were little different from those of the original dihaploid's progeny. Tuber flesh quality, as measured lack of blemishes, was better in the offspring of second generation dihaploids.

It is suggested that the negative effects of producing second generation dihaploids are minor compared with producing the first generation dihaploid from a tetraploid, because most deleterious recessives have already been unmasked. The results indicated residual variation within the original dihaploid which could be exploited for plant breeding purposes.

An indicator of inbred status, alternative to the inbreeding coefficient, is suggested which could be applied to both diploids and tetraploids.
Effects of activated charcoal effects on induction and development of microtubers in potato (Solanurn tuberosum L.)
Authors: BIZARRI M. , BORGHI L. , RANALLI P.
Published: February 2008

The aim of this research was to compare hormone‐free medium with media with regulator substances (activated charcoal, cytokinins, polyamine biosynthesis inhibitor and chlorocholine chloride) used for microtuber induction and development. Explants of cvs Monalisa, Primura and Spunta were multiplied subculturing nodal segments on plant growth regulator‐free Murashige & Skoog (1962) (MS) medium. When the plantlets had 6–8 nodes, single‐node stem segments were excised and transferred to eight tuberisation media, each consisting of MS basal components supplemented with sucrose (8% w/v) and various regulator substances. The control was a regulator‐free medium including only sucrose. Results were expressed as the number and weight of microtubers per nodal explant.

The cultivars showed wide variations in the mean weight of microtubers, ranging from 44.6 mg (Primura) to 77.5 mg (Spunta), and nearly all plants produced tubers. Medium containing activated charcoal gave the highest rate of tuberisation and the largest microtubers. It thus played a role in optimising conditions for rapid, mass tuberisation of these cultivars, and produced large microtubers for field planting.
Distribution and abundance of three species of Sitona (Coleoptera: Curculionidae) in grassland in England
Authors: MURRAY P. J. , CLEMENTS R. O.
Published: February 2008

The distribution and abundance of weevils of the genus Sitona was assessed at 16 sites in England. The sites were chosen to cover a wide range of geographical and agricultural regions. Adult weevils were sampled on four occasions, from May to August 1993. Numbers of adults, larvae and pupae were determined for each site on four occasions from June to September 1994. Numbers of larvae declined throughout the year in which they were sampled and pupae were most numerous in July. The population density of adults increased through the sampling period in both years. Sites close to pulse crops had the largest population levels of weevils, with Sitona lineatus L. the dominant species. No differences in the population levels of Sitona hispidulus (F.) or S. flauescens (Marsh.) were detected. Evidently populations of the latter two species are fairly constant in grassland and most of the variation in the population densities of these three species found in English grassland can be attributed to the migratory behaviour of S. lineatus and the proximity of pulse crops.
Partial application of insecticide to broad bean (Vicia fabae) as a means of controlling bean aphid (Aphis fabae) and bean weevil (Sitona lineatus)
Authors: WARD A. , MORSE S.
Published: February 2008

The effects upon the nature of insect pest attack of treating only a certain proportion (0%, 25%, 50%, 75% and 100%) of the plants in a field bean (Vicia fabae) stand, with a systemic insecticide (aldicarb as Temik 10G, Rhone Poulenc Drugs Ltd; 10% a.i.) were assessed. Numbers of both the black bean aphid (Aphis fabae) and the bean weevil (Sitona lineatus) were proportionally reduced on untreated plants in plots with an increasing proportion of insecticide treated plants. A similar response was also observed with bean weevil leaf damage scores.

It is postulated that the observed effects are due to a reduction in insect numbers per plot brought about by redistribution of insects after initial invasion. Insects initially alighting on untreated plants later migrate to treated plants and either die or leave the plot altogether. This resulted in proportionally fewer insects on the untreated plants than would be expected.
In vitro screening of coffee genotypes for resistance to coffee berry disease (Colletotrichum kahawae)
Authors: NYANGE N. E. , WILLIAMSON B. , McNICOL R. J. , HACKER CHRISTINE A.
Published: February 2008

An in vitro protocol was developed to screen Coffea arabica genotypes for resistance to coffee berry disease caused by Colletotrichum kahawae. Initially, cultural conditions which influenced the growth of isolates of C. kahawae on agar media suitable for callus growth were determined. The growth of the fungus on the callus derived from susceptible and resistant genotypes was then assessed. This ensured that no detrimental competition for nutrients between the pathogen and the calli occurred. Optimisation of the concentration of the phytohormones added to the media, the temperature and incubation period were found to be important in the expression of differential responses of calli to inoculation with the pathogen as detected by measurement of hyphal growth. The screening of calli of nine C. arabica genotypes showed that this method identified genotypes highly resistant or susceptible to the disease and was sufficiently sensitive to distinguish those genotypes with moderate or low resistance.
Assessing linseed (Linum usitatissimum) resistance to Alternaria linicola using a detached cotyledon assay
Authors: EVANS N. , McROBERTS N. , HITCHCOCK D. , MARSHALL G.
Published: February 2008

Levels of resistance to the seed‐borne pathogen Alternaria linicola in linseed and Linum accessions were characterised using an in vitro detached cotyledon bioassay. The response of four marketed varieties to seven isolates showed that differences between the isolates accounted for the majority of the variance. There was no significant interaction between varieties and isolates so that levels of response to the isolates showed a consistent trend. In a more comprehensive study, 102 different linseed and Linum accessions were challenged with an aggressive and a non‐aggressive isolate. Differences between accessions were significant (P > 0.001). Much of the material gave a moderate response to the two isolates although there was a continuous distribution of resistance from susceptible to resistant. The response of a sub‐set of tested material to the two isolates in a whole plant assay was positively correlated to the scores achieved in the in vitro bioassay, indicating that the resistance response of material could be predicted by the in vitro bioassay. Since large isolate‐line interactions with respect to resistance scores were not observed in either test, resistance appears to be polygenically determined. The results suggest that an improvement in the resistance of linseed to A. linicola would be possible and beneficial.
Evaluating between‐plant interference in field trials for assessing potato genotypes for resistance to late blight
Authors: CONNOLLY T. , McNICOL J. W. , WASTIE R. L. , STEWART HELEN E.
Published: February 2008

Field trials were done with four cultivars over 3 years to assess the extent to which the amount of late blight on the foliage of a potato plant could be influenced by that on a neighbouring plant of the same or a different cultivar. Drills containing the test plants were interspersed with those of spreader plants (cv. King Edward) which were artificially inoculated with Phytophthora infestans. The intensity of blight on the test plants was recorded on several occasions.

Resistant cultivars tended to be scored as less resistant in mixtures with other cultivars than in pure stands, and susceptible cultivars tended likewise to be scored as more resistant in mixed stands. However, standard analysis of variance indicated no systematic evidence of a significant effect due to neighbour cultivars, nor of interaction between cultivars and neighbour cultivars. In contrast, Kempton's (1982) neighbour model indicated a significant and positive interference coefficient (β) in each trial, which generally decreased over time. Predicted pure stand scores for each cultivar indicated that the adjustment was greatest for the most resistant and most susceptible cultivars. There was no advantage in using two‐plant rather than one‐plant plots in withstanding neighbour effects.
Evidence from the virobacterial agglutination test for the existence of eight serogroups of cocoa swollen shoot virus
Authors: HUGHES J. d'A. , ADOMAKO D. , OLLENNU L. A. A.
Published: February 2008

Many isolates of cocoa swollen shoot virus (CSSV) have been found in Ghana. Relationships between these isolates have been based on symptom expression and limited serological information. This paper reports on the serological relationships between 44 accessions of CSSV using the virobacterial agglutination test. The CSSV group is differentiated into eight groups using seven antibody ‘types’. The largest group comprising those isolates closely related to CSSV 1A is sub‐divided into four further groups. These groupings are compared with previous results. Differences are seen between accessions of the same isolate which may be due to contamination of the source plants. These serological results can be used for studying mixed isolate infections as well as for determining the most closely related CSSV mild isolate for appropriate cross‐protection against severe isolates.
Critical factors required by the nematode Steinernema feltiae for the control of the leafminers Liriomyza huidobrensis, Liriomyza bryoniae and Chromatomyia syngenesiae
Authors: WILLIAMS E. C. , MACDONALD O. C.
Published: February 2008

The critical factors required by entomopathogenic nematodes for the control of dipteran leafminers were investigated and compared. The foliar application of Steinernema feltiae and Heterorhabditis sp. (strain UK 211) caused a significant reduction in the numbers of dipteran leafminer larvae. There was no significant difference in efficacy between these nematode species against Liriomyza huidobrensis at 20°C and 85–90% r.h. Application of S. feltiae to all three larval instars of L. huidobrensis significantly reduced larval survival, with application to the second instar being the most effective at 20 ± 2°C and 80 ± 10% r.h. Humidities of >90% significantly enhanced the efficacy of S. feltiae. When S. feltiae was applied to second instar larvae, it was equally effective throughout the temperature range 10–30°C. At 20°C and >90% r.h., sufficient nematodes were able to enter the leaf tissues within the first 12 h after application to reduce larval survival to c. 15%. A comparison between L. huidobrensis, L. bryoniue and Chromatomyia syngenesiue indicated that the efficacy of S. feltiae was affected by the same critical factors for all three species.
Shelf‐life enhancement of fresh ginger rhizomes at ambient temperatures by combination of gamma‐irradiation, biocontrol and closed polyethylene bag storage
Authors: MUKHERJEE P. K. , THOMAS PAUL , RAGHU K.
Published: February 2008

The feasibility of a combination process involving gamma‐irradiation, packing in closed polyethylene bags and biological control of fungi causing storage rot was evaluated as a means of extending the shelf‐life of fresh ginger rhizomes at ambient temperatures (25–30°C). Storage in closed polyethylene bags reduced weight loss but increased sprouting and rooting, which could be prevented by gamma irradiation to 60 Gy. Rotting caused by Sclerotium rolfsii was, however, a major cause of spoilage during extended storage.

Four isolates of Trichoderma sp. isolated from sclerotia of S. rolfsii infecting ginger rhizomes, one of Gliocfadium uirens, and four isolates of fluorescent Pseudomonas were tested, out of which, one isolate of Trichoderma was found to be highly effective in suppressing the growth of S. rolfsii. The efficacy of the antagonist was demonstrated under simulated market conditions using artificially inoculated rhizomes. The recommended procedure consists of dipping washed, air dried rhizomes in Trichoderma suspension (108spores ml‐1), air‐drying, packing in 250 gauge LDPE bags followed by irradiation to 60 Gy. Rhizomes thus treated remained in good marketable condition for up to 2 months at ambient temperature without sprouting or significant loss of quality and less than 5% weight loss.

An in vitro bioassay system was developed to demonstrate the efficacy of the antagonist to protect the cut surface of sliced rhizomes inoculated with the pathogen. The method could be used for rapid screening of antagonists.
In vitro selection of Coffea arabica callus for resistance to partially purified phytotoxic culture filtrates from Colletotrichum kahawae
Authors: Nyange N E. , Williamson B. , McNicol R J. , Lyon G D. , Hackett Christine A.
Published: February 2008

Calli derived from hypocotyl explants of a susceptible and resistant genotype of Coffea arabica were evaluated for their response to different concentrations of partially purified culture filtrates (PPCFs) produced by Colletotrichum kahawae which are phytotoxic. The size of calli was measured non‐destructively by automated image analysis. Differential responses of calli ranged from complete necrosis or reduced growth in the susceptible genotype (N39) to an absence of necrosis and rapid growth in the resistant genotype (cv. Hybrido de Timor). Subsequently, one selection cycle in the presence of PPCF was devised and applied to calli of nine C. arabica genotypes. Normal plants were regenerated through somatic embryogenesis of callus lines that survived the phytotoxin treatment and in vitro and in vivo testing of these plants against the PPCF showed that increased resistance to the toxin had been obtained. These studies suggest that in vitro selection of calli may be a feasible approach to acquiring germplasm with improved resistance to coffee berry disease.
Genetics of resistance to Fusarium oxysporum f.sp. cucumerinum races 1 and 2 in cucumber line Wisconsin‐2757
Authors: Vakalounakis D J. , Smardas K.
Published: February 2008

The mode of inheritance of resistance to Fusarium oxysporum f.sp. cucumerinum races 1 and 2 in Wisconsin‐2757 (WI‐2757), a gynoecious cucumber (Cucumis sativus L.), was determined by analysing segregation of F1, F2 and BC1 populations of crosses with susceptible cultivar Straight‐8. Resistance to either race 1 or race 2 in WI‐2757 was conferred by a single dominant gene. In allelism tests, resistance to either race in WI‐2757 was determined by the gene Fcu‐1, which also confers resistance in line SMR‐18.
Occurrence of potato virus X strain group 1 in seed stocks of potato cultivars lacking resistance genes
Authors: Wilson C R. , Jones R A C.
Published: February 2008

Potato virus X (PVX) isolates were obtained from a simple seed potato production scheme or from ware potatoes produced by seed potatoes obtained from it. In this scheme, PVX infection is widespread in seed stocks and most of the potatoes grown lack PVX resistance genes. Thirteen PVX isolates were typed to strain group by inoculation to potato cultivars containing different combinations of hypersensitivity genes Nx and Nb. Six failed to overcome either gene and therefore belonged to strain group 1, four overcame Nb only and were placed in strain group 3 and three were mixtures of the two. All 13 isolates failed to overcome extreme resistance/immunity gene Rx. Naturally infected cultivars of genotype nx.nb contained strain group 1 alone or strain groups 1 and 3, while those of genotype nx:Nb contained only strain group 3. The widespread occurrence of strain group 1 contrasts with the predominant occurrence of strain group 3 in potatoes in the UK. However, it resembles the UK situation before sophisticated seed potato production schemes were introduced and before PVX hypersensitivity genes Nx and Nb were deliberately exploited in potato breeding. Prior infection with potato leafroll virus (PLRV) did not affect expression of hypersensitivity to PVX in inoculated leaves of an nx:Nb genotype.
Field evaluation of a tunnel sprayer and effects of spray volume at constant drop size on spray deposits and efficacy of disease control on apple
Authors: Cross J V. , Berrie A M.
Published: February 2008

An air assisted tunnel sprayer (the Noric Joco EX2) incorporating CDA rotary atomisers (Volume Median Diameter (VMD) =c. 140 μm, volume rate = 50 litre ha‐1 forward speed = 3.9 km h‐1) gave at best equal but in some cases significantly poorer control of apple powdery mildew and scab than the standard commercial practice of spraying with an axial fan sprayer with Micron XI rotary atomisers (VMD =c. 90 μm, volume rate = 50 litre ha‐1, forward speed = 7.2 km h‐1). Approximately 30% of the spray volume applied was collected for recycling with the tunnel sprayer. Increasing spray volumes at approximately constant drop size (c. 140 μm) from 50 to 100 to 200 litre ha‐1 with the tunnel sprayer consistently improved efficiency of mildew and scab control. Bulk spray deposits on leaves, and their gross distribution in the tree, was similar with the different spraying methods and volumes. The mean percentage leaf area covered with spray deposit increased with spray volume as did the number of spray deposits per unit area. The tunnel sprayer at 50 litre ha‐1 gave a similar though less variable mean level of cover than the axial fan sprayer at the same volume rate. It gave 2–3 times more cover on upper than on lower leaf surfaces. The axial fan sprayer gave approximately equal cover on upper and lower leaf surfaces.

The main limitations of the tunnel sprayer were its slow maximum forward speed and the restricted tree size and shape on which it can be used.
Chemical control of vine weevil larvae on container‐grown hardy ornamental nursery stock 1986–1989
Authors: Cross J V. , Buxton J H. , Jacobson R. , Richardson D M.
Published: February 2008

In a search for alternatives to the former standard aldrin compost incorporation treatment for control of vine weevil (Otiorhynchus sulcatus) larvae on container‐grown hardy ornamental nursery stock, a series of 87 tests of insecticides were done at four experimental centres of the ADAS (Leeds, Reading, Wolverhampton and Wye) from 1986 to 1989. Insecticidally‐treated plants and untreated controls were artificially infested with vine weevil eggs at varying intervals before and after treatment, and the survival of the pest was assessed. Aldrin treatment gave consistent and excellent preventive control of vine weevil larvae for over 2 years. Of the candidate materials tested, a slow‐release granular formulation of chlorpyrifos incorporated into compost at a dose rate of 100 g a.i. m‐3 of compost gave good control for up to 34 wk after treatment (the longest period evaluated) and a micro‐encapsulated slow release formulation of fonofos incorporated at a dose rate of 43.3 g a.i. m‐3 usually gave good control for up to two years (the longest period evaluated). Surface applications of these two organophosphates or of carbofuran granules, though sometimes effective, were unreliable as either preventive or remedial treatments even for short term control.
Tolerance of antibiotic and susceptible cereal seedlings to the aphids Metopolophium dirhodum and Rhopalosiphum padi
Authors: Lamb R J. , Mackay P A.
Published: February 2008

Some cereal seedlings exhibit antibiotic and antixenotic resistance to the aphids Metopolophium dirhodum (Walker) and Rhopalosiphum padi (L.), because the seedlings contain hydroxamic acids or gramine. The association between tolerance to aphids and aphid antibiosis was investigated for three cereals, Dollarbird wheat Vulcan wheat and Yagan barley. The dry biomass gained by the aphids and the simultaneous reduction in the biomass of the plants (biomass conversion ratio) quantified tolerance. Biomass production and the density dependence of biomass production by the aphids quantified antibiosis more effectively than fecundity. Vulcan wheat, which has more hydroxamic acid than Dollarbird wheat showed the highest level of antibiosis, and the barley was not antibiotic for either aphid. The biomass conversion ratio was a constant; the biomass of an infested plant was reduced by 3 mg for each mg of aphid biomass gained, regardless of aphid species, plant cultivar, or aphid density. The three plants showed no differential tolerance to the aphids, and therefore tolerance is not associated with antibiosis in this case.
Physiological determinants of genotypic differences in carbon isotope discrimination in potato grown in well‐watered conditions
Authors: Jefferies R A.
Published: February 2008

Carbon isotope discrimination (A), leaf conductance (gs), photosynthetic capacity, and plant growth were measured in well‐watered, glasshouse‐grown potato plants of clones from a cross made between diploid Solanum tuberosum and Solanum vernei. Clones showed significant differences (P < 0.001) in gs, Δ, stomatal density, root growth, and total dry matter production. Carbon isotope discrimination of genotypes was positively correlated (P < 0.001) with gs. There was no correlation between gs and stomatal density indicating that differences in gs reflected differences in stomatal aperture. Differences in rooting characteristics or in root/shoot ratio did not contribute to differences in gs or A. Genotypic differences in photosynthetic capacity were not statistically significant, and there was no correlation between A and photosynthetic capacity. Total dry matter production and A were positively correlated (P < 0.001) when differences in the time of plant emergence were included in the regression model.

It is concluded that differences in A among potato genotypes is largely determined by gs, but confounding of gs and photosynthetic capacity reduces genotypic variation in A compared with that in gs. Total dry matter production is largely determined by processes other than carbon assimilation rate per unit area in individual leaves. Effective use of A as a character for selection in plant breeding depends on elucidating the effects that differences in stomatal characteristics have on crop production both in well‐watered and in water‐limited crops.
A method to test compounds for feeding deterrence towards redlegged earth mite (Acarina: Penthaleidae)
Authors: Ridsdill‐Smith T J. , Jiang Y. , Ghisalberti E L.
Published: February 2008

A bioassay, based on a membrane sachet technique, has been developed to identify antifeeding compounds affecting the redlegged earth mite, Halotydeus destructor (Acari: Penthaleidae). The method consists of counting H. destructor numbers on membrane sachets in choice experiments, which was quicker and more efficient than weighing the mites. Five per cent aqueous glucose solution was used as a feeding stimulant, with Tween 80® at 5% concentration as a solubilising agent for water‐insoluble compounds. (+)‐Catechin, rutin, biochanin A, formononetin, chlorogenic acid, and gramine acted as feeding deterrents at 1% concentration. Quercetin (1 %) and azadirachtin (100 ppm) had no significant effect. At lower concentrations (0.01%), compounds showed antifeeding (gramine), phagostimulating (quercetin and chlorogenic acid), or no effects on mite numbers. Dose‐dependent deterrent effects of plant extracts were demonstrated with the bioassay, which could be used for other mites.
Detection of pineapple bacilliform virus using the polymerase chain reaction
Authors: THOMSON K G , DIETZGEN R G , THOMAS J E , TEAKLE D S
Published: February 2008

A polymerase chain reaction (PCR) assay has been developed to detect pineapple bacilliform virus (PBV) in extracts from infected plants. Initially, degenerate primers were designed from conserved badnavirus amino acid sequences and used in PCR with partially purified PBV preparations. A 448 bp DNA fragment was amplified from a region in the reverse transcriptase and ribonuclease H genes. The nucleotide sequence of the cloned PCR product indicated that PBV was related to, but distinct from, other badnaviruses. Specific primers designed from the PBV sequence yielded a 403 bp fragment when used in PCR with extracts from infected pineapple plants, but not from plants infected with sugarcane bacilliform or banana streak viruses (genus Badnavirus). The specificity of the PCR product was confirmed by Southern hybridisation using a digoxigenin labelled DNA probe. PBV appears to be present in all pineapple growing areas along the east coast of Australia. PBV was detected in plants grown from seeds, plants propagated through meristem tip culture and in mealybugs which were collected from infected plants. PBV was detected in crown, leaf and root tissue from infected pineapple plants. PCR results of all field‐infected samples were confirmed by immunoelectron microscopy.
Costs and benefits of hydroxamic acids‐related resistance in winter wheat against the bird cherry‐oat aphid, Rhopalosiphum padi L.
Authors: GIANOLI E. , PAPP M. , NIEMEYER H M
Published: February 2008

Estimations of infestation by the bird cherry‐oat aphid (Rhopalosiphum padi) as well as measurements of grain yield in 26 Hungarian winter wheat cultivars under field conditions were correlated with the concentration of hydroxamic acids (Hx) in seedlings of those cultivars. The significant inverse relationship between infestation ratings and Hx levels in wheat showed that Hx, despite their decreased accumulation at later plant phenological stages, may be able to confer resistance against aphid infestation in the field. Since no significant relationship was found between grain yield and Hx levels in plants it is suggested that Hx accumulation does not impose a cost to the plant in terms of yield. These findings support earlier claims stressing the potential of Hx as breeding targets for aphid resistance in wheat.