bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of the potato cyst nematode Globodera pallida on in vitro root growth of potato genotypes, differing in tolerance
Authors: ARNTZEN F K , VISSER J H M , HOOGENDOORN J
Published: February 2008

Roots of eighteen potato genotypes, differing in tolerance of G. pallida, were grown from tuberpieces on agar in Petri dishes. Juveniles of G. pallida were inoculated directly onto root tips. Root length was measured at various times after inoculation. Inoculation reduced root growth within one day. At later stages, genotypes differed strongly in growth of inoculated roots. Between four and seven days after inoculation, growth of inoculated roots was not significantly correlated with growth of untreated roots, and was only poorly correlated with tolerance assessed in the greenhouse or in the field. However, multiple regression analysis revealed that the tolerance of the tested genotypes was associated with both the rate at which they induced hatching and the growth of roots after inoculation. The combination of these two variables accounted for high percentages explained variance.
Leaf surface wetness in sorghum and resistance to shoot fly, Atherigona soccata: role of soil and plant water potentials
Authors: SOMAN P , NWANZE K F , LARYEA K B , BUTLER D R , REDDY Y V R
Published: February 2008

In experiments with potted plants, the relationships between soil matric potential, plant water potential and production of water droplets (leaf surface wetness) on the folded central whorl leaf of seedlings of sorghum genotypes that are either resistant or susceptible to shoot fly (Atherigona soccata) damage were investigated. Differences in soil matric potentials in the pots affected the plant water status, which in turn had profound effects on the production of water droplets on the central whorl leaf of the sorghum genotype susceptible to shoot fly. There was no consistent variation in the relationship between plant water potential and soil matric potential of resistant and susceptible sorghum genotypes. However, there was very little or practically no water droplets on the central whorl leaf of the resistant genotypes, indicating that the production of water droplets is not solely the result of internal water status of the plant. It is suggested that leaf surface wetness is genetically controlled and that an understanding of the mechanism by which water is transferred to the leaf surface will enhance breeding for resistance to shoot fly.
Genotype X environment interaction and simultaneous selection for high yield and stability in soybeans (Glycine max (L.) Merr.)
Authors: DASHIELL K E , ARIYO O J , OJO K
Published: February 2008

Eighteen genotypes of soybean were grown in five locations in Nigeria. The heritability estimates for seed yield were generally low, ranging from 22.6% to 45.3%. Joint regression analysis indicated the presence of genotype x environment, although a large proportion was non‐linear. The genotypes responded differently to environments, highlighting the possibility of breeding for specific environments.

The correlation of regression coefficients with mean yield indicated that high yielding genotypes were responsive to changing environments. The simultaneous selection parameters Pi, S3 and rank‐sums gave somewhat similar results but Pi produced higher yielding genotypes than others. The correlation between Pi and rank‐sum indicated that either of the techniques could be employed during selection.
Inheritance of resistance to lettuce root aphid in the lettuce cultivars ‘Avoncrisp’ and ‘Lakeland“
Authors: ELLIS P R , PINK D A C , RAMSEY A D
Published: February 2008

The inheritance of resistance in two lettuce cultivars to lettuce root aphid, Pemphigus bursarius, was studied in a series of laboratory and field experiments at Wellesbourne between 1989 and 1992. A source of total resistance in the cv. ‘Avoncrisp’ which is linked to the downy mildew resistance gene Dm6, was shown to be governed by a single dominant gene. There were no maternal effects evident in the inheritance of this resistance. The basis of the high level of resistance which exists in the cv. ‘Lakeland’ (formerly known as ‘Jubilee’) was also shown to be controlled by the same dominant gene. The linkage between Dm6 and root aphid resistance was broken in ‘Lakeland’ as this cultivar does not possess the Dm6 gene. The linkage was presumably broken when the original cross between the parents of cv. ‘Lakeland’, ‘Calmar’ and ‘Avoncrisp’ was made. Under laboratory conditions small numbers of aphids commence development on cv. ‘Lakeland’ but colonies fail to develop and under field conditions the resistance provides adequate Protectión against the pest. The resistance in both ‘Avoncrisp’ and ‘Lakeland’ was effective against a population of lettuce root aphid collected from an endive crop in southern France as well as being effective against the Wellesbourne population of this aphid.
Interactions between a seed‐borne strain of cucumber mosaic cucumovirus and its lupin host
Authors: GEERING A D W , RANDLES J W
Published: February 2008

The relationship between time of inoculation with cucumber mosaic cucumovirus (CMV) and the growth, seed production and rate of seed transmission of virus in lupin (Lupinus angustifolius cv. Illyarrie) was studied in field‐grown plants. Plants inoculated at the seedling stage (2 days post‐emergence) showed 45% mortality. Plants infected through the seed were more stunted than plants inoculated at the seedling stage. Plants inoculated up to the mid‐vegetative growth stage (58 days post‐emergence) yielded ≤ 27% of the dry matter and ≤ 9% of the seed of healthy plants. Late inoculation (114 days post‐emergence) did not affect dry matter yield, but reduced seed yield to 75% of that of healthy plants. Rate of seed transmission depended on the time of inoculation of plants. The maximum rate was 24.5% for plants that were inoculated at the mid‐vegetative growth stage (58 days post‐emergence). However, early inoculation caused a large reduction in seed yield, and it was shown that plants inoculated at the beginning of flowering (94 days post‐emergence) produced greater numbers of infected progeny than plants inoculated at earlier or later times. No relationship was observed between seed weight and transmission of CMV. Infectious CMV was recovered from the embryo, but not from the testa.

A simple seed transmission model was used to evaluate several hypothetical epidemics and to determine the time of inoculation which results in greatest rates of seed transmission of CMV. For example, when fewer than 73% of plants in a crop become infected with CMV, then the rate of transmission of virus in crop seeds will be greatest when inoculations are at the beginning of flowering.
Field resistance in maize cultivars to stem borer Chilo partellus
Authors: KUMAR HARISH
Published: February 2008

The Kenyan maize varieties, Hybrid 511, Hybrid 622, Pwani hybrid, Katumani Composite B, and local populations were evaluated along with the varieties of Multiple Insect‐Resistant Tropical (MIRT) pool and experimental varieties from The Maize and Wheat Improvement Centre (CIMMYT), Mexico for resistance to the stem borer, Chilo partellus (Swinhoe). The artificial infestation by first‐generation C. partellus on maize during the early whorl stage revealed that the leaf feeding damage, the dead heart formation, and the stem damage on the Kenyan hybrids and populations were significantly greater than on the MIRT varieties. The experimental varieties of CIMMYT were also susceptible to C. partellus. When the maize was infested at anthesis, the Kenyan varieties displayed a moderate level of resistance in terms of stem tunnelling and grain damage by C. partellus. The varieties of Multiple Insect Resistance Tropical pool can be effectively used by the breeders to enhance the resistance of agronomically good, but susceptible, varieties of Kenya.
Breeding for partial resistance in dry beans (Phaseolus vulgaris) to bean rust (Uromyces appendiculatus)
Authors: EDINGTON B R , SHANAHAN P E , RIJKENBERG F H J
Published: February 2008

Significant differences in susceptibility of 23 bean cultivars were found after natural infection by a single‐pustule isolate of bean rust in field trials over three seasons. These differences were not related to differences in the number of adaxial or abaxial acicular leaf hairs, latent period in primary leaves or a difference in pustule size. Forty‐five large‐seeded bean lines with partial resistance to a single‐pustule isolate were developed by recurrent selection for commercial evaluation.
Antixenosis component of resistance to sorghum midge, Contarinia sorghicola Coq. in Sorghum bicolor (L.) Moench
Authors: SHARMA H C , VIDYASAGAR P
Published: February 2008

Sorghum midge, Contarinia sorghicola Coq. (Diptera: Cecidomyiidae) is the most destructive pest of grain sorghum, and host‐plant resistance is an effective method of controlling this insect. We studied the antixenosis component of resistance to sorghum midge using multi‐, double‐ and no‐choice cage tests, and under multi‐choice field conditions to quantify and understand the nature of antixenosis component of resistance to this insect in Sorghum bicolor (L.) Moench. Midge response towards sorghum panicles was influenced by panicle size and cage type used to study the orientation behaviour. Maximum number of midges were recorded at 30 and 60 min after initiating the experiment. Antixenosis shown by C. sorghicola under multi‐choice field conditions to ICSV 197 and TAM 2566 was not confirmed under cage tests, while DJ 6514, AF 28 and IS 3461 were non‐preferred both under field and cage conditions. Midge‐resistant female parents (PM 7061 and PM 7068) were less preferred than the midge susceptible (ICSA 42 and 296A) female parents. Male‐sterility did not influence host finding and acceptance by the midge females, although in one out of two tests, the maintainer lines (B‐lines) were preferred over the male‐sterile lines (A‐lines).
Glasshouse‐based selection to identify agronomically adapted, uniform true potato seed (TPS) progenies
Authors: CLULOW S A , BRADSHAW J E
Published: February 2008

Twenty‐five true potato seed progenies and five clonally maintained cultivars were grown in a glasshouse. Tubers of each clone of each progeny were grown in a field experiment. At harvest, one seed tuber was taken from each plant and field grown for a second year. After each experiment, the tubers from every plant were weighed and counted and their colour, shape, form (regularity) and skin finish assessed. Progeny means and variances for each character were calculated. There were significant differences between means for each character in all experiments, except mean yield in the glasshouse, variances for each character in both field experiments and tuber number variances and colour variances in the glasshouse. In general, Pearson's product‐moment correlations between glasshouse and field assessments were moderate or poor (r ≤ 0.6) and inconsistent between experiments. Spearman's rank correlations between glasshouse and field assessments for progeny means were similar to the linear correlations, while those for variances were somewhat better. Rank correlation gave more consistent results between experiments. Ranking glasshouse means will allow some worthwhile progeny selection for tuber colour, shape and skin finish. It can be a useful screen for progenies with the highest levels of uniformity for all characters.
Effect of light on DIMBOA‐glucoside concentration in wheat {Triticum aestivum L.)
Authors: ÅHMAN I , JOHANSSON M
Published: February 2008

DIMBOA (2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one) glucoside in wheat has been suggested to play a role in plant resistance to cereal aphids. Thus there is considerable interest in trying to breed modern wheat varieties with increased concentrations of this compound. To further such work we assessed the effects of light intensity on DIMBOA glucoside production in wheat seedlings under both indoor and outdoor conditions. Light had a marked effect on DIMBOA‐glucoside concentrations, with levels in plants being negatively related to light intensity. Our findings suggest that breeding aimed at increasing levels of DIMBOA‐glucoside would be most effective if test plants for selection were to be grown under weak light conditions.
Properties of cocksfoot streak and cocksfoot cryptic, two viruses infecting cocksfoot (Dactylis glomerate) in Scotland
Authors: TORRANCE LESLEY , JONES A T , DUNCAN G H
Published: February 2008

A Scottish isolate of cocksfoot streak virus (CSV‐S) was found to have flexuous filamentous particles which, in sap of infected cocksfoot plants, had a modal length of 712 nm. It was transmitted from infected to healthy cocksfoot plants in a non‐persistent manner by Myzus persicae and by mechanical inoculation of infective sap extracts containing an anti‐oxidant. Apart from cocksfoot, mechanical inoculation of infective sap succeeded in infecting only four of 22 plant species tested. The infectivity of sap extracts containing 0.2% thioglycerol was lost after heating for 10 min at 55oC but not 50oC, storage at room temperature for 48 but not 24 hours, and after diluting 10‐2 to 10‐3. Highly purified preparations of CSV‐S particles sedimented as a single component with a sedimentation coefficient of 139S and had a buoyant density in rubidium bromide of 1.31 g/cm3. Virus particles were composed of one protein and one ssRNA species with estimated Mr of 31 000 and 3.2 times 106 respectively. In ELISA, an antiserum prepared to CSV‐S detected the virus in all aerial parts of infected cocksfoot plants and, when present in the ratio of 1 infected leaf: 1000 healthy leaves. Both CSV‐S‐infected and ‐uninfected cocksfoot also contained a previously undescribed virus with isometric particles c. 30 nm in diameter. This virus, named cocksfoot cryptic virus (CCV), was seed‐borne in two cvs of cocksfoot tested and its particles contained two dsRNA species of estimated Mt of 1.14 times 106 and 1.27 times 106. Despite the fact that particles of CSV‐S were largely free from CCV particles following exclusion chromatography on agarose beads prior to immunisation, immunoelectron microscopy (IEM) showed that the antiserum prepared to CSV‐S also contained some antibodies to CCV. Evidence from IEM suggested a possible distant serological relationship of CCV to ryegrass and beet (BCV 1 or BCV 2, or both) cryptoviruses, all members of sub‐group A of cryptoviruses.
A comparison of the flora and arthropod fauna of organically and conventionally grown winter wheat in southern England
Authors: MOREBY S J , AEBISCHER N J , SOUTHWAY S E , SOTHERTON N W
Published: February 2008

Fields of winter wheat on organic and conventional farms were sampled for weeds and invertebrates in June/July in 1990 and 1991. Organic fields were paired with adjoining conventional ones and their invertebrate fauna compared with a D‐vac vacuum suction sampler. Weed counts showed greater percentage cover of broad‐leaved weeds in organic fields than in conventional ones, with three times as many species present where herbicides were not used.

Significantly higher densities of nematoceran and acalypteran Diptera, Hem‐iptera (especially aphids), aphid‐specific predators, parasitic Hymenoptera and cryptophagid and cantharid Coleoptera were found in conventionally grown fields. Significantly higher densities of weevils, spiders, springtails, plant hoppers and sawfly larvae were found in organic fields. Reasons for these differences or the lack of them are discussed.
Serological characterisation of citrus tristeza virus isolates from Israel
Authors: SHALITIN D , MAWASSI M , GAFNY R , LEITNER O , CABILLY S , ESHHAR Z , BAR‐JOSEPH M
Published: February 2008

Seven monoclonal antibodies (MAbs) showing homologous reactions with the VT strain of citrus tristeza virus (CTV) were tested against 21 CTV strains or isolates, representing the range of biological diversity and the geographical distribution of CTV in Israel. All the CTV strains gave positive reactions in ELISA with polyclonal antibodies and with one MAb (#25#2). Two MAbs; #13#21 and #3/7 reacted with 19 and 12 out of the 21 CTV strains, respectively. Seventeen CTV strains, including all those previously assigned by sequencing their coat protein gene (CPG) to the CPG‐VT group (Mawassi, Gafny & Bar‐Joseph, 1993), reacted with five or more MAbs. Four CTV strains of minor epidemiological importance, including two members of the CPG‐MT group, did not react with five or more of the MAbs.

These results indicated the existence of two serogroups of Israeli CTV strains that can be differentiated by MAbs and which closely correlate with and extend the previous CPG grouping. The extensive biological variation within each CPG group confirms recent analyses suggesting that the CTV pathogenic traits are not necessarily associated with a sequence or antigenic variation of the CTV‐CPG.
Serological relationships among rice yellow mottle virus isolates
Authors: MANSOUR A N , BAILLIS K W
Published: February 2008

Serological studies on five isolates of RYMV collected from the Ivory Coast (IC), Sierra‐Leone (SL), Niger (Nr), Kenya (K) and Nigeria (N) indicated that these isolates are serologically related. Gel double diffusion and direct ELISA tests showed that the five isolates could be arranged into three serological groups here designated RYMV‐N, SL‐IC and K‐NR. However, the ISEM studies did not reveal any clear grouping of the heterologous isolates tested.
The effects of temperature on the availability and acquisition of potato leafroll luteovirus by Myzus persicae
Authors: SYLLER J
Published: February 2008

The concentration of potato leafroll luteovirus (PLRV) did not differ in potato plants with secondary infections grown at 15°C or 27°C. Detached leaves of plants grown at 15°C or 27°C were used as sources of PLRV for peach‐potato aphids (Myzus persicae Sulz.) both at 15°C and 27°C. At comparable temperature during virus acquisition, aphids which fed on leaves of plants kept previously at 15°C contained more viral antigen detected by ELISA than aphids which fed on leaves of plants grown at 27°C. The aphids which acquired PLRV at 27°C contained evidently more viral antigen than those which acquired PLRV at 15°C. The greatest amount of PLRV was found in the aphids which acquired the virus at 27°C from the leaves of plants kept at 15°C. The ability of M. persicae to transmit PLRV to Physalis ftoridana Rydb. generally decreased with decrease in the amount of PLRV in vectors.
The freezing characteristics of cauliflower curd
Authors: FULLER M P , WHITE G G , CHARMAN A
Published: February 2008

Cultivar differences in frost resistance and the heritable nature of resistance were demonstrated using seedling cauliflower plants. Such cultivar differences were not however expressed in the curd. Selection for frost resistance in cauliflower should therefore use whole plant screening techniques.

Curd material when frozen as isolated florets, supercooled over the range – 1°C to – 12°C and the mean freezing point of all curds tested was ‐6°C to ‐7.25°C (overall mean ‐6.44°C). Curd florets which supercooled but did not freeze were completely undamaged, whereas freezing always led to cell damage and death observed as water‐soaking of the floret surface and measured using an electrical conductivity method. The large range of freezing points measured suggests a range of active ice nucleators either on or within the florets. When curds were frozen intact the ability of florets to supercool was severely restricted which was attributed to the seeding of freezing by the internal growth of ice crystals. A crop protection strategy needs to identify and control or modify warm temperature nucleators in cauliflower curd.
Bio‐activity of marine cyanobacteria in the animal‐based systems: Modulation of food intake, body weight and some haematological characters
Authors: SUNDARARAMAN M , AVERAL H I , AKBARSHA M A , SUBRAMANIAN G
Published: February 2008

With a view to assess the bioactive potential of the unexploited marine cyanobacteria available in abundance in the marine habitat, water‐soluble fraction of the ethanolic extract of 12 different strains of marine cyanobacteria were administered to male rats and their impact on food intake, body weight and certain haematological characters including RBC counts, WBC‐TC and DC, platelet counts, haemoglobin content and mean corpuscular haemoglobin was studied. The results suggest prospective applications as feed/nutritional supplements; among them, Spirulina subsalsa BDU 30311, Oscillatoria salina BDU 10142 and Phormidium valderianum BDU 20571 appear highly promising in this regard. Lyngbya sp. BDU 30601 and Pseudanabaena schmidlei BDU 30313 appear to contain one or more toxins and deter food intake and cause decrease in body weight. With Synechococcus elongatus BDU 30312 food intake increased over the control which was not commensurate with the change in body weight. The results relating to the haematological characters indicate bioactivity of the cyanobacteria in the animal‐based systems, some of which are positive, whereas a few strains like Lyngbya BDU 30601 are negative, implying their pharmaceutical application.
Resistance in sorghum to shoot fly Atherigona soccata: Evidence for the source of leaf surface wetness
Authors: SIVARAMAKRISHNAN S , SOMAN P , NWANZE K F , REDDY Y V R , BUTLER D R
Published: February 2008

Leaf surface wetness (LSW) of the central whorl leaf of sorghum seedlings has been associated with susceptibility to shoot fly. Previous physical and physiological evidence suggested that LSW originates from the plant. This was confirmed by radioactive labelling methods using tritium and carbon‐14. Tritiated water applied to the soil of potted seedlings was translocated to the surface of the whorl leaf. There were significant differences in the amount of tritiated water collected from susceptible (CSH 5) and resistant (IS 18551) genotypes. Studies with carbon‐14 labelling of sorghum seedlings indicated the presence of (small amounts of) solutes in the surface water that may affect larval movement and survival.
Development and reproductive potential of the cereal aphid Sitobion avenae on resistant wheat lines (Triticum monococcum)
Authors: CAILLAUD CLAUDIA M , DEDRYVER C A , SIMON J C
Published: February 2008

The effect of wheat resistance in lines of Triticum monococcum L., on the reproductive performances of the cereal aphid (Sitobion avenae F.) was investigated. Aphids were reared from birth to adult moult either on resistant or susceptible wheat lines, and transferred as apterae to both host genotypes. The influence of these transfers on the subsequent adult weight, gonad status and reproductive performances was evaluated.

Aphids transferred from resistant to susceptible plants proved able to compensate for their poor nymphal growth, mainly through additional embryo growth and an increase in the number of matured embryos within the first 10 days of their adult life. Most aphids transferred from susceptible to resistant plants died within the first week following the transfer. Their most advanced embryos matured and were born, but subsequent embryo growth was quickly reduced.

The reproductive strategies adopted by S. avenae when facing plant resistance, and the hypothesis of a resistant mechanism based on a poor nutritional state of the resistant plants are discussed.
Biochemical characterisation of Pythium spp. involved in cavity spot of carrots in France
Authors: GUÉRIN LUCIA , BRIARD MATHILDE , ROUXEL FRANCIS
Published: February 2008

The pathogenicity and growth rate in vivo were assessed on 27 isolates of Pythium spp. recovered from cavity spot lesions on carrots grown in various parts of northwest France. Polyacrylamide gel electrophoresis of isoesterases was used to identify the Pythium spp. involved.

Slow‐growing isolates were more aggressive than fast‐growing ones when inoculated on carrot tap roots. Isoesterase patterns identified the slow‐growing isolates as P. violae and P. sulcatum; P. ultimum and P. intermedium were identified among the less aggressive fast‐growing isolate group, in which some isolates were also classed as P. sylvaticum or P. irregulare, which have similar electrophoretic profiles.

The incidence of Pythium spp. associated with the disease in France is discussed in regard to cavity spot in other countries.
Sources of crown rot (Phytophthora cactorum) infection in strawberry and the effect of cold storage on susceptibility to the disease
Authors: PETTITT T R , PEGG G F
Published: February 2008

Cold‐stored plants of strawberry cultivars Tamella, Cambridge Favourite and Redgauntlet were more susceptible to pathogenic isolates of Phytophthora cactorum than similar plants which had not been cold‐stored. Indigenous nonpathogenic isolates of P. cactorum did not cause crown rot in cold‐stored plants, although a small number of symptomless latent infections occurred. The majority of P. cactorum isolates causing crown rot symptoms were taken from infected strawberry crowns, although two isolates from gooseberry plants, but of uncertain origin, were also pathogenic. Outbreaks of crown rot in areas with no previous history of the disease therefore probably result from the importation of non‐indigenous inoculum with planting material.

Assessments of the timing of infection in relation to cold storage revealed that a high incidence of death in the cold store and chronic wilt symptoms on planting from the store resulted from initiating symptomless infections prior to cold storage. However, infection during the period immediately after cold storage resulted in rapid wilt symptoms of Phytophthora crown rot. When plated in sterile distilled water for 24 h, pieces of tissue from infected plants which had died during cold storage produced large numbers of sporangia and zoospores. This indicates that such plant material could provide a potent source of inoculum for infections in the post storage thawing environment. It is proposed that a combination of heightened host susceptibility resulting from cold storage and the presence of scatted latent infections or infected debris among the plants could result in a sudden, large scale appearance of crown rot, as sometimes is seen with cold‐stored plantings of strawberries.
Geminivirus transmission and biological characterisation of Bemisia tabaci (Gennadius) biotypes from different geographic regions
Authors: BEDFORD I D , BRIDDON R W , BROWN J K , ROSELL R C , MARKHAM P G
Published: February 2008

Eighteen populations of Bemisia tabaci, collected from different geographic locations (North & Central America, the Caribbean, Africa, the Middle East, Asia and Europe), were studied to identify and compare biological and genetic characteristics that can be used to differentiate biotypes. The morphology of the fourth instar/pupal stage and compound eye structures of adults were investigated using scanning electron microscopy and found to be typical of the species among all biotypes and populations studied. Setae and spines of B. tabaci larval scales from the same colony were highly variable depending on the host plant species or leaf surface characteristics. The location and the morphology of caudal setae, characteristic of all B. tabaci studied to date, were present in all colonies. However, differences in adult body lengths and in the ability to induce phy to toxic disorders in certain plant species were found between biotypes or populations. The recently identified “B” biotype, characterised by a diagnostic esterase banding pattern and by its ability to induce phytotoxic responses in squash, honeysuckle and nightshade was readily distinguished from non‐“B” biotype populations. None of the non‐“B” biotypes studied, were found to induce phytotoxic responses. Nine populations examined showed typical “B” biotype characteristics, regardless of country of origin. All tested populations, determined as “B” or “B”‐like biotypes successfully mated with other “B” biotype colonies from different geographic areas. Non‐“B” biotype colonies did not interbreed with other biotypes.

The B. tabaci populations were tested for their ability to transmit 15 whitefly‐transmitted geminiviruses (WTGs) from different geographic areas with a wide range of symptom types. All WTGs were transmitted by the “B” biotype colonies and by most non‐“B” biotype colonies, with the exception of three viruses found in ornamental plants which were non‐transmissible by any colony. Some non‐“B” biotypes would not transmit certain geminiviruses and some geminiviruses were more efficiently transmitted than were others.
Biological control of slugs in winter wheat using the rhabditid nematode Phasmarhabditis hermaphrodita
Authors: WILSON M J , GLEN D M , GEORGE S K , PEARCE J D , WILTSHIRE C W
Published: February 2008

A field experiment on winter wheat in autumn 1991 investigated the effect of the rhabditid nematode, Phasmarhabditis hermaphrodita, applied to soil at five dose rates (108 ‐ 1010 infective larvae ha‐1) immediately after seed sowing, on slug populations and damage to seeds and seedlings. The nematode was compared with methiocarb pellets broadcast at recommended field rate immediately after drilling and no molluscicide treatment. Slug damage to wheat seeds and seedlings was assessed 6 and 13 wk after drilling. Seedling survival increased and slug grazing damage to seedlings declined linearly with increasing log nematode dose. These two measures of slug damage were combined to give an index of undamaged plant equivalents, which also increased linearly with increasing log nematode dose. ANOVA showed that, after 6 wk, there were significantly more undamaged plant equivalents on plots treated with the two highest nematode doses (3 × 109 and 1 × 1010 ha‐1) than on untreated plots, but the number of undamaged plant equivalents on methiocarb‐treated plots was not significantly greater than that on untreated plots. Slug populations were assessed by refuge trapping and soil sampling. Deroceras reticulatum was the commonest of several species of slugs recorded. During the first 4 wk after sowing, significantly more slugs were found under refuge traps on plots treated with certain doses of P. hermaphrodita than under traps on untreated plots and more showed signs of nematode infection than expected from the prevalence of infection in slugs from soil samples, suggesting that the presence of P. hermaphrodita altered slug behaviour. Application of P. hermaphrodita had no significant impact on numbers or biomass of slugs in soil during a 27 wk period after treatment, except after 5 wk when slug numbers were inversely related to log nematode dose. However, by this time, numbers in soil samples from untreated plots had declined to levels similar to those in plots treated with the highest dose of nematodes. During the first 5 wk after treatment, c. 20% of slugs in soil samples from untreated plots showed symptoms of nematode infection. It is suggested that this represented the background level of infection in the experimental field rather than spread of infection from treated plots. The apparent lack of impact of P. hermaphrodita on slug numbers and biomass in soil suggests that its efficacy in protecting wheat from slug damage was through inhibition of feeding by infected slugs.
Bio‐assay study of response by a parasitoid to frass and feeding substrates of its host, the stalk borer Eldana saccharina
Authors: SMITH G S , ALLISON J C S , PAMMENTER N W
Published: February 2008

In Petri dish and olfactometer tests Goniozus natalensis Gordh (Hymenoptera: Bethylidae) exhibited a host‐searching response upon contact with, and at a short distance from, frass of its natural host, Eldana saccharina Walker (Lepidoptera: Pyralidae), whichever the substrate on which E. saccharina had been feeding. The substrates were two host plants, sugarcane or Cyperus papyrus L.; diet media based respectively on sugarcane, papyrus, or cellulose; or a synthetic diet medium, containing no plant material. Host‐searching behaviour increased in intensity with age and after mating of G. natalensis females. Parasitoids responded similarly to frass produced by male and female E. saccharina larvae. The substrates themselves elicited little response in G. natalensis. Frass of another borer, Sesamia calamistis Hamps. (Lepidoptera: Noctuidae), fed on sugarcane‐based medium, also elicited little response in G. natalensis. The results suggest that frass of E. saccharina larvae contains a material, evidently volatile, to which their parasitoid G. natalensis responds, irrespective of the substrate on which the E. saccharina subsist.
An investigation of the resistance to cabbage aphid in brassica species
Authors: SINGH R , ELLIS P R , PINK D A C , PHELPS K
Published: February 2008

Fifteen Brassica species and subspecies, as well as accessions of Arabidopsis thaliana and Eruca sativa, were evaluated for their resistance to the cabbage aphid, Brevicoryne brassicae, in the field and laboratory at Horticulture Research International (HRI) Wellesbourne in 1992. In the laboratory, aphid performance was measured in terms of pre‐reproductive period, reproductive period, population increase and insect survival. Using these parameters it was possible to identify brassicas possessing antibiosis resistance. In the field B. brassicae attack was assessed in terms of numbers of insects and it was possible to determine aphid preferences for alighting on different species. High levels of antixenosis and antibiosis resistance were discovered in accessions of Brassica fruticulosa and B. spinescens, in a Brassica juncea breeding line and in Eruca sativa. Partial resistance was found in several other Brassica species. The potential of these various sources as donors of resistance genes to be bred into cultivated brassicas is discussed.
Effect and interaction of temperature and photoperiod on growth and partitioning in three groundnut (Arachis hypogaea L.) genotypes1
Authors: NIGAM S N , RAO R C NAGESWARA , WYNNE J C , WILLIAMS J H , FITZNER M , NAGABHUSHANAM G V S
Published: February 2008

Effect of temperature and photoperiod and their interaction on plant growth and partitioning of dry matter to pods was examined in three selected groundnut genotypes viz., TMV 2, NC Ac 17090 and VA 81B. The genotypes were grown in six walk‐in growth chambers which were programmed to simulate three temperature regimes (22/18°C, 26/22°C and 30/26°C day/night) each under long (12 h) and short (9 h) photoperiods. The plant growth rates and partitioning of dry matter to pods were estimated on a thermal time basis.

Plant growth rate (PLGR) was significantly influenced by temperature, photoperiod and genotype, whereas pod growth rate (PDGR) was influenced primarily by temperature and genotype. The interaction of genotype with photoperiod and with temperature was significant for both PLGR and PDGR. For example, at the 22/18°C temperature regime, VA 81B had a high PDGR, while NC Ac 17090 did not even initiate pod growth. The partitioning of dry matter to pods (Pf) was also significantly influenced by photoperiod, temperature and genotype, and significant interactions were found. Photoperiod did not significantly affect Pf under the low temperature regime, but at higher temperatures, partitioning to pods was significantly greater under short days. Pf of VA 81B was relatively insensitive to photoperiod compared with the other two genotypes. The study provided evidence of genotypic variability for photoperiod × temperature interactions which could influence adaptation of groundnut genotypes to new environments.
A study by cryo‐scanning electron microscopy of the initiation and early development of an inflorescence in glasshouse celery (Apium graveolens L. var. dulce (Miller) Pers.) grown under inductive conditions
Authors: ROELOFSE E W , ATKEY P T , HAND D W , HALL R L
Published: February 2008

The morphology of flower initiation and early development in glasshouse celery (Apium graveolens L. var. dulce (Miller) Pers.) cv. Celebrity was studied by means of apical dissections and cryo‐scanning electron microscopy. Easily recognisable morphological features were used to define seven stages in the early development of the inflorescence. A highly significant linear regression was established between the logarithm of the apical diameter (measured diametrically across the apical dome between the two most recently initiated leaf or inflorescence primordia) and these discrete floral stages. There was no strong evidence that either the origin or the slope of the regression varied with different combinations of temperature (viz. 10°C or 14°C) and daylength (viz. natural, short or long) which were conducive for the initiation and development of an inflorescence. It is suggested that both apical diameter and floral stage may be used as parameters for assessing the influence of environmental factors such as temperature and daylength on the floral development of glasshouse celery.
Nuclear DNA content of the Solanum spp. in the series Etuberosa as determined by laser flow cytometry
Authors: VALKONEN JARI P T
Published: February 2008

Nuclear DNA content was determined in three accessions of Solanum brevidens, three accessions of S. etuberosum, and one accession of S. fernandezianum, which are diploid (2n = 2×= 24), closely related, non tuber‐bearing wild potato species belonging to the series Etuberosa (Solanaceae). The plants were grown in vitro at 18°C or at 25°/22°C (day/night). S. brevidens was also grown in soil in the glasshouse at 25°/19°C (day/night), and in growth chambers at 18°C or 32°C. Leaf nuclei were isolated using a chopping method and stained with propidium iodide. Chicken red blood cells (CRBC; 2.33 pg) were added to the samples of nuclei as internal standards. The fluorescence of plant nuclei relative to CRBC was measured with an EPICS PROFILE flow cytometer. The 2C values of in vitro‐grown S. brevidens and S. etuberosum were similar (1.48–1.54 pg, depending on the accession), but they were smaller than the 2C value of S. fernandezianum (1.63 pg). The 2C values of S. brevidens and S. etuberosum were generally smaller than those of the diploid species S. berthaultii (1.60–1.61 pg) and the diploid clones of S. tuberosum (1.60–1.72 pg). A similar relative difference of nuclear DNA content was found also between tetraploid S. brevidens and tetraploid S. tuberosum (2C = 3.15–3.16 pg and 3.50–3.62 pg, respectively). High (32°C) and low (18°C) growth temperatures caused abnormal changes in morphology and reduced fertility in S. brevidens in the growth chamber. The 2C values of S. brevidens grown at 25°/19°C (day/night) or at 32°C were similar, whereas the 2C values were c. 10% lower at 18°C.
Aerial flow of barley yellow dwarf viruses and of their vectors in western France
Authors: QUILLEC FRANÇOISE LECLERCQ‐LE , TANGUY SYLVIE , DEDRYVER C A
Published: February 2008

During the years 1989–1992 cereal aphids were caught alive in a low level (1.5 m high) suction trap operated in Le Rheu (Brittany, France) and tested for BYDV transmission. In most cases comparisons with data collected simultaneously by a 12.2 m suction trap operating in the same site resulted in good relationships between weekly catches at both heights.

Results from transmission tests showed that: (i) the two main BYDV vectors were Rhopalosiphum padi and Metopolophium dirhodum during the years of experiment; (ii) PAV and MAV were the commonest viruses and RPV was relatively scarce; (iii) during spring M. dirhodum appeared to be the most important MAV vector and nearly as good a PAV vector as R. padi; (iv) during autumn R. padi was the only vector of the three viruses with mixed transmission allowing it to transmit also MAV probably by heteroencapsidation. To give an indication of the risk of infection, infectivity indices were calculated by multiplying the numbers of aphids caught by the 12.2 m suction trap by the proportion that were infective. These infectivity indices agreed with field records of primary infections.
Localisation of plum pox virus in apricot stem and petiole tissues by tissue printing onto nitrocellulose membrane
Authors: DICENTA F , AUDERGON J M
Published: February 2008

The localisation of plum pox virus (PPV) in stem and petiole tissues of nine susceptible apricot cultivars and GF305 peach seedling has been studied. From stem and petioles consecutive transverse sections spaced at 1 mm were made and tissue sections printed onto nitrocellulose membrane. The resulting prints were probed with a specific antibody for plum pox virus, followed by a rabbit anti‐goat antibody conjugated with horse radish peroxidase, in order to localise the virus within the tissues. In stems the virus was mainly present in xylem and pith. The possible presence of the virus in the sclerenchyma is discussed. In petioles the virus was present in epidermis and parenchymas, but not in vessels. The probable movement through the xylem and from cell to cell has been shown.
Occurrence of whitefly‐transmitted geminiviruses in crops in Burkina Faso, and their serological detection and differentiation
Authors: KONATÉ G , BARRO N , FARGETTE D , SWANSON M M , HARRISON B D
Published: February 2008

Whitefly‐transmitted geminiviruses were found to be associated with four diseases of crop plants in Burkina Faso: cassava mosaic, okra leaf curl, tobacco leaf curl and tomato yellow leaf curl. Tomato yellow leaf curl is an economically serious disease, reaching a high incidence in March, following a peak population of the vector whitefly, Bemisia tabaci, in December. Okra leaf curl is also a problem in the small area of okra grown in the dry season but is not important in the main period of okra production in the rainy season. The geminiviruses causing these four diseases, African cassava mosaic (ACMV), okra leaf curl (OLCV), tobacco leaf curl (TobLCV) and tomato yellow leaf curl (TYLCV) viruses, were each detected in field‐collected samples by triple antibody sand‐wich‐ELISA with cross‐reacting monoclonal antibodies (MAbs) to ACMV. Epitope profiles obtained by testing each virus isolate with panels of MAbs to ACMV, OLCV and Indian cassava mosaic virus enabled four viruses to be distinguished. ACMV and OLCV had similar but distinguishable profiles. The epitope profile of TobLCV was the same as that of one form of TYLCV (which may be the same virus) and was close to the profile of TYLCV from Sardinia. The other form of TYLCV reacted with several additional MAbs and had an epitope profile close to that of TYLCV from Senegal. Only minor variations within each of these four types of epitope profile were found among geminivirus isolates from Burkina Faso. Sida acuta is a wild host of OLCV.
Double kerneled fruits in almond (Prunus dulcis Mill.) as related to pre‐blossom temperatures
Authors: EGEA J , BURGOS L
Published: February 2008

A ten year study on the influence of pre‐blossom temperatures on the percentage of double kerneled almond fruits, under warm climatic conditions, showed a negative correlation between the percentage of fruits with double kernels and mean temperatures during the pre‐blossom months. When mean temperatures for single pre‐blossom months were correlated with double‐kernel production, mean temperatures in December showed a much larger correlation (r = ‐0.78) than those of November (r = ‐0.51) or January (r = ‐0.31).

Artificially induced 3–4°C daytime increases in pre‐blossom temperature on the variety ‘Malagueña’ which commonly produces double kernels, caused a marked fall in the percentage of double kerneled fruits, although it did not affect the percentage fruit set. Our results may indicate an important influence of pre‐ blossom temperatures on ovule viability.
Use of the most probable number technique to quantify soil‐borne plant pathogens
Authors: ADAMS M J , WELHAM S J
Published: February 2008

Bioassays using serial soil dilutions and most probable number (MPN) estimations have been used by various authors to quantify inoculum of soil‐borne plant pathogens. The requirements of a reliable bioassay are discussed; they include a good choice of dilution series and reproducible growing conditions. Sources of computer programs for analysis of the data are listed. The importance of testing the fit to the mathematical model used is illustrated and emphasised. Factors affecting the size and stability of the standard errors and of the inherent bias of the most probable number estimate are discussed. Equations are presented for calculating the expected standard errors, approximate confidence limits and least significant differences for different dilution factors and numbers of replicates. The benefits of using uneven replication are illustrated. Mathematical considerations show that the technique should enable differences of an order of magnitude to be detected and MPNs should be quoted with a maximum of two significant figures. Dilution ratios as large as 10 should be avoided. Statistical and biological difficulties, especially in standardising growing conditions when soil moisture is critical, indicate that results should normally be regarded as relative, rather than absolute, measurements of inoculum.
Harvest index: a review of its use in plant breeding and crop physiology
Authors: HAY R K M
Published: February 2008

This review charts the use of the concept of harvest index in crop improvement and physiology, concentrating on the literature from the last 20 years. Evidence from abstract journals indicates that the term has been applied most to small grain cereal crops and pulses, in India, Western Europe and the USA, and that it has been less useful for maize and tuber crops. Standard methods of measuring harvest index, the associated problems of measurement and interpretation, and representative values for a range of world species are reviewed. The values for modern varieties of most intensively‐cultivated grain crops fall within the range 0.4 to 0.6. Variation between varieties of the same species is illustrated by trends in the harvest indices of old, outclassed and recent varieties of temperate and mediterranean wheat and barley (compared under uniform conditions); this shows a progressive increase throughout the present century, although improvement has been much slower in Australia and Canada than in the UK. In most cases, the improvement in harvest index has been a consequence of increased grain population density coupled with stable individual grain weight. The high heritability of harvest index is explored by examining its (rather weak) response to variation in environmental factors (fertilisation, population density, application of growth regulators) in the absence of severe stress. A fuller perspective is gained by reviewing aspects of the harvest index of rice, maize and tropical pulses. With rice, attention must be paid to the fact that the adhering lemma and palea (not primarily part of economic yield) can make up 20% of grain weight; and there are important interactions among biomass, grain yield and season length. Maize differs from most small grain crops in that harvest index (in N. American varieties) was already high at the start of this century, and increases in yield potential have been largely the consequence of increased biomass production. The harvest index of many pulse species and varieties tends to be low because selection has been for some yield in all seasons. Extension of the harvest index concept to express the partitioning of mineral nutrients as well as dry matter (e.g. the nitrogen harvest index) has provided a range of responses whose implications for production and breeding remain to be explored. It is concluded that even though the principal cereal crops appear to be approaching the upper limit of harvest index, and future yield gains will have to be sought by increased biomass production, there will still be a need for the concept of harvest index as a tool in interpreting crop response to different environments and climatic change.