bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aetiology of tobacco leaf curl in southern Africa
Authors: PAXIMADIS M. , REY M E C 
Published: February 2008

SummarySymptom variability of tobacco leaf curl disease has been reported by numerous researchers worldwide. It has been suggested that the different types of leaf curl may be caused by more than one geminivirus strain (McClean, 1940; Osaki & Inouye, 1981), although no evidence exists to support this hypothesis. Previously, several tobacco plants exhibiting a range of leaf curl symptoms were collected from South Africa and Zimbabwe and grouped according to symptomology (Paximadis, Dusterwald, Duyver & Rey, 1997). Three classes (I, II & III) of leaf curl were distinguished, and class I leaf curl from South Africa was shown not to be associated with a geminivirus infection, but was consistently associated with 12 double‐stranded RNA species, now believed to be of phytoreovirus origin. In this study, symptom descriptions of class II and III leaf curl have been reported, and, triple‐antibody sandwich ELISAs, dot‐blot hybridisation analysis, PCR, double‐stranded RNA analysis and seed‐transmission experiments were employed to screen class II and III tobacco plants for geminiviruses or other possible causal agents. Class II leaf curl symptoms were shown not to be associated with a geminivirus infection or with any double‐stranded RNA species. Class II leaf curl symptoms were however transmitted through seed. Class III leaf curl plants tested negative for double‐stranded RNA, but tested positive in PCR, dot‐blot hybridisation and ELISAs for geminiviruses. It is suggested that ‘tobacco leaf curl’ is not a single disease but rather a wide collection of symptoms incited by different agents, and should therefore be described as a disease complex or syndrome.
Influences of compost and casing layer depths on the mechanical properties of mushrooms
Authors: NOBLE R. , RAMA T. , MILES S. , BURTON K S. , STEPHENS T M. , REED J N. 
Published: February 2008

SummaryThe mushroom growing bed consists of an underlying compost which is covered with casing (a peat and chalk or lime mixture) to induce fruit‐body formation. The influences of the depths of the compost and casing layers on the mushroom texture, susceptibility to bruising, and ease of detachment from the growing bed surface were investigated. Textural properties were determined on cubes of cap tissue and detachment torque was determined by using an instrumented rotating suction cup which was lowered on to the caps. The proportion of mushrooms which detached at the base from the bed surface was recorded, since this is an important parameter for an automatic (robotic) harvesting system. Shallow casing resulted in mushrooms that were firmer and less likely to deform plastically, but that showed greater discolouration after a standard bruising treatment. Shallower casing also increased the proportion of mushrooms that detached at the base. Increasing the depth of compost produced firmer mushrooms, significantly increased the detachment torque and reduced the proportion of mushrooms detached at the base. The proportion of mushrooms that detached at the base correlated negatively with the plastic deformation of cap tissue. A positive correlation was found between mushroom dry matter content and tissue firmness.
The morphology of bracken (Pteridium aquilinum (L.) Kuhn) in the North York Moors—a comparison of the mature stand and the interface with heather (Calluna vulgaris (L.) Hull) 2. The rhizome
Authors: WHITEHEAD S J. , DIGBY J. 
Published: February 2008

SummaryThe rhizome system of mature bracken (Pteridium aquilinum (L.) Kuhn) contains large reserves of both biomass (mean 8.63 kg m˜2 fr. wt) and buds (mean 565 m‐2) which are largely responsible for both its persistence and its often rapid rates of vegetative encroachment. Within areas such as the North York Moors the spread of bracken into areas previously dominated by heather and grass is considered undesirable because of reduced land value in terms of both agriculture and ecological diversity.In this paper we describe the morphology of bracken rhizome within a mature bracken stand, and at advancing and stationary stand margins where bracken‐heather interfaces occur. Stationary margins, i.e. those where bracken is not encroaching into heather at a significant rate, often have morphological characteristics intermediate to those of a mature stand and an advancing margin. In the mature stand rhizome biomass is dominated by carbohydrate‐storing long shoots which comprise 63% of the total fresh weight, whilst the majority of rhizome buds (89% of all active and 86% of all dormant buds) are found on frond‐bearing short shoots. At the margins of a bracken stand the proportion of rhizome which is composed of long shoots is even greater, and that of short shoots small relative to that in the mature stand. More transitional shoots are also found at the stand margins. Hence close to the margin a greater proportion of fronds is found on transitional rhizome than is the case in more mature parts of the stand.The majority of buds on all types of rhizome are in a dormant state. The proportion of buds which are active is, however, greater on long and transitional shoots than on short shoots. Hence, a larger proportion of buds are active close to the margin where the rhizome is composed less of short shoots than is the case further into a mature stand.The differences in the morphology of bracken in a mature stand and at the stand margins which are identified here support the idea of controlling bracken at stand margins in preference to the spraying of large areas of dense, mature bracken. Morphological differences include an increased proportion of active buds, greater frequency of fronds per unit rhizome biomass, reduced biomass reserves. Improved conditions for the re‐invasion and re‐establishment of alternative vegetation are also available at stand margins in comparison with the centre of a dense bracken stand.
Callus tissue of Solanum tuberosum L. cultured in the presence of the pyrethroid deltamethrin
Authors: FIDALGO F. , SANTOS I. , SALEMA R. 
Published: February 2008

SummaryThe effect of Decis (deltamethrin as active ingredient) on callus tissue of Solanum tuberosum L. cv. Désirée was studied. Decis is an agrochemical currently used on field grown potato plants to control the Colorado beetle, a potato pest. Deltamethrin added to the culture medium interferes with the behaviour of callus tissue. After 5 h of culture, the level of total proteins was higher in treated tissue than in the control, and SDS‐PAGE showed that deltamethrin promoted the increase of some soluble proteins. After 24 h and 14 days of culture, the level of total proteins became similar in both treated and control material. This similarity between control and treated tissues, after 14 days of culture, occurred as a result of the treatment with deltamethrin which caused a decrease of soluble proteins, but an increase in insoluble proteins whereas the opposite was observed for control callus. SDS‐PAGE of both soluble and insoluble proteins showed that only quantitative dissimilarities occurred. This longer treatment also increased the chlorophyll content. Ultrastructural study of the cells revealed that tissue callus cultured for 14 days in the presence of deltamethrin had plastids containing a more developed membranous system, with a higher number of grana and with more compartments than in control cells. Deltamethrin also promoted the abundance of vesicles associated with dictyosomes.This response of the callus tissue to Decis added to the callus medium parallels the behaviour of potato plants treated with this agrochemical under field conditions (Fidalgo, Santos & Salema, 1993).
Variation and inheritance of resistance to cypress aphid, Cinara cupressi Buckton in Cupressus lusitanica Miller
Authors: KAMUNYA S M , DAY R K , CHAGALA E. , OLNG'OTIE P S 
Published: February 2008

Summary.Cupressus lusitanicaseedlings from open‐pollinated seeds of 18 families were inoculated with day‐old first instarCinara cupressi.Aphid survival was used to determine the genetic basis and inheritance of resistance to the insect. There was marked variation in aphid survival both between and within families. An individual‐tree narrow‐sense heritability of 0.76 ± 0.30 shows strong additive genetic control which could allow effective selection and breeding for resistance. Resistant parents produced resistant progeny while susceptible parents produced susceptible progeny. There were notable exceptions as some susceptible parents produced highly resistant progeny, indicating that they had acquired pollen from resistant neighbours. Recovery of aphid damaged trees is evident implying that care should be taken in selecting for resistance. The strong additive variance and potentially high heritability indicate that one cycle of selection may yield a resistant population, while intraspecific crossing may give better results. Implications of the results in aC. lusitanicabreeding programme are discussed.
Diversity among the coat proteins of luteoviruses associated with chickpea stunt disease in India†
Authors: NAIDU R A , MAYO M A , REDDY S V , JOLLY C A , TORRANCE L. 
Published: February 2008

Summary.Chickpea stunt is an important virus disease of chickpea in the Indian subcontinent which is thought to be caused by infection with a luteovirus. Samples of diseased chickpea plants were collected from different chickpea growing regions of India and analysed with a panel of monoclonal antibodies to potato leafroll, beet western yellows and barley yellow dwarf (RPV strain) luteoviruses. The results suggested that more than one luteovirus was present in chickpea crops near ICRISAT Asia Center, Hyderabad. Aphid transmission tests resulted in the separation of two distinct isolates from these samples. One of them (isolate L) was more efficiently transmitted by Myzus persicae than the other (isolate IC). Nucleotide sequence analysis of DNA obtained by reverse transcription‐polymerase chain reaction (RT/PCR) amplification revealed that the amino acid sequence of the coat protein of isolate L was 94% identical to that of beet western yellows virus, whereas the coat protein sequence of isolate IC was 82% identical to that of isolate L and 80% identical or less to those of the coat protein of other luteoviruses. Using newly designed “universal luteovirus primers”, a minor sequence variant of isolate IC, which was 96% identical to it in part of the coat protein gene, was detected in the same location during the next season. Only isolate IC could be detected in samples from other locations by either serological or nucleotide sequence analysis.
Studies on inheritance of resistance and allelic relationships for strain 2 of pigeonpea sterility mosaic pathogen
Authors: SRINIVAS T. , REDDY M V , JAIN K C , REDDY M S S 
Published: February 2008

Summary.Inheritance of resistance and allelic relationships were studied in three resistant pigeonpea sources for strain 2 of sterility mosaic pathogen. The resistant genotypes (ICP 7035, ICP 7349 and ICP 8850) were crossed with susceptible genotypes (BDN1 and LRG30) to determine the inheritance of resistance. The resistant and susceptible genotypes were also crossed among themselves to obtain information on their allelic relationships. Parents, F1 and F2 generations were sown in pots and screened using infector‐hedge technique. Observations in parents, F1 and F2 generations, indicated dominance of resistance in certain crosses and the dominance of susceptibility in others. Disease reaction appeared to be governed by two independent non‐allelic genes, with at least three multiple alleles, at one of the loci.
Phenological stages of the pomegranate tree (Punka granatum L.)
Authors: MELGAREJO P. , MARTÍNEZ‐VALERO R. , GUILLAMÓN J M , AMORÓS M MIRÓ and A 
Published: February 2008

Summary.As in other temperate species, the pomegranate tree shows different phenological characteristics through its vegetative cycle in response to changing temperature. This phenology has been studied as a basis for comparisons of the successive stages of growth and reproduction in different geographical areas and conditions. The variety Mollar de Elche was studied, since it is grown on more than 95% of the total area devoted to this crop in Spain. Thirteen phenological‐stages were identified during the annual cycle, starting at bud in dormancy and finishing a year later with leaf fall. These stages are denoted using the BBCH General Scale which uses numerical codes to represent particular stages. The code uses a two‐digit number to describe the different phenological states and makes it possible to distinguish between principal and secondary stages of development. The duration of stages was measured in days and as accumulated degree‐day.
Distribution, prevalence and intensity of earthworm populations in arable land and grassland in Scotland
Authors: BOAG B. , PALMER L F , NEILSON R. , LEGG R. , CHAMBERS S J 
Published: February 2008

Summary.The earthworms of arable and pasture fields from 100 randomly chosen arable farms were identified and counted and their relationship with soil factors examined. Thirteen species of earthworm were recorded includingLumbricus friendifrom Scotland for the first time. The most prevalent and numerous species wereAporrectodea longa, Aporrectodea caliginosaandLumbricus terrestris.All earthworm species had cosmopolitan distributions apart fromAporrectodea nocturnaandLumbricus festivuswhich were confined to southern/central Scotland. Four soil characteristics (% moisture, % sand, % organic matter and pH) shared no relationship with species recorded but tillage may have had a detrimental effect on species composition and size of population. It is suggested that the magnitudes of the earthworm populations found, particularly in permanent pasture, were important in maintaining soil structure and fertility, and the spread of the New Zealand flatworm(Artioposthia triangulata), an obligate predator of earthworms, could have a considerable impact on agricultural productivity and wildlife in Scotland.
Transfer of resistance to clubroot (Plasmodiophora brassicae) to swedes {Brassica napus L. var. napobrassica Peterm) from B. rapa
Authors: BRADSHAW J E , GEMMELL DOROTHY J , WILSON R N 
Published: February 2008

SummaryIn 1975, tests with UK populations of Plasmodiophora brassicae not only revealed a lack of effective clubroot resistance in swedes (Brassica napus), but also the outstanding resistance of the European Clubroot Differential (ECD)04 (B. rapa). It was, therefore, decided to transfer the resistance genes from ECD04 to swedes, using the most pathogenic UK population of clubroot (C56) available for screening purposes. An autotetraploid form of ECD04 was crossed with tetraploid kale (B. oleracea) using the latter as female parent. One of the euploid, 2n = 38, hybrids secured by embryo rescue in 1976 was crossed to the swede cultivars Marian and Ruta Øtofte. Three further backcrosses of clubroot resistant plants to lines derived from modern swede cultivars were made over the period 1980 to 1982. Selfing commenced in 1983 to produce F2 populations. From F3 to F5 there was family selection for yield and agronomic characters, as well as single plant selection for clubroot resistance. In 1991, the six most promising F5 families were multiplied for subsequent evaluation in replicated yield trials in Dundee. The most promising family entered official trials at the beginning of 1993 and, 2 years later, was added to the National List as cv. Invitation and granted Plant Breeders' Rights. The first certified seed was sold in 1996, 20 years after the original synthetic B. napus was produced.The breeding programme provided evidence for only one of the three postulated dominant genes in ECD04 being required for resistance to C56 and also good evidence of differential resistance from tests with other clubroot populations. Hence, whilst the differential resistance in cv. Invitation should prove useful in the UK in the immediate future, it may not be durable in the longer term. It is, therefore, argued that the next and more difficult goal to achieve should be to introduce high levels of non‐differential resistance from B. oleracea.
A bioassay for screening materials influencing feeding in the field slug Deroceras reticulatum (Müller) (Mollusca: Pulmonata)
Authors: CLARK S J , DODDS C J , HENDERSON I F , MARTIN A P 
Published: February 2008

SummaryTest materials were incorporated in wheatflour pellets to measure their effect on slug feeding. The dry weights of individual pellets were measured before and after exposure for 24 h to starved slugs. The method gave consistent results, and can accommodate test materials with different physical properties. The phagostimulant effect of sucrose was confirmed. An extract of the herb tarragon (Artemisia dracunculus) was the most effective antifeedant of the materials used at the concentrations tested. The method is compared with other published techniques.
Components of quantitative resistance in sunflower to Alternaria helianthi
Authors: KONG G A , SIMPSON G B , KOCHMAN J K , BROWN J F 
Published: February 2008

SummaryComponents of quantitative resistance, spore production, incubation period, infection frequency and mean lesion size were measured in 17 sunflower accessions inoculated with conidia of Alternuria helianthi under controlled conditions. The same accessions were also rated for disease reaction in the field in 1994 and 1995 using a generated epidemic and varied in their disease reactions from highly susceptible to highly resistant. Spearman's ranking of accessions was highly correlated (r = 0.9) for both years; however, the ranking of components measured under controlled conditions with field severity was generally poor. Regression analysis of components with field severity ratings of the accessions showed that mean lesion size was highly correlated (r = O.74) and infection frequency was moderately correlated (r = 0.58) with the field severity ratings taken over the two years. Infection frequency was also well correlated (r = 0.75) with mean lesion size. Spore production and incubation period were poorly correlated with the field severity ratings for both years. An index based on infection frequency and mean lesion size gave a better correlation with the 1995 field severity ratings than either component alone, but in 1994 the index was not as well correlated with field severity as mean lesion size alone. It is suggested that mean lesion size, determined from plants 7–9 days after inoculation could be used to select for resistance to A. helianthi in the greenhouse. Infection frequency could also be used as a predictor of resistance, but to a lesser degree.
Changes in photosynthetic and transpiration rates of cotton leaves infested with the cotton aphid, Aphis gossypii: Unrestricted infestation
Authors: SHANNAG HAIL KAMEL , THORVILSON HARLAN , EL‐SHATNAWI MOH'D KHAIR 
Published: February 2008

SummaryThe influence of aphid, Aphis gossypii, feeding on photosynthesis and transpiration in cotton plants was investigated under greenhouse conditions. Four population densities of 0, 5, 10, and 25 aphids were used to infest individual cotton leaves. Gas exchange rates were determined for single attached cotton leaves after 9, 18, and 27 days of aphid infestation. Aphid feeding changed photosynthetic rates and transpiration rates. These changes were proportional to the number of aphids and the length of infestation period. Photosynthetic rates were significantly reduced in infested leaves with 25 aphids over 18 days, whereas significant reduction in photosynthetic rates was recorded within 27 days in infested leaves with 5, 10, and 25 aphids in comparison to their respective control. Initial population of 10 aphids increased significantly the transpiration rate of infested leaves over 9 and 27 days. Leaves of plants with 25 aphids had significantly greater transpiration rate than the control at all times.
Effects of method of straw disposal and depth of cultivation on populations of Fusarium spp. in soil and on brown foot rot in continuous winter wheat
Authors: BATEMAN G L , MURRAY G. , GUTTERIDGE R J , COŞLKUN H. 
Published: February 2008

SummarySoil samples (0–10 cm depth) taken from plots of continuous winter wheat at intervals between January 1993 and July 1996 were dilution‐plated on PCNB agar to identify and enumerate colony‐forming units (cfus) of Fusarium spp. Cfus of the main wheat pathogen, F. culmorum, were more numerous in soil from plots that were shallow‐cultivated to 10 cm after each harvest than in those that were ploughed. They were also usually more numerous in plots in which straw had been chopped and incorporated (by shallow cultivation or ploughing) than in those in which straw had been burnt. Increasing amounts of straw tended to increase the number of cfus. Deeper sampling (15–25 cm) showed that ploughing resulted in a more even, but diluted, distribution of cfus down the soil profile. Populations of some commonly found species that are not pathogenic on wheat {F. oxysporum, F. equiseti, F. flocciferum and F. merismoides) were sometimes also affected by straw disposal or cultivation treatments. Alternative methods of estimating population densities (baiting soil with wheat kernels or wheat seedlings, or plating‐out straw fragments) showed generally similar effects of treatments on populations of F. culmorum; the relative merits of the methods are considered. Large differences in population densities of all species occurred within and between seasons. The smallest populations were found in January 1995 but, in the case of F. culmorum, they increased to relatively large numbers in July 1995. The summer of 1995 was warm and dry and especially favourable for development of fusarium foot rot. Severe disease occurred only in this year and was less frequent after ploughing than after tine‐cultivation but more frequent after straw burning than after straw incorporation. The implications of these observations for understanding the role of propagules of F. culmorum in soil as inoculum for foot rot are discussed.
Effects of ascochyta blight (Mycosphaerella pinodes Berk. & Blox.) on biomass production, seed number and seed weight of dried‐pea (Pisum sativum L.) as affected by plant growth stage and disease intensity
Authors: GARRY G. , JEUFFROY M H , TIVOLI B. 
Published: February 2008

SummaryThe effects of ascochyta blight due to Mycosphaerella pinodes on biomass production, seed number and seed weight according to physiological stage and disease intensity were examined. Pea plants were grown in a glasshouse and inoculated with various concentrations of conidia before flowering, at flowering of the second fructifer node (FLO2), at the start of seed filling of the first fructifer node (FSSA1) or the second fructifer node (FSSA2). Uninoculated plants were used as controls. Whatever the stage of inoculation (FLO2 or FSSA2), the disease reduced plant growth and the decrease depended on disease intensity on foliar organs. The seed number was reduced for plants inoculated before flowering, at FLO2 and at FSSA1 and the reduction was linked to disease intensity on foliar organs. At each node, seed number was reduced if the disease occurred before FSSA of the node. The mean seed weight per plant was decreased in plants inoculated at FSSA1 and FSSA2 and the higher the disease intensity on aerials organs, the greater was the reduction of the seed weight. For individual nodes, only inoculations after the beginning of seed filling had a negative effect on mean seed weight at harvest. We found that the decrease of seed number induced by the disease was proportional to aerial biomass production before the end of the period of seed production.