bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

In 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

Test 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

Components 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

The 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

Soil 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

The 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.
Studies on a Nigerian isolate of banana streak badnavirus: I. Purification and enzyme linked immunosorbent assay
Authors: THOTTAPPILLY G. , DAHAL G. , LOCKHART B E L
Published: February 2008

A Nigerian isolate of banana streak badnavirus (BSV) was purified and a polyclonal antiserum was produced in mice. The antiserum titre was between 1:10 000 and 1:40 000 in enzyme linked immunosorbent assay (ELISA), and showed a good specificity to BSV antigens. Comparative tests were carried out to determine the sensitivity and reliability of BSV antigen detection by double antibody sandwich (DAS)‐ELISA, triple antibody sandwich (TAS)‐ELISA, antigen coated plate (ACP)‐ELISA, and protein‐A coated antibody sandwich (PAS)‐ELISA. TAS‐ELISA using rabbit polyclonal antiserum to trap BSV and mouse polyclonal antiserum to detect the virus particles, was more sensitive than ACP‐ELISA and PAS‐ELISA and detected BSV in plant extracts from both symptomatic and some asymptomatic plants. However, immunosorbent electron microscopy detected more BSV‐infected plants from asymptomatic plant samples than did TAS‐ELISA. Results of this study showed that detection of BSV antigens in sap extracts by TAS‐ELISA was most efficient with symptomatic tissues which occurred most frequently in the ‘cool rainy’ season. This suggests that for more reliable BSV‐indexing of field samples, tissue sampling should be done during the rainy season when most BSV‐infected plants express severe symptoms.
Studies on a Nigerian isolate of banana streak badnavirus: II. Effect of intraplant variation on virus accumulation and reliability of diagnosis by ELISA
Authors: DAHAL G. , PASBERG‐GAUHL C. , GAUHL F. , THOTTAPPILLY G. , HUGHES J d'A
Published: February 2008

Monitoring of banana streak badnavirus (BSV) antigens and symptoms in naturally BSV‐infected plantain and banana (Musa spp.) plants showed a great variation in symptom expression, distribution and relative concentration of BSV between and within plants. Expression and distribution of symptoms was erratic within individual leaves as well as between different leaves of the same plant. The concentration of BSV antigens detected by triple antibody sandwich enzyme linked immunosorbent assay (TAS‐ELISA) varied in different plant parts including leaf lamina, midrib and pseudostem, roots and young ‘cigar’ leaf. The concentration of BSV antigens was high in symptomatic tissues but was low or below the limits of detection in most asymptomatic tissues. During ‘hot dry’ seasons when symptoms were not fully expressed, the concentration of BSV antigens in leaf tissues declined drastically, often below the detection limit of TAS‐ELISA. These results suggested that for more reliable detection of BSV antigens by TAS‐ELISA, it is advisable to index plants using composite tissue samples comprising as many leaves as possible for each plant and collected during cool and/or rainy seasons when symptom expression is generally severe.
The effect of seed dormancy on percentage and rate of germination in Polygonum persicaria, and its relevance for crop‐weed interaction
Authors: VLEESHOUWERS L M
Published: February 2008

Changes in germination percentage and germination rate of Polygonum persicaria resulting from loss of primary dormancy during chilling of imbibed seeds were quantified. Both percentage and rate of germination increased with increasing loss of dormancy. It was concluded that retardation of germination caused by dormancy was not due to dormancy release prior to germination, but to retardation of the germination process itself. When evaluated in relation to competition between sugar‐beet and P. persicaria, the effect of dormancy on the germination percentage was more important than the effect on germination rate, but for an accurate prediction of yield loss, the latter effect cannot be neglected.
The response of dodder {Cuscuta spp.) seedlings to phytohormones under various light regimes
Authors: HAIDAR M A , ORR G L , WESTRA P.
Published: February 2008

Phytohormones were screened for their effects on induction of coiling and prehaustoria in de‐etiolated excised dodder seedlings under different light treatments. Zeatin stimulated coiling and the formation of prehaustoria under all light tested, even in darkness. A synergistic effect was observed with zeatin and far‐red light (700–800 nm) but not with red light (600–700 nm) on the formation of prehaustoria. Application of indole‐3acetic acid inhibited zeatin‐induced coiling and prehaustoria development under blue (400–500 nm) and a mixture of red plus far‐red light, but not in blue plus far‐red light. Ethylene had no effect on coiling and prehaustoria development. Observations suggest that zeatin‐induced coiling and prehaustoria development may be mediated by phytochrome.
Canola seed germination and seedling emergence from pre‐hydrated and re‐dried seeds subjected to salt and water stresses at low temperatures
Authors: ZHENG G H , GAO Y P , WILEN R W , GUSTA L V
Published: February 2008

Low soil temperatures and low water potentials reduce and delay the seed germination of canola (Brassica rapa L., B. napus L.) in western Canada. Germination is also very sensitive to the salinity effects of nitrogen fertiliser placed with the seed, especially when the seed bed is relatively dry. The effects of pre‐hydration and re‐drying treatment on canola (Brassica rapa L. cv. Tobin) seed germination and seedling emergence at 10°C subjected to either a water or salt stress were determined. Low water potentials, induced by polyethylene glycol (PEG 8000), low soil moisture, or high concentrations of salts, reduced both germination and seedling emergence, and increased the time to 50% germination and emergence of seeds at 10°C. At equal osmotic potentials, Na2SO4 was less inhibitory on low temperature germination than either NaCl or PEG, suggesting that the sulphate ion partially alleviated the inhibitory effects of low water potential. Solutions of NaCI produced more abnormal seedlings compared to Na2SO4, suggesting that NaCl was more toxic than Na2SO4 during seedling development. Pre‐hydration and re‐drying partially overcame the inhibitory effects of both low water potential and salts on seed germination and seedling emergence at 10°C. The seed treatment increased the germination rate in Petri dishes and seedling emergence from a sandy loam soil. Water potentials or soil water contents required to inhibit 50% germination or emergence at 10°C were lower for treated seeds compared to control seeds. Salt concentrations inhibiting 50% emergence were higher for treated seeds than control seeds. Neither treated nor control seeds produced seedlings which emerged if the soil water content was lower than 9% or when the soil was continuously irrigated with salt solutions of 100 mmol kg‐1 of NaCl or 50 mmol kg‐1 of Na2SO4. These results suggest that the pre‐hydration and re‐drying treatment did not lower the base water potentials at which seedling emergence could occur. Abnormal seedlings were observed in both treated and control seeds, particularly if the soil was watered with NaCl solutions; however, the seed treatment reduced the number of abnormal seedlings.
Phylogenetic relationships of coconut phytoplasmas and the development of specific oligonucleotide PCR primers
Authors: TYMON A M , JONES P. , HARRISON N A
Published: February 2008

Using the polymerase chain reaction the 16S rRNA genes and the 16S‐23S spacer regions of phytoplasmas associated with lethal decline diseases of coconut palm (Cocos nucifera), were amplified from infected plants from Florida and the Yucatan region in Mexico and from east and west Africa. Following sequencing of the rDNA products, phylogenetic analysis confirmed that these coconut phytoplasmas form a separate cluster within the phytoplasma clade and that the pathogen causing diseases in west Africa formed a new sub‐clade within this cluster. Analysis of the 16S‐23S intergenic spacer regions confirmed the sequence diversity of this region and enabled two primers to be designed which were specific for the diseases found in east and west Africa. None of these specific primers, when paired with a universal primer, produced PCR amplification products from healthy coconut DNA, infected coconut DNA from the Caribbean or DNA from a variety of periwinkle (Catharanthus roseus)‐maintained phytoplasmas. These specific primers can serve as effective tools for identifying particular coconut phytoplasmas in field samples.
Sources of resistance to groundnut rosette disease in global groundnut germplasm*
Authors: SUBRAHMANYAM P. , HILDEBRAND G L , NAIDU R A , REDDY L J , SINGH A K
Published: February 2008

About 6800 groundnut germplasm accessions originating from South America, Africa, and Asia were evaluated for resistance to rosette disease using an infector row technique between the 1990/91 and 1996/97 growing seasons. Of these, 116 germplasm accessions, including 15 short‐duration Spanish types, have shown high levels of resistance to rosette disease. A high percentage of these resistant accessions were from West Africa and a few were from Asia and southern Africa. Only one out of 1400 accessions from South America showed resistance to rosette disease. All disease‐resistant accessions were susceptible to groundnut rosette assistor virus. This is the first report to identify sources of resistance to rosette disease in groundnut germplasm from Asia and South America. These additional sources of resistance provide an opportunity to broaden the genetic base of resistance to rosette disease. The origins of rosette resistance in groundnut are discussed.
The design and analysis of breeders' trials of sugar beet (Beta vulgaris) using two‐dimensional blocking structures
Authors: ZHAO B. , MEAD R. , MACKAY I J , CALIGARI P D S
Published: February 2008

A method for generating two‐dimensional blocking designs to fit any shape and size of experimental area is presented. The method takes an alpha design appropriate to the experimental area and imposes additional blocking perpendicular to the alpha blocks. Improvements to the design are then made by repositioning entries within the alpha blocks. Although this method of construction is less sophisticated than for other two‐dimensional designs, the designs are particularly suited to large scale breeders trials where no alternative two‐dimensional design may exist. The designs have been used for 3 yr in a sugar beet breeding programme, and have given improvements in efficiency over one‐dimensional alpha designs.
Chemical control of Alternaria brown spot on Minneola tangelo in South Africa
Authors: SWART S H , WINGFIELD M J , SWART W J , SCHUTTE G C
Published: February 2008

The effectiveness of several groups of fungicides was compared with that of copper and mancozeb for their ability to control Alternaria brown spot on Minneola tangelo. Variables used for comparing fungicides in order of importance were: performance index, the number of exportable fruits per tree, the number of fruits per tree free of Alternaria lesions and total number of fruits per tree. Percentage exportable fruits was not a reliable variable for comparing treatment efficiency.

During the 1992/1993 evaluations iprodione, difenoconazole, and procymidone showed promising control of the disease. Other than for difenoconazole, members of the triazole group were not effective, especially at dosages below 10 g a.i. 100 litre ] water. Moderate control of Alternaria brown spot was obtained using copper and mancozeb. During the 1993/1994 season spray programmes with copper oxychloride, mancozeb, maneb plus zinc oxide, procymidone, iprodione, and tebuconazole were compared in field trials, for the control of Alternaria brown spot on Minneola tangelo. Mancozeb applied at 2‐weekly intervals was the most effective spray programme, followed in order of efficiency by programmes using procymidone, maneb plus zinc oxide, and mancozeb applied at 4‐ and at 3‐weekly intervals. Iprodione and tebuconazole were not particularly effective in this evaluation, although they performed significantly better than the control treatment. Trees treated with copper oxychloride produced poorly, in spite of a high percentage exportable fruits.
Effects of cold shock on the susceptibility of white lupins to fungal diseases
Authors: ETHERIDGE J V , BATEMAN G L
Published: February 2008

Experiments in controlled environments tested interactions between freezing soil (a compost‐vermiculite mixture) and below‐ground infection of white lupins with each of three pathogenic fungi (Botrytis cinerea, Fusarium avenaceum or Pleiochaeta setosa) on plant disease and death. Whilst soil freezing (up to 4 days at – 1oC) caused slight necrosis and increased the severity of disease symptoms, incidence of plant death was increased only after inoculation, before freezing, of the lower hypocotyl of the youngest plants (soil frozen at less than 17 days old) with P. setosa. It is concluded that the contribution of below‐ground infection by pathogenic fungi to overwinter losses in autumn‐sown white lupin crops is exacerbated to a negligible extent by soil freezing, the main primary cause of such losses.
Serological identification and quantification of potato cyst nematodes from clean cysts and processed soil samples
Authors: CURTIS R H C , DUNN J. , ROBINSON M P , MARTINS F. , EVANS K.
Published: February 2008

Two monoclonal antibodies which specifically recognise each of the two species of potato cyst nematodes (PCN) and do not cross react with other species of soil nematodes, were used successfully in an immunoassay to identify and quantify PCN species using clean cysts and mixed populations. These antibodies show reactivity only towards antigens prepared from live eggs and they recognise antigens which are easily released from the nematodes. The results presented in this paper show that serological identification and quantification of PCN, not only from clean cysts but also from processed soil samples is achievable. A simple procedure to recover nematodes from soil samples and then to release nematode antigens was devised. The use of these procedures and the immunoassay for quantification of PCN was validated in tests with soil samples from Northern Portugal. The flotation method proved to be as efficient as the Fen wick Can for cyst recovery from soil samples. A significant correlation was obtained between results from immunoassay estimates and the traditional method of cyst picking and egg counting. The amount of organic matter (OM) present in the soil samples affected the sensitivity of the immunoassay but quantification of nematodes extracted from soil samples was possible with soils containing up to 14% of OM. The challenge remains to optimise the extraction procedures and the immunoassay, in practical conditions with highly organic soils containing cysts of different sizes and ages.
A chamber for the simulation of radiation freezing of plants
Authors: FULLER M P , GRICE P LE
Published: February 2008

Frost injury to plants can occur following episodic radiation frosts. In the UK this is particularly important to spring sown crops such as potatoes. Most laboratory based frost studies simulate freezing using either conductive or convective freezing chambers. Such frost tests do not simulate overnight freezing events adequately.

A freezing chamber based on radiative cooling is described which mimics overnight radiative freezing. The chamber is rectangular in design (1 m × lm × 2 m high) with a radiative cooling plate at the top of the chamber cooled to ‐40°C to ‐45°C using HFC coolants, which acts as a cold black body. The sides of the chamber are also cooled to variable temperatures down to ‐5°C in order to prevent the chamber walls radiating to the plant material during testing.

Using thermocouples to measure air temperature and plant temperature the chamber has been characterised to simulate the radiative cooling conditions found in the UK during autumn and spring. Exotherm detection upon plant freezing is simplified by virtue of the reduction in temperature fluctuation normally experienced at the plant surface during natural freezing. Radiation frosts and subsequent frost damage to potatoes have been recorded in the temperature range ‐4°C to –5°C. The equipment is recommended for studies of frost damage to plants normally caused by episodic radiation frost events.
The palatability of 78 wildflower strip plants to the slug Arion lusitanicus
Authors: BRINER T. , FRANK T.
Published: February 2008

AsArion lusitanicushas been observed in high densities in wildflower strips, the palatability of the foliage of 78 species of sown and naturally occurring plants found in such strips was investigated. In the laboratory, the slugs were offered a surplus of fresh, mature leaves and, after 16 h, a consumption index was calculated to rank the plants according to their palatability to the slugs.Arion lusitanicusshowed clear preferences for particular plant species, but more than two thirds of all plants investigated were scarcely eaten.Brassica napuswas most eaten, followed byPapaver rhoeas, Capsella bursa‐pastorisandLamium purpureum.

Overall,A. lusitanicuspreferred sown species to naturally occurring ones and preferred annuals to perennials.
Sclerospora graminicola‐ and arachidonic acid‐induced autofluorescence in downy mildew resistant and susceptible genotypes of pearl millet
Authors: GEETHA S. , SHETTY SUDHEER A , SHETTY H SHEKAR , PRAKASH H S
Published: February 2008

Autofluorescence of downy mildew resistant and susceptible cells of pearl millet seedlings undergoing hypersensitive reaction (HR) upon Sclerospora graminicola‐inoculation and arachidonic acid (AA)‐treatment was studied. Two‐day‐old seedlings of a highly resistant (IP 18296) and a highly susceptible (23D2B) genotype of pearl millet were either inoculated with zoospore suspension of S. graminicola or treated with AA for 24 h. The coleoptiles with hypersensitive necrotic spots were processed by the standard procedure, and the tissues were subjected to fluorescence microscopy. A differential accumulation of autofluor‐escent compounds in resistant and susceptible pearl millet genotypes was observed with most accumulation occurring in resistant cells treated with AA. The variation in the degree of fluorescence and the spatial accumulation of autofluorescent compounds among the two inoculated/treated genotypes is discussed.
The case for headland set‐aside: consideration of whole‐farm gross margins and grain production on two farms with contrasting rotations
Authors: SPARKES D L , RAMSDEN S J , JAGGARD K W , SCOTT R K
Published: February 2008

Spreadsheet calculations were used to compare headland set‐aside with rotational set‐aside in terms of gross margin and grain production on two farms with contrasting rotations. At Broom's Barn, Suffolk there was a five course rotation consisting of sugar beet and four cereals, while at Bunny Park, Nottinghamshire oilseed rape was the break crop, followed by three cereals. For both farms a sensitivity analysis was used to investigate the effect of the proportion of the farm required to be set aside, the extent of headland yield reduction and the cereal price on the outcome of the spreadsheet calculations.

In general headland set‐aside out‐performed rotational set‐aside. Yields on headlands were always less than the main body of the field, but it was on the turning headlands where yield was particularly depressed. Thus the advantage, in terms of gross margin, of setting aside the headlands was greatest when the requirement could be fulfilled by fallowing most turning headlands, but no non‐turning headlands.

Generally, rotational set‐aside reduced grain production more than headland set‐aside, but when the spreadsheet models were adjusted to maintain the area of sugar beet, the situation was reversed. In this case headland set‐aside produced a larger gross margin and had the greatest impact on grain production.

An extension of the analysis is to ask the question: even if set aside is not an option, is it worthwhile to crop rather than fallow headlands? For cereals and oilseed rape the answer is in the affirmative; the gross margin for headlands remains positive, even when prices are much reduced, because the arable area payment more than offsets the variable costs. This does not hold for crops such as sugar beet that are not eligible for arable area payments.

An additional benefit from headland set‐aside is its potential to enhance the environment through increased habitat diversity and the provision of ‘buffer zones’ to prevent agrochemicals from drifting into hedges and watercourses.
The potential benefits from cultivar specific red clover ‐potato crop rotations
Authors: STURZ A V , CHRISTIE B R
Published: February 2008

The aim of this study was to determine if endophytic bacteria could contribute to cultivar specific interactions between red clover(Trifolium pratenseL.) and potatoes(Solanum tuberosumL.) in crop rotations. Endophytic bacteria were isolated from the roots of four red clover cultivars (AC Charlie, Altaswede, Marino and Tempus) grown in the field. Populations of bacteria from each cultivar were similar. The most abundant genus wasRhizobium,but species ofCurtobacterium, Pseudomonas,andXanthomonaswere common to all cultivars. Plantlets of two potato cultivars, Russet Burbank and Shepody, were inoculated individually with the seven bacterial isolates most frequently recovered from each red clover cultivar, and grown in Magenta vessels for 6 wk. Significant differences were found for plant height, and wet weights of roots, shoots and their total. Potato cultivars differed for root wet weight only, while red clover cultivar, as a source of bacteria, had a significant effect on all traits except plant height. Differences among bacteria were significant for all traits except shoot wet weight. There was a significant interaction of potato cultivar by red clover cultivar. The potato cultivar Russet Burbank did best with bacteria from the red clover cultivar, Marino; and Shepody, with bacteria from Altaswede.
Galling and reversion disease incidence in a range of blackcurrant genotypes, differing in resistance to the blackcurrant gall mite (Cecidophyopsis ribis) and blackcurrant reversion disease
Authors: JONES A TEIFION , BRENNAN R M , McGAVIN WENDY J , LEMMETTY ANNE
Published: February 2008

An assessment was made of the response of 10 blackcurrant genotypes, differing in resistance to the agent of blackcurrant reversion disease (BRD) and to its gall mite vector, in field trials in Scotland and Finland over 5 yr. At each location, the 10 genotypes were planted in plots containing infector plants with high inoculum levels of the two organisms. In Scotland, the infector plants contained large numbers of gall mites (Cecidophyopsis ribis) and were infected with the European (E) form of BRD; in Finland, infector plants contained a different species of gall mite (C. spicata) and the severe Russian form (R) of BRD. As expected, at both sites, almost all plants of cvs Ben Alder, Ben Lomond, Ben Tirran, Ojebyn and an SCRI selection F4/1/66, which are susceptible to gall mite and BRD, became infested with each of these organisms. However, in Scotland but not in Finland, 58% of cv. Ojebyn plants were affected by BRD. The cv. Foxendown, which contains gene Ce that confers apparent immunity to C. ribis, was free from galls and failed to develop distinctive BRD symptoms at both sites. The cvs Rus and Neosypajuscajaija, which contain gene P which is reported to confer resistance to C. ribis, were infested more slowly by mites than the mite‐susceptible genotypes and showed a smaller number of galls per plant. Also, they were infected with BRD more slowly than some mite‐susceptible genotypes although by the end of the experiment, most plants were affected by BRD. All plants of cvs Golubka and Ben Gairn, which are resistant to the agent of BRD, remained free from distinct BRD symptoms at both sites despite the fact that plants contained galls. These data indicate the superiority of gene Ce over gene P for resistance to gall mites with the added benefit that the virtual immunity to gall mites provided by gene Ce provides a high level of protection against infection with BRD. The relative merits of these different forms of resistance to gall mites and BRD in blackcurrant are discussed in relation to present control methods for these two organisms and in the light of recent findings of different species of eriophyid mites on Ribes species.
Interactions between wheat (Triticum aestivum L.) cultivar, row spacing and density and the effect on weed suppression and crop yield
Authors: CHAMPION G T , FROUD‐WILLIAMS R J , HOLLAND J M
Published: February 2008

In 1995/1996 weed suppression ability of two wheat cultivars (Spark and Tonic) was investigated in conjunction with two row spacings (15 cm and 9 cm) and three sowing densities (125, 250 and 350 plants m‐2). Weed biomass was influenced initially by crop density, and following stem extension by both cultivar and density, although these factors did not interact. Tillering capacity was a poor predictor of weed suppression ability and Spark, the more profusely tillering cultivar, contained greater weed biomass than Tonic. The earlier stem extension of Tonic increased shading at 0–20 cm above ground level compared to Spark and this was believed to be the reason for reduced weed biomass. Row spacing did not influence weed suppression, but grain yield was reduced in 15 cm rows at a density of 350 plants m‐12 compared to 250 plants m‐12. This may be of importance to growers contemplating the use of wider row spacings for mechanical weeding.
Effects of pod infection by Mycosphaerella pinodes on yield components of pea (Pisum sativum)
Authors: BEASSE C. , NEY B. , TIVOLI B.
Published: February 2008

Yield reduction of pea (Pisum sativum) due to various types of infections by Mycosphaerella pinodes on pods was assessed. A range of disease severities was created on pods of pea plants grown in the glasshouse, by painting the pods with different concentrations of spore suspensions, at three different pod development stages: lag phase, the beginning of seed filling (BSF) and mid‐filling of the seeds.

Seed number at harvest was reduced only if the pods were infected before BSF, as shown previously for whole plant infections. Pod infections led to individual seed weight (ISW) losses from zero (for late infections, at mid‐filling) to 20% (for earlier infections and severe disease). Infection during the lag phase affected ISW by reducing seed growth rate, whereas infection at BSF tended to reduce the duration of seed filling. There was a linear relationship between the area under the disease progress curve and the percentage decrease in ISW. This model should be complemented by the effect of leaves and stem infections, in order to predict ISW losses in diseased crop conditions, in which epidemics occur on all aerial parts of the pea plant.
Effect of the anthraquinones emodin and physcion on availability of selected soil inorganic ions
Authors: INDERJIT  , NISHIMURA HIROYUKI
Published: February 2008

The effects of emodin and physcion, two anthraquinones involved in Polygonum sachalinense allelopathy, were studied in soils amended with 5, 10 and 15 mg 100 g‐1 soil of each compound, and with their mixtures. Recovery of each compound and its effects on availability of soil Mn++, Na+, K+, Mg++, Ca++ and PO43‐ were monitored. Total phenolic content of each soil was determined to study the role of degraded phenolics. Soil amended with 5 mg of emodin and physcion gave maximum recovery of the two anthraquinones. Soil amended with different amounts of two anthraquinones and their mixture had significant lower values for pH compared to control. In general, both anthraquinones affect availability of soil inorganic ions. Compared to unamended control soil, a significant decrease in Mn++ availability, and an increase in Na+ and K+ availability when emodin and physcion were added to the soil was observed. A correlation among soil inorganic ions, relative recovery of two compounds, and total phenolic content of amended soils was observed. Results indicate that emodin and physcion influence the availability of soil inorganic ions. The significance of the effect of allelopathic compounds on soil inorganic ions is discussed.
Growth of potato cultivars in response to application of phosphate fertiliser
Authors: JENKINS P. D. , ALI HAKOOMAT
Published: February 2008

Three experiments examined the response of potato cultivars from different maturity groups to fertiliser phosphorus application under conditions of relatively low residual soil P. Initial expansion of the leaf canopy was much more rapid following P application and maximum cover was attained sooner. In the absence of applied P, maximum ground cover was reduced substantially in early‐maturing cultivars but not in maincrop cultivars. At early harvests, all cultivars showed very large growth responses to P application, but cv. Rocket grown from well‐sprouted seed showed a significantly larger response than cv. Desiree. In the absence of applied P, ground cover was in some cases higher at later growth stages allowing a substantial degree of growth compensation so that final harvests showed only small effects of P application on dry matter yields. At final harvests, no significant interactions between cultivar and phosphorus fertiliser level were found for either dry matter production or P uptake despite some apparent effects. Phosphorus application increased dry matter production through increased interception of solar radiation with no effect on efficiency of utilisation.
Effect of cowpea monocultures and polycultures with sorghum and greengram on predatory arthropods
Authors: NAMPALA P. , ADIPALA E. , ‐LATIGO M W OGENGA , KYAMANYWA S. , OBUO J. E.
Published: February 2008

Prior to implementing biological control, knowledge on availability of the possible enemies of pest(s) is important. Therefore, as part of a larger on‐farm study whose main objective was to develop a farmer‐friendly package for the management of cowpea pests, the diversity and abundance of insect predators within cowpea cropping systems (sole crops and intercrops) were monitored at three diverse locations in eastern Uganda. Coccinellids, syrphid larvae, spiders, Orius sp. and earwigs were observed at all locations. Abundance of Coccinellids and syrphid larvae were not influenced by the cowpea genotype nor cropping systems. Contrastingly, the abundance of predatory Orius sp., spiders and earwigs differed significantly among the cowpea cropping systems, being more common in the cowpea pure stands and cowpea + greengram than in the cowpea + sorghum intercrops.
Preliminary studies on Ramularia crupinae sp. nov. as a potential biological control agent for common crupina (Crupina vulgaris) in the USA
Authors: HASAN S. , SOBHIAN R. , KNUTSON L.
Published: February 2008

Common crupina, Crupina vulgaris (Asteraceae), is an alien weed of pastures and disturbed noncrop lands in the western USA. Research is underway in Europe to search for the natural enemies to control the weed. Among various natural enemies attacking C vulgaris, a new fungal species, Ramularia crupinae, has been found to cause serious damage to the weed. The fungus has been grown on various media and a modified V8 juice agar has proved to be suitable for both growth and sporulation. Greenhouse and field studies have shown that R. crupinae can kill infected leaves, thus reducing the plant growth, and in severe cases can kill the young plants. During preliminary host‐range tests using various members of the Asteraceae, including artichoke and safflower, the fungus attacked only C. vulgaris.
Local and systemic changes in glucosinolates in Chinese and European cultivars of oilseed rape (Brassica nap us L.) after inoculation with Sclerotinia sclerotiorum (stem rot)
Authors: LI Y. , KIDDLE G. , BENNETT R N , WALLSGROVE R M
Published: February 2008

Four Chinese Brassica napus lines, generated through a breeding programme to identify Sclerotinia sclerotiorum tolerant and susceptible lines, and three European varieties were analysed for changes in glucosinolates (qualitative and quantitative), and general host reactions, after localised inoculation with a UK S. sclerotiorum isolate. Plants at the fifth leaf stage were either singly inoculated (third leaf) or were inoculated once (third leaf) and then challenged a second time (seventh leaf) 7 days after the first inoculation. The results showed very distinct reactions in the different lines and cultivars to the fungus, both locally and systemically.

Of the European lines B. napus cv. Bienvenu showed good resistance (small lesions and less host damage) both 3 and 7 days post‐inoculation. Capricorn was the most susceptible followed by Cobra; the third leaves of these cultivars were showing strong chlorotic and necrotic reactions by day 3 and lesions were well developed. By day 7 the third leaves of Capricorn were completely rotten whilst Cobra still had a little healthy tissue.

Inoculation of the four Chinese lines showed that two had moderate resistance (014 and 020 — slightly less resistant than Bienvenu) and two were very susceptible (016 and 024 — similar reactions to Capricorn and Cobra), based on lesion size and host tissue damage. Glucosinolate induction in line 014 was good both locally and systemically, with clear local and systemic induction of indolylglucosinolates and 2‐phenylethylglucosinolate both 3 and 7 days post‐inoculation. Line 020 did not show no particular increases in glucosinolates after inoculation either locally or systemically. In line 016 there was a small local increase and a large systemic reduction in total glucosinolates. Inoculation of line 024 caused no major local changes in glucosinolates and again a big reduction in glucosinolates systemically.

The dual inoculation system, with lines 014 and 016, produced comparable results, with line 014 showing good local and systemic induction of glucosinolates (after the first inoculation) and a further local and systemic induction after the second inoculation. This induction in pre‐inoculated line 014 plants was associated with a reduction in lesion size of the second inoculum. Line 016 responded poorly both locally and systemically, and there were no real decrease in the lesion size of the second inoculum. It appears that in line 014 glucosinolate induction may be an important part of resistance, whereas in line 020 there are clearly other non‐glucosinolate factors involved. The poor local and systemic induction of glucosinolates in lines 016 and 024, and subsequent susceptibility, implies that glucosinolate induction may be an important marker of resistance to S. sclerotiorum in oilseed rape.
Virus particles in guttate and xylem of infected cucumber (Cucumis sativus L.)
Authors: FRENCH CHRISTOPHER J , ELDER MAUREEN
Published: February 2008

Particles of plant viruses representing ten genera were visualised by electron microscopy in samples of guttate from systemically infected cucumber (Cucumis sativus L.) plants. For the majority of viruses tested, guttation samples tested positively by ELISA and infectivity was also demonstrated. Virus particles of zucchini yellow mosaic potyvirus were also observed in xylem in sections of infected root tissue. Since guttate originates from xylem exudate, this study demonstrates the potential for xylem tissue to act as a conduit for a diverse group of plant viruses in planta