Seed bank and other demographic parameters of broomrape (Orobanche crenata Forsk.) populations in faba bean (Vicia faba L.)

A study on the population dynamics of broom-rape (Orobanche crenata Forskal) in faba bean (Viciafaba L.) was conducted in two locations for 8 years. The O. crenata seed bank increased every year in the 20-cm depth arable layer until it reached approximately 4 million (M) seeds m^?2. Seed viability ranged between 53% and 68%, approximately half of the seeds remaining dormant. About 3 × 10^?3% of the seed bank became attached to the root system of the faba beans. Only 9% of the attached broomrapes developed and emerged from the soil, possibly reflecting high levels of intraspecific competition. Maximum broomrape seed production for a population of 53 emerged broomrapes per m² was approximately 4 M seeds m^?2. About 43% of the seeds produced were not incorporated into the soil, most probably as a result of their degradation, decomposition or dispersion. Stock semencier et autres paramètres démographiques de I'orobanche crénelée (Orobanche crenata Forsk.) dans des cultures de féverolle (Vicia faba L.) Une étude de la dynamique de populations d'orobanche crénelée (Orobanche crenata Forsk.) dans des cultures de féverolle (Viciafaba L.) a été menée pendant 8 années sur deux sites. Le stock semencier de O. crenata a augmenteéchaque année dans la couche (20 cm) arable du sol jusqu'à atteindre 4 millions (M) de graines m^?2. La viabilité des graines était comprise entre 53 et 68%, approximativement la moitié d'entre elles présentaient une dormance. Environ 3 × 10^?3% du stock semencier adhérait au système racinaire de la féverolle. Seulement 9% des orobanches adhérantes se développaient et levaient, ce qui pourrait refléter une compétition intraspécifique importante. La production maxi-male de graines par une population de 53 orobanches levées au m²était d'environ 4 M graines m^?2. Environ 43% des graines produites n'étaient pas incorporées au sol, très prob-ablement en raison de leur dégradation, de leur décomposition ou de leur dispersion. Bodensamenbank und andere populationsde-mographische Parameter der Sommerwurz Orobanche crenata Forsk. in Bestanden der Acker-Bohne (Vicia faba L.) Bei einer Untersuchung der Populationsdy-namik der Sommerwurz Orobanche crenata Forsk. in Beständen der Acker-Bohne (Vicia faba L.) an 2 Orten über 8 Jahre hin nahm die Bodensamenbank in der Pflugzone von 20 cm Tiefe jedes Jahr zu, bis sie rund 4 Millionen Samen m^?2 erreichte. Die Lebensfähigkeit der Samen lag bei 53 bis 68%, etwa die Hälfte war dormant. Ungefähr 3 × 10^?3% kamen mit den Bohnenwurzeln in Berührung. Nur 9% davon entwickelten sich und wuchsen heran, worin vielleicht der hohe Grad intraspezifischer Konkurrenz zum Ausdruck kommt. Die höchste Zahl gebildeter Samen eines Sommer-wurzbestands von 53 Pflanzen m^?2 war rund 4 Millionen. Etwa 43% der gebildeten Samen gelangten nicht in den Boden, wahrscheinlich weil sie zerstört oder verweht wurden.     

Fusarium moniliforme secretes four endopolygalacturonases derived from a single gene product

Extracellular endopolygalacturonase, purified from the pathogenic fungus Fusarium moniliforme, consists of four molecular forms (38, 41·5, 45, and 48·5 kDa, respectively. Three forms (38, 41·5, and 45 kDa) were purified to homogencity by FPLC on a Mono S column followed by electroelution after SDS-PAGE. The N-terminal amino acid sequences of each of the three forms, and of a mixture containing all four forms were shown to be identical to that predicted from the nucleotide sequence of the endopolygalacturonase gene previously cloned from F. moniliforme. Enzymatic deglycosylation experiments revealed the presence of N-linked, high mannose oligosaccharide side-chains on all four forms of endo polygalacturonase. Hydrogen fluoride catalysed chemical deglycosylation of the polygalacturonase mixture yielded a single polypeptide with an apparent molecular mass of 36·2 kDa. Southern blot analysis, carried out at high stringency with an endopolygalacturonase-specific probe on genomic DNA digested with three different restriction enzymes, showed a single hybridizing restriction fragment in all three digests. A single 2·0 Mb chromosome hybridized with the endo polygalacturonase-specific probe, as shown by Southern blot analysis of F. moniliforme chromosomes separated by CHEF electrophoresis. Northern blot analysis revealed only one mRNA species 1350 nt encoding endo polygalacturonase. These data indicate that a single gene encodes the endopolygalacturonases of F. moniliforme.     

Natural enemies and seasonal abundance of the blackmargined aphid (Monellia caryella) in pecan orchards in Israel

The blackmargined aphid,Monellia caryella (Fitch), exhibited a seasonal pattern with early and late peaks of the population in pecan orchards at Newe Ya’ar in the Yizre’el Valley. A similar pattern was not observed at Kibbutz Sede Eliyyahu in the Bet She’an Valley, where there was a single peak, late in the season. The occurrence of natural enemies indicated that spiders and lacewing eggs were the predators most commonly associated with population fluctuations of the aphid. In most cases the rate of increase of the blackmargined aphid was highest late in the season.     

Bacterial biodegradation of ethoxylated surfactants

Agricultural, industrial and domestic use of surfactants leads to the entry of these compounds into terrestrial and aquatic ecosystems. Synthetic surfactants vary significantly in structure, but most consist of alkyl or alkylphenol groups attached to nonionic or anionic hydrophilic moieties. Continued use of these compounds is usually justified on the basis that they do not cause pollution problems because they undergo biodegradation by micro-organisms present in soils and surface waters. In accomplishing biodegradation, micro-organisms, predominantly bacteria, are exploiting these potentially useful resources of reduced carbon to derive energy and support growth in situations which are otherwise frequently oligotrophic. This paper reviews aspects of surfactant biodegradation, especially in relation to alcohol and alkylphenol ethoxylates used extensively as adjuvants for agrochemicals. In principle, bacteria can employ two strategies to gain access to the aliphatic chains in alcohol ethoxylate surfactants: separation of the hydrophobic chain from the hydrophile (central fission), or direct attack on the -terminal of the alkyl chain of the intact surfactant. Direct exo-cleavage of ethylene glycol units from the polyethylene glycol (PEG) chain also provides a third route to assimilable carbon. In pure cultures of known degraders or in mined environmental samples, all three strategies are exploited, some even within the same organism. Central fission occurs predominantly at the alkyl-ether bond, but may also occur within the PEG chain itself, thus producing various glycol intermediates which accumulate in pure cultures but appear only transiently in mixed environmental samples. Against this background, the relative resistance of some alkylphenol ethoxylates to biodegradation can be assessed in mechanistic terms. The steric bulk of the aryl nucleus effectively eliminates the central fission pathway. Moreover, some alkyl phenol ethoxylates contain branched alkyl chains which restrict ω-β-oxidation. As a result, ethoxylate shortening appears to be the major course of biodegradation observed so far. Not surprisingly, these surfactants are observed to undergo extensive primary biodegradation (removal of surfactant properties) but relatively restricted ultimate degradation to carbon dioxide and normal cell components.     

The Danish Integrated Farm Management System—sector module for plant production1

The Danish Integrated Farm Management System is a PC-based system developed by the Danish agricultural advisory service covering all management and control aspects of a farm. It consists of a joint module linking a number of sector modules (cattle production, plant production, economy, pig production and buildings/machinery). The sector module for plant production provides facilities for detailed planning, decision support and control, including all subjects of a complete cultivation plan for each individual field. The fertilizer plan and the crop protection plan provide detailed specifications within the overall cultivation plan. For decision support there are advanced sub-modules for fertilization, crop protection and grassland management. PC-Plant Protection is an optional and fully integrated sub-module of The Integrated Farm Management System, or a self-contained program product.     

Present status of verticillium wilt of olive in Andalucía (southern Spain)1

Verticillium wilt caused by Verticillium dahliae is a disease highly prevalent in newly established olive orchards in Andalucía, southern Spain. Two syndromes of the disease occur in Andalucia, namely apoplexy and slow decline. Apoplexy is characterized by quick dieback of twigs and branches while slow decline consists of rapid drying out of inflorescences together with leaf chlorosis and necrosis. Systematic disease observations carried out in two experimental orchards planted with susceptible cv. Picual indicated that natural recovery of diseased trees occurred over time. Infection and vascular colonization of olive plants by V. dahliae were studied in susceptible (Picual) and resistant (Oblonga) cultivars inoculated with a mildly virulent or a highly virulent cotton-defoliating isolate of V. dahliae. Disease symptoms developed 24–32 days after inoculation in cv. Picual, but at that time plants of cv. Oblonga remained free from symptoms. However anatomical observations and isolations indicated that systemic infections by the two isolates had occurred to a large extent in both cultivars.     

Field evaluation of the single intradermal cervical tuberculin test and the interferon-gamma assay for detection and eradication of bovine tuberculosis in Spain

A field comparison of the interferon-gamma (IFN-gamma) assay and the single intradermal cervical tuberculin (SICT) test for the diagnosis of bovine tuberculosis was conducted. A total of 1136 cattle belonging to 85 herds placed in 'Castilla y León' (northwestern Spain) were chosen, and 21 of these herds were subjected to the diagnostic assays two or three times at intervals of at least 4 months. All the animals positive to any of the tests were slaughtered and tuberculosis was confirmed by culture isolation method (CIM) and further identification by means of PCR. Only 10.6% of cattle reacted with the bovine PPD in the SICT test, a percentage that increased to 12.8% in the IFN-gamma assay. The sensitivity of the IFN-gamma assay compared to CIM was shown to be higher (84.9%) than that of the SICT test (80.2%), but the combination of both tests offered the highest sensitivity (92.9%). The number of false positive reactors (those animals in which CIM was negative) was considerably higher for the IFN-gamma assay than for the SICT test and, conversely, the number of false negative animals (M. bovis isolation but negative immunological result) was higher for the skin test than for the interferon assay. In the herds tested twice, tuberculosis was eradicated after the second cycle of testing in 50%, and in 75% after the third cycle in herds tested three times. The combination of these two techniques instead of separately seems, therefore, to be useful in eradication programmes against bovine tuberculosis.     

Identification of aesculin-hydrolyzing streptococci, lactococci, aerococci and enterococci from subclinical intramammary infections in dairy cows

Aesculin-hydrolyzing, catalase-negative, gram-positive cocci isolated from subclinical intramammary infections in dairy cows were identified to species level using growth characteristics and biochemical activity. The results indicated that the aesculin-hydrolyzing cocci associated with this type of infection are a very heterogenic group. S. uberis strains, including inulin- or beta-glucuronidase-negative isolates, accounted for only about one-third of the collection, and Enterococcus faecalis strains for one-fifth. Other species of some importance included (in descending order of isolation frequency) Aerococcus viridans, Streptococcus pluranimalium, Lactococcus garvieae, Streptococcus bovis and Streptococcus gallolyticus.     

Progression of Mycoplasma hyosynoviae infection in three pig herds. Development of tonsillar carrier state, arthritis and antibodies in serum and synovial fluid in pigs from birth to slaughter

In this investigation, natural infection with Mycoplasma hyosynoviae was followed in groups of individual pigs in three different herds with regard to occurrence of tonsillar carrier state, clinical arthritis and development of antibodies in serum and in synovial fluid. Antibodies were detected by a polyclonal enzyme-linked immunosorbent assay (ELISA) developed for experimental use. The infection with M. hyosynoviae progressed very differently in the three herds investigated. In one herd, the infection was apparently limited to adult pigs. In a second herd, all pigs became tonsillar carriers of M. hyosynoviae, but no mycoplasma-related arthritis nor any serological response was demonstrated within the growing-finishing period. In the third herd investigated, tonsillar infection was detected in all pigs, clinical cases of M. hyosynoviae arthritis followed and a moderate serological response was observed in some, but not all, pigs. In all three herds, M. hyosynoviae infection was carried in the tonsils of the adult pigs, but it was only occasionally transmitted from sows to piglets. Maternal antibodies were transferred to the piglets and persisted for approximately 8-12 weeks. After weaning, some pigs became infected before 20 weeks of age, while others did not. In the majority of cases, the tonsillar infection was established from 11 weeks of age or older. A latent tonsillar infection was present for a period of several weeks within the group of investigated pigs before cases of generalized infection and arthritis were seen. In some cases, generalization of M. hyosynoviae infection in the blood and in joints was observed in spite of the detection of an active serological response a few weeks earlier. The present work suggests that generalization of the infection and development of arthritis may depend on age, immunity, virulence factors and/or infection pressure; in some herds maybe combined with certain triggering mechanisms such as stress and lowered general resistance.