Infection of ryegrass by three rust fungi (Puccinia coronata, P. graminis and P. loliina) and some effects of temperature on the establishment of the disease and sporulation

Experiments were conducted to examine the processes leading up to the infection of Lolium temulentum by crown rust ( Puccinia coronata ), stem rust ( P. graminis ) and brown rust ( P. loliina ), and the effects of temperature on these processes and sporulation. Uredia of all three rusts were produced freely if the adaxial leaf surface was inoculated, but did not form following inoculation of the abaxial surface. Light and scanning electron microscopy revealed abnormal growth of germlings on the abaxial surface which had amorphous sheet-like epicuticular waxes and very few stomata. On the adaxial leaf surface germ tubes of all the rusts orientated at right angles to the long axis of the leaf. However, the directional growth of germ tubes was often disrupted when they contacted the surface of bulliform cells at the base of leaf grooves. For P. loliina the optimum temperatures for urediospore germination and sub-stomatal vesicle formation were 12–16°C, and 8–20°C for appressorium formation. The optimum temperatures, for the same stages of fungal development, for P. coronata and P. graminis were higher. Urediospore production of P. loliina was higher at 10°C than at 25°C, but was similar at both temperatures for P. coronata .     

Decrease by plant development and leaf age of susceptibility of groundnut to rust (Puccinia arachidis) in a susceptible cultivar

The effects of plant development and leaf age on the infection efficiency (IE), the latency period (LP) and the sporulation intensity (SP) of groundnut rust were studied using detached and attached leaflets of a highly susceptible groundnut cultivar. The results indicate a decrease ofIE with increasing leaf age and an increase ofLP with increasing leaf age and development stage. A significant effect of detachment onIE was found. However, experiments on both detached and non-detached leaflets resulted in the same, general conclusions. The observed reduction ofIE and lengthening ofLP suggest that further studies would profitably distinguish epidemiologically different layers in the host canopy.Samenvatting De invloed van het ontwikkelingsstadium van de plant en van de leeftijd van het blad op de infectie-efficiëntie (IE), de latentieperiode (LP) en de sporulatie-intensiteit (SP) van aardnootroest werd onderzocht bij een zeer vatbare aardnoot-cultivar aan wel en niet afgesneden deelblaadjes. De resultaten laten een afname zien vanIE bij toenemende bladleeftijd alsmede een toename vanLP met de toename van bladleeftijd en ontwikkelingsstadium. Het effect van het afsnijden van de deelblaadjes opIE was significant, maar proeven met wel en met niet afgesneden blaadjes leidden tot dezelfde algemene gevolgtrekkingen. De waargenomen afname vanIE en verlenging vanLP doen vermoeden dat voortgezet onderzoek een nuttig onderscheid zal kunnen maken tussen in epidemiologische zin verschillende bladlagen van het gewas.     

Identification of resistance to Pratylenchus thornei,P. neglectus,P. penetrans and Ditylenchus dipsaci in Turkish accessions of five wild chickpea species (Cicer bijugum,C. echinospermum,C. pinnatifidum,C. reticulatum and C. turcicum)

Phytoparasitica - Plant-parasitic nematodes feed and reproduce in chickpea roots. Root-lesion nematodes are one of the most important biotic factors to limit chickpea production in the world. The...     

Evaluation of a rapid diagnostic field test kit for identification of Phytophthora species, including P. ramorum and P. kernoviae at the point of inspection

Plant health regulations to prevent the introduction and spread of Phytophthora ramorum and P. kernoviae require rapid, cost effective diagnostic methods for screening large numbers of plant samples at the time of inspection. Current on-site techniques require expensive equipment, considerable expertise and are not suited for plant health inspectors. Therefore, an extensive evaluation of a commercially available lateral flow device (LFD) for Phytophthora species was performed involving four separate trials and 634 samples. The assay proved simple to use, provided results in a few minutes and on every occasion a control line reacted positively confirming the validity of the test. LFD results were compared with those from testing a parallel sample, using laboratory methods (isolation and real-time PCR). The diagnostic sensitivity of the LFD (87·6%) compared favourably with the standard laboratory methods although the diagnostic specificity was not as stringent (82·9%). There were a small number ( n  = 28) of false negatives, but for statutory purposes where all positive samples must be identified to species level by laboratory testing, overall efficiency was 95·6% as compared with visual assessment of symptoms of between 20-30% for P. ramorum and P. kernoviae . This work demonstrates the value of the LFD for diagnosing Phytophthora species at the time of inspection and as a useful primary screen for selecting samples for laboratory testing to determine the species identification.     

Description of a new species of seed-gall nematode, <Emphasis Type="Italic">Anguina obesa</Emphasis> n. sp. (Nematoda: Anguinidae) from northern Iran,and its phylogenetic relations with other species and genera

Anguina obesa n. sp., a new species of the genus, causing small seed galls inside the ovaries of foxtail weed plants (Alopecurus mysuroides Huds.) is described and illustrated based on its morphological and molecular characters. The new species is characterized by its 1516–2564 μm long obese females irregularly ventrally curved after fixation, having six lines in lateral fields, 6–9 μm long stylet with well-developed rounded knobs, constriction at junction of isthmus with the pharyngeal bulb, monodelphic-prodelphic female reproductive system, and conical, 60–80 μm long tail. Males of the new species are characterized with their slender 936–1420 μm long body, 25–30 μm long tylenchoid spicules, and bursa not reaching tail tip. Second stage juveniles of the new species were also common inside the galls and also recovered from soil in type locality. The new species is morphologically close to Anguina agropyronifloris, A. amsinckiae, A. paludicola and A. tumefaciens, but is more closely related to A. paludicola, from which it can be separated based on differences in morphological characters and internal transcribed spacer sequence. In Bayesian inference using sequences of the aforementioned genomic fragment, the new species formed a clade with A. agrostis, A. funesta, A. graminis, A. phalaridis and some unidentified isolates, with robust Bayesian posterior probability (BPP). The morphologically closest species, A. paludicola, occupied a separate position, outside of the clade containing the new species. The sequences of two other genomic fragments, 18S and 28S rDNA (D2/D3 region) were also made available for the new species. Morphological comparisons of the new species with the related species are discussed.     

Diversity,spatial variation,and temporal dynamics of virulences in the German leaf rust (<Emphasis Type="Italic">Puccinia recondita</Emphasis> f. sp. <Emphasis Type="Italic">secalis</Emphasis>) population in winter rye

A large collection of German rye leaf rust isolates was analysed to characterize the diversity, spatial variation and temporal dynamics of virulences. Virulence-avirulence phenotypes (=pathotypes) were determined on 23 host differentials. We found 93 pathotypes among 177 single-uredinial isolates in 2000, 201 pathotypes among 437 isolates in 2001, and 125 pathotypes among 213 isolates in 2002. In total, the 827 analyzed isolates represented 317 pathotypes. Frequency of virulences on the individual differentials varied from 2% to 97%. Eight of the differentials showed a high resistance level with virulence frequencies <10%. Virulence complexity of the isolates ranged from 3 to 21 with a mean of nine. The percentages of highly virulent isolates (>14 virulences) increased from 4 to 15% during the sampling period. A high level of virulence diversity was observed within and between individual sampling sites with Simpson indices around 0.9. Evenness indices ranged from 0.88 to 0.92. Four of the five most frequent pathotypes were found in each year but their frequency never exceeded 10%. Isolates with unusual virulence combinations could be clearly separated by principal component analysis. Location-specific pathotype frequencies were revealed in each year, but the frequency patterns varied across years. On four fields a considerable increase of highly virulent pathotypes occurred within 6 weeks during the epidemic. The high diversity of pathotypes as well as the fast accumulation of highly virulent pathotypes favour the adaptation of the pathogen to race-specific host resistances. More durable resistance might be achievable by combining new effective race-specific resistances with adult-plant and/or race-non-specific quantitative resistances.     

The status of Rhoptrobothrium Shipley et Hornell, 1906 (Cestoda: Tetraphyllidea), with redescription of the type species, R. myliobatidis, and description of three new species from two species of Aetomylaeus (Myliobatiformes: Myliobatidae) from Malaysian Borneo

As part of a metazoan parasite survey of elasmobranchs from Malaysian Borneo, specimens of Rhoptrobothrium Shipley et Hornell, 1906 were collected from the eagle rays Aetomylaeus maculatus (Gray) and Aetomylaeus niehofii (Bloch et Schneider). The type species is redescribed from its type host, and a neotype specimen is designated. In addition, three new species of Rhoptrobothrium are described: R. chongi sp. n., R. gambangi sp. n. and R. limae sp. n. Rhoptrobothrium myliobatidis conspicuously differs from the three new species in its lack of a secondary areola; R. limae is distinguished from R. chongi and R. gambangi based on its greater total length; R. chongi possesses conspicuously stalked remi, while R. gambangi possesses short remi, often folded anteriorly. Rhoptrobothrium is somewhat unusual among tetraphyllideans in its possession of a "metascolex," a character it shares with other taxa in the Thysanocephalinae (i.e., Myzocephalus Shipley et Hornell, 1906, Myzophyllobothrium Shipley et Hornell, 1906 and Thysanocephalum Linton, 1889). The morphology of the "metascolex" of Rhoptrobothrium is investigated and new terminology is suggested to standardise the names given to structures constituting a metascolex. As a result, Rhoptrobothrium is considered to possess cephalic peduncle extensions, termed remi. In Rhoptrobothrium, each remus bears, at its distal end, a primary areola, and, in the case of the three new species, also a secondary areola proximal to the primary areola. Myzocephalus and Myzophyllobothrium are tentatively considered to possess remi; the configuration of the "metascolex" of Thysanocephalum, however, is not considered homologous to the condition in the other three genera currently placed in the Thysanocephalinae.     

Potential of zimtaldehyde, 4-allyl-anisol, linalool, terpineol and other phytochemicals for the control of the confused flour beetle (Tribolium confusum J. d. V.) (Col., Tenebrionidae)

Toxicity and repellency effects of several pure compounds (of plant origin) against the confused flour beetle (Tribolium confusum) were investigated in a filter paper test. The compounds were α-pinen, β-pinen, 4-allyl-anisol, camphor, 1,8-cineol, eugenol, linalool, menthol, piperin, terpineol, thymol and zimtaldehyde. Five compounds (4-allyl-anisol, linalood, terpineol, thymol and zimtaldehyde) caused enough mortality of this insect to allow the determination of LD₅₀ and LD₉₅ values. Zimtaldehyde and 4-allyl-anisol showed the strongest toxicity effects with LD₅₀ values of 0.04–0.05 μl/cm² within an exposure period of 24 h. When the isolated fumigant effects were tested by separating the insects from the filter paper, the toxicity of zimtaldehyde (LD₅₀=0.29 μl/cm²) was much lower than that of 4-allyl-anisol (LD₅₀=0.10μl/cm²).     

Monogenoids from the gills of spiny eels (Teleostei: Mastacembelidae) in India and Iraq, proposal of Mastacembelocleidus gen. n., and status of the Indian species of Actinocleidus, Urocleidus and Haplocleidus (Monogenoidea: Dactylogyridae)

Mastacembelocleidus gen. n. (Monogenoidea: Dactylogyridae) is proposed to include two species collected and redescribed from spiny eels (Mastacembelidae) in India and Iraq: Mastacembelocleidus bam (Tripathi, 1959) comb. n. (syn. Ancyrocephalus bam Tripathi, 1959) from the gills of Macrognathus pancalus (new host record) and Macrognathus aculeatus (Synbranchiformes: Mastacembelidae) from Lucknow, India; and Mastacembelocleidus heteranchorus (Kulkami, 1969) comb. n. (syn. Urocleidus heteranchorus Kulkarni, 1969) from the gills of Mastacembelus armatus from Lucknow, India, and Mastacembelus mastacembelus (new host record) from the environs of Erbil, Iraq (new locality record). Urocleidus rhyncobdelli Jain, 1959, Haliotrema tandani Agrawal et Singh, 1982 and Urocleidus raipurensis Dubey, Gupta et Agarwal, 1992 are considered junior subjective synonyms of M. bam.     

Lyctidae (Coleoptera) of Israel, their damage and its prevention

Seven species of Lyctidae are recorded from Israel:Lyctus linearis (Goeze) andL. planicollis Le Conte for the first time; as well asL. africanus Lesne;L. brunneus (Stephens);L. parallelocollis Blackburn;Minthea rugicollis Walker;Trogoxylon impression (Comolli); andAcantholyctus comifrons Lesne for the first time from Sinai. The extent of damage and its reduction and prevention are described.     

Check-list for scientific names of common parasitic fungi. Supplement Series 2a (additions and corrections): Fungi on field crops: Beet and potato; caraway,flax and oil-seed poppy

This paper supplements Series 2a (Neth. J. Pl. Path. 82 (1976) 193–214) and documents the nomenclature of an additional four parasitic fungi. The data of sixteen fungi (teleomorph and/or anamorph) previously treated in Series 2a have been brought up to date and in accordance with the recent changes in the International Code of Botanical Nomenclature (‘Sydney Code’). One new combination is proposed, viz.Uromyces beticola (Bellynck) Boerema et al. The scientific names used in official publications of the Netherlands Society of Plant Pathology and the Netherlands Ministry of Agriculture and Fisheries conform with those selected in the check-list.     

Cytochrome P-450 in insects. 7. Age dependency and phenobarbital induction of cytochrome P-450, P-450 reductase,and monooxygenase activities in the black blow fly (Phormia regina,Meigen)

Development and phenobarbital (PB) induction of microsomal cytochrome P-450, NADPH-cytochrome c (P-450) reductase, two epoxidation, and two O-demethylation activities were examined in chronologically timed populations of female black blow flies (Phormia regina, Meigen). Measurements of these enzymes started with the pharate adult stage and ended 5 days following eclosion. Induction occurred in all enzymes, even at 0.005% PB, and was maximum at 0.15%. Dramatic induction of the O-demethylation of 7-methoxy-4-methylcoumarin was observed in flies dosed with the maximum concentration of the drug. This monooxygenase activity increased to nearly 1400 times the level in control flies, whereas the other O-demethylation (methoxyresorufin) and the two epoxidation reactions exhibited considerably less change. Induction of the structural enzymes of this enzyme system were 10-fold for cytochrome P-450 and 5-fold for NADPH-cytochrome c (P-450) reductase. These data suggest that PB induces several P-450's in the blow fly, particularly one bearing a high degree of specificity for 7-methoxy-4-methycoumarin.     

Cultural, molecular and pathogenic variability of Mycosphaerella pinodes and Phoma medicaginis var. pinodella isolates from dried pea (Pisum sativum) in France

The characteristics of 50 isolates of Mycosphaerella pinodes and 17 isolates of Phoma medicaginis var. pinodella , originating from several regions of France where ascochyta blight is prevalent, were investigated using cultural, physiological, molecular and pathogenicity analyses. M. pinodes was distinguished from P. medicaginis var. pinodella on the basis of presence of pseudothecia, a higher proportion of larger, bicellular conidia, compared with the smaller, predominantly unicellular conidia of P. medicaginis var. pinodella , and a slower linear growth rate on agar under a 12-h light regime. RAPD analysis clearly distinguished the two species, which had low intraspecific variability. Although both species gave identical symptoms, they could be distinguished by their incubation period and aggressiveness, respectively, shorter and higher for M. pinodes . Virulence tests gave no definitive evidence for the existence of pathotypes among the M. pinodes isolates. Two unidentified isolates had similar characters to both M. pinodes and P. medicaginis var. pinodella in some features but were distinguished from them by their RAPD patterns.     

Detection of Pseudomonas syringae pv. actinidiae using polymerase chain reaction (PCR) primers based on the 16S–23S rDNA intertranscribed spacer region and comparison with PCR primers based on other gene regions

Several published polymerase chain reaction (PCR) primers to identify Pseudomonas syringae pv. actinidiae, the causal organism of bacterial canker of kiwifruit, were found not to be specific. Two new sets of PCR primers, PsaF1/R2 and PsaF3/R4, were designed to be complementary to a portion of the 16S–23S rDNA intertranscribed spacer (ITS) regions. These primers amplified a DNA fragment from strains of P. syringae pv. actinidiae, but not from 56 strains of bacteria from six genera and 17 species, except for a strain of the tea pathogen, P. syringae pv. theae. When tested against DNA extracted from a further 20 strains from Japan, Korea, Italy and the USA deposited in culture collections as P. syringae pv. actinidiae, all except six cultures produced the expected product of 280 bp with PsaF1/R2 and 175 bp with PsaF3/R4. Results of multilocus sequence analysis using five housekeeping genes (gyrB, acnB, rpoD, pgi and cts) showed that none of these six strains was phylogenetically similar to P. syringae pv. actinidiae. In contrast to the P. syringae pv. actinidiae type strain, these strains were positive in the determinative tests for ice nucleation and syringomycin production. It is suggested that these six strains were incorrectly identified as P. syringae pv. actinidiae. It was not possible to distinguish P. syringae pv. actinidiae from the phylogenetically similar P. syringae pv. theae using the ITS, gyrB, acnB, rpoD, pgi or cts gene regions to design PCR primers. Because P. syringae pv. theae is unlikely to be found on kiwifruit, primers PsaF1/R2 and PsaF3/R4 are recommended for screening bacteria isolated from kiwifruit tissue.     

Development of a specific assay using RISA for detection of the bacterial agent of 'basses richesses' syndrome of sugar beet and confirmation of a Pentastiridius sp. (Fulgoromopha, Cixiidae) as the economic vector

A technique for the specific diagnosis in insects of SBRp (the γ-3 proteobacterium associated with the syndrome 'basses richesses' (SBR) of sugar beet crops in eastern France), using the RISA (rDNA intergenic spacer analysis) technique, was developed. PCR using the Alb1/Oliv1 primer pair specifically amplified a 16S-ITS region of SBRp and produced a characteristic DNA fingerprint. This PCR assay did not detect other closely related organisms, including the Arsenophonus endosymbiont of Diaphorina citri , the secondary endosymbiont of Glycaspis brimblecombei , or ' Candidatus Phlomobacter fragariae', a related phytopathogenic γ-3 proteobacterium. Six different ribosomal operons, differing in their ITS region or partial 16S sequence, were identified in SBRp. PCR amplification with Alb1/Oliv1 of DNA samples from Hemiptera species (suborders Fulgoromorpha and Cicadomorpha) collected in sugar beet fields confirmed Pentastiridius sp. as the economic vector of SBR disease. The high percentage of field- Pentastiridius sp. specimens which tested positive for SBRp reflected the importance of SBR disease in sugar beet crops. This is the first time that the RISA technique has been used as a diagnostic test for a plant pathogenic bacterium in insects.