Yield Loss Caused by Heterodera avenae in Cereal Crops Grown in a Mediterranean Climate1

In south-eastern Australia, where large areas of cereal crops are grown in a Mediterranean climate, yield loss caused by Heterodera avenae is generally more severe than in Northern Europe. This appears to be due to differences in seasonal cropping patterns and the stages of crop growth when roots are exposed to larvae. Field observations and laboratory experiments show that, in Australia, crops ≪ sown early ≫, in late autumn, are less damaged than those ≪ sown late ≫. This is explained by the times of emergence and population density of larvae, by the nematode-fungus interaction and by the environmental conditions affecting plant growth, rather than by differences in the nematode or in host tolerance.     

Distribution of Cereal and Grass Cyst Nematodes in the Federal Republic of Germany1

A survey of cereal and grass cyst nematodes in the Federal Republic of Germany revealed that Heterodera avenae is the most widely distributed heteroderid species and common mainly in areas with light sandy soils and intensive cereal cultivation. The so-called ≪race 3 ≫ was recovered several times, and other populations differing morphologically from ≪ typical ≫ H. avenae were found. H. hordecalis, H. bifenestra, H. mani, H. iri and Punctodera punctata were also recovered in many parts of the country. In arable soils these species constituted only 7 % of all records of cereal and grass cyst nematodes, whereas they prevailed in grassland, forests and other habitats, where they amounted to almost 80 % of the records. 93 % of all H. avenae records came from agricultural soils, but only 21 % of the records of the five other species. H. hordecalis and H. bifenestra are obviously of no economic importance in FRG.     

Biological Control of Plant Pathogens: Present Status and Perspectives in Italy

Interest in the biological control of plant pathogens has been increasing in Italy in the last few years. Current or completed research programmes at some University and/or CNR (National Research Council) Institutions concern the following topics: a) biological control of crown gall with Agrobacterium radlobacter strain 84; b) biocontrol of some forestry diseases caused by fungi; c) integrated biological control of grey mould on grapevine; d) biocontrol of Fusarium dry rot on maize and sorghum and of Rhizoctonia rot on eggplant and tomato with Trichoderma viride; e) seed and root≪ bacterization ≫ as a means of biological control of some fungal diseases of horticultural plants; f)≪ suppressive ≫ effect of some Italian soils to Fusarium oxysporum f.sp. dianthi : g) biologically induced resistance against bacterial, fungal and viral diseases. In this contribution, the results obtained are reported, together with comments on the prospects for practical application of each type of biological control. Evaluation of the reduction in the use of pesticides against the same pathogens is not currently possible, owing to lack of data (except for programmes b) and c) above). Biological control will only become a common and widespread agricultural practice if a number of conditions are satisfied, including the establishment of registration guidelines for microbial and viral pesticides. The criteria for the evaluation of biological control organisms in the agricultural environment must be revised and the technical-legislative problems must be solved. A Commission in the European Community is currently examining the question.     

Suggestions for Determination and Terminology of Pathotypes and Genes for Resistance in Cyst-forming Nematodes, especially Heterodera avenae1

A short review of differentiation into pathotypes is given. Use of the word ≪ pathotype ≫ is recommended when a very clear difference is established between virulence of nematode populations. Our present knowledge makes it possible to differentiate between 10 pathotypes of Heterodera avenae. It is suggested that the pathotypes are given numbers, and corresponding terms should be used for genes for resistance in plants, e.g. a gene Hal on the barley chromosome gives resistance to nematode pathotypes 11,21,31,41 etc. Some proposals for improvement of pathotype identification are given.     

Cereal and Grass Hosts of Some Gramineous Cyst Nematodes1

The host ranges of some British populations of cyst nematodes from cereals and grasses have been studied. The nematodes were isolated from agricultural and natural habitats. Their morphology corresponded to the Heterodera avenaeImani type, to ≪ pathotype 3 ≫, or to the H. hordecalisIlatipons type. The host series included barley, oats and wheat, some of which were known to be resistant to H. avenae pathotypes, and agricultural and wild grasses. Many of the H. avenae-resistant cereals were susceptible to pathotype 3 and to a population resembling H. avenae I mani, which had a very wide host range including grasses. The population of H. hordecalis, collected from grasses, also overcame the resistance of gene Rha2. Two populations of H. mani reproduced to a limited extent on cereals, and showed a clear preference for grass hosts. A third H. mani population reproduced only on grasses. The results draw attention to some problems in conducting and interpreting tests with many different hosts and nematodes. They reinforce the view that these gramineous cyst nematodes are a species complex, with variations in host range, as well as in morphology and biology.     

Jectarow - A Commercial Unit for Applying Low Volumes of Toxicants to the Seed Furrow of Row Crops1

Jectarow was developed specifically to apply EDB at low volume into the cereal seed furrow for Heterodera avenae control. It has since been used successfully to apply a range of other toxicants. These include liquid formulations of the soil fumigants chloropicrin, and formalin, and emulsions of the fungicides quintozene and etradiazole and the insecticide chlorpyrifos. Suspensions of the powder formulations of captan and chlorothalonil have also been applied successfully using the microtube applicator. Other potential applications of Jectarow may include growth regulators, Rhizobium cultures, trace elements, fertilizers or nitrification inhibitors. Perhaps this machine offers the opportunity to inoculate antagonistic or competitive non-pathogenic cultures into a required soil zone. Jectarow has the advantage that highly toxic compounds can be considered as being contained in a ≪ closed system ≫ Jectarow is a low cost machine that sells to the Australian farmer for $A 215–470 depending on the size of his cereal seed drill (16–120 rows). It is probable that in sophisticated agricultural systems several Jectarows could apply different toxicants on the same machine in the same crop simultaneously.     

Polymorphisme génétique chez Heterodera avenae1

On a étudié par l'électrophorèse la variabilityé de certains enzymes avec l'idée de trouver des caractéres plus commodes pour la distinction des pathotypes. Les premiers resultats font apparaître qu' Heterodera avenae , contrairement à ce qui a été observé chez le genre voisin Meloidogyne , est très polymorphe pour les quatre premiers enzymes déjà analyses, soit: deux estérases, la malate déhydrogénase (MDH) et les phosphatases acides. Les differences d'une population à l'autre semblent pour l'instant plutôt se situer au niveau du nombre d'allèles presents et de leurs fréquences respectives dans chacune d'elles. Différents phénomènes biologiques ont été parallèlement mis en évidence comme l'≪ inbreeding ≫à faible densité de population ou la fécondation effective d'une femelle par plusieurs mâles.     

Resistance de l'avoine a Heterodera avenae. Methodes de selection et sources de resistance1

Deux sources de résistance ont été utilisées pour la sélection de lignées &d'avoines résistantes à Heterodera avenae: CI 3445 et Nelson. Seules des descendances àrésistance intermédiaire (quelques kystes par plante) ont pu être sélectionnées au départ de CI 3445. En revanche, des lignées totalement résistantes ont pu être produites á partir de Nelson. Une méthode &d'évaluation de la résistance permettant &d' examiner rapidement un grand nombre de plantes s'est révélée discriminante pour les lignées hotes. Elle n'a pas permis de différencier les lignées totalement résistantes des lignées àrésistance intermédiaire. Cette méthode peut être appliquée au ≪ screening ≫ des lignées en cours de sélection. Elle doit être répétée pendant deux ou trois générations en raison du caractére bigénique et dominant de la résistance. Il est nécessaire, pour caractériser avec précision le degré de résistance des lignées en fin de sélection, de faire appel àune méthode plus normalisée, basée sur &l' utilisation de substrats artificiellement infestés et le dénombrement complet des kystes formés sur le système racinaire.     

Analysis of selected singleton transposable elements (SSTEs) and their application for the development of land PATE markers in Magnaporthe oryzae

Transposable elements (TEs) are distributed throughout the genome and play an important role in genome variation of the rice blast fungus, Magnaporthe oryzae. TE-associated molecular markers have been developed and used extensively for diversity analysis in natural populations. Here, we investigated the genomic distribution of a selected group of TEs that are dispersed as singletons, and each is of a size feasible for PCR validation, designated as SSTEs, in the genome of the reference laboratory strain, 70-15. The 75 SSTEs identified were distributed evenly on seven chromosomes of the M. oryzae genome. Approximately 40 % of SSTEs were located either in the coding or promoter regions of the predicted genes. The presence or absence of each SSTE at the respective locus was assessed, resolving significant presence/absence polymorphism among 11 rice blast strains collected from different locations worldwide. The presence/absence (P/A) polymorphism of SSTEs in different strains suggests that they may be useful for developing map-based land PATE markers for genetic analysis in M. oryzae.     

A qualitative quick-test for detection of herbicide resistance to tribenuron-methyl in Papaver rhoeas

A qualitative seed-based method useful for the detection of resistance to the herbicide tribenuron-methyl in Papaver rhoeas L. is described. Seeds were germinated on 35 mL of a 1.3% agar medium containing 2 g KNO₃ L^–1 in 8.5 cm Petri dishes in a growth chamber under 20 μmol s^–1 m^–2 of fluorescent light. When 0.24 μM tribenuron-methyl or more was added, growth in susceptible plants stopped after the cotyledon stage and they turned chlorotic. The resistant plants continued developing new leaves. The same effect was achieved when 0.2 g gibberellin (GA₃) L^–1 and 7.68 μM tribenuron-methyl or 0.5 g GA₃ L^–1 and 61.44 μM tribenuron-methyl were added. Germination percentage rose with gibberellin in the presence or absence of the herbicide. Plants developed rapidly, with only about 14 d needed to finish the test but sometimes root growth was reduced because of the addition of gibberellin. In the absence of gibberellin but in the presence of the herbicide, plants grew more slowly and developed smaller leaves with a 17-d evaluation period requirement. The test was validated with pot experiments in a greenhouse and also with field trials. The best combination was found to be 0.2 g GA₃ L^–1 and 7.68 μM tribenuron-methyl, assuring homogenous germination and testing of dormant seeds but avoiding root inhibition associated with too much gibberellin.     

大草蛉触角感器的扫描电镜观察

利用扫描电镜对大草蛉雌、雄成虫触角进行了亚显微结构的观察与分析,旨在为揭示其嗅觉与行为的关系奠定基础。结果表明大草蛉触角为线形,共3节,即柄节、梗节和鞭节,其中柄节和梗节均为单节,而鞭节由116个亚节组成。雌、雄触角总长度分别为（1.52±0.08）和（1.58±0.23）cm,鞭节长度分别为（1.44±0.04）和（1.47±0.13）cm。触角感器共有4种,分别是毛形感器、锥形感器、刺形感器和Böhm氏鬃毛。其中毛形感器为触角上分布最广、长度最长的感器,共有4种类型,锥形感器有3种类型。感器主要分布在鞭节部位,且布满整个触角表面。雌、雄个体之间触角感器种类、结构、数量、分布均无明显差异,但个别感器长度存在显著差异。根据感器形态学结构特点推测不同感器功能不同。     

Daniconema anguillae gen. et sp. n., a new nematode of a new family Daniconematidae fam. n. parasitic in European eels

A new nematode genus and species, Daniconema anguillae gen. et sp. n., is described from the serosa of the swimbladder and from the intestine of eels (Anguilla anguilla (L.] from Denmark (Lake Esrum, northern Zealand); a new family Daniconematidae fam. n. is established to accommodate it. The hitherto monotypic family Daniconematidae shows affinities with the Skrjabillanidae; in contrast to the latter, the new family is characterized by the absence of a buccal capsule, by the presence of anus in the female, and by different structure of the male tail (shape of the tail, absence of bursa-like caudal alae, number and distribution of papillae, presence of the peculiar genital projection). D. anguillae has recently been recorded also from eels in Czechoslovakia (Mácha Lake, northern Bohemia).     

Extended survival of Puccinia graminis f. sp. tritici urediniospores: implications for biosecurity and on‐farm management

Puccinia graminis f. sp. tritici (Pgt), the causal organism of stem rust, is of global importance across wheat‐growing countries. However, some epidemics commence without the obvious presence of ‘alternate’ or ‘green bridge’ hosts, suggesting urediniospores can survive in the absence of suitable host plants for many weeks. Testing a range of inert material types, including metals, plastics, fabrics and woods, highlighted a significant effect of material type and temperature on urediniospore viability (P < 0.001), with urediniospores remaining attached and viable on these materials (aluminium, paper, rubber, all fabric and all woods) for up to 365 days at 23/8 °C day/night. At 36/14 °C day/night, urediniospore viability was retained for a maximum of 300 days on denim and jute. Furthermore, at 45/15 °C day/night, urediniospores remained viable for a maximum of 180 days on cotton and jute. The frequency of recovery of attached urediniospores was also dependent upon the material type, with significant differences between materials in their abilities to retain urediniospores after washing (P < 0.001). Urediniospores recovered even after 300 or 365 days from the lower two temperature regimes successfully initiated infections of wheat seedlings. Results confirm the potential importance of inert materials as long‐term carriers of viable Pgt urediniospores, highlighting risks of spread of new pathotypes and strains across wheat‐growing regions, the significant biosecurity implications for contaminated carrier materials, and its likely survival across seasons without a host.     

Genetic variation in tolerance of host monoterpenes in a population of the ascomycete canker pathogen Crumenulopsis sororia

Twenty families of single-ascospore isolates of the canker pathogen Crumenulopsis sororia were collected from eight trees of Pinus sylvestris in a native pinewood. Measurements were made of growth rate of each isolate in the presence and absence of a saturating atmosphere of the five principal monoterpenes of P. sylvestris cortical oleoresin (α-pinene, β-pinene, 3-carene, β-myrcene and limonene).
All monoterpenes significantly reduced the mean linear growth rate of the C. sororia population. However, there was highly significant genetic variation among isolates in their tolerance of all five monoterpenes. The extent of genetic variation was greatest for β-myrcene and limonene tolerance, and least for α-pinene and 3-carene tolerance. Significant positive correlations between tolerance of different monoterpenes were found, implying the presence of tolerance mechanisms common to a range of compounds.     

Virulence characteristics of Bremia lactucae populations in Norway

Use of resistant cultivars represent an efficient control measure for lettuce downy mildew (Bremia lactucae), although the durability of presently deployed resistance genes remains uncertain. Our objective was to document the pathogenic diversity of B. lactucae isolates in Norway. A total of 69 isolates of B. lactucae were collected between 2001 and 2006 from 65 commercial fields and four greenhouses in southeastern and southwestern Norway and tested for the presence of one or more of 19 virulence factors (v-factors). Phenotypic diversity was calculated based on presence or absence of v-factors, and as an overall comparison of v-phenotypes for each isolate. Disease severity varied over the years of the study, and epidemics were most consistently severe in southeastern Norway. The most commonly occurring v-factors, in order of frequency, were v5/8, v7, v2, v18, v4, v13, v6, v11, v12, v1 and v10. Virulence factor v17 was not found, while v36 was found in one isolate only. A total of 44 different v-phenotypes were identified within the population represented by the 69 isolates, yielding an incidence of unique virulence types of 63 %; a relatively high level of pathogen diversity. Four of the identified v-phenotypes were identical to races Bl:17, 18, 22 and 24, which have been previously reported in European populations of B. lactucae. The variability of the Norwegian B. lactucae populations verifies the genetic flexibility of this pathogen and its great ability to adapt to changes in host plants and surrounding conditions.     

Avian regulation of crop and forest pests,a meta-analysis

BACKGROUND

Birds have been shown to reduce pest effects on various ecosystem types. This study aimed to synthesize the effect of birds on pest abundance, product damage and yield in agricultural and forest systems in different environments. Our hypothesis is that birds are effective pest regulators that contribute to a reduction in pest abundance, enhancement of yield quality and quantity and economic profit, and that pest regulation may depend on moderators such as the type of ecosystem, climate, pest, and indicator (ecological or economic).

RESULTS

We performed a systematic literature review of experimental and observational studies related to biological control in the presence and absence of regulatory birds. We retained 449 observations from 104 primary studies that were evaluated through qualitative and quantitative analyses. Of the 79 studies with known effects of birds on pest regulation, nearly half of the 334 observations showed positive effects (49%), 46% showed neutral effects, and very few (5%) showed negative effects. Overall effect sizes were positive (mean Hedges’ d = 0.38 ± 0.06). A multiple model selection retained only ecosystem and indicator types as significant moderators.

CONCLUSION

Our results support our hypothesis that there is a positive effect of avian control of pests for each analyzed moderator and this effect was significant for both ecological and economic indicators. Avian regulation of pests is a potential effective approach for environmentally friendly pest management that can reduce pesticide use regardless of the context of implementation. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Persistence to rainwashing of DDT wettable powders

The amounts of DDT removed by ‘rainwashing’ deposits of wettable powders on glass or cotton leaf surfaces were greatly diminished if the powders were formulated with amine stearates. The age and the density of the deposit affected retention to a lesser degree. Rates of loss by ‘rainwashing’ the deposits from both types of surface could be described in general terms by double exponential equations. The initial rate at which DDT penetrated into cotton leaves, but not the amount that penetrated after several weeks in the laboratory at 20°c, was influenced by the presence of amine stearates in the formulation (which formed stearic acid in the deposits). The proportional amounts, and the total amounts, of DDT that penetrated from these unweathered deposits depended on the deposit density.     

Survival in the phylloplane of an introduced biocontrol agent (Trichoderma harzianum) and populations of the plant pathogenBotrytis cinerea as modified by abiotic conditions

Leaf populations ofTrichoderma were studied on tomato, pepper and geranium plants incubated under various conditions. Treatments involved high (>90%) or lower (75–85%) relative humidity (r.h.), temperatures of 15±3°C or 25±3°C, and soil fertilization with formulations of 2,2,5%, 3,3,8% or 5,3,8% NPK. The size of populations on leaves treated with the fungusTrichoderma harzianum differed according to plant species, leaf age, length of incubation, atmospheric conditions, and plant nutrition.T. harzianum populations were promoted in many cases by high r.h. and by 3,3,8% NPK. Interactions of introduced populations ofBotrytis cinerea with populations ofT. harzianum on tomato leaves under combinations of the above conditions showed that the population ofB. cinerea wasca tenfold lower in the presence ofT. harzianum than in the absence of this fungus.     

Some characteristics of an avocado strain of Tobacco mosaic Virus

An isolate of tobacco mosaic virus (TMV-A) was obtained from healthy and sunblotch-infected avocado (Persea americana) seedlings. TMV-A resembled common TMV in particle morphology, RNA size and coat protein molecular weight. TMV-A coat protein differed from common TMV coat by a minimum of 22 amino acid exchanges including the presence of one methionine, and by the absence of cysteine. Spur formation between the precipitation lines of TMV, TMV-A and a TMV antiserum indicates certain differences among the antigenic determinants of these two strains.     

Uptake of chemicals from foliar deposits: Effects of plant species and molecular structure

The uptake from foliar deposits of 10 ¹⁴C-labelled compounds into each of 10 species of field-grown plants was measured 26 h after deposition by combustion of leaf tissue after removal of surface deposits. The compounds, which included eight pesticides, covered a wide range of lipophilicity and each was formulated in the same way; they were applied as droplets with a microsyringe. Uptake varied greatly between the species. All compounds were taken up well into maize and Xanthium pennsylvanicum, whereas relatively little entered the leaves of apple or orange. Uptake into the six other species varied according to the compound. Amongst the eight non-polar compounds, no relationship between the rate of uptake and molecular size was discerned, and only in X. pennsylvanicum was uptake related to the partition coefficient and water solubility. Considering all the compounds, weak relationships were observed between molecular cross-sectional area and uptake into four species. The range of the uptake rates (×130) was small compared with those of octan-1-ol-water partition coefficients (×10¹⁰) and water solublities (×10⁷) shown by the 10 compounds. Possible reasons for the absence of correlations between the uptake and the molecular properties considered are discussed. The results are consistent with either separate routes of cuticular entry for non-polar and polar compounds, or a common route for both types of compound. The generally poor uptake by apple and orange leaves, which may be related to their thick cuticles, highlights the need to develop special formulations to optimise uptake into these species.