Cereal Cyst Nematode and N Fertilization1

The effect of increasing amounts of nitrogen on the propagation of the cereal cyst nematode was studied. Nitrogen applications as nitro-chalk ranged 0–1,500 kg/ha (0–232.5 kg N/ha). Maximum propagation was obtained at about 46.5 kg N/ha. Increasing N doses reduced propagation to about 1/2 - 1/3 of the maximum. Two factors seem to be involved: 1) reduced fertility of females with increasing N application and 2) apparently fewer females developed with N applications greater than 46.5 kg/ha. Hatching in solution of calcium nitrate decreased with increasing concentration.     

湖北和广东按蚊线虫分布初步调查

四川罗索线虫（Romanomermis sichuansis）是专性寄生于按蚊体内的水生索科线虫之一，其宿主中华按蚊（Anophelesin sinensis）、嗜人按蚊（A．anthropophgus）、大劣按蚊（A．dirus）等都是疟疾的重要传播媒介。稻田是按蚊幼虫的主要栖息地。作者于2002-2004年连续3年在湖北枣阳琚湾和广东徐闻市郊对该线虫的分布特点做了初步的调查与分析。     

Identification of Pathotypes of the Potato Cyst Nematode1

Since the discovery of pathotypes of the potato cyst nematode (Heterodera rostochiensis Wollenweber, 1923), surveys on the distribution of these pathotypes have been carried out in different European countries. Test varieties of potato were selected according to findings resulting in the present situation of varying distinctive host-plants and of diverging programs for breeding potatoes resistant to the potato cyst nematode. With respect to rational selection and use of resistant potato varieties, there is a great need for standardization in pathotype identification (nomenclature), maintenance and supply of appropriate genotypes of Solanum species and methods for testing resistance in new potato varieties. Anticipating a cross-experiment with pathotypes and test varieties from Great Britain, the Federal Republic of Germany and the Netherlands in 1974, a preliminary test with all recognized or presumed pathotypes from these countries, but with only part of the potential differential host-plants was carried out by the Plant Protection Service at Wageningen. The results of this experiment are discussed.     

Cereal Cyst Nematode, Soil Heating and Fungal Parasitism1

Experiments on winter heating of cereal cyst nematode-infested soil have been carried out during 4 years on light loam in eight concrete pipes (l-m diam.) dug into the soil. The soil in four of the pipes was heated to a temperature of 5oC during the winter periods. Temperature was measured at a depth of 5 cm. The heating was carried out by means of buried electrical cables. Soil temperature in the remaining pipes followed the natural fluctuation. The host plant was Sun II oats. Statistical analysis of the results for all the years together showed that the propagation of nematode populations was significantly lower in heated than in non-heated plots. Investigation of soil samples in spring and autumn 1980 for eggs and larvae, as well as fungal parasitism of these, showed that numbers of eggs and larvae were significantly lower in heated than in non-heated plots and the percentage of parasitized eggs and larvae was significantly higher in heated than in non-heated plots. Verticillium chlamydosporium seems to be a main parasitic fungus.     

Vertical Distribution of the Plant-Parasitic Nematode, Pratylenchus penetrans, Under Four Field Crops

ABSTRACT The vertical distribution of Pratylenchus penetrans was monitored in four fields cropped with maize, black salsify, carrot, or potato. Soil samples were collected at 21-day intervals from May 2002 until April 2003 from five plots (2 x 5 m(2)) per field. Per plot, 15 cores were taken to a depth of 70 cm and split into seven segments of 10 cm each. Within the plots, segments from corresponding depths were pooled. After mixing, 200-g subsamples were taken and nematodes were extracted by zonal centrifugation from the root fraction and the mineral soil fraction separately. In most crops, the root fraction contained more than 50% of the total number of P. penetrans. Because the ratio between the numbers of nematodes in the root fraction and mineral soil fraction changes during the growing season, numbers of P. penetrans found in the mineral soil fraction cannot be used to estimate the total number in the soil. Therefore, both fractions have to be processed to obtain a reliable estimate of the density. No nematodes were recovered below 50 cm soil depth, except in the maize field where nematodes were found at 70 cm. The optimum sampling depth for maize, black salsify, carrot, and potato was 45, 25, 25, and 35 cm, respectively. The percentage of nematodes per soil layer was independent of the sampling date, indicating that a defined optimum sampling depth will be applicable throughout all seasons. The cumulative vertical distribution, modeled with a logistic equation, can be used to estimate the sampling error when samples are collected at different depths.     

The Golden Nematode (Heterodera rostochiensis Woll.) in Greece: History,Distribution, Economic Importance,Research and Phytosanitary Regulations1

Heterodera rostochiensis Woll. was reported for the first time in Greece in 1933, but was probably introduced from Europe before 1914. Its distribution in the country is restricted, mainly to isolated fields; many districts still remain uncontaminated. In 1972, about 7–12% of the area cultivated with potatoes was infested with H. rostochiensis, and the damage caused was estimated to be 1.6-2.4% of the total annual yield. Only few experiments have been carried out on biology, Control and other aspects. Domestic and international phytosanitary regulations for combatting this nematode are in force.     

嗜菌异小杆线虫的分离鉴定及生物学特性分析

为了发掘具有耐高温特性的昆虫病原线虫,本实验室对在山东地区采集的122份土样进行了线虫分离,得到异小杆线虫JNR,扩增其ITS基因和D2-D3基因,并构建系统进化树,分析可得:线虫JNR与嗜菌异小杆线虫Heterorhabditis bacteriophora在同一分支,同源性达到98%以上,为嗜菌异小杆线虫品系。为进一步了解该线虫品系的生物学特性,本试验研究了其侵染力、高温耐受力及水平运动能力。结果表明,线虫JNR有较好的耐热性,38℃条件下处理16 h,存活率最高54%,24 h时为32%;40℃水浴处理2 h,低浓度500 IJs/mL下存活率28%,3 h后全部死亡。对大蜡螟和小菜蛾的生测结果显示,在10、15、20、25、30、35、40、60、120、240 IJs/头剂量下处理24 h,蔬菜害虫小菜蛾先出现死亡,大蜡螟则在48 h后出现死亡;大于20 IJs/头剂量下,处理48 h后线虫对大蜡螟的校正死亡率达到59.5%,高于对小菜蛾的侵染效果。在剂量120 IJs/头以上,72 h后寄主的校正死亡率均能达到100%。异小杆线虫JNR在30℃条件下水平运动能力比在18、25℃时强,48 h时有31%的个体运动到3.6 cm处。以上研究表明,该线虫有较强的侵染力,特别是在温度相对较高时具有较好的耐热力和水平运动能力,对防治蔬菜田小菜蛾具有应用开发潜力。     

我国松材线虫及其传媒昆虫的生物防治

本文介绍我国近年来在松材线虫及其传媒昆虫松墨天牛的天敌昆虫、病原微生物、植物性杀线活性物质,以及松墨天牛的引诱剂等方面的研究进展。     

大豆胞囊线虫病生物防治研究进展

本文概述了国外对大豆胞囊线虫病生物防治方面的研究及其进展。     

Distribution quality of orchard sprayers1

Studies of the variability of initial deposition on leaves from orchard sprayers showed that both minimum and maximum values and the coefficient of variation of the amounts deposited increased in a linear manner with the application rate. The minimum and maximum amounts of deposit are important for biological efficacy, potential development of resistance. determination of the dose rate and effects on beneficial organisms. Measurements of the amounts deposited on leaves at different tree heights showed that the reproducibility of curves is considerably interfered with by random effects. There was not always a connection between these curves and measurements on a lamellate vertical distribution test stand. Measurements of vertical distribution from a fixed position differed considerably from those produced with forward movement.     

昆虫病原线虫JLSY 003的鉴定及其生物学特性测定

经28S rDNA和ITS序列分析,从吉林省松原市土样中分离到的昆虫病原线虫JLSY 003为Oscheius myriophila品系.本研究以大蜡螟末龄幼虫为寄主,测定该线虫的生物学特性.结果表明,JLSY 003浓度为80IJs/larva时具有较高的侵染力,致死中时间LT50为15.409 h,侵染24、48h...     

Forecasting Crop Damage by Nematodes: Nematode Population Dynamics1

Factors affecting the ease or difficulty of forecasting and modelling cyst, root-ectoparasitic and soil surface nematodes are mentioned. To relate pre-planting to post-harvest populations of cyst nematodes, a version of the logistic curve is derived from first principles and modified to take account of the injury done to root systems as numbers increase, and of eggs carried over to the following year. Egg hatch, when potato or other crops are grown, appears to be independent of population density. So also does root invasion over the population densities encountered in field plots. In the absence of enemies, population density is determined by competition for feeding sites induced by females in the root system, and by the size of the root system. Population oscillations about the equilibrium point are affected mainly by the proportion of the population that fails to hatch and the damage to the root system. The process of model building and the parameters required are outlined. The model includes hypotheses relating to intraspecific (genetic) competition and interspecific competition. The limitations of models and the need to make them stochastic are discussed. L'article fait état des possibilites et difficultés rencontrees dam la prévision et la modelisation des populations de nematodes a kystes, de nematodes ectoparasites des racines, et de nematodes de surface. Afin detablir la relation entre les populations de nematodes a kystes avant le semis et apres la recolte, il est recouru a la courbe logistique, derivee des principes fondamentaux. Celle-ci se trouve modifiee afin de tenir compte des degits croissants subis par les racines en fonction de I'augmentation des populations et de la survie d'une partie des ceufs d'une annee a I'autre. L'eclosion des ceufs semble être independante de la densite des populations dans les champs de pommes de terre et de toute autre culture. Ceci s'applique egalement a I'invasion des racines, dans le cas des densites de populations observees dans les parcelles experimentales. En I'absence dennemis, la densite est determinee par la competition pour L'acces aux sites de nutrition que les femelles preparent dans les racines, et par L'importance du systeme radiculaire. Les ecarts de population observes a partir dun equilibre sont principalement dus a la proportion de la population non eclose et aux deggts subis par les racines. I1 est fait etat d'une modelisation, basee sur certains parametres essentiels. Le modele repose sur L'hypothese d'une concurrence intraspecifique (genetique) et interspecifique. Les limites des modeles sont considerees, ainsi que la necessite de passer a une approche stochastique.     

Genetic and Phenotypic Diversity in the Graminaceous Cyst Nematode Complex, Inferred from PCR-RFLP of Ribosomal DNA and Morphometric Analysis

Graminaceous cyst nematodes form a group of eleven valid species including Heterodera avenae, Heterodera filipjevi and Heterodera latipons and constitute major pests to cereals. They are widely spread in circum-mediterranean areas where they are presumed to cause yield losses on bread and durum wheat. The objective was to document the diversity of these cereal cyst nematodes, in particular samples from Mediterranean regions, in comparison to species which develop on cultivated or wild grasses (H. arenaria, H. hordecalis, H. mani) and on rice or sugarcane (H. sacchari). Studies involved PCR-RFLP of ITS and morphometrics of the juvenile and cyst characters. UPGMA analysis of molecular data showed that the isolates segregated in two main clusters which seem to represent different evolutionary lineages. The H. avenae sensu lato cluster (I) contained H. arenaria, H. avenae, H. filipjevi and H. mani. The second cluster (II) contained isolates of H. hordecalis and H. latipons. Within H. avenae sensu lato, H. filipjevi was separated from the other related species with significant bootstrap value. The differentiation of H. arenaria, recognized for the first time based on molecular data, and H. mani with few restriction enzymes were the least significant. Intraspecific polymorphism allowed differentiation of isolates originating from Australia within H. avenae sensu stricto. The group H. hordecalis–H. latipons showed the greatest genetic variability between and within isolates. Two representatives of Heterodera sacchari, taxonomically included in the schachtiigrave group, were genetically as distant to this group as to the other graminaceous species belonging to either H. avenae sensu lato or H. hordecalis–H. latipons group. Results inferred from multivariate analysis applied on morphometrics of the cysts and juveniles showed agreement between genetic and phenotypic classifications. This study demonstrates the utility of combined molecular and classical methods to enhance our knowledge about the diversity within the complex of graminaceous cyst nematodes and to establish robust techniques to identify a wider set of nematode species.     

昆虫病原线虫共生细菌共生性与病原性的研究进展

本文对昆虫病原线虫共生细菌共生性和病原性及其相关基因近年来的研究概况进行了阐述，探讨了可能的共生因子和昆虫毒性因子相关基因的表达和调控模式。