Metabolism of methylated analogs of aldrin and dieldrin by liver preparations from male and female rat

Analogs of aldrin and dieldrin have been synthesized, the molecules of which lack a methylene bridge but have two methyl groups attached to olefinic or oxirane ring carbon atoms. Their metabolism was studied using NADPH-supplemented 12,000g × 30-min supernate of livers from Wistar and CD strains of rats. The dimethylated olefin was not metabolized to its epoxide but was converted by supernate of liver from rats of both sexes to a labile hydroxylated metabolite. Exogenous NADPH increased the rate at which the olefin was metabolized, but concentrations of NADPH which increased the yield of the labile metabolite when added to female rat liver preparations decreased the yield when added to those from the male. This metabolite had a mass spectrum which was consistent with it being a hydroxymethyl derivative. The dimethylated epoxide was metabolized more slowly than the olefin, and a notable sex difference in the route of metabolism was evident. With supernate from livers of female rats the only metabolite detected by gas-liquid chromatography had a mass spectrum consistent with it being a ring-hydroxylated epoxide. Male rat liver supernate formed small quantities of the same compound, but the major metabolite had a mass spectrum indicative of a hydroxymethyl epoxide. No hydrolysis of the oxirane ring of the epoxide has been detected. The relevance of these results to the planned synthesis of cyclodienes of optimal biodegradability is mentioned.     

豌豆根腐病研究进展

根腐病是豌豆根部的重要病害之一,在世界各地豌豆产区均有发生,是制约豌豆产业持续健康发展的因素之一。世界上尚未发现对根腐病完全免疫的豌豆品种,防治方法主要以农业防治和化学防治为主。本文从豌豆根腐病的发生与分布、病原菌的分类及特点、抗性鉴定及评价标准、种质资源、分子标记及防治策略等方面对国内外豌豆根腐病研究现状进行综述。并提出抗病育种和未来豌豆根腐病综合防治的研究方向。     

The occurrence in Denmark of black root rot of pea caused by Thielaviopsis basicola

Thielaviopsis basicola has been shown to be a root pathogen of pea of considerable importance in Denmark. The fungus is only found in fields with one or more previous pea crops in the field history. In the dry and warm growing season of 1989 the fungus was found in 0·6% and 3·2% of the fields in two separate areas in Denmark. In the fields where T. basicola was detected the average disease severity index in plant samples was 51·8, whereas the average disease severity index in plant samples without the fungus was 27·0. The average yield of green peas was reduced from 5167 to 4171 kg/ha when T. basicola was present. For detection and isolation of T. basicola it is important to use a technique combining microscopic examination, a semi-selective medium and a dilution plate method.     

Bioassay to assess root rot in pea and effect of root rot on yield

Infection of pea roots by soil-borne pathogens causes foot and root rot. In 1985 research was started to develop a method to predict the root rot likely to occur in prospective pea fields. In a bioassay the pea cultivar Finale was sown in a composite soil sample from each field in pots under standardized conditions in the greenhouse. The plants were removed at the green bud stage and the severity of root rot recorded. Between 1985 and 1988 approximately 200 field pea crops were monitored for root rot development. Forty-eight fields were bioassayed in 1986, 51 in 1987 and 30 in 1988. Each year, root rot readings in the bioassay and disease severity readings at field sampled plants at flowering and green pod were linearly correlated (P<0.001). As the degree of root rot in the field crop increased, there was a proportional lower yield. In heavily infested fields, up to a 50% yield reduction occurred.The bioassay in pots proved to be a reliable method for predicting root rot severity in sampled pea fields.     

Application of formulated rhizobacteria against root rot of field pea

Formulations of bacterial biocontrol agents were evaluated for the control of pea root-rot caused primarily by Pythium ultimum and Rhizoctonia solani, at different levels of disease severity in field trials. Pseudomonas fluorescens (strain PRA25) in a peat-based formulation increased yield by 17% over the untreated, in a trial with light disease infection, and by 120% in another with moderate infection. Other bacteria including P . cepacia (strain AMMD) and fluorescent pseudomonads increased seedling emergence, and decreased disease incidence and severity, but with variable effects on yield when disease level was light to moderate. Biocontrol agents resulted in only limited control when disease was severe. Control with Captan did not differ significantly from that obtained with bacterial biocontrol agents. The application of Rhizobium granular inoculum together with PRA25 granules did not differ from other treatments in disease control, indicating that Rhizobium is compatible with biocontrol agents. The population dynamics of a fluorescent pseudomonad introduced into the rhizosphere in peat or granular formulation was monitored using an antibiotic-resistant mutant marker strain. The bacterium in peat formulation established a considerably higher population than that in granular formulation in 1993 trials, and a slightly higher population in 1994 trials. The higher population may have been responsible for the efficiency of root colonization and the effectiveness of disease control.     

干旱胁迫对豌豆根系形态及产量的影响

采用盆栽方法,研究了55%的土壤相对含水量在分枝期、孕蕾期、花荚期进行15 d历时的干旱胁迫对豌豆干物质累积、根系生长及产量的影响。结果表明,与全生育期正常供水(75%)相比,三种干旱胁迫处理均降低了豌豆的干物质累积量,胁迫时期越早,复水对豌豆地上部干物质累积的补偿效果越好,分枝期干旱胁迫在成熟期达到了等量补偿;干旱胁迫均显著抑制了根系的生长,分枝期干旱胁迫对根系生长的抑制具有滞后效应,胁迫结束时与对照间差异不显著,在花荚盛期显著低于对照,孕蕾期干旱胁迫根系的复水补偿生长作用较好,各根系形态指标在成熟期均达到了超越补偿;三种胁迫方式均抑制了根瘤的形成及其生长,且复水后均产生了不足补偿,胁迫时期越早,补偿效果越差;花荚初期干旱胁迫对豌豆产量的抑制作用最大,比对照低20.41%,其次为孕蕾期,比对照低6.63%,分枝期干旱胁迫不影响子粒产量。     

Genetic diversity of the pea root pathogen Aphanomyces euteiches in Europe

The oomycete pathogen Aphanomyces euteiches causes root rot in various legume species. In this study we focused on A. euteiches causing root rot in pea (Pisum sativum), thereby being responsible for severe yield losses in pea production. We aimed to understand the genetic diversity of A. euteiches in Europe, covering a north-to-south gradient spanning from Sweden, Norway and Finland to the UK, France and Italy. A collection of 85 European A. euteiches strains was obtained, all isolated from infected pea roots from commercial vining pea cultivation fields. The strains were genotyped using 22 simple-sequence repeat markers. Multilocus genotypes were compiled and the genetic diversity between individual strains and population structure between countries was analysed. The population comprising strains from Italy was genetically different and did not share ancestry with any other population. Also, strains originating from Finland and the eastern parts of Sweden were found to be significantly different from the other populations, while strains from the rest of Europe were more closely related. A subset of 10 A. euteiches strains from four countries was further phenotyped on two susceptible pea genotypes, as well as on one genotype with partial resistance towards A. euteiches. All strains were pathogenic on all pea genotypes, but with varying levels of disease severity. No correlation between the genetic relatedness of strains and virulence levels was found. In summary, our study identified three genetically distinct groups of A. euteiches in Europe along a north-to-south gradient, indicating local pathogen differentiation.     

载银无机抗菌制剂对大豆根腐病的防治效果

 测定了广泛用于工业和日用品的载银无机抗菌制剂Zeomic和AM₁对大豆根腐病重要病原菌Fusarium oxysporum、Fusarium solani和Rhizoctonia solani孢子萌发和菌落扩展的抑制作用。结果表明,Zeomic在浓度为500 mg/L时可以完全抑制F. oxysporum和F. solani的孢子萌发,但对F. oxysporum、F. solani和R. solani菌落扩展的抑制作用较弱,分别为7.4%、0.0%和3.7%。AM₁对病菌孢子萌发的抑制作用随浓度的升高而增强,在浓度为250 mg/L时对F. solani孢子萌发的抑制率为18.8%,到1 000 mg/L时可完全抑制。但AM₁在浓度为1 000 mg/L时对F. oxysporum的孢子萌发抑制率只有29.7%,表明不同菌类对AM₁的敏感性不同。同一浓度下的AM₁对F. oxysporum菌落扩展的抑制率大于对F. solani和R. solani菌落扩展的抑制作用,在500 mg/L时对病菌的抑制率分别为51.4%、14.6%和11.0%。温室内对大豆生长的调查结果表明,用种子重量0.05%和0.10%的AM₁拌种对出苗和生长有促进作用,Zeomic用量在0.05%时不影响出苗、株高和根系干物质积累,但当用量增加至0.10%时,则表现对出苗和干物质累积的抑制作用。田间试验结果表明,500m g/L的AM₁拌种对大豆根腐病防效为32.6%,与化学农药35%多克福包衣处理无显著差异,但比后者增产10.1%。由此说明,载银无机抗菌制剂具有用于农作物病害防治的潜力。     

Genetic variation in Fusarium avenaceum causing root rot on field pea

Isolates of Fusarium spp. were recovered from the roots of field pea (Pisum sativum) collected from 15 commercial fields in Alberta, Canada. Most of the isolates (75 out of 96) were identified as F. avenaceum, based on morphology, phylogeny and species‐specific PCR amplification. Molecular differences in the F. avenaceum isolates were detected based on putative mating type, and on ITS and CPN60 sequences. MAT‐1 and MAT‐2 were equally distributed among the isolates. Phylogenetic analysis based on ITS and CPN60 sequences clustered most of the F. avenaceum isolates into a single group. In some cases, isolates with low aggressiveness clustered together in additional groups. There was no correlation between phylogenetic profile and either mating type or geographic origin. This population of F. avenaceum has a low level of genetic variation and consists of isolates derived from the two mating types. Isolates with low aggressiveness are also retained in the population.     

Soil receptivity toFusarium solani f. sp.pisi and biological control of root rot of pea

Potential antagonists ofFusarium solani f. sp.pisi (Fsp) were selected from soil samples with varying degrees of receptivity to this pathogen. They were tested against Fsp isolate 48 (Fs48), in increasingly complex systems. Most species testedin vitro were able to antagonize Fs48. No relation could be establishedin vitro between the receptivity of the soil from which an isolate originated and its antagonism to Fs48. In soils naturally infested with pea root rot pathogens, which were stored humid at 4°C for a period longer than a year, various isolates ofFusarium, Gliocladium andPenicillium spp. were able to reduce root rot. After sterilization of these soils, onlyGliocladium roseum isolates, added at 10⁵ conidia g^–1 dry soil, significantly reduced disease severity and prevented root weight losses caused by Fs48 at 10⁴ conidia g^–1 dry soil. In soils in which the biota were activated by growing peas before the assays, doses of 10⁶ and 10⁷ ofG. roseum were required to reduce root rot. In these soils, the antagonistic effects of fluorescent pseudomonad strains from soil of low receptivity to Fsp were variable. Some strains of fluorescent pseudomonads, from soil moderately receptive to Fsp and from highly infested soils, were also able to reduce root rot. Disease suppression by pseudomonad strains was more evident in the absence than in the presence ofAphanomyces euteiches in the root rot pathogen complex. The role of receptiveness of the soil with regard to potential antagonists is discussed.     

The epoxidation of aldrin by microsomes from the Fc strain of housefly: A genetic survey

The DDT-resistant housefly strain, Fe, known to resist DDT by biochemical oxidation, is also resistant to carbamate insecticides and has a high in vitro microsomal epoxidase activity. The purpose of this investigation was to determine whether the DDT resistance, associated with chromosome V, is also responsible for the resistance to carbamates and for the high epoxidase levels. Genetic procedures for segregating the R factors were employed using a multimarker insecticide susceptible strain designated acbco. The technique involved backcrossing the F₁ hybrid of the resistant and susceptible parents to the susceptible parent. The genotypes with a single R chromosome from the Fc parent were retained for further development as substrains and for toxicological and biochemical studies.These studies revealed that both resistance to the carbamate insecticide, propoxur, and the high in vitro microsomal epoxidation of aldrin were lost during the genetic isolation of the R factors. However, the resistance to DDT, associated with chromosome V, was present in the substrain carrying this chromosome from the Fc parent. All of the substrains were induced five- to seven-fold, by feeding phenobarbital at 1% in the diet for 3 days.Additional substrains synthesized from the substrains carrying chromosomes II and V or III and V from the Fc parent did not possess sufficient propoxur resistance or aldrin epoxidase activity to account for that present in the R parent.The interpretation of these rseults is that neither the carbamate resistance nor the microsomal epoxidase of the Fc strain is due to the factor which oxidizes DDT. Furthermore, the factor responsible for the high microsomal epoxidase activity is not due to a single chromosome such as chromosome II which is the case in other housefly strains with high oxidase activities.     

Tyrosinase as an inhibitor of aldrin epoxidase in house fly microsomes

The alleged inhibition by the house fly tyrosinase system of microsomal aldrin epoxidase and its reversal by KCN, which has been reported by another laboratory, was investigated. It was found that, except in newly emerged adults or in late instar larvae, no such effect was evident. Although a full explanation of the reported low epoxidase activity was not possible, some contributing practices were identified. One of these was the use of highly concentrated homogenates in the preparation of house fly microsomes, resulting in low recoveries of enzyme activity. The stimulatory effect of KCN, added during homogenization, is attributed, at least in part, to its negative effect on the determination of microsomal protein, thus resulting in a positive error when epoxidase activity is based on microsomal protein. Tyrosinase is a potent inhibitor of aldrin epoxidase in the microsomes prepared from late instar house fly larvae and its effect can be greatly reduced by the use of KCN. Bovine serum albumin, added during homogenization of house fly larvae, also enhances the epoxidase. Together, KCN and BSA, can increase epoxidase activity sevenfold in such larvae.     

Identification,pathogenicity and community dynamics of fungi and oomycetes associated with pea root rot in northern France

The pea root rot complex is a major concern for green pea production worldwide. This study aimed at characterizing its composition and dynamics throughout a cropping season in northern France. To this end, fungi and oomycetes were isolated from green pea plant roots with symptoms sampled at the flowering stage in 22 fields in 2017, and at the pea emergence, elongation and flowering stages in two fields in 2018. Out of 646 isolates collected, 317 were identified using molecular markers. Fusarium oxysporum, F. solani and F. redolens were highly predominant. Pathogenicity tests separated the isolates into four aggressiveness groups. F. solani isolates were the most aggressive. Phylogenetic analysis of their TEF1 sequences showed that they mainly belonged to the F. pisi lineage, and that F. oxysporum isolates were genetically close to isolates from the UK that did not belong to the forma specialis pisi. In addition, several Clonostachys rhizophaga isolates are reported for the first time to cause pea root rot. The oomycetes were rarely found and were represented by a few Pythium spp. isolates. Lastly, this study shows that the fungal and oomycete communities associated with pea root rot change during the cropping season. The level of dissimilarity of the root-rot-associated communities decreased throughout the cropping season towards a more similar composition at the flowering stage, dominated by F. solani, F. oxysporum and F. redolens. The proportion of nonpathogenic to weakly pathogenic isolates decreased progressively during the growing season in favour of moderately to highly pathogenic isolates.     

卵圆根瘤象危害箭舌豌豆

卵圆根瘤象(Sitona ovipennis Hochhuth)是豆科作物上的一种重要害虫, 在青海省分布广泛.一般年份该虫危害较轻, 但2003年在西宁市湟中县西堡乡发现其危害箭舌豌豆, 危害率90%以上, 尤其是前茬为蚕豆等豆科作物的被害更为严重, 给农民造成严重的损失.     

Degradation of maackiain by a cell-free extract from Sclerotinia trifoliorum

Preliminary results are presented on a cell-free system extracted from mycelium of Sclerotinia trifoliorum , which caused the disappearance of maackiain from solution. Activity depended on prior exposure of the mycelium to maackiain and on the inclusion of a protease inhibitor in the extraction buffer. No activity was found in culture filtrates.     

Effect of the polygalacturonase inhibitor from pea on the hydrolysis of pea cell walls by the endopolygalacturonase from Ascochyta pisi

Exo–polygalacturonase (exo–PG) and endo–PG from Ascochyta pisi rapidly adsorbed to insoluble fragments of cell walls from pea leaflets as did the endo–PG inhibitor that was isolated from these organs. The wall fragments were hydrolysed by the exo– and endo–PG but the rates were, respectively, only 1–8 and 8% of the rate of hydrolysis of soluble polygalacturonic acid (PGA). Although the endo–PG inhibitor rapidly and completely inhibited the hydrolysis of soluble PGA by the endo–PG it had no effect on the rate of hydrolysis of pea cell wall fragments by this enzyme. Extracts of the intercellular fluid from pea leaflets contained only 4% of the inhibitor present in that organ and the remainder was presumably intracellular. These findings indicate that the endo–PG inhibitor may be less effective in vivo than was previously suspected.     

Reduced consumption of pea protein-treated flour disks by stored-product insects

Consumption of pea (Pisum sativum L.) protein-treated wheat flour by the red flour beetleTribolium castaneum (Herbst.), the rice weevilSitophilus oryzae (L.) and the lesser grain borerRhyzopertha dominica (F.), was significantly reduced compared with wheat flour alone. Consumption was affected when the insects were exposed for 3 days to flour disks containing protein-rich fraction of the ‘Bonneville’ pea variety. Antifeedants present in the pea protein fraction are apparently responsible for the reduced feeding response in these species. http://www.phytoparasitica.org posting May 6, 2004.