昆虫组蛋白修饰的研究进展

组蛋白修饰作为表观遗传修饰的一种主要形式,对基因表达和表型调控具有重要作用。组蛋白修饰的N端尾区可通过乙酰化、甲基化、磷酸化等修饰来改变染色质的状态以及调控基因的表达。与脊椎动物相比,昆虫种类繁多,且有变态发育、表型复杂等特征,可以成为探索动物社会行为、发育调控和毒理作用等表观遗传基础的模型。本文总结了昆虫组蛋白修饰的主要类型(乙酰化和甲基化修饰)及修饰酶的研究进展,对染色质免疫共沉淀测序技术(chromatin immunoprecipitation followed by sequencing,ChIP-seq)、染色质转座酶可及性测序技术(assay for transposase-accessible chromatin with high-throughput sequencing,ATAC-seq)、转录组测序技术(RNA-seq)、组蛋白修饰酶功能验证以及Western blot、免疫细胞化学(immunocytochemistry,ICC)、免疫组织化学(immunohistochemistry,IHC)、酶联免疫吸附测定(enzyme linked immunosor...     

Buried seeds in arable soils in Scotland

Soil from arable areas in Scotland was examined macroscopically for seeds. In terms of the percentage of sites at which they were recorded, Chenopodium album L. (33%), Poa annua L. (22%), Polygonum aviculare L. (41%), Polygonum persicaria L. (39%), Spergula arvensis L. (42%) and Stellaria media (L.) Vill. (44%) were the most common species found. They accounted for 78% of the seeds recovered. There were eighty different species found over the 5 years of the survey. Estimated total weed populations (m^?2) ranged from nil to 170000 with an average of 16000 m^?2 in the top 20 cm of soil.     

Variability in initial spray deposit in apple trees in space and time

Variation in pesticide residues in space and time has not been investigated systematically in spite of the large variability found at single scales (e.g. between trees or orchards). Information on variability at different scales will support the development of sampling methods and more reliable prediction of residues. Experiments were conducted to quantify the spatiotemporal variability in initial spray deposit on apple leaves and fruit using a substitute tracer (zinc EDTA chelate). Five hierarchical spatial scales were defined as (1) between orchards, (2) between plots within an orchard, (3) between trees within a plot, (4) between zones within a tree and (5) between leaves/fruit within a zone. Similarly, two temporal scales were defined as (1) between applications within a single year and (2) between years. The initial zinc concentration was approximately log-normally distributed; the variability in initial deposit concentration was greater on leaves than on fruit. The average initial zinc deposition was significantly greater in the top and outside zones than in the middle zones within individual trees. The most important scale for driving residue variability is the within-zone unit-to-unit variation, contributing to 71 and 49% of the observed variability for leaf and fruit samples respectively. Variability at other scales was related to the variation in the tree architecture. The results indicated that stratified sampling on the basis of within-tree zone structures, with the effort focused on within-zone sampling, should be used for the determination of pesticide residues.     

Occurrence of viruses in irrigated wheat in Zambia

Surveys were conducted during the cool-dry months of June–August 1997 and June–July 1998 for the presence of viruses in irrigated wheat in Central, Copperbelt, Lusaka and Southern Provinces of Zambia in 14 commercial farms and four wheat cultivar plots. Virus symptoms were observed on nine wheat cultivars ( Triticum aestivum 'Deka', 'Gamtoos', 'Lorie II', 'MM2', 'Nata', 'Nkwazi', 'P7', 'Scan' and 'Sceptre') of South African, Zambian and Zimbabwean origin. Several viruses were identified on the basis of field symptomatology, symptoms developing on mechanically inoculated indicator plant species or cultivars and serology (DAS-ELISA). The study revealed the occurrence of Brome mosaic virus (BMV), Barley stripe mosaic virus (BSMV), Barley yellow dwarf virus and its strains (BYDV-PAV and RPV), Soil-borne wheat mosaic virus (SBWMV), Wheat dwarf virus (WDV), Wheat streak mosaic virus (WSMV) and Wheat spindle streak mosaic virus (WSSMV). DSA-ELISA tests confirmed these identifications. The prevalence of viruses varied annually and from field to field. BSMV, BYDV-PAV, SBWMV, WDV, WSMV and WSSMV were found to be the most prevalent viruses. Viruses generally occurred in mixed infections of 3–6 viruses and the most common virus complex consisted of 4 viruses (50%), viz. BYDV, SBWMV, WDV and WSSMV. Five- and six-virus complexes were relatively less common (20% each) whereas 3-virus complex was noticed in only 10% cases. SBWMV and WSSMV have been found to be new to Africa and Zambia and are reportedly vectored by a fungal protist – Polymyxa graminis . BYDV strains MAV and SGV were also tested but gave negative results against their antisera.     

Progress in research on resistance in arthropods

This is a short review of the history of the extensive research on resistance in the post-DDT era, in relation to advancing experimental technique. The subject began as a serious concern to applied entomologists only, gradually involved other disciplines, notably genetics and biochemistry; and the inherent interest and challenge of the problem attracted the attention of experts in these fields. It will be convenient to divide the 25 years involved into three periods: the years up to 1952, the decade 1953-62 and the decade 1963-72. The various types of investigation can be categorised as: (1) detection and measurement, (2) genetic studies, (3) primary toxicology and (4) biochemical toxicology.     

Differences in resistance in onion cultivars to pink root rot disease in Iran

Forty-five onion (Allium cepa) cultivars were evaluated for disease resistance to the fungal pathogen Pyrenochaeta terrestris (pink root disease). Forty-three Iranian cultivars and two commercially exotic resistant cultivars (Texas Early Grano and Yellow Sweet Spanish) were grown in a glasshouse for two successive years (2003 and 2004) in Isfahan, Iran. Susceptibility of the cultivars was determined using a scale of 0–3. Six cultivars had significantly lower susceptibility of pink root compared to the exotic ones. High susceptibility tended to be associated with high mean scores (2–3), and the highly resistant cultivars had the lowest scores (0–1). In addition, the 45 examined cultivars were ranked from 1 to 45 according to their markedly differing reactions to P. terrestris, which differed markedly. Of 32 cultivars that were less resistant, 30 with an intermediate status or tolerance (1–2) differed considerably in their rank order. No pink root symptoms were seen in the early stages, but on blotter paper or wheat-straw agar some roots turned pink with no pycnidia formation, whereas on potato dextrose agar medium (PDA) with a few fresh healthy and sterile onion roots on the surface, mycelia and pycnidia were recovered. Variance and cluster analysis showed similar results among the cultivars with various levels of resistance, tolerance and susceptibility as determined by scoring scales.     

Phytopathological situation in potato in Belarus1

The control of potato diseases in Ukraine is reviewed. Control of potato blight (Phytophthora infestans) has only been adequate for limited periods in the past (when resistant cultivars were available and when the systemic fungicides were introduced). Currently, the disease is in a new epiphytotic phase and control has failed again, probably connected with the introduction of new mating types and the existence of greater variability. Blight now occurs earlier in the season and in most years (instead of only years when climatic conditions are favourable). Control has now to be essentially preventive, rather than based on forecasting. The importance and control of other potato diseases is also considered (Alternaria spp., Rhizoctonia solani, Geotrichum candidum, Phytophthora erythroseptica, Sclerotinia sclerotiorum, Streptomyces scabies).     

Observations on some nematodes parasitic in freshwater fishes in Laos

In 1989, samples of some freshwater fishes collected in Vientiane Province (R. Mekong basin) in Laos were examined for helminths. This material comprised 11 species of parasitic nematodes (7 adults and 4 larvae), including 3 species new to science: Camallanus (Camallanus) hampalae sp. n. from Hampala macrolepidota, Procamallanus (Punctocamallanus) punctatus sp. n. from Mystus rhegma and Mystus sp., and Rhabdochona (Globochona) equispiculata sp. n. from Hampala macrolepidota and H. dispar. Zeylanema Yeh, 1960 is considered a subgenus of the genus Camallanus, Dentocamallanus subgen. n. (type species C. (D.) sweeti (Moorthy, 1937)) is proposed for the species of Paracamallanus with teeth in the buccal capsule, and Punctocamallanus subgen. n. (type species P. (P.) punctatus sp. n.) for the species of Procamallanus with the buccal capsule ornamented with punctations. The name Rhabdochona wangi nom. nov. is proposed for R. bagarii Wang et Guo, 1983 (a homonym to R. bagarii Gupta et Srivastava, 1982) and Camallanus gomtii Gupta et Verma, 1978 is newly synonymized with Neocamallanus ophiocephali (Pearse, 1933). All the nematodes are recorded from Laos for the first time. The parasites are briefly described and illustrated and some problems concerning their taxonomy and geographical distribution are discussed.     

Evaluation of endosulfan residues in vegetables grown in greenhouses

The reduction in residue levels of endosulfan with time after treatment of tomatoes, green beans, peppers and cucumbers grown in different types of commercial greenhouses (flat- and asymmetric-roof greenhouses) in Almería (Spain) was investigated. A study of the major and minor degradation products of endosulfan in peppers and cucumbers (endosulfan-sulfate, -ether and -lactone) was carried out using gas chromatography-tandem mass spectrometry (GC-MS/MS). To establish the influence of environmental conditions on the degradation of endosulfan, several field trials have been carried out in which crops were sprayed at different rates (full, half- and quarter- of those rates recommended) during two seasons (spring and winter). For statistical purposes, the disappearance of endosulfan with time was considered to follow a pseudo-first-order reaction. Analysis of variance (ANOVA) has been applied to the results obtained. Half-lives of residue disappearance were 4.03-4.68 days in green beans, 4.03-4.20 days in tomatoes, 8.22 days in peppers and 7.97 days in cucumbers. Half-lives in spring were shorter than in the winter season. The application rate and the type of greenhouse did not influence the half-lives.     

Management of resistance in Bemisia in Arizona cotton

A whitefly (Bemisia argentifolii) resistance crisis climaxed in 1995 in Arizona cotton and prompted the development of an integrated resistance management strategy adapted from a program implemented in Israel in 1987. The strategy incorporated two new major elements: once-per-year use of the insect growth regulators (IGRs) pyriproxyfen and buprofezin, and measures to delay use of pyrethroids for as long into the growing season as possible. A three-stage chemical use recommendation was formulated comprising IGRs (Stage I), other non-pyrethroid insecticides (Stage II), and synergized pyrethroid insecticides (Stage III). Results from use of the strategy in the 1996 season were very promising. Insecticide use for control of whiteflies was reduced substantially. State-wide monitoring of whitefly susceptibility revealed significant reductions in resistance to synergized pyrethroids as well as increased susceptibility to amitraz. Susceptibility of Lygus bugs to key insecticides changed correspondingly with increases and decreases in whitefly resistance from 1994 through 1996. ©1997 SCI     

Detection and identification of phytoplasmas in yellows-diseased weeds in Italy

Yellows-diseased plants of Crepis setosa (hawksbeard), Knautia arvensis (field scabious), Convolvulus arvensis (field bindweed), Picris echioides (bristly oxtongue), Echium vulgare (blueweed) and Calendula officinalis (pot marigold) collected in central and southern Italy were examined for phytoplasma infection by means of polymerase chain reaction (PCR) technology using universal phytoplasma primers directed to ribosomal sequences. The detected phytoplasmas were characterized and differentiated using restriction fragment length polymorphism analysis of PCR-amplified DNA. The phytoplasma detected in diseased pot marigold plants was identified as a member of the aster yellows group and proved indistinguishable from a strain of the American aster yellows phytoplasma. The phytoplasma identified in diseased field bindweed plants is a putative new type of the stolbur group that differed from the typical stolbur phytoplasma. Phytoplasmas detected in diseased hawksbeard, blueweed and field scabious plants are all putative new members of the sugarcane white leaf group while the phytoplasma detected in diseased bristly oxtongue plants represents a new member of the faba bean phyllody group. For hawksbeard and field scabious this is the first report on the occurrence of phytoplasma diseases, whereas phytoplasmas infecting bristly oxtongue and blueweed have never been characterized before.     

Phenotype Instability in Botrytis cinerea in the Absence of Benzimidazole and Dicarboximide Fungicides

ABSTRACT Stability of phenotypes of isolates of Botrytis cinerea that were sensitive or resistant to benzimidazole and dicarboximide fungicides was examined in the absence of fungicides in laboratory and growth room experiments. Twelve greenhouse isolates of B. cinerea were subcultured on potato dextrose agar (PDA) for 20 generations and on geranium seedlings for 15 generations. Three isolates of each of the following four phenotypes were used: sensitive to the fungicides thiophanate-methy1 (a benzimidazole) and vinclozolin (a dicarboximide) (S(T)S(V)), resistant to both fungicides (R(T)R(V)), resistant to thiophanate-methy1 and sensitive to vinclozolin (R(T)S(V)), and sensitive to thiophanate-methy1 and resistant to vinclozolin (S(T)R(V)). In three trials on PDA, 36 populations were subcultured; 8 populations changed phenotypes by the end of 20 generations, as determined by conidium germination on fungicide-amended medium. Five of the eight initially were S(T)R(V); the resulting phenotypes were S(T)S(V), R(T)S(V), and R(T)R(V). Populations from eight other isolates exhibited temporary changes in phenotype during intermediate generations on PDA but reverted to initial phenotypes by the twentieth generation; five of these populations changed to phenotype R(T)R(V). In two geranium seedling trials, each of the 12 greenhouse isolates was inoculated onto a set of three seedlings for each generation, and diseased tissue that developed was used to initiate the next generation. Therefore, a total of 72 populations of B. cinerea were subcultured in the two trials; 5 of these populations changed phenotype at the end of 15 generations. Three of the five initially were S(T)R(V); these changed to phenotypes S(T)S(V) or R(T)R(V). In each of the two trials on geranium seedlings, a population subcultured from one S(T)S(V) isolate changed phenotype one to phenotype R(T)R(V) and one to phenotype R(T)S(V). In all trials, no population resistant to thiophanate-methy1 changed to a thiophanate-methy1-sensitive phenotype, and no population changed to phenotype S(T)R(V). Random amplified polymorphic DNA (RAPD) fingerprints were generated with the 12 initial isolates and 49 isolates subcultured on PDA or geranium seedlings. Cluster analyses of RAPD markers showed that subcultured isolates exhibiting the same phenotype clustered together and that subcultured isolates derived from a common greenhouse isolate but with different phenotypes were in different clusters. Some populations that did not change phenotype exhibited considerable differences in RAPD marker patterns. The results of this study indicate that, in the absence of fungicides, sensitive populations of B. cinerea can develop resistance to thiophanate-methy1 and vinclozolin, and this resistance can be maintained in populations through multiple generations. Populations resistant only to vinclozolin (S(T)R(V)) exhibited a high frequency of phenotype change, and populations resistant to both fungicides (R(T)R(V)) were stable.     

内蒙古温带草地植被的碳储量

草地生态系统在全球碳循环中起着极为重要的作用。大部分草地碳储存在地下,但是实测数据十分匮乏,因此准确估算温带草地植被碳储量对评价草地生态系统碳循环具有重要意义。作为一个区域性资料积累工作,作者对内蒙古温带草地的碳储量进行了大范围的实测研究,以估算该地区草地植被的碳储量。主要结果如下:(1)内蒙古温带草地总面积为58.46×106hm2,总植被碳储量为226.0±13.27Tg C(1 Tg=1012g),平均碳密度为3.44Mg C.hm-2;(2)地下根系储存的碳是地上碳储量的6倍左右,地上、地下生物量碳储量分别为33.22±1.75和193.88±12.6 Tg C,平均碳密度分别是0.51和2.96 MgC.hm-2;(3)不同草地类型的碳储量差异较大,典型草原最大(113.25 Tg C),占草地总碳储量的50%,其次是草甸和草甸草原,荒漠草原碳储量最低(15.37 Tg C)。     

Yield loss in chickpeas in relation to development of fusarium wilt epidemics

ABSTRACT Development of 108 epidemics of Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris were studied on cvs. P-2245 and PV-61 in field microplots artificially infested with races 0 and 5 of F. oxysporum f. sp. ciceris in 1986 to 1989. Disease progression data were fitted to the Richards model using nonlinear regression. The shape parameter was influenced primarily by date of sowing and, to a lesser extent, by chick-pea cultivars and races of F. oxysporum f. sp. ciceris. Fusarium wilt reduced chickpea yield by decreasing both seed yield and seed weight. These effects were related to sowing date, chickpea cultivar, and virulence of the prevalent F. oxysporum f. sp. ciceris race. Regression models were developed to relate chickpea yield to Fusarium wilt disease intensity with the following independent variables: time to initial symptoms (t(is)), time to inflection point (t(ip)) of the disease intensity index (DII) progress curve, final DII (DII(final)), standardized area under DII progress curve (SAUDPC), and the Richards weighted mean absolute rate of disease progression (rho). Irrespective of the chickpea cultivar x pathogen race combination, the absolute and relative seed yields decreased primarily by delayed sowing. The relative seed yield increased with the delay in t(is) and t(ip) and decreased with increasing DII(final), SAUDPC, and rho. A response surface as developed in which seed yield loss decreased in a linear relationship with the delay in t(is) and increased exponentially with the increase of rho.     

Genetic characterisation of Giardia duodenalis in dairy cattle in Brazil

The intestinal protozoan parasite Giardia duodenalis (Lambl, 1859) Kofoid & Christiansen, 1915 [syn. Giardia intestinalis and Giardia lamblia] has emerged as a widespread enteric pathogen in humans and domestic animals. In recent years, G. duodenalis has been found in cattle worldwide and longitudinal studies have reported cumulative prevalence of 100% in some herds. In the present study, we determined the prevalence and genetic characterisation of G. duodenalis in 200 dairy cattle from 10 dairy farms in S?o Paulo state, Brazil. All faecal specimens were screened for the presence of G. duodenalis using microscopy examination, enzyme immunoassay (EIA) and polymerase chain reaction (PCR). DNA was extracted from faecal samples and G. duodenalis were identified by amplification of the small subunit ribosomal (SSU-rDNA) and glutamate dehydrogenase (GDH) genes followed by restriction fragment length polymorphism (RFLP) or sequencing analysis. Giardia was identified in eight farm locations (80% prevalence). Overall, 15/200 (7.5%) animals were positive for infection, only one of which was a cow. Giardia duodenalis genotype E was present in 14 of the animals tested. Zoonotic genotype AI was present in one positive sample. Genotype E and genotype A represented 93% and 7% of G. duodenalis infections, respectively. This study demonstrates that G. duodenalis infection was prevalent in dairy calves in S?o Paulo state and that the non-zoonotic genotype E predominates in cattle in this region. Nevertheless, calves naturally infected in Brazil can shed Giardia cysts that can potentially infect humans, and thus, they may represent a public health risk.     

Flowering events in relation to smut susceptibility in pearl millet

In field experiments at ICRISAT, selected lines of pearl millet (Pennisetum glaucum) resistant and susceptible to smut (Tolyposporium penicillariae) were evaluated for the timing of flowering events. In smut-resistant lines, the time from the boot-leaf stage (inoculation) to stigma emergence varied in the range 46–120 h, from boot to anther emergence 105–190 h, and from stigma emergence to anther emergence (protogyny period) 59–131 h; in smut-susceptible lines, the corresponding periods were 62–140 h, 146–200 h and 44–120 h, respectively. There were no significant correlations between timing of events and smut severity. Three cytoplasmically male-sterile lines showed longer protogyny periods and higher smut severity than their corresponding maintainer lines. Four lines having short protogyny periods (22–52 h) and resistance to ergot (Claviceps fusiformis) also showed high resistance to smut. Resistance to smut in most ergot-susceptible lines was independent of the timing of flow ering events, but in ergot-resistant lines it could be closely related to flowering events.     

江汉平原麦田杂草调查

运用倒置“Ｗ”９点取样法对江汉平原麦棉套作农田杂草调查,结果表明该地区麦田杂草有１４科２３种,其中禾本科杂草占２７％,阔叶杂草占６９％,莎草科占４％。相对多度达１０以上的麦田杂草依次有猪殃殃、婆婆纳、野燕麦、半夏、通泉草、狗牙根、卷耳等７种,其中猪殃殃、婆婆纳两种双子叶杂草的相对多度达５０和４０,为当地麦田优势种群。     

蒸散发观测研究进展及绿洲蒸散研究展望

蒸散发是绿洲水文循环中最重要的水文过程和生态过程之一,开展绿洲蒸散发研究是提高水资源利用的基础.从叶面、个体、田间到景观尺度,系统综述了国内外蒸散发观测研究的最新进展,结合荒漠绿洲的特点及研究现状,指出应加强:①涡度相关技术在异质性强的绿洲的应用技术研究;②如何分割蒸散发中植物蒸腾和土壤蒸发,以及时空动态、驱动机制和调...     

Rice Diseases in Nigeria

Abstract

The two major fungal diseases of rice in Nigeria are rice blast (Pyricularia oryzae Cav.) and brown spot (Cochliobolus miyabeanus (Ito and Kuribayashi) Dreschler ex Dastur). The loss in grain yield attributable to these diseases ranges from 11.5–39.6% and 12–43% respectively, Mancozeb, blasticidin-S, fentin hydroxide, benomyl and edifenphos as foliar sprays effectively control rice blast in the laboratory and field. Brown spot is controlled by spraying with thiram, mancozeb or blasticidin-S. A more useful approach to the control of these diseases being adopted in Nigeria is the search for horizontally resistant varieties. Other fungal diseases of rice in Nigeria are the green smut (Ustilaginoidea virens (Cooke) Tak.), basal sheath rot (Rhizoctonia solani Kühn), sheath blight (Corticium sasakii (Shirai), Matsumoto.), leaf scald (Rhynchosporium oryzae Hashioka and Yokogi), narrow brown leaf spot (Cercospora oryzae Miyake) and bakanae disease, a foot rot caused by Fusarium moniliforme Sheldon. Two suspected cases of virus diseases have been reported; grassy stunt disease (transmitted by Nilaparvata lugens Stal.), and orange leaf disease (transmitted by Inazuma dorsalis (Motschulsky). No bacterial disease of rice has been found in Nigeria.