Light and Scanning Electron Microscopy of Greenbug Aphid Damage in Wheat Using the Same Section

A method has been developed to enable correlative light microscopy (LM) and scanning electron microscopy (SEM) on the same section of wheat (Triticum aestivum L.) leaves infested by greenbug aphids (Schizaphis gra-minum Rondani). Segments of infested leaf tissue were fixed, embedded in paraffin, sectioned, and affixed to slides by standard histological techniques. Serial sections were viewed by LM as temporary mounts in xylene. Sections of interest were identified and re-embedded in fingernail polish, affixed to aluminum stubs, freed of polish with ethyl acetate or acetone, and sputter-coated for SEM. SEM of re-embedded leaf sections showed excellent preservation of leaf anatomy. The same aphid tracks and regions of cell damage identified by LM were visible. SEM increased resolution and provided a much clearer sense of the three-dimensional relations involved in the interaction between plant and insect.     

Light and Scanning Electron Microscopy of Greenbug Aphid Damage in Wheat Using the Same Section

A method has been developed to enable correlative light microscopy (LM) and scanning electron microscopy (SEM) on the same section of wheat (Triticum aestivum L.) leaves infested by greenbug aphids (Schizaphis gra-minum Rondani). Segments of infested leaf tissue were fixed, embedded in paraffin, sectioned, and affixed to slides by standard histological techniques. Serial sections were viewed by LM as temporary mounts in xylene. Sections of interest were identified and re-embedded in fingernail polish, affixed to aluminum stubs, freed of polish with ethyl acetate or acetone, and sputter-coated for SEM. SEM of re-embedded leaf sections showed excellent preservation of leaf anatomy. The same aphid tracks and regions of cell damage identified by LM were visible. SEM increased resolution and provided a much clearer sense of the three-dimensional relations involved in the interaction between plant and insect.     

浅论城市害蜂的危害与治理

蜂害是我国城市化发展过程中出现的新问题。该文综述了国内外螫人害蜂的种类、习性与危害 ,蜂毒的成分与毒理 ,被蜂螫伤者的救治及蜂害的治理方法 ,分析了目前我国所面临的城市蜂害问题 ,并提出了应采取的相应对策     

In vitro regeneration of cereals based on multiple shoot induction from mature embryos in response to thidiazuron

The in vitro competency of mature cereal embryos (winter, spring and durum wheats, oat, barley and triticale) was assessed for direct multiple shoot production on culture media containing the plant growth regulators, thidiazuron (TDZ) and/or 6–benzylaminopurine (BAP). Mature embryos of CDC Dancer oat showed the best response, with 69 shoots per explant on culture medium containing a combination of 4.5 μM TDZ and 4.4 μM BAP. TDZ alone induced about 16 shoots per explant from the oat. Among the wheat genotypes, durum wheat showed the most number of shoots (35) per explant on culture medium containing 4.5 μM of TDZ and 4.4 μM of BAP. With TDZ alone, shoot regeneration for durum wheat ranged from 27–32 shoots per explant. The regeneration frequency from the three winter wheat genotypes ranged from 11–25 shoots per explant and was highest on culture medium containing 9.1 μM TDZ and 4.4 μM BAP. The latter culture medium was also effective for a triticale genotype, inducing 34 shoots per explant. The regeneration from mature embryos of barley genotypes ranged from 5–9 shoots per explant. The mature embryos of all the cereals tested could be used for in vitro regeneration with TDZ and TDZ+BAP combinations.     

Auxin and sugar effects on callus induction and plant regeneration frequencies from mature embryos of wheat (Triticum aestivum L.)

Summary Genetic engineering of cereals currently depends on the use of tissue culture and plant regeneration systems. In wheat (Triticum aestivum L.), immature embryos are the most widely used explant to initiate cultures, but they are inconvenient due to their temporal availability and production requirements. Mature embryos are easily stored and are readily available as mature seeds. However, plant regeneration frequencies from cultures derived from mature embryos are generally low. This research was undertaken to improve callus induction and plant regeneration from wheat mature embryos of cultivar ‘Bobwhite’. The effects of four auxins [2,4-dichlorophenoxyacetic acid (2,4-D): 3,6-dichloro-o-anisic acid (dicamba); 4-amino-3,5,6-trichloropicolinic acid (picloram): and 2-(2-methyl-4-chlorophenoxy) propionic acid (2-MCPP)], and the effect of maltose vs. sucrose under filter sterilized and autoclaved conditions were evaluated. All auxin treatments resulted in callus induction except 2 MCPP. A highly significant effect of auxin type on both callus and plantlet production was detected, though interactions were observed. The effect of sugar type was dependent on the type of auxin used. Substitution of sucrose by maltose enhanced the regenration ability of callus from embryos cultured on media containing 2,4-D and picloram, but caused an opposite effect on media containing dicamba. Picloram significantly enhanced callus growth, however, embryogenic response and plant regenerability were low. Relative to 2.4-D, dicamba (18μM) resulted in a twofold increase in the number of plants regenerated per embryo and reduced the amount of time required for plant regeneration by 3–4 wk. Mention of a trademark or proprietary product does not constitute a guarantce or warranty by the University of Wisconsin and does not imply its approval to the exclusion of other products that may be suitable.     

Feeding impact of the planthopper Taosa longula (Hemiptera: Dictyopharidae) on water hyacinth,Eichhornia crassipes (Pontederiaceae)

Taosa longula Remes Lenicov (Hemiptera: Dictyopharidae), a planthopper native to South America, is a candidate for the biological control of water hyacinth, Eichhornia crassipes (Mart.) Solms-Laubach (Pontederiaceae), a serious weed worldwide. Biological control requires agents that are not only specific but also effective. Damage caused by sap-sucking insects is difficult to assess. In this work we designed an experimental and analytical procedure to evaluate the potential damage of T. longula on water hyacinth. The damage that T. longula causes to the clonal reproduction, biomass production, and growth of water hyacinth was studied through a paired greenhouse trial with floating cages. The performance of the plant, starting from two plants per treatment, was evaluated at different insect densities (5, 10, 15 and 20 nymphs per cage) until all the nymphs moulted to adults. The tests showed that individual growth and biomass production of water hyacinth was reduced due to the effect of the insect feeding above five nymphs per cage. The number of new plants produced by clonal reproduction was only significantly different above 15 nymphs per cage. These results suggest that this planthopper could be an effective agent for the biological control of water hyacinth.     

Incidence and severity of pest and disease damage to white clover foliage at 16 sites in England and Wales

From 1985 to 1987, leaves of white clover ( Trifolium repens ) cv. Grasslands Huia were examined for damage by pests and fungal diseases on seven occasions at up to 16 sites in England and Wales. Pest damage was recorded at all sites on all sampling dates. Over all sampling dates, the mean number of leaves damaged by slugs ranged from 23% to 67%, and that by weevils ( Sitona spp.) ranged from 3% to 62%. Also, up to 30% of leaves were damaged by other, unidentified pests. At individual sites, total pest damage frequently exceeded 90% of leaves. The area of leaf damaged by pests ranged from 2 - 12%. Fungal diseases were recorded in July and September but not in May, and were more prevalent in September 1985 than in September 1986 or 1987. Black blotch ( Cymadothea trifolii ) was the most frequently recorded disease, and the mean number of leaves damaged ranged from 4% to 21%. The mean area of leaves covered by lesions was 1–2%. Infections by viruses were assessed on two occasions, using indicator plants and electron microscopy, and only a very low incidence of arabis mosaic virus and red clover necrotic mosaic virus was recorded.     

A plate assay for simultaneous screening of polysaccharide- and protein-degrading micro-organisms

AIMS: To develop a plate assay for simultaneous screening of polysaccharide-degrading and protein-degrading micro-organisms. METHODS AND RESULTS: A plate assay, based on the visible solubilization of small substrate particles and the formation of haloes on Petri dishes, containing a mixture of diversely coloured insoluble polysaccharides and dye-labelled collagen as chromogenic substrates, was developed. This method was successfully applied for isolating the diverse polysaccharide- and/or protein-degrading bacteria from soil and sludge samples. Selected strains were identified using 16S rDNA partial sequencing; most of them belong to the genera Bacillus, Cellulomonas and Cellulosimicrobium. CONCLUSIONS: This novel approach provides unique and valuable information for direct primary screening when the target of selection is micro-organisms exhibiting protein-degrading activity, polysaccharide-degrading activity or a specific combination of them. SIGNIFICANCE AND IMPACT OF THE STUDY: This plate assay is convenient and easy to perform, rapid, and more adaptable for screening of a large number of samples, compared with other existing methods in the literature.     

A major QTL for resistance to soil-borne cereal mosaic virus derived from an old Italian durum wheat cultivar

Abstract

The genetic basis of resistance to soil-borne cereal mosaic virus (SBCMV) in the Triticum turgidum L. var. durum cv. Neodur was analyzed in this study, using a linkage mapping approach. We performed phenotypic and molecular analyses of 146 recombinant inbred lines derived from the cross Cirillo (highly susceptible)×Neodur (highly resistant). A major quantitative trait locus (QTL) that explained up to 87% of the observed variability for symptom severity was identified on the short arm of chromosome 2B, within the 40-cM interval between the markers Xwmc764 and Xgwm1128, with wPt-2106 as the peak marker. Three minor QTLs were found on chromosomes 3B and 7B. Two markers coding for resistance proteins co-segregate with the major QTL on chromosome 2B and the minor QTL on chromosome 3B, representing potential candidate genes for the two resistance loci. Microsatellite markers flanking the major QTL were evaluated on a set of 25 durum wheat genotypes that were previously characterized for SBCMV resistance. The allelic composition of the genotypes at these loci, together with pedigree data, suggests that the old Italian cultivar Cappelli provided the SBCMV-resistance determinants to durum cultivars that have been independently bred in different countries over the last century.     

基于MODIS植被指数评估洞庭湖区东方田鼠大暴发的危害

鼠害大暴发年份对受害植被分布和受害等级的快速评价,对于鼠害防治和恢复农业生产具有重要意义。研究以洞庭湖北洲子区域东方田鼠(Microtus fortis)为例,提出通过分析植被指数变动规律以确定评价时间的方法,通过植被指数对鼠害的敏感性分析,选择增强型植被指数(Enhanced vegetation index,EVI)为适宜植被指数,0.07为具有代表性的灾害阈值。运用植被指数差值法获得研究区作物危害分布图与危害等级分布图,表明东方田鼠危害区具有聚集和离大堤一定距离的特点。比较洞庭湖区实地踏查获得的东方田鼠危害图与灾害阈值确定的危害像元分布图,表明基于MODIS(Moderate-resolution imagine spectroradiometer)植被指数的鼠类暴发年份评估方法准确可行。     

A technique for assessing damage to roots of white clover caused by root feeding insects

A nutrient, slant-board technique was developed in order to estimate the losses to roots of white clover (Trifolium repens L.), caused by the feeding of the larvae of Sitona weevils. In this preliminary experiment losses of up to 50% of root length were found. This simple technique was straightforward to use and has the potential for applications in a large range of root-pest/feeding studies.