玉米种质和新品种对腐霉茎腐病和镰孢穗腐病的抗性分析

玉米是我国最重要的农作物之一,腐霉茎腐病和镰孢穗腐病是玉米生产上的重要病害。2006-2012年期间,对1647份玉米种质进行了抗肿囊腐霉茎腐病和拟轮枝镰孢穗腐病鉴定,筛选出高抗茎腐病和穗腐病的种质分别为564份和27份,占鉴定总材料的34.2%和1.6%,抗性材料分别为209份和352份,占比为12.7%和21.4%,表明高抗肿囊腐霉茎腐病的资源较为丰富,高抗镰孢穗腐病的种质相对匮乏。其中,13份种质对2种病害均表现高抗,207份种质对2种病害均表现抗性或对其中一种表现高抗而另一种表现抗性。自交系中对肿囊腐霉茎腐病和拟轮枝镰孢穗腐病表现抗性以上(含HR和R)的种质分别占总鉴定种质的56.5%和23.6%,在农家种中分别为21.2%和21.4%,表明玉米自交系中的抗性资源较农家种丰富。2009-2013年期间参加国家玉米区试的品种中,对腐霉茎腐病表现高抗、抗性、中抗、感病和高感的品种分别占11.5%、11.9%、40.1%、17.6%和18.9%。2009-2011年间,中抗以上的育成品种所占比例呈现明显上升趋势,但2012-2013年间,中抗以上的品种所占比例呈下降趋势。     

seed rot and root rot complex of beans (Phaseolus vulgaris L.)

Fusarium solani (76%),Phyllosticta phaseolina (12%) andAspergillus flavus (10%) were isolated from bean(Phaseolus vulgaris) seeds showing lesions. Out of these the first two caused 30 per cent and 20 per cent seed rotting respectively after artificial seed inoculations. When inoculum was added into the soil before sowing the seed, 35 per cent and 10 per cent pre-emergence rot ocurred and there was 35 per cent and 15 per cent post-emergence blight when soil with healthy seedlings was inoculated withF. solani andP. phaseolina respectively.F. solani caused similar lesions on bean seeds when inoculated after an injury.F. oxysporum was isolated from the roots of dried bean plants showing necrosis.     

Pseudomonads associated with midrib rot and soft rot of butterhead lettuce and endive

During the past ten years, bacterial soft rot and midrib rot of glasshouse-grown butterhead lettuce (Lactuca sativa L. var. capitata) and field-grown endive (Cichorium endivia L.) has become increasingly common in the region of Flanders, Belgium. Severe losses and reduced market quality caused by bacterial rot represent an important economical threat for the production sector. Symptoms of midrib rot are a brownish rot along the midrib of one or more inner leaves, often accompanied by soft rot of the leaf blade. Twenty-five symptomatic lettuce and endive samples were collected from commercial growers at different locations in Flanders. Isolations of dominant bacterial colony types on dilution plates from macerated diseased tissue extracts yielded 282 isolates. All isolates were characterized by colony morphology and fluorescence on pseudomonas agar F medium, oxidase reaction, and soft rot ability on detached chicory leaves. Whole-cell fatty acid methyl esters profile analyses identified the majority of isolates (85%) as belonging to the Gammaproteobacteria, which included members of the family Enterobacteriaceae (14%) and of the genera Pseudomonas (73%), Stenotrophomonas (9%), and Acinetobacter (3%). Predominant bacteria were a diverse group of fluorescent Pseudomonas species. They were further differentiated based on the non-host hypersensitive reaction on tobacco and the ability to rot potato slices into 4 phenotypic groups: HR-/P- (57 isolates), HR-/P+ (54 isolates), HR+/P (16 isolates) and HR+/P+ (35 isolates). Artificial inoculation of suspensions of HR-, pectolytic fluorescent pseudomonads in the leaf midrib of lettuce plants produced various symptoms of soft rot, but they did not readily cause symptoms upon spray inoculation. Fluorescent pseudomonads with phenotype HR+ were consistently isolated from typical dark midrib rot symptoms, and selected isolates reproduced the typical midrib rot symptoms when spray-inoculated onto healthy lettuce plants.     

Aphanomyces root rot of cauliflower

Résumé L'influence du cycloheximide sur la composition chimique des parois de deux levures Rhodotorula après 24 heures et 4 jours de croissance dans deux milieux de culture différents a été étudiée.La composition en glucides neutres ne varie que faiblement en fonction de l'âge des cellules, la détermination du rapport des oses neutres n'indiquant qu'un léger enrichissement en mannose dans les parois des cellules âgées. Chez Rhodotorula glutinis, les teneurs en hexosamines et aminoacides augmentent nettement en fonction de l'âge des cellules, cette variation ne se produit pas chez Rhodotorula rubra. Les teneurs en chitine sont dépendantes de la nature du milieu de culture mais non de l'âge des cellules sauf chez Rhodotorula glutinis.L'influence du cycloheximide sur la composition chimique se traduit par une baisse globale en protéines et par une perturbation des concentrations d'aminoacides.Le rapport molaire des oses neutres indique une baisse systématique du galactose. Les valeurs des hexosamines sont également plus faibles; la diminution de la chitine est surtout très nette lorsque les cellules se développent dans un milieu normalement favorable à son élaboration, cependant il n'apparaît pas de relation directe entre les baisses des teneurs en hexosamines et en chitine.

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Summary The influence of cycloheximide on the chemical composition of the cell walls of two Rhodotorula yeasts, cultivated during 24 and 96 hours in two different media, has been studied.The composition, of the neutral sugars varies only weakly with the age of the cells, the determination of the molar ratio revealing only a little increase of mannose.Hexosamine and aminoacids contents in Rhodotorula glutinis cells distinctly increase in old cells; this variation does not appear in Rhodotorula rubra. The content of chitine depends on the culture conditions but not on the age of cells, except with Rhodotorula glutinis.The influence of cycloheximide on the chemical structure is responsable of a general decrease of protein and a perturbation of the concentration of the different aminoacids. The molar ratio of the neutral sugars indicates a decrease of galactose in the cell walls. The values of hexosamine are also lower; the decrease of chitine is especialy appearant when the cells are cultivated in a medium which normaly favors the synthesis of this polymer, but there is no direct relation between the decrease of hexosamin and chitin.

     

Pythium root rot of crucifers

A destructive root disease of cabbage (Brassica oleracea L. var. capitata) and cauliflower (Brassica oleracea L. var. botrytis) incited by a species of Pythium Pringsheim is described as occurring in Varanasi, U.P. The pathogen was isolated on potato dextrose and corn meal agar. Pathogenicity and host range of the disease were studied. Cultural characters, morphology and developmental stages and life cycle of the fungus indicated its identity with Pythium middletonii Sparrow.     

Isolation of laccase gene-specific sequences from white rot and brown rot fungi by PCR.

Degenerate primers corresponding to the consensus sequences of the copper-binding regions in the N-terminal domains of known basidiomycete laccases were used to isolate laccase gene-specific sequences from strains representing nine genera of wood rot fungi. All except three gave the expected PCR product of about 200 bp. Computer searches of the databases identified the sequence of each of the PCR products analyzed as a laccase gene sequence, suggesting the specificity of the primers. PCR products of the white rot fungi Ganoderma lucidum, Phlebia brevispora, and Trametes versicolor showed 65 to 74% nucleotide sequence similarity to each other; the similarity in deduced amino acid sequences was 83 to 91%. The PCR products of Lentinula edodes and Lentinus tigrinus, on the other hand, showed relatively low nucleotide and amino acid similarities (58 to 64 and 62 to 81%, respectively); however, these similarities were still much higher than when compared with the corresponding regions in the laccases of the ascomycete fungi Aspergillus nidulans and Neurospora crassa. A few of the white rot fungi, as well as Gloeophyllum trabeum, a brown rot fungus, gave a 144-bp PCR fragment which had a nucleotide sequence similarity of 60 to 71%. Demonstration of laccase activity in G. trabeum and several other brown rot fungi was of particular interest because these organisms were not previously shown to produce laccases.     

Characterisation of husk rot in macadamia

The causal agent of husk rot of macadamia is often attributed to Colletotrichum gloeosporioides sensu lato. However, in recent husk rot outbreaks, the characteristic concentric ring of pycnidia of C. gloeosporioides that is associated with the disease was often absent. Due to its sporadic occurrence, the importance of husk rot is often underrated and attributed to environmental and physiological factors. In order to determine the significance, prevalence and factors that influence husk rot in macadamia, this study examined the aetiology of husk rot in Australia. The relative incidence and severity of husk rot was evaluated in several macadamia orchards over eight consecutive years. Pathogenicity assays were developed to confirm the identity of the causal agent. A range of fungi from several genera including: Diaporthe, Lasiodiplodia, Colletotrichum, Pestalotiopsis, Aspergillus, Alternaria, Nigrospora and Epicoccum were isolated from samples of macadamia pericarps with husk rot symptoms from different orchards. Fungi in the genus Diaporthe were most frequently isolated, often from symptomatic fruit. Results from pathogenicity trials showed the characteristic soft or spongy black lesions characteristic of husk rot symptoms in wounded fruits that were incubated with the diseased fruit or inoculated with a conidial suspension of Diaporthe spp. Our results suggest that injury to the macadamia fruit pericarp not only predisposes the pericarp to pathogen infection but it is a prerequisite for infection. Large variations in husk rot severity were observed over years. Husk rot severity was linked to days after anthesis and was associated with mean weekly relative humidity and minimum temperatures. This study confirmed that Diaporthe species cause husk rot in macadamia, hence, a rationale for adopting Phomopsis husk rot as the name of the disease is discussed.     

Lignin degradeation by white rot fungi

Abstract. The wood-degrading white-rot fungus Phanerochaete chrysosporium , has been the subject of intensive research in recent years and, based upon isolation of the extracellular enzyme ligninase, major advances have now been made toward elucidating the mechanism by which this fungus degrades lignin. From these developments, a model emerges which could explain the process by which wood-degrading fungi in general, attack lignin.     

Notes on basal rot of narcissus

Control of basal rot of narcissus following hot-water treatment against eelworm was equally good when 0.5% formalin was included in the bath or was used as a cold or warm steep immediately afterwards. When the formalin steep was delayed control was less good. All methods of applying formalin in connexion with hot-water treatments used in these experiments were equally harmless to growth and flowering of the bulbs.     

Sclerotium rot of sugarbeets in India

Sclerotium rot of sugar beets incited byP. rolfsii is described for the first time from India. The disease has been found widely prevalent around Pantnagar. Observations on the susceptibility of crops grown in the affected areas and the relative susceptibility of different sugarbeets varieties are presented. Ability of the pathogen to survive from one season to another under conditions at Pantnagat is indicated.Published with the approval of the Director as Paper No. 104, Journal Series, Experiment Station, UPAU Pantnagar.Ast. Prof. Plant Pathology.     

The occurrence of root rot and crown rot of rice in Gilan and Zanjan provinces, Iran

Root rot and crown rot of rice is one of the important fungal diseases of rice in Gilan and Zanjan provinces, Iran. During 1999--2002, samples of plant and soil around the roots of infected rice plants were collected and used to identify the causal agent. Root and crown parts were surface sterilized with sodium hypochlorite and then cultured on PDA (potato dextrose agar), PPA (pepton pentacholoritobenzene agar) and CLA (carnation leaf agar) media. Soil samples prepared in water agar were used to isolate the pathogen. The causal agent was identified as Fusarium moniliforme. Colonies were initially white but turned violet to grey late. Microconidia were arranged in chain and macroconidia were cylindrical and long with 3-5 septa. The disease was severe in Zanjan province particularly along Ghezel Ozan river where the infection ranged from 70-80%. Root and crown rot was more prevalent in areas where Champa and Gerdeh were being cultivated continuously. On the other hand, Sadri cultivars had relatively less infection. Persistent cultivation of rice and seed sowing method intensified disease development and caused significant economic losses.     

Biological control of white rot of onion

Summary Interactions of 123 isolates of fungi, 17 of bacteria and 22 of actinomycetes, respectively, withSclerotium cepivorum were studied in agar culture. They were grouped into 4 different types of reactions. Amongst themTrichoderma viride, Fusarium graminearum, Coniothyrium minitans andGliocladium roseum inhibited the growth ofS. cepivorum and later grew over its colony.T. viride showed a characteristic coiling around the hyphae ofS. cepivorum. T. viride andF. graminearum prevented the development of sclerotia.C. minitans was found to parasitize the sclerotia ofS. cepivorum and produced its pycnidia within them.Aleurisma carnis, Cladosporium elatum, Penicillium expansum, P. nigricans, P. notatum, P. piscarium, P. puberulum, P. rolfsii, P. urticae, P. variabile, Tilachlidium humicola andHelminthosporium sp. inhibited the growth ofS. cepivorum at a distance. Eleven isolates of bacteria and 3 ofStreptomyces sp. showed pronounced antagonistic properties againstS. cepivorum.Experiments were carried out to study the effects on white rot development in soil of organisms selected from agar plate tests. None of the antagonistic micro organisms had any deleterious effects on onion growth. Of the organisms testedP. nigricans gave the best results in controlling white rot infection.This work was carried out at the Department of Botany, The University, Birmingham, England. I wish to thank Prof.C. J. Hickman for his invaluable advice and encouragement.     

蓝莓腐霉根腐病的病原菌

在山东青岛新发现一种蓝莓根腐病害,症状最初出现在根部,病根腐烂坏死,根状茎维管束和皮层变黑,导致根数量减少,叶片变黄、变红,植株生长不良,严重时叶片全部脱落,植株死亡。通过组织分离法和菌丝段分离法获得纯化菌株HMQAU 180018,经柯赫氏法则验证,综合形态学特征及ITS区和cox I基因序列分析,菌株HMQAU 180018被鉴定为畸雌腐霉Pythium irregulare。这是国内首次描述畸雌腐霉引起蓝莓根腐病的报道。     

Synthetic dye decolourization by white rot fungi

Synthetic dyes are integral part of many industrial products. The effluents generated from textile dyeing units create major environmental problems and issues both in public and textile units. Industrial wastewater treatment is one of the major problems in the present scenario. Though, the physical and chemical methods offer some solutions to the problems, it is not affordable by the unit operators. Biological degradation is recognized as the most effective method for degrading the dye present in the waste. Research over a period of two decades had provided insight into the various aspects of biological degradation of dyes. It is observed that the white rot fungi have a non-specific enzyme system, which oxidizes the recalcitrant dyes. Detailed and extensive studies have been made and process developed for treatment of dye containing wastewaters by white rot fungi and their enzyme systems. An attempt is made to summarize the detailed research contributions on these lines.     

Dibenzyl sulfide metabolism by white rot fungi

Microbial metabolism of organosulfur compounds is of interest in the petroleum industry for in-field viscosity reduction and desulfurization. Here, dibenzyl sulfide (DBS) metabolism in white rot fungi was studied. Trametes trogii UAMH 8156, Trametes hirsuta UAMH 8165, Phanerochaete chrysosporium ATCC 24725, Trametes versicolor IFO 30340 (formerly Coriolus sp.), and Tyromyces palustris IFO 30339 all oxidized DBS to dibenzyl sulfoxide prior to oxidation to dibenzyl sulfone. The cytochrome P-450 inhibitor 1-aminobenzotriazole eliminated dibenzyl sulfoxide oxidation. Laccase activity (0.15 U/ml) was detected in the Trametes cultures, and concentrated culture supernatant and pure laccase catalyzed DBS oxidation to dibenzyl sulfoxide more efficiently in the presence of 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) than in its absence. These data suggest that the first oxidation step is catalyzed by extracellular enzymes but that subsequent metabolism is cytochrome P-450 mediated.