Isolation and pathogenicity of Phytophthora species from declining Rubus anglocandicans

Rubus anglocandicans is the most widespread and abundant blackberry species within the European blackberry (Rubus fruticosus) aggregate in Western Australia (WA). European blackberry is also one of the 32 Weeds of National Significance in Australia. A disease recorded as ‘blackberry decline’ was first observed in some blackberry sites in WA in 2006. A disease survey was conducted in the Manjimup‐Pemberton region along the Warren and Donnelly River catchments in WA between 2010 and 2012. Phytophthora amnicola, P. bilorbang, P. cryptogea, P. inundata, P. litoralis, P. multivora, P. taxon personii, P. thermophila and a P. thermophila × amnicola hybrid were recovered from declining and adjacent decline‐free sites, as well as from streams and rivers. Phytophthora cinnamomi was isolated from dying Banksia and Eucalyptus species from two non‐decline sites. Of these species, P. bilorbang and P. cryptogea were more pathogenic than the others in under‐bark inoculations using excised stems (primocanes), in planta primocane inoculations in blackberry growing wild in native forest stands, and in glasshouse pot trials. It was concluded that blackberry decline is a complex syndrome and Phytophthora species, in particular P. bilorbang and P. cryptogea, together with temporary inundation, are major biotic and abiotic factors contributing to blackberry decline.     

Phytophthora species in oak ecosystems in Turkey and their association with declining oak trees

From 1999 to 2001, a survey on the occurrence of Phytophthora spp. in the rhizosphere soil of healthy and declining oak trees was conducted in 51 oak stands in Turkey. Seven Phytophthora spp. were recovered from six out of the nine oak species sampled: P .  cinnamomi , P .  citricola , P .  cryptogea , P .  gonapodyides , P .  quercina , Phytophthora sp. 1 and Phytophthora sp. 2. The most frequently isolated species, P .  quercina , was very common on slopes susceptible to drought. It occurred in four different climatic zones and on six Quercus spp., suggesting that it is native to oaks. The second most common species, P .  citricola , was separated into three subgroups: type C was recovered only in Anatolia, whereas A and B occurred only in the European part of Turkey. Phytophthora cinnamomi was recovered at one site only, and may not be involved in oak decline in Turkey. The other four species were recovered sporadically. On affected sites there was a significant association between deteriorating crown status and the presence of Phytophthora spp., particularly P .  quercina . The occurrence of Phytophthora species was significantly influenced by soil pH. Stem inoculation tests on oak seedlings revealed that Q .  petraea was the most susceptible species.     

Involvement of soilborne Phytophthora species in Central European oak decline and the effect of site factors on the disease

A survey was made on the occurrence of soilborne Phytophthora species in 35 oak stands on a range of geologically different sites in Bavaria. The most widespread species were P. quercina , P. cambivora and P. citricola . Seven other Phytophthora species were isolated infrequently. The fine root systems of 106 healthy and 111 declining mature trees of Quercus robur and Q. petraea were intensively investigated. The results indicate that, depending on the site conditions, at least two different complex diseases are referred to under the name 'oak decline'. On sites with a mean soil pH (CaCl₂)  3·5 and sandy-loamy to clayey soil texture Phytophthora spp. were commonly isolated from rhizosphere soil, and highly significant correlations existed between crown transparency and various root parameters. Oaks with P. quercina or other Phytophthora spp. in their rhizosphere had markedly higher levels of fine root damage than oaks without Phytophthora spp., and were subject to a relative risk of severe crown symptoms of 2·1 and 2·8, respectively. In contrast, in stands with sandy to sandy-loamy soils and a mean soil pH  3·9, Phytophthora spp. were not found. In these stands, correlations between crown transparency and various root parameters were either less significant or not significant. It is concluded that Phytophthora species are strongly involved in oak decline on sandy-loamy to clayey sites with a mean soil-pH (CaCl₂)  3·5.     

Occurrence of Globodera pallida in Hungary

Golden potato cyst nematode, Globodera rostochiensis , has been known to occur in Hungarian potato fields for more than 20 years. The Hungarian NPPO has been carrying out a country-wide Globodera monitoring programme since 1995 and has inspected 16 000 samples. Until 2000, all records were of G. rostochiensis . However, in 2001, three localities in Pest county were found to be infested with Globodera pallida . This was the first official record of G. pallida in Hungary. The two species have been found together in five fields. Unmixed populations of G. pallida have not been found. Identification was based on morphometric data, as well as on biochemical methods (ELISA technique).     

Characterisation of Isolates of Phytophthora infestans From Hungary

A total of 36 single-lesion isolates were collected from 9 crops of potato and 13 of tomato in different regions of Hungary in the past decade, particularly in 1998. These were analysed for mating type, sensitivity to metalaxyl, allozyme genotype at glucose-6-phosphate isomerase and peptidase loci and genotype at 24 loci detected using the multilocus RFLP probe RG57. The ratios of the mating types A1 to A2 were 8:9 and 4:15 among isolates recovered from potato and tomato, respectively. Resistance to metalaxyl was found more frequently among isolates from potato and in the A1 mating type. The populations were not clearly differentiated on the basis of host origin. All isolates were homozygous (100/100) at the locus for glucose-6-phosphate isomerase. Unlike in other European countries, the most common peptidase allele was 96. Genotypes at the peptidase locus were 96/96 (50%), 96/100 (27.7%) and 100/100 (16.6%). In addition, one isolate from 1993 and another from 1998, were defined as 83/96, a genotype that had not been described elsewhere. The 18 RG57 fingerprints that were observed among 36 isolates, with one exception, seem to be unique to Europe. On the basis of combined genotypic traits, 20 multilocus genotypes were designated. These data, which reveal a remarkable variability with unique genotypes of the late blight pathogen, suggest that migration and sexual and/or asexual recombination have a role in the recent evolution of the pathogen in Hungary.     

茄子绵疫病的发生与防治

茄子绵疫病是茄子的重要病害之一，在我国各地均有发生，茄子各生育期皆可受害，一般损火200％-30％，发病严重损失超过50％。此病除茄子外，还可侵染番茄、西瓜、辣椒、黄瓜以及马铃薯等蔬菜。     

Antimicrobials in Phytophthora isolation media and the growth of Phytophthora species

Many recently described Phytophthora species detected using high-throughput sequencing have never been isolated into culture. NARH is a commonly used isolation medium containing cornmeal agar with n ystatin 22.72 ppm, a mpicillin 100 ppm, r ifampicin 10 ppm, and h ymexazol 50 ppm. We investigated whether the antimicrobial compounds in this medium selectively inhibit growth of some Phytophthora species. Growth of 10 Phytophthora species from 10 Phytophthora clades was tested in NARH medium with antimicrobials in a range of concentrations, singly and in combination: nystatin 12.5–100 ppm, ampicillin 62.5–500 ppm, rifampicin 5–40 ppm, hymexazol 12.5–100 ppm and in addition, chloramphenicol 5–40 ppm. Two combinations of antimicrobials that supported good growth of the greatest number of species were selected: (a) nystatin 12.5 ppm, ampicillin 250 ppm, rifampicin 10 ppm, and hymexazol 12.5 ppm, and (b) these compounds with the addition of chloramphenicol 5 ppm. Subsequently the growth of 47 Phytophthora species from all clades was tested in media with these two combinations and standard NARH, both in aseptic culture and in plates with leaf baits infected from soils known to be infested with Phytophthora. Although growth of some Phytophthora species was better with the new combinations of antimicrobials in aseptic culture, suppression of competing microorganisms was best in standard NARH. Sensitivity to the NARH antimicrobials is not the reason for the difficulty or failure of isolating many species detected using high-throughput sequencing. NARH is a robust and appropriate medium for isolation of Phytophthora species from all clades.     

绞股蓝疫病的发生与防治技术

绞股蓝又称七叶胆、五叶参、小叶五爪龙等,俗称母猪藤。为葫芦科绞股蓝属植物。以全草供药、食兼用。含有多种氨基酸和微量元素,并含50多种皂甙。其中有5种绞股蓝皂甙和人参皂甙结构相同,因此,有“南方人参”之称。陕西安康为绞股蓝原产保护地,全市有4个县、区大面积种植。目前人工栽培面积6900hm2,为农民增收发挥了重要作用,也是安康市委、市政府提出“药、水、游”战略决策的内容之一,为安康一大主导产业。但是,随着人工栽培面积扩大,时间增长,加之气候异常变化,田间管理粗放,绞股蓝病害逐年加重,特别是疫病常造成绞股蓝成片死亡,一般病田…     

几种阔叶杂草对小麦产量的影响

麦田杂草不仅消耗土壤中的水分、养分,浪费光热资源,而且影响小麦产量。它们既是一个复杂的群体,又是形态特征各异的个体。其对小麦产量的影响因密度、种类、种群结构而异。所以,开展杂草对小麦影响的研究,是提高麦田化学除草技术的重要组成部分。为此,笔者于2001～2003年结合生产实际,开展了有关项目的调查研究。1麦田杂草数量对小麦产量的影响由于不同年份杂草的种群结构不同,所以此项调查不分杂草种类,是同一田块各种杂草在不同密度下对小麦产量的影响。调查选择地力均匀、小麦基本苗均匀、杂草数量大的田块,人为划分为无草、60株/m2(相…     

Fungicide resistance in soil-borne Phytophthora species1

Systemic fungicides such as the phenylamides and phosphonates have provided new opportunities for chemical control of soil-borne Phytophthora species. Potential problems in their use include biodegradation in soils, and the emergence of pathogen isolates resistant to these compounds. Resistance to phenylamides is well known in leaf-infecting Oomycetes, but less is known about the development and relative fitness of resistant isolates among populations of soil-borne Phytophthora species. Experiments with P. capsici and P. palmivora have shown that stable resistant and virulent isolates can be selected under laboratory conditions. Some mutants resistant to both metalaxyl and fosetyl-A1 have been recovered, with growth rates and sporulation equivalent to parental wild types. Selected mutants proved able to compete in vivo with fungicide-sensitive wild types in the absence of the compounds. More information is required to fully evaluate the implications of these results for chemical control of soil-borne Phytophthora species in the field. Résistance des Phytophthora du sol aux fongicides     

长春花疫病的发生危害与防治

进口F₁代长春花上疫病 (Phytophthora nicotianae)是普遍发生的一种病害 ,危害较重。经对其发生规律、发病条件、药剂筛选及防治等方面研究 ,结果表明 ,该病的发生与长春花生育期及湿度等密切相关 ,RH>80%时病害迅速发展。现蕾期至初花期为病害易发期 ,克露等3种药剂对其防效达90%以上     

Occurrence of metalaxyl-resistant ttrains of Phytophthora infestans in Dutch potato fields

Samenvatting In de zomer van 1980 gaf in een aantal gevallen het systemische fungicide metalaxyl een zeer onvoldoende werking te zien tegen de aardappelziekte.Phytophthora infestans-isolaten die uit de desbetreffende percelen werden verkregen vertoonden in een drijftoets een zeer geringe gevoeligheid voor het fungicide in vergelijking met isolaten uit percelen waar gebruik werd gemaakt van maneb/fentin-acetaat combinaties en waarin nagenoeg geen aantasting voorkwam.De oorzaak van de onvoldoende werking van metalaxyl moet worden gezocht in het ontstaan van metalaxyl-resistente stammen in de populatie, die als gevolg van de voor de aardappelziekte geschikte weersomstandigheden en de veelvuldige toepassing van alleen metalaxyl zich ongebreideld konden vermenigvuldigen.Metalaxyl-resistentie kwam voor in verschillende fysio's. Dit wijst erop dat de resistentie op meerdere plaatsen is ontstaan. Opmerkelijk was dat éé van de resistente fysio's nooit eerder in Nederland was geisoleerd.     

Metabarcoding and development of new real‐time specific assays reveal Phytophthora species diversity in holm oak forests in eastern Spain

The evergreen holm oaks (Quercus ilex subsp. ilex and Q. ilex subsp. ballota) are the most representative tree species in the Iberian peninsula and the main tree species in oak‐rangeland ecosystems (dehesas). Oak decline in western, central and southern parts of Spain has been associated with root rot caused by Phytophthora cinnamomi for decades. However, Phytophthora species such as P.  quercina and P. psychrophila have recently been found associated with Quercus decline in eastern Spain where calcareous soils are predominant. Soil and root samples from two Quercus forests presenting decline symptoms in two different geographical areas in eastern Spain (Carrascar de la Font Roja and Vallivana) were analysed by amplicon pyrosequencing. Metabarcoding analysis showed Phytophthora species diversity, and revealed that an uncultured Phytophthora taxon, named provisionally Phytophthora taxon ballota, was the predominant species in both areas. In addition, a real‐time PCR assay, based on the pyrosequencing results, was developed for the detection of this uncultured Phytophthora taxon, and also for the detection of P. quercina. TaqMan assays were tested on soil and root samples, and on Phytophthora pure cultures. The new assays showed high specificity and were consistent with metabarcoding results. A new real‐time PCR protocol is proposed to evaluate the implication of different Phytophthora spp. in oak decline in eastern Spain.     

日光温室辣椒疫病发生规律及综合防治对策

辣椒疫病是本地区日光温室辣椒生产中的常见高发病害之一。笔者通过连续4年的多点温室田间调查研究与综合防治示范,初步明确和掌握了该病在本地区的田间发病症状、发病条件及发生规律,并从农业防治、物理防治、生态防治及化学防治等方面总结提出了一套较为系统完善的、科学实用的综合防治对策,以指导生产实践。     

Standard and Swedish variant types of the hybrid alder Phytophthora attacking alder in Hungary

A new Phytophthora disease of common alder (Alnus glutinosa) similar to that previously reported in several countries in Europe has been observed in Hungary. Based on these earlier studies, the alder Phytophthora was considered likely to be a hybrid between P cambivora and a P fragariae-like species: across Europe a range of new alder Phytophthora is spreading that comprise a range of heteroploid hybrids including a 'standard' hybrid type and several other hybrid types termed 'variants'. Phenotypic and molecular features of the pathogen in Hungary were characterised and compared with isolates from elsewhere. The morphologies of five isolates from one region (Hévíz) resembled the common, 'standard' type, whereas the three isolates from another region (Hanság) exhibited traits similar to those of one of the 'variant' types, ie the Swedish 'variant'. Molecular markers of these two groups of Hungarian isolates also represented a good fit to those of the standard type and the Swedish variant, respectively. Isozyme patterns and profiles of restriction fragments of the entire internal transcribed spacer (ITS) region or mitochondrial DNAs and of RAPD-PCR products did not differ within a group, but distinct polymorphisms were exhibited between the two groups of isolates. Southern analysis of random amplified polymorphic DNA (RAPD) revealed the homologous nature of co-migrating bands of P cambivora and the isolates of alder Phytophthora. Furthermore, restriction fragment profiles of the ITS region of ribosomal DNAs and the mtDNAs were consistent with reported biparental origin of alder Phytophthora. The hybrid status of these continuously evolving pathogens raises many issues and challenges concerning efficient control measures.