András Takács

Detection of cereal viruses in wheat ( Triticum aestivum L.) by serological and molecular methods

The reliable monitoring of field virus infections of crop species is important for both farmers and plant breeders. The aim of this study was to detect virus infections of winter wheat in the 2006/2007 season. Twelve well-known winter wheat varieties were sown on two different dates (11 th of October and 3 rd of November 2006). Leaves of two individuals from each genotype were collected on 23rd of April 2007 to detect the virus infections ( Barley stripe mosaic virus — BSMV, Barley yellow dwarf virus — BYDV-PAV, Wheat dwarf virus — WDV and Wheat streak mosaic virus — WSMV) after an extra mild autumn- and wintertime. Virus infections were detected by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). The aphid-transmitted BYDV-PAV was found frequently whereas other viruses were presented very rarely or were not detected. Forty-six per cent of the tested wheat plants proved to be infected by BYDV-PAV in ELISA, while using PCR, the virus infections with BYDV-PAV was found in 58% o...

Natural weed hosts of tomato spotted wilt virus (TSWV) in Hungary

Tomato spotted wilt virus (TSWV) is the type member of the Tospovirus genus. It was first described on tomato plants in Australia (Brittlebank 1919). During the past century the virus became distributed throughout all over the world. In Europe, TSWV was found first in England by Smith (1932). Nagy and Ligeti (1972) found it in tobacco plants in Hungary. TSWV causes, severe yield losses in tobacco, pepper, tomato and potato production in Hungary (Gaborj&nyi et al. 1993, 1995, 2002, Horv&th et al. 2001). TSWV is transmitted by thrips vectors (e.g. Frankliniella occidentalis and Thrips tabaci) in a circulative manner (Jenser ds Tasnadi 1989). TSWV has more than 1000 natural and experimental host plant species (Parrella et al. 2003). Infected weeds that are hosts of the thrips vectors also, in vegetable-growing regions play an important role in the epidemiology of the virus. Under our climate, TSWV can overwinter in infected thrips vectors and virusreservoir weeds (Jenser 1995). TSWV has become one of the most important virus pathogen in vegetable production on the southern part of Hungary, because of widespreading of virus vector (F. occidentalis) and virus reservoir weed species.

Virus infection of ornamental plants in Hungary

Recently the economic importance of the ornamental plant production has shown remarkable growth. Following the countrys joint to the EU increased competition has become characteristic of the Hungarian market. More than 20 viruses have been isolated in the various vegetatively propagated Petunia species and varieties [Richert (1992), Lesemann and Dalchow (1995), Bellardi et al. (1996), Mavric et al. (1996) Salamon (1996), Richert-POggeler and Shepherd (1997), Feldhof et al. (1998), Boonham et al. (1999), Alexandre et al. (2000)]. Metelik et al. (1994, 1996), Mokrd and Gfitzovd (1994), Lesemann and Winter (2002) as well as Pham et al., (2002) examined the health condition of Zanthedeschia aetiopica and other Zanthedeschia species. The presence of Bean yellow mosaic virus (BYMV), Dasheen mosaic virus (DsMV), Cucumber mosaic virus (CMV), Konjac mosaic virus (KoMV) and Tomato spotted wilt vims (TSVW) were detected. Hosta virus X (HVX) and Impatiens necrotic spot vims (INSV) were isolated in the examined Hosta species (Lockhart 2002). Lockhart et al. (2002) verified the presence of Turnip mosaic virus (TuMV) in Heuchera samples and that of Alfalfa mosaic vims (AIMV) in Pulmonaria species. The goal of our work was to make a virological survey of herbaceous ornamental plants in Hungary.

Early competition between tomato and Convolvulus arvensis in additive experiment

Introduction Weeds can successfully compete with the cultivated plants, causing considerable reduction in crop quantity and quality. The majority of competition studies between crops and weeds are based on addititve experiments. In these studies two species (crop and weed) are grown together. The density of the crop is maintained constant, while that of the weeds is varied (Varga et al. 2006). Tomato is one of the most important vegetable in Hungary both under cover and field conditions. Basic criteria for tomato production is that fields must be kept free from different pests, pathogens and weeds, with special regards to dicot weeds, because except mechanical weed control no convenient technology is available against them in tomato cultures. When no suitable area is chosen for tomato production or the weed control of the forecrop does not manage, field bindweed (Convolvulus arvensis) can cause problems (Hunyadi et al. 2000). C. arvensis is a vining perennial plant with adventitious buds on its root system, reproducing both vegetatively and to a lesser extent by seeds (Weaver – Riley 1982). The aim of our work was to investigate the effect of different weed density of C. arvensis seedlings on the early development of tomato.

Virus–virus interactions

Over the past quarter century there have been massive applications of new molecular, cell biology, and genetics techniques to research plant viruses. Hundreds of complete virus genomes were sequenced and analyzed, their constituent genes and control elements identified, and similarities and differences revealed in genome organization, allowing for the taxonomic classification of viruses. Numerous virus replication systems were described and some viral replicases isolated. Especially good progress was made in understanding cell-to-cell and long-distance viral transport within plants; in cloning dominant and recessive plant genes controlling virus resistances and identifying the cognate viral avirulence factors; in unraveling mechanisms of viral transmission by invertebrate and plasmodiophorid vectors; and in showing, through these advances, how viruses utilize and subvert endogenous eukaryotic processes. The discovery of gene silencing and viral silencing–suppressor proteins transformed thinking about how virus replication is controlled and explained the phenomena of recovery from disease, cross protection, and synergy between unrelated viruses. Transgenic, virus-resistant plants were created and tested successfully in field conditions, and a few were commercialized. Factors underlying the appearance of new disease epidemics were identified. Genetic recombination was reported and found to make an important contribution to generating virus variation. Additionally, some major viral evolutionary pathways were identifed through comparative genome analysis. The stage is set for further major advances in the coming decades.

General properties of grapevine viruses occurring in Hungary

The past fifty years important advances have been made in the field of grapevine virus research, including characterization of pathogens and control measurements. Still the occurrence of Grapevine fanleaf virus (GFLV), Arabis mosaic virus (ArMV), Tomato black ring virus (TBRV), Grapevine chrome mosaic virus (GCMV), Alfalfa mosaic virus (AMV), Grapevine Bulgarian latent virus (GBLV), Grapevine fleck virus (GFkV), Grapevine leafroll- associated viruses (GLRaV1-4), Grapevine virus A (GVA), Grapevine virus B (GVB) and Grapevine rupestris stem pitting- associated virus (GRSPaV) have been reported in Hungary and characterized by conventional methods as woody indexing, herbaceous indexing and serological methods. Among grapevine viruses the Grapevine line pattern virus (GLPV) seems to be uncial; because it was reported only in Hungary. Causal agents of several grapevine diseases, like enation, vein necrosis and vein mosaic remained undiscovered. These virus-like diseases occurred only sporadically, without economic importance.

Herbicide-Affected Plant Metabolism Reduces Virus Propagation

Abstract It has been previously shown that certain herbicides or plant extracts inhibited the viral infection. The goal of this study was to investigate the effect of Obuda pepper virus (ObPV) infection and herbicide or plant extract treatments on the photosynthetic processes of the host plants to get informations about the interactions of these factors. In Capsicum annuum- ObPV host-virus relations the virus infection slightly increased the activity of photosystem II (PSII), as it was supposed from fluorescence induction parameters. Chlorophyll content of leaves was also elevated probably due to virus-induced growth inhibition. The herbicide Stomp (active ingredient: pendimethalin) incorporated into the soil one week before planting (preplant treatment) together with virus infection even strengthened these effects in agreement with previous observations that this herbicide always did not prevent virus infection or reduce virus concentration in hosts. In ObPV-infected Nicotiana tabacum the structural changes showed similar tendency like in ObPV-infected C. annuum, but PSII efficiency did not significantly differ from that of the control. However, non-photochemical quenching (NPQ) increased because of the strongly decreasing CO2 fixation activity. Though simultaneous application of a water extract of Cirsium arvense shoot caused a little stronger inhibition of CO2 fixation, little loss in production was obtained due to significant reduction in virus concentration. In Solanum nigrum-ObPV relation the slightly increasing tendency of the values of actual PSII quantum efficiency could be related to the probably elevated ratio of reaction centre components (increased chlorophyll a/b ratio) in the thylakoids. Application of the herbicide Fusilade S (active ingredient: fluazifop-P-butyl) at 4-6 leaf stage as a postemergence treatment practically prevented systemic virus infection and the virus-induced changes of photosynthesis are probably due to inhibiting the virus infection/replication process.

Epidemyology of tomato pathogen viruses in Hungary

Introduction Tomato (Lycopersicon esculentum) is an important crop on the basis of its high consumption, nutritional and cash value in temperate and tropical countries. Tomato crop production is over 4 million ha and about 110 million tonne on the world. The largest producers are in Asia because the half of the cultivation area and also the production are in these countries. In the European countries tomato is produced mainly under greenhouse. The gene centres is in the regions of the Andes in Peru, Ecuador and Chile. The cultivated tomato is a member of the Lycopersicon genus in the Solanaceae family. After the molecular characterization of Lycopersicon genus were transferred to Solanum (Marshall et al. 2001). Wild Lycopersicon species can be used in resistance breeding (Alexander and Hoover 1955). Six members (L. pimpinellifolium, L. chesmanii, L. parviflorum, L. chmielewski, L. hirsutum and L. penelii) from the Lycopersicon genus could relatively easily cross with cultivated tomato. This species could be use as sources of insect and disease resistance (Rick 1979; Taylor 1986; Tigchelar 1986; Kegler and Friedt 1993). There are about forty different viruses species are infecting Solanaceous vegetable crops, or potato (Solanum tuberosum) and tobacco (Nicotiana tabacum). Among them Potato virus Y (PVY), Tomato spotted wilt virus (TSWV) and other different Tobamoviruses (e.g. Tobacco mosaic virus) can cause severe yield losses. Pepino mosaic virus (PepMV) is a recently emerged viral pathogen in Hungary. It was first reported from pepino (Solanum muricatum) plants from Peru (Jones 1980). The PepMV has several hosts in different plant families (e.g. Amaranthaceae, Solanaceae). The virus is easily mechanically transmitted. PepMV transmitted by workers touching infected plants, and can also transmit by contact between plants. Maybe it is carried in tomato seeds and potentially can also transmit by Bombus bees. The rapid spread of PepMV was reported from European tomato cultivars in the last years (Verhoven et al. 2003). In Hungary PepMV was found first in 2004 from a glasshouse between the area Danube and Tisza Rivers (Forray et al. 2004).

Virus-induced physiologic changes in plants

Numerous investigations of crops infected by viruses have been, and continue to be, conducted on both the physiologic and biochemical levels. Pathologic processes have been discussed on the basis of their biochemical and physiologic mechanisms, such as their effects on photosynthetic processes, respiration, nucleic acid and protein synthesis, hypersensitivity reactions, phytohormones, nutrient transport, and cell wall and intracellular membrane structures.

Hosts and non-hosts in plant virology and the effects of plant viruses on host plants

Abstract Plant viruses, as obligate parasites of host plants, can cause extreme injury to plants. They contain nucleic acid (ribonucleic acid [RNA] or deoxyribonucleic acid [DNA]) and a protein capsid. Viruses can be classified on the basis of their chemical compounds and morphologic, biologic, pathologic, and molecular characteristics. Viruses can penetrate a host plant cell only in a passive way, through a microscab or with the help of different vectors, such as insects. The majority of plant viruses have a broad range of hosts (e.g. Cucumber mosaic virus [CMV], Tomato spotted wilt virus [TSWV]), whereas others have a narrower host range (e.g. Sowbane mosaic virus [SoMV]). Viral infections can be identified on the basis of the symptoms appearing on test plants (for more exact and qualitative identification, other methods, such as serologic and molecular ones, are necessary). Plant viruses create a close biologic unit with their host plant cell. Some artificial and natural substances are believed to inhibit virus replication and cell-to-cell movement, but these substances cannot act as viricides in vivo. Biologic decline due to viral infection can greatly contribute to a reduction in the competitive ability of weeds in agroecosystems. Therefore, viruses can indirectly contribute to weed control.