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Economically important viruses such as Tomato spotted wilt virus, genus Tospovirus, are transmissible mechanically and mainly by two thrips species (Thrips tabaci and Frankliniella occidentalis) in Hungary (1). Samples (31) of eight ornamental plant species (Catharanthus roseus, Cyclamen persicum, Dendranthema × grandiflorum, Eustoma grandiflorum, Gerbera sp., Impatiens walleriana, Ocimum basilicum, and Verbena hybrida) were studied. Symptoms including color breaking on flowers and necrotic symptoms on leaves were observed on four samples (C. persicum, I. walleriana, O. basilicum, and E. grandiflorum). Infection by Impatiens necrotic spot virus (INSV) was determined by double-antibody sandwich-ELISA and triple-antibody sandwich-ELISA using antisera obtained from Loewe (Sauerlach, Germany) and the DSMZ. Back inoculation with the F. occidentalis vector was also carried out to Lycopersicon esculentum as indicator plants. Back inoculation was also positive for INSV by symptoms and ELISA. The high amount of ornamental plant production together with the use of virus-infected propagation material and the increasing thrips vector populations may result in significantly increased establishment and distribution of INSV in Hungary. References: (1) M. L. Daughtrey et al. Plant Dis. 81:1220, 1997.

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The main characteristics of a substitutive experiment is that the proportions of two species in the mixtures are varied while the overall density of the two species is maintained constant - a replacement series. In our experiments early competition between sunflower and field bindweed (Convolvulus arvensis) was studied in a replacement studies under glasshouse conditions. Pot experiments were set up with the following treatments: 1, sunflower 100% (6 plants pot(-1)); 2, sunflower 66.6% (4 plants pot(-1)) + C. arvensis 33.3% (2 plants pot(-1)); 3, sunflower 33.3% (2 plants pot(-1)) + C. arvensis 66.6% (4 plants pot(-1)); 4, C. arvensis 100% (6 plants pot(-1)). Sixty eight days after sowing dry weight of shoots and roots were measured and nitrogen (N), phosphorus (P) and potassium (K) content was also determined. Dry biomass production of sunflower was almost twice higher as compared to that of C. arvensis without interspecific competition. Dry weight of sunflower and C. arvensis shoots and roots for a plant continuously decreased by reducing their proportion in the mixtures. Higher biomass production of sunflower suggests, that its development is faster at the beginning of vegetation penod, therefore sunflower has better competitive ability in sunflower--C. arvensis mixtures in the early competition as compared to C. arvensis. Shoot:root ratio of plants did not change considerably in mixtures, but generally was ten times higher in sunflower plants, as compared to that of C. arvensis. Shoots generally contained macro elements at higher concentration as compared to those of roots. Total NPK content of sunflower was reduced by 53 and 82% for a pot, as its proportion decreased in the mixtures. More severe reduction in NPK content was observed in case of C. arvensis, which also proves stronger competitive ability of sunflower in the early vegetation.

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Susceptibility of 33 Lycopersicon species and varieties to Tobacco mosaic virus (TMV) and Cucumber mosaic virus (CMV) were studied. Plants were mechanically inoculated with the C/U1 strain of TMV and U/246 strain of CMV. Virus infection was checked by symptomatology, DAS ELISA and back inoculation (biotest). All the studied Lycopersicon species and varieties were susceptible to TMV-C/U1. L. esculentum Mill. convar. infiniens Lehm. var. flammatum Lehm., L. esculentum Mill. convar. fruticosum Lehm. var. speciosum Lehm. and L. esculentum Mill. convar. infiniens Lehm. var. validum Bail. showed extreme resistance to CMV-U/246. The other 30 species and varieties were susceptible to CMV-U/246. New compatible and incompatible host-virus relations have been reported. The extreme resistant Lycopersicon varieties could be used as resistance sources in tomato breeding.

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It is clearly seen from data that roots of Convolvulus arvensis L. have more and less intensive regenerative period during growing season. The more intensive period is in autumn, because in that time roots culminate nutrients, carbohydrate as starch and sugar. The less intensive regenerative or shoot-growing period is in spring, called "late spring bud dormancy". Experiments were conducted to get more information and further details about the regenerative capacity of roots close to and far from the collar of Convolvulus arvensis L. Root segments closer to collar have an intensive regenerative capacity than those ones further to collar. By data of Bakke et al. (1939) is well known, roots exhumed from deep soil layers are able to create shoots with low intensity. So finally we can exclaim that regenerative capacity is decreasing further to collar. Using mechanical weed control it is sufficient to till the upper layer of soil, but many times. Chemical treatments are most effective in the integrated weed control. It is clearly seen that auxin-type herbicide such as 2,4-D, fluroxipir, MCPA. dicamba give the best result. They gave 95% weed control effect used them separately or in combination with other herbicides. Combination of Banvel 480 S (dicamba) and Logran 75 WG (triasulfuron) introduced 95% weed control effect. Only one time got absolutely 100% weed control effect, in the case of Glyphosate active substance. Caused total plant destruction. Excellent result was given with the application of Pledge 50WP (flumioxazin). Herbicides mentioned above are absolutely allowed to take an important and significant part in chemical plant protection against Convolvulus arvensis L. Other herbicides like Granstar 75DF (tribenuron-methyl), Basis 75DF (rimsulfuron + tifensulfuron-methyl) and Huszár (jodosulfuron-methyl-sodium + mefenpir-diethyl) are not so effective against Convolvulus arvensis L., as compared to the previous ones.

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The aim of our investigations was to study the susceptibility of 22 weed species to Pepino mosaic virus (PepMV). Seven plants of each species were mechanically inoculated at 4-6 leaf stage with PepMV in a vector free virological glasshouse. Inoculated plants were tested on the basis of symptoms, by DAS ELISA serological method and back inoculation. Among the 22 weed species, only some Solanum ones (S. aethiopicum, S. dulcamara, S. luteum, S. nigrum) were susceptible to PepMV infection. All of them--except S. aethiopicum--belong to Hungarian weed flora, therefore these weeds--occurring mainly in tomato ecosystems--may play important role in the epidemiology of PepMV. Other 18 weed species seemed to be resistant to PepMV, and on the basis of back inoculation not even latent infection has been observed.

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Weeds, as alternative hosts of plant viruses and nutrient plants of virus vectors play important role in virus ecology and epidemiology. The aim of our study was to discover new weed-virus relations. Therefore some weed species were mechanically inoculated with 28 viruses (strains or isolates) maintained in our glasshouse. Different weed species with and without visible symptoms were collected from agro-, water ecosystems and wastelands of Hungary between 1997 and 2003. Virus infections were evaluated by biotests, DAS ELISA serological methods, electronmicroscopy and immunosorbent electronmicroscopy (ISEM). Under glasshouse conditions Ambrosia artemisifolia was considered as a virophob species, showing resistance to all viruses listed above. A series of new artificial (Chenopodium album--SoMV (LH+SH)*, AMV (LH+SH); C. berlandieri--PVY(NTN) (LH), AMV (LH+SH), CMV (LH), SoMV (LH+SH), ObPV (LH+SH), ZYMV-10 (LH): C. ugandae--ObPV (LH), SoMV (L); C. glaucum--ObPV (LH), SoMV (L); Echinocystis lobata--PVX (L), ZYMV (LH+SH); Solanum nigrum--MYFV (LH+SH), PVY(N) (L), PVY(NTN) (LH+SH), SoMV (LH), TMV (SH), CMV (SH); S. dulcamara--CMV-U/246 (SH), PVY(NTN) (LH), SoMV-H (L), TMV-O (L); S. luteum--PVY(N) (SH), PVY(NTN) (LH+L), TMV(SH).) and natural (Asclepias syriaca--TMV, AMV, TSWV; Alisma plantago-aquatica--PVY, SoMV; Ambrosia artemisiifolia--CMV; Chenopodium album--CMV, PVS, PLRV; C. hybridum--CMV; Cirsium canum--CMV, PVM; Carex vulpina--CMV; Comium maculatum--PVY; Datura stramonium--PVA, PVX, PVS, PVM, CMV, TMV; Lysimachia vulgaris--ArMV, BNYVV, CMV, TMV; Lythrum salicaria--ArMV; Malva neglecta--CMV; Mercurialis annua--SoMV; Solanum nigrum--CMV, PVY, PVY(N); Solidago gigantea--CMV, RpRSV, BNYVV; Stenactis annua--PVM, PVA) weed--virus relations were detected. The epidemiological role of perennial hosts (A. syriaca, A. planlago aquatica, C. canurm, L. vulgaris, L. salicaria, S. gigantea) is especially high, because they can serve as infection sources as well as overwintering hosts of different plant viruses.

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Cirsium arvense /L/ Scop. nowadays is popular in all territory of Hungary, it can be found almost on every soil types. Cirsium arvense is one of the most difficulty eradicated weed of the fields, the ruderals, and also the roadsides. On the base of IV. Hungarian Weed Survey 1996-1997, it takes the fifth place in the dominance sequence of the weeds, with 1.8% average covering. In the interest of effective weed control we can know the biological characteristics of the weeds in detail. In our experiments we followed the nutrient uptake and its changing in Cirsium arvense plants. Nitrogen concentration of shoots altered between 1.5-3.6%. We established that plants can uptake potassium in a great quantity. Roots and shoots contained potassium in high concentration between 2.2-5.9%. The maximum of shoot production from the adventitious buds of the roots was in October and the minimum was in April and May.

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The objective of this study was to examine the reaction of 12 Capsicum breeding lines to NTN strain of Potato virus Y (PVY(NTN)) and 16 lines to Obuda pepper virus (ObPV). Inoculated plants were symptomatologically and serologically checked for virus infection. Back inoculation was also carried out to Nicotiana tabacum 'Xanthi-nc' and N. tabacum 'Samsun' as indicator plants. Out of the 12 lines tested four (32.Bogyiszlói, 4/99 F2, 17/99 F2 and VI-61 in.) proved to be resistant (immune) to PVY(NTN). Seven Capsicum lines (9/99 F2, 17/99 F2, V-21 = 28/98 F3, V-28 = 36/98 F3, V-3 = 7/98 F2, V-6 = 13/98 F2, and V-10 = 17/98 F2) showed hypersensitive reaction to ObPV. Other breeding lines were susceptible to ObPV infection. One line (17/99 F2) showed immunity to PVY(NTN) and hypersensitivity to ObPV at the same time, therefore this one is considerably valuable for breeding pepper varieties for multivirus resistance.

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Virus susceptibility of 33 Lycopersicon species and varieties to NTN strain of Potato virus Y (PVY(NTN)) and Tomato mosaic virus (ToMV) were studied. Inoculated plants were tested for infection symptomatologically, serologically and by back inoculation as well. New incompatible and compatible host-virus relations have been determined. All tested plants were susceptible to ToMV. However, Lycopersicon esculentum Mill. convar. parviboccatum Lehm. var. cerasiforme (Dun.) Alef. s.l., L. peruvianum (L.) Mill. and L. hirsutum Humb. et Bonpl. were extreme resistant (immune) to PVY(NTN). Other species were susceptible. Resistant lycopersicon genotypes could be used as sources for virus resistance.

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We have studied the susceptibility or resistance of Solanum capsicastrum Link. et Schauer, S. comatum Sendt., S. dulcamara L., S. luteum Mill., S. malacoxylon Sendt. and S. nigrum L. to three aphid transmissible viruses [alfalfa mosaic alfamovirus (AMV), potato M. carlavirus (PVM) and potato S carlavirus (PVS)]. Out of the species, S. capsicastrum, S. comatum, S. dulcamara, S. malacoxylon and S. nigrum to AMV, S. capsicastrum and S. malacoxylon to PVM and S. capsicastrum, S. luteum and S. nigrum to PVS showed the highest resistance (immunity). Symptoms could not be seen on inoculated plants and the virus could be detected by them neither by serological nor biological tests. Solanum luteum plants were susceptible to AMV. Solanum comatum, S. dulcamara, S. luteum and S. nigrum showed susceptibility to PVM. Solanum comatum and S. dulcamara were susceptible to PVS. Symptoms (necrotic lesions, mosaic and chlorosis) could be seen after inoculation and the absorbance values (DAS-ELISA) exceeded twice that of the healthy control samples during the serological tests.

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