Purple cone fl ower viruses : species diversity and harmfulness

Viral diseases became an actual problem in medicinal plants cultivation. The number of viruses known to infect purple conefl ower increased signifi cantly in the last years in many countries. However, there is no any review about the viral diseases of this valuable medicinal crop. Therefore, the aim of this article is to summarize the main information about the viruses affecting purple conefl ower plants (Echinacea purpurea L. Moench.). An analysis of the literature data showed that purple conefl ower could be infected by 10 viruses. These viruses belong to the families Bromoviridae, Bunyaviridae, Secoviridae, Potyviridae, Vir ga vi ri dae, and almost all of them are considered to be highly harmful plant viruses. Additionally, four of them (TMV, TSWV, CMV, PVY) are in the top 10 of the most economically important plant viruses in the world and occupy the fi rst places. The data from a few countries show that the viral diseases of purple conefl ower are becoming more severe from year to year. The appearance of new viruses is registered on conefl ower every year that complicates prognosis and risk estimation of epiphytoties in these regions which, for example, were revealed in Bulgaria, Lithuania and Ukraine. This review presents the detailed symptoms of the viral diseases in purple conefl ower, the main properties of each virus and data about their harmful effect on the plant metabolism and on the quality of raw material (the concentration of biologically active substances and heavy metals in plants).


Introduction
Nowadays demand for herbal medicines is constantly increasing.Purple conefl ower (Echinacea purpurea (L.) Moench.) is an important medicinal plant.This plant is used for treating more than 70 disorders in humans and is a component of approximately 300 herbal medicines [1].Besides that, it is also used as ornamental, melliferous and essential oil plant.Purple conefl ower is an herbaceous perennial plant of Asteraceae family.It is native to the eastern and southern USA [2].
This herb is cultivated in the north-western sta tes of America, in western Canada, Australia, New Zealand, southern America, Europe and also was in-troduced in Ukraine.The diffi culty of its cul tivating is connected with the condition requirements for the plant.Unlike the natural phytocenosis, during accommodating to agrocenosis conditions the herbs are becoming more wasted and susceptible to plant pathogens of different etiology.Besides that, purple conefl ower is a perennial plant that causes accumulation of pathogens, including viruses.
Regardless of the value of the purple conefl ower in different areas, there is no review on its viruses all over the world.So, in this article we present a review that summarizes the main information about the viruses affecting purple conefl ower plants all around the world.
There are data about diseases of purple conefl ower caused by 10 viruses (Tabl.1).

Viruses of Bromoviridae family
Alfalfa mosaic virus, AMV.Alfalfa mosaic virus is a member of Alfamovirus genus, Bromoviridae family.AMV has a wide host range.This virus can naturally infect many herbaceous and some woody plant hosts (150 species of 22 families) and is transmissible to over 430 species of 51 dicotyledonous families [25].AMV can cause various mosaics, mottles, and malformations in alfalfa (Medicago sativa), yellowing of lea ves in pea (Pisum sativum), calico and tuber necrosis in potato (Solanum tuberosum), and various symptoms in tobacco (Nicotiana tabacum) [26,27].Sixteen species of aphids, including Myzus persicae, can tran smit AMV in a non-persistent manner [28].AMV can be also transmitted by potato pollen and by seed [29].
In 2008-2009, Alfalfa mosaic virus was detected in Bulgaria in 55.5 % of tested purple conefl ower samples [3,4].AMV caused spotting and dwarfi ng of the purple conefl ower leaves.The virus was detected in co-infection with TMV and CMV.The impact of the disease caused by CMV, AMV and TMV on the conefl ower yield was also determined.Infected herbs had lower weight and number of leaves, racemes and produced seeds half as much.

Cucumber mosaic virus, CMV
Cucumber mosaic virus causes substantial agronomic yield losses in many crops in the world, probably has one of the broadest host range among plant viruses.CMV is a type member of the genus Cu cu mo virus, family Bromoviridae and infects more than 1,000 plant Purple conefl ower viruses: species diversity and harmfulness species from more than 86 families, including monocots and dicots [25].The host range includes different crops and numerous wild plants, which are important for the annual persistence of the virus in the open fi eld.
The earliest report on CMV affecting purple conefl ower was in 1964 in Germany [6].CMV-infected purple conefl ower was revealed in Belarus and reported as a weedy host for the virus [15], New Zealand with the symptoms of yellow mottling on the leaves [7,8], and also in the US, where the disease was accompanied with ringspots and leaf deformation [13].
In 1993, CMV disease of Echinacea purpurea was observed in Japan [9].Conefl ower plants showed mosaic symptoms in the leaves.
Yamamoto et al. studied a host range of an isolate of CMV (39 plant species were inoculated) [9].It was demonstrated that 18 species including Echinacea purpurea, Lycopersicon esculentum, Petunia hybrid, Capsicum annum, Pisum sativum, Vicia faba, Cucumis sativus, Nicotiana tabacum, N. glutinosa were systemically infected by CMV, but the virus could not be readily transmitted to Cucumis sativus.Eighteen species such as: Citrullus lanatus, Cucumis melo, C. melo (makuwa), C. melo (conomon), Cucurbita maxima, C. moschata, C. pepo, Vig na ses quipedalis, Chenopodium quinoa, Che nopodium amaranticolor were locally infected.It was the fi rst report about the viral disease of purple conefl ower in Japan and the authors proposed to name this disease as 'Echinacea mosaic disease' [9].
In Italy, CMV has been detected in the plants of purple conefl ower for years.The disease has the symptoms of yellow mosaic, variegation on the leaves which were often malformed and with bullas.The petals showed contractions, deformations and mottling [10,11].In 2009, CMV-infected plants showed stunting; leaves with yellow mosaics, ring, line patterns and malformations; small fl owers with pale stripes on red petals [12].Mo reover, Italian scientists have studied genetic modifi cations of the CMV isolates, taken from aromatic, offi cinal and ornamental plants in the Northern Italy.They made a sequence analysis of the movement protein gene of CMV isolate from purple conefl ower and its comparison with the isolates from other countries [31].A phylogenetic analysis showed that CMV isolate from Echinacea purpurea from Italy (EU 432180) belonged to the subgroup IA and was genetically closer to the Italian isolate CMV-LAV (EU432182) from Lavandula offi cinalis and Hungarian NS isolate from Nicotiana glutinosa (AJ511990).The comparison of nonsynonymous and synonymous substitutions suggested that 30 % of amino acid sites were under negative selection and only one was under positive selection.Phylogenetic, nucleotide diversity and genetic differentiation analyses suggested that longdistance migration plays a role in the evolution and determination of the genetic structure and diversity of CMV in northern Italy and other regions.
CMV was also revealed in Hungary in mixed infection with PVY, TMV і TSWV [14].
The disease of purple conefl ower with the symptoms of yellow mosaics on the leaves was also revealed in China.On the basis of virion structure, the biological and serological properties were determined that were caused by CMV [16].The nucleotide and amino acid sequence analysis of the RNA 2-1-1 fragments showed the 94.5 and 98.1 % identity with the standard isolates of Fny subgroup as well as 77.7 and 82.5 % identity with the standard isolate Q from the subgroup II [32].
In Bulgaria, 45.5 % of purple conefl ower plants with viral symptoms were determined as infected by CMV [4].The symptoms were light-green spots on the leaves with curly laminas due to the different growth of pale green and dark green areas of the leaves (Fig. 1).
Dikova et al. showed that economically important viruses for the E. purpurea cultivation in Bulgaria are those, transmitted by aphids: AMV and CMV as well as the mechanically transmitted TMV [4].These three viruses were widespread in over 45 % of plants and caused the symptoms of spotting and even of mosaic on the leaves.It is interesting to mention that mixed infection by CMV, AMV and TMV caused   other symptoms -spotting and dwarfed conefl ower leaves (Fig. 2).
Dikova and co-authors revealed that sprouts, containing viruses, grew from the purple conefl ower roots, infected during the fi rst year of twoand three-year old conefl ower plantations showed the highest percentage of infection with spotted plants and dwarfi ng leaves and stems [3,4].They showed that the vector of CMV could be aphids Aphis gossypii Glover (cotton aphid) which were found in the trial fi elds with E. purpurea during April, May and June.These aphids were not observed at later stages of vegetation of E. purpurea plants in July and August.
In 2006-2009, epiphytoty of CMV on fi eld-grown purple conefl ower was registered in Ukraine [17,33].Monitoring of the plantations showed that 75 % of the plants were with the symptoms of viral infection.The most typical symptom was chlorosis on the leaves accompanied by their size reduction (Fig. 3, A).
It is noteworthy that these symptoms were revealed among the herbs of the 1 st year of cultivation as well as among those of the 2 nd -5 th years during both regeneration and blossoming periods.Also rolling, rasp-shape and leaf deformation were revealed on the 2 nd year plants (Fig. 3, B).In limited number of the cases, the plant stunting and the stunting of the root system have been observed (Fig. 3, C).Generally, it was observed that the virus symptoms were getting more pronounced during the last years.
The spherical particles were revealed in the purple conefl ower plants 29.5 ± 0.5 nm in diameter [17,34].The virus identifi cation carried out by ELISA and the study of biological, physical and chemical properties of the virus proved that the plants were infected by CMV [17].It was the fi rst report about infection of purple conefl ower by CMV in Ukraine.
Taking into consideration the data about species diversity of the viruses infecting purple conefl ower in the world and those widely spread in Ukraine, the samples were also tested as to the presence of other viruses.The results of ELISA test indicated that in purple conefl ower there were no antigens of the following viruses: TMV, AMV, TSWV, INSV, TRV, PVY, PVS, PVX, PVM, TAV, ArMV, TuMV, PePMV, WMV-2, and CGMMV [17].

Viruses of Bunyaviridae family
Tomato spotted wilt virus, TSWV, and Impatiens nec rotic spot virus, INSV.TSWV and INSV are the members of genus Tospovirus.Initially INSV was considered to be another isolate of TSWV, but genetic studies proved that they are different virus species [35].Tospoviruses are transmitted in a persistent and propagative manner exclusively by thrips (Thysanopte ra: Thripidae) [36].Trans mis sion can also be achie ved through infected plant sap.INSV and TSWV are mainly defi ned on the basis of their vector spe cifi city, host range and symptoms of disease.
TSWV was reported to have a very broad host range including more than 1100 different species from more than 80 families [37].The TSWV infection is characterized by different symptoms depending on the plant species [38,39].TSWV causes severe diseases in numerous horticultural and agri-cultural crops.TSWV is the second among the top 10 of scientifi cally and economically important plant viruses in the world [40].The distinguishing feature of this virus is an ability to infect many species: from 150announced in 1968 [41] to 650 announced in 1994 [42] and about 1100 plants from more than 80 families -in 2003 [37,43].The number of susceptible plants exposed to the risk to be infected by TSWV is growing nowadays.It can be explained by some features of epidemiology of this virus.There are innumerable infected weeds that serve as reservoirs for primary infection [38].These plant sources perpetuate TSWV as important hosts for thrips vectors and serve as foci for subsequent movement and infection of susceptible crop plants [44].TSWV is transmitted by thrips Frankliniella occidentalis, F. bispi nosa, F. cephalica, F. gemina.F. fusca, F. intonsa, F. schultzei, F. se tosus and Thrips tabaci [25,36].TSWV is also transmitted by grafting; and is not transmitted by contact between plants, by seed and by pollen.
INSV has a narrower host range than TSWV.INSV infects more than 648 species including important horticultural and agricultural crops [25].Its name indicates that the main symptom is necrotic spotting on the leaves.However, it is rather diffi cult to diagnose INSV as the symptoms can vary depending on the host and its age.The symptoms caused by INSV can be easily confused with those of other viruses, fungi and bacteria or nutrition disorders.It has been announced many years ago that fl ower thrips (Frankliniella occidentalis) are the only effective transmitter of INSV [45].Mo re over, INSV can be transmitted by other species Fran kliniella -F.intonsa [46] and F. fusca [47].
In purple conefl ower TSWV was detected in Europe (Lithuania, Bulgaria, Hungary and Ukraine).In Lithuania, TSWV on the purple conefl ower was registered in co-infection with INSV [18].
In 2009-2010, TSWV was also revealed in Bulgaria on the purple conefl ower plants [23].The author described that TSWV caused yellow spotting on the purple conefl ower leaves.TSWV was revea led in one plant with the symptoms on leaves typical for this virus -chlorotic dark red ring spots turning into brown necrotic lesions [4,23].Thripses were found on E. purpurea racemes in single cases.The main species was Frankliniella occidentalis that appeared in May to July.
In 2012, purple conefl ower disease caused by TSWV was revealed in Ukraine [24].The symptoms of the disease were yellow spots, mosaics and leaf deformation during all vegetation phases.Light green mottling on the leaves during budding-initial blossoming (Fig. 4, A, B) turned into yellow mottling, that at the end of blossoming covered practically all lamina (Fig. 4, C).
The virions of the TSWV isolate were studied with the electron microscopy method and were 100 ± ± 20 nm in diameter.
It was also studied whether the plant samples were infected by INSV taking into consideration that in Lithuania purple conefl ower was infected with the complex of TSWV and INSV [18].The ELISA results showed the absence of INSV in the conefl ower plants [24].

Viruses of Potyviridae family
Potato virus Y, PVY.Potato virus Y is a type member of the genus Potyvirus of family Potyviridae.It is common knowledge that this is one of the most widely spread and economically important pathogen with a broad range of susceptible plants from different families.Besides the potato it can infect tobacco, tomato, sweet pepper and many others.Nowadays PVY is the fi fth among top 10 economically and scientifi cally important plant viruses [40].The virus is transmitted by a vector in non-persistent manner (arthropods, insects of order Hemip tera, family Aphi didae), by mechanical inoculation, by grafting.Transmitting by seeds and contact is plausible [25,48].
In 2008, only 3.13 % of purple conefl ower infected by the PVY+ CMV+AMV complex was revealed in Bulgaria.The symptoms were spotting and «dwarfed» leaves [3,4].In Hungary PVY was found in the co-infection with CMV, TMV and TSWV [14].
PVY was also detected in Ukraine in purple conefl ower with the symptoms of leaf curling and deformation [19].The samples of 2 nd and 3 rd years of cultivation were tested positive by RT-PCR.

Viruses of Secoviridae family, Comovirinae subfamily
Broad bean wilt virus 2, BBWV-2.BBWV-2 is a member of Fabavirus genus [49].BBWV-2 spreads in African region, Eurasian region, Middle East, North American region, Pacifi c region, Australia and China.The virus is transmitted by a vector in a nonpersistent manner; an insect; Acyrthosiphon pisum, Aphis craccivora, A. faba, A. nasturtii, Mac ro siphum euphorbiae, M. solanifolii, M. persicae; Aphididae.The virus is transmitted by mechanical inoculation and not transmitted by seeds.
In 2010, BBWV-2 was revealed on purple conefl ower plantations in China.The symptoms were necroses, leaf rolling, yellow mosaics, and mosaics in leaves [5].One plant sample with mosaics symptoms was tested positive in ELISA.Li et al. have studied the range of experimental hosts.Susceptible plant species for Chinese BBWV-2 isolate were Chenopodium quinoa (local lesions in inoculated lea ves, systemic chlorotic mottle in upper leaves, deformation, and apical necrosis), C. amaranticolor (chlo rotic local lesions, systemic mosaic and leaf distortion), Nicotiana benthamiana (systemic mosaics), Gomphrena globosa (local purple spots in inoculated leaves and systemic infection in upper leaves), Tetragonia expansa (local lesions, but no symptoms of systemic infection), Physalis fl oridana (systemic mosaics).No symptoms were observed on Capsicum annum, Datura stramonium, N. glutinosa, or N. tabacum cv.White Burley.Compa rison with the sequences of other BBWV-2 isola tes showed that the isolate from conefl ower (No.JX070674) had approximately 99 % nt identity (98 % amino acid identity) with Chinese BBWV-2 isolate BC from Bupleurum chinense.This was the fi rst report of BBWV-2 infecting purple conefl ower in China and, to our knowledge, in the world.
Tobacco ringspot virus, TRSV and Tomato ringspot virus, ToRSV.TRSV and ToRSV belong to the subgroup A of genus Nepovirus and are serologically related viruses [25].The nepoviruses have a wide host range, including both woody and herbaceous plants.TRSV causes signifi cant disease in gra pe, soybean, tobacco, blueberry and members of Cu-curbitaceae family (melon, cucumber, squash, and pumpkin).Ma ny other hosts infected naturally were found, including apple, pepper, cherry, papaya, various weeds and mint [50].TRSV causes systemic chlorotic or necrotic ringspots, leaf deformation and stunting.The ToRSV host range is very similar to that of To bacco ringspot nepovirus, except that it is much less important for fruit crops than ToRSV.
The nepoviruses are transmitted by the nematode Xiphinema americanum and other closely related Xiphinema spp [51].TRSV is easily transmitted mechanically, by seeds and pollen [52,53].TRSV and ToRSV have been reported in Europe, North Ame rica, Australia, Africa, India, Japan [3] and New Zealand [54], Lithuania [55] and Uk raine.TRSV is included in the list of quarantined pest [56].
Firstly ToRSV on the purple conefl ower plants was revealed in Lithuania in 2000 [22] and TRSV in 2006 [21].In 2003, the mixed infection of ToRSV and TRV was detected [18].In 2008, Echinacea purpurea (L.) Moench exhibiting the symptoms of plant stunting, leaf malformation, various shaped chlorotic spots, ringspots was collected in the Botanical Gar den of Vilnius University.According to the results obtained by the methods of test-plants, electron microscopy, DAS-ELISA, and RT-PCR, the purple conefl ower plants were affected by co-infection of TRSV and TRV [21].

Viruses of Virgaviridae family
Tobacco rattle virus, TRV.Tobacco rattle virus is a type member of Tobravirus genus, Virgaviridae family.For the fi rst time this virus was revealed in 1931 in Germany on tobacco.TRV is transmitted by a vector (nematodes; family Trichodoridae; Paratri chodorus allius, P. anemones, P. christiei, P. nanus, P. pachydermus, P. teres, Trichodorus minor, T. pri mitivus, T. viruliferus).The virus is transmitted by mechanical inoculation, grafting and seeds; not tran smitted by contact between hosts.
Geographically TRV has been found throughout Europe, New Zealand, North America and Ja pan.TRV has one of the widest host ranges among all the plant viruses.Natural infection has been reported in more than 100 plant species [25].About 400 species in more than 50 families can be infected by sap in-oculation [57].TRV has continuously been a significant potato pathogen causing corky ringspots in potato tubers, which renders the crop unmarketable [58].Additionally, infection by TRV may cause a loss of vigor and yield in tomato, tobacco, sugar beet, spinach, artichoke, celery, pepper and lettuce.
In 2003, TRV was detected in the purple conefl ower in co-infection with ToRSV and in 2008 with TRSV in Lithuania [18,20].This is the only report about infecting purple conefl ower plants by TRV in the world.
Tobacco mosaic virus, TMV is the type member of genus Tobamovirus.TMV is thermostable, the thermal inactivation point is 95 C.It is extremely persistent in an external environment.The virus is not transmitted by a vector.Virus is transmitted by mechanical inoculation, grafting, contact between hosts, by seeds (occasionally transmitted through the testa, but not through the embryo), not transmitted by pollen [25].
TMV has a wide host range (more than 350 species), which includes various vegetables (beet, pepper, eggplant, potato, spinach, tomato), agricultural crops (tobacco, beans, grapes, apple-tree), de corative plants (petunia, phloxes, zinnia), annu al and perennial weeds.It is one of the most contagious plant viruses.The sources of infection are plant residues, seeds, and soil in which the virus does not lose viability for over 22 months.The sym ptoms vary depending on the virus strain, species, phase of infection, environmental conditions.A mixed infection of Tobacco mosaic virus with other viruses (Potato virus X, Potato virus Y, Cu cum ber mosaic virus) causes brown wide and narrow stripes on fruits, leaves, stems and petioles which die off in course of time.TMV is distributed in Eurasia, revealed in Argentina, Australia, Germany, France, Hungary, Iceland, India, Italy, Japan, Pe ru, Kenya, Spain, USA, and Great Britain [25].
TMV in purple conefl ower plants was revealed in Hungary in 2006 [14] and in Bulgaria [4], where it was observed in a co-infection with AMV and CMV.TMV caused the mosaics symptoms and spotting and is considered to be one of the most economically important viruses infecting purple conefl ower (Fig. 2).Dikova et al. found that the virus infected conefl ow-er plants were lower, with smaller number of leaves and racemes in comparison with the control plants [4].The differences in the sizes of organs affected the yield.So, the yield of leaf mass (herba) from the virus infected plants was twice to several times lower in comparison with the symptomless samples.It was noted that more than half of the purple conefl ower plants died over a period of three years.Such perishing was due to different factors -viruses, phytoplasma pathogens and environmental conditions (dry soil, high or low temperature).In order to minimize the damage, caused by viruses, the purple conefl ower fi elds should be isolated from the vegetable and fl ower plants [4].
Viruses, presented in Fig. 5, are rod-shaped with distinct axial canal.Morphologically they are similar to the viruses of Virgaviridae family, which includes six genera: Hordeivirus, Furovirus, Pec lu vi rus, Po movirus, Tobamovirus, and Tobravirus.How ever, among mentioned genera, the fi rst four have a very narrow host range.The described viruses can not be considered as tobamoviruses as the length of virions differs substantially.Morpho lo gically they are closer to tobraviruses.Additionally, the infecting purple conefl ower plants by Tobacco rattle virus which belongs to this family was registered in Lithuania [18,20].Tobraviruses are transmitted by the nematodes Trichodorus and Parat richodorus (Trichodoridae), which are widespread in Ukraine [59].However, the results of ELISA tests indicated that this rod-shaped virus is not the TRV (unpublished data).Maybe, purple conefl ower in Ukraine was affected by other members of the genus Tobravirus: Pea early browning virus, PEBV or Pepper ringspot virus, PepRSV.However, testing conefl ower plants on the antigens of PEBV and PepRSV was not conducted.There are the data about infecting atypical plants by hordeiviruses which is known to have a very narrow host range which includes mainly cereals.Beczner et al. noted that in Hungary the member of Hordeivirus genus Lychnis ringspot virus (LRSV-M) infected mint plants (Mentha longifolia Huds) [60].The virus is transmitted mechanically, by seeds and pollen.Taking this into consideration, we should not eliminate the possibility that purple conefl ower can be infected by hordeiviruses in Ukraine.

Effect of plant viruses on the general links of plants metabolism
For today, despite numerous researches devoted to the study of viral diseases of plants, the mechanisms of development of the pathological process remain unexposed and, at the same time, actual for many scientists.Study on the effects, caused by a viral infection, at the level of cells and their compartments as well as at the organism level is important for understanding the mechanisms of co-operation of the virus with a plant.The research of infl uence of viral infection on the basic links of metabolism is of special interest as they provide the plant with plastic and power substances that are necessary for normal development and vital functions.
Many scientists investigate an infl uence of viruses on the photosynthetic apparatus of plants, in fact the level of photosynthesis is one of basic indexes of the plant normal development and productivity, and thus, the plant: resistance to the infections [17,[61][62][63].They revealed a substantial reduction in the concentration of both chlorophylls a and b as well as of carotenoids in the leaves of Lophanthus anisatus, Arctium lappa and Echina cea purpurea under viral infection.The chlorophyll a content in the leaves of virus infected Lophanthus anisatus plants was by 35 % lower, in comparison with the healthy standards.This tendency was observed also at research of concentration of chlorophyll b, that in sick plants diminished three times (by 31.4 % in comparison with the control).The carotenoids concentration diminished by 32 % in the virus infected giant hyssop plants [64].A substantial decline in the photosynthetic pigments content under the action of viral infection was found for the burdock plants too.Concentration of chlorophyll a was less by 69.7 % compared with the control, chlorophyll b -by 73.0 %, sum of carotenoids -by 44.6 %.In leaves of the CMV-infected Echinacea purpurea plants content of chlorophyll a was by 50.5 % lower, than in healthy plants, and content of chlorophyll b and sum of carotenoids -by 68.9 % and 41.3 %, accordingly [61].It is necessary to mark that the most substantial decline in the content of these pigments was revealed in purple conefl ower plants that testify about high harmfulness of the virus.
Viruses can infl uence the metabolism of plants differently, including the content of carbohydrates in leaves.Some viruses have insuffi cient effect on carbohydrates in leaves, whereas others can change both speed of synthesis and speed of their movement in a plant.It was revealed that in leaves of the infected ginseng plants the content of saccharides was higher compared with the healthy plants: monosaccharides -by 26 %, sucrose -by 102 %, sum of sugars -by 57 % [17].One of suggestions of a reason of glucose, fructose and sucrose accumulation in the leaves of plants infected by a virus was the violation of their outfl ow from phloem that conduces to the development of gummosis.Later Watson M.A. and Watson D.J. made a conclusion that the carbohydrates accumulation in leaves of the sugar beet staggered by the Beet yellow virus is conditioned not by blocking the carbohydrates outfl ow from leaves but by the infl uence of the virus on the cells of leaf cells and, maybe, related to the changes in the activity of the enzyme systems that control the interconversion of different forms of carbohydrates [65].It was shown that viral infection conduces to the increase in quantitative content of carbohydrates in leaves and stems of ginseng plants (Panax ginseng C.A. Meyer): mo nosaccharides -on 26 %, sucrose -on 102 %, sum of saccharides -on 57 % in comparison with the uninfected plants [17].Unlike ginseng, in purple conefl ower plants infected with CMV there was registered decline of content of carbohydrates -monosaccharides -by 58.8 %, sum of saccharides -by 7.7 % [17].Such controversial data on the carbohydrates concentration for these two herbs (conefl ower, ginseng) at a viral infection can be explained by the fact that ginseng was infected by a less virulent virus, than culture of Echinacea purpurea.Probably, in the last case a tendency to the accumulation of sugars is counterbalanced by more active infl uence of viruses on the photosynthetic apparatus of a plant.
Danger and harmfulness of viral diseases increases due to some factors.Firstly, a viral infection negatively affects a height and development of plants, represses the process of forming productive stems and reproductive organs.Secondly, a viral disease makes weakened plants more vulnerable to other pathogens, in particular, by fungi that cause the root rot.Thirdly, a viral infection often passes and spread by vectors, especially by insects, that is a diffi cult and ecologically dangerous challenge.

Effect of plant viruses on the raw material quality
Except a signifi cant effect of viruses on the yield of purple conefl ower and other medicinal plants [4,17], it was proved that these pathogens reduce the content of biologically active substances in medicinal plants.In Italy, virologists showed that CMV reduced the content of some lipophilic compounds in the purple conefl ower plants [10,11,66].The infected materials from Echinacea purpurea afforded a lower oil content and signifi cant quantitative variations in the oil composition when the plants were infected by CMV [67].It was shown that the CMV infection led to a Fig. 5. Rod-shaped virions from Echinacea purpurea cultivated in Ukraine [19,61] decrease in the concentration of hydrocinnamic acids sum, caftaric and cichoric acids sum in conefl ower plants, sometimes to the level below the norms regulated by the State Pharmacopoeia [61,68,69].The polysaccharides content signifi cantly reduced, too [17,69].Pellati with colleagues have studied the content of the secondary metabolites, such as coffee acid derivatives, alcamides and essential oil in purple conefl ower affected by CMV and phytoplasma 16SrIX-C [12].It was noted, that in the plants infected by both pathogens, the concentration of cichoric acid substantially diminished.Viral infection reduces the content of alkamides and some components of essential oil [12].Regarding the main alkamide, dodeca-2E,4E,8Z,10E / Z-tet rae no ic acid isobutylamide, a signifi cant decrease in the content of this secondary metabolite was observed in virus-infected plants in comparison with healthy plants, whereas in the phytoplasma-infected sample the variation of this secondary metabolite was not appreciable.
Indisputable negative CMV infl uence on the quality of raw material was also revealed for some other medicinal plants.For example, it was shown that the CMV infection reduced signifi cantly the quantitative yield of essential oil in Agastache anethiodora and caused changes in the relative composition of the main components: pulegone, menthone, iso-menthone, methyl chavicole and limonene [70].
Negative infl uence on the raw material quality is also shown for some other viruses.It was discovered that AMV reduces the essential oil secretion in the lavender plants [71], Peppermint stunt virus -in the mint plants [72] and BBWV-1 reduces quantitative and qualitative content of essential oil in the Thymus vulgaris [73] and Salvia sclarea plants [74,75].A decrease of the basic BAS in the infected plants is discovered also for ginseng (Panax ginseng C.A. Meyer).It was shown that the content of triterpene glycosides (saponins) in the roots of infected ginseng was 5.6 %, i.e. by 2.0 % less than in the healthy plants [17].Although such raw material remains suitable for pharmacology, however, such substantial worsening of the raw material quality can have catastrophic consequences taking into account diffi culty of cultivating this crop in Ukraine.
Except the infl uence of viruses on therapeutically active substances in the plants it was shown that these pathogens worsened the quality of raw material for drug production.So, upon the action of viral infection it was revealed the accumulation of some heavy metals in medicinal plants in amo unts which exceed maximum allowable concentrations (MAC) in food products.It is necessary to notice that the content of hightoxic elements (As, V, Sb, Cr, Fe) in the TSWVinfected purple conefl ower plants exceeded MAC in 1.2, 7, 2.3, 2.5 and 3.4 times respectively, unlike the healthy plants, the concentration of these metals [in which] was within the limits of norm [24,76].
In the virus infected Lophanthus anisatus plants the concentration of Pb, As, Cu, Zn, V, Ni, Fe and Al exceeded MAC in 1.1, 4.9, 1.7, 3.5, 8.4, 5.8, 7.3, 13.2 times respectively [77].There is no clear information about the passing of heavy metals to the medical forms.That is why viruses can cause a serious problems in the production of high-quality me dical raw material from infected medicinal plants.

Discussion
The review of world scientifi c literature concerning viruses, which infect purple conefl ower crops in different countries, showed that almost all of them are considered to be highly harmful and economically important plant viruses.Additionally, four of them (TMV, TSWV, CMV, PVY) occupy the fi rst places in top 10 of the most economically important plant viruses in the world [40].Such prevalence and harmfulness of these viruses are explained by a wide range of susceptible host plants, wild plants-reservoirs of the infection, and a variety of vector species.
Thus, the analysis of literature showed that all viruses, registered on purple conefl ower, are po ly phagous.Additionally, the number of viruses known to infect purple conefl ower has increased signifi cantly in the last years.Every year new viruses appear in the same agrocoenosis, that was revealed, for example, in Bulgaria, Lithuania and Ukraine [4,17,18,21,22,24,34,62,69].In fact, it complicates the prognosis and risk estimation of epiphytoties emergence in these regions.
Detection and circulation of such harmful viruses on commercial plantations of purple conefl ower re-Purple conefl ower viruses: species diversity and harmfulness quire permanent virological inspections.Cultivation of medicinal plants needs the safety management.In case with medicinal plants using of chemical substances against viruses and their vectors is unacceptable.That is why well-timed detection of plant viruses and information about symptoms of disease, main properties of these pathogens is almost the only method of the prevention of viral infections.Strict control, well-timed diagnostics and disease management of medicinal plants must be applied by the establishments cultivating them.It would reduce the risk of viruses migration into new environments with new vectors that could lead to serious diseases not only of purple conefl ower, but also other horticultural or ornamental crops.
A signifi cant reduces of the BAS and accumulation of toxic metals in different medicinal plants under viral infection have been shown in many countries.Today one of the general principles of the modern phytotherapy is medicines safety.That is why much attention of WHO and national Pharmacopoeias is paid to the control of pollution of medicinal raw materials with pesticides, radionuclides, heavy metals, mycotoxins.So, we think that the information about such harmfulness of plant viruses must attract an attention of the drugs producers, creators of the pha rmacopoeia papers, state standards and specifications which regulate the quality of medicinal raw material.Virus detection should be included to the worksheets of medicinal crops and to the State Pharmacopoeias as one of key principles for obtaining high yield and high-quality raw material.

Fig. 3 .
Fig.3.Echinacea purpurea infected by CMV in Ukraine: on each photo at the left -healthy plant, at the right -virus infected plant[17,33]