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Rhizomania disease, caused by the Beet necrotic yellow vein virus (BNYVV), is considered as one of the major constraints for sugar beet production, worldwide. As a result of the introgression of major resistance genes (Holly, Rz2) in commercially available sugar beet varieties, the virus has endured strong selection pressure since the 90s'. Understanding the virus response and diversity to sugar beet resistance is a key factor for a sustainable management of only few resistance genes. Here we report rhizomania surveys conducted in a rhizomania hot spot, the Pithiviers area (France) during a 4-year period and complementary to the study of Schirmer et al. (2005). The study aimed at evaluating the intra- and inter-field BNYVV diversity in response to different sources of resistance and over the growing season. To follow rhizomania development over the sugar beet growing season, extensive field samplings combined with field assays were performed in this study. The evolution of the BNYVV diversity was assessed at intra- and inter-field levels, with sugar beet cultivars containing different resistance genes (Rz1, Rz1 + Heterodera schachtii resistance and Rz1Rz2). Intra-field diversity was analyzed at the beginning and the end of the growing season of each field. From more than one thousand field samples, the simultaneous presence of the different A, B and P types of BNYVV was confirmed, with 21 variants identified at positions 67–70 of the p25 tetrad. The first variant, AYHR, was found most commonly followed by SYHG. Numerous mixed infections (9.93% of the samples), mostly of B-type with P-type, have also been evidenced. Different tetrads associated with the A- or B-type were also found with a fifth RNA-genome component known to allow more aggressiveness to BNYVV on sugar beet roots. Cultivars with Rz1+Rz2 resistant genes showed few root symptoms even if the BNYVV titre was quite high according to the BNYVV type present. The virus infectious potential in the soil at the end of the growing season with such cultivars was also lower despite a wider diversity at the BNYVV RNA3 sequence level. Rz1+Rz2 cultivars also exhibited a lower presence of Beet soil-borne virus (BSBV), a P. betae-transmitted Pomovirus. Cultivars with Rz1 and nematode (N) resistance genes cultivated in field infected with nematodes showed lower BNYVV titre than those with Rz1 or Rz1+Rz2 cultivars. Overall, the population structure of BNYVV in France is shown to be different from that previously evidenced in different world areas. Implications for long-term management of the resistance to rhizomania is discussed.

The RNA3 species of the beet necrotic yellow vein virus (BNYVV), a multipartite positive-stranded RNA phytovirus, contains the ‘core’ nucleotide sequence required for its systemic movement in Beta macrocarpa. Within this ‘core’ sequence resides a conserved “coremin” motif of 20 nucleotides that is absolutely essential for long-distance movement. RNA3 undergoes processing steps to yield a noncoding RNA3 (ncRNA3) possessing “coremin” at its 5′ end, a mandatory element for ncRNA3 accumulation. Expression of wild-type (wt) or mutated RNA3 in Saccharomyces cerevisiae allows for the accumulation of ncRNA3 species. Screening of S. cerevisiae ribonuclease mutants identified the 5′-to-3′ exoribonuclease Xrn1 as a key enzyme in RNA3 processing that was recapitulated both in vitro and in insect cell extracts. Xrn1 stalled on ncRNA3-containing RNA substrates in these decay assays in a similar fashion as the flavivirus Xrn1-resistant structure (sfRNA). Substitution of the BNYVV-RNA3 ‘core’ sequence by the sfRNA sequence led to the accumulation of an ncRNA species in yeast in vitro but not in planta and no viral long distance occurred. Interestingly, XRN4 knockdown reduced BNYVV RNA accumulation suggesting a dual role for the ribonuclease in the viral cycle.

Rhizomania disease, caused by the Beet necrotic yellow vein virus (BNYVV), is considered as one of the major constraints for sugar beet production, worldwide. As a result of the introgression of major resistance genes (Holly, Rz2) in commercially available sugar beet varieties, the virus has endured strong selection pressure since the 90s'. Understanding the virus response and diversity to sugar beet resistance is a key factor for a sustainable management of only few resistance genes. Here we report rhizomania surveys conducted in a rhizomania hot spot, the Pithiviers area (France) during a 4-year period and complementary to the study of Schirmer et al. (2005). The study aimed at evaluating the intra- and inter-field BNYVV diversity in response to different sources of resistance and over the growing season. To follow rhizomania development over the sugar beet growing season, extensive field samplings combined with field assays were performed in this study. The evolution of the BNYVV diversity was assessed at intra- and inter-field levels, with sugar beet cultivars containing different resistance genes (Rz1, Rz1 + Heterodera schachtii resistance and Rz1Rz2). Intra-field diversity was analyzed at the beginning and the end of the growing season of each field. From more than one thousand field samples, the simultaneous presence of the different A, B and P types of BNYVV was confirmed, with 21 variants identified at positions 67–70 of the p25 tetrad. The first variant, AYHR, was found most commonly followed by SYHG. Numerous mixed infections (9.93% of the samples), mostly of B-type with P-type, have also been evidenced. Different tetrads associated with the A- or B-type were also found with a fifth RNA-genome component known to allow more aggressiveness to BNYVV on sugar beet roots. Cultivars with Rz1+Rz2 resistant genes showed few root symptoms even if the BNYVV titre was quite high according to the BNYVV type present. The virus infectious potential in the soil at the end of the growing season with such cultivars was also lower despite a wider diversity at the BNYVV RNA3 sequence level. Rz1+Rz2 cultivars also exhibited a lower presence of Beet soil-borne virus (BSBV), a P. betae-transmitted Pomovirus. Cultivars with Rz1 and nematode (N) resistance genes cultivated in field infected with nematodes showed lower BNYVV titre than those with Rz1 or Rz1+Rz2 cultivars. Overall, the population structure of BNYVV in France is shown to be different from that previously evidenced in different world areas. Implications for long-term management of the resistance to rhizomania is discussed.

The plasmodiophorid Polymyxa betae is considered as the only natural transmitting agent of Beet necrotic yellow vein virus (BNYVV), the most devastating agent of sugar beet fields throughout the world. To evaluate for the first time the genetic diversity of P. betae isolated from different autumn and spring sugar beet fields, and also to detect the presence of virus in these isolates, susceptible sugar beet plants (cv. Regina) were grown in soil samples collected from 10 different regions of Iran. P. betae detection was carried out using root microscopic observations, DAS-ELISA, and PCR-based methods. Results showed the presence of plasmodiophorids in all soil samples. Complementary assays also revealed the presence of viruses in soil samples collected from Khorasan Razavi, Fars, Hamadan and Kermanshah regions. The genetic diversity was evaluated through comparing glutathione-S-transferase nucleotide sequences amplified by PCR with the Internal Transcribed Spacers region. Results showed no significant differences in nucleotide sequences between virus-bearing and virus-free isolates of P. betae.

International audience; Systemic movement of beet necrotic yellow vein virus (BNYVV) in Beta macrocarpa depends on viral RNA3, whereas in Nicotiana benthamiana this RNA is dispensable. RNA3 contains a coremin motif of 20 nucleotides essential for the stabilization of noncoding RNA3 (ncRNA3) and for long-distance movement in Beta species. Coremin mutants that are unable to accumulate ncRNA3 also do not achieve systemic movement in Beta species. A mutant virus carrying a mutation in the p14 viral suppressor of RNA silencing (VSR), unable to move long distances, can be complemented with the ncRNA3 in the lesion phenotype, viral RNA accumulation, and systemic spread. Analyses of the BNYVV VSR mechanism of action led to the identification of the RNA-dependent RNA polymerase 6 (RDR6) pathway as a target of the virus VSR and the assignment of a VSR function to the ncRNA3.

International audience; The p25 protein encoded by Beet necrotic yellow vein virus (BNYVV) RNA-3 is a pathogenicity determinant that has been implicated in symptom exacerbation on Chenopodiaceae hosts. Several p25 variants exist within natural isolates and p25 sequence variation may influence the degree of pathogenicity of such BNYVV isolates. Expression of p25 from natural A- and P-type isolates in the background of B-type BNYVV cDNA clones gave symptom discrepancies when compared to B-type p25 expression. Such pathogenicity fluctuation was not due to a different subcellular localization of p25 but was correlated with the nature of the tetrad motif present between amino acid residues 67–70, as well as with the capacity of p25 to self-associate and to activate transcription in a yeast one-hybrid system. Our data suggest that the complete sequence of p25 is required for its functions and the identified sequence variations may contribute to correct folding of the protein.

Large changes introduced in the sugar beet production technology in the Vojvodina Province over last 40 years resulted in changes in the etiology and harmfulness of different agents of sugar beet root diseases. Improvements in cultivation practices reduced the harmfulness of some diseases while increased the harmfulness of others. Some disease agents became obsolete, but others gained importance. New agents of root diseases were found. The most frequent damages, persisting over long periods of time were caused by seedling damping-off, Fusarium root rot, charcoal root rot, parasitic (Rhizomania) and non-parasitic root bearding. The parasitic damping-off caused by several fungal species but most frequently by Phoma betae occurred at the time when multigerm seeds were used in combination with extensive cultural practices. The agents of seedling diseases completely lost their significance as the consequence of switching to fungicide - treated monogerm seeds, earlier planting and improved soil tillage. In the period of intensive use of agricultural chemicals, seedling damping-off occurred frequently due to the phytotoxic action of chemicals (insecticides, herbicides and mineral fertilizers). In some years, frosts caused damping- off of sugar beet seedlings on a large scale in the Vojvodina Province. Poor sugar beet germination and emergence were frequently due to spring droughts. Sometimes they were due to strong winds. The occurrence of Fusarium root rot and charcoal root rot intensified on poor soils. Fusariosis symptoms were exhibited as plant wilting and different forms of root rot. In recent years root tip rot has occurred frequently in the first part of the growing season causing necrosis and dying of plants. Lateral roots tended to proliferate from the healthy tissue, giving the root a bearded appearance similar to Rhizomania. Fusarium oxysporum was the most frequent agent of this fusariosis. F. graminearum, F. equiseti, F. solani have also been identified in recent years as the agent of root rot, but its importance was much lower. Charcoal root rot and plant wilting (Macrophomina phaseolina) have caused extensive damages in sugar beets, especially under the conditions of severe drought and high temperatures in summer. In some years, it was the dominant agent of root rot. Mixed infections caused by fungi from the genera Fusarium and M. phaseolina were encountered frequently. The extent of damage caused by these diseases was reduced by improved pro- duction technology. Rhizomania of sugar beet (caused by beet necrotic yellow vein virus) was identified in Serbia in the 1970s. Results of recent investigations have shown that BNYVV is widespread in Vojvodina, since the virus was found on 36,7% (24,674 ha) of acreages from 67,213 ha of total sugar beet acreages inspected on incidence of BNYVV in the period from 1997 to 2004 year. In the last few years, the occurrence of Rhizoctonia root rot (Rhizoctonia solani) was registered in some localities in Vojvodina.

U radu je provedena usporedba pouzdanosti dvije metode za dokazivanje virusa nekrotičnog žućenja žila šećerne repe (BNYVV): metode mehaničke inokulacije i metode biljaka mamaca. Uspješnost obje metode je provjerena metodom ELISA. U istraživanju je korišteno ukupno pet uzoraka šećerne repe koji su provjereni metodom ELISA na prisutnost navedenog virusa te ukupno pet uzoraka tla na kojem su rasli navedeni uzorci. Metoda biljaka mamaca uz korištenje dvije sorte šećerne repe (Goethe i Clementina) te cikle se pokazala kao vrlo učinkovita u detekciji BNYVV pri čemu je navedeni virus metodom ELISA potvrđen u svim uzorcima dok se metoda mehaničke inokulacije biljaka vrste Chenopodium quinoa pokazala neučinkovita u detekciji virusa te isti metodom ELISA nije potvrđen niti u jednoj od inokuliranih biljaka.

ÖZETYüksek Lisans TeziTRAKYA BÖLGESİ ŞEKER PANCARI ÜRETİM ALANLARINDA BEET NECROTIC YELLOW VEIN VIRUS (BNYVV), BEET WESTERN YELLOWS VIRUS (BWYV) VE BEET YELLOWS VIRUS (BYV) HASTALIKLARININ SAPTANMASI ÜZERİNE ARAŞTIRMALARHarun ÖZDEMİRNamık Kemal ÜniversitesiFen Bilimleri EnstitüsüBitki Koruma Anabilim DalıDanışman: Doç. Dr. Havva İLBAĞITrakya Bölgesi'nin Edirne, Kırklareli ve Tekirdağ illerindeki şeker pancarı üretim alanlarında 2013 yılı üretim döneminde gerçekleştirilen sürvey çalışmalarında, verim kayıplarına neden olan virüs hastalıklarını saptamak amacıyla 126 yaprak örneği toplanmıştır. Şeker pancarı üretim alanlarında yapraklarda sararma, nekroz, mozayik ve şekil bozukluğu simptomları gösteren bu yaprak örneklerinde Beet necrotic yellow vein virus (BNYVV), Beet western yellows virus (BWYV), Beet yellows virus (BYV) hastalıklarını saptamak üzere Double Antibody Sandwich Enzyme-linked Immunosorbent Assay (DAS-ELISA) testi gerçekleştirilmiştir. Test edilen toplam 126 yaprak örneğinden 25 adedinde BNYVV, 6 adedinde BWYV ve 5 adedinde ise BYV bulunduğu saptanmıştır. 8 yaprak örneği BNYVV+BYV, 1 örnek BNYVV+BWYV, 1 örnek BWYV+BYV ile enfekteli iken 14 adet örneğin ise BNYVV+BWYV+BYV ile enfekteli oldukları tespit edilmiştir. DAS-ELISA testi sonucunda Trakya Bölgesi'ndeki illerden alınan 126 adet yaprak örneğinin 60 adedinde tekli ve karışık enfeksiyonlar saptanmıştır. Tek enfeksiyon halinde BNYVV'nin % 19.84, karışık enfeksiyonlar halinde % 38.09 olduğu tespit edilmiştir. BWYV'nin tek enfeksiyon halinde % 4.76, karışık enfeksiyon halinde % 12.69, BYV'nin ise tek enfeksiyon halinde % 3.97, karışık enfeksiyon olarak ise % 18.25 olduğu belirlenmiştir. Söz konusu virüslerin illere göre dağılımının ise Edirne ilinde % 50, Kırklareli ilinde % 41.51, Tekirdağ ilinde ise % 53.33 düzeyinde olduğu saptanmıştır.Anahtar Kelimeler: Şeker Pancarı, BNYVV, BWYV, BYV2014, 42 sayfa ABSTRACTMSc. ThesisINVESTIGATIONS ON SUGAR BEET VIRUS DISEASES CAUSED BY BEET NECROTIC YELLOW VEIN VIRUS (BNYVV), BEET WESTERN YELLOWS VIRUS (BWYV) AND BEET YELLOWS VIRUS (BYV) IN THE SUGAR BEET GROWING AREAS IN THE TRAKYA REGION OF TURKEYHarun ÖZDEMİRNamık Kemal UniversityGraduate School of Natural and Applied SciencesDepartment of Plant ProtectionSupervisor: Assoc. Prof. Dr. Havva İLBAĞIIn order to determine yield reducing beet virus diseases in the sugar beet growing areas of Edirne, Kırklareli and Tekirdağ provinces in the Trakya region of Turkey. 126 symptomatic sugar beet leaf samples were collected in 2013. For the identification of Beet necrotic yellow vein virus (BNYVV), Beet western yellows virus (BNYVV) and Beet yellows virus (BYV) Double Antibody Sandwich Enzyme Linked Immunosorbent Assay (DAS-ELISA) tests were implemented to sugar beet leaf samples which were exhibited yellowing, necrosis, mosaic and leaf distortions. As a result of DAS-ELISA tests 25out of 126 leaf samples were found infected with BNYVV, 6 of the them had BWYV and 5 leaf samples revealed the presence of BYV. Beside these individually infected samples 8 out of 126 leaf samples had BNYVV+BYV, 1 of them infected with the mixture of BNYVV+BWYV, another one of them had BWYV+BYV and 14 out of 126 leaf samples however were found infected with those three viruses as individually and as their mixed infections. Individually BNYVV was found 19.84 %, as mixed it was 38.09 %. In the case of BWYV individually 4.76 % as mixed infection 12.69 % rate of disease were determined. Individually infection of BYV was 3.97 % as the mixed infection rate of this virus was found 18.25 %. Those sugar beet virus infections occurred 50 % in Edirne, 41.51 % in Kırklareli and 53.33 % in Tekirdağ province.Key words: Sugar beet, BNYVV, BWYV, BYV2014, 42 pages 51

Methods for the generation of monoclonal antibodies against plant viruses are limited because current hybridoma techniques do not allow efficient exploitation of the immune repertoire. Moreover, the immunization procedures often lead to a bias towards an immunodominant contaminant in the immunogen preparation and not to the plant virus itself. The selection of six different single-chain antibody variable fragments (scFv) against beet necrotic yellow vein virus from a semi-synthetic human combinatorial antibody library showed the feasibility of the phage display system. No bias towards minor contaminants in the purified virus preparation was observed in ELISA, as all the selected scFvs reacted only with beet necrotic yellow vein virus infected plant homogenates. In addition, two of the isolated beet necrotic yellow vein virus-specific scFvs could be produced in E. coli as a scFv fusion protein with alkaline phosphatase, and were applied in ELISA as specific ready to use antibody-enzyme conjugates. Because of their specificity, these antibodies have potential to be used as reagents in sensitive diagnostic assays for routine testing for beet necrotic yellow vein virus in sugar beets.

Complementary DNA (cDNA) clones corresponding to each of five distinct RNA species of beet necrotic yellow vein (BNYVV) were synthesized and identified. The sizes of each cDNA clone for RNAs 1,2,3,4 and 5 molecules were 3.0, 1.7, 1.8, 1.5 and 1.4 kbp, respectively. cDNA inserts to RNA 2 were covered at a part of the 3'regions, and those of RNAs 3,4 and 5 were almost full-length. The plasmids containing each of cDNA inserts were labeled with digoxigenin by the random priming method. Northern blot hybridization tests showed that individual probes hybridized specially to each of the five RNAs. Good results were obtained with 1 to 10 ng of RNA as a mixture of five RANs, but the probe to RNA 3, RNA 4 or RNA 5 gave a weak signal with hererologous RNAs when more than 10 ng RNA was used. In dot blot hybridization, the limit of detection was about 10 pg RNA, but if a higher content of RNA was spotted, cross reaction occurred using heterologous RNAs. For laboratory and field isolates of BNYVV, each of RNAs 3,4 and 5 was easily detected by Northern blot hybridization in total nucleic acids extracted from Tetragonia expansa leaves inoculated mechanically, but not from roots of sugar-beet plants inoculated by the fungus Polymyxa betae. However, satisfactory results were obtained with partially purified or concentrated preparations from roots. These findings indicate that the digoxigenin-labeled probes are useful for the identification and detection of RNAs contained in field and laboratory isolates of BNYVV., テンサイそう根ウイルス（Beet nectotic yellow vien virus,BNYVV）に含まれる5種類のRNAのcDNAをクローニングした。得られたcDNAクローンのサイズは次の通りであった：RNA－1、3.0kbp；RNA－2、1.7kbp；RNA-3、1.8kbp；RNA－4、1.5kbp；RNA－5、1.4kbp。RNA-1とRNA-2由来のcDNAクローンは、それぞれ全ゲノムの3’末端側45％と35％を占めていた。RNA-3、RNA－4およびRNA－5からのcDNAクローンはほぼ全長であった。各cDNAクローンをジゴキシゲニン標識し、Northern blot hybridization でウイルスRNAの検出条件を検討した結果、試料はホルマリン・ホルムアルデミド変性、プローブのソニケーション、プローブ量は50ng/ml,ホルムアミド存在下の温度は42℃で行うのが最適であった。BNYVVの4～5種のRNAを検出するためには、全RNA量として1～10ngが適当であった。全RNA量が20ng以上では、RNA-3、RNA-4およびRNA-5の間でお互いにわずかに反応が認められた。この原因は、プローブの3’末端にみられる共通配列によることが確かめられた。Dot blot hybridization によるウイルスRNAの検出感度は、10pgであったが、試料の濃度が高くなるにつれて、RNA-3、RNA-4およびRNA-5の間でお互いに反応が認められた。各種BNYVV分離株を用いて、それらに存在するRNA組成とサイズをNorthern blot hybridization により解析したところ、検定植物ツルナ接種葉の場合には、直接全核酸を調整した試料からウイルスRNAの検出が可能であったが、Polymyxa betae 菌で接種されたテンサイの根の場合には、ウイルス濃度に応じて部分純化または濃縮した試料から核酸を調整する必要があった。このような条件下で、ほ場および室内分離株に存在するBNYVV RNA種およびそれらの欠失変異株を確実に検出することができた。

Rhizomania, caused by the Beet necrotic yellow vein virus and vectored by Polymyxa betae, is one of the most damageable diseases of sugar beet. Since the widespread use of resistant cultivars, multiple Rz1 resistance-breaking events have been reported worldwide. Understanding the dynamic of the emergence of resistance breaking isolates and their ability to spread is of the uttermost importance. A field-based strategy was set up to follow the evolution of the disease in the epidemic foci of Pithiviers, in France. With the help of high-throughput PCR-based methods, the wide diversity of the BNYVV populations with high infectious potentials in soils was evidenced, with the presence of mixed viral infections (BNYVV A-, B- and P-pathotype) and the emergence of BNYVV reassortants. Variations according to the sugar beet genotype as well as to the spatial dispersion of the virus strongly suggest micro-evolution of the virus over a single season, as well as the fact that the host plant resistance is able to shape the viral population. The data accumulated over four years provide insights for a sustainable management of the sugar beet resistance. A model for the virus epidemic is proposed. (AGRO 3) -- UCL, 2013

International audience; The RNA-3-encoded p25 protein was previously characterized as one of the major symptom determinants of the Beet necrotic yellow vein virus. Previous analyses reported the influence of the p25 protein in root proliferation phenotype observed in rhizomania disease on infected sugar beets (Beta vulgaris). A transgenic approach was developed, in which the p25 protein was constitutively expressed in Arabidopsis thaliana Columbia (Col-0) ecotype in order to provide new clues as to how the p25 protein might promote alone disease development and symptom expression. Transgenic plants were characterized by Southern blot and independent lines carrying single and multiple copies of the transgene were selected. Mapping of the T-DNA insertion was performed on the monocopy homozygote lines. P25 protein was localized both in the nucleus and in the cytoplasm of epidermal and root cells of transgenic plants. Although A. thaliana was not described as a susceptible host for BNYVV infection, abnormal root branching was observed on p25 protein-expressing A. thaliana plants. Moreover, these transgenic plants were more susceptible than wild-type plants to auxin analog treatment (2,4-D) but more resistant to methyl jasmonate (MeJA), abscisic acid (ABA) and to lesser extend to salicylic acid (SA). Hormonal content assays measuring plant levels of auxin (IAA), jasmonate (JA) and ethylene precursor (ACC) revealed major hormonal changes. Global transcript profiling analyses on roots displayed differential gene expressions that could corroborate root branching phenotype and stress signaling modifications.

Horizontal dispersal of beet necrotic yellow vein virus (BNYVV) by means of viruliferous zoospores ofPolymyxa betae was studied in greenhouse experiments. BNYVV was not detected in roots of sugar beet plants grown in silver sand for 4 weeks at a root-free distance of 5 cm from eitherP. betae- and BNYVV-infected plants or BNYVV-infested soil. Spread of BNYVV from inoculum sources in the field was studied in the absence and presence of tillage practices. Active dispersal in combination with root growth from and towards point sources of inoculum contributed only little to horizontal dispersal of viruliferous inoculum and spread of disease during the season, as determined for one soil type, two different years and in the absence of tillage and tread. In the second beet crop after application of inoculum to whole field plots, more BNYVV-infected plants were detected at 2 m than at 8 m distance from the infested plots in the tillage direction. In the third year, disease incidence at 8 m was high and equivalent to that at 2 m.

Sugar beet plants (cv. Arosa), susceptible to rhizomania, were grown in 144 soil samples taken from sugar beet fields in north and central part of Turkey in 2004. Incidences of Beet necrotic yellow vein virus (BNYVV) and Beet soilborne virus (BSBV) by ELISA and of their vector Polymyxa betae by root staining method were determined in bait plants. Some soil properties such as, texture, pH, organic matter, cation exchange capacity, electrical conductivity, lime (CaCO3) and exchangeable Ca, Mg, K and Na contents were determined. Sand content and pH values of the soils gave significant positive correlations with P. betae (0.177* and 0.164*, respectively). Lime (CaCO3) and exchangeable Mg contents had also significant positive correlations with soil pH. Increasing CaCO3 (0.189*) and exc. Mg (0.235**) content of soils induced BNYVV and BSBV infections respectively, transmitted by P. betae, due to their increasing effects on soil pH., Se cultivaron plantas de remolacha azucarera (cv. Arosa), susceptibles a rhizomania, en 144 muestras de suelo recogidas de campos del norte y centro de Turquía en 2004. Se determinó la incidencia de Beet necrotic yellow vein virus (BNYVV) y Beet soilborne virus (BSBV) por ELISA y de su vector Polymyxa betae por el método de tinción de raíz en plantas cebo. Se determinaron algunas propiedades del suelo tales como textura, pH, materia orgánica, capacidad de intercambio catiónico, conductividad eléctrica, y contenidos en cal (CaCO3), y Ca, Mg, K y Na intercambiables. El contenido en arena y los valores de pH de los suelos presentaron correlaciones positivas con P. betae (0,177* y 0,164*, respectivamente). La cal (CaCO3) y el contenido en Mg intercambiable estuvieron también positivamente correlacionados con el pH del suelo. Contenidos crecientes en CaCO3 (0,189*) y en Mg intercambiable (0,235**) de los suelos indujeron infecciones de BNYVV y BSBV respectivamente, transmitidas por el vector P. betae, debido a su creciente efecto en el pH del suelo.