پديد آورندگان :
سلطاني ايدليكي، جمشيد دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه گياه پزشكي , مهرور، محسن دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه گياه پزشكي , زكي عقل، محمد دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه گياه پزشكي , سازمان تحقيقات آموزش و ترويج كشاورزي - مؤسسه تحقيقات اصلاح و تهيه بذر چغندر قند، كرج , صلاتي، منصور سازمان تحقيقات آموزش و ترويج كشاورزي - مركز تحقيقات و آموزش كشاورزي و منابع طبيعي استان خراسان رضوي - بخش تحقيقات گياه پزشكي، مشهد
چكيده لاتين :
Introduction: Soil-borne sugar beet viruses are responsible for the destructive diseases of sugar beet. They
can cause significant yield losses worldwide. Four of the soil-borne sugar beet viruses consisted of Beet necrotic
yellow vein virus (BNYVV), Beet soil-borne mosaic virus (BSBMV), Beet soil-borne virus (BSBV) and Beet
virus Q (BVQ) are transmitted by the protis Polymyxa betae, a common root infecting parasite which ensures the
long-term persistence of the viruses in the soils and one consisted of Beet black scorch virus (BBSV), is
transmitting by Olpidium brassicae. So far, four out of five aforementioned viruses have been reported (except
for BSBMV) in Iran. BNYVV is the causal agent of the rhizomania disease which has been reported in mixedinfections with BSBV, BVQ and/or BBSV. In previous studies, BSBV, BVQ and BBSV have been found
alongside the BNYVV in some root samples. Nevertheless, up to now, no field has been spotted with black
scorch symptoms of sugar beet leaves. Recently, we observed symptoms of burns on leaves and similar signs of
rhizomania disease in the roots of some sugar beet cultivars in the fields of Khorasan Razavi province. The
purpose of this study was to detect soil-borne viruses of sugar beet and determine some of their molecular
aspects.
Materials and Methods: In this study, sugar beet with bearded roots and black scorching of leaves
symptoms were collected from Mashhad, Fariman, Chenaran, Jolge-Rokh, and Jovein sugar beet fields. Total
RNA was extracted from 100 mg of rootlets using RNeasy Mini Kit (Qiagen-Germany) based on the
manufacturer's protocol. The presence of three viruses of BSBV, BVQ and BNYVV were analyzed by multiplex
reverse transcription-polymerase chain reaction (mRT-PCR). However, For BBSV detection, simplex RT-PCR
was used to detect of the 3′-UTR of the genomic RNA. For the molecular characterization of the BNYVV
isolates, the BNYVV type (A or B) was determined with duplex RT-PCR (dRT-PCR), using A/B-type-specific
primers pairs for the triple gene block (TGB) gene in RNA-2 and the partial p25 gene of the RNA-3 segment of
the virus. RT-PCR was done using the PrimeScript™ Reverse Transcriptase kits and the PrimeSTAR GXL DNA
Polymerase (Takara, Japan). The PCR products were cloned in pGEM®-T Easy Vector (Promega-USA). The
recombinant plasmids were extracted using PrimPrep Plasmid DNA isolation kit (GenetBio-Korea) and then
sequenced (Macrogene, South Korea). Nucleotide sequences data were analyzed using Chromas (version
1.45) and MEGA7 softwares.
Results and Discussion: The results showed that in the three samples with bearded root symptoms
(Mashhad, Jovein, and Jolge-rokh), only BNYVV (A-type) was present and there were no BSBV and BVQ in
the tested samples. In addition, in the two samples (Fariman and Chenaran), none of the three viruses was
detected. The results showed that the two BNYVV isolates had ‘ACHG’ (Mashhad and Jolge-Rokh isolates) or
‘AHHG’ (Jovein isolate) residues in the tetrad position. So that the amino acid cysteine (C) in a68 position was
converted to histidine (H). Although this A-type tetrad has been previously reported by Mehrvar et al. (2009) in
Khorasan Razavi and Northern Khorasan, Semnan, Qazvin, Zanjan, Ilam, Hamedan, and West Azarbaijan
provinces. In this study, BBSV was detected in all samples. In Mashhad, Jolge-rokh, and Jovein samples,
BNYVV was present accompanied by BBSV. However, BBSV was detected alone from Fariman (holding black
scorching of the leaves and vascular necrosis of root symptoms) and Chenaran (black scorching of the leaves)
samples. These results are consistent with the results of other researchers from Spain and the United States who
reported the presence of rhizomnia symptoms in the BBSV infected roots.
Conclusion: While most of the farmers in Khorasan province cultivate resistant cultivars of sugar beet
carrying the Rz1 gene for successive years in a field, the breakdown of the resistance and emerging of new
resistance breaking (RB) variant of the virus have occurred via amino acid changes. However, more research on
BNYVV pathogenicity by the use of additional sources of resistance and alternative disease control majors is
needed to have a suitable conclusion. In addition, the results of this study showed that the presence of both
viruses (BBSV and BNYVV) together could exacerbate the Rhizomania syndrome symptoms while single
infection by BBSV could just cause vascular necrosis in the root and black scorching symptoms of the leaves.
This could be very important in symptoms based diagnosing of the disease and preventing errors in evaluating
the resistance of sugar beet cultivars in the field.
