Date: May 16, 2007

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[1] 1st Report of _Beet soil-borne virus_ , sugar beet - China
[2] 1st Identification of _Beet western yellows virus_ , sugarbeet & lettuce - China
[3] 1st Report of _Cucurbit aphid-borne yellows virus_ , 9 cucurbitaceous species - China

[1] 1st Report of Beet soil-borne virus, sugar beet - China
Date: May 2007
Source: British Society for Plant Pathology, New Disease Reports (NDR) [edited] <http://www.bspp.org.uk/ndr/july2007/2007-33.asp>

_Beet soil-borne virus_ (BSBV) and _Beet virus Q_ (BVQ) are 2 members of the genus _Pomovirus_ that are transmitted by _Polymyxa betae_. BVQ and BSBV are commonly found in fields where _Beet necrotic yellow vein virus_ (BNYVV), the causal agent of rhizomania disease, is present (Henry et al.
1986; Koenig et al. 1998; Meunier et al. 2003). During the growing season of 2006, 26 roots of sugar beet exhibiting moderate to severe symptoms of rhizomania were collected from 3 fields located in Inner Mongolia and Xinjiang Provinces for a survey to determine whether BSBV and BVQ were present in China. Viral RNA was extracted from partially purified viruses of beet roots as described by Han et al. (2000) and tested by RT-PCR [reverse transcription - polymerase chain reaction] using 3 specific primer sets and designed to amplify coat protein genes for BSBV, BVQ and BNYVV respectively.

Of the 26 beet samples, 15 gave positive reactions for BSBV, 21 for BNYVV and 14 for both BSBV and BNYVV. BVQ was not detected in any sugar beet sample tested. Subsequently, three RT-PCR products amplified in sugar beet samples collected from different locations with the primers specific to BSBV were cloned and sequenced. Sequence analysis revealed that these submitted sequences shared nucleotide identity of 98-99 percent with the German BSBV isolate. The partially purified viruses from infected sugar beet root were used for mechanical inoculation of _Chenopodium quinoa_ and _C. amaranticolor_, and local lesions were observed on inoculated leaves.
Furthermore, BSBV was also confirmed by RT-PCR (as described above) in the local lesions that appeared approximately 5 days after mechanical inoculation.

Combined, the RT-PCR detection, nucleotide sequences and symptoms on inoculated host plants confirm the presence of BSBV in Inner Mongolia and Xinjiang. To our knowledge, this is the 1st report of the occurrence of BSBV in China.

(Byline: Bin Wang et al., NDR vol 15, Feb - July 2007,
<Hanchenggui@cau.edu.cn>)

[2] 1st Identification of _Beet western yellows virus_ , sugarbeet & lettuce - China
Date: May 2007
Source: British Society for Plant Pathology, New Disease Reports (NDR) [edited] <http://www.bspp.org.uk/ndr/july2007/2007-16.asp>

In China, yellowing disease of sugar beet has been reported previously, with _Beet yellows virus_ (BYV; genus _Closterovirus_) regarded as the viral agent (Liu et al., 1981). During a survey in September 2006, the incidence of diseased sugar beet showing yellowing symptoms ranged from 5 percent to 30 percent. The symptoms observed were mainly yellowing, developing mostly in the interveinal tissue of old- and middle-aged leaves (Figure 1). These symptoms were similar to those reported previously for yellowing disease caused by poleroviruses (_Beet western yellows virus_, BWYV; _Beet mild yellowing virus_, BMYV; _Beet chlorosis virus_, BChV) in other countries (Hauser et al., 2000; Stevens et al., 2005).

To identify the viruses involved, 64 samples of sugar beet were collected from fields in different provinces (Inner Mongolia, Gansu, Beijing, Hebei, Jilin and Heilongjiang). Total RNA was extracted from leaf tissue and tested by RT-PCR using a universal polerovirus primer pair and BYV-specific primers. Amplification products of the expected size for a polerovirus (ca. 1100 bp) were obtained in 41 samples, whereas BYV was not detected in any sample tested. Five of these RT-PCR products were selected
(2 from Inner Mongolia, and 2 from Gansu, 1 from Beijing), cloned and sequenced. Comparisons showed that these sequences shared between 88-91 percent nucleotide identity with BWYV (USA isolate), while sharing only 73-75% identity with a French BMYV isolate, and approximately 70 percent identity with BChV. In addition, spherical particles measuring 26 nm in diameter were also observed in some samples by electron microscopy.

In addition to the sugar beet samples, 4 samples of diseased lettuce were also collected from Beijing. These showed yellowing symptoms and were tested positive by RT-PCR with the polerovirus primers. One sample was sequenced. Sequence analysis revealed that it shared between 88-98 percent sequence identity with BWYV, including the Chinese isolates from sugar beet described above.

Based on these data, BWYV was confirmed as a causal agent of yellowing disease of sugar beet and lettuce in Northern China. To our knowledge, this is the 1st definitive identification of BWYV in China.

Figure 1: Yellowing symptoms on sugar beet in Gansu Province, caused by _Beet western yellows virus_ <http://www.bspp.org.uk/ndr/july2007/2007-16-1a.jpg> [field view] <http://www.bspp.org.uk/ndr/july2007/2007-16-1b.jpg> [closeup]

(Byline: H.Y. Xiang et al., NDR vol 15, Feb - July 2007,
<hanchenggui@cau.edu.cn>)