First Report of Strawberry Root Rot Caused by Fusarium falciforme in China.

Root rot caused by Fusarium spp. is a destructive disease affecting agricultural regions worldwide. Strawberries (Fragaria × ananassa Duch.) are an economically important crop in China. In March 2023, root rot was observed in strawberries grown in Jinan, Shandong Province, China. Symptoms included leaf wilt, necrotic roots, and plant death (Figure 1). Four strawberry samples (two symptomatic and two asymptomatic) were collected from ~2-acre fields where the disease incidence rate ranged from 2 to 3%. Tissue pieces (5 mm × 5 mm × 5 mm) from two healthy and two diseased strawberry root tissues were surface-disinfected with 75% ethanol for 3 min, treated with 10% sodium hypochlorite for 5 min, and washed three times with sterile water. These pieces were cultured for 5 days at 28°C on potato dextrose agar (PDA) containing 200 mg/L timentin. Typical Fusarium spp. like growth was observed on plates with the two symptomatic samples. Two representative fungal isolates (CM1 and CM2) with similar morphological characteristics were purified using the single-spore method (Figure 1). CM1 showed an average growth rate of 5 mm/d in PDA and comprised of several white-to-cream aerial mycelia after 5 d. After cultivation in carnation leaf agar medium for 7 d, falciform macroconidia, with blunt apical cells and slightly hooked basal cells comprising 3 to 4 septa of varying sizes (20 to 39)×(3.6 to 6.7 µm) were observed (n=50) (Figure 1). The chlamydospores were spherical, terminal or intercalary, solitary or chain-forming, and 3.1-10.5 µm in diameter (Figure 1). The microconidia on PDA were (5.8 to 13.6)× (2.5 to 3.3) µm in size (n=50). These morphological characteristics are consistent with previous descriptions of the Fusarium solani species complex (FSSC). DNA was extracted using the CTAB method (Stenglein and Balatti 2006). The internal transcribed spacer (ITS), translation elongation factor 1-α gene (tef1), RNA polymerase II largest subunit (rpb1), and RNA polymerase II second largest subunit (rpb2) were amplified and sequenced using specific primers (O'Donnell et al. 2010). The ITS (OR526528, OR526529), tef1 (OR536947, OR536948), rpb1 (OR536949, OR536950), and rpb2 (OR536951, OR536952) sequences of the CM1 and CM2 isolates were uploaded to the NCBI database. BLASTn analysis revealed that the ITS, tef1, rpb1, and rpb2 sequences were 99.1-100% identical to those of the Fusarium falciforme reference strains NRRL 54989 and NRRL 54978. A phylogenetic tree based on the ITS, tef1, rpb1, and rpb2 sequences was generated using MEGA v.11 via the maximum-likelihood method (Tamura et al. 2021). CM1 clustered with the Fusarium falciforme reference strains NRRL 54989 and NRRL 54978 and belonged to the FSSC based on its morphological and molecular characteristics (Figure 2). To test for pathogenicity, the roots of nine 3-month-old healthy strawberry (cv. Akihime) plants were exposed to conidial suspensions (1×108 spores/mL) of the CM1 isolate. Another nine root samples were treated with sterile water and used as controls. All strawberry plants were maintained in a growth chamber under a 12/12 h light/dark cycle at 28°C and 90% relative humidity and the experiment was repeated three times. After one month, the inoculated plants had withered and died, and the pith became dark red (similar to field plants) (Figure 1). The fungi isolated from the experimental plants were confirmed as F. falciforme using morphological and sequence analyses. F. falciforme causes root rot in several species including Nicotiana tabacum (Qiu et al. 2023) and Weigela florida (Shen et al. 2020); however, this study is the first to report root rot caused by F. falciforme in strawberries in China. Overall, F. falciforme infection poses a threat to strawberry production and breeding.

Characterisation of a Novel Insect-Specific Virus Discovered in Rice Thrips, Haplothrips aculeatus.

Insects constitute the largest proportion of animals on Earth and act as significant reservoirs and vectors in disease transmission. Rice thrips (Haplothrips aculeatus, family Phlaeothripidae) are one of the most common pests in agriculture. In this study, the full genome sequence of a novel Ollusvirus, provisionally named "Rice thrips ollusvirus 1" (RTOV1), was elucidated using transcriptome sequencing and the rapid amplification of cDNA ends (RACE). A homology search and phylogenetic tree analysis revealed that the newly identified virus is a member of the family Aliusviridae (order Jingchuvirales). The genome of RTOV1 contains four predicted open reading frames (ORFs), including a polymerase protein (L, 7590 nt), a glycoprotein (G, 4206 nt), a nucleocapsid protein (N, 2415 nt) and a small protein of unknown function (291 nt). All of the ORFs are encoded by the complementary genome, suggesting that the virus is a negative-stranded RNA virus. Phylogenetic analysis using polymerase sequences suggested that RTOV1 was closely related to ollusvirus 1. Deep small RNA sequencing analysis reveals a significant accumulation of small RNAs derived from RTOV1, indicating that the virus replicated in the insect. According to our understanding, this is the first report of an Ollusvirus identified in a member of the insect family Phlaeothripidae. The characterisation and discovery of RTOV1 is a significant contribution to the understanding of Ollusvirus diversity in insects.

First Report of Cucumber Green Mottle Mosaic Virus Infecting Zucchini (Cucurbita pepo) and Wax Gourd (Benincasa hispida) in China.

Cucumber green mottle mosaic virus (CGMMV) was first discovered in China in 2003 and caused an epidemic in 2005. In China, the virus has been reported in gourd crops including watermelons, cucumbers, melons, etc (Sui et al. 2019). In Shandong Province, China from September 2014 to 2017, approximately 30% of zucchini (Cucurbita pepo) and wax gourd (Benincasa hispida) plants in commercial cucurbit fields, the two most important cash crops, exhibited chlorosis, mosaic, and mottling symptoms suspected to be caused by a tobamovirus. To identify the causative pathogens, ten zucchini and 15 wax gourd samples were collected from the commercial cucurbit fields. Total RNA was extracted and all samples were tested using reverse transcription PCR (RT-PCR) with TobamodF/TobamodR and TobamodF2/TobamodR2 (Li et al. 2018a). Five common Cucurbitaceae viruses were also tested: cucumber mosaic virus, papaya ringspot virus, squash mosaic virus, watermelon mosaic virus, and zucchini yellow mosaic virus (Ali et al. 2012). All samples generated positive results using tobamovirus generic primers but were negative for the five common Cucurbitaceae viruses. Amplification products (880 bp) from all samples were inserted into pMD19-T and recombinant clones were selected for Sanger sequencing. The results showed that zucchini green mottle mosaic virus, CGMMV, and tobacco mosaic virus (TMV) were detected in zucchini samples. CGMMV and TMV were detected in the wax gourd samples. To confirm the presence of these viruses, RT-PCR was performed using specific primer pairs, including CGMMV-cpf/CGMMV-cpr (Chen et al. 2006), ZG-F/ZG-R (Li et al. 2018b), and TMV-CP-F/TMV-CP-R (Srivastava et al. 2015). CGMMV was detected in all samples, with four zucchini and nine wax gourds only containing CGMMV. Zucchini (n=4; CGZ1-CGZ4) and wax gourd (n=4; CGWX1-CGWX4) isolates were cloned into pMD19-T and sequenced bidirectionally. The BLASTn results confirmed the presence of CGMMV, and the sequencing results were processed using DNAMAN Version (Lynnon Biosoft, San Ramon, CA, USA) and submitted to the GenBank database (https://www.ncbi.nlm.nih.gov/). A phylogenetic tree based on the CGMMV coat protein (CP) was constructed using CGZ1-CGZ4 (OP779762-OP779765), CGWX1-CGWX4 (OP779766-OP779769), and representative CGMMV sequences from GenBank. Sequence analysis of the CP demonstrated that CGMMV-zucchini and -wax gourd isolates belonged to an independent branch of the Chinese muskmelon AH-FT197 isolate (KU175639) and had 100% identity with the AH-FT197 isolate. To confirm their infectivity, leaf sap extract of CGZ4 and CGWX4 in phosphate buffer (0.1 M, pH 7.0) was mechanically inoculated on leaves of virus-free zucchini seedlings (Cucurbita pepo cv. Zaoqingyidai, 4-leaf-stage, n = 10) or virus-free wax gourd seedlings (Benincasa hispida cv. Tiezhu 2, n = 10). Ten days after inoculation, all plants exhibited symptoms (systemic chlorosis, mosaic, and mottling) similar to those of diseased plants in the field. Control seedlings inoculated with phosphate buffer remained symptomless. RT-PCR analysis using the CGMMV-cpf/CGMMV-cpr primer confirmed that all ten zucchini or wax gourd seedlings were infected with CGMMV, and all the control plants were free from CGMMV. To the best of our knowledge, this is the first report on zucchini and wax gourd as natural hosts for CGMMV in China. CGMMV is a highly contagious seed-borne virus and further attention should be paid to its spread in cucurbit crops.

First Report of Fruit Rot Caused by Fusarium luffae in Cherry Tomato in China.

Tomato (Solanum lycopersicum L.) is a fruit of great economic value that is grown worldwide. In November 2022, fruit rot symptoms were observed in cherry tomatoes (cv. Qianxi) in Jinan City of Shandong Province, China. Six cherry tomato samples (four symptomatic and two asymptomatic) were collected from commercial fields (approximately 1.2 ha) where the incidence of the disease ranged from 5 to 10%. The core and surface of the infected fruit were colonized and covered with white mycelia. Tissue pieces (5 mm × 5 mm) from the junction of healthy and diseased samples were surface-disinfected with 75% ethanol for 3 min, followed by 10% sodium hypochlorite for 5 min, and washed three times with sterile water. Tissue pieces were cultured on potato dextrose agar (PDA containing 200 mg/L timentin) at 28°C for five days. Four fungal isolates with similar morphological characteristics were obtained from each sample. Two representative isolates were collected and purified using the single-spore method. After five days on PDA at 28°C, FL1 and FL2 colonies showed abundant white to cream colored aerial mycelia with an average growth rate of 5 mm/day. On carnation leaf agar, FL1 was characterized by falcate macroconidia with pronounced dorsiventral curvature containing three to eight tapered apical cells and foot-shaped basal cells ranging in size from 25 to 74 µm × 3.6 to 6.8 µm (n=50). Microconidia and chlamydospores were not observed. These morphological characteristics were consistent with the description of F. luffae (Wang et al. 2019). DNA was extracted using the CTAB method. The nucleotide sequences of the translation elongation factor 1-α gene (TEF1) and the second largest RNA polymerase II subunit (RPB2) were amplified using specific primers EF1/EF2 and RPB2F/R, respectively (O'Donnell et al. 1998, 2010). FL1 and FL2 sequences were deposited in GenBank (TEF1: OQ427345 and OQ427346, RPB2: OQ427347 and OQ427348). Polyphasic identification indicated 100% similarity of FL1 and FL2 to F. luffae. A combined dataset of TEF1 and RPB2 was aligned using MAFFT v.7, and phylogenetic analysis was performed in MEGA v.7.0 using the maximum likelihood method. The cherry tomato isolates (FL1 and FL2) clustered together with the F. luffae reference strain NRRL31167 (100% bootstrap) and were identified on a morphological and molecular basis as F. luffae belonging to the Fusarium incarnatum-equiseti species complex. F. luffae was the only pathogen recovered from the infected fruit. To test for pathogenicity, healthy cherry tomato fruit were inoculated in a greenhouse (28°C, 12/12 h light/dark cycle, 90% relative humidity), six by wounded inoculation and six by nonwounded inoculation) with 10 µL conidial suspensions of isolate FL1 at 1 × 106 conidia/mL. Six wounded-treated cherry tomato fruit were used for the control. All cherry tomatoes were kept in a growth chamber at 28℃ with 90% relative humidity. After seven days, the inside of the wound inoculated fruit began to rot, expanding toward the surface and producing white mycelia. Two diseased cherry tomatoes were randomly selected for tissue isolation and F. luffae was re-isolated showing the same morphology as the FL1 isolate, thus fulfilling Koch's postulates. The nonwounded inoculated fruits and control cherry tomatoes remained asymptomatic with no pathogens recovered. This indicates that the wound is an important way for F. luffae to invade tomato, and fruit rot is caused by F. luffae's infection of tomato. To the best of our knowledge, F. luffae has caused fruit rot in muskmelon (Zhang et al. 2022), but this is the first report of fruit rot disease in cherry tomatoes caused by F. luffae in China. Since cherry tomatoes are an important commercial crop in China, F. luffae infection has the potential to pose a threat to the industry.

Selection and Validation of Reference Genes in Virus-Infected Sweet Potato Plants.

Quantitative real-time PCR (qRT-PCR) in sweet potatoes requires accurate data normalization; however, there are insufficient studies on appropriate reference genes for gene expression analysis. We examined variations in the expression of eight candidate reference genes in the leaf and root tissues of sweet potatoes (eight nonvirus-infected or eight virus-infected samples). Parallel analyses with geNorm, NormFinder, and Best-Keeper show that different viral infections and origin tissues affect the expression levels of these genes. Based on the results of the evaluation of the three software, the adenosine diphosphate-ribosylation factor is suitable for nonvirus or virus-infected sweet potato leaves. Cyclophilin and ubiquitin extension proteins are suitable for nonvirus-infected sweet potato leaves. Phospholipase D1 alpha is suitable for virus-infected sweet potato leaves. Actin is suitable for roots of nonvirus-infected sweet potatoes. Glyceraldehyde-3-phosphate dehydrogenase is suitable for virus-infected sweet potato roots. The research provides appropriate reference genes for further analysis in leaf and root samples of viruses in sweet potatoes.

Dietary methionine restriction alleviates oxidative stress and inflammatory responses in lipopolysaccharide-challenged broilers at early age.

In this study, we investigated the effect of dietary methionine restriction (MR) on the antioxidant function and inflammatory responses in lipopolysaccharide (LPS)-challenged broilers reared at high stocking density. A total of 504 one-day-old male Arbor Acre broiler chickens were randomly divided into four treatments: 1) CON group, broilers fed a basal diet; 2) LPS group, LPS-challenged broilers fed a basal diet; 3) MR1 group, LPS-challenged broilers fed a methionine-restricted diet (0.3% methionine); and 4) MR2 group, LPS-challenged broilers fed a methionine-restricted diet (0.4% methionine). LPS-challenged broilers were intraperitoneally injected with 1 mg/kg body weight (BW) of LPS at 17, 19, and 21 days of age, whereas the CON group was injected with sterile saline. The results showed that: LPS significantly increased the liver histopathological score (p < 0.05); LPS significantly decreased the serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activity at 3 h after injection (p < 0.05); the LPS group had a higher content of Interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α (TNF)-α, but a lower content of IL-10 than the CON group in serum (p < 0.05). Compared with the LPS group, the MR1 diet increased catalase (CAT), SOD, and T-AOC, and the MR2 diet increased SOD and T-AOC at 3 h after injection in serum (p < 0.05). Only MR2 group displayed a significantly decreased liver histopathological score (p < 0.05) at 3 h, while MR1 and MR2 groups did so at 8 h. Both MR diets significantly decreased serum LPS, CORT, IL-1ß, IL-6, and TNF-α contents, but increased IL-10 content (p < 0.05). Moreover, the MR1 group displayed significantly increased expression of nuclear factor erythroid 2-related factor 2 (Nrf2), CAT, and GSH-Px at 3 h; the MR2 group had a higher expression of Kelch-like ECH-associated protein 1 (Keap1), SOD, and GSH-Px at 8 h (p < 0.05). In summary, MR can improve antioxidant capacity, immunological stress, and liver health in LPS-challenged broilers. The MR1 and MR2 groups experienced similar effects on relieving stress; however, MR1 alleviated oxidative stress more rapidly. It is suggested that precise regulation of methionine levels in poultry with stress may improve the immunity of broilers, reduce feed production costs, and increase production efficiency in the poultry industry.

Transcriptional profiling reveals a critical role of GmFT2a in soybean staygreen syndrome caused by the pest Riptortus pedestris.

Soybean staygreen syndrome, characterized by delayed leaf and stem senescence, abnormal pods, and aborted seeds, has recently become a serious and prominent problem in soybean production. Although the pest Riptortus pedestris has received increasing attention as the possible cause of staygreen syndrome, the mechanism remains unknown. Here, we clarify that direct feeding by R. pedestris, not transmission of a pathogen by this pest, is the primary cause of typical soybean staygreen syndrome and that critical feeding damage occurs at the early pod stage. Transcriptome profiling of soybean indicated that many signal transduction pathways, including photoperiod, hormone, defense response, and photosynthesis, respond to R. pedestris infestation. Importantly, we discovered that members of the FLOWERING LOCUS T (FT) gene family were suppressed by R. pedestris infestation, and overexpression of floral inducer GmFT2a attenuates staygreen symptoms by mediating soybean defense response and photosynthesis. Together, our findings systematically illustrate the association between pest infestation and soybean staygreen syndrome and provide the basis for establishing a targeted soybean pest prevention and control system.

Dietary Supplemental Chromium Yeast Improved the Antioxidant Capacity, Immunity and Liver Health in Broilers under High Stocking Density.

This study was conducted to investigate the effects of different levels of yeast chromium on growth performance, organ index, antioxidant capacity, immune performance and liver health of broilers under high stocking density. A total of 684 1-day-old Arbor Acres broilers were selected and fed a common diet from 1 to 22 days of age. At the end of 22 days, broilers with similar weight were randomly divided into six treatments, with six replications in each treatment. The broilers in control groups were fed with a control diet and raised at low stocking density of broilers (14 broilers/m2, LSD) and high stocking density (20 broilers/m2, HSD). The broilers in treatment groups were fed with diets supplemented with 200, 400, 800 and 1600 µg Cr/kg chromium yeast (Cr-yeast) under HSD, respectively. The experimental period was 23~42 days. Compared with the LSD group, the HSD group significantly decreased the liver index (ratio of liver weight to live weight of broilers) of broilers (p < 0.05), the HSD group significantly increased the content of corticosterone (CORT) and the activities of alanine aminotransferase (ALT) and alkaline phosphatase (ALP) and decreased the prealbumin (PA) level in the serum (p < 0.05). HSD decreased the total antioxidant capacity (T-AOC) contents in the serum, liver and breast, serum glutathione peroxidase (GSH-Px) activities, breast total superoxide dismutase (T-SOD) activities and liver catalase (CAT) activities of broilers (p < 0.05). The HSD group significantly increased the total histopathological score (p < 0.05). Compared with the HSD group, adding 200, 400, and 1600 Cr-yeast significantly increased the liver index of broilers (p < 0.05), all HSD + Cr-yeast groups decreased the ALT activities (p < 0.05), and the HSD + 800 group significantly decreased the CORT contents and the ALP activities of the serum (p < 0.05); the HSD + 400, 800 and 1600 groups increased the PA contents of the serum (p < 0.05); HSD + 800 group significantly reduced the tumor necrosis factor-α (TNF-α) and Interleukin-1ß (IL-1ß) contents of the serum (p < 0.05); moreover, the HSD + 400 group increased the GSH-Px activities of the serum (p < 0.05), the T-AOC and the T-SOD activities of the breast (p < 0.05) and the T-AOC and CAT activities of the liver (p < 0.05). Adding 800 Cr-yeast significantly decreased the total histopathological score (degree of hepatocyte edema and inflammatory cell infiltration) under HSD (p < 0.05). In summary, Cr-yeast can improve the antioxidant capacity and immune traits, and liver health of broilers under HSD. Based on the results of the linear regression analysis, the optimal supplementation of Cr-yeast in antioxidant capacity, immunity ability and liver health were at the range of 425.00−665.00, 319.30−961.00, and 800.00−1531.60 µg Cr/kg, respectively.

High Dietary Organic Iron Supplementation Decreases Growth Performance and Induces Oxidative Stress in Broilers.

Although Iron (Fe) is an essential nutrient that plays a vital role in respiratory processes, excessive Fe in the diet can affect the health of broilers. We investigated the effects of diet supplemented with high levels of iron chelates with lysine and glutamic acid (Fe−LG) on the growth performance, serum biochemical parameters, antioxidant status, and duodenal mRNA expression of Fe transporters in broilers. A total of 800 1-day-old male Arbor Acres broilers were assigned to 5 groups, with 8 replicates each. Broilers were fed a corn−soybean meal basal diet or basal diets supplemented with 40, 80, 400, or 800 mg Fe/kg as Fe−LG for 6 weeks. The body weight (BW) was increased in the 80 mg Fe/kg treatment group, but decreased in the 800 mg Fe/kg treatment group on day 21. During days 1−21, compared with the control group, the supplementation of the 80 mg Fe/kg increased the average daily gain (ADG) and average daily feed intake (ADFI); however, the supplementation of the 800 mg Fe/kg group decreased the ADG and increased the FCR in broilers (p < 0.05). The heart, liver, spleen, and kidney indices were reduced in the 800 mg Fe/kg treatment group (p < 0.05). The supplementation of the 800 mg Fe/kg group increased the serum aspartate aminotransferase activity and the levels of creatinine and urea nitrogen on day 42 (p < 0.05). The broilers had considerably low liver total superoxide dismutase activity and total antioxidant capacity in the 800 mg Fe/kg treatment group (p < 0.05). Serum and liver Fe concentrations were elevated in the 400 and 800 mg Fe/kg treatment groups, but were not affected in the 40 and 80 mg Fe/kg treatment groups. The duodenal Fe transporters divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) were downregulated in the Fe−LG treatment groups (p < 0.05). We conclude that a high dietary supplement of 800 mg Fe/kg in broilers leads to detrimental health effects, causing kidney function injury and liver oxidative stress.

Exploration of wheat yellow mosaic virus-responsive miRNAs and their targets in wheat by miRNA and degradome sequencing.

Wheat (Triticum aestivum) is one of the most important food crops around the world. China is the largest wheat production country and wheat yellow mosaic virus (WYMV) is a non-negligible threat to wheat production. This study aimed to explore miRNAs and their corresponding target genes responsive to WYMV in wheat. Linmai and Jimai were used for miRNA and degradome high-throughput sequencing. After comparison and analysis, differentially expressed miRNAs and their target genes between normal wheat and WYMV-infected wheat were identified. GO and KEGG pathway enrichment analysis were then performed on target genes. A total of 530 miRNAs were identified in all samples, including 106 known miRNAs and 424 novel miRNAs. Among them, 131 miRNAs, corresponding to 85 target genes, were differentially expressed between normal wheat and WYMV-infected wheat. 85 target genes were significantly enriched in 21 GO terms and two KEGG pathways, Plant hormone signal transduction and Monobactam biosynthesis. In conclusion, 131 differentially expressed miRNAs, corresponding to 85 target genes, were identified between normal wheat and WYMVinfected wheat. Our findings provide more evidence on the roles of miRNAs and their target genes in wheat- WYMV interactions.

Triticum aestivum heat shock protein 23.6 interacts with the coat protein of wheat yellow mosaic virus.

The role of heat shock proteins (HSPs) in viral replication has been described in numerous publications. Wheat yellow mosaic virus (WYMV) belongs to the genus Bymovirus (family Potyviridae), which causes yellow mosaic and dwarf symptoms in wheat (Triticum aestivum). In this study, the T. aestivum heat shock protein 23.6 (TaHSP23.6), which belongs to the small heat shock protein family, was shown to interact with the WYMV coat protein (CP) in a yeast two-hybrid screen. The co-localization and interaction between TaHSP23.6 and WYMV CP were additionally verified in Nicotiana benthamiana by co-localization assays and bimolecular fluorescence complementation (BiFC). Not only the transcription of TaHSP23.6 but also that of other HSP family members (TaHSP70, TaHSP90, and TaHSP101) was up-regulated in WYMV-infected leaves, as shown by semi-quantitative PCR assays. Interestingly, the expression levels of the T. aestivum heat stress transcription factor A2 (TaHSFA2) members were varied in response to WYMV infection. Thus, our results provide insights into the interaction between TaHSP23.6 and WYMV infection.

Corrigendum: Differential Characteristics of Viral siRNAs Between Leaves and Roots of Wheat Plants Naturally Infected with Wheat Yellow Mosaic Virus, a Soil-Borne Virus.

[This corrects the article on p. 1802 in vol. 8, PMID: 28979249.].

Differential Characteristics of Viral siRNAs between Leaves and Roots of Wheat Plants Naturally Infected with Wheat Yellow Mosaic Virus, a Soil-Borne Virus.

RNA silencing is an important innate antiviral defense in plants. Soil-borne plant viruses naturally infect roots via soil-inhabiting vectors, but it is unclear how antiviral RNA silencing responds to virus infection in this particular tissue. In this study, viral small interfering RNA (siRNA) profiles from leaves and roots of wheat plants naturally infected with a soil-borne virus, wheat yellow mosaic virus (WYMV, genus Bymovirus), were analyzed by deep sequencing. WYMV siRNAs were much more abundant in roots than leaves, which was positively correlated with the accumulation of viral RNA. WYMV siRNAs in leaves and roots were predominantly 21- and 22-nt long and equally derived from the positive- and negative-strands of the viral genome. WYMV siRNAs from leaves and roots differed in distribution pattern along the viral genome. Interestingly, compared to siRNAs from leaves (and most other reports), those from roots obviously had a lower A/U bias at the 5'-terminal nucleotide. Moreover, the expression of Dicer-like genes upon WYMV infection were differently regulated between leaves and roots. Our data suggest that RNA silencing in roots may operate differently than in leaves against soil-borne virus invasion.