Fiji Disease Virus Research Articles

Fiji disease virus (fiji disease of sugar cane)

Fiji disease virus (fiji disease of sugar cane)

Analysis of Analysis of Agronomic Traits and Quarantine Diseases of Sugarcane Germplasms Newly Introduced from USA and Vietnem

The purpose of this study was to detect the status of Fiji disease virus (FDV) and leaf scald ( Xanthomonas albilineans ) in the newly introduced sugarcane germplasms from USA and Vietnam, and observe their agronomic performances in Guangxi sugarcane growing area, thus to provide references for screening healthy sugarcane germplasm. Following the quarantine procedure, 41 newly introduced sugarcane germplasm accessions were planted in isolated quarantine area for FDV and leaf scald detection. The PCR (RT-PCR) results showed the reaction to FDV and leaf scald were both negative and no quarantine disease occurred. Further, field experiments were conducted to observe their agronomic performance and resistance to commom diseases, like red rot, yellow spot, ring spot, pokkah boeng, mosaic, smut, rust and brown stripe diseases, and the results showed that 18 germplasm accessions were resistant to these diseases. Based on the experimental results, 8 accessions from USA and 4 accessions from Vietnam were selected for the next variety test. This study would provide excellent resistant germplasm materials and scientific references for further sugarcane disease resistance breeding.

Elimination of five viruses from sugarcane using in vitro culture of axillary buds and apical meristems

Procedures were developed for the in vitro elimination of Sugarcane mosaic virus (SCMV), Sorghum mosaic virus (SrMV), Sugarcane streak mosaic virus (SCSMV), Sugarcane yellow leaf virus (SCYLV) and Fiji disease virus (FDV) from infected sugarcane. In vitro shoot regeneration, elongation and virus elimination through meristem tissue culture originating from both apical and axillary shoots were compared. The average rates of regeneration and elongation from apical meristem tissues were 91 and 66%, respectively, with the virus-free rate among elongated shoots ranging from 61–92%. Mature axillary buds were cultivated in vitro to produce axillary shoots, from which meristem tissues were excised and cultured. These meristem tissues regenerated (77–100%) and elongated (55–88%) in culture medium at approximately the same rate as the apical meristems. The average virus elimination rate was 90% among elongated shoots derived from mature axillary buds. All five viruses can be eliminated by meristem tissue culture from both apical and axillary shoots using a standardized procedure. The overall average efficiency of virus-free plant production was 45 and 58% from apical and axillary shoots, respectively. There were no significant differences for shoot induction or virus elimination when the meristems were harvested from either the apical or the axillary shoots. This is the first report of SrMV or SCSMV elimination from sugarcane, as well as elimination of any mixed virus infections. This new method of harvesting meristems from axillary buds greatly expands the amount of material available for therapeutic treatments and thereby increases the probability of eliminating viruses from infected sugarcane.

Identification of Yeast Associated with the Planthopper, Perkinsiella saccharicida: Potential Applications for Fiji Leaf Gall Control

Yeasts associate with numerous insects, and they can assist the metabolic processes within their hosts. Two distinct yeasts were identified by PCR within the planthopper Perkinsiella saccharicida, the vector of Fiji disease virus to sugarcane. The utility of both microbes for potential paratransgenic approaches to control Fiji leaf gall (FLG) was assessed. Phylogenetic analysis showed one of the microbes is related to yeast-like symbionts from the planthoppers: Laodelphax striatellus, Nilaparvata lugens, and Sogetella furcifera. The second yeast was a member of the Candida genus, a group that has been identified in beetles and recently described in planthoppers. Microscopy revealed the presence of yeast in the fat body of P. saccharicida. The Candida yeast was cultured, and transformation was accomplished by electroporation of Candida albicans codon optimized plasmids, designed to integrate into the genome via homologous recombination. Transgenic lines conferred resistance to the antibiotic nourseothricin and expression of green fluorescent protein was observed in a proportion of the yeast cells. Stably transformed yeast lines could not be isolated as the integrative plasmids presumably replicated within the yeast without integration into the genome. If stable transformation can be achieved, then this yeast may be useful as an agent for a paratransgenic control of FLG.

In Vitro Rearing of Perkinsiella saccharicida and the Use of Leaf Segments to Assay Fiji disease virus Transmission

Fiji leaf gall (FLG) is caused by the Reovirus, Fiji disease virus (FDV), which is transmitted to sugarcane by planthoppers of the genus Perkinsiella. Low vector transmission rates and slow disease symptom development make experimentation within the FDV-Perkinsiella-sugarcane system inherently difficult. A laboratory-based technique was devised to rear the vector using sugarcane leaves as a food source. Planthoppers were reared on sugarcane leaf segments embedded in agarose enclosed within plastic containers. To provide a nondestructive assay for determination of the inoculation potential of planthoppers, FDV was detected by reverse transcription-polymerase chain reaction (RT-PCR) in newly infected sugarcane leaf segments following exposure to viruliferous planthoppers. Leaf segment inoculation correlated with development of FLG symptoms in whole plants that were fed on by the same planthoppers. Analysis of FDV RNAs within the planthopper, measured by quantitative RT-PCR (qRT-PCR), indicated that FDV RNA concentration was associated with successful inoculation of the leaf segment, transmission of FDV to sugarcane and subsequent development of FLG in plants. Quantification of FDV RNA within planthoppers provided an additional measure to assess vector competence in individuals.

Genetic variability of genome segments 3 and 9 of Fiji disease virus field isolates

Fiji leaf gall is an important disease of sugarcane in Australia and other Asia-Pacific countries. The causative agent is the reovirus Fiji disease virus (FDV). Previous reports indicate that there is variation in pathology between virus isolates. To investigate the amount of genetic variation found in FDV, 25 field isolates from Australia, Papua New Guinea and Malaysia were analysed by partial sequencing of genome segments S3 and S9. There was up to 15% divergence in the nucleotide sequence among the 25 isolates. A similar amount of divergence and pattern of relationships was found for each of the two genomic segments for most of the field isolates, although reassortment of genome segments seems likely for at least one of the Papua New Guinean isolates. The finding of a high level of variation in FDV isolated in different regions has implications for quarantine and disease management.

Variation in Acquisition of Fiji Disease Virus by <I>Perkinsiella saccharicida</I> (Hemiptera: Delphacidae)

Fiji leaf gall, caused the Fiji disease virus (genus Fijivirus, family Reoviridae, FDV), is a serious disease of sugarcane, Saccharum officinarum L., in Australia and several other Asia-Pacific countries. In Australia FDV is transmitted only by the planthopper Perkinsiella saccharicida Kirkaldy (Hemiptera: Delphacidae), in a propagative manner. Successful transmission of FDV by single planthoppers confined to individual virus free plants is highly variable, even under controlled conditions. The research reported here addresses two possible sources of this variation: (1) gender, wing form, and life stage of the planthopper; and (2) genotype of the source plant. The acquisition of FDV by macropterous males, macropterous females, brachypterous females, and nymphs of P. saccharicida from infected plants was investigated using reverse transcription-polymerase chain reaction to diagnose FDV infection in the vector. The proportion of individuals infected with FDV was not statistically related to life stage, gender, or adult wing form of the vector. The acquisition of FDV by P. saccharicida from four cultivars of sugarcane was compared to assess the influence of plant genotype on acquisition. Those planthopper populations reared on diseased 'NCo310' plants had twice as many infected planthoppers as those reared on 'Q110', 'WD1', and 'WD2'. Therefore, variation in FDV acquisition in this system is not the result of variation in the gender, wing form and life stage of the P. saccharicida vectors. The cultivar used as the source plant to rear vector populations does affect the proportion of infected planthoppers in a population.

Variation in Acquisition of Fiji Disease Virus by Perkinsiella saccharicida (Hemiptera: Delphacidae)

Variation in Acquisition of Fiji Disease Virus by Perkinsiella saccharicida (Hemiptera: Delphacidae)

Associations between DNA markers and resistance to diseases in sugarcane and effects of population substructure

Association between markers and sugarcane diseases were investigated in a collection of 154 sugarcane clones, consisting of important ancestors or parents, and cultivars. 1,068 polymorphic AFLP and 141 SRR markers were scored across all clones. Data on the four most important diseases in the Australian sugarcane industry were obtained; these diseases being pachymetra root rot (Pachymetra chaunorhiza B.J. Croft & M.W. Dick), leaf scald (Xanthomonas albilineans Dowson), Fiji leaf gall (Fiji disease virus), and smut (Ustilago scitaminea H. & P. Sydow). By a simple regression analysis, association between markers and diseases could be readily detected. However, many of these associations were due to the effects of embedded population structure and random effects. After taking population structure into account, we found that 59% of the phenotypic variation in smut resistance ratings could be accounted for by 11 markers, 32% of variation for leaf scald and pachymetra root rot rating by 4 markers, and 26% of Fiji leaf gall by 5 markers. The results suggest that marker-trait associations can be readily detected in populations generated from modern sugarcane breeding programs. This may be due to special features of past sugarcane breeding programs leading to persistent linkage disequilibrium in modern parental populations.

Molecular Analysis of Fiji Disease Virus Segments 2, 4 and 7 Completes the Genome Sequence

The complete nucleotide sequences of Fiji disease virus (FDV) genome segments S2, S4 and S7 were determined. This now completes the sequencing of all ten dsRNA genome segments of the Fijivirus type member, FDV, which comprises a total of 29339 nt. FDV S2, S4 and S7 comprised 3820, 3568 and 2194 nt, respectively. S2 and S4 each contained a single open reading frame (ORF), which encoded putative proteins of 137 and 133 kDa, respectively, while S7 contained two ORFs, which encoded putative proteins of 42 and 37 kDa. The putative amino acid sequences of FDV S2 and S4 showed most similarity to the gene products of Rice black-streaked dwarf virus (RBSDV) S2 and RBSDV S3, respectively. The putative amino acid sequences of FDV S7 ORF I and II showed most similarity to Maize rough dwarf virus (MRDV) S6 ORF I and RBSDV S7 ORF II, respectively. Phylogenetic analyses showed that FDV was most closely related to the group 2 fijiviruses.

Susceptibility of source plants to Sugarcane Fiji disease virus influences the acquisition and transmission of the virus by the planthopper vector Perkinsiella saccharicida

Abstract: Fiji leaf gall (FLG) caused by Sugarcane Fiji disease virus (SCFDV) is transmitted by the planthopper Perkinsiella saccharicida. FLG is managed through the identification and exploitation of plant resistance. The glasshouse‐based resistance screening produced inconsistent transmission results and the factors responsible for that are not known. A series of glasshouse trials conducted over a 2‐year period was compared to identify the factors responsible for the erratic transmission results. SCFDV transmission was greater when the virus was acquired by the vector from a cultivar that was susceptible to the virus than when the virus was acquired from a resistant cultivar. Virus acquisition by the vector was also greater when the vector was exposed to the susceptible cultivars than when exposed to the resistant cultivar. Results suggest that the variation in transmission levels is due to variation in susceptibility of sugarcane cultivars to SCFDV used for virus acquisition by the vector.

Improving Fiji disease resistance screening trials in sugarcane by considering virus transmission class and possible origin of Fiji disease virus

Fiji disease virus is a propagative, persistently transmitted virus that multiplies in species of the delphacid planthopper genus Perkinsiella, and in sugarcane, the feeding host of the insect. Efforts to improve and modify the disease rating system for Fiji disease have largely focussed on the planthopper as individual vectors of the virus, rather than as a population of the principal, or at least an alternative, host of the virus. This perspective has resulted in key parameters of disease incidence resulting from plant infection by propagative, persistently transmitted viruses being largely overlooked or misunderstood during efforts to improve the rating system. These parameters include the relatively long acquisition, latency, and transmission times, the percentage of the population containing virus, or viruliferous, in the above periods, and the effects of population density and number of plants visited on disease incidence. Suggestions to modify trial design to improve virus transmission to the plant, based on the disease incidence parameters of the propagative, persistent transmission class, are presented and the practical difficulties of implementing these proposals are discussed. In the context of fully understanding the underlying biology of this virus–insect–plant system, the hypothesis that Fiji disease virus, as a plant-infecting member of the Reoviridae, is primarily an insect virus with a secondary plant host, and may have diverged from an insect-infecting virus relatively recently is proposed and compared with other members of the family Reoviridae.

Production and evaluation of transgenic sugarcane containing a Fiji disease virus (FDV) genome segment S9-derived synthetic resistance gene

A transgenic line of the sugarcane cultivar Q124 with significantly enhanced resistance to Fiji disease was produced by microprojectile-mediated transformation with a transgene encoding a translatable version of Fiji disease virus (FDV) segment 9 ORF 1 under the control of the maize polyubiquitin promoter. Sixty-four transgenic lines were tested in glasshouse trials by caging the plants with viruliferous Perkinsiella saccharicida planthoppers. After 2 weeks, the planthoppers were removed and the plants monitored for symptoms. One transgenic line showed significantly enhanced resistance to Fiji disease compared with the Q124 parent and other lines showed varying levels of resistance. The molecular phenotypes of the transgenic plants at both the DNA and RNA levels were not entirely consistent with a resistance mechanism based on post-transcriptional gene silencing but were consistent with reports from other sugarcane-virus resistance systems. This is the first report of transgenic sugarcane containing an FDV-derived synthetic resistance gene showing resistance to FDV, although the mechanism of resistance has not yet been elucidated.

Sequence and phylogenetic analysis of genome segments S1, S2, S3 and S6 of Mal de Rı́o Cuarto virus, a newly accepted Fijivirus species

Mal de Rı́o Cuarto virus (MRCV) is a newly described species of the genus Fijivirus, family Reoviridae. The nucleotide sequence of four MRCV genome segments was determined. MRCV S1, S2, S3 and S6 were predicted to encode proteins of 168.4, 134.4, 141.7 and 90 kDa, respectively. MRCV S1 encodes a basic protein that contains conserved RNA-dependent RNA polymerase motifs, and is homologous to Rice black streaked dwarf virus (RBSDV), Fiji disease virus (FDV) and Nilaparvata lugens reovirus (NLRV) polymerases as well as to corresponding proteins of members of other genera of the Reoviridae. MRCV S2 codes for a protein with intermediate homology to the ones coded by RBSDV S4 and FDV S3 ‘B’ spike, which is presumably the B-spike protein. MRCV S3 most probably encodes the major core protein and is highly homologous to corresponding proteins of RBSDV S2 and FDV S3. MRCV S6-encoded protein has low homology to the proteins of unknown function coded by RBSDV S6 and FDV S6. The identity levels between all analyzed MRCV coded proteins and their RBSDV counterparts varied between 84.5 and 44.8%. The analysis of the reported sequences allowed a phylogenetic comparison of MRCV with other reovirus and supported its taxonomic status within the genus.

Resistance to Fiji disease in sugar cane: role of cultivar preference by planthopper vector Perkinsiella saccharicida (Homoptera: Delphacidae).

Fiji disease (FD) of sugar cane caused by Fiji disease virus (FDV) is transmitted by the planthopper Perkinsiella saccharicida Kirkaldy (Hemiptera Delphacidae). FD is effectively managed by using resistant cultivars, but whether the resistance is for the vector or for the virus is unknown. This knowledge would help develop a rapid and reliable glasshouse-based screening method for disease resistance. Sugar cane cultivars resistant, intermediate, and susceptible to FD were screened in a glasshouse, and the relationship between vector preferences and FD incidence was studied. Cultivar preference by nymphs increased with an increase in cultivar susceptibility to FD, but the relationship between adult preference and FD resistance was not significant. There was a positive correlation between the vector population and FD incidence, and the latent period for symptom expression declined with the increase in the vector populations. FD incidence in the glasshouse trial reflected the field-resistance status of sugar cane cultivars with known FD-resistance scores. The results suggest that resistance to FD in sugar cane is mediated by cultivar preference of the planthopper vector.

Sequence analysis of the complete genome of rice black-streaked dwarf virus isolated from maize with rough dwarf disease.

The complete nucleotide sequences of 10 genomic segments (S1-S10) from an isolate of rice black-streaked dwarf virus causing rough dwarf disease on maize (RBSDV-Hbm) in China were determined, a total of 29,142 base pairs (bp). Each segment possessed the genus-specific termini with conserved nucleotide sequences of (+) 5'-AAGUUUUU......CAGCUNNNGUC-3' and a perfect or imperfect inverted repeat of seven to eleven nucleotides immediately adjacent to the terminal conserved sequence. While the coding strand of most RBSDV-Hbm segments contained one open reading frame (ORF), there were two non-overlapping ORFs in S7 and S9, and one small overlapping ORF downstream of the major ORF in S5. Homology comparisons suggest that S1 encodes a RNA-dependent RNA polymerase (RdRp), with 63.5% and 32.6% identity to the putative RdRp encoded by Fiji disease virus (FDV) and Nilaparvata lugens reovirus (NLRV), respectively. The proteins encoded by S2, S3, and S4 showed various degrees of similarity to those encoded by the corresponding segments of FDV or NLRV. In S5 and S6, low identities were found to those of FDV only, but not to NLRV. Sequence analyses showed that RBSDV-Hbm had the most similarities in the genome organizations and the coding assignments with a RBSDV isolated from rice in China, in which each pair of the corresponding segments shared sequence identities of 93.8-98.9% and 93.5-100% at nucleotide or amino acid levels, respectively. In addition, phylogenetic analyses suggested that RBSDV-Hbm had the closest evolutionary relationship to RBSDV in Fijivirus.

Plant virus surveys on the island of New Guinea and adjacent regions of northern Australia

A series of plant virus surveys was undertaken in Papua (formerly Irian Jaya), Indonesia, Papua New Guinea, and Australia’s Torres Strait Islands, Gove and Cape York Peninsula from 1996 to 2000. Confirmed records included Chilli veirtal mottle virus, Dasheen mosaic virus, Papaya ringspot virus, Passion fruit woodiness virus, Watermelon mosaic virus and Zucchini yellow mosaic virus. Peanut stripe virus (Bean common mosaic virus) was widespread in Papua and Fiji disease virus was recorded at one location in Papua New Guinea. The first records of Glycine mosaic virus outside Australia and of a natural infection of Passiflora latent virus in Passiflora foetida are reported.

Molecular characterisation of segments 1 to 6 of Rice black-streaked dwarf virus from China provides the complete genome.

The nucleotide sequences of segments S1 to S6 of a Chinese isolate of Rice black-streaked dwarf virus (RBSDV) were determined. This provides the first complete sequence of a plant pathogenic member of the genus Fijivirus. The complete ten-segment genome has 29,141 nucleotides, making it the largest reovirus genome so far reported. Each of the segments S1-S6 is predicted to encode a single major protein. Protein comparisons indicated that S1 encoded an RNA dependent RNA polymerase, with similarities to that encoded by S1 of Nilaparvata lugens reovirus (NLRV). S2 and S3 appeared to be homologous to S3 and S4 respectively of both Fiji disease virus (FDV) and NLRV. The protein encoded on S4 showed some similarity to that of NLRV S2. The proteins encoded on S5 and S6, though similar in size to those of NLRV S5 and S6, had no detectable homologies to them or to any other known protein.

Detection of Fiji disease virus in sugarcane by ELISA

A direct double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the detection of Fiji disease virus (FDV) in sugarcane (Saccharum spp. hybrid) cultivars NCo310 and CP44-101. Optimal results were obtained when Dynatech microplates, coated with 2 �g/mL FDV-specific immuno-gamma globulin (IgG) coupled with alkaline phosphatase-lgG conjugate at a concentration of 1/1000, were used. The test could detect FDV in crude extracts (fresh or frozen) of gall and gall-free infected tissues with an end point dilution of 1/5000 and 1/1000, respectively. The FDV antibody showed a high degree of specificity and failed to react with 3 other field-associated sugarcane viruses. When the distribution of FDV within the plant was studied, the highest titre was found in the basal axillary buds decreasing towards the top of the plant and into the roots. However, the apical meristem produced a virus titre significantly higher than any adjacent axillary buds. The ELISA was well suited for large-scale screening programs and its potential was further extended to quarantine work since it could be used to identify the virus in frozen, non-galled tissues.

Development of an Axillary Bud Culture Technique for Fiji Disease Virus Elimination in Sugarcane

A technique was developed for culture of axillary buds of sugarcane (Saccharum spp. hybrid) cultivar NCo310. Successful establishment was obtained following surface sterilisation (sodium hypochlorite 4% for 5 min), decontamination (100 mg L-1 carbenicillin, 25 mg L-1 nystatin and 100 mg L-1 benlate) and a double heat treatment applied firstly to setts (single-bud vegetative cuttings; 50°C for 120 min) and then to the isolated axillary buds (61°C for 30 min). The most suitable bud culture medium consisted of half-strength Murashige and Skoog nutrients plus 8 g L-1 agar, 30 g L-1 sucrose, 2 mg L-1 naphthalene-acetic acid and 500 mg L-1 malt extract. Roots and hence plantlets could be developed for all cultures following incubation in distilled water. Decontamination and heat treatment resulted in eradication of pathogens from 94% and Fiji disease virus from 28% of the cultures.