Academic literature on the topic 'Corn rough dwarf virus disease'

A widespread disease of pangola grass (Digitaria decumbens) and summer grass (D. ciliaris) in south-eastern Queensland was characterized by a bunched and stunted growth habit, yellow or red discolouration of the foliage, seed heads with crimped, distorted racemes, and sometimes premature plant death. Virus-like particles present in extracts of diseased plants were unstable, 50-70 nm in diameter, had a core and outer coat and were morphologically similar to particles of viruses in the genus Fijivirus, family Reoviridae. The particles were shown by immune electron microscopy to be serologically closely related to pangola stunt and maize rough dwarf viruses, but unrelated to oat sterile dwarf virus. Similar virus-like particles were observed in crystalline arrays in ultrathin sections of cells in vein enations of D. ciliaris. Extracts of diseased pangola grass and summer grass contained 10 double-stranded RNA species, which were somewhat similar in size to those reported for pangola stunt virus. A planthopper, Sogatella kolophon, which is related to the South American vector of pangola stunt virus, S. furcifera, was associated with diseased pangola grass and summer grass in the field, and was shown to be a vector. However, efforts to infect maize, a major host of maize rough dwarf virus, were unsuccessful. On the basis of these properties the Australian virus is considered to be pangola stunt virus.

“Mal de Río Cuarto” (MRC) is the most important viral disease affecting corn in Argentina. Reovirus-like particles were observed in diseased plants (1,4) and were later serologically related to an isolate of maize rough dwarf virus (3), though this relationship was recently questioned (2). Based on estimates of the prevalence and severity of MRC and yield losses, government agencies, corn hybrid seed companies, and growers agreed that the worst epidemic in the country occurred during the 1996 to 1997 agricultural year. Approximately 300,000 ha of corn were affected by the disease and yield losses were estimated at $120 million. Affected areas included the central and southern Santa Fe, the central, northern, southeastern, and western Buenos Aires, and the eastern and southern (originally the endemic center of MRC in Río Cuarto County) parts of Córdoba. Virus infections were confirmed by double-antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) in root samples from each surveyed location, using an antiserum to MRC virus. The occurrence of MRC in non-endemic areas suggests an unusual phenological coincidence of high vector populations, abundant natural virus reservoirs, and susceptible stages in the crop. Most commercial hybrids surveyed were apparently susceptible to the virus, although some were tolerant. References: (1) O. E. Bradfute et al. Phytopathology 71:205, 1981. (2) C. Marzachi et al. Sem. Virol. 6:103, 1995. (3) R. G. Milne et al. Phytopathology 73:1290, 1983. (4) S. F. Nome et al. Phytopathol. Z. 101:7, 1981.

Rice black streaked dwarf virus (RBSDV) is an important agent causing maize rough dwarf disease, whereas the host factors responding to RBSDV infection are poorly understood. To uncover the molecular interactions between RBSDV and maize, a yeast two-hybrid screen of a maize cDNA library was carried out using the viral P8 protein as a bait. ZmAKINβγ-1 and ZmAKINβγ-2 (βγ subunit of Arabidopsis SNF1 kinase homolog in maize) possessing high sequence similarities (encoded by two gene copies) were identified as interaction partners. Their interactions with P8 were confirmed in both Nicotiana benthamiana cells and maize protoplasts by bimolecular fluorescence complementation assay. The accumulation levels of ZmAKINβγ mRNAs were upregulated at the stage of the viral symptoms beginning to appear and then downregulated. ZmAKINβγs are putative regulatory subunits of the SnRK1 complex, a core regulator for energy homeostasis. Knockdown of ZmAKINβγs in maize regulated the expression levels of the genes involved in sugar synthesis or degradation, and also the contents of both glucose and sucrose. Importantly, downregulation of ZmAKINβγs expressions facilitated the accumulation of RBSDV in maize. These results implicate a role of ZmAKINβγs in the regulation of primary carbohydrate metabolism, and in the defense against RBSDV infection.

Rice black-streaked dwarf virus (RBSDV), a Fijivirus, causes maize rough dwarf disease and rice black-streaked dwarf disease in the summer maize-growing regions of the Yellow and Huai rivers, respectively, in China. Nevertheless, the diversification and selection of the entire genome from S1 to S10 have not been illuminated. Molecular variation, evolution, conserved regions, and other genomic properties were analyzed in 21 RBSDV isolates from maize (Zea mays L.) and rice (Oryza sativa) hosts sampled from nine geographic locations in China. Low codon adaptation index values ranging from 0.1878 to 0.2918 indicated a low degree of codon-usage bias and low potential expression for all 13 RBSDV open reading frames (ORFs). ORF9-2 showed a stronger effect of codon usage bias than did other ORFs, as the majority of points for this ORF lay close to the standard curve in the Nc plot (the effective number of codons [Nc] versus the frequency of G+C at synonymous third-base positions [GC3]). A 9-bp deletion mutation was detected in the RBSDV genome in the 3′ UTR of S8. Nucleotide diversity analysis indicated that the structural proteins of RBSDV, such as S2 and S4, were all more conserved than nonstructural proteins such as S9. Nucleotide diversity (π) was highest among S9 sequences (0.0656), and was significantly higher than among S4 sequences (0.0225, P < 0.01). The number of conserved regions among the 10 segments varied substantially. The highest number of conserved regions (5) was found in S5, whereas no conserved regions were identified in S9. Nucleotide diversity and the number of conserved regions were independent of the lengths of segments. Nucleotide diversity was also not correlated with the number of conserved regions in segments. Ten recombination events in 21 isolates were found in seven segments with breakpoint positions in UTRs, intergenic spacer regions, and gene coding regions. The number of recombination events was also independent of the lengths of segments. RBSDV isolates from China could be phylogenetically classified into two groups using either 10 segment sequences or the concatenated sequence of S1 through S10, regardless of host or geographical location. The phylogenetic tree generated from pairwise nucleotide identities of individual RBSDV segments such as S9 and S3, with nucleotide identity values of 93.74% and 95.86%, respectively, is similar to the tree constructed from the concatenated sequences of the entire RBSDV genome. The 13 RBSDV ORFs were under negative and purifying selection (Ka/Ks < 1). ORF5-2 was under the greatest selection pressure; however, ORF2, which encodes the core protein of RBSDV, was under the lowest selection pressure.

Maize dwarf mosaic virus (MDMV) is a serious maize pathogen, epidemic worldwide, and one of the most common virus diseases for monocotyledonous plants, causing up to 70% loss in corn yield globally since 1960. MDMV belongs to the genus Potyvirus (Potyviridae) and was first identified in 1964 in Illinois in corn and Johnsongrass. MDMV is a single stranded positive sense RNA virus and is transmitted in a non-persistent manner by several aphid species. MDMV is amongst the most important virus diseases in maize worldwide. This review will discuss its genome, transmission, symptomatology, diagnosis and management. Particular emphasis will be given to the current state of knowledge on the diagnosis and control of MDMV, due to its importance in reducing the impact of maize dwarf mosaic disease, to produce an enhanced quality and quantity of maize.

Resistance to maize rough dwarf disease (MRDD), a major cause of crop losses, depends on external conditions such as the virus transmission period and the rate of viruliferous small brown planthoppers, Laodelphax striatellus. The precise identification of MRDD contributes to the utilization of resistant germplasm and the cloning of resistant genes. In this study, eight maize varieties were artificially inoculated in a greenhouse with viruliferous planthoppers. The viral titers in maize seedlings were detected by quantitative fluorescence RT-PCR, and the viral replication curves were analyzed by regression. A logistic model fit the Rice black-streaked dwarf virus (RBSDV) replication data for five susceptible varieties well, whereas a linear model fit the data for three resistant varieties. Among the five susceptible varieties, the time points with the maximum replication rates (tIP) of the highly susceptible Ye478 and XH6 were significantly earlier than those of the three susceptible varieties, Mo17, Zheng58, and Zhengdan958. P138, the most highly resistant variety, had the lowest slope of the best fit line, followed by moderately resistant Chang7-2 and Dan 340. The RBSDV replication curve model developed in this study can accurately identify the resistance of maize germplasm to MRDD at the molecular level. Our results also suggested that tIP and the slope of the RBSDV replication curve can be considered new criteria to evaluate maize resistance to MRDD.

Field experiments were conducted to evaluate the hypothesis that johnsongrass control in corn causes increased maize dwarf mosaic virus (MDMV) and maize chlorotic dwarf virus (MCDV) disease severity because of increased movement of insect vectors from dying johnsongrass to the corn crop. Johnsongrass control treatments included 1) broadcast POST nicosulfuron, 2) directed POST imazethapyr, 3) mechanical control, and 4) no treatment. Disease severity in both a virus-susceptible and a virus-tolerant corn hybrid was evaluated. With the virus-susceptible hybrid, greater disease severity was observed where johnsongrass was controlled in the experimental area than where johnsongrass was not controlled. Increases in disease severity were independent of the method of johnsongrass control. Corollary studies conducted on the same site verified a double infection of corn with MDMV and MCDV and documented movement of blackfaced leafhoppers, the insect vector of MCDV, subsequent to treatment of johnsongrass.

Two major maize viruses have been reported in the United States: Maize dwarf mosaic virus (MDMV) and Maize chlorotic dwarf virus (MCDV). These viruses co-occur in regions where maize is grown, such that co-infections are likely. Co-infection of different strains of MCDV is also observed, and a synergistic enhancement of symptoms in co-infected plants was previously reported. Here, we examined the impact of co-infections of two strains of MCDV (MCDV-S and MCDV-M1, severe and mild, respectively), and co-infections of MCDV and MDMV in the sweet corn hybrid ‘Spirit’ in greenhouse experiments. Quantitative plant growth and development parameters were measured and virus accumulation was measured by reverse-transcriptase quantitative polymerase chain reaction. Virus symptoms were enhanced and plants showed no recovery over time in co-infections of MDMV-OH and MCDV-S but virus titers and quantitative growth parameters did not indicate synergy in co-infected plants. MCDV-M1 co-infections with either MDMV-OH or MCDV-S did not show symptom enhancement or evidence of synergism.

Field and laboratory experiments were conducted to evaluate the effect of postemergence johnsongrass control on incidence of maize chlorotic dwarf virus (MCDV) and maize dwarf mosaic virus (MDMV) in corn and to confirm the presence and movement of the blackfaced leafhopper, the insect vector of MCDV. Corn plants surrounded by MCDV- and MDMV-infected rhizomatous johnsongrass were either treated or not treated with nicosulfuron at 35 g ai/ha. Corn tissue samples were taken at the time of treatment and 4, 9, 14, and 21 d after treatment and the presence of MCDV and MDMV was determined by enzyme-linked immunosorbent assay (ELISA). Virus incidence in treated experimental units was higher at the later sampling dates relative to the nontreated. Earlier differences in incidence of MCDV and MDMV double infection in corn were detected where johnsongrass was controlled. Movement of the insect vector of MCDV was observed within the experimental area after johnsongrass was controlled, but was not significantly different from that in nontreated areas.

Maize dwarf mosaic (MDM), caused by Maize dwarf mosaic virus (MDMV) and Sugarcane mosaic virus (SCMV), is an economically important viral disease of sweet corn (Zea mays). MDM is known to increase the severity of fungal root rots and southern corn leaf blight (SCLB). The effect of infection with MDMV-A and SCMV on eight foliar diseases was evaluated on 32 sweet corn hybrids (27 MDM-susceptible hybrids and five MDM-resistant hybrids) in 2007, 2008, and 2009. Virus infection substantially increased the severity of five diseases, including: SCLB, northern corn leaf spot (NCLS), gray leaf spot (GLS), Diplodia leaf streak (DLS), and eyespot. Among MDM-susceptible hybrids, mean severity of SCLB, NCLS, GLS, DLS, and eyespot on virus-infected plants was typically double that of plants that were asymptomatic of viral infection. Three diseases were not substantially increased by MDM, including: common rust, northern corn leaf blight (NCLB), and Stewart's wilt. Virus infection appeared to affect the severity of diseases caused by necrotrophic foliar fungi that colonize mesophyll tissue. MDM did not appear to substantially affect the severity of diseases caused by pathogens that form haustoria or invade the vascular system. The extent to which SCLB severity is increased by MDM in terms of changes in level of host resistance also was determined. For MDM-susceptible hybrids, reactions to SCLB ranged from resistant to moderately susceptible in MDM-free treatments, but each of these hybrids was classified as moderately susceptible to susceptible when infected with MDMV-A and/or SCMV. The results of this experiment demonstrate the importance of breeding for MDM resistance, not only to control this important viral disease of sweet corn, but also to lower the potential for detrimental effects from several other foliar diseases that often are of minor importance on sweet corn in the absence of MDM.

Gray leaf spot, caused by Cercospora zeae-maydis, can be a yield-limiting factor in maize where continuous minimum tillage practices are followed. Commercial corn hybrids were evaluated for response to gray leaf spot for seven years at two Virginia locations (Shenandoah and Wythe Counties) and one year at a third location in Virginia (Montgomery County). Yield losses, when comparing resistant to susceptible classes, were approximately 2,000 kg ha⁻¹ at Wythe County in 1982, 750 kg ha⁻¹ at Shenandoah County in 1984, and 2,150 kg ha⁻¹ at Montgomery County in 1988. The inheritance of reaction to gray leaf spot was studied using a 14 inbred diallel in Montgomery and Wythe Counties, Virginia in 1987 and 1988 planted in randomized complete block designs. Resistance was found to be highly heritable and controlled by additive gene action. Inbreds producing high yielding, resistant, and agronomically superior hybrids were identified (B68, NC250, Pa875, Va14, Va17, and Va85); and several hybrids between these lines had high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875). Currently available inbreds could be used to produce hybrids with higher levels of resistance than hybrids currently available to growers, and these could serve as a basis for gray leaf spot breeding programs. Lesion size measurements were not correlated with disease scores. Late-season photosynthesis rates were associated positively with resistance. The hybrids of some inbreds were found to produce high levels of pigment (believed to be anthocyanins) around the gray leaf spot lesions. These did not limit the size of the individual lesion later in the season. Some pigment(s)-producing genotypes were found to be resistant when the pigment character was expressed. This type of resistance must prevent or inhibit infection of the leaf but not later colonization, once established. Maize dwarf mosaic virus (MDMV) also limits maize production in some areas where johnsongrass (Sorghum halepense L.) is a problem. Resistance to MDMV was found to be mainly additive and highly heritable. However, a strong specific combining ability component was found, indicating that the background of the material receiving resistance genes may have a strong effect on the expression of resistance. Inbreds capable of producing high-yielding, resistant, and agronomically acceptable hybrids are available (B68, NC250, A632, Pa875, Va17, and Va85); and several hybrids between these lines have high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875).
Ph. D.