Details of DPV and References

DPV NO: 300 September 1985

Family: Unallocated ssRNA- viruses

Genus: Tenuivirus

Species: Maize stripe virus | Acronym: MSpV

Maize stripe virus

R. F. Gingery USDA-ARS, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691, USA

Contents

Introduction

Disease probably discovered by Shepherd (1929) and described in detail by Storey (1936).

Synonyms

Maize chlorotic stripe virus (Autrey, 1983)

Maize hoja blanca virus (Trujillo et al., 1974)

A virus with fine filamentous particles 3 nm in diameter and of undetermined length. The particles sediment as four major components, contain a single species of coat protein and five species of single-stranded RNA. Large amounts of a disease-associated non-particle or ‘non-capsid’ (NC) protein are found in infected tissue. The only known vector is the delphacid planthopper, Peregrinus maidis, which transmits the virus in the persistent propagative manner and transovarially. It is not transmitted by sap inoculation. The virus infects only a few species of Gramineae. It is found throughout the tropics where it occasionally causes serious losses.

Main Diseases

In maize (Zea mays), the virus causes severe chlorotic striping and streaking with frequent apical bending (Fig. 1, Fig. 2). Infected plants are stunted and produce little or no grain (Tsai, 1975; Gingery et al., 1979; Greber, 1981).

Geographical Distribution

The virus occurs world-wide in most tropical maize-growing regions where the distributions of maize and Peregrinus maidis overlap. It has been reported from Florida, USA (Tsai, 1975), Venezuela (Trujillo et al., 1974), Peru (Nault et al., 1979), Guadeloupe (Migliori & Lastra, 1980), Nigeria and Sao Tome (H. W. Rossel, personal communication), Kenya (Kulkarni, 1973), Botswana (P. Jones, personal communication), Mauritius and Reunion (Autrey, 1983), Australia (Greber, 1981), Costa Rica (R. Gomez & L. R. Nault, personal communication) and possibly the Philippines (Exconde, 1977).

Host Range and Symptomatology

The virus occurs naturally in maize, sorghum and itchgrass (Rottboellia exaltata) (Trujillo et al., 1974; Greber, 1981). Experimentally, the virus infects barley, rye, triticale (Greber, 1981), oats (Falk & Tsai, 1983) and several teosintes (Zea spp.) (Nault et al., 1982).

Diagnostic species

Zea mays (maize). Initial symptoms are chlorotic spots and streaks in the youngest leaves 4-7 days after inoculation depending on the temperature (Gingery et al., 1981; Greber, 1981). As the leaves expand, the spots and streaks fuse to form variable-width chlorotic bands. Late in infection most of the leaf may become chlorotic (Fig. 2). Plants are stunted and commonly exhibit acute bending at the apex (Fig. 1). Many plants die when infected early.

Rottboellia exaltata. Foliar symptoms similar to those on maize.

Oryza sativa (rice) and Triticum aestivum (wheat) are not infected.

Propagation species

Cultures of the virus are maintained in maize by serial passage with Peregrinus maidis. Plants are normally inoculated at the 3- to 4-leaf stage.

Assay species

Maize seedlings are used in a whole plant assay to test for transmission by vectors.

Strains

Isolates from different locations have not been critically compared. The maize chlorotic stripe strain from Mauritius, Rodrigues and Reunion causes symptoms different from those of the type strain from the USA (Autrey, 1983), but the strains are serologically indistinguishable (R. E. Gingery and L. J. C. Autrey, unpublished data).

Transmission by Vectors

The vector is the corn planthopper, Peregrinus maidis (Auchenorrhyncha:Delphacidae). Species known not to be vectors include Dalbulus maidis (Gingery et al., 1979), Sogatella kolophon and a Toya sp. (Greber, 1981). The virus is transmitted in the persistent manner but intermittently. Nymphs are more efficient than adults in transmitting the virus (Tsai & Zitter, 1982). The mean latent period in the insect has been reported to be 10 days (Gingery et al., 1981), 9 to 13 days (Tsai & Zitter, 1982) and 15.6 days (Greber, 1981), with individuals first transmitting between 4 and 22 days after acquisition. The virus does not shorten the life span of viruliferous individuals, but can reduce insect fecundity by up to 50% (Tsai & Zitter, 1982; L. R. Nault, personal communication). The virus is transmitted through the egg (Gingery et al., 1981; Tsai & Zitter, 1982).

Transmission through Seed

No information.

Serology

The virus particles and the NC protein are both good immunogens. Rabbit antisera with titres of 1/256 to 1/1024 in microprecipitin tests are easily produced. It is not necessary to disrupt the particles to obtain positive reactions in agar-gel double-diffusion tests. Enzyme-linked immunosorbent assay (ELISA) with virus antiserum is useful in screening plants or insects for infection (Nault et al., 1979). ELISA with antiserum to the NC protein has been used to detect infected plants (Falk & Tsai, 1983). There is no serological cross-reactivity between virus particles and the NC protein (Gingery et al., 1981; Falk & Tsai, 1983).

Relationships

Particles of the virus are serologically related to those of rice stripe virus (Gingery et al., 1981, 1983), but there is no evidence that the NC proteins of the two viruses are serologically related. Purified preparations of rice stripe virus contain not only 3-nm-wide nucleoprotein filaments similar to those of maize stripe virus, but also branched filaments (thought to be supercoiled configurations of circular strands) (Koganezawa et al., 1975) and 8-nm-wide filamentous particles (Toriyama, 1982), neither of which have been observed for maize stripe virus. Other viruses with 3-nm filamentous structures and associated NC proteins are rice grassy stunt virus (H. Hibino, personal communication), rice hoja blanca virus (Morales & Niessen, 1983; Descr. 299) and European wheat striate mosaic virus (R. E. Gingery, unpublished data). None of these viruses appear to be serologically related to maize stripe virus (Gingery et al., 1981; H. Hibino & R. E. Gingery, unpublished data; B. W. Falk, personal communication).

Stability in Sap

Assayed by virus transmission after injection of Peregrinus maidis with chloroform-clarified extracts from infected maize. The virus has a thermal inactivation point between 45 and 50°C; a longevity in vitro of less than 24 h at room temperature and about 3 days at 4°C; and a dilution end-point between 10^-2 and 10^-3.

Purification

(Gingery et al., 1981). Grind infected leaves in 8-10 vol 0.01 M potassium phosphate, 10 mM EDTA, pH 7.0 (EB), containing 0.5% 2-mercaptoethanol and 200 µg/ml bentonite. Press through cheesecloth and clarify by emulsifying with 0.25 vol chloroform. Recover the aqueous phase by centrifugation at 8000 g (max) for 10 min. Centrifuge the clarified extract for 3 h at 110,000 g (max) through a cushion of 30% sucrose in EB. Resuspend the pellets in 0.14 M NaCl, 0.01 M potassium phosphate, 0.01 M EDTA, pH 7.0 (PBS-EDTA) and centrifuge in rate-zonal sucrose gradients and/or isopycnic CsCl or Cs₂SO₄ gradients. Further purify individual components by concentration and centrifugation on additional rate-zonal gradients. Yields of purified virus range from 80 to 120 mg per kg fresh tissue. The virus particles are very labile and susceptible to RNase, and it is desirable to work in the cold and to treat all solutions and glassware to eliminate RNase activity.

The NC protein may be purified by exploiting its crystallization below and solubilization above pH 6.0. The procedure of Gingery et al. (1981) works, but the following variation yields more protein (R. E. Gingery, unpublished data). Very chlorotic tissue from old infections contains the most NC protein. Grind the tissue in 1.5 vol phosphate-citrate buffer, pH 5.0 (prepared by mixing 0.2 M K₂HPO₄ and 0.1 M citric acid) by grinding one third of the tissue at a time and pressing the extract through cheesecloth after each grinding. Hold the extract overnight at 4°C to maximize crystallization of the protein. Recover the crystals by sedimentation at 12,000 g (max) for 30 min, dissolve them in phosphate-citrate buffer, pH 7.0 (0.1 vol), and clarify the solution by centrifugation at 12,000 g (max) for 10 min. Adjust the supernatant fluid to pH 5.4 with 0.1 M citric acid and hold overnight at 4°C for recrystallization. Repeat the solubilization-recrystallization sequence three to five times. Further purify the protein by isopycnic centrifugation in CsCl (Gingery et al., 1981) or by polyacrylamide gel electrophoresis (Falk & Tsai, 1983).

Properties of Particles

The virus sediments as four major components with sedimentation coefficients between 70 and 187 S (Fig. 3) (Falk & Tsai, 1984).

Absorbance (A_{0.1%, 1cm, 260nm}) about 2.3 (Gingery et al., 1981).

A₂₆₀/A₂₈₀: about 1.39 (not corrected for light-scattering).

Buoyant density (all components): 1.28 g/ml in CsCl in PBS-EDTA; 1.27 g/ml in Cs₂SO₄ in 0.15 M NaCl, 0.015 M sodium citrate, pH 7.0.

Particle Structure

Although first reported to be isometric (Kulkarni, 1973; Trujillo et al., 1974), the virus particles are now known to be 3 nm-wide, filamentous nucleoprotein strands. Linear, circular and helical forms have been reported (Fig. 4, Fig. 5, Fig. 6) (Gingery et al., 1981; R. E. Gingery, unpublished data). There is no information about the morphologies of the individual components.

Particle Composition

Nucleic acid: Five species of single-stranded RNA are found in the particles, ranging in M. Wt ( x 10^-6) from 0.52 to 3.01 with some correlation between the size of the RNA species and the sedimentation coefficient of the virus component. After phenol extraction of the particles, five species of double-stranded RNA are also found with M. Wt about double those of the single-stranded species. These double-stranded RNA species are not seen if the particles are disrupted in sodium dodecyl sulphate without phenol immediately before electrophoresis, which suggests that negative and positive sense RNA species are separately encapsidated (Falk & Tsai, 1984). RNA constitutes 5-6% of the particle weight (Gingery et al., 1981).

Protein: One species, of M. Wt 32.7 x 10³ (Gingery et al., 1981).

Relations with Cells and Tissues

The disease-associated NC protein (M. Wt 16.3 x 10³) is recovered from infected tissue in amounts up to 2 mg per g fresh tissue. The protein forms needle-shaped crystals below pH 6 in vitro. The NC protein has been found in infected maize, itchgrass, rye (Secale cereale) and oats (Avena sativa), but not in viruliferous Peregrinus maidis (Falk & Tsai, 1983).

Two types of inclusion are found in the epidermis, mesophyll, vascular parenchyma and phloem elements of infected maize (Ammar et al., 1985). One type consists of long, narrow bundles of filamentous electron-opaque (FEO) material (Fig. 7, Fig. 8); the other type consists of irregularly-shaped masses of amorphous, semi-electron-opaque (ASO) material (Fig. 9). Some cells contain both types. Antibodies to the NC protein bind to FEO inclusions; antibodies to virus bind only to an unidentified cytoplasmic constituent, and neither antibody binds to ASO inclusions.

Infected plants contain six double-stranded RNA species. Five appear the same in size as those isolated from purified virus (see Particle Composition) and one is smaller, of M. Wt 0.66 x 10⁶ (Falk & Tsai, 1984).

Virus particles are found in the muscle, brain, midgut, hindgut, Malpighian tubules, salivary glands, ovaries, eggs, spermatheca and male sperm sac of P. maidis by ELISA (L. R. Nault & D. T. Gordon, personal communication).

Notes

Maize stripe virus is readily distinguished from other maize viruses by symptomatology and by its unusual morphology and sedimentation pattern. Also, it is the only maize virus known to be transmitted by Peregrinus maidis except for maize mosaic and maize sterile stunt viruses, which are rhabdoviruses distinguishable from maize stripe virus by particle morphology and serological tests. The maize stripe virus reported from India (Raychaudhuri et al., 1977) is synonymous with maize mosaic virus (Sharma & Payak, 1983).

Figures

References list for DPV: Maize stripe virus (300)

1. Ammar, Gingery & Nault, Phytopathology 75: 84, 1985.
2. Autrey, in Proc. int. Maize Virus Dis. Colloq. Workshop, Wooster, Ohio, 1982: 167, 1983.
3. Exconde, in Proc. int. Maize Virus Dis. Colloq. Workshop, Wooster, Ohio, 1982: 83, 1983.
4. Falk & Tsai, Phytopathology 73: 1259, 1983.
5. Falk & Tsai, Phytopathology 74: 909, 1984.
6. Gingery, Nault, Tsai & Lastra, Pl. Dis. Reptr 63: 341, 1979.
7. Gingery, Nault & Bradfute, Virology 112: 99, 1981.
8. Gingery, Nault & Yamashita, J. gen. Virol. 64: 1765, 1983.
9. Greber, Aust. J. agric. Res. 32: 27, 1981.
10. Koganezawa, Doi & Yora, Ann. phytopath. Soc. Japan 41: 148, 1975.
11. Kulkarni, Ann. appl. Biol. 75: 205, 1973.
12. Migliori & Lastra, Annls Phytopath. 12: 277, 1980.
13. Morales & Niessen, Phytopathology 73: 971, 1983.
14. Nault, Gordon, Gingery, Bradfute & Castillo-Loayza, Phytopathology 69: 824, 1979.
15. Nault, Gordon, Damsteegt & Iltis, Pl. Dis. 66: 61, 1982.
16. Raychaudhuri, Seth, Renfro & Varma, in Proc. int. Maize Virus Dis. Colloq. Workshop, Wooster, Ohio, 1976: 69, 1977.
17. Sharma & Payak, in Proc. int. Maize Virus Dis. Colloq. Workshop, Wooster, Ohio, 1982: 186, 1983.
18. Shepherd, Trop. Agric. Trin. 6: 320, 1929.
19. Storey, E. Afr. agric. J. 1: 333, 1936.
20. Toriyama, J. gen. Virol. 61: 187, 1982.
21. Trujillo, Acosta & Pinero, Pl. Dis. Reptr 58: 122, 1974.
22. Tsai, Pl. Dis. Reptr 59: 830, 1975.
23. Tsai & Zitter, J. econ. Entomol. 75: 397, 1982.