Vector‐induced Modifications in a Plant Virus

Abstract

The planthopper‐borne rough dwarf virus disease manifests itself on maize plants in two different groups of symptoms presumably caused by two distinct strains of the virus. The severe, dwarfing strain is transmitted to maize plants only by Laodelphax striatellus and Javesella pellucida. The milder, non‐dwarfing strain is transmissible by two additional delphacid species, namely Delphacodes propinqua and Sogatella vibix, which are unable to provoke the dwarfing‐strain syndrome on maize test plants. However, when the dwarfing strain was injected into the haemocoel of these two non‐vectors, the virus, upon replication and circulation in this unnatural medium, was modified into a novel strain inducing hermaphroditism in the vector‐inoculated maize test plant. Modification of the dwarfing strain into the non‐dwarfing one also occurs in the body of the natural vector (L. striatellus) when the insect acquires the former strain in an imperfect manner. This happens when the vector feeds on infected maize which is an unsuitable host species for this planthopper, or when the virus is acquired by trans‐ovum transmission. All above‐mentioned modifications are irreversible. ZUSAMMENFASSUNG VEKTOR‐BEDINGTE MODIFIKATIONEN IN EINEM PFLANZENVIRUS Die durch Langkopfzirpen übertragene Rauhverzwergungsvirose zeigt sich auf Maispflanzen in zwei verschiedenen Symptomgruppen, die vermutlich durch zwei getrennte Virusstämme verursacht werden. Der schwere, Verzwergung erregende Stamm wird auf die Maispflanzen nur durch Laodelphax striatellus und Javesella pellucida übertragen. Der mildere, nicht Verzwergung erregende Stamm ist auch durch zwei andere Langkopfzirpenarten (Delphacodes propinqua und Sogatella vibix) übertragbar, die aber unfähig sind, das Verzwergungssyndrom an Maistestpflanzen hervorzurufen. Jedoch, wenn der Verzwergungsstamm in das Haemocoel dieser zwei Nichtüberträger injiziert wurde, modifizierte das Virus infolge der Vermehrung und Zirkulation in diesem unnatürlichen Medium der Zirpenkörper in einen neuen Stamm. Dieser neue, vorher nicht vorhandene Stamm führte Hermaphroditismus in die vektor‐geimpfte Maistestpflanze ein. Modifikation des Verzwergungsstammes in einen nicht Verzwergung erregenden Stamm kommt auch im Körper des natürlichen Vektors (L. striatellus) vor, wenn dieser Überträger den erstgenannten Stamm auf unvollkommene Weise aufnimmt. Dies geschieht, wenn der Vektor auf infiziertem Mais saugt, der eine ungeeignete Wirtsart für diese Zirpe ist, oder wenn das Virus durch eine transovum‐Übertragung von der Mutterzirpe auf ihre Nachkommen aufgenommen wurde. All diese genannten Modifikationen sind nicht umkehrbar.

Identification of phytoplasmas in eggs, nymphs and adults of Scaphoideus titanus Ball reared on healthy plants

“…Rice dwarf virus (RDV) was found to be transmitted through 85% of the eggs of six succeeding generations of Nephotettix cincficeps (Uhler) (Chiykowski, 1981). Maize rough dwarf virus (MRDV) was reported to be transmitted to the progeny of Laodelphax striatellus (Fallen) by Harpaz & Klein (1969). RLOs associated with clover club leaf and rugose leaf curl passed through the eggs of their vectors Agalliopsis novella (Say) and Ausfroagallia torrida Evans, respectively (Chiykowski, 1981).…”

Genomic and phylogenetic evidence that Maize rough dwarf and Rice black-streaked dwarf fijiviruses should be classified as different geographic strains of a single species

“…In addition, both viruses are naturally transmitted by the small brown planthopper, Laodelphax striatellus Fallén, in a persistent manner. We suggest that more evidence is needed to support the claim that the vector can transmit MRDV through its eggs to a small proportion (4%) of the off spring (Harpaz and Klein, 1969;Milne et al, 1977a), while all other fi jiviruses are not transmitted via eggs.…”

“…(2) MRDV and RBSDV are transmitted almost exclusively by the planthopper, Laodelphax striatellus Fallén, whereas SRBSDV is transmitted by the white-backed planthopper (Sogatella furcifera Horváth) and MRCV by the planthopper Delphacodes kuscheli Fennah. (3) MRDV is transmitted through the eggs of its vector insect but RB-SDV is not (Harpaz and Klein 1969;Harpaz, 1972;Milne et al, 1977a). (4) Serological comparisons and hybridization experiments using cDNA probes also suggest that they are distinct viruses (Isogai et al, 1995;Marzachi et al, 1995).…”

Insights Into Insect Vector Transmission and Epidemiology of Plant-Infecting Fijiviruses

“…For FDV, transovarial transmission in P. saccharicida was reported but no data were included (Chang, 1977). Transovarial transmission of MRDV in L. striatellus was reported to be about 4% (Harpaz and Klein, 1969), but none of 300 progenies from L. striatellus eggs deposited on sorghum were viruliferous (Harpaz, 1972). For OSDV, only 0.2% transovarial transmission was found in one case (Vacke, 1966) and no evidence found in another case for J. pellucida (Lindsten, 1974).…”

“…Adverse effects include extending the nymphal stages, shortening the lifespan of adults, decreasing survival rate or fecundity (Harpaz and Klein, 1969;Nakasuji and Kiritani, 1970;Wei and Li, 2016). For example, Harpaz and Klein (1969) reported that MRDV viruliferous females of L. striatellus laid 30-50% fewer eggs than non-viruliferous females did and that the viability of these eggs was poor (14% vs. 99% for hatch from non-viruliferous). In those cases where hatching did occur, the incubation period was longer by up to 3 days (about 25%) than that of eggs from non-viruliferous females, and the mortality of the resulting larvae was high.…”