SUMMARYA mechanically transmissible virus causing leaf mottling and ringspotting of Passiflora edulis var. flavicarpa in the Ivory Coast is described. Its particles are flexuous rods 810–830 nm long and 15 nm wide. It infects mainly species of Passifloraceae and Leguminosae; Passiflora foetida is a good diagnostic host. Aphis gossypii and Aphis spiraecola transmit the virus after brief acquisition feeds. Seed transmission was not detected. In crude sap of P. edulis, infectivity was lost after 10 min at 65–70 °C, 12–14 days at 24 °C or dilution to 10‐7. A purification method is described, using Triton‐X‐100 as clarifying agent. The virus is serologically related but not identical to passionfruit woodiness virus from Queensland. The virus seems to belong to the potato virus Y group and has the cryptogram */*:*/(6):E/E:S/Ap. It is designated passionfruit ringspot virus.
No dodder transmission was found. Serological relationship with onion yellow dwarf virus and Columbian Datura virus was established.
The percentage of passionfruit ringspot virus infection in batches of young passionfruit seedlings exposed in the open in a plot of diseased fully grown passionfruits was significantly correlated with the number of winged Aphis spiraecola trapped in yellow watertrays during the time of exposure.Of all aphids trapped, 98 ~ were A. spiraecola, colonizing predominantly Eupatorium eonyzoides (Compositae). This plant was found colonized everywhere in the forest area of Ivory Coast, which emphasizes the importance of A. spiraeeola as a potential virus vector in this part of Africa. The numlzers of trapped A. spiraecola were positively correlated with the preceding rainfall in mm with an interval of two weeks before the assessment. The influence of a period of rainfall lasted four to six weeks.member of the potyvirus group, could be transmitted experimentally by Aphis gossypii and A. spiraecola after brief acquisition feeds (De Wijs, 1974). Therefore a field experiment was set up to find out which aphids were responsable for the spread of PRV in the field. Materials and methodsExperimental site. The experimental fields of the ORSTOM at Adiopodoum6, IvoryCoast, are situated 17 km west of Abidjan at about 50 m above sea level and surrounded to the North and East side by secondary rain forest and to the South and West side by African cultivation.The passionfruit plots. The site of the two passionfruit plots in the experimental fields of the ORSTOM can be seen on Fig. 1. Passionfruit plot No 1 consisted of three rows ' " I~ Habitations Parc meteo r--l J f 4
In greenhouse trials paraffinic mineral oils, characterized by a viscosity gravity constant (VGC) of 0.790 0.819, and with viscosities between 12 and 30 cSt at 37~ (66-150 SUS) proved to have the best aphid transmission inhibiting activity of potato virus Y to red peppers. The activity decreased rapidly with decreasing viscosities but only slowly with increasing values.Effective oils are further characterized by an unsulfonated residue (USR) of 95-100, indicating the near or total absence of aromatic structures, which are inactive and known to be phytotoxic. The paraffine-pourpoint should be below 0~ indicating that n-paraffines do not form a very important part of the oil, since they are also inactive. Naphthenic structures seem equally inert, their percentage in the oil depending on the origin of the crude oil, because they cannot be separated from the paraffinic structures by refining procedures.Mineral oils which one commercialize for agricultural practice normally have an USR above 95 and a paraffine-pourpoint below 0 ~ Therefore, the information on the classification, based on a VGC value and on the viscosity, is already sufficient to allow an evaluation of those oils of their suitability as inhibitor of the virus transmission by aphids.Additional keyword: Capsicum annuum.
During a study on passionfruit viruses in Ivory Coast, a survey for wild Passifloraceae in the neighbourhood of the ORSTOM, revealed that Adenia lobata was very often present in het forest border. Plants showing mosaic symptoms in their leaves were first found in 1970. Check inoculations on Passiflora edulis var. flaviearpa andP.foetida caused the same symptoms in these test plants as passionfruit ringspot virus (PRV)did (De Wijs, 1974). A. lobata plants with less obvious symptoms and even without symptoms gave the same reaction. One plant was chosen for further indentification of the virus involved. From the beginning of the study PRV was used for comparison with the Adenia virus (AV).The preparation of inoculum, determination of the in vitro properties, aphid transmission experiments, purification of the AV from A. lobata, length measurements of the virus particles and serological testing of the crude juice of P. edulis were done as described earlier (De Wijs, 1974). Purified virus preparations were examined in an electron microscope after contrasting with neutral 2 ~ (w/v) phosphotungstate. For antigen from A. lobata the crude sap had to be clarified more thoroughly to avoid aspecific reactions with the available antiserum (homologous titre 4096) against PRV. Crude sap of A. lobata had to be emulsified with an equal volume of chloroform for 30 min and clarified by low-speed centrifugation, 10 min. at 12,000 g, in the SS 34 rotor of a Sorvall RC2B refrigerated centrifuge. The supernatant was deep frozen at -18 ~ for 18 h and once more clarified by low-speed centrifugation after thawing to get rid of fraction 1 protein (Van Regenmortel, 1964). Antigen was then concentrated by high-speed centrifugafion in a Spinco L50 preparative centrifuge: 150 min at 54,000 g in the R 30 rotor. The pellets were resuspended in a 0.9 % NaC1 solution and clarified by low-speed centrifugation. Host range and symptoms.
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