No abstract

No abstract

Wheat spindle streak mosaic virus was transmitted via isolates of each of the zoosporic fungi were cultured on wheat water from soil-free roots of wheat plants infected by growing infected with the virus by sap inoculation of leaves, the virus in infective soil, but not from plants grown in sterile soil and was transmitted by root association in sand only from plants infected with the virus by sap inoculation of the leaves. The infected with P. graminis. The optimum temperature for zoosporic fungi Lagena radicicola, Olpidium brassicae, transmission of the virus in soil, 15 C, is above the optimum Polymyxa graminis, Rhizophydium graminis, and Pythium for the development of the virus, 10 C, but within the lower spp. usually were present in the roots of plants infected from range of temperatures favorable for the development of P. soil, and in the roots of most plants in 10 sets infected graminis. successively by root association in sterilized sand. When Wheat spindle streak mosaic (WSSM) is widespread in transmission, and to determine if any of these fungi some years in most fields in areas of southern Ontario transmitted WSSMV. where winter wheat is grown most intensively (10). It has been reported in several central and northeastern States MATERIALS AND METHODS of the USA, in France, and recently in India (1, 14). It is Soil for most of the experiments reported here was a caused by a soil-borne virus, WSSMV, with very long, sandy loam collected at the Central Experimental Farm, filamentous particles, quite distinct from the short rod-Ottawa, from a field in which winter wheat had been like particles of soil-borne wheat mosaic virus (WSBMV) grown every 3rd yr starting in 1952. By 1967, plants with (4), which has not been found in Ontario and was not symptoms of WSSM were observed in this field. detected in any of the plants grown in soils used in these Subsequently winter wheat was planted each year to build experiments. up and maintain a high level of infectivity. The soil was Because a zoosporic fungus, Polymyxa graminis Led. collected in October, dried on a greenhouse bench, sifted has been associated with the transmission of WSBMV (4, to break down the lumps, and stored dry in a greenhouse 9), this fungus has been a prime suspect as a vector of where temperatures ranged from about 15 to 30 C. WSSMV. Although P. graminis usually has been found Winter wheat (Triticum aestivum 'Kent') was used as in the roots of wheat plants infected with WSSMV the test host and for multiplying the virus and culturing wherever the disease occurs, other fungi that infect wheat the zoosporic fungi. Wheat was infected from soil by roots in similar ways also generally are present, hence sowing 10-15 seeds in 7.5-cm diameter pots of the test soil, they also were suspect as vectors. One of these, Olpidium watering moderately, and growing at 15 C with about brassicae (Wor.) Dang., is a vector of several other viruses 12,000 lux of light for 12 hr per day, genereally for 21 (7). The other suspects included Rhizophydium graminis days, but...

No abstract

Agropyron mosaic virus (AMV) from Ontario and wheat streak mosaic virus (WSMV) from Alberta readily infected wheat (Triticum aestivum L.) causing mosaic symptoms that could be differentiated only when carefully compared. All isolates of AMV infected Agropyron repens (L.) Beauv. but not oats (Avena sativa L.). WSMV infected oats but not A. repens. Hordeum mosaic virus (HMV) from Alberta caused mottle rather than streak symptoms on wheat, rye, and other common hosts of WSMV, and did not infect A. repens, but, like AMV, it was not transmitted by Aceria tulipae (K.), the vector of WSMV. It infected Hordeum jubatum L., which is not susceptible to AMV or WSMV. It ranked between AMV and WSMV in longevity and tolerance to heat and pH. The particles were flexuous rods similar to those of WSMV, which appear less flexuous and slightly shorter than particles of AMV.The temperatures at which the viruses multiplied and caused symptoms on wheat ranged from 15° to 33 °C for WSMV and 10° to 30° for AMV. HMV multiplied at all temperatures from 10° to 33 °C but caused symptoms only at 10° to 30 °C.Specific antisera were prepared by partially purifying the viruses by differential centrifugation of juice from diseased wheat, emulsifying the juice with adjuvant, then injecting rabbits intramuscularly. The precipitation titers against their homologous viruses were 1/640, 1/1280, and 1/1280 for the WSMV, AMV, and HMV antisera respectively. The WSMV antiserum did not react with the heterologous viruses, but two HMV antisera had a precipitation titer of 1/16 against AMV, and an AMV antiserum had a titer of 1/10 againt WSMV. Cross absorption of each of the antisera with the heterologous viruses did not reduce the titers against the homologous viruses.The infection of wheat with a mild strain of any of the three viruses protected against later infection by a severe strain of the same virus. Both AMV and HMV were synergistic in combination with WSMV. Serological tests demonstrated that both AMV and HMV multiplied in wheat simultaneously inoculated with both viruses, but systemic infection with either virus protected the plants against later infection by the other.Despite general similarities in physical characteristics and effects on wheat, specific differences in other characteristics show that AMV, HMV, and WSMV are sufficiently different to be designated as different viruses rather than closely related strains of one virus.