Potato Leafroll Virus Infection Research Articles

Use of IKI leafroll test to reduce net necrosis storage losses of potatoes

An iodine-potassium-iodide (IKI) starch staining procedure was adapted for use on potato plant leaflets to estimate the frequency of potato leafroll virus (PLRV) infection in potato fields prior to harvest. Large increases in the percentage of tubers with net necrosis occurred during storage among tubers from fields with high PLRV infection rates. Such fields were reliably identified prior to harvest by the IKI test, so their tubers could be processed at harvest to avoid net necrosis storage losses. The test could be performed on hundreds of samples per hour by untrained personnel with commonly available equipment. PLRV infection frequency varied widely in Columbia Basin potato fields. Most infected plants expressed no symptoms but could be detected by the IKI test before harvest. High rates of virus dissemination apparently occur late in the growing season in the Columbia Basin

Volunteer potatoes as a source of potato leafroll virus and potato virus X

Volunteer potatoes were investigated as infection sources for potato leafroll virus (PLRV) and potato virus X (PVX) in a high elevation seed potato growing area of eastern Idaho. Population densities ofMyzus persicae were assessed. Percentage of PLRV and PVX infection of the volunteers and seed potato crops was determined, as well as density of volunteers and certain parameters of volunteer growth and reproduction. Volunteers apparently harbored no more PLRV than the potato crop from which they originated. But they were found to be an important reservoir of PVX with the infection increasing as much as 12.43% in one year. No aphids capable of transmitting PLRV were found although one species that can transmit potato virus Y was recorded. The mean density of volunteers varied from 0 to 84,880 stems/ha. The number of tubers remaining in the field after harvest and winter weather conditions appeared to be the only factors affecting volunteer density. Volunteer plants arising from seed pieces at an average depth of 6.1 cm were found to set an average of 2.1 new tubers per plant at an average depth of 4.0 cm. These results suggest that volunteer potatoes are a significant source of PVX infection in subsequent seed potato crops.

Reducing potato leaf roll virus (PLRV) in potato by means of baiting aphids to yellow surfaces and protecting crops by coarse nets

Surrounding half of the perimeter of potato plots with sticky yellow polyethylene sheets (HPS) stretched vertically at a height of 0.6 m above the soil, reduced the number, of winged aphids by ca. 70% and of PLRV infection by ca. 38%. A YPS mulch cuased an increase in aphid population, PLRV incidence and percentage of misshapen tubers.

Testing for mild leafroll in Maine

Field and greenhouse readings in Maine together with test plot readings in Florida showed the incidence of potato leafroll virus infection in 10 Kennebec seed lots from south, central and northern Aroostook County to be about 1.2%. When the seed lots were indexed by aphid transmission of the virus toPhysalis floridana Rydb. in January and July the incidence of leafroll was found to be 2% and 10% respectively. SinceP. floridana detects mild strains as well as those capable of causing visible symptoms on potato, these results indicate that mild strains are present in the Kennebec variety being grown for seed in Aroostook County. The authors indicate, however, that leafroll symptom expression inP. floridana, in many instances, was not definitive and they suggest that their data may reflect an inaccurate estimate of the prevalence of mild strains of leafroll in Maine.

Control of the Green Peach Aphid and Its Effect on the Incidence of Potato Leaf Roll Virus1

Although several insecticides provided excellent control of Myzus persicae (Sulzer), none prevented the occurrence of potato leaf roll virus (PLRV) infection duro ing 4 yr of experimentation. There appeared to be no correlation between populations of apterous aphids in treated plots during a given year and the occurrence of PLRV infection in tubers from the plots. The overall incidence of PLRV infection was highest in years of the greatest aphid populations but appeared to be correlated with the numbers of winged aphids as indicated by catches in Moericke traps.

A rapid electron microscopic diagnosis of potato leafroll virus

Particles of potato leafroll virus (PLRV) can be concentrated by ultracentrifugation of homogenates of sprouting tubers and seen in the electron microscope. In contrast to staining with resorcin blue and survey of symptoms in eye-cuttings — methods based on phenomena associated with PLRV infection — the electron microscopic method (EM) is direct, as it demonstrates the virus itself. The method differentiates clearly between PLRV-carrying and PLRV-free tubers, and leaves fewer doubtful cases than the other methods. Only one gram of tissue is required from each tuber. The same procedure detects but does not by itself differentiate among other viruses like potato virus X, Y, A, S, M and tobacco rattle virus, all having elongated particles. The procedure for diagnosis of PLRV in EM is significantly quicker than the eye-cutting test, reducing the time frm weeks to hours. Its results are reproducible enough to be recommended for routine diagnosis of PLRV.

Phosphorus disturbances associated with potato leafroll virus infection

Potato leafroll virus induces considerable disturbances of phosphorus metabolism in leafroll-infected potato plants. Each variety reacts differently in this respect on the infection, to some extent being dependent on the susceptibility of the respective variety to leafroll and to the season as well. In varieties particularly susceptible to leafroll as in Apta and Sieglinde there is a decrease of total P after infection. On the contrary, varieties showing medium susceptibility such as varieties Tatranka, Rita and Ambra react to leafroll infection with a considerable increase of total P. In the comparatively less susceptible variety Krasava, there is no change in the level of total P after infection. In autumn, however, a slight decrease of total P even in the medium susceptible variety Tatranka, and the less susceptible variety, Krasava, can be found. Our results shed a new light on existing controversies in literature regarding phosphorus content in leafroll-infected potato plants.

Branch-trace necrosis, a symptom of potato leafroll virus infection

Branch-trace necrosis, a symptom of potato leafroll virus infection