Mechanical transmission of Potato leafroll virus (original) (raw)
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Purification and electron microscopy of potato leafroll virus
Virology, 1969
A procedure for purification of potato leafroll virus (PLRV) from its plant host was improved. An extract from diseased Physalis $oridana plants was emulsified with an n-butanol-chloroform mixture. The virus in the aqueous phase was concentrated by centrifugation, the pellet was resuspended in 0.01 M phosphate buffer and subjected to emulsification with fluorocarbon (Daifron S-3). The virus, concentrated by additional centrifugation from the aqueous phase, was fractionated in a sucrose densitygradient column. When the final preparation was suspended in 0.01 M phosphate buffer at pH 6.0 and negatively stained by 2oJ, PTA at pH 5.5, the resulting suspension contained uniform particles 25 rnp in diameter (side by side) and with more or less hexagonal profiles. High infectivity was associated with the zone containing these particles. Preparations obtained from healthy plants and virus-free aphids by the same purification procedure did not contain these particles. Examination of ultrathin sections of the infected P. JEoridana and Datura stramonium plants by electron microscopy indicated that the virus occurred in some of the phloem cells. When PLRV particles were measured in crystalline array in ultrathin sections the size obtained (23 rnp diameters) agreed approximately with that of the purified virus particles.
Characterization of potato leafroll virus
1980
Potato leafroll virus (PLRV) was purified from infected potato (Splanum tuberosum L.) by using a mixture of chloroform and-"butanol for clarification and polyethylene glycol for concentration. The virus sedimented as a single band in a sucrose density gradient. Yield of purified virus varied from 0.4-0.6 mg/kg fresh weight of potato foliage. Virus yield was higher from tissue immediately processed after harvest than from tissue stored at 4 C or-20 C for a day or longer. The A 260/A 280 varied from 1.74-1.82. Antiserum prepared against purified virus had a maximum titre of 1024 in agar gel double diffusion tests. PLRV in unconcentrated potato sap could not be detected by agar gel tests, but could be detected by enzyme-linked immunosorbent assay. A pure line of the mild strain of PLRV was isolated, and an antiserum with a maximum titre of 2560 by agar gel tests was produced. PLRV had a sedimentation coefficient of 127 S by linear log sucrose density gradient centrifugation and 117 S by analytical ultracentrifugaition. A buoyant density of 1.38-1.39 g/cm was obtained from isopycnic centrifugation in cesium chloride and analytical ultracentrifugation in cesium sulphate. The nucleic acid content of PLRV was estimated from the particle densities to be 26-28%. The PLRV nucleic acid had:, a moi wt of 2.0 x 10^; was degraded by RNase but not by DNase; reacted with orcinol but not with diphenylamine; and had a broad range of melting temperatures from 35 to 85 C in 1 x SSC buffer with hyperchromicity of 20-21%. These properties indicated that PLRV nucleic acid is a single-stranded RNA. The sedimentation coefficient of the RNA molecule before and after treatment with formaldehyde was 34.5 S iii and 20.7 S, respectively. Dissociated coat protein migrated as a single band in polyacrylamide gel electrophoresis and the average subunit moi wt was 26 300-PLRV should be considered a member of the luteovirus group.
Resistance to phloem transport of potato leafroll virus in potato plants
Journal of General Virology, 1992
A 'double-graft sandwich' technique in which sections of potato stem from different potato cultivars were grafted between a susceptible healthy stock plant and a potato leafroll virus (PLRV)-infected scion was used to study the rate of phloem transport of PLRV in cultivars differing in resistance to PLRV infection (I R) and accumulation (AR). Resistance to phloem transport (i.e. delayed PLRV systemic movement) was found in Bismark cultivar (I R AS). This was independent of I R and A R as the rate of movement in Bismark cultivar was markedly slower than that in Omega and Spunta (I R AR), Delaware (I s AR), and Desiree and Renova (I s A s) cultivars. It operated in Bismark cultivar stems of two different ages, but did not operate against potato virus X (PVX) and was not influenced by previous infection with this virus. Aphid vector (Myzuspersicae) feeding preferences and colonization rates differed between cultivars, but the cultivar characteristics responsible were unrelated to I R, A R or resistance to phloem transport. Delayed systemic movement of PLRV out of leaves inoculated with viruliferous aphids was independent of A R and resistance to phloem transport, and remained unaffected by previous infection with PVX. It was also independent of cultiwlr factors causing different aphid feeding preferences and colonization rates, but may be linked to I R.
Journal of general …, 1997
The aphid Myzus persicae (Sulz.) was shown to transmit potato spindle tuber viroid (PSTVd) to potato clone DTO-33 from source plants doubly infected with potato leafroll virus (PLRV) and PSTVd. Transmission was of the persistent type and did not occur when the insects were allowed to feed on singly infected plants. Only low levels of PSTVd were associated with purified PLRV virions, but its resistance to digestion with micrococcal nuclease indicates that the viroid RNA is encapsidated within the PLRV particles. Epidemiological surveys carried out at three locations in China revealed a strong correlation between PSTVd infection and the presence of PLRV, suggesting that PLRV can facilitate PSTVd spread under field conditions. Like all known viroids, potato spindle tuber viroid (PSTVd) is an independently replicating agent which completes its infection cycle without generating either a capsid or other viroid-specific proteins. Its genome is a small (359 nt), singlestranded, covalently closed circular RNA molecule whose extensive regions of intramolecular complementarity are responsible for its unusual stability in vivo (Sa$ nger et al., 1976 ; Riesner, 1987). In potato, natural spread of PSTVd has been repeatedly shown to occur either by foliar contact (Goss, 1926 ; Merriam & Bonde, 1954) or botanical seed (Hunter et al., 1969). Early reports (Goss, 1930) suggested that PSTVd might be transmitted by chewing-insects, but these reports have not been confirmed. De Bokx & Piron (1981) reported a low rate of transmission by the aphid Macrosiphum euphorbiae (Thomas) but no transmission was obtained with either Myzus persicae (Sulz.) or Aulacorthum solani (Kaltenbach). In contrast to PSTVd, potato leafroll virus (PLRV ; a member of the genus Luteovirus) is readily aphid transmitted, M. persicae being the most efficient natural vector (Goss, 1930). Like all luteoviruses, PLRV is restricted to the phloem tissue of
Annals of Applied Biology, 2008
The potato clone G8107(1) has been identified as resistant to both PLRV infection and multiplication. In this study, attempts were made to reveal the mechanism(s) involved in the resistance of this clone to PLRV infection. Considering the existence of a rigid cell wall as a passive resistance barrier or mature-plant resistance as barrier to virus infection, experiments were conducted in which softer tissues of this potato clone (sprouts and in vitro propagated plantlets) were aphid inoculated with PLRV. The results indicated that aphid inoculation of both tissue types of this potato clone with PLRV did not lead in breakdown of its resistance to virus infection. Therefore, it was concluded that the resistance of this clone to PLRV infection via aphid inoculation is not associated with the existence of a rigid cell wall or mature-plant resistance. It is suggested that the observed resistance might be due to the PLRV replication failure in the tissues of this potato clone, or inability of the virus to transport from the initially infected cells and or, somehow, degradation of the virus particles after replication. However, it seems that this very strong resistant potato clone is an excellent choice to be exploited in PLRV resistance breeding programs.
Euphytica, 1992
Degeneration of seed tubers caused by viruses is a major constraint to potato cultivation in many warm tropical areas. Cultivars resistant to the most important viruses present a promising solution to such a problem. In a breeding study conducted at the International Potato Center (CIP), ten cultivars resistant to PLRV were crossed to five clones immune to PVX and PVY, as well as to a susceptible control. The resulting progenies were screened for PVX and PVY immunity. Afterwards, the resistant genotypes were fieldexposed to a PLRV-viruliferous aphid population. One tuber was harvested from each plant and used to assess, using ELISA serology, the presence of leafroll virus. The cultivars Serrana and Pentland Crown gave the best progenies in terms of percentage of healthy plants, with values of 47 .4 and 33 .3 respectively. The presence of joint infection of PLRV and PVY or PVX in the progenies of the susceptible control resulted in an increased susceptibility to leafroll .
American Journal of Potato Research, 2005
The effects of Potato leafroll virus (PLRV) isolates and inoculation method on the resistance to PLRV in potato clones and cultivars were investigated. In the season of inoculation, aphid inoculation resulted in higher proportions of infected plants and higher virus concentration in infected plants, as compared to graft inoculation. In these respects, grafting showed superiority over aphid inoculation in the tuber progeny of inoculated plants, though distinct dominance of aphid inoculation was observed for some tested clones. This leads to the conclusion that both methods should be applied as complementary tests for the efficient selection of highly resistant potato clones. For inoculations, two isolates of PLRV were applied, and one of them, isolate L7, was routinely used in screening breeding materials for resistance to the virus. The second isolate originated from plants of the highly resistant clone DW84-1457, which were incidentally infected with PLRV. The virus isolated from these Amer J of Potato Res (2005) 82:411-417 411
Australian Journal of Agricultural Research, 1993
A selection of potato cultivars and breeding lines was evaluated for presence of resistance to infection with potato leafroll virus (PLRV) via viruliferous aphid vectors ( I~) and/or resistance to accumulation of PLRV antigen ( A~) in infected leaf tissue. Cultivars Aracy, Delcora, Omega and Spunta, and breeding lines BR63.15 and B71.240.2 carried both and AR , Bismark, Serrana INTA and L/T1 had alone and Delaware had AR alone. The other cultivars tested had neither. Within both the resistant and susceptible classes for AR, the level of PLRV antigen accumulation achieved varied with cultivar. Previous infection with potato virus X (PVX) or potato virus S (PVS) either alone or together did not diminish the expression of or AR. However, the presence of PVX sometimes significantly increased the accumulation of PLRV in susceptible cv. Desiree and this effect was most pronounced in mature leaves of older plants. In contrast, presence of PVX in susceptible cv. Desiree did not increase the numbers of plants becoming infected with PLRV. Identifying potato genotypes with