A study of ethylene in apple, red raspberry, and cherry

High ethylene levels were associated with flower abscission in apple (Malus sylvestris) and cherry (Prunus avium and Prunus cerasus), “June drop” of immature cherries, and harvest drop of apple and red raspberry (Rubus idaeus). However, an increase in ethylene content was not associated with June drop of apples and harvest drop of cherries. During the period of fruit ripening on the plant, the largest increases in ethylene occurred in apple flesh and red raspberry receptacular tissue. Ethylene remained low throughout the period of sweet and tart cherry ripening. The data obtained indicated marked ethylene gradients between adjacent tissues. Increases of ethylene in some tissues may have resulted from ethylene diffusion from adjacent tissues containing high levels of ethylene.     

A comparison of some properties of four strains of cherry leaf roll virus

The elm mosaic and golden elderberry strains of cherry leaf roll virus (CLRV) and a strain from cherry and from rhubarb were very similar in their host range, symptomatology and properties in vitro. However, only the rhubarb isolate infected rhubarb systemically and only the golden elderberry isolate infected Sambucus nigra systemically. Purified preparations of all strains contained isometric particles which sedimented as two nucleoprotein components with sedimentation coefficients of about 115 S and 128 S. The elm mosaic strain was the least stable in vitro and was the most difficult to purify. In plant-protection tests, one-way protection occurred between tomato ringspot virus and each of the four CLRV strains. However, whereas the elm mosaic, golden elderberry and the cherry strains protected against one another, they did not protect against infection with the rhubarb strain.     

Some properties of an isolate of tobacco rattle virus from Northern Ireland

A virus obtained from soil in which potato plants had shown severe spraing symptoms induced symptoms on indicator plants typical of tobacco rattle virus (TRY). Purified virus preparations of a local-lesion isolate contained particles of two modal lengths, 192 nm and 94 nm containing RNA molecules of mol. wt 2.4 × 10⁶ and 1.23 × 10⁶. Virus coat protein had a mol. wt of c. 21 500. The virus was serologically distantly related to TRY (SYM) and pea early browning virus (PEBV) SP5, but did not react with TRY (CAM) or TRY (PRN) antisera. However, cDNA hybridisation indicated that the virus was more closely related to TRY (PRN) than either TRY (SYM) or PEBV (SP5). The virus isolate has been designated TRY (NI).     

The influence of FeEDDHA in red raspberry cultures during shoot multiplication and adventitious regeneration from leaf explants

We examined the effect of FeEDDHA on multiplication via axillary branching and adventitious shoot regeneration from leaf explants in five red raspberry cultivars. When applied during multiplication, FeEDDHA reduced chlorosis, increased content of chlorophyll and iron but had no effect on the number of side shoots in four of the five cultivars. Addition of FeEDDHA to regeneration medium increased the percentage of regenerating leaves in some cultivars and the number of adventitious shoots in all five cultivars.     

Biological properties,transmission, serological characterization and varietal susceptibility of an isolate of Papaya leaf curl virus affecting papaya crops in Eastern Uttar Pradesh,India

Papaya leaf curl disease (PLCD) was recorded with 5–35% incidence at six districts of Eastern Uttar Pradesh during survey. The characteristic symptoms observed were severe downward leaf curling, swelling of veins, twisting and reduction of petioles, inverted leaf bowls and stunted growth of the entire plant which bore only few small and distorted fruit. The virus isolate was identified as Papaya leaf curl virus (PaLCuV).The PaLCuV isolate was successfully transmitted by whitefly (Bemisia tabaci) but not by mechanical (sap) transmission on Carica papaya plants. Plants could be proved efficiently from infected to healthy C. papaya, Capsicum annuum, Lycopersicon esculentum, Nicotiana tabacum, Crotalaria juncea, Ageratum conyzoides, Zinnia elegans, Datura stramonium and Petunia hybrida. Symptomatic samples of these plants were tested with polyclonal antiserum of Tomato leaf curl New Delhi virus by DAC-ELISA test showed the positive relationship of the samples with geminivirus. On the basis of symptomatology, whitefly transmission, host range studies and serological relationship, the isolate was identified as whitefly transmitted geminivirus. To identify potential varietal resistances source to PaLCuV, five cultivars of C. papaya were tested against PaLCuV using whitefly insects to transmit the infection. Results revealed that two cultivars (Washington and Ranchi Dwarf) were found to be moderately resistant.     

Properties of an unusual isolate of raspberry ringspot virus from grapevine in Germany and evidence for its possible transmission by Paralongidorus maximus

An isolate of raspberry ringspot nepovirus (RRV-P) commonly found infecting grapevine in localised areas of the German Palatinate, was serologically closely related to, but distinguishable from, the English type strain of this virus (RRV-E) which is transmitted by Longidorus macrosoma. However, unlike RRV-E, RRV-P had a restricted herbaceous host range and produced symptoms reliably in only two hosts, Chenopodium quinoa and Nicotiana occidentalis-accession 37B: these symptoms were a faint systemic vein clearing which, on most occasions in C. quinoa, was transient. In in vitro studies with herbaceous plant sap, RRV-P infectivity was lost after diluting 1/100 -1/500, after storage at 20^oC for 1–3 days and at 4^oC for 45 days: for similar studies with RRV-E, the values were 1/125 000, and more than 15 days at 20^oC and 4^oC, respectively. RRV-P was difficult to purify in quantity and in most preparations seemed to sediment as a single component corresponding to ‘bottom’ component of RRV-E. Purified particles of RRV-P, like those of RRV-E, contained a major polypeptide and two RNA species of M_r 54 000, 2.6 times 10⁶and 1.6 times 10⁶respectively. There was no evidence from RNA preparations from purified virus particles or, from analysis of dsRNA from infected plants, that RRV-P contained a satellite RNA. The incidence of RRV-P in vineyards was not associated with the presence in soils of Longidorus nematodes, but was associated with the distribution in the Palatinate of Paralongidorus maximus. Furthermore, results from an experiment in Germany in a vineyard planted with healthy grapevines in soil fumigated to destroy nematodes, showed spread of RRV-P into these plants from an adjoining source of infected grapevines and soil infested with P. maximus. In laboratory studies, RRV-P was transmitted by P. maximus at a very low level between grapevines (used as the virus source and test plants) but not to, or between, herbaceous hosts.     

Properties of an unusual isolate of raspberry ringspot virus from grapevine in Germany and evidence for its possible transmission by Paralongidorus maximus

An isolate of raspberry ringspot nepovirus (RRV-P) commonly found infecting grapevine in localised areas of the German Palatinate, was serologically closely related to, but distinguishable from, the English type strain of this virus (RRV-E) which is transmitted by Longidorus macrosoma. However, unlike RRV-E, RRV-P had a restricted herbaceous host range and produced symptoms reliably in only two hosts, Chenopodium quinoa and Nicotiana occidentalis-accession 37B: these symptoms were a faint systemic vein clearing which, on most occasions in C. quinoa, was transient. In in vitro studies with herbaceous plant sap, RRV-P infectivity was lost after diluting 1/100-1/500, after storage at 20^oC for 1–3 days and at 4^oC for 45 days: for similar studies with RRV-E, the values were 1/125 000, and more than 15 days at 20^oC and 4^oC, respectively. RRV-P was difficult to purify in quantity and in most preparations seemed to sediment as a single component corresponding to ‘bottom’ component of RRV-E. Purified particles of RRV-P, like those of RRV-E, contained a major polypeptide and two RNA species of Mx 54 000, 2.6 × 106 and 1.6 × 106 respectively. There was no evidence from RNA preparations from purified virus particles or, from analysis of dsRNA from infected plants, that RRV-P contained a satellite RNA. The incidence of RRV-P in vineyards was not associated with the presence in soils of Longidorus nematodes, but was associated with the distribution in the Palatinate of Paralongidorus maximus. Furthermore, results from an experiment in Germany in a vineyard planted with healthy grapevines in soil fumigated to destroy nematodes, showed spread of RRV-P into these plants from an adjoining source of infected grapevines and soil infested with P. maximus. In laboratory studies, RRV-P was transmitted by P. maximus at a very low level between grapevines (used as the virus source and test plants) but not to, or between, herbaceous hosts.     

Biological properties of phospholipase C purified from a fleecerot isolate of Pseudomonas aeruginosa

A role for one of many exocellular enzymes produced by Pseudomonas aeruginosa--phospholipase C (PLC)--as a prime candidate virulence factor in fleecerot dermatitis has been examined. The addition of Tween 80 in tryptose minimal medium effectively perturbed the membrane system of a field isolate of P. aeruginosa, resulting in increased production and release of a periplasmic enzyme marker, alkaline phosphatase (AP), and also of PLC. PLC activity levels in the culture supernatant were 10- to 15-fold higher in the presence of Tween than in its absence. Apart from AP, the culture medium contained little or no detectable proteolytic enzyme activity, thereby facilitating the partial purification of a haemolytic form of PLC by anion-exchange chromatography. This enzyme, when injected intradermally into the skin of sheep, elicited histopathological lesions virtually identical to those seen in naturally occurring fleecerot. In addition, serum from each of eight sheep afflicted with fleecerot contained high levels of circulating anti-PLC antibody activity when assayed by ELISA. Since these antibodies did not affect the enzymic function of PLC, it is likely that they do not bind to, or are incapable of conformational modification of, the active site.     

Ultrastructure and cytochemistry ofPhaseolus leaf tissues infected with an isolate of tobacco necrosis virus inducing localized wilting

Summary The cytopathology induced by an isolate of tobacco necrosis virus (TNV-W) causing wilted, non-self-limiting lesions inPhaseolus bean was compared with that of abiotically-induced wilting. The main cell alterations specific to TNV-W infection were ER proliferation and vesiculation, plasmolysis and plasmalemma proliferation. Later there was lysis of most cell membranes, formation of crystalline inclusions in the chloroplasts and development of fibrous structures in the cytoplasm. It is suggested that the chloroplast inclusions consist of ribulose-1,5-bisphosphate carboxylase (RuBisCo). TNV-W replicated extensively in infected cells, often forming large crystalline aggregates of virus particles. Tissue wilting, as well as crystallization of the virus and RuBisCo, may have been caused by cell dehydration due to the loss of plasmalemma integrity.Abbreviations CA chromic acid - CI crystalline inclusion - DG dense granule - E ethanol - ER endoplasmic reticulum - FS fibrous structure - H₂O₂ hydrogen peroxyde - MVB multivesicular body - Pb lead citrate - PTA phosphotungstic acid - RuBisCo ribulose-1,5-bisphosphate carboxylase - TNV-W tobacco necrosis virus-wilting - UA uranyl acetate     

Further studies on the occurrence and inheritance of resistance in red raspberry to a resistance-breaking strain of raspberry bushy dwarf virus

A strain of raspberry bushy dwarf virus (RBDV-RB), discovered in England in 1981, readily infects by grafting many raspberry cvs that have gene Bu, which confers strong resistance or immunity to isolates of the common strain. Haida is one of two cultivars that are highly resistant or immune from RBDV-RB, but both its parents, cvs Creston and Malling Promise, are infectible. Studies of the segregation of resistance to both RBDV-RB and a common strain of RBDV (D200) in four progenies related to cv. Haida or its two parents, showed that resistance to RBDV-RB was heritable and occurred when gene Bu was present with a second resistance component whose inheritance is probably multigenic. There was some indication that the second component might be a form of partial resistance to graft inoculation of varying expression, and that cv. Haida possesses this resistance at a high level that has not been distinguished from immunity in the graft inoculations used. Cultivars Creston and Malling Promise possibly have this resistance to a lesser degree, while resistance in cv. Heritage has been distinguished from immunity only by extensive graft tests. Some possible implications for breeding RBDV-RB resistant cultivars are discussed.     

Ultrastructural, biochemical and biophysical properties of an erythrocytic virus of frogs from Ontario, Canada

Frog erythrocytic virus (FEV), one of the largest icosahedral viruses, is enveloped, measures up to 450 nm in diameter, and contains double stranded DNA. The virus is found in the cytoplasm of erythrocytes of Rana catesbeiana, Rana septentrionalis, and Rana clamitans from Algonquin Park, Ontario (Canada). Acidophilic inclusions in infected erythrocytes stained with Giemsa's stain correspond to viroplasms from which FEV buds and forms aggregates of virus particles as seen in the electron microscope. Frog erythrocytic virus appears to acquire its envelope from lamellar membranes which surround the virus particles. The virus is structurally sensitive to cesium chloride, potassium tartrate and glycerol. It is also sensitive at pH 1 to 5 and a temperature of 56 C for 15 min. The virus contains at least 16 proteins which range in relative molecular mass from 19.5 to 91.0 kilodaltons (kDa), with two major proteins of 31.0 and 43.0 kDa. The viral DNA has a buoyant density of 1.690 +/- 0.005 g/ml, guanine plus cytosine ratio of 25 to 36%, and a melting temperature of 82 to 86 C. Data from this study indicate that FEV should be included in the family Iridoviridae.     

Immunity from raspberry vein chlorosis virus in raspberry and its potential for control of the virus through plant breeding

The apparent immunity of five cultivars of red raspberry and two of black raspberry from graft inoculation with raspberry vein chlorosis virus (RVCV) was established or confirmed. The segregations obtained from selfs and crosses with infectible cultivars of four of the red raspberry cultivars and the black raspberry cultivar Cumberland indicated that the apparent immunity was not determined by a single major gene. The range in severity of the symptoms expressed in the segregates suggested either that sensitivity to infection is under separate genetic control, or that immunity and sensitivity are opposite expressions of a character which varies continuously rather than discontinuously. Nevertheless, although the precise mechanism of immunity remains unclear, the high proportion of immune segregates obtained in crosses indicated that breeding for immunity from RVCV is feasible and offers the best prospect for control of the virus.     

Thermal inactivation of cherry leaf roll virus in tissue cultures of Nicotiana rustica raised from seeds and meristem-tips

Nicotiana rustica tissue cultures derived from seeds or embryos infected with cherry leaf roll virus (CLRV), remained infected after culture at 22 ^oC. No infectivity was found in cultures held at 32 ^oC for 5 days but it was readily detected after such cultures were transferred to 25 ^oC for 8 days. Virus was permanently eradicated from most plants after 20 days incubation at 32 ^oC and from all plants after 7 days incubation at 40 ^oC. Partially purified preparations of CLRV lost infectivity after 9–12 days at 22^oC, 5 days at 32^oC and 3 days at 40^oC.     

Rubus host range, symptomatology and ultrastructural effects of a British isolate of black raspberry necrosis virus

Scions from red raspberry (Rubus idaeus) plants naturally infected with an aphid- and sap-transmissible virus, code-named 52V, always induced apical necrosis in R. occidentals signifying the presence of black raspberry necrosis virus (BRNV), whereas plants free from 52V did not. These and other findings provide strong circumstantial evidence that 52V is an isolate of BRNV, the heat-labile member of the pair of viruses that together cause raspberry veinbanding mosaic disease. On grafting with R. idaeus scions containing a 52V culture of BRNV free from other detectable viruses, all of twenty-two red raspberry cultivars and four other Rubus species were infected symptomlessly but apical necrosis developed in R. henryi and R. molaccanus. Electron microscopy of thin sections of 52V-infected Chenopodium quinoa, R. henryii and R. occidentalis showed areas of dead cells in the vascular tissue and leaf blade. Some of the cells adjacent to these areas had cell wall outgrowths and many of the plasmodesmata contained virus-like particles c. 25 nm in diameter arranged in a single file.     

Comparison of ELISA and immunoblotting techniques for the detection of cherry mottle leaf virus

Formaldehyde treated cherry mottle leaf virus (ChMLV) and the isolated coat protein were used successfully for the production of polyclonal and monoclonal antibodies. The monoclonal antibodies had a titre of 1:51 200 and consisted of IgG1 and IgG2. The antibodies reacted with all 11 isolates of ChMLV, from five locations in Canada and the USA, included in this study. Several serological procedures were assessed to compare their sensitivity for detecting ChMLV. Plate-trapped antigen ELISA (PTA-ELISA) and dot-blot immunobinding assay (DBIA), using virus specific MAbs, were the most sensitive tests in this study. Triple antibody sandwich ELISA (TAS-ELISA) and Western blot were found to be less sensitive. Dilution of the samples appeared to increase the sensitivity of both PTA-ELISA and Western blot detection. Young leaves and flowers of Prunus avium were the best tissue for detecting the virus which could also be detected in the fruit and leaves of P. tomentosa. April and May were optimal for detection of the virus in the field, whereas both April to May and August to September were optimal for screenhouse-grown plants.