Effects of mist irrigation on the physiology of sugar beet

Bacilliform particles characteristic of plant rhabdoviruses were found in negatively-stained leaf sap and in thin sections of Laburnum anagyroides in England showing vein yellowing. The particles were detected principally in the perinuclear space of parenchyma cells. They were not transmitted by sap inoculation to twelve herbaceous species. The affected trees also showed mosaic symptoms but there was no evidence of an association between these and the bacilliform particles.     

Association of different kinds of bacilliform particle with vein chlorosis and mosaic diseases of raspberry (Rubus idaeus)

Thin sections of diseased raspberry (Rubus idaeus) were examined by electron microscopy. Plants of the cv. Baumforth's B and of an aphid (Amphorophora rubi)-resistant breeding selection (6820/54), both infected with raspberry vein chlorosis virus (RVCV) but not with other detectable viruses, contained large bacilliform particles c. 430 × 65 nm. Particles occurred in the cytoplasm and perinuclear space of a small proportion of xylem parenchyma cells. They had an inner core c. 25–30 nm in diameter with cross-banding of periodicity 4·5 nm, and were bounded by an outer membrane. They are probably the particles of RVCV. Plants of cv. Mailing Jewel and of a selection (M14) both showing symptoms of raspberry mosaic (veinbanding) disease contained smaller bacilliform particles c. 125 × 30 nm, which occurred singly or in clusters in the cytoplasm of a small proportion of vascular parenchyma cells. It is not known which, if any, of the viruses associated with raspberry mosaic are represented by the particles.     

Morphology and development of rhabdovirus-like particles inCuscuta odorata (Convolvulaceae) simultaneous infected with virus and mycoplasma-like organisms

Summary Electron microscopic examination ofCuscuta odorata, used for transmission trials, revealed mycoplasma-like organisms (MLO) as well as rhabdovirus-like particles, unknown toCuscuta. The virus infection is confined to certain phloem-parenchyma cells and a 1–2 cell thick layer of parenchyma cells with thickened walls surrounding the central cylinder. Virus particles, mostly bacilliform, could be detected mainly in the nucleus but also in the cytoplasm. They reach a length of 350–400 nm and a diameter of approximately 75 nm. Virus assembly takes place exclusively in the nucleus. Virus maturation occurs in membrane bound areas within the nucleus, which have no connection with the perinuclear space. Formation of nucleocapsids is always associated with a nuclear viroplasm. Envelopment of virus particles occurs in these membrane bound areas. Budding into the perinuclear space does not occur. Virus infection leads to degeneration and finally to death of the protoplast.Abbreviations cy cytoplasm - m membrane stacks - mt mitochondria - my mycoplasma-like organisms - nc nucleocapsid - ncp nucleocapsid particles - nf nuclear filaments - np nucleoplasm - nu nucleus - nvp nuclear viroplasm - oc obliterated cells - p plastid - pc passage cells - ph phloem - ps perinuclear space - spc strand of parenchymatous cells - v virus particle - x xylem     

Rhabdoviruses in Mentha piperita

Bacilliform and bullet-shaped particles measuring 360 × 80 nm and 180x 80 nm respectively, were found in the perinuclear space of parenchymatous cells in the vascular bundles of leaves, or roots of Mentha piperita. All particles contained bullet-shaped, electron dense cores and were enveloped by a unit membrane with spikes on its surface. The typical morphology and the intracellular occurrence of these particles leads us to the conclusion that they are rhabdoviruses.     

Rhabdovirus-like and closterovirus-like particles in ultrathin sections of Ribes species with symptoms of blackcurrant reversion and gooseberry veinbanding diseases

In attempts to determine the causal agents of blackcurrant reversion (BCRD) and gooseberry veinbanding (GVBD) diseases of Ribes species, details of the ultrastructure of different kinds of tissue from plants affected with these different diseases were studied. In three of 12 blackcurrant plants affected with BCRD, leaves and flowers of plants showing symptoms typical of the severe (R) form of the disease, contained rhabdovirus-like particles c. 65–80 nm × 215–485 nm. They were seen most often in the nucleus of cells as single particles but were also found in clusters or rafts. In leaves, these virus-like particles (VLPs) were present only in cells associated with the xylem parenchyma where they occurred as membrane-bound clusters within the nucleus. In flowers, they were also found in phloem parenchyma cells in the peripheral cytoplasm and very occasionally in the cytoplasm of epidermal cells. All non-nuclear VLPs were membrane-bound, either singly or in groups and the membrane seemed to be part of the endoplasmic reticulum. The proportion of vascular cells containing these VLPs was very low (< 1%). In a few cells, smaller bacilliform particles, c. 40–50 nm × 200–250 nm, were found in the nucleus together with the larger particles. Double-membrane bodies, detected in fig leaves affected with fig mosaic (the agent of which is also mite-transmitted), were not detected in any BCRD-affected plants. In leaf tissue of one of three gooseberry and one of two blackcurrant plants affected with GVBD, two kinds of VLPs were found. Rhabdovirus-like particles, similar to those in BCRD-affected material, were present in the nuclei, perinuclear space and cytoplasm of xylem parenchyma cells. They were c. 60–72 nm × 155–230 nm but there was no evidence of the smaller rhabdovirus-like particles detected in a few cells of BCRD-affected tissues. The second kind of VLP was found in noncrystalline masses, with a mean centre-centre spacing of c. 10 nm, in the cytoplasm of phloem cells. These particles, together with other ultrastructural changes, were typical of those reported for aphid-transmitted closteroviruses. No badnavirus-like particles, reported previously from GVBD-affected plants, were observed in any of the plants studied. The significance of these findings in relation to these two important diseases of commercial Ribes species is discussed.     

Characterisation of datura yellow vein virus, a newly described rhabdovirus from Australia

A previously undescribed sub-group 2 rhabdovirus was isolated in Queensland from Datura stramonium with symptoms of vein yellowing, leaf distortion and reduced leaf size. Particles accumulated in the perinuclear space of infected cells of D. stramonium and measured 77 × 166 nm in preparations from sap. The virus was named datura yellow vein virus (DYVV) and was graft-transmitted to several hosts in the Solanaceae including Lycopersicon esculentum, Nicotiana tabacum and Solanum melongena, but not to Capsicum annuum or Solanum tuberosum. DYVV was not transmitted by mechanical inoculation and no insect vector was found. Purified particles of DYVV contained four structural proteins with molecular weights of about 78, 47, 41 and 36 kd. The 78 kd protein bound the lectin concanavalin A, thus identifying it as the viral glycoprotein. DYVV was serologically distinct from 11 other rhabdoviruses belonging to both subgroups, including potato chlorotic stunt, potato yellow dwarf (2 isolates) and tomato vein yellowing viruses. The glycoprotein only of DYVV cross-reacted with a polyclonal antiserum to sonchus yellow net virus.     

The influence of ammonia in nutrient solution on growth and metabolism of cucumber plants

Summary Shoot yield of cucumber plants grown 18 days in nutrient solution with 0.06 mM NH₃ was decreased. Root yield was diminished at 0.09 mM NH₃ The ammonia treatment caused heavy chlorosis increasing with age of leaves. This chlorosis was not due to any nutrient deficiency. Ammonia also influenced the morphology of roots. They were clearly shorter caused by a much smaller size of root cells.The decrease of yield was linked to a reduction of assimilation occurring not only after a long influence of ammonia lasting 14 days, but also within one hour after starting the NH₃ treatment. The decline of assimilation was probably caused by a higher resistance of stomata against CO₂ influx in leaf tissue as can be concluded from the observation that transpiration was decreased in the same way as assimilation.The effect of ammonia in nutrient solution could also be due to the occurrence of higher NH₃ concentrations in leaf tissue, because both, pH of plant press sap as well as NH₄ concentration of plant tissue, were increased.Furthermore, it is shown that the nitrate content of plant tissue was diminished by ammonia whereas ammonium and amide content were raised. Regulation of nitrate uptake of plants by means of ammonium and amide content of tissue is discussed.     

Purification and Identification of a Rhabdovirus from Thunbergia alata

A subgroup 2 rhabdovirus was isolated in south-east Queensland from black-eyed Susan (Thunbergia alata) with symptoms of vein yellowing, vein clearing and leaf distortion. Bacilliform particles accumulated in the perinuclear space of infected plants and measured 69 ± 7 × 161 ± 8 nm in unfixed preparations. The virus was not transmitted mechanically. Purified preparations of the Thunbergia alata rhabdovirus (TaRV) contained four major proteins with molecular weights of 80 kD, 48 kD, 40 kD and 35 kD, similar to those of datura yellow vein virus (DYW), a newly described rhabdovirus from Australia. The 80 kD protein was identified as the viral glycoprotein. In immunoblots, the two largest proteins of TaRV reacted strongly with antiserum to DYW, but were serologically distinct from sonchus yellow net, cereal chlorotic mottle, potato yellow dwarf and lettuce necrotic yellows viruses. TaRV is considered to be a strain of DYW.     

Trifluralin-induced chlorosis in soybeans (Glycine max (L.) Merr.) grown on clayey,high pH soils

Summary The cause of leaf chlorosis, frequently observed on soybeans (Glycine max (L.) Merr.) grown on high pH soils of the Mississippi Blackland Prairie, is thought to be low Fe availability and restricted rooting. Three greenhouse experiments were conducted using two soils, Sumter, a Rendollic Eutrocrept and Okolona, a Typic Chromudert; nine soybean cultivars differing in Feefficiency; and trifluralin (α-α-α-trifluoro-2,6-dinitro-N, N-di-propyl-p-toludine). Trifluralin at rates greater than 0.56 kg/ha caused chlorosis which was more severe on the Sumter, a soil low in available Fe. Fe-efficient cultivars were more resistant to the chlorosis induced by trifluralin than the Fe-inefficient cultivars. It was concluded that the chlorosis is an Fe deficiency caused by reduced uptake. The herbicide-induced chlorosis can be avoided by proper dosage and placement of the herbicide.     

Chlorosis caused by two recessively interacting genes reveals a role of RNA helicase in hybrid breakdown in Arabidopsis thaliana

Hybrids often differ in fitness from their parents. They may be superior, translating into hybrid vigour or heterosis, but they may also be markedly inferior, because of hybrid weakness or incompatibility. The underlying genetic causes for the latter can often be traced back to genes that evolve rapidly because of sexual or host–pathogen conflicts. Hybrid weakness may manifest itself only in later generations, in a phenomenon called hybrid breakdown. We have characterized a case of hybrid breakdown among two Arabidopsis thaliana accessions, Shahdara (Sha, Tajikistan) and Lövvik‐5 (Lov‐5, Northern Sweden). In addition to chlorosis, a fraction of the F₂ plants have defects in leaf and embryo development, and reduced photosynthetic efficiency. Hybrid chlorosis is due to two major‐effect loci, of which one, originating from Lov‐5, appears to encode an RNA helicase (AtRH18). To examine the role of the chlorosis allele in the Lövvik area, in addition to eight accessions collected in 2009, we collected another 240 accessions from 15 collections sites, including Lövvik, from Northern Sweden in 2015. Genotyping revealed that Lövvik collection site is separated from the rest. Crosses between 109 accessions from this area and Sha revealed 85 cases of hybrid chlorosis, indicating that the chlorosis‐causing allele is common in this area. These results suggest that hybrid breakdown alleles not only occur at rapidly evolving loci, but also at genes that code for conserved processes.     

Comparative cytopathology of Crinivirus infections in different plant hosts

We used transmission electron microscopy to compare the cytopathology induced in plants by five criniviruses (genus Crinivirus; Lettuce infectious yellows virus (LIYV), Cucurbit yellow stunting disorder virus (CYSDV), Tomato infectious chlorosis virus (TICV), Tomato chlorosis virus (ToCV) and Beet pseudo‐yellows virus (BPYV) (Hartono et al., 2003)). We also compared the patterns of infection for plants and mesophyll protoplasts infected by LIYV and Beet yellows virus (BYV), type members of genera Crinivirus and Closterovirus, respectively. The main cytopathological effects induced in plants by criniviruses were common in young leaves and included alterations of the chloroplasts and the presence of BYV‐type inclusion bodies in companion cells. Virus‐like particles were present in sieve tubes and vascular parenchyma cells as scattered particles, or in companion cells as large masses forming cross‐banded inclusions. Depending on the virus and the plant, it was possible to find virions or virus‐like particles out of the phloem cells, but only in cells of the bundle sheath. Virion‐like particles were never found outside of the vascular tissue. Accumulation of electron‐dense material at the plasmalemma was common for criniviruses, but only LIYV infections produced characteristic conical electron‐dense plasmalemma deposits (PDs). The LIYV‐induced PDs have a crystalline‐like structure and were found at the internal side of plasmalemma.     

Incidences and progression of tomato chlorosis virus disease and tomato yellow leaf curl virus disease in tomato under different greenhouse covers in southeast Spain

Epidemics of whitefly‐transmitted Tomato chlorosis virus, Tomato yellow leaf curl Sardinia virus and Tomato yellow leaf curl virus have been present in the south east of Spain since the 1990s. A survey was performed in 40 greenhouses and nethouses during 2003 to establish the relationship between the disease incidence and the quality of greenhouse or nethouse coverings, providing a physical protection of crops against whiteflies. For tomato chlorosis virus disease (ToCD), the incidence correlated with the type of greenhouse cover and was most reduced under higher quality covers. Control of tomato yellow leaf curl disease (TYLCD) was achieved only for crops grown in the highest quality greenhouses. TYLCD incidence in tolerant tomatoes remained below 100% within the 5 months of sampling, despite the disease progress rate at the initial stage of the cultivation being higher than that of ToCD, which did reach 100% incidence in many greenhouses. Linear regression analysis showed that the development of ToCD and TYLCD in most of the greenhouses was best described by the monomolecular model and the Gompertz model, respectively. Tomato infectious chlorosis virus was not detected in parallel surveys carried out during this study, although it has been described previously in the area studied.     

Comparative phytotoxicity of nitrapyrin and ATC to several leguminous species

Summary The relative toxicity of nitrapyrin 2-chloro-6-(trichloromethyl) pyridine and ATC (4-amino-1, 2, 4-triazole) on the growth of chick peas (Cicer arietinum L.) cow peas (Vigna sinensis L.), green beans (Phaseolus vulgaris L.), green peas (Pisum sativum L.) and mung beans (Phaseolus aureus Roxb.) and their effectiveness as nitrification inhibitor were studied under greenhouse conditions. ATC produced no toxicity symptoms in green peas, whereas resulted in leaf chlorosis in cow peas, chick peas and green beans. However, nitrapyrin toxicity appeared as leaf chlorosis in cow peas, and interveinal chlorosis in chick peas. Moreover, nitrapyrin-treated green beans and peas developed leaf curling and cupping. Although ATC had no significant effect on growth, a suppression in plant growth was associated with nitrapyrin application. Furthermore, green beans was the most resistant and chick peas the most sensitive to nitrapyrin. Nitrapyrin was more effective nitrification inhibitor than ACT, especially at the lower rates.     

A physiological study ofTeucrium scorodonia ecotypes which differ in their susceptibility to lime-induced chlorosis and iron-deficiency chlorosis

Summary Edaphic ecotypes ofTeucrium scorodonia have been shown which differ in their susceptibility to lime-induced chlorosis. Plants especially resistant or susceptible to lime-induced chlorosis were found to be similarly resistant or susceptible to iron-deficiency chlorosis. Differences were found in the chlorophyll-iron and dry weight-chlorophyll relationships of the leaves of green and chloroticTeucrium plants, similar effects being produced by growth on a calcareous soil, in iron-deficient culture or by bicarbonate treatment. Chlorotic leaves had less chlorophyll per unit iron but had a greater dry weight per unit chlorophyll than green material. Chlorotic leaves were found to be reduced in both leaf area and dry weight compared with green ones, the reduction in dry weight being the greatest. Common root abnormalities were noted in chlorotic material induced by the above three methods.Evidence was produced which suggested that the difference between chlorosis-resistant and susceptible plants lay in qualitative differences in their iron transport compounds produced within the rootstock. Differential iron uptake was not suggested as a cause of the differences in behaviour. There was, however, evidence of a key role of the root iron pool in population differences in chlorosis susceptibility.Bicarbonate was found to suppress first iron uptake and then iron translocation. A possible causal role of the bicarbonate ion in lime-induced chlorosis was suggested through these effects and through its possible effect on the production of iron-transport compounds.     

Foliar fertilization to control iron chlorosis in pear (Pyrus communis L.) trees

The effectiveness of foliar fertilization to re-green chlorotic leaves in iron-deficient pear trees has been studied. Trials were made to assess the influence of (i) the level of Fe deficiency, (ii) the leaf surface treated (adaxial or abaxial), and (iii) two different surfactants, L-77 and Mistol. Treatments were ferrous sulphate alone, ascorbic, citric and sulphuric acids, applied either alone or in combination with ferrous sulphate, Fe-DTPA and water as a control. Solutions were applied with a brush and leaves were treated twice each year. None of the treatments caused a full recovery from Fe deficiency chlorosis. Treatments containing Fe caused the largest re-greening effects, and FeSO₄ had a similar re-greening effect to Fe(III)-DTPA. Increases in leaf Chl were more pronounced with abaxial leaf surface applications and in severely deficient leaves. Using Fe(III)-DTPA in foliar sprays does not seem to be justified, since their effects are not better than those of FeSO₄. The joint use of Fe(III)-DTPA and L-77 and that of FeSO₄ and citric acid do not seem to be suitable. With a single foliar application, FeSO₄ combined with acids gave slightly better results than FeSO₄ alone. Acidic solution applications without Fe may be effective in alleviating chlorosis in some cases, especially in the case of citric acid. In the current state of knowledge, foliar fertilization cannot offer yet a good alternative for full control of Fe chlorosis, although its low environmental impact and cost make this technique a good complementary measure to soil Fe-chelate applications and other chlorosis alleviation management techniques. Abbreviations: Chl – chlorophyll; EDDCHA – ethylenediamine di(5-carboxy-2-hydroxyphenylacetic) acid; EDDHA – ethylenediamine di(o-hydroxyphenylacetic) acid; EDDHMA – ethylenediamine di(o-hydroxy-p-methylphenylacetic) acid; EDDHSA – ethylenediamine di(2-hydroxy-5-sulfophenylacetic) acid     

Comparison of soil tests and leaf analysis as methods of diagnosing Zn deficiency in British Columbia apple orchards

Soil Zn extracted by 0.25M MgCl₂ or DTPA as an index of Zn availability was compared to Zn or P:Zn concentration in leaves for 40 commercial apple orchards in southern British Columbia. Sampled trees included a wide range of ages and cultivar/rootstock combinations. Leaves were sampled from the midportion of current season's shoots at four times; May–June 1984, July 1984, May 1985 and July 1985. At the same time the severity of the four Zn deficiency symptoms, rosetting, blind bud, little leaf and chlorosis was assessed. Little relationship was found between soil and leaf Zn measures, except in July 1984, when both terminal leaf Zn and P:Zn concentrations varied directly with 0.25M MgCl₂ extractable soil Zn. Soil Zn extracted by 0.25M MgCl₂ was more closely related to severity of deficiency symptoms on the trees at all four samples dates than was DTPA-soil Zn or leaf Zn concentration. Blindbud was the most useful indicator of deficiency in samples collected in May whereas chlorosis was the most useful one in July.     

Injury to Rice Plants Caused by Complete Submergence; A Contribution by Ethylerie (Ethene)

Complete submergence of rice plants (Oryza sativa L. cv. ‘IR42’)in dilute nutrient solution for 3–6 d almost stopped theaccumulation of dry matter, depressed soluble carbohydrate concentrationby over 75% and promoted chlorosis in fully expanded leaves.Increase in fresh weight by the shoots was not impaired. Extensionby the youngest visible leaf was stimulated. Extension by thenext leaf to appear was retarded by submergence. These growthresponses to submergence were associated with a 1-5-fold increasein the partial pressure of endogenous ethylene (ethene). Applying ethylene (0.3–0.35 Pa) in the gas-phase to non-submergedplants reproduced some, but not all, of these effects of submergence.Thus, greater leaf extension and chlorosis of submerged plantscould be attributable to accumulated ethylene but neither theslow relative growth rate nor the decreased extension of leavesemerging after the start of submergence could be so attributed. Two cultivars (‘FR13A’ and ‘Kurkaruppan’)already known to tolerate submergence, differed little fromsubmergence-intolerant ‘IR42’ in their relativegrowth rate and soluble carbohydrate concentration during submergence.However, their underwater leaf extension was less than in ‘IR42’and chlorosis was much less prevalent, especially in ‘FR13A’.Similarly, ethylene supplied to non-submerged plants was a lesseffective promotor of leaf extension and chlorosis in the twosubmergence tolerant cultivars. Application of 1.0 kPa carbondioxide in the gas-phase prevented the chlorosis response toethylene. The results indicate that accumulated ethylene is a likely causeof fast leaf extension and chlorosis in submergence intolerantforms of rice, particularly when amounts of dissolved carbondioxide are minimal. Key words: Oryza sativa L., aeration, ethylene (ethene), stress-tolerance     

Characterisation and serology of virus-like particles associated with faba bean necrotic yellows

A disease showing chlorosis, leaf rolling and stunting in Vicia faba and other legumes was observed in West Asia and North Africa during 1987–1988. The putative causal agent could not be transmitted mechanically, but could be transmitted by aphids, most efficiently by Acyrthosiphon pisum, in the persistent manner. Further studies revealed isometric virus-like particles (VLPs) closely associated with the disease, although their infectivity could not be demonstrated by membrane feeding. These particles, measuring c. 18 nm in diameter and containing a capsid protein of about 22 kDa and ssDNA of about 1 kb, are hereafter designated faba bean necrotic yellows virus (FBNYV). A high proportion of circular nucleic acid molecules of about 0.9 kb were visualised by electron microscopy. Hybridisation analysis of cloned viral DNA suggests that the circular genome is larger than 1 kb and consists of several components of similar size. An antiserum produced against FBNYV was used in ELISA, immunoelectron microscopy (IEM) and Western blot experiments for virus detection in aphids and field samples and for serological comparison with other viruses. Weak heterologous reactions between FBNYV and subterranean clover stunt virus (SCSV) were detected in IEM, but could not be confirmed in ELISA or Western blots. No serological relationship to banana bunchy top virus (BBTV) was detected. Using a direct tissue blot immunoassay (TBIA), FBNYV was detected in vascular tissue of infected faba bean leaves and stems.     

Zinc, Iron, and Chlorophyll Metabolism in Zinc-toxic Corn

Zinc toxicity and Zn-Fe interactions were studied in corn (Zea mays L. var. Barbecue hybrid) grown in hydroponic culture. High Zn greatly reduced the root and shoot fresh weights; increasing Fe largely, but not completely, restored normal growth. Correlation analyses of root and leaf Zn and Fe contents suggested that Zn may interfere with the translocation of Fe; however, Zn toxicity was not associated with a diminished leaf Fe content. Fe did appear to retard both the absorption and the translocation of Zn. The chlorosis of Zn-toxic plants is not attributable to diminshed total leaf Fe; however, this chlorosis is relieved by increasing nutrient Fe. Zn and Fe probably do interact at some site.     

In vitro evaluation of sugarcane resistance to gumming disease and of Xanthomonas campestris pv. vasculorum aggressiveness

Sugarcane plantlets were sectioned halfway between the base and the youngest ligule and then inoculated by soaking the wound in a suspension of Xanthomonas campestris pv. vasculorum. The infection caused rapid necrosis of the inoculated leaves, chlorosis of uninoculated leaves, or death of the inoculated plantlet. New tillers sometimes showed chlorosis or white streaks. The effects of the inoculum concentration, the cultivar, and the bacterial strain on symptom severity were determined. The ranking of cultivars depended on the inoculum concentration, and strains were found to differ with regard to aggressiveness. However, cultivars and strains were more effectively classified in greenhouse trials. The poor expression of leaf resistance appeared to limit the use of the in vitro test.