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Caratteristiche di un ceppo del virus del mosaico dell'Arabis, isolato da Lilium tigrinum Ker-Gawl

Francesca Marani and Gianni Faccioli
Phytopathologia Mediterranea
Vol. 13, No. 1/2 (Agosto 1974), pp. 101-107
Stable URL: http://www.jstor.org/stable/42684209
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Caratteristiche di un ceppo del virus del mosaico dell'Arabis, isolato da Lilium tigrinum Ker-Gawl
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Abstract

Da piante di Lilium tigrinum Ker-Gawl mostranti aree decolórate sulle foglie, è stata trasmessa meccanicamente ad ospiti erbacei una entità virale isodiametrica che è stata identificata sierologicamente corne un ceppo di virus del mosaico dell'Arabis (AMV). Le medesime piante risultavano infettate latentemente anche da un'entità di circa 650 nm di lunghezza, non trasmissibile meccanicamente aile piante di saggio. Il ceppo di AMV isolato aveva un grado di inattivazione térmica di 54-56°C, un punto di diluizione limite di 10⁻³-10⁻⁴ ed una longevità in vitro di 34 giorni. Il virus è stato purificato omogeneizzando foglie infette di Cucumis sativus L. in cloroformio ed effettuando cicli di centrifugazione differenziale. In gradienti di densità di saccarosio (10-40%) sono state osservate tre zone costituite da particelle di 28 nm di diametro. La superiore risultava costituita da particelle prive di RNA e non infettive (Top) e le due inferiori (Middle e Bottom) costituite da particelle con diversa percentuale di RNA e infettive. La zona superiore aveva infatti uno spettro di assorbimento in UV tipico per una proteina (Amax 274-278; Amin 250-252), mentre le due inferiori davano luogo a spettri tipici per nucleoproteine con i seguenti rapporti caratteristici: M=A280/A260 = 0,796 B= A280/A260 = 0,634 Amax₂₆₀/Amin₂₄₄ = 1,038 Amax₂₆₂/Amin₂₄₀ = 1,361 Nelle prove di reinfezione di piante di L. tigrinum, che già avevano l'entità allungata, siamo stati in grado di riprodurre il quadro sintomatologico originario sia inoculando meccanicamente AMV purificato, che innestando germogli infetti di C. quinoa. An isodiametric virus, serologically identified as a strain of Arabis mosaic virus, was mechanically transmitted to herbaceous hosts from plants of Lilium tigrinum Ker-Gawl showing faint chlorosis. The plants were also latently infected with a tubular virus having a length of about 650 nm which was not mechanically transmitted to the test plants. The strain of AMV isolated had a thermal inactivation point of 54-56°C, a dilution end point of 10⁻³-10⁻⁴ and a longevity in vitro of 34 days. The virus was purified by homogenizing infected leaves of Cucumis sativus L. with chloroform and carrying out differential centrifugation cycles. In 10-40% sucrose density gradient three components formed by particles of 28 nm in diameter were observed. The top component appeared to be made up of non-infective particles deprived of RNA, whereas the middle and bottom components were constituted of infective particles with varying RNA content. In fact, the top component had a UV absorption spectrum typical for a protein (Amax₂₇₄₋₂₇₈ - Amin₂₅₀₋₂₅₂) whereas middle and bottom components had spectra typical for nucleoproteins with the following absorption ratios: M : A280/A260 = 0.796 B : A280/A260 = 0.634 Amax₂₆₀/Amin₂₄₄ = 1.038 Amax₂₆₂/Amin₂₄₀ = 1.361 In test of reinfection of plants of L. tigrinum already infected by the tubular virus, we have been able to reproduce the original symptomatology either by mechanical inoculation of purified AMV or by grafting infected sprouts of C. quinoa. En partant de plantes de Lilium tigrinum Ker-Gawl révélant des zones décolorées sur les feuilles, des hôtes herbacés on été infectés par voie mécanique au moyen d'un virus isodiamètrique que l'analyse sérologique a montré appartenir à une souche de virus de la mosaïque de l'Arabette (AMV). Les mêmes plantes résultaient également être infectées de manière latente par un virus de 650 nm environ de long, qui ne pouvait pas être transmis par voie mécanique aux plantes d'essais. La souche de l'AMV isolée possédait un degré d'inactivation thermique de 54° à 56°C, un point limite de diluition de 10⁻³ à 10⁻⁴ et une longévité in vitro de 3 à 4 jours. Le virus a été purifié par homogénéisation des feuilles infectées de Cucumis sativus L. en chloroforme et par cycles de centrifugation différentielle. En gradients de densité de saccharose (10-40%) on a observé trois zones consistant en particules d'un diamètre de 28 nm. La zone supérieure était formée de particules d'épourvues de RNA et non infectieuses (top) et les deux zones inférieures (middle et bottom) étaient formées de particules comportant des taux différents de RNA et des particules infectieuses. La zone supérieure présentait en effet un spectre d'absorption en UV typique pour une protéine (Amax 274-278; Amin250-252), alors que les deux zones inférieures donnaient des spectres typiques pour les nucléoprotéines, ayant les rapports caractéristiques suivants: M=A280/A260 = 0,796 B=A280/A260 = 0,634 Amax₂₆₀/Amin₂₄₄ = 1,038 Amax₂₆₂/Amin₂₄₀ = 1,361 Dans les essais de réinfection de plants de L. tigrinum ayant déjà le virus allongé, nous avons pu reproduire le tableau symptomatologique originaire soit par inoculation mécanique d'AMV purifié, soit par greffe de bourgeons infectés de C. quinoa.

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