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Turnip Yellow Mosaic Virus in Yugoslavia
Đorđe Mamula
; Hrvatska
Sažetak
In 1965 we have found virus infected specimens of Brassica rapa var. silvestris with mosaic pattern in Slovenia in the vicinity of the town Celje. Already at the beginning of our investigation of this isolate (Y65) we have noticed the similarity in symptoms with the turnip yellow mosaic virus (TYMV). We have made further researches primarily in order to identify this isolate. In order to be able to make comparisons we have procured by the courtesy of Dr. C. H. C a d m a n (Invergowrie, Dundee, Scotland) an precisely identified isolate (YS) of the TYMV, and by kindness of Dr. O. Bode (Braunschweig) another strain (YD) of the same virus isolated from Danish turnip plants. Besides that Dr. C a d m a n has also given us an antiserum against the TYMV.
During the investigation of the isolate Y65 we have studied the reaction of test plants, host range, physical properties, alterations in plastids, and moreover we have carried out serological tests, electron microscope analysis and purification of the virus.
We have tried to transmit isolate Y65 to 20 species from the family Cruciferae. Distinct symptoms of infection have developed on 15 species (Table 1). We have also inoculated several species from other families but symptoms of disease have appeared only on two species, that is, on Cleome spinosa (Capparidaceae) and Reseda odorata (Resedaceae). On these two species vein-clearing has appeared on the leaves situated above the place of inoculation, and on upper leaves less or more chlorotic areas and mosaic. C. spinosa was mentioned by Smith (1957) and R. odorata by Broad- bent and Heathcote (1958) as species susceptible to TYMV. These plants are up to now the only known species outside the family Cruciferae which can be infected by TYMV.
Infected cruciferous plants usually show distinct symptoms of infection. The incubation period lasts from 6 to 15 days. The appearance of chlorotic local lesions on inoculated leaves is fairly common in some hosts and it usually comes before the symptoms of systemic infection. In the course of our investigations the most distinctly developed lesions have been found in Raphanus raphanistrum, R. sativus (PI. 1, c, d), Brassies oleracea var. gongylodes f. violacea, Eruca sativa and Sisymbrium officinale, and somewhat less expressed lesions in Brassica chinensis, B. pervi- ridis, B. rapa var. rapifera and B. napus var. napobrassica. It is likely that some of the quoted species, particularly R. raphanistrum and R. sativus, will be suitable for use in quantitative investigations of this virus. Species B. chinensis has already been used for that purpose (Diener and Jenifer 1964).
The first symptom of the systemic infection is vein-clearing (PL 1, a). Parallel with this symptom, systemic spots develop in some species, as for instance in R. sativus, B. chinensis, B. perviridis, B. rapa var. rapifera and specially in B. oleracea var. gongylodes f. violacea. In some hosts we have sometimes observed vein-banding (PI. 1, b). Besides vein-clearing the most common and the most characteristic symptoms of our isolate are variegation and mosaic. These two symptoms are expressed very clearly on the leaves of B. perviridis (PL 2,a, b), B. rapa var. rapifera, B. chinensis and sometimes Eruca sativa (Pl. 2, c). Green, clear yellow and often almost white areas alternate on their leaves (Pl. 2, a, b, c) the yellow areas being most outstanding. Quite frequently the line pattern can be seen on leaves of B. perviridis and B. rapa var. rapifera (Pl. 2, d). The normally yellow petals of B. chinensis often show the phenomenon of white lines, and sometimes petals are white on their entire surphace (comp. Smith 1957).
In the greenhouse grown infected plants are little stunted in comparison with the healthy ones.
According to the described symptoms in hosts of the isolate Y65, the isolate fully agrees with the descriptions of TYMV by Smith (1957), Klinkowski (1958) and other authors. We have also noticed a great similarity between the symptoms of the isolates Y65 and YS.
In respect to the physical properties our isolate corresponds to TYMV. The infection end-point of our isolate is somewhat higher than 1 : 10®, and it withstands in vitro considerably more than 10 days (comp. Smith 1957, Broadbent and Heathcote 1958).
Isolate Y65 causes a development of characteristic alterations in pla- stids in the cells of infected plants. One or more colourless vacuoles are formed in each plastid so that the green parts of the plastids sometimes can be seen in the form of rings or sickles (Pl. 3, b). The plastid can be seen in the first form when a vacuole arises in the centre of it and in the sickle form when a vacuole arises on the margin. Besides that plastids gather forming bigger masses in which their boundaries later disappear. Such masses often have an irregular shape and are ordinary vacuolised.
Described alterations of plastids are especially clearly visible in sub- epidermal cells of leaves. We have observed them for instance in B. chinensis, B. perviridis, Sinapis alba and in many other species.
The changes of plastids observed by us agree with those investigated by Rubio (1956) in plants also infected with TYMV.
Isolate Y65 has given a distinct positive serological reaction in the slide precipitin test and in the agar-gel diffusion test with the antiserum against the TYMV. In these tests it has reacted very similarly to the isolate YS (Table 2).
We have also purified the isolate Y65 using the method for virus sedimentation by means of ammonium sulphate (Markham and Smith 1949). Clarified infective sap has been freed from various ingredients by applying fractional sedimentation with saturated solution of ammonium sulphate. By such a concentration of this salt, which corresponds to one third of saturation, the virus crystallizes in the solution into the form of small, optical isotropic octahedra which are identical with those of the TYMV (Markham and Smith 1946. 1949; Markham 1959).
Electron microscope analysis revealed the presence of numerous “spherical”, i. e. polyhedral particles in preparation of isolate Y65 which, as regards their dimensions, correspond to virus particles. In preparation of healthy plants we did not find “spherical” particles of same or similar size. As it is already known, the particles of TYMV have a diameter of 28 nm (Markham 1959).
According to these results the presence of turnip yellow mosaic virus in Yugoslavia is proved (comp, also Mamula et al. 1966; Sla- detic 1966; Miličić and Štefanac (1967).
Ključne riječi
Hrčak ID:
154793
URI
Datum izdavanja:
31.12.1968.
Posjeta: 993 *