OBSERVATIONS ON A VIRUS ISOLATED FROM WISTERIA FLORIBUNDA DC IN ITALY

From plants of Wisteria floribunda showing a bright vein mosaic on the leaves, a virus of the « Potato virus Y » group has been repeatedly isolated in Piedmont (Italy). It is serologically closely related to wisteria vein mosaic virus (WVMV) isolated by Dr. Bos at the same time in the Netherlands. This name has therefore been accepted and used also for the Italian virus isolate. WVMV was transmitted by sap inoculation to 27 plant species belonging to the families Amaranthaceae, Chenopodiaceae, Compositae, Leguminosae and Solanaceae. The plants which reacted in clearly differential ways were: Amaranthus hybridus var. hypochondriacus, Atriplex hortense, Chenopodium quinoa, Lupinus albus, Nicotiana clevelandii, Phaseolus vulgaris and Zinnia elegans. The properties « in vitro » of WVMV were : thermal inactivation point between 60 and 65°C for 10 min; dilution end point between 10⁻⁵ and 10⁻⁶; longevity « in vitro » at room temperature between 12 and 15 days. WVMV seemed not to be seed-transmitted in W. floribunda, Phaseolus vulgaris and Trigonella foenum-graecum. It was experimentally transmitted in the non-persistent way (« stylet-borne ») by Aphis crac̣civora and Myzus persicae. The latter aphid was a more active vector when it was given an acquisition feeding time of 1 min instead of 5 or 20 min. Cross-protection trials between WVMV and bean yellow mosaic virus gave negative results. The serological affinity between the Italian and the Dutch isolate of WVMV was ascertained by serological slide tests. In the electron microscope WVMV showed elongated, flexuous particles with a normal length of about 750 mμ. Da piante di Wisteria floribunda che presentavano vivace mosaico nervale, è stato più volte isolato in Piemonte un virus ascrivibile al « Gruppo del virus Y della Patata ». Sierologicamente esso è risultato strettamente affine ad un virus contemporaneamente isolato in Olanda dal Dr. Bos, per il quale è stato proposto il nome « wisteria vein mosaic virus » (WVMV); tale denominazione viene accettata anche per il virus isolato in Italia ed impiegata nel lavoro. WVMV è stato trasmesso per inoculazione di succo a 27 specie vegetali delle famiglie Amaranthaceae, Chenopodiaceae, Compositae, Leguminosae e Solanaceae. I migliori ospiti differenziali del virus sono stati: Amaranthus hybridus var. hypochondriacus, Atriplex hortense, Chenopodium quinoa, Lupinus albus, Nicotiana clevelandii, Phaseolus vulgaris e Zinnia elegans. Le proprietà « in vitro » di WVMV sono sta