Spinach chlorotic spot virus: a new strain of 8eet yellows virus

Abstract

A Uirus causing systemic chlorotic spot symptom in spinach (Soinacea oleracea) was characterized and iden tified as a strain of beet yellows virus and was referred to as spinach chlorotic spot virus (SCSU). The virus particles were flexuous and approximately 840 nm in length. In glasshouse all the beet varieties (Crimson globe, Eclipe and Detroit) and spinach varieties (lucullus, Foordhook giant and Swiss chard) tested were susceptible. The virus isolate was limited in host range to the family Chenopodiaceae. In Beta vulgaris. a member of chenopodiaceae family, systemic necrotic lesions were observed about 8-10 days after inoculation. The necrosis was more marked in mature leaves and there was general intensification of red colour. A few leaves showed yellow spots and the plants were also stunted. Necrotic lesions, 2-3 mm in diameter, were also observed in Chenopodi tim amaranti col or 5 days after inoculation. Systemic tip necrosis was also observed 2-3 weeks after inoculation. Chenopodi urn gui noa and C. album showed the same type of symptoms already described for C. amaranti col or. White necrotic spots, about 2-3 nm in diameter, with reddish outline, observed in Gomphrery xi i i globosa. Chenopodium amaranticolor was used as an assay host. SCSU was successfuly transmitted in a semi persistent manner by the aphid Myzus persicae. The virus isolate had a thermal inactivation point (TIP) at o o -4 56 C and not 54 C; dilution end-point (DEP at 10 and -5 not 10 i longevity in in vitro (LIU) at one days and not 2 days. SCSU was partially purified from infected spinach leaves by differential centrifugation. The virus was extracted with 0.1M phosphate buffer, pH 7.2, and clarified in 72 ether. In homologous reactions, the virus reacted with its own antiserum to the titre of 1/1024 in nii cropreci pi ti n tests. On the basis of these criteria and results obtained, the virus inducing chlorotic spots in spinach was identified as a strain of beet yellows virus.