Abstract
A virus disease of eggplant was found in the vicinity of Tokyo during 1971-1972. Young leaves of the diseased plants showed necrotic spots, sometimes followed by twisting or crinkling of the leaves and dwarfing of whole plant. Some experiments were made to identify the causal virus.
The disease was easily transmitted by sap inoculation. Out of 38 species of plants among 15 families, 24 species among 10 families were proved to be susceptible to the causal virus. The virus was also transmitted by the green peach aphid, Myzus persicae (Sulz.).
The virus in infective sap was inactivated in 10 minutes at 60-70C, and in 4-6 days at room temperature. Its dilution end point lied between 1:10, 000 and 1:100, 000.
Spherical virus particles of about 25nm in diameter were detected in the diseased eggplant leaves under the electron microscope by the direct negative staining method. The same virus particles were also detected in leaves of mechanically inoculated plants.
The diseased spinach leaves were ground in phosphate buffer (0.2M, pH 7.6), and then the virus in the extract was partially purified by differential centrifugation followed by sucrose density gradient centrifugation. The finally obtained virus preparation contained a large number of spherical virus particles of about 25nm in diameter. Size and shape of these particles were quite uniform. The preparation showed a high infectivity to Chenopodium amaranticolor.
Electron microscopy of the diseased eggplant leaves showed that the virus particles distributed as individuals or as amorphous, sometimes crystalline, aggregates in vacuole and cytoplasm. They were found in epidermal, mesophyll, and also phloem parenchyma cells. Sometimes a chain-like array of the virus particles was observed in plasmodesmata connecting two neighbouring cells. Necrosis and abnormal development of vesicular bodies were common in cells of the diseased tissues.
From these results it is evident that the causal virus is broad bean wilt. Broad bean wilt virus has not been reported to occur on eggplant. Thus we propose to name the disease “necrotic leaf spot of eggplant”.
