Viruses isolated from tomato plants showing mosaic and/or streak in Japan, with special reference to tomato strain of tobacco mosaic virus

Abstract

1) In a survey to determine the causal viruses of tomato plants showing mosaic and/or streak, 89 samples were collected from Yamanashi, Kanagawa, Nagano, Kochi and Tottori Prefectures. These diseased plant samples were subjected to inoculation tests on a series of 8 differential hosts using carborundum. 85 samples (95 per cent) yielded tobacco mosaic virus (TMV), 21 samples (24 per cent) yielded cucumber mosaic virus (CMV) and 2 samples (2 per cent) yielded potato virus X (PVX). From 17 samples (19 per cent), both TMV and CMV were isolated, and from 2 samples both TMV and PVX were isolated. The collections were divided on basis of the original symptoms on tomato plants into mosaic group (70 samples) and streak group (19 samples). Both groups yielded almost the same kinds of viruses and isolation percentage of each virus.2) Of the 85 samples which contained TMV, 78 samples (92 per cent) yielded TMV specialized to tomato (tomato strain of TMV), while 11 samples (13 per cent) were of the ordinary strain of TMV. From 4 samples (5 per cent), both tomato strain and ordinary strain were isolated.3) Tomato strain produced only local necrotic lesions on tobacco (Bright Yellow), N. sylvestris and petunia, but no systemic mosaic on these plants. No local lesions were produced on bean (Otebo). Ordinary strain produced local lesions on bean, but no local lesions on the above 3 species. On these plants, ordinary strain produced systemic mosaic.4) Tomato strain was considered to be identical with tomato streak strain of TMV described by Ainsworth (1933) and Smith (1957), judging from reactions of several plants, thermal inactivating point, cross protection test, particle size and agglutinaton reaction on slides with antiserum against ordinary strain of TMV. The name “tomato strain” seems to be more preferable than “tomato streak strain”, because this strain can be isolated from samples showing only the mosaic symptom. Hence the name “tomato strain” is preferred.5) Multiplication of tomato strain was better than that of ordinary strain in the inoculated leaves of tomato. When these two stranis were inoculated on lower leaves of tomato respectively, tomato strain was recovered from top leaves after 3 days, while ordinary strain was recovered after 5 days. These results indicate that tomato strain is more pathogenic to tomato plant than ordinary strain.