Presence of Tobacco Mosaic Virus in Roots of Field-grown Tomato Plants Healthy in Appearance

Abstract

Tomato plants healthy in appearance were collected from five fields, in which mosaic disease had been prevalent during recent years. Leaves and roots were tested for the presence of TMV. Tests for samples of 50 plants collected from three fields, where mosaic disease did not occur, showed that 24 plants (48%) contained TMV in roots but not in leaves, while 16 plants (32%) contained TMV both in the roots and leaves. Ten plants (20%) did not show presence of TMV in either leaves or roots. No plants were found in which TMV could be detected in the leaves only. In the other two fields, 10-15% of the plants showed symptoms of mosaic disease in the fields. The samples of 40 apparently healthy plants were collected from these fields. In these samples of leaves and roots, 13 tomato plants (33%) contained TMV in roots but not in leaves, 18 plants (45%) contained TMV both in the roots and leaves, and 2 plants (5%) in leaves but not in the roots. Seven plants (17%) did not show presence of TMV in leaves and roots.
These results show that many tomato plants apparently healthy in appearance and having no detectable virus in their foliage, collected from fields which have been continuously cultivated with tomatoes, are infected with TMV in their roots. From the 60 plants which contained TMV in the above experiments, tomato strain was found in 59 plants (98%), ordinary strain was found in 6 plants (10%), 5 plants being doubly infected with both tomato and ordinary strains.
Roots of 25 common weeds of Youngia japonica, Sonchus oleraceous, Capsella bursapastoris, Stellaria media and Cerastium caespitosum, healthy in appearance, were collected from the same tomato fields and the roots were tested for the presense of TMV. In every case, presense of TMV could not be detected by the method used.