Sixteen greenhouse tomato hybrids (Lycopersicon esculentum, Mill.) were evaluated for their horticultural traits, and their resistance and reaction towards tobacco mosaic virus (TMV) inoculation (1988). Plants possessing resistance gene Tm-2^a^, in either homozygous or heterozygous state, showed no visual symptoms caused by the virus, while susceptible plants developed mosaic symptoms (blistering and mottling of leaves). Blotchiness means of fruits picked from TMV susceptible plants were significantly higher compared to fruits from TMV resistant varieties.
The presence or absence of tobacco mosaic virus in inoculated plants was confirmed by the Dot Immuno Binding Assay (DIBA). The Dot Immuno Binding Assay is a very sensitive method for detecting the presence or absence of tobacco mosaic virus in tobacco and tomato plants (1985). There were no non-specific reactions when extracts from healthy tomato plants were spotted on nitrocellulose membrane at 1:25 dilution. Extracts of TMV infected tomato plants gave specific reactions in dilutions up to 1:1000. the presence of TMV could be detected in concentrations as low as 500 pg/ml of sap.
The presence of the virus could not be detected in extracts from inoculated or systemically infected leaves of tomato entries that possessed at least one gene for TMV resistance. Also, there was no difference if the gene for TMV resistance was present in homozygous or heterozygous state. The same procedure was also used for detecting TMV presence in tomato fruit extracts. Fruit extracts from healthy or resistant tomato plants at 1:1 dilution did not give specific reactions but TMV could be detected at the same dilution in fruit extracts of susceptible plants, indicating the presence of the virus in these fruits. By using the Dot Immuno Binding Assay it is possible to detect how fast the virus is translocated within the plant, and relate the amount of the virus present in the tomato fruits to the degree of fruit blotchiness.
Literature cited:
Hibi, T. and Y. Saito. 1985. A dot immunobinding assay for the detection of tobacco mosaic virus in infected tissues. J. Gen. Virol. 66: 1191-1194.
Katsiotis, A. 1988. Evaluation of tomato hybrids resistant to tobacco mosaic virus. University of Missouri-Columbia. Department of Horticulture.