A single dominant gene for Fusarium wilt resistance in protoplast-derived tomato plants.

Tomato plants resistant to the fungal pathogen, Fusarium oxysporum f. sp. lycopersici, race 2, were obtained using in vitro selection against fusaric acid, a non-specific toxin, as well as non-challenged cells. Protoplasts were isolated from cotyledonary tissue of tomato cv. 'UC-82', which is susceptible to Fusarium race 2. Protoplasts were challenged with the toxin, and the resistant calli were further subjected to the toxin. Plants regenerated from toxin-resistant calli were screened for resistance to the pathogen by using the Fusarium slurry inoculation technique. Seeds were collected from the surviving individuals, germinated and rescreened for resistance to the pathogen. Data obtained from this test showed a ratio of three resistant to one susceptible among R1 progenies. Further analysis of the R2 progenies confirmed that the fusarium-resistant plants were either homozygous or heterozygous dominant for the gene conferring the resistance. Similar results were recorded for tomato plants regenerated from cells that received no selection pressure. The nature of this single dominant gene-type of resistance is under investigation.