ISHS Acta Horticulturae 789: XV Meeting of the EUCARPIA Tomato Working Group
RESISTANCE TO TWO IMPORTANT TOMATO DISEASES IN CALIFORNIA |
| Author: | L. Stamova |
| Keywords: | Lycopersicon esculentum, disease resistance, Verticillium wilt, corky root |
| Abstract:
Two major tomato diseases limit tomato production in California – Verticillium wilt, caused by Verticillium dahliae race 2 and corky root, caused by Pyrenochaeta lycopersici. The screening of germplasm for the last two decades has not revealed a reliable source of resistance to race 2. The recessive nature of gene py-1 has significantly slowed the development of processing tomatoes resistant to corky root. The objective of this work was to confirm the usefulness of the author’s sources of resistance when inoculated with California isolates of the pathogens and to incorporate these new sources into California Tomato Research Institute (CTRI) processing tomato cultivars. A standard root-dip method was applied for inoculation of tomato seedlings with V. dahliae race 2. Two methods – transplanting into infected soil and fungus culture – were used to inoculate young plants with P. Lycopersici. The dominant resistance to race 2 in the line Veda was confirmed once again when the line and F1 hybrids with ‘Veda’ were grown in a heavily infested field. The introgression of race 2 resistance into CTRI cultivars is in progress. Another line, Yoti, with resistance derived from different wild species, also showed very good performance after inoculation with race 2 isolates. A dominant factor was responsible for the resistance in the Yoti line. Two cultivated type lines – 'Pirelly' and 'Espera' – with resistance coming from different wild species, demonstrated very high levels of resistance to California populations of P. lycopersici in both field and greenhouse tests. The factors conferring resistance are dominantly inherited. The introgression of the dominant resistance into CTRI processing tomato cultivars is under way. The use of dominant genes for resistance would speed the development of tomato hybrids resistant to corky root. The availability of two sources with resistance derived from different wild species would allow breeders to pyramid the resistance genes and to increase the resistance level, as well as to slow the evolution of the pathogen. | |
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