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Studies on the Inheritance of Resistance to Fusarium oxysporum f. sp. apii in Celery. T. J. Orton, Department of Vegetable Crops, University of California, Davis 95616. M. E. Durgan, and S. D. Hulbert, Department of Vegetable Crops, University of California, Davis 95616. Plant Dis. 68:574-578. Accepted for publication 12 January 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-574.

Fusarium yellows, incited by Fusarium oxysporum f. sp. apii, is currently the most important disease of celery (Apium graveolens L.) in North America. No effective control methods have been developed for this pathogen, and at present, breeding for resistance is the approach most widely used. Experiments were conducted to elucidate the inheritance of resistance to race 2 of the pathogen, which was observed previously in the celeriac line PI 169001. F2 populations derived from a cross of this line with a putatively tolerant selection from the susceptible celery cultivar Tall Utah 52-70R showed segregation of resistance and susceptibility. With one exception, F2 segregation ratios were between 3:1 and 15:1 resistant/susceptible. Results from progeny tests of 20 resistant F2 plants were consistent with the conclusion that resistance in PI 169001 was conditioned by a dominant allele at a single locus and that segregation distortion was caused by segregating genes with quantitative effects on resistance contributed by the selected Tall Utah 52-70R parent or both parents. The F2 segregation from a separate cross was also consistent with the hypothesis of a single dominant resistance gene and a quantitative resistance gene(s) in PI 169001.