title: [Susceptibility of leaves and fruits of tomato varieties and of their hybrids to attack by Phytophthora infestans].
abstract: 1. The investigations were started to establish a correlation between the incidence of Phytophthora infestans (Mont.) de Bary on leaves and on fruits of tomatoes, the mechanism of the inheritance of the resistance and the number of responsible genes. 2. A close correlation was found between the spontaneous incidence on leaves and fruits and the results of artificial inoculation by the leaf-disc-test. The resistant types especially showed a remarkably low percentage of attack in all three tests. Resistant plants were successfully selected by means of the leaf-disc-test; the leaves as well as the fruits of the progeny were largely free from the disease. 3. The field-resistance of the variety 'Atom' was demonstrated to be due to a high degree of relative resistance of the leaves against the races T0 and T1. 4. The results obtained from F1-hybrids of 'Atom' with various more or less susceptible varieties indicate the participation of incompletely dominant genes. Since in the F2 a certain number of plants with a high degree of field-resistance could be selected, it is suggested that the field-resistance against Phytophthora infestans is based on a few genes only. From our results we conclude that principally two genes in the variety 'Atom' determine the field-resistance against the fungus. A participation of other modifier-genes can be supposed. We propose the gene-symbols Phf and Phf-2 for the Phytophthora-field-resistance.
authors.affiliation: Sektion Biologie und Arbeitsgruppe Phytopathologie, Ernst-Moritz-Arndt-Universität Greifswald, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Grümmer
authors.forename: E
authors.initials: E
authors.lastname: Günther
authors.forename: D
authors.initials: D
authors.lastname: Eggert