Date of Award:

5-1968

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Pathology

Committee Chair(s)

O. S. Cannon

Committee

O. S. Cannon

Committee

W. S. Boyle

Committee

J. L. Anderson

Abstract

Experiments have demonstrated that Verticillium dahliae is capable of direct cortical penetration of roots and of subsequent distribution throughout plants of both resistant (Loran Blood) and susceptible (Meteor) varieties of tomato. Plants were inoculated by the root dip method and planted in sterile soil. After one week the fungus was isolated from the upper portions of both the susceptible and resistant varieties as indicated by growth petiole sections plated on PDA. The distribution of the fungus in the resistant plants was irregular, but in susceptible plants the fungus was isolated regularly from all petiole sections. In experiments using disposable growth packets, uninjured roots were allowed to grow into agar containing hyphae. The roots were then penetrated by the fungus. Results of these experiments closely paralleled the results found with the root dip method. When penetration did occur, the distribution of the fungus in the resistant plants was not as extensive as that in the susceptible variety. Infection of tomato in natural conditions seems to involve more than the presence of the pathogen and a susceptible variety of plant. Tests were conducted in which heavily infested wheat was mixed with pasteurized soil. Not one plant of either variety had the pathogen present in its vascular systems.

No conclusions were drawn on whether a phytoalexin was present or absent in the resistant variety used.

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