Degree Name

Master of Science (MS)

Semester of Degree Completion

1992

Thesis Director

Janice Coons

Abstract

A rapid detached leaf assay technique was developed to test various pathogens for biological control of hedge bindweed (Calystegia sepium). Detached leaves with complete petiole were excised, surface sterilized in 70% ethanol, washed with sterile distilled water, and placed in sterile petri plates with sterile filter paper moistened with 5ml sterile distilled water. Media, leaf size, temperature and light duration were then tested for conditions that would optimize maximal leaf longevity. The best conditions derived were: 12/12 hrs. light, dark, period, 30°C, sterile distilled water medium and leaves of any size. Twenty-five isolates recovered from bindweed lesions were grown on agar and these pathogens were introduced via 4mm agar plugs on adaxial leaf surfaces and leaves observed for necrotic leaf death. Teliospores of a rust fungus were introduced via 0.1ml spore suspension. Plates were maintained in a lighted growth chamber at 30°C, 12 hrs. light/12 hrs. dark. Lack of symptom induction was equated to lack of pathogenicity. Puccinia convolvuli caused fungal pustules that resulted in necrotic leaf death.

Field tests were conducted with P. convolvuli to determine mycoherbicidal response. A field containing hedge bindweed was mapped to determine areas of concentration. Of these bindweed areas, 3.8% were initially inoculated with rust teliospores and observed for spore spread from inoculated point source as well as necrotic leaf response. At the close of the growing season, 23.7% of the total area containing bindweed contained rust teliospores as well as exhibited necrotic leaf death. Results of these studies suggest that further investigation of P. convolvuli as a biological control for hedge bindweed is warranted.

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